EOS

Sea ice encircles the Antarctic continent, variously melting and expanding according to the season and geographic location. A recent article in Reviews of Geophysics presented a synthesis of what we know about seasonal cycles of ice extent variability and the drivers in the context of longer term change. Here, some of the authors give an overview of what we know about the regional, seasonal, and interannual variability of Antarctic sea ice, and suggest where additional research is needed.

How has the overall extent of Antarctic sea ice changed over the past few decades?

For nearly 40 years, satellites have made a nearly complete and consistent record of daily sea ice concentration and extent.For nearly 40 years, satellites have made a nearly complete and consistent record of daily sea ice concentration and extent. Over this time, there has been a modest increase in Antarctic sea ice extent. This small increasing trend is made up of the sum of much larger opposing regional trends. The last few years of the record have stood out: there were record increases in total Antarctic sea ice extent from 2012 to 2014, followed by record lows through 2018.

How does sea ice extent vary through the year?

Sea ice extent is at a minimum in February when it fringes the Antarctic continent (at approximately 75 degrees south). It grows to a maximum in September when it is limited at approximately 55 degrees south by the Antarctic Circumpolar Current that separates cold, fresh polar waters from warmer subtropical waters. There is a consistent pattern in the seasonal cycle, characterized by a slow growth period and rapid melt period. This consistency is remarkable, considering the substantial regional, seasonal, and interannual variability of Antarctic sea ice observed over the 40-year satellite period.

Comparison of sea ice concentration in the Southern Ocean around Antarctica during the most recent winter maximum (September 2018, left) and summer minimum (February 2019, right). The gold line shows the median ice extent (the total area that is at least 15 percent ice-covered) over the period 1981 to 2010. Credit: Maps by Climate.gov, based on data from the National Snow and Ice Data Center

Are there geographic variations around the continent?

There are significant regional variations from the overall pattern. For example, sea ice advance in the western Antarctic Peninsula region is generally either shorter than or equivalent to the period of sea ice retreat. This is opposite to the pattern for Antarctica as a whole. Such regional variations have climatic, biological, and biogeochemical consequences at the local scale and warrant further investigation.

How long does it take each season for the sea ice to grow and melt?

Each year Antarctic sea ice takes seven months to grow and five months to melt.Each year Antarctic sea ice takes seven months to grow and five months to melt, with most melt occurring in just a couple of months. The maximum melt rate is approximately twice the maximum growth rate. This asymmetrical pattern is in stark contrast to the nearly symmetrical seasonal cycle seen in the Arctic.

Why is there a longer growth period than melt period?

Winds are thought to play a significant role in this. The tracks of individual storms make up a band of low pressure (trough) that circles Antarctica. This trough separates westerly winds to the north and easterly winds to the south. Twice a year, the trough deepens and contracts towards the continent.

At the start of the growing season, the sea ice edge is south of the trough and easterly winds work against the advancing ice edge to hamper its progress. As the ice advances and crosses the trough, its intensity weakens.

At the start of the melting season, the ice edge is north of the trough and westerly winds speed up its retreat until the ice edge again returns to the south of the trough. The warming ocean increases the rate of melting, but it is unclear whether this contributes to the asymmetry in the seasonal cycle.

How accurately do climate models capture the Antarctic seasonal cycle?

Antarctic sea ice extent simulated by the CMIP5 climate models. Credit: Eayrs et al. [2019], Figure 7On the whole, climate models do a reasonable job of capturing the seasonal cycle of Antarctic sea ice.

The mean of all models is very similar to the observed cycle of slow growth and rapid melt (see right).

Over 60 per cent of climate models grow ice for seven months, 20 per cent have longer growth seasons (eight months), and 20 per cent have equal growth and melt seasons.

However, none of the simulations has a melt season that is longer than the growth season. This implies that the mechanisms that drive the seasonal cycle are inherent in the climate models.

The models don’t always get the maximum and minimum extents correct, and there is a large spread across the individual models. The majority of the models melt too much ice during summer, so there is not enough ice during February. Many models do not grow enough ice, and so the winter maximum is less than two-thirds of the observed.

What are some of the unresolved questions where additional research, data or modeling is needed?

The role of the westerly winds to the north of the trough has not been quantified. Until we fully understand the mechanisms that drive the seasonal cycle, it is difficult to put the long-term variability into context.

Regional differences are likely to be of major importance for local ecosystems but the mechanisms driving the seasonal cycle at the regional scale have not yet been investigated.

Finally, changes in the sea ice cover only provide part of the story. Satellite technology does not yet adequately capture changes in the sea ice volume but this is an active area of research. An understanding of the changes in the total mass of the sea ice cover over time remains a significant gap in Southern Ocean observations.

We need a better understanding of how sea ice changes because it is a key climate indicator.We need a better understanding of how sea ice changes because it is a key climate indicator: its presence dramatically increases the amount of sunlight reflected by the surface, affects interactions between the atmosphere and the ocean, and is of major importance for ecosystems.

 

—Clare Eayrs (clare.eayrs@nyu.edu;  0000-0003-3129-7604), David Holland ( 0000-0002-5768-0866), Diana Francis ( 0000-0002-7587-0006) and Rajesh Kumar, Center for Global Sea Level Change, New York University Abu Dhabi, United Arab Emirates; Till Wagner ( 0000-0003-4572-1285), Department of Physics and Physical Oceanography, University of North Carolina, USA; and Xichen Li, Institute of Atmospheric Physics, China

Earthquakes send energy rippling through the planet, but so does something decidedly human caused: an underground nuclear explosion. With the goal of monitoring the proliferation of nuclear weapons, scientists and engineers have been tasked with differentiating between these two types of energetic events. By collecting geophysical data from controlled detonations in the Nevada desert, researchers aim to do just that.

“Sometimes an explosion can look very earthquake-like, and sometimes an earthquake can look very explosion-like.”Rob Abbott, a seismologist at Sandia National Laboratories in Albuquerque, N.M., sums up the motivation for the project, known as the Source Physics Experiment: “Sometimes an explosion can look very earthquake-like, and sometimes an earthquake can look very explosion-like.”

Going Boom in the Desert

The Source Physics Experiment, which began in 2010, has conducted 10 controlled underground explosions at the Nevada National Security Site, a Rhode Island–sized facility roughly 105 kilometers northwest of Las Vegas. The detonations mimicked underground nuclear explosions, but the researchers used chemical explosives such as nitromethane rather than fission- or fusion-based bombs.

“We obviously can’t and don’t want to set off a nuclear explosion,” said Abbott, who is the science lead at Sandia National Laboratories for the Source Physics Experiment.

The team set off different-sized explosions ranging from roughly 100 to 50,000 kilogram equivalents of 2,4,6-trinitrotoluene, an explosive commonly known as TNT. The largest bundle of explosives filled a canister roughly 12 meters long and 2 meters wide. “It’s huge,” said Abbott. “It comes on a flatbed truck.”

All of the explosions occurred in boreholes dug into either porous alluvial soil or granite. They were set off at depths ranging from 30 to 385 meters. That’s far shallower than most earthquakes, but drilling boreholes is very expensive, and the Source Physics Experiment used two, the larger of which was 2.4 meters in diameter.

Lawrence Livermore National Laboratory technician George Governo (right) and a coworker secure the upper skids on a high-explosive canister for the Source Physics Experiment-6 test. Credit: Gary Striker/LLNL Sensors, Sensors, Everywhere

Each explosion was carefully orchestrated. “Like anything, practice makes perfect,” said Abbott. “We do multiple dry runs.”

Abbott and his colleagues monitored the explosions from trailers located roughly 2 kilometers away after placing sensors like accelerometers into nearby instrument boreholes. In addition to the belowground sensors, instruments such as geophones and high-speed video cameras and surface mapping techniques (lidar, photogrammetry, and synthetic aperture radar) were used to measure how the detonations dynamically deformed, shocked, and otherwise affected their surroundings. The Source Physics Experiment team obtained measurements at a range of distances from the explosion: Some instruments were as close as 10 meters, and others were several hundred kilometers away.

Regional seismic networks run by such institutions as the University of Nevada, the University of Utah, and the California Institute of Technology detected the detonations as well. Metaphorically, no rock was left unturned, said Abbott. “The geologists came out on their hands and knees to look for microcracks.”

“It’s kind of like seismology of the atmosphere.”Danny Bowman, a geophysicist and atmospheric scientist at Sandia National Laboratories involved in the Source Physics Experiment, launched balloons containing pressure sensors above the explosion sites. Airborne experiments are important because most of the sound associated with an explosion goes straight up, said Bowman. “A ground-based sensor actually catches a small fraction of the energy.”

Bowman and his colleagues measured infrasound, low-frequency pressure fluctuations that can’t be heard by humans. By analyzing ripples in pressure and knowing the properties of the atmosphere, Bowman and his colleagues can reconstruct the physics of the explosion. “It’s kind of like seismology of the atmosphere,” said Bowman.

Hundreds of people at Sandia National Laboratories, Lawrence Livermore National Laboratory, Los Alamos National Lab, and other institutions have been involved in the Source Physics Experiment, which detonated its final explosion earlier this year. Data analysis is now ongoing, and it’ll take a while, said Abbott. “We’ve taken a ton of data.”

P’s and S’s

Comparing the Source Physics Experiment measurements with data from earthquakes will reveal the geophysical differences between nuclear explosions and seismic activity.

