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Crustal brines at an oceanic transform fault: New research explores geological processes along plate boundaries

Phys.org: Earth science - Mon, 04/14/2025 - 15:16
In an article published in Science Advances, a collaborative team led by the Woods Hole Oceanographic Institution (WHOI) presents a never-before-seen image of an oceanic transform fault from electromagnetic (EM) data collected at the Gofar fault in the eastern Pacific Ocean.

Climate Shifts Drive Episodic Drainage Changes

EOS - Mon, 04/14/2025 - 13:21

The locations of drainage divides determine how water flows across a landscape. Now, a new study has revealed how quickly these features can migrate when a region’s normally dry climate gets a little wetter.

Researchers used a combination of field observations, sediment dating, and numerical modeling to show how a river system in Israel’s Negev Desert has made sudden shifts in response to known wet periods. Drainage divides that migrated at an average rate of 1.1 kilometers (0.7 mile) per million years over the studied interval stalled and picked up speed in step with known shifts in the region’s climate.

“To my knowledge, this is the first study that directly measures rates of drainage divide migration,” said Mikaël Attal, a geomorphologist at the University of Edinburgh in Scotland who was not involved in the research. “This is important because drainage migration can have implications for understanding erosion across landscapes, our ability to infer tectonics from topography, and the management of water resources.”

Drainages Move Slowly, Then All at Once

Water falling on a landscape flows downhill, accumulates in rivers, and eventually drains into lakes, wetlands, or oceans. Drainage divides are topographic boundaries that control the water’s path.

“If a drop of water falls on one side or the other of a drainage divide, it will follow a different route,” Attal said. He used North America’s Great Divide as an example: “If a drop falls on the west side of the divide, it goes to the Pacific; if it falls on the other side, it goes to the Atlantic.”

A drainage divide migrates when the rivers on one side of the ridge erode more rapidly than on the other. In response, rivers may change their course or even reverse direction.

Because divide migration has a significant effect on landscapes, researchers are interested in how—and how quickly—it happens. But so far, it has been difficult to determine the rate at which drainage divides migrate on short timescales.

“Geomorphic markers capable of recording past divide locations, such as alluvial terraces, are often eroded away,” explained Elhanan Harel, a geomorphologist at the Geological Survey of Israel and a coauthor of the study, which appeared in Proceedings of the National Academy of Sciences of the United States of America.

Most of the movement happened in two intervals, during which the drainage divide migrated across the landscape at twice the average rate.

Previous studies have used cosmogenic nuclide dating to measure erosion on either side of drainage divides. These erosion rates, along with other variables, were fed into an equation that estimates the rate of drainage divide migration.

This approach, however, presents several drawbacks. The equation relies on a simplified geometric model of the drainage divide, which may not accurately describe a specific site. In addition, cosmogenic nuclide dating provides erosion rates that are averaged over a river basin, which may not match erosion at the drainage divide. The erosion rates inferred from cosmogenic nuclides are also time averaged, making it impossible to track short-term changes.

Harel and his coauthors overcame these difficulties by studying unusually well-preserved river terraces in Israel’s dry southern Negev Desert. River terraces, created as rivers slowly erode and leave behind steps that represent previous levels of the valley floor, are valuable markers of regional geomorphology. At the Negev Desert site, each terrace records a past location of the drainage divide, enabling Harel and others to trace the divide’s migration step by step.

The researchers used a technique called optically stimulated luminescence to date when the terraces formed. Collating dates on the sequence of terraces, they reconstructed the drainage divide’s 258-meter migration over the past 227,000 years.

Most of the movement, they found, happened during two intervals, from 245,000 to 183,000 years ago and 36,000 to 26,000 years ago, during which the divide moved across the landscape at twice the average rate.

Wet Climates May Drive Rapid Migration

Although the southern Negev Desert has been mostly dry for at least a million years, its arid state has been punctuated by occasional wet periods: One occurred around 220,000–190,000 years ago, and another took place between 35,000 and 20,000 years ago. These periods coincide with intervals of rapid drainage migration.

Increased weathering and the timing of groundwater recharge in the southern Negev indicate that extreme storms and floods occurred at those times.

The researchers simulated the physical processes of river incision to evaluate whether climate shifts could explain the observed divide migration rates. They found that a scenario assuming constant climate conditions couldn’t reproduce their observations from the Negev, but one that included intermittent climate shifts matched the results exactly.