Scientists already have a few clues for telling these two types of events apart, said Abbott. Seismic activity tends to produce a higher fraction of shear (S) waves than explosions. That’s not surprising, Abbott said, because an explosion displaces material radially around it, producing compression (P) waves. But explosions also make S waves, and Source Physics Experiment researchers want to know why. “A major goal is to figure where those shear waves are coming from in a theoretically purely compressive, isotropic source,” said Abbott.

The Source Physics Experiment team is also studying how parameters such as burial depth and sediment type affect the signals recorded from an explosion.

Researchers around the world are looking forward to analyzing Source Physics Experiment data, which will be made freely available. Open science accelerates progress in research, said Timo Tiira, a seismologist at the University of Helsinki not involved in the research. “This experiment creates an important ground truth database.”

—Katherine Kornei (@katherinekornei), Freelance Science Journalist

Sailing through rocks is anything but quiet. Last month, vessels in the South Pacific clinked and clanked their way through pumice spewed out from an undersea volcano. These temporary islands of volcanic rock, shaped and propelled by ocean currents, wind, and waves, provide a literal toehold for marine life like barnacles, coral, macroalgae, and mollusks.

“We were in a large area surrounded as far as the eye could see.”In early August, an unnamed volcano near the Kingdom of Tonga erupted roughly 40 meters underwater. The eruption sent pieces of gray pumice—porous rock filled with gas bubbles—floating to the surface. This volcanic debris, some fragments as large as beach balls, then aggregated into pumice “rafts” spanning roughly 200 square kilometers.

Several sailing crews have encountered the rocks.

“We were in a large area surrounded as far as the eye could see,” said Rachel Mackie, the purser and chef of Olive, a private vessel that sailed into a raft on 9 August near Late Island. There was a strong smell of sulfur, said Mackie, and Olive took a beating. “When the larger rocks hit the steel hull, it reverberated.”



Pumice rafts aren’t that common, said Martin Jutzeler, a volcanologist at the University of Tasmania in Hobart. “We see about two per decade.”

Not all undersea eruptions produce them, but the rafts that do form tend to stick around. They can last for months or years until the pumice abrades itself into dust or finally sinks. And floating pumice can traverse long distances—when the same unnamed volcano near Tonga erupted in 2001, the pumice raft it created eventually arrived in Queensland, Australia, said Jutzeler.

Pumice can be “a perfect little substrate” for an array of marine biota, including mollusks, algae, and corals. Credit: Eleanor Velasquez

These transient, movable islands play an important role in marine ecosystems, scientists agree. Barnacles, coral, and macroalgae have all been found clinging to pumice, riding the waves en route to a new home.

“It’s a perfect little substrate,” said Jutzeler.

In 2012, Scott Bryan, a geologist at the Queensland University of Technology in Australia, and his colleagues showed that pumice rafts can significantly increase the dispersal of marine organisms. Bryan and his team found that more than 80 species traveled thousands of kilometers aboard pumice following the 2006 eruption of Home Reef Volcano in Tonga. “Pumice is an extremely effective rafting agent that can…connect isolated shallow marine and coastal ecosystems,” the researchers wrote in PLoS ONE.

Pumice rafts are definitely a way to get organisms to disperse widely.The long-distance journeys of pumice rafts are “definitely a way to get organisms to disperse widely,” said Erik Klemetti, a volcanologist at Denison University in Granville, Ohio, not involved in the research. But the idea that the stowaways aboard pumice rafts might replenish the Great Barrier Reef’s corals is wishful thinking, said Klemetti. “That’s probably an oversell.”

Jutzeler and his colleagues are planning to study pumice from last month’s eruption. They’ve been in touch with several vessels that passed through the rafts, and they’ve arranged to analyze some of the rocks. (But the samples they’ve been promised are currently stuck in transit in Fiji, said Jutzeler.)

By analyzing the chemistry of the pumice, Jutzeler and his colleagues hope to learn about the properties of the underwater volcanic eruption. For instance, was it eruptive or effusive?

Studying the rocks’ surfaces will also reveal how quickly they’re being abraded, which will shed light on how rapidly volcanic dust is being deposited into the ocean. That’s important because some plankton feed on this volcanic debris, which can result in phytoplankton blooms, said Jutzeler.

Jutzeler and other researchers are keeping a close watch on how the rafts are moving. Satellite imagery—from Terra, Aqua, Sentinel, and Landsat satellites, for instance—provides nearly daily updates. Ocean currents, wind, and waves sculpt and power the rafts, which now number in the hundreds.

They’ll likely arrive in Fiji in a few weeks, Jutzeler predicts.

—Katherine Kornei (@katherinekornei), Freelance Science Journalist

6 September 2019: This story has been updated to correct the distance a previous pumice raft traveled.

When scientists talk about the search for life in the cosmos, they often leave out a few key words: life as we know it on Earth. That usually means three things: liquid water, complex chemistry, and an energy source. It’s not a perfect definition of what’s required for life, but it’s as good a starting point as any.

But life as we know it on Earth can get pretty darn weird. Extremophiles can thrive in the most inhospitable places and make our planet seem less like a documentary and more like an episode of The X-Files—the X-philes, perhaps. We haven’t found any life beyond Earth yet, but here are five extreme environments on Earth in which life has managed to find a way and the distant worlds where we might look for their cosmic cousins.

A Martian Desert in Chile

The Atacama Desert’s rocky terrain, dried salt lake beds, and hyperarid climate make it challenging for life to gain a foothold. And yet the Atacama is home to insects, reptiles, occasional fields of flowering plants, and a few mammal species adapted to live in its extreme ecosystem.

The hyperarid Atacama Desert can bloom with flowers. Credit: Javier Rubilar, CC BY-SA 2.0

On the basis of its looks, the Atacama has often stood in for Mars in movies and TV shows, but portions of it are actually a good scientific analogue for Mars’s soil and climate, too. Oxalate minerals, found in both places, break down through biological processes and play a role in the carbon cycle of the Atacama. Scientists think the minerals could also do the same on Mars and serve as a potential biosignature for the dry limit of life.

Venusian Clouds in Earth’s Atmosphere Viewing Venus in ultraviolet light reveals dark streaks from an unknown UV absorber. Credit: ESA © 2007 MPS/DLR-PF/IDA

Life on Earth doesn’t live just on the surface and in the oceans. It also floats in the clouds. Microbes including bacteria, mold spores, pollen, and algae have all been detected in various regions of Earth’s atmosphere, lofted by storms and impacts and dispersed by the wind to other locations.

The same might be true of Venus’s lower atmosphere, where conditions are much more temperate than on its surface. “Among the plausible niches for extraterrestrial life in our solar system, the clouds of Venus are among the most accessible and among the least well explored,” planetary scientist David Grinspoon said at a forum in May 2018. A study last year explored the idea that sulfur-eating, acid-resistant, and UV-absorbing bacteria similar to those found on Earth could thrive in Venus’s atmosphere.

Otherworldly Ice Blades in the Andes

Sharp blades of ice carved by sunlight cling to the sides of Andean slopes. Scientists recently discovered that these penitentes are home to microbial life that survives the intense sunlight, dry air, and icy surface. “I think it’s the first discovery of microbes on penitentes,” microbial ecologist Steve Schmidt told Eos earlier this year. “Nobody ever thought to look for them.”

Penitentes, like these in the Atacama Desert, have been detected elsewhere in the solar system. Credit: European Southern Observatory, CC BY 4.0

Beyond Earth, penitentes have been detected on Pluto and are suspected to exist on Jupiter’s moon Europa. Studying these snow algae on Earth could give clues to how much aridity, ultraviolet radiation, and altitude life can withstand.

Titan’s Chemical Cocktail in Arctic Lakes

Titan is always near the top of the list of places to search for life beyond Earth because of its abundant surface liquid and exotic chemical composition ideal for chemotrophs to munch on. The discovery of vinyl cyanide in the moon’s atmosphere was particularly exciting for astrobiologists, as the molecules could theoretically combine with methane in Titan’s lakes to make the compounds that form cell walls.

Methane bubbles up from thawed permafrost in an Arctic lake. Credit: NASA, Katey Walter Anthony/University of Alaska Fairbanks

Methane lakes on Earth are hard to find but are becoming more common in the Arctic as permafrost thaws. For the past decade, scientists have been monitoring how Arctic lakes are responding to global warming. As the permafrost melts, it releases methane gas created by biological processes and trapped in ice. Although the Arctic lakes are still composed primarily of water—something frozen rock-solid on Titan—studying their ecosystems as they become more methane rich can give insight into not only our own planet’s future but also the potential for life on Titan.

Irradiated Mold on the ISS Mold grows on an interior panel of the International Space Station. Credit: NASA

As far back as the Soviet space station Mir in the 1980s, scientists have known that mold is a big problem for spacecraft. Recent research has shown that some mold spores that have been found on the International Space Station (ISS) can survive X-ray exposure 200 times the dose that would kill a human. “We now know that [fungal spores] resist radiation much more than we thought they would,” microbiologist Marta Cortesão said about her team’s discovery.

This resilience might be relevant for planets orbiting stars smaller than the Sun. Many red dwarf stars have strong flares that expose nearby planets to punishing doses of X-rays and ultraviolet light. But the ISS molds hint that such stars might not be so poisonous after all—at least not to mold.