“Our study provides the first direct evidence linking divide migration to climate fluctuations on much shorter timescales.”

The new analysis supports the idea that climate and rainfall drive landscape changes. “While previous studies have demonstrated that tectonic forces can drive divide migration over million-year timescales, our study provides the first direct evidence linking divide migration to climate fluctuations on much shorter timescales,” Harel said.

Attal agreed that the study helps researchers understand the connection between climate and drainage patterns. “It is very interesting that [the authors] found that the divide tends to migrate in bursts during wet periods,” he said.

This knowledge may be increasingly relevant as extreme weather events—such as severe rain, storms, and floods—become more common because of climate change. In flat areas with an abundance of loose sediment, severe flooding could divert rivers and shift drainage divides, causing permanent changes to the landscape.

“I think this work highlights that some landscapes may be highly sensitive to climate change,” said Attal.

—Caroline Hasler (@carbonbasedcary), Science Writer

Citation: Hasler, C. (2025), Climate shifts drive episodic drainage changes, Eos, 106, https://doi.org/10.1029/2025EO250139. Published on 14 April 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

When Ice Ages End, Ocean Circulation Fine-Tunes Ocean Heat

EOS - Mon, 04/14/2025 - 13:20
Source: Geophysical Research Letters

Much of Earth’s heat uptake is passed to the ocean, making ocean heat content key for understanding long-term climate patterns. Ocean heat content is typically lower during ice ages and rises during warmer periods of glacier retreat. Over the past 1.2 million years, ice ages and interglacials have occurred in cycles lasting about 100,000 years, and we are currently in an interglacial period after the Last Glacial Maximum occurred about 20,000 years ago.

Recent climate modeling studies have suggested that ocean heat content also changes on shorter timescales of just a few thousand years as a result of intermittent changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC)—a pattern of Atlantic Ocean currents that carries warm water north and cold water south. The models suggest that a weaker AMOC leads to increased ocean heat content. However, real-world evidence to support or refute AMOC’s potential influence on ocean heat content has been limited.

Grimmer et al. present the first record of ocean heat content during the ends of the last four ice ages and the subsequent warm periods, enabling the team to test modeling predictions against paleoclimate data.

To generate the new record, the researchers analyzed the ratios of specific noble gases trapped within 59 new samples from a 3,260-meter-long ice core drilled in East Antarctica as part of the European Project for Ice Coring in Antarctica (EPICA). The noble gas ratios in different ice layers serve as fingerprints of ocean heat content at various times in Earth’s past.

Analysis of the new record showed that at the end of each of the last four ice ages, ocean heat content generally increased alongside a weaker AMOC, as predicted by the models. These transitions to warmer interglacial periods, known as deglaciations, last several thousand years. The record also showed evidence of millennial-scale changes in ocean heat content that occurred alongside changes in ocean circulation. When the AMOC strengthened, ocean heat content either increased at a slower pace or decreased.

These findings align with the prior modeling predictions, supporting the idea that on millennial timescales, the AMOC plays a key role in controlling heat uptake by Earth’s oceans. In turn, this interaction likely influences subsequent sea levels, climate conditions, and atmospheric carbon dioxide levels. (Geophysical Research Letters, https://doi.org/10.1029/2024GL114415, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), When ice ages end, ocean circulation fine-tunes ocean heat, Eos, 106, https://doi.org/10.1029/2025EO250137. Published on 14 April 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Nonlinear Dynamics May Lead to Faster Retreat of Antarctic Ice

EOS - Mon, 04/14/2025 - 12:00
Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Geophysical Research Letters

Ice sheets are formed by the slow transformation of snow into ice. Large masses of ice, such as the Antarctic ice sheet, deform under their own weight and transport the ice from the interior of the continent to the coast, eventually breaking off and forming icebergs. The flow of ice is non-Newtonian, which means that its viscosity decreases as it deforms more. Recent research has shown that this effect may be even stronger than what current computer models use.

Getraer and Morlighem [2025] evaluate what the consequences of ice being an even more nonlinear material may be on its stability and contribution to sea level rise. The authors find that the sector of Thwaites glacier in West Antarctica would lose 32% more ice by 2100, and 70% by 2300. Current estimates of the future contribution of the ice sheets to sea level may therefore be strongly underestimated.

Citation: Getraer, B., & Morlighem, M. (2025). Increasing the Glen–Nye power-law exponent accelerates ice-loss projections for the Amundsen Sea Embayment, West Antarctica. Geophysical Research Letters, 52, e2024GL112516. https://doi.org/10.1029/2024GL112516

Minghua Zhang, Former Editor-in-Chief, Geophysical Research Letters

Text © 2024. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Arctic matter pathways are poised for major shifts amidst climate change, Transpolar Drift study finds

Phys.org: Earth science - Mon, 04/14/2025 - 09:00
A new study has shed light on the highly variable and climate-sensitive routes that substances from Siberian rivers use to travel across the Arctic Ocean. The findings raise fresh concerns about the increasing spread of pollutants and the potential consequences for fragile polar ecosystems as climate change accelerates.

A Simple Method for Improving the Resolution of Geodetic Slip Inversion

Geophysical Journal International - Sat, 04/12/2025 - 00:00
SummaryIn geodetic slip inversions, resolution decreases rapidly with depth because deformation data are measured at the ground surface. Traditionally, this decrease in resolution has been attributed to the weak deformation signals caused by slips at greater depths. However, this study demonstrated that the primary cause is the stronger smoothing applied to deeper slips compared to shallower ones. This work proposes a method that scales the Green's functions to equalize smoothing effects across depths. The method's effectiveness was validated through both synthetic tests and real earthquake applications. In synthetic tests, it improved recovery of deep slips in both location and amplitude. When applied to the 2008 MW7.9 Wenchuan earthquake, the method produced smaller slips near the ground surface and larger slips at depth. For the land-based deformation inversion of the 2011 MW9.0 Tohoku earthquake, the method resulted in larger shallow slips near the trench and greater sea-floor uplift compared to the conventional inversion, which is valuable for accurate prediction of tsunami wave height. Additionally, this method may also be applicable to other inversions where smoothing is used and observation amplitudes vary with distance.

NASA Science Faces an “Extinction-Level Event” with Trump Draft Budget Proposal

EOS - Fri, 04/11/2025 - 19:53
body {background-color: #D2D1D5;} Research & Developments is a blog for brief updates that provide context for the flurry of news regarding law and policy changes that impact science and scientists today.

The initial draft of President Donald Trump’s budget request proposes devastating cuts to NASA’s science research, future space missions, and field centers. The draft budget request, reported by Ars Technica and The Washington Post, proposes an overall 20% cut to NASA’s budget, from about $25 billion to $20 billion.

“This is an extinction-level event for NASA science,” Casey Dreier, chief of space policy for the Planetary Society, told The Washington Post. “It needlessly terminates functional, productive science missions and cancels new missions currently being built, wasting billions of taxpayer dollars in the process. This is neither efficient nor smart budgeting.”

The overwhelming majority of the cuts would come from NASA’s Science Mission Directorate (SMD), which would face a more than 50% cut from $7.5 billion to just $3.9 billion. This division includes all planetary science, Earth science, astrophysics, heliophysics, and biological and physical science research.

The draft budget request proposes a 68% cut to astrophysics (from $1.5 billion to $487 million), a more than 43% cut to heliophysics (from $805 million to $455 million), a 30% cut to planetary science (from $2.7 billion to $1.9 billion), and a 53% cut to Earth science (from $2.2 billion to $1.033 billion).

The proposal retains funding for the Hubble Space Telescope and the James Webb Space Telescope, but kills funding for the upcoming Nancy Grace Roman Space Telescope, which is fully assembled, on budget, and on schedule to launch in 2 years.

Also on the chopping block are the funding for the DAVINCI+ mission to Venus and the Mars Sample Return joint mission with the European Space Agency, which has been a budgetary flashpoint for years.

Casey Dreier (@caseydreier.bsky.social) 2025-04-11T17:45:09.472Z

NASA’s Earth science division within SMD is home to NASA’s Earth observing satellite programs and climate research. Combined with continued attacks on NOAA and the National Weather Service, such steep budget cuts to NASA Earth science would nearly eliminate the United States’s capacity to study climate change and protect people from increasingly severe climate impacts.

The draft budget also appears to seek to force the closure of NASA’s Goddard Space Flight Center in Greenbelt, Md., which employs more than 10,000 civil servants and contractors.

 
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“NASA Goddard and the NASA science missions are critical to discovering the secrets of the universe and the planet we live on and have a direct bearing on our leadership in technological innovation and our national security,” wrote U.S. Senator Chris Van Hollen (D-Md.) in a statement. Van Hollen is the Ranking Member of the Appropriations Subcommittee on Commerce, Justice, Science, and Related Agencies.