As we explore the limits of life as we know it on Earth, we begin to understand that the potential for life beyond our X-philes planet is much bigger than we had imagined—the truth is, in fact, out there.

—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer

Scientists have long known that lightning from thunderstorms can cause perturbations in the lower ionosphere, partially ionizing the layer and creating disturbances in radio frequency communications. These disturbances usually occur over timescales of less than 15 seconds. However, scientists have also noted ionospheric perturbations occurring over timescales of several minutes, coincident with thunderstorms. Because of the longevity of these signals, it’s unlikely they are caused by single lightning strikes; rather, they appear to result from the electrical activity of a thunderstorm as a whole.

Koh et al. provide the first analysis of this type of long-term, lower atmosphere–ionosphere energy coupling and propose that heating observed in the ionosphere results from charges in thunderclouds redistributing as updraft strength increases.

All thunderstorms are built on the upward convection of warm, moist air. This process helps create the separation of electrical charges in storms that can lead to lightning, but even when the spectacular fast discharges do not occur, convective forces still create strong electrical polarization in storm clouds. The new study shows that this type of convection-based charging can also cause heating in the lower ionosphere as the ions there are energized by the electrical activity in the storm below.

The researchers studied long-wavelength radio wave transmissions from four locations in the United Kingdom and Germany to a single receiver in Bath, United Kingdom, on 27 August 2016 at around noon local time. These radio signals are sensitive to charges in the atmosphere, including the lower ionosphere, and the team used them—along with independent electric field measurements from an antenna array in Portishead, United Kingdom—to monitor a strong convective system over south central England. The researchers observed disturbances in the lower ionosphere occurring on timescales too long to be associated with lightning strikes. The disturbances grew for approximately 1 minute, and then ionospheric conductivity took at least another 200 seconds to return to normal levels.

The researchers note several other mechanisms by which such ionospheric disturbances might occur, such as gravity waves or solar flares, but conclude that the updraft-related mechanism is the most likely. The results, they say, demonstrate a new type of energy coupling between thunderstorms and the ionosphere and offer a more complete picture of atmospheric geophysics. (Journal of Geophysical Research: Space Physics, https://doi.org/10.1029/2019JA026863, 2019)

—David Shultz, Freelance Writer

Accurately representing clouds and convection in weather and climate models is one of the thornier challenges facing climate modelers. Cloud droplets form on micrometer scales, whereas convective updrafts and downdrafts, which play vital roles in cloud formation, can extend over distances of up to 10 kilometers.

Current global climate models operate with resolutions of 10–100 kilometers and thus cannot resolve these processes directly. Instead, cloud processes are represented with numeric approximations known as parameterizations. For example, climate models depict the transport of heat and moisture in a cloud using values that describe the rate and direction of movement of heat and moisture in the atmosphere. However, these approximations gloss over the dynamic, small-scale processes that drive cloud formation in reality, so the resulting representations of clouds in these parameterizations contain significant uncertainty.

This uncertainty with respect to clouds is the main source of uncertainty in model-based projections of future global warming; more clouds in a future climate will dampen global warming while fewer clouds will amplify the warming. Furthermore, uncertainty in cloud representations also contributes to systematic errors in simulated precipitation patterns.

In a recent study, Jansson et al. demonstrate a new approach to modeling clouds. The authors used a method known as superparameterization in which individual parameterizations are replaced by a smaller-scale and more accurate simulation of cloud processes in a global circulation model. Superparamaterizations have been applied before in global climate models, but new in this study is the use of three-dimensional, high-resolution large eddy simulations as the cloud-resolving model. The new technique also allows users to restrict the superparameterization to a given geographic area to control computational costs.

The authors implemented their procedure using the Dutch Atmospheric Large Eddy Simulation and the Open Integrated Forecast System (OpenIFS) and demonstrated the superparameterized setup by simulating conditions on an April day in 2012 over part of the Netherlands.

The model more accurately reproduced cloud top height measurements observed by the Moderate Resolution Imaging Spectroradiometer aboard the Terra satellite compared with the standard parameterized version of OpenIFS. The superparameterized model also showed improvements in representing specific humidity.

The results of the study indicate that superparameterization using large eddy simulations could improve the representation of clouds in global circulation models. Furthermore, the work provides a foundation for developing future parameterization approaches and the use of different local models.

However, the authors note that future work is needed to validate the approach fully and that there is room for improvement. For instance, the geographic area over which the superparameterized model can be applied is limited by computational restraints, and the model did not capture cloud structure well. Nevertheless, the demonstration cleared a significant technical hurdle and shows promise for future climate modeling efforts. (Journal of Advances in Modeling Earth Systems (JAMES), https://doi.org/10.1029/2018MS001600, 2019)

—Aaron Sidder, Freelance Writer

Sunlight is one of the main drivers of polar landscapes, which rely on the Sun’s rays for warmth and energy.

These results reveal interactions among the atmosphere, sea ice, and ocean.Researchers now have quantified how sunlight permeates Arctic sea ice and reaches marine ecosystems. They found distinct seasonal patterns in light transmission, with the presence of ice, snow, and melt ponds dictating how much light makes it into the ocean. These results reveal interactions among the atmosphere, sea ice, and ocean, data that are important for climate modeling, the team suggests.

The Ice Decides

Stefanie Arndt, a sea ice physicist at the Alfred Wegener Institute in Bremerhaven, Germany, and her colleagues used measurements obtained with the R/V Polarstern, a research icebreaker operating out of Bremerhaven. Over the course of six expeditions between 2011 and 2017, researchers sent remotely operated vehicles (ROVs) under Arctic sea ice in 45 different locations. The sites were more or less randomly selected, said Arndt. “The route [of R/V Polarstern] is dependent on the ice conditions.”

Instruments on the ROVs measured light levels between wavelengths of 320 and 950 nanometers. By comparing measurements obtained from under the sea ice and measurements taken on top of the sea ice, Arndt and her collaborators calculated light transmission as a function of wavelength. In total, they analyzed more than 35,000 spectra obtained between May (spring) and September (autumn) through ice ranging from a few centimeters thick to more than 3 meters thick.

Snow, Ice, and Melt Ponds

The Arctic landscape follows distinct seasonal patterns, said Arndt. It snows in the winter, but the snow melts in the springtime. As temperatures continue to increase, the exposed sea ice begins to melt as well. Melt ponds form and enlarge, and they can extend all the way through the ice into the underlying water. In the autumn, snow accumulates, and the process begins again.

The scientists found the lowest transmission levels in May—less than 1% at all wavelengths. That’s not surprising because snow still blankets much of the ice at that time of the year, said Arndt. “Snow is really opaque.”

But as the snow disappeared, some of the surface ice melted, ponds of meltwater started to accumulate, and more light was transmitted. In August, more than 10% of the incident sunlight was transmitted to the ocean below, Arndt and her colleagues found. That sunlight transports heat and energy, said Arndt. For instance, it warms the water and powers the metabolism of algae.

One explanation for the increased transmittance is meltwater ponds that melt all the way through the ice. These conduits, which can measure up to a few hundred meters across, link the atmosphere and the ocean and are important for transmitting light, the scientists suggest. “They’re a window from the atmosphere to the upper ocean,” said Arndt.

These results reveal how the atmosphere, sea ice, and ocean are entwined, said Arndt. “That’s poorly understood in climate models.”

Thriving Brown Algae

Arndt and her colleagues also found evidence that sunlight was being used by marine life in the Arctic. The researchers measured a spectral shift in data collected in July: There was lower transmittance at wavelengths beyond 500 nanometers. That’s likely due to brown algae that thrive on the underside of sea ice, the team concluded. These algae grow by absorbing light.

“The novelty and significance of this work lie in the extensive data set it presents.”“Decreased early summer light transmission through sea ice moderated by sea ice algae might be a widespread feature in the Arctic,” the researchers wrote in the Journal of Geophysical Research: Oceans in July.

“Light transmission through sea ice is central in both sea ice energy balance and ecosystem studies,” said Hanna Kauko, a biological oceanographer at the Norwegian Polar Institute in Tromsø not involved in the research. “The novelty and significance of this work lie in the extensive data set it presents.”

Arndt and her colleagues are looking forward to collecting data on a special R/V Polarstern cruise that begins this month (September). During the expedition, called Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), the icebreaker will purposefully anchor itself to an ice floe and drift around the Artic for a year.

The project will shed new light on how the Arctic is responding to climate change and the links among the atmosphere, sea ice, and liquid water. Arndt plans to be aboard R/V Polarstern for at least one of MOSAiC’s legs. She’ll arrive via helicopter or plane if a runway can be cleared, she said. “That’ll be a real expedition.”

—Katherine Kornei (@katherinekornei), Freelance Science Journalist

When was it, exactly, that plate tectonics started on Earth?

Geodynamicist Fabio Crameri recalled a 2016 conference in which attendees argued over this question. Some thought that plate tectonics started shortly after the planet formed over 4 billion years ago, whereas others thought that tectonics did not truly begin until about 800 million years ago.

In 2018, Crameri was at a different tectonics conference and heard the same argument spark over the same question. It was a rift in opinion, and who was right and who was wrong depended on how you defined plate tectonics, explained Crameri, who works at the University of Oslo in Norway.

“It became obvious to me that semantics was the main problem when discussing when plate tectonics began on Earth,” Crameri said.

In response, Crameri assembled a team of researchers to analyze the issue, and they recently published a paper in Tectonophysics. In it, the scientists outline a concept for what they think plate tectonics has come to mean in the decades since the idea assembled, and they call this concept “ocean plate tectonics.” Crameri and his team’s aim is that the term will bring an end to the semantic impasses that keep upwelling in the discipline.

New Views

Traditionally, plate tectonics describes the motion of continental and oceanic plates as they move across the planet’s surface. But that definition does not include much about the engine (Earth’s convection system) that drives the motion.

“It comes from nowhere,” said Louis Moresi, a computational geophysicist at Australian National University in Canberra. “There’s a huge step between understanding what those simple behaviors are and how they work.”

Right now, researchers talk about plate tectonics the way a car enthusiast might talk about their car—the way it handles—without ever talking about the engine or the car’s design.

“We can no longer look at plates as separate from mantle convection.” Part of the reason is that computers were not able to simulate the engine that drives tectonics until the past few decades. That engine is mantle convection, which revs when hot mantle material rises and creates new oceanic crust at mid-ocean ridges. Such a system, because of its planetary scale, is computationally hard to simulate, according to Anne Davaille, a geodynamicist with the French National Centre for Scientific Research. Davaille, who was not involved in the ocean plate tectonics work, thinks that geoscientists who study things like fluid dynamics think about mantle convection and tectonic plates as one and the same and those who study tectonics in terms of what happens on the planet’s surface tend to separate the two.

At the conference in Switzerland that Crameri attended, Davaille gave a presentation about the death of tectonic plates at subduction zones, where plates plunge into the mantle at the end of their long journey after being born at mid-ocean ridges. Subduction, she argued, seems to happen if there is a plume of hot mantle material beneath the plate—something that may have been essential for plate tectonics to get going early on in Earth’s history. In her eyes, subduction zones are where ocean plates and the mantle start to become indistinguishable.

“We can no longer look at plates as separate from mantle convection,” said geodynamicist Carolina Lithgow-Bertelloni, one of the authors behind the new paper.

In the theory of ocean plate tectonics, oceanic plates are part of one whole convective regime. Credit: Fabio Crameri

In addition to sites of plate tectonics and mantle convection, researchers also examined the source of the upwelling magma that drives seafloor spreading in the first place.

Traditionally, some researchers thought new oceanic crust was fed by plumes of magma that rise from the boundary between Earth’s lower mantle and core. But, according to Crameri and his team, this is not the whole story.

“This misconception is mainly due to the many cartoons or sketches that put the deep upwelling flow always right underneath the spreading ridge,” Crameri said.

Those cartoons and sketches create the impression that ocean plates are more distinct from the mantle than they really are, he added. Rather, the smaller-scale updraft made by spreading ridges pulls mantle magma into place, and this magma need not come only from a deep plume—it can come from anywhere in the mantle.

“Our planet, it’s cooling down, and the convection of the mantle is what’s producing the motion of the plate,” said Claudio Faccenna, a structural geologist and geodynamicist at the University of Texas at Austin and Roma Tre University in Rome who was not involved in the work. “What they’re doing is to try to frame the original evolution of the oceanic lithosphere in a fully consistent way.”

Back to the Start

Ocean plate tectonics is not exactly a new concept, explained Laurent Jolivet, a tectonicist at Sorbonne University in Paris who was not involved in the review work. “This so-called new concept is just what we’ve been talking about for 10 years or so,” he said.

“It’s not a eureka moment. It’s a hard-work-over-two-decades moment. Only on geologic time does this look like a eureka moment.”Moresi, who was also not involved with the work, agrees. “It’s not a eureka moment. It’s a hard-work-over-two-decades moment. Only on geologic time does this look like a eureka moment,” he said.

Nevertheless, ocean plate tectonics stands to rescript the way geologists speak to one another about the history of plate tectonics on Earth.

If plate tectonics describes just the motion of plates on Earth’s surface relative to one another, for example, the process began shortly after Earth’s formation billions of years ago, “right after the magma ocean or so,” Crameri said.

But if plate tectonics is defined in terms of ocean plate tectonics, that means the process started much later, around 800 million years ago. The reason is that it took Earth millions of years to cool off enough for plates to remain solid for long periods of time.

Older ideas surrounding plate tectonics, once so new, subduct and destruct, making way for something new back at the ridge.

—Lucas Joel, Freelance Journalist

Scientists mimicked the neural networks of the brain to map phytoplankton types in the Mediterranean Sea. A new study published in the Journal of Geophysical Research: Oceans presented a new method of classifying phytoplankton that relies on artificial intelligence clustering.

Phytoplankton blanket surface waters of the world’s oceans, and pigments in their cells absorb certain wavelengths of light, like the chlorophyll that gives plants their green color. Viewed from space, the color of the ocean’s surface changes depending on the phytoplankton growing there. In the Mediterranean Sea, where the latest study focused its efforts, an array of phytoplankton species bloom throughout the year.

Past research has mined satellite images of ocean color in the Mediterranean for common pigments found in phytoplankton. A combination of pigments can reveal a certain type of dominant phytoplankton in the area, like certain species of diatoms that can be spotted because of their unique orange pigment, fucoxanthin. But connecting the complex relationships between satellite image pixels, pigments, and phytoplankton types can make for a tricky analysis.

The latest study turns to artificial intelligence to parse through the multidimensional data. The process mimics the brain’s ability to take in new information and learn over time, giving the algorithm a chance to identify relationships in the data that may not be readily apparent. The algorithms cluster similar nodes of information near one another, creating a two-dimensional diagram called a “self-organized map.” The scientists trained two algorithms used in the study with 3 million pixels from satellite images and over a thousand measurements taken by boat in the Mediterranean.

The results show six types of phytoplankton and how they come and go by season. In winter, haptophytes and chlorophytes (both algae) are common in the western Mediterranean. In the summer months, the most abundant photosynthetic organism on Earth, the cyanobacteria Prochlorococcus, rules broad swaths of the sea. The new method revealed how the blooms changed over time, giving the scientists a way to ask questions about marine food chains and possible effects of climate change in the future.

The scientists called the new method “very general” in their paper and said that it could be applied elsewhere in the world’s oceans.

—Jenessa Duncombe (@jrdscience), News Writing and Production Fellow

Ten Democratic hopefuls spoke about climate change and their plans to curtail it at CNN’s Climate Crisis Town Hall on 4 September. The candidates, who answered questions from moderators and audience members for 40 minutes each, addressed concerns, including rising sea levels, regulations on fossil fuel companies, green energy solutions, and the impacts of climate change on people of the world. The event stood in place of a formal debate, as the Democratic National Committee has refused to endorse debates on single-issue topics.

“This feels like something I’ve been waiting for all my career—a substantive discussion of policy where most of the candidates offer new ideas and clearly understand the urgency of the situation.”The candidates all voiced support for rejoining the Paris climate accord, which New Jersey senator Cory Booker said is “the cost of entry” to be on the Democratic ticket.

Although many of the candidates emphasized their support for scientific and research development, with former vice president Joe Biden commenting that “we have to start choosing science over fantasy,” they differed on how they plan to address curbing carbon emissions and mitigating the consequences of climate change.

Kate Marvel, a climate scientist at NASA Goddard Institute for Space Studies, told Eos that she was “impressed with the caliber of questions and the thoughtfulness of many candidates’ responses” at the town hall.

“This feels like something I’ve been waiting for all my career—a substantive discussion of policy where most of the candidates offer new ideas and clearly understand the urgency of the situation,” Marvel noted.

The Struggle Between Urgency and Realism

The candidates spoke about becoming carbon neutral, first in energy generation and then overall, by no later than 2050. South Bend, Ind., mayor Pete Buttigieg said that we must end our dependence on coal “as quickly as humanly possible,” and Massachusetts senator Elizabeth Warren and Vermont senator Bernie Sanders said that most currently proposed timelines were not aggressive enough.

Biden, Minnesota senator Amy Klobuchar, and businessman Andrew Yang put forth that such carbon-free timelines are not realistic given the current science or political structure, a position that elicited frustration from some scientists. Andrea Simonelli, a political science professor at Virginia Commonwealth University in Richmond, called those responses “tone deaf.”

“Biden suggested that the timelines he is using in his plans are because science didn’t have a faster way to transition [or that] there wasn’t the technology yet,” Simonelli explained. “It’s not that we don’t have the tech. We’ve been missing the political will to move on it.”

“Suggesting that we should take more time when the evidence shows we need to move faster minimizes the great risk to all of us as well as the power of American ingenuity,” she added.

Personal Versus Corporate Responsibility

The candidates faced repeated questions on the personal sacrifices that Americans could face in their future plans to address climate change. Former housing and urban development secretary Julián Castro commented that people must strive to take public transit, and California senator Kamala Harris voiced support for plastic straw bans.

Several candidates emphasized that tackling climate change is not entirely dependent on individual actions and instead requires holding corporations responsible.

Warren, for instance, rebuffed a question about consumer choice of light bulbs, saying “I get that people are trying to find the part that they work on” but added “this is exactly what the fossil fuel industry wants us to talk about.”