“This is a wholly unserious budget proposal,” Van Hollen noted. “I will fight tooth and nail against these cuts and to protect the critical work being done at NASA Goddard.”

On 9 April, Jared Isaacman, Trump’s nominee for NASA administrator, said in his Senate hearing that he had no knowledge of any planned budget cuts to NASA and had no present intentions of cancelling existing programs. Notably, he did not commit to keeping all NASA field centers open given multiple chances to do so. Isaacman repeatedly emphasized that he was committed to ensuring U.S. dominance in the space race against China, which also seeks to put humans on the Moon and Mars, as well as expand its exploration science program throughout the solar system. These budget cuts would make that goal much harder to achieve.

With Trump’s proposed NASA budget…1st samples from Mars:

Low Latitude TEC Disturbances during Extreme Geomagnetic Storms: Insights into March and May 2024

Publication date: Available online 2 April 2025

Source: Advances in Space Research

Author(s): C. Pansong, P. Wongsak, S. Ruttanaburee, P. Pornsopin, P. Kenpankho

Ionospheric Response to the 2004 Sumatra-Andaman Earthquake: Evaluation of a Novel Histogram-Based Metric

Publication date: Available online 2 April 2025

Source: Advances in Space Research

Author(s): Ali Öztürk, Ramazan Atıcı

Atmospheric concentrations of CH<sub>4</sub> in central-western areas of Brazil for 2009–2019 using GOSAT satellite

Publication date: 1 April 2025

Source: Advances in Space Research, Volume 75, Issue 7

Author(s): Luciano de Souza Maria, Fernando Saragosa Rossi, Luis Miguel da Costa, Marcelo Odorizzi Campos, Alan Rodrigo Panosso, Carlos Antonio da Silva Junior, Newton La Scala

CO₂ removal and storage: Which options are feasible and desirable?

Phys.org: Earth science - Fri, 04/11/2025 - 15:49
As climate change increases, so does the pressure on humanity to remove carbon dioxide (CO2) from the atmosphere—possibly with the help of the oceans. But which of the proposed marine CO2 removal and storage options should be used?

O'ahu's shores could see heavy erosion by 2030, study finds

Phys.org: Earth science - Fri, 04/11/2025 - 15:49
O'ahu's sandy beaches are at risk. New research from the Coastal Research Collaborative (CRC) at the University of Hawai'i (UH) at Mānoa determined that 81% of O'ahu's coastline could experience erosion by 2100, with 40% of this loss happening by 2030. Importantly, these forecasts of shoreline erosion are more extreme than previous studies indicated for Oʻahu. The study was published recently in Scientific Reports.

Climate warming increases flood risks from rain-on-snow events in high mountain Asia, study finds

Phys.org: Earth science - Fri, 04/11/2025 - 15:05
A recent study led by Prof. Chen Yaning from the Xinjiang Institute of Ecology and Geography of the Chinese Academy of Sciences has found that climate warming is increasing flood risks from rain-on-snow (ROS) events in High Mountain Asia. The study, published in npj Climate and Atmospheric Science, analyzed the distribution, causes, and flood risks of ROS events.

Hundred-year storm tides to hit Bangladesh every decade as climate change intensifies, scientists report

Phys.org: Earth science - Fri, 04/11/2025 - 15:05
Tropical cyclones are hurricanes that brew over the tropical ocean and can travel over land, inundating coastal regions. The most extreme cyclones can generate devastating storm tides—seawater that is heightened by the tides and swells onto land, causing catastrophic flood events in coastal regions.

Missing nitrogen: A dramatic game of cosmic hide-and-seek deep within our planet

Phys.org: Earth science - Fri, 04/11/2025 - 13:54
Imagine if Earth's history had a mystery novel, and one of its biggest unsolved puzzles was: Where did all the nitrogen go? Scientists have long known that our planet's rocky outer layers—the mantle—are oddly poor in nitrogen compared to other volatile elements like carbon or water. Very strangely, the C/N and 36Ar/N ratios in the bulk silicate Earth (BSE, the whole Earth minus the metallic core) are far higher than those found in the meteorites that supposedly delivered these ingredients during the planet's infancy.

New Insights into an Enigmatic Form of Magnetic Reconnection

EOS - Fri, 04/11/2025 - 13:26
Source: Geophysical Research Letters

In magnetic reconnection, adjacent magnetic field lines break and snap together to form new lines. This process converts magnetic energy to both thermal energy, or heat, and kinetic energy, or the acceleration of particles, creating jets of electrons and ions. Magnetic reconnection plays a key role in many outer space events such as solar flares and aurorae, as well as in laboratory methods related to nuclear fusion.