 

Sen. Elizabeth Warren says conversations around regulating lightbulbs, banning plastic straws and cutting down on red meat are what the fossil fuel industry wants people focused on as a way to distract from their impact on climate change. #ClimateTownHall https://t.co/N3vZCD2jHC pic.twitter.com/eVQhFxgKet

— CNN (@CNN) September 5, 2019

 

Arvind Ravikumar, an energy engineer at Harrisburg University of Science and Technology in Pennsylvania, praised her response. “I think Sen. Warren best understands and articulates the need for systemic and institutional change in addressing the climate crisis, and even pointing out the fallacy of focusing on individual actions,” he told Eos.

Buttigieg echoed Warren’s concerns. “No individual can solve this through personal action,” he said. To a question about changing meat consumption in the United States, he responded, “Of course we need balance in all our consumption patterns,” and said that questioners should stop repeating Republican talking points.

Leah Stokes, an assistant professor in the Department of Political Science at the University of California, Santa Barbara, said that despite CNN’s repeated questions on individual responsibility, “overall, I think the candidates did a good job of pushing back against that framing.”

Resilience Versus Retreat

When it came to the question of whether residents should move away from areas vulnerable to natural disasters or build up resilience to them—flight or fight—candidates were split. Those in the fight camp, like Booker, argued that regardless of sea level rise communities will face natural hazards that they must prepare for. “We don’t want to wait until there’s a natural disaster to actually make our communities more sustainable,” Castro mentioned earlier in the evening.

Castro also endorsed the idea of protecting more people with subsidized flood insurance, an approach that Naomi Oreskes, a professor of the history of science at Harvard University, called “a mistake.”

“This should open a discussion about the future of disaster insurance, immigration policy, and disaster preparedness.”“I would rather he had suggested paying for necessary relocation out of his carbon pollution fee,” Oreskes commented during the town hall.

Other candidates also saw this stance as a temporary solution at best. It is “pretty stupid” to keep paying people to rebuild where things keep getting destroyed, according to Sanders. Both he and Warren supported the idea that people living in affected areas should be offered monetary support to relocate to safer areas. Temporary protected status and a special asylum status must be offered to international climate refugees around the world, said former Texas representative Beto O’Rourke.

Simonelli argues that any solution needs to incorporate both fight and flight options. “There is a need to rebuild our communities to stronger flood [and] hurricane wind standards as well as moving them inland,” which will be a “huge undertaking,” she said. “This should open a discussion about the future of disaster insurance, immigration policy, and disaster preparedness.”

“Win for Climate and the American People”

That climate change is a crisis that affects people around the world was common ground among the presidential hopefuls. “We are fighting for the survival of the Planet Earth,” Sanders said.

Scientists watching the debate voiced support for the town hall as a way to convey that message to voters.

“At the end of the day, this is a win for climate and the American people. We are finally at a stage where we can discuss and debate serious policy questions on ways to address climate change and not get stuck with inane questions like ‘Do you believe in climate change?’ that have long dominated this topic,” Ravikumar noted.

“As a researcher in this field, I wasn’t prepared to be ‘wowed’ by anyone, but what is important is that they are discussing climate change in some detail and candidates are taking this issue seriously,” said Simonelli.

Stokes called the event “unprecedented coverage of the climate crisis on mainstream national cable news.”

“I think we’ll have knockoff effects that we will be benefiting from for years to come,” she added.

Candidates will have a second chance to speak to a live audience about their climate change plans on 19–20 September at Georgetown’s Climate Forum cohosted with MSNBC.

—Jenessa Duncombe (@jrdscience), News Writing and Production Fellow; and Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer

Nitrogen, along with carbon, hydrogen, and oxygen, is one of the fundamental elements that make life on Earth possible. Nitrogen makes up nearly 80% of the air we breathe and is a key factor in food security, human and environmental health, climate change, and the economy. The problem with nitrogen today—at least with agricultural nitrogen in the form of fertilizers—is like many others: There is a geopolitical divide between haves and have-nots. And, according to the researchers behind a new study, large-scale efforts are needed to address the environmental, economic, and social problems that surround the use, and misuse, of nitrogen around the world.

Agricultural nitrogen that doesn’t enter crops contaminates the land, water, and air in many parts of the world, particularly in developed countries with ample access to fertilizers. Unused amounts represent wasted nutrients that do not contribute to farmers’ yields and contribute to numerous health problems, as well as to ozone depletion, climate change, aquatic dead zones, water pollution, and other environmental problems.

In developing economies, though, farmers don’t have enough nitrogen. Without fertilizer, exhausted soils cannot support the crops that local populations need, and food insecurity contributes to social unrest, economic stagnation, malnutrition, and famine.

In a new paper, Houlton et al. consider the problems of the global nitrogen imbalance as well as proposed solutions and present a five-pronged approach to maximize the positive effects of agricultural nitrogen on our planet.

First, we should build on the recent momentum of nitrogen efficiency gains in the United States, Europe, and China. With improved technology and farming practices, fertilizers can precisely meet the needs of growing plants. These efforts should extend to nitrogen in animal feed and waste as well. Incentive programs and more nitrogen-efficient crops can help farmers adopt better practices.

Second, nitrogen supplies should be distributed differently. Food-insecure areas, such as parts of sub-Saharan Africa and South America, would benefit from increased access to nitrogen fertilizers. These changes would require the cooperation of both national governments and private organizations and must account for farmers’ local needs and customs.

Third, nitrogen pollution should be removed from the environment by both reducing nitrogen pollution at its sources and restoring wetlands and floodplains. These restored ecosystems can sponge excess nitrogen out of water, and they provide habitat that may increase biodiversity. In addition, wetland soils can further mitigate climate change by storing carbon.

Fourth, we should waste less food. A quarter of all food produced is never consumed, so the fertilizer used to grow this food is wasted. Better on-farm storage facilities and public awareness both can help, as food waste occurs both on farms and at the consumer level.

Finally, we need a cultural shift to adopt diets with low nitrogen footprints. Farmers can breed and grow more nitrogen-efficient crop varieties, whereas consumers can opt to consume food with lower nitrogen footprints.

The researchers call on other scientists to model and explore the costs and benefits of these solutions. For example, quantitative modeling of how different practices might affect future climate change could spur governments to enact incentive programs. And research into which foods use nitrogen most efficiently would help consumers make more informed choices. (Earth’s Future, https://doi.org/10.1029/2019EF001222, 2019)

—Elizabeth Thompson, Freelance Writer

Peering back in time over 4 billion years is hard, but asteroids lend a hand: These space rocks contain primordial material left over from the formation of the solar system.

Scientists have now analyzed high-resolution images of the surface of Ryugu, a near-Earth asteroid recently visited by the Hayabusa2 spacecraft. They found a surprising lack of dust, rocks compositionally similar to rare meteorites, and a landscape consistent with the space rock forming from a cataclysmic collision. These results shed light on how asteroids are assembled, information that’s valuable for planning asteroid deflection missions on Earth, the research team suggests. These results were reported last month in Science.

“This is the first time scientists are able to study boulders up close on a dark asteroid.”It’s critical to learn more about the composition, surface, and interior of asteroids in the event that one of these objects is incoming toward Earth, said Lucille Le Corre, an astronomer at the Planetary Science Institute in Tucson, Ariz., not involved in the research. “This is the first time scientists are able to study boulders up close on a dark asteroid.”

Exploring a Dark World

In June 2018, the Japan Aerospace Exploration Agency’s Hayabusa2 arrived at Ryugu after a 3.5-year journey. The refrigerator-sized spacecraft paced the roughly 900-meter asteroid, both objects orbiting the Sun at tens of kilometers per second. In October of the same year, Hayabusa2 released a lander—the Mobile Asteroid Surface Scout (MASCOT)—toward Ryugu’s surface from an altitude of 41 meters. Thanks to Ryugu’s extremely weak gravitational acceleration (about 1/80,000 that of Earth), MASCOT fell for roughly 6 minutes before tumbling to a stop. Over the next 17 hours, until its batteries ran out, the lander snapped more than 90 images with its visual and near-infrared camera. (Light-emitting diodes provided illumination during Ryugu’s roughly 4-hour night.)

These images, which record features as small as 0.1 millimeter, confirm that Ryugu is a dark world. It reflects only about 5% of the light that shines on its surface. “You can compare it to very dark coal,” said Ralf Jaumann, a planetary scientist at the German Aerospace Center in Berlin and lead author of the new study.

MASCOT’s close-up images also revealed a mystery. They showed that Ryugu’s surface is free of dust, a big surprise given that asteroids are constantly bombarded by interplanetary dust particles. These tiny impacts, which pulverize and destroy the upper structure of rocks, produce debris.

“There should be dust,” said Jaumann.

He and his collaborators hypothesize that dust may sink into holes on Ryugu’s porous surface, effectively remaining hidden from view. Another idea is that the charged particles that constantly circulate through the solar system—the solar wind—create a magnetic field on Ryugu’s surface that causes dust to levitate. The dust then escapes from the asteroid because of the space rock’s weak gravity, the team suggests.

“Ryugu is some product of a violent process.”MASCOT’s instruments also showed that the rocks that litter Ryugu’s surface—ranging in size from a few tens of centimeters to a few tens of meters—tend to fall into one of two categories. They’re either dark and rough or relatively bright and smooth, Jaumann and his colleagues found. “They have a different structure,” said Jaumann.

This finding implies that Ryugu may have formed from the collision of two different types of asteroids, the research team suggests. Or Ryugu’s inner and outer regions may have been originally composed of different types of material that got jumbled up after a cataclysmic impact by another body.

“Ryugu is some product of a violent process,” said Jaumann. It’s a rubble pile held together by weak gravity, so it’s important “not to destroy this pile of debris,” said Jaumann.

Ryugu’s rocks also contain inclusions, most of them smaller than 1 millimeter. On the basis of how these inclusions reflect light, some of them may contain olivine, a greenish mineral found in Earth’s crust and certain rare meteorites. Ryugu—or bodies like it—may therefore be the source of some of Earth’s meteorites.

In late 2020, scientists will get an even closer look at Ryugu. That’s when samples that Hayabusa scooped up from the asteroid’s surface will parachute down in the Australian outback. “Future laboratory studies of the samples from Ryugu will give us some clues about our solar system’s early history and formation,” said Le Corre.

—Katherine Kornei (@katherinekornei), Freelance Science Journalist

Dorian, Hurricanes, and Flood Risks. Following the news about Dorian sent me to Eos’s own archives to read more about hurricanes and flood risk. Here are a few articles that caught my attention: A Diary of a Storm is an engaging essay by a former editor about her experience of Harvey in Houston. The authors of the opinion article Millions More Americans Face Flood Risks Than Previously Thought explain how “top-down” flood modeling over vast areas can help provide more comprehensive floodplain mapping and better risk assessments. And in Sharing Data Helps Puerto Ricans Rebound After Hurricane Maria, scientists describe their project focused on drinking water and Hurricane Maria data. They believe that “the scientific community can do more to reduce the cost and human impact of destructive hurricanes.” —Faith Ishii, Production Manager

 

Copernicus Sentinel-6A Ready for Testing. I’m eagerly awaiting next year’s launch of the two newest Copernicus Sentinel satellites from the European Space Agency. Sentinel-6A and its twin Sentinel-6B will be dedicated to monitoring changes in global sea level. —Kimberly Cartier, Staff Writer

 

Bizarre Fossils Reveal Asia’s Oldest Known Forest. How cool is it to envision this newly discovered ancient forest of small trees growing along a Devonian-age coast where this piece of land in Xinhang, Anhui, China, was located at least 360,000,000 years ago? Time travel to the past is one of the great joys of geology! —Liz Castenson, Editorial and Production Coordinator

 

Rising Global Temperatures Influence California’s Fire Season.

Credit: NASA

Researchers divided California into four regions (North Coast, Sierra Nevada, Central Coast, and Southern Coast) and examined fire activity during different seasons. The Earth Observatory article has graphs for all four regions, and the one above shows the seasonal and annual burned area in the whole state between 1972 and 2018. Overall, the annual burned area increased by 405% during that period. —Melissa Tribur, Production Specialist

 

Elizabeth Warren Unveils Climate Change Plan, Embracing Jay Inslee’s Goals. In advance of the CNN climate debate, a number of Democratic presidential hopefuls released details of how they would deal with climate change. This New York Times story does a good job of examining Sen. Elizabeth Warren’s plan, including pointing out that Warren has picked up on some of the ideas advocated by Washington State governor Jay Inslee, who has dropped out of the race. —Randy Showstack, Staff Writer

 

Terrawatch: Warnings Fail to Prevent U.K. Fracking Quakes. After M2.1 and M2.9 fracking-related earthquakes shook the English city of Blackpool in August, seismologists are investigating why the industry’s traffic-light system failed. They’re looking into U.K. shale formations and how they may be different than commonly understood shale. —Heather Goss, Editor in Chief

 

Great Pacific Garbage Patch Swim Nears Conclusion.

Long-distance swimmer Ben Lecomte encountered a lot of plastic during his Vortex Swim in the Pacific Ocean. Credit: icebreaker

I doubt that swimming through a “soup” of plastic in the middle of the ocean is high on many bucket lists. But long-distance swimmer Ben Lecomte took one for the team and did just that, swimming 335 nautical miles through the Great Pacific Garbage Patch to raise awareness of plastic pollution. Read this great interview with Lecomte to learn about his motivations and what he saw along the way. —Timothy Oleson, Science Editor

When we put a plastic bag in the trash, it’s out of sight, out of mind. But where does it end up? Ben Lecomte, a long-distance swimmer, ventured into one burial ground for the world’s plastics: the North Pacific garbage patches. His recount of swimming through the swirl of bottles and milky soup of microplastics is a reminder that our plastics from land have a long life at sea. —Jenessa Duncombe, Staff Writer

The year 1969 was monumental. It is remembered in popular culture for the Moon landing, the Stonewall riots, and Woodstock. But it also marked an important breakthrough for diversity within the scientific community. Fifty years ago, four women made history as the first all-female team to conduct research in Antarctica and to venture to the South Pole. In doing so, these brave pioneers set an example for women in polar science and beyond for years to come.

Prior to the 1969 expedition, women, especially women in scientific roles, were virtually nonexistent in Antarctica. The first women to visit arrived there in part as a by-product of marriage. These women included Caroline Mikkelsen, the first woman to reach Antarctica, who accompanied her husband on his 1935 expedition, and Edith Ronne and Jennie Darlington, who also accompanied their husbands on their polar exploration in 1947. Other early female visitors included marine geologist Maria Klenova in 1956, the first woman scientist to visit Antarctica, and Christine Muller-Schwarze, who visited in early 1969 to study penguins. While Muller-Schwarze was in Antarctica, another milestone expedition was being planned.

Rising Stars in Polar Research

At the team’s forefront was Dr. Lois Jones, a geochemist at Ohio State whose research focused on studying strontium isotopes to determine the origin of salts in Antarctic lakes and soils and better understand the geologic history of the continental basin.In mid-1969, Colin Bull, director of the Institute of Polar Studies (now the Byrd Polar and Climate Research Center) at Ohio State University in Columbus, was pulling together a team of strong women scientists for an Antarctic expedition. At its forefront was Dr. Lois Jones, a geochemist at Ohio State whose research focused on studying strontium isotopes to determine the origin of salts in Antarctic lakes and soils and better understand the geologic history of the continental basin [Lewandowski, 2018].

Until 1969, Jones had relied on samples collected and brought home by other scientists because of the strict gender ban imposed by the U.S. Navy, which oversaw U.S. research expeditions in Antarctica at the time and prevented women from visiting the continent for fieldwork [Lewandowski, 2018]. But she was interested in expanding her research to a new location, Antarctica’s Dry Valleys, which meant conducting her own fieldwork and collecting her own samples. With Bull’s support, she submitted a research proposal to the National Science Foundation (NSF). NSF approved the proposal, and the Navy reluctantly allowed the all-woman research team to visit Antarctica [Rejcek, 2009].

The rest of the Ohio State team fell into place with Jones at the helm. It included Eileen McSaveney, a geology graduate student; Kay Lindsay, an entomologist who had an interest in the mites and springtails of Antarctica and whose husband had previous experience with Antarctic research; and Terry Tickhill Terrell, a chemistry undergraduate who lacked a background in geology but was skilled with machinery and who, in Jones’s estimation, was gritty enough for arduous Antarctic work. Although the research team received overwhelming support from the public and the scientific community, there was also skepticism.

Rather than focusing on the research that the team was pursuing, for example, some reporters asked superficial questions of the researchers, such as “Will you wear lipstick while you work?” [Rejcek, 2009]. New York Times journalist Walter Sullivan even declared the expedition to be “an incursion of females” into “the largest male sanctuary remaining on this planet” [Carey et al., 2016]. Other groups, including the Navy, expressed concern about whether the women would successfully complete the expedition.

Terry Tickhill Terrell, Eileen McSaveny, and a crowd of U.S. Navy servicemen stand outdoors at McMurdo Station. Credit: The Ohio State University, Byrd Polar and Climate Research Center Archival Program, Lois M. Jones Papers

This skepticism only fueled the team’s determination to succeed.

In November 1969, Jones and her colleagues arrived in Antarctica to begin their work. To prove that women could successfully conduct research in Antarctica, the team asked for help from support staff as infrequently as possible during their 4-month-long stay, requesting supplies only when absolutely necessary.

The expedition experienced tremendous successes, both scientific and otherwise. Jones and a colleague, using samples the team had collected, revealed insights into the sources and implications of strontium isotopes in Taylor Valley [Jones and Faure, 1978]. McSaveney gathered additional geologic samples as part of her graduate studies, and Lindsay collected springtails and mites for her research. Accompanying the Navy to the South Pole, the four researchers, alongside two other women (New Zealand biologist Pam Young and Detroit Free Press journalist Jean Pearson), also became the first women to ever visit the South Pole.

Breaking the Ice

The trip and its success had historic implications, although not everyone immediately embraced the idea of women on polar research expeditions. For example, the British Antarctic Survey continued to bar women from participating in Antarctic expeditions until 1987, when glaciologist Elizabeth Morris finally joined a field team [Carey et al., 2016]. Despite such stances, the 1969 expedition broke a barrier and contributed more broadly to the growing momentum of women in science.