Several years ago, observations of Earth’s magnetic field by NASA’s Magnetospheric Multiscale mission led to the discovery that magnetic reconnection can occur with only electron jets, without also involving the acceleration of ions. These events also have a relatively high reconnection rate, meaning the involved magnetic field lines snap together quickly. Now Fan et al. report the results of new simulations that deepen the understanding of these electron-only events.

The researchers applied a computational method known as particle-in-cell simulation to model the behavior of ions and electrons during magnetic reconnection. They ran 12 simulations to explore what factors might underlie electron-only reconnection.

The simulations revealed that the electron-only status of reconnection occurs when field lines outside of the electron diffusion region do not bend enough, leading to an underdeveloped ion diffusion region. This atypical bending happens in the early stage and may continue throughout the process if the entire system size (the size of the area in which reconnection occurs) is smaller than the radius of the path along which the ions travel.

The team also realized that magnetic reconnection and field line bending may not develop at the same pace. A relatively thin initial current sheet allows the reconnection rate to peak before field lines are fully bent, leading to calculations of high reconnection rates if they are normalized by ion parameters. However, the calculations of the reconnection rate are more typical when they are normalized by electron parameters.

These findings could help clarify the fundamental physics of magnetic reconnection, the authors suggest. (Geophysical Research Letters, https://doi.org/10.1029/2024GL113889, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), New insights into an enigmatic form of magnetic reconnection, Eos, 106, https://doi.org/10.1029/2025EO250138. Published on 11 April 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Unlocking Climate Secrets of Hawai‘i’s Drowned Reefs

EOS - Fri, 04/11/2025 - 13:24

Cycles of ice sheet growth (glacials) and intervening warmth (interglacials) in Earth’s past—largely triggered by shifts in the amount of solar radiation (insolation) reaching the planet—have been characterized by major changes in global atmospheric carbon dioxide (CO2) levels, sea levels, and temperatures. Around the time of the Last Glacial Maximum 20,000 years ago, for example, average global temperatures were roughly 6°C (11°F) colder, and sea levels were more than 120 meters (400 feet) lower than today, whereas ice covered about a quarter of Earth’s land surface.

Such changes have had profound effects on ecosystems, particularly coastal ecosystems, including coral reefs. And as CO2 levels, temperatures, and sea levels rise rapidly around the world today, modern ecosystems—humans included—will likely continue to experience major impacts as well.

Coral reef systems are highly sensitive to sea level and climate, and fossil reefs preserve reliable records of past variations.

Yet many unknowns remain about the mechanisms that control climate transitions, particularly during past episodes of rapid warming. These unknowns raise critical questions about present and future warming as well: Are predictions of catastrophic sea level rise—up to several meters—resulting from ice sheet collapse valid? Will the behavior and effects of annual to interannual climate phenomena, such as the El Niño–Southern Oscillation and seasonal rainfall, change as the average global climate changes?

Also uncertain is how coral reefs and coasts will respond to associated environmental stresses. Coral reef systems are highly sensitive to sea level and climate, and fossil reefs preserve reliable records of past variations. Yet our understanding of these variations is severely limited because we lack continuous fossil coral records, particularly from periods of abrupt climate instability. Such records are exceptionally rare given the specific conditions required to build and preserve fossil reef sequences over extended periods and the difficulty of sampling them where they do occur.

In fall 2023, scientists and crew on the International Ocean Discovery Program’s (IODP) Expedition 389 (X389) employed an advanced, remotely operated seabed drilling system to access the interiors of submerged, or “drowned,” fossil reefs off the island of Hawai‘i for the first time (Figure 1). The reef sequences there contain globally unique records of sea level and climate change—and their impacts on reef ecosystems—over the past 500,000 years [Webster et al., 2025].