After the Jones expedition, the U.S. Navy officially began accepting women at McMurdo Station, the country’s largest Antarctic outpost, and more women flew in to conduct research on the frozen continent.After the Jones expedition, the U.S. Navy officially began accepting women at McMurdo Station, the country’s largest Antarctic outpost, and more women flew in to conduct research on the frozen continent, setting additional records along the way. In 1970, Irene Peden, an engineering professor at the University of Washington, became the first woman to conduct research in Antarctica’s interior. She later spent an entire winter at the South Pole in 1979, becoming the first woman ever to do so. In 1974, physiologist Mary Alice McWhinnie became the first woman to head McMurdo Station and one of the first two, along with Mary Odile Cahoon, to spend the winter there. And in 1999, physician Jerri Nielsen became famous for her quick action after finding a lump in her breast while overwintering at the South Pole. With no other medical staff present and with no chance of a quick departure, she performed a biopsy on herself using ice and local anesthesia; then, after doctors remotely diagnosed her with breast cancer, she self-administered chemotherapy—delivered via a midwinter airdrop—until she was evacuated several months later.

The contributions of women in research publications also grew. For example, the number of women authoring research articles in the Journal of Glaciology and Annals of Glaciology increased from 10 in 1979 to 55 in 1990 [Carey et al., 2016].

Aside from the increasing presence of women in Antarctica, steps have been taken to improve gender parity across the sciences. Committees are in place to assess and encourage gender diversity in academia generally and across many disciplines, including physics, chemistry, medicine, and geoscience. Today, women account for roughly one third of all scientists visiting Antarctica and, according to the United Nations Educational, Scientific and Cultural Organization’s Institute for Statistics, 28.4% of the world’s researchers. And women lead multimillion-dollar expeditions and projects, participate in every scientific discipline, and serve in key leadership roles around the world.

Cause for Celebration

The revolutionary researchers from the 1969 expedition have reflected fondly on their Antarctic experience and have remarked on the progress of women in science. In a 2009 article by Peter Rejcek marking the 40th anniversary of the mission, Terrell recalled the heartbreak of leaving such a beautiful and stimulating environment, and McSaveney said she holds on to memories of the expedition by staying up to date on research and discoveries related to Antarctica. McSaveney also recalled having seen a documentary in the mid-2000s that showed scientists at McMurdo Station: “It was obviously so commonplace to have women working there that no particular mention of it was made in the commentary.…That told me that things are now as they should be,” she said.

Terry Tickhill Terrell stands in the team’s tent at a field site in Wright Valley during the 1969 expedition. Credit: The Ohio State University, Byrd Polar and Climate Research Center Archival Program, Lois M. Jones Papers

Sadly, both Jones and Lindsay have passed away, in 2000 and 2001, respectively. Their legacies live on, however. After her death, Jones’s estate donated 18,275 slides containing images from her personal life, travel, and research to the Byrd Polar and Climate Research Center. These slides are now stored within Ohio State’s Polar Archives. In addition, Jones donated funds toward research studying both geology and cancer through two generous endowments, the Lois M. Jones Fellowship Fund in Geological Sciences and the Lois M. Jones Endowment for Cancer Research Fellowships.

Looking toward the future, this symposium will introduce tools for engagement, share experiences and successes of women in science, and discuss changes being made across the globe to include women in all disciplines within and outside of science.This October, the Byrd Polar and Climate Research Center will host a symposium in Columbus, Ohio, commemorating the 50th anniversary of the groundbreaking expedition. Members of the public, researchers, faculty, and students are invited to celebrate the achievements of the women who made it happen and to discuss current challenges and hopes for women in science, research, discovery, and leadership. Topics will include polar research, fieldwork, and assessing gender parity in the U.S. Antarctic Program. Terry Tickhill Terrell and Eileen McSaveney will be in attendance to share their experiences. Looking toward the future, this symposium will introduce tools for engagement, share experiences and successes of women in science, and discuss changes being made across the globe to include women in all disciplines within and outside of science.

Ongoing Obstacles

Women have come a long way since the early years of Antarctic exploration.

Although inclusion of women in scientific fields has increased, challenges still arise, and women are still breaking down barriers that have been in place since long before the 1969 expedition. Broadly, women experience workplace discrimination in terms of unequal pay and harassment, and female researchers and workers in Antarctica face gender stereotypes, sexual harassment, and outright discrimination. In academia, women in higher education and research experience a “leaky pipe” scenario, with the proportion of women involved in undergraduate, graduate, and postdoctoral research and education declining at each successively more advanced level.

As women’s involvement in science and other industries becomes more commonplace, it is important to remember the fearless individuals who forged paths and set examples for women today.But the news isn’t all bad. In the past decade, workplace diversity has improved, and zero-tolerance policies have increasingly been introduced to combat workplace harassment and gender inequality. In January 2017, more than 3 million women and men marched on all seven continents in solidarity with the Women’s March on Washington. The “Me Too” movement, which began in 2006 to protect victims of sexual violence, became a viral sensation in October 2017 when celebrities brought workplace harassment into the light with their personal stories. In 2018, the National Academies of Sciences, Engineering, and Medicine released a consensus study report about the climate, culture, and consequences of workplace harassment against women. In 2019, AGU launched its Ethics and Equality Initiative, which targets harassment in the science, technology, engineering, and medicine (STEM) fields. These developments indicate that empowerment and teamwork are two key components of creating change and pushing diversity in professional and academic environments.

As women’s involvement in science and other industries becomes more commonplace, it is important to remember the fearless individuals who forged paths and set examples for women today. Remembering and celebrating victories for women in science, identifying areas where further inclusion is needed, and looking forward to a brighter future all are reasons why a 50th-anniversary celebration of the 1969 expedition is right around the corner. We hope to see you there!

Acknowledgments

I acknowledge those who contributed to this article, including Jason Cervenec, Michele Cook, Kira Harris, Laura Kissel, Kasey Krok, and Stacy Porter.

The annual increment rings found in the trunks and stems of trees tell numerous stories. Some of these stories are about climate while others are about the life of the tree, but the two are often difficult to disentangle. As a result, previous studies found conflicting results between a strong climate and carbon dioxide response of mid- and high-latitude vegetation in ecosystem models and a weaker or non-existent one in many tree ring chronologies.

Trees grow faster or slower both due to changes in surrounding species from natural processes of aging and thinning and to increases in favorable climate or nutrients. Further, sampling is typically limited to live and dominant trees at any time, further complicating analysis who entire forest growth.

Hember et al. [2019] systematically evaluate sources of biases in estimating tree growth from these rings and develop an approach that attempts to minimize those. By combining forest growth models with a large database of tree ring chronologies, the authors were able to demonstrate that environmental change contributed to significant growth in Canadian black spruce trees. 

Citation: Hember, R. A., Kurz, W. A., & Girardin, M. P. [2019]. Tree ring reconstructions of stemwood biomass indicate increases in the growth rate of black spruce trees across boreal forests of Canada. Journal of Geophysical Research: Biogeosciences, 124. https://doi.org/10.1029/2018JG004573

—Ankur Rashmikant Desai, Editor, JGR: Biogeosciences

In the 124th chapter of Herman Melville’s Moby Dick, “The Needle,” Ahab and his crew discover that their whaleship’s compass needles have reversed as a consequence of the previous day’s electrical storm. This has caused the Pequod to sail in the exact opposite direction from its intended course, dismaying the superstitious sailors. To restore their tattered confidence, Ahab resorts to a bit of geomagnetic magic.

Proclaiming that he is “lord over the level loadstone yet,” Ahab orders up “a lance without the pole; a top-maul, and the smallest of the sail-maker’s needles.” (Lodestones were magnetic rocks used as early compasses. A top maul is a large, heavy hammer used in shipbuilding.)

With these tools, Ahab gets to work.

With a blow from the top-maul Ahab knocked off the steel head of the lance, and then handing to the mate the long iron rod remaining, bade him hold it upright, without its touching the deck. Then, with the maul, after repeatedly smiting the upper end of this iron rod, he placed the blunted needle endwise on the top of it, and less strongly hammered that, several times, the mate still holding the rod as before. Then going through some small strange motions with it—whether indispensable to the magnetizing of the steel, or merely intended to augment the awe of the crew, is uncertain—he called for linen thread; and moving to the binnacle, slipped out the two reversed needles there, and horizontally suspended the sail-needle by its middle, over one of the compass cards. At first, the steel went round and round, quivering and vibrating at either end; but at last it settled to its place, when Ahab, who had been intently watching for this result, stepped frankly back from the binnacle, and pointing his stretched arm towards it, exclaimed,—“Look ye, for yourselves, if Ahab be not the lord of the level loadstone! The sun is East, and that compass swears it!”

The sailors are cowed by this stunning display of Ahab’s knowledge and power:

One after another they peered in, for nothing but their own eyes could persuade such ignorance as theirs, and one after another they slunk away.

And the episode, for Ahab, is his grandest moment:

In his fiery eyes of scorn and triumph, you then saw Ahab in all his fatal pride.

But was Ahab indeed “lord of the level loadstone”?Ahab seeks to “induce magnetization” in the needle through shock remanent magnetization.

By hammering the lance and then the carpenter’s needle, Ahab seeks to induce magnetization in the needle through shock remanent magnetization, reorganizing its magnetic domains and providing it with an accurate reading of north and south.

To do so, he should have aligned the lance with the Earth’s magnetic field. In 1851, the date of the publication of Moby Dick, the magnetic North Pole would have been located in Canada’s far northern Boothia Peninsula.

At this point in Moby Dick, however, the Pequod is moving into the Pacific well southeast of Japan, where the dip of the field would be about 41°. With lance and needle being held upright, this would have thwarted Ahab’s magnetization attempt.

In addition, Ahab makes a fatal error: He treats his mariner’s compass as if it were a landlubber’s compass. A Brunton is an example of a landlubber’s compass: The needle swings freely and independently above the compass rose printed on the compass base.

There are six cylindrical bar magnets attached underneath the compass card in a mariner’s compass, like this one, and the lubber line is equivalent to the projection at top. Although this compass is relatively modern, mariner’s compasses have been in use for hundreds of years and would have been used on the fictional Pequod. Credit: John Baranosky

A mariner’s compass is quite different: The pairs of needles, one of each pair on each side of the pivot, are affixed to the base of the compass rose, which swings as a unit upon the pivot. This “compass card” maintains its orientation with the geomagnetic field as the ship itself changes direction. The helmsman reads the ship’s direction from the position of the compass card in relation to a “lubber line” marking the bow-to-stern axis of the ship.

With Ahab having removed their needles, the Pequod’s compass cards would point in some unknown, arbitrary direction. A magnetized needle suspended by a thread may have pointed north, but the compass card it would have been held above would not reliably indicate that. Further, any change in the ship’s direction would not result in a change in the orientation of the Pequod’s compass card.

Despite the failure of Ahab’s “magic,” Melville says it awed the Pequod’s crew, as does Moby Dick itself on this 200th anniversary of its author’s birth.

—Dan Dorritie (dorritie@dcn.davis.ca.us). For an extended version of this article, please contact the author.

In the northern reaches of the Atlantic Ocean, warm, salty waters—delivered from the tropics by prevailing winds—cool and sink before flowing back toward the Southern Hemisphere. This process, known as the Atlantic Meridional Overturning Circulation (AMOC), transports heat and nutrients and plays a key role in Earth’s climate system.

Decades of research have deepened scientists’ understanding of the AMOC and its importance. Now a study by Johnson et al. synthesizes recent advancements in modeling the fundamental processes that drive and maintain this powerful circulation system.

The new review focuses on theoretical models that deal with pared-down conceptual perspectives on the AMOC, rather than on more complex attempts at realistic simulations. The authors discuss progress in modeling the many large- and small-scale factors that influence the AMOC, from Southern Hemisphere wind patterns and intermediate-sized eddies to the shape of continents and the bathymetry of ocean basins.

Recent theoretical models have also explored variability and anomalies in the AMOC, not just its average patterns. Some have explored why the AMOC exists in the first place, instead of a Pacific meridional circulation system. And other theoretical studies have aided interpretation of real-world observations, such as those made by the ongoing Rapid Climate Change–Meridional Overturning Circulation and Heatflux Array project, which uses an array of sensors to continuously measure AMOC dynamics at 26.5°N latitude.

In addition to compiling recent advancements, the study addresses what is on the horizon for continuing research in this field. For instance, theoretical approaches may help researchers interpret measurements from ongoing observational projects, such as the Overturning in the Subpolar North Atlantic Program (OSNAP), and may generate hypotheses that could be tested using the newly collected data.

The authors emphasize the critical role of theoretical modeling in understanding the AMOC and in linking that understanding to ocean and climate models, which could improve understanding of how the AMOC influences and is influenced by climate change. (Journal of Geophysical Research: Oceans, https://doi.org/10.1029/2019JC015330, 2019)

—Sarah Stanley, Freelance Writer

In Japan’s mountains, torrents of water cascade down steep ridges, flow beneath cedar boughs in unmanaged forests, stream through farms maintained by an aging rural population, and, finally, course past the urban areas to which many younger citizens have flocked. By the time this water reaches the rivers that feed local drinking supplies, it has picked up a lot of evidence of the land it has traversed, including nutrient pollution.

Nutrient pollution, or an excess of nutrients such as nitrogen and phosphorus in the water, can lead to a host of health and environmental problems. Many nutrients enter rivers as runoff from farms and residential areas. Scientists have also suggested that forest soils may generate nutrient runoff, especially in coniferous forests where soil surfaces are often bare and prone to erosion.

As global climate warms and strong rainstorms become more frequent throughout the world, researchers are wondering how the increase in heavy precipitation might affect nutrient pollution. In a new study, Ide et al. studied the Hii River basin in western Japan to understand how nitrogen and phosphorus levels there fluctuate with rainfall.

Over an 18-year period, the team collected water samples from subbasins within the larger river basin and from the area where the entire basin drains into a single river. They measured concentrations of nitrate, phosphate, total nitrogen, and total phosphorus and then analyzed their data with a model designed to evaluate many possible factors, including land cover, and relationships that could explain patterns seen in their results.

The researchers found that the relationship between nutrient concentrations and surrounding land types was strongest during times of heavy rain and high river flow. Agricultural land always leached phosphorus and nitrogen but did so even more during heavy rains. In contrast, forests of all types helped dilute excess nutrients, reducing nutrient concentrations even more during periods of heavy rain.

On farms, nutrients from fertilizers accumulate over time and are flushed out in high doses with rainfall—an issue that may be exacerbated in Japan. Proper fertilizer use tends to require a lot of work, and the aging farming population of Japan often opts instead for fewer, heavier fertilizer applications, the researchers noted. The team found that even a small stretch of agricultural or residential land had a disproportionately large effect on nutrient levels in the rivers studied.

The scientists predict that as heavy rainstorms occur more frequently and as young people continue migrating from rural to urban areas, nitrogen and phosphorus levels in Japan’s rivers will go on rising, affecting the drinking water and lakes downstream. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2018JG004513, 2019)

—Elizabeth Thompson, Freelance Writer

Knowing streamflow up to the smallest tributary is important for the understanding the global water cycle, the role of freshwater systems in nutrient and carbon cycling, and how water depths and velocities impact freshwater biodiversity. However, until now, streamflow was only available at resolutions coarser than 10 kilometers using global hydrological models or as observations at points.

A group of hydrologists from the United States, China, and Japan used a combination of hydrological modeling, over 14,000 streamflow observations, machine learning, and a new bias-correction method to estimate natural streamflow (without impacts of dams and water use) for over 2.94 million individual river reaches worldwide.

Lin et al. [2019] is not only an important resource for hydrological, biogeochemical and ecological research, but this dataset will also serve as a much-needed benchmark for estimating streamflow from space with the upcoming Surface Water and Ocean Topography (SWOT) mission.

Citation: Lin, P., Pan, M., Beck, H. E., Yang, Y., Yamazaki, D., Frasson, R., et al. [2019]. Global reconstruction of naturalized river flows at 2.94 million reaches. Water Resources Research, 55. https://doi.org/10.1029/2019WR02528

—Marc F. P. Bierkens, Editor, Water Resources Research

Increased rainfall in East Africa caused by a particularly strong El Niño and subsequent weather conditions may have helped usher in one of the worst cholera epidemics in modern history in war-torn Yemen.

“In Yemen, there is a catastrophic crisis in terms of human health and the availability of fresh water,” said Shlomit Paz, head of the Department of Geography and Environmental Studies at the University of Haifa in Israel and author of a research note published in July in Environmental Research.

Yemen has been embroiled in a civil war since 2015, and the cholera epidemic has been ongoing since 2016–2017. Cholera bacteria thrive in untreated water, and the Yemeni outbreak may be due to the breakdown of basic infrastructure (including water sanitation facilities) in the country. Estimates of more than 1.2 million infections make the Yemeni cholera epidemic “the largest in epidemiologically recorded history.”

Early Outbreaks in East Africa

Cholera cases first started to pick up in Somalia and surrounding countries in 2016, coinciding with particularly heavy rainfall due to extreme El Niño conditions.

Paz said it’s possible the cholera bacteria that started the epidemic in Yemen may have migrated out of East Africa through human hosts, but they also may have been carried by small insects. Chironomids, small midges that spend their early life stages in water, are known to carry the disease and can transmit bacteria between water reservoirs, she said.

Strong winds blowing from the Horn of Africa across the Gulf of Aden in July, August, and September 2016 could have carried the midges northeastward to Yemen, Paz said. There, they may have infected water supplies that helped start the epidemic.

Colin Stine, a professor of epidemiology at the University of Maryland who was not involved in Paz’s paper, isn’t sure that midges would have been able to carry sufficient loads of cholera bacteria to cause the epidemic in Yemen. He agreed that the Yemeni cholera epidemic likely originated in East Africa but thinks it came from a human source rather than from midges.

“It is very clear that climate change has a lot of effect on vector- and food-borne diseases.”Stine said that just one human can carry cholera bacteria in amounts orders of magnitude higher than many midges could.

“The weakness of the paper [is] that it doesn’t have those kinds of calculations in it,” Stine said.

Stine said it’s hard to disprove the El Niño theory, but he pointed to a similar idea that circulated around a 2010 cholera epidemic in Haiti. Some researchers initially believed that weather conditions prompted by La Niña had a hand in causing the outbreak, but it was later found to have originated in a United Nations peacekeeping camp in the Caribbean country.

Regardless, Paz said that health authorities would gain a lot from monitoring weather conditions, especially because the warming climate will create ideal conditions for the rapid spread of disease.

“It is very clear that climate change has a lot of effect on vector- and food-borne diseases,” Paz said. “In order to be prepared for such an epidemic, I think that first of all there is a need for constant monitoring and forecasting—collaboration between scientists and doctors.”

Stine agreed that there should be more dialogue between environmental scientists and doctors tracking the spread of disease, though he’s not sure how important this will be for monitoring the spread of cholera.

—Joshua Rapp Learn, Freelance Journalist