Fig. 1. A unique sequence of drowned fossil coral reefs was sampled off Hawai‘i during X389. (a) Sampling sites (red markers) are indicated along with their depths below sea level and name (H1, H2, etc.). (b) Sea level changes (blue curve) are shown through the cold glacials (blue shading) and warm interglacials (orange shading) over the past 600,000 years [Rohling et al., 2009; Elderfield et al., 2012; Lambeck et al., 2014]. New preliminary age data (red bars) confirm that reefs H1–H8 (gray bars) span 13 glacial-interglacial intervals (termed marine isotope stages (MIS), numbered boxes), including rapid climate transitions. ka = thousand years ago. Credit: Adapted from Webster et al. [2025], CC BY 4.0 Hawai‘i’s Unique Reef Records

Hawai‘i is geologically special. Located over an active volcanic hot spot, it has been—and continues to be—built up by successive eruptions. As the underlying mantle compensates for the increasing weight of the island, the ocean crust has experienced nearly constant subsidence over the past 500,000 years. This subsidence creates space that accommodates growth and vertical expansions of reefs, which, as they accumulate and fossilize, capture conditions through glacial-interglacial intervals in great detail (Figures 1b and 2). These reefs ring the island, forming a spectacular sequence of increasingly older terraces between 100 and 1,500 meters below present sea level (Figure 1a).

Rapid sea level rises linked to catastrophic ice sheet collapse and abrupt meltwater pulse events during deglaciations cause reef drowning.

The reefs have been the subject of 4 decades of data collection and study involving multiple methods of seafloor imaging (bathymetric, backscatter, and seismic) and sampling (with dredges, submersibles, and remotely operated vehicles), as well as geochronologic methods and numerical modeling [Webster et al., 2009]. These prior data underpin our knowledge of fossil reef development and motivated the scientific rationale and drilling strategy of X389.

As Hawai‘i subsides at a rate of 2.5 millimeters per year, space below the ocean surface is created for reef growth in the near term (Figure 2). But how do large and longer-term sea level changes occurring through glacial-interglacial intervals affect reefs?

Reef growth initiates during sea level highstands and continues during glaciation as sea levels slowly drop. If sea level falls quickly, outpacing the island’s subsidence rate, the living part of the reef dies as it is exposed above the waves. If, on the other hand, sea level rises too quickly and new reef growth—which requires the sunlight available near the ocean surface—fails to keep up, the reef will deepen and ultimately drown.

Fig. 2. This conceptual model illustrates the development and accumulation of drowned fossil coral reefs and other rock facies (e.g., microbialites, volcanic deposits) in different paleoenvironments around Hawai‘i over the past 100,000 years in response to rapid island subsidence, which creates accommodation space (double-headed arrow), and changing sea levels (dark blue curve). ka = thousand years ago; mbsl = meters below sea level. Credit: Adapted from Webster et al. [2025], CC BY 4.0

Rapid sea level rises linked to catastrophic ice sheet collapse and abrupt meltwater pulse events during deglaciations thus cause reef drowning [Sanborn et al., 2017]. Then, during the subsequent warm high sea level stand, a new reef is initiated upslope, and the cycle starts again.

Numerical models of reef growth and demise, forced by changes in sea level, predict that the Hawaiian terraces comprise thicker sequences of fossilized reef—100–150 meters per glacial cycle—compared with those built on stable margins such as the Great Barrier Reef. As such, the Hawaiian expanded sequences hold great promise for providing sea level and climate records of unprecedented resolution and detail.

To sample these Hawaiian reefs across a range of water depths and challenging lithologies (they commonly fragment and break), researchers required a novel drilling system—unavailable to the scientific community until recently—that could penetrate the reef interior rather than just scratch its surface.

The Core of the Matter

The X389 team found the needed technology in Benthic’s fifth-generation portable remotely operated drill (PROD5). This commercial, tethered device can be guided to and secured at seafloor targets as deep as several kilometers, where its automated capabilities allow it to collect long sample cores (up to 73 meters below the seafloor in the case of X389). A major advantage of seafloor drills over ship-based systems is that they’re stationary, which makes it easier to keep constant weight on the drill bit and improves recovery of continuous core segments.

Scenes from X389’s drilling operations show the PROD5 drill (a) being deployed over the side of the MMA Valour and (b) landing on the seafloor, as well as (c) team members processing and archiving a core collected from a well-preserved fossilized massive Porites coral. Credit: Jody Webster

Sailing aboard the MMA Valour, the expedition used PROD5 to obtain reef material from roughly the past 500,000 years to address four major objectives: (1) measuring the extents of past sea level variations, (2) investigating seasonal to millennial climate and oceanic change, (3) assessing coral reef ecosystem responses to abrupt sea level and climate changes, and (4) improving knowledge of the growth and subsidence of Hawai‘i over time.

Over the course of 2 months in fall 2023, we deployed the drill at 16 drowned reef sites offshore Hawai‘i, coring 35 holes at water depths ranging from 132 to 1,242 meters (Figure 1a). A total of 425 meters of core were recovered, comprising both reef (83%) and volcanic (17%) materials. Core recoveries averaged 66%, and numerous intervals of well-preserved reef samples exhibited recoveries greater than 90%, significant achievements compared with recoveries from prior expeditions. For example, core recoveries averaged 27% using a ship-based drilling system during Expedition 325 to the Great Barrier Reef in 2010 [Webster et al., 2011].

The deployments were largely successful, but the expedition was not all smooth sailing.

The deployments were largely successful, but the expedition was not all smooth sailing. Technical issues with the drill, including mechanical breakdowns and difficulties penetrating heterogeneous coral reef material, limited our ability to reach all target depths.

Moreover, the expedition did not adequately engage with community members about the plans and purpose of its research or about concerns it may have posed. This regrettable oversight alienated members of the local and Native Hawaiian communities, some of whom expressed frustration at not being informed or consulted prior to the Valour’s arrival offshore and voiced uncertainties over possible environmental harms.

In addition to damaging the expedition’s relationship with local communities, the lack of timely and vital engagement directly affected the science we could pursue. The concerns raised by community members contributed to the denial of a permit to drill in state waters—a decision received after X389 was already at sea—meaning that we could not sample at some young, science-critical reef sites as originally planned.

Consequently, we pivoted our approach to add more sites in federal waters where we could sample other young reef sequences and to drill transects of shorter, but high-quality, cores to capture small sea level oscillations. Since the research cruise, expedition members have sought to redouble community engagement efforts to redress the offenses and concerns caused by the expedition.

Ancient Anatomy Lessons Fig. 3. Line scan images of two core sections show shallow, in situ reef frameworks characterized by branching Porites coral with well-developed encrusting coralline algae, vermetid gastropods, and microbialite deposits. These cores were collected from the same H2 reef terrace but on opposite sides of Hawai‘i, (a) one near Kawaihae on the leeward, dry side and (b) one near Hilo on the windward, wet side; they are indicative of rapid reef accretion in response to sea level rise and differing riverine inputs. Credit: Adapted from Webster et al. [2025], CC BY 4.0

Analysis of the hundreds of meters of core collected during X389 will reveal, for the first time, the complex internal anatomy and composition of Hawai‘i’s extensive reef packages through the past half million years. Preliminary visual observations have already offered glimpses of exquisite new details, including drowning reef sequences formed during the terminations of glacial periods [Webster et al., 2025]. The building blocks of these drowning reefs include branching, columnar, and massive shallow corals; several types of microbialite; thick crustose coralline algae (Figure 3); lithified and unlithified sediments; and a diversity of volcanic flows and associated sediments.

Observations so far also suggest that our sampling captured distinct shallow, intermediate, and deep reef communities and depositional settings, as well as the first evidence of major lithologic boundaries indicating repeated reef initiation and demise, as predicted by models and previous seafloor observations [Webster et al., 2009] (Figure 2). Furthermore, substantial differences in sedimentary contributions to the reefs between the dry and wet sides of Hawai‘i highlight that variations in precipitation, sediments, and nutrient input might influence reef evolution (Figure 3).

Fig. 4. A suite of nondestructive analytical techniques from across the electromagnetic spectrum was used to investigate fossil coral reef cores collected during X389. Shown here are representative high-resolution images of a robust branching Porites coral and other components from the same core from the H2 reef terrace (dated to between MIS7 and MIS6). The images include (a) a line scan image, (b) an X-ray computed tomography image showing 3D density changes, and hyperspectral images providing mineralogic information such as the (c) aragonite index, (d) calcite index, and (e) minimum wavelength mapping. Credit: Adapted from Webster et al. [2025], CC BY 4.0

Early analyses of the cores have been done using a suite of nondestructive imaging techniques (Figure 4). X-ray computed tomography is providing 3D reconstructions of massive Porites coral specimens, which often provide accurate records of past ocean conditions. In addition, traditional high-resolution line scans integrated with high-resolution hyperspectral scanning of the cores are revealing carbonate and other minerals (e.g., aragonite, calcite, clay, and iron), helping to guide sampling and more detailed analyses of the cores.

Windows into the Past and Future

The material recovered during X389 is between 10,000 and 500,000 years old and includes hundreds of well-preserved samples. These samples will be used to reconstruct the first absolute dating of sea level changes during portions of this time window. Putting absolute dates to these changes will have profound implications for testing theories about the drivers and triggers of past glacial-interglacial cycles and for validating climate and ice sheet models that are critically important for predicting sea level changes resulting from current and future global warming.

Further, the X389 cores include more than 300 Porites coral specimens with annual banding that will provide the first estimates of seasonal to millennial paleoclimate variability in the region. Geochemical analyses can be used to estimate monthly oceanographic variability with respect to temperature, precipitation, nutrient dynamics, carbon chemistry, and pH.

Assessing the nature of variability at different temporal scales will help answer critical questions. For example, were the occurrence and seasonality of extreme climate events in the past dependent on the background average climate state at times when global temperature, Pacific storm tracks positions, solar insolation, and atmospheric CO2 levels were different? The state dependency of high-frequency temperature and hydroclimate variability is a key question today as Earth warms.

The sequences of reef lithologies recovered during X389, including volcanic flows and the diverse variety and shapes of reef-building organisms, will be interpreted to reveal a story of ecosystem response to geological processes and paleoclimatic variations in sea level and oceanographic conditions. This interpretation will inform broader understanding of the factors that control reef growth, reef health, and coastal resilience in subsiding island settings in the face of future changes in hydroclimate, ocean temperature, nutrient availability, sediment supply, and ocean pH.

The X389 science party is working together to continue studying the collected cores in greater detail to address the project’s scientific goals. And we welcome contributions from external scientists as well: Careful sampling of the cores has left much of the material intact, and as of late February 2025, anyone can request X389 samples from the IODP core repository at Texas A&M University. With concerted and collaborative efforts, we can continue the flexible and inclusive approach of IODP—even as the Sun sets over its current phase—to advance knowledge of the paleoclimate over the past 500,000 years and understanding of what conditions Earth may experience in the future.

Acknowledgments

We thank the entire IODP 389 Expedition Science Party, ECORD Science Operator (ESO) support staff, Benthic drilling team, MMA surveyors, and the captain and crew of the MMA Valour for their outstanding work on the offshore and onshore phases of the expedition. IODP Expedition 389 was supported by funding from the various national funding agencies of the participating IODP countries.

References

Elderfield, H., et al. (2012), Evolution of ocean temperature and ice volume through the mid-Pleistocene climate transition, Science, 337(6095), 704–709, https://doi.org/10.1126/science.1221294.

Lambeck, K., et al. (2014), Sea level and global ice volumes from the Last Glacial Maximum to the Holocene, Proc. Natl. Acad. Sci U. S. A., 111(43) 15,296–15,303, https://doi.org/10.1073/pnas.1411762111.

Rohling, E. J., et al. (2009), Antarctic temperature and global sea level closely coupled over the past five glacial cycles, Nat. Geosci., 2(7), 500–504, https://doi.org/10.1038/ngeo557.

Sanborn, K. L., et al. (2017), New evidence of Hawaiian coral reef drowning in response to meltwater pulse-1A, Quat. Sci. Rev., 175, 60–72, https://doi.org/10.1016/j.quascirev.2017.08.022.

Webster, J. M., et al. (2009), Coral reef evolution on rapidly subsiding margins, Global Planet. Change, 66(1–2), 129–148, https://doi.org/10.1016/j.gloplacha.2008.07.010.

Webster, J. M., et al. (2011), Great Barrier Reef environmental changes, Proc. Integrated Ocean Drill. Program, 325, https://doi.org/10.2204/iodp.proc.325.2011.

Webster, J. M., et al. (2025), Hawaiian drowned reefs, Proc. Int. Ocean Discovery Program, 389, https://doi.org/10.14379/iodp.proc.389.2025.

Author Information

Jody M. Webster (jody.webster@sydney.edu.au), School of Geosciences, Geocoastal Research Group, University of Sydney, Australia; and Christina Ravelo (acr@ucsc.edu), Ocean Sciences Department, Institute of Marine Sciences, University of California, Santa Cruz

Citation: Webster, J. M., and C. Ravelo (2025), Unlocking climate secrets of Hawai‘i’s drowned reefs, Eos, 106, https://doi.org/10.1029/2025EO250135. Published on 11 April 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Lunar Ice Might Be Easier to Reach Than We Thought

EOS - Fri, 04/11/2025 - 13:22

Past lunar missions have detected evidence of large ice deposits in permanently shadowed regions near the Moon’s south pole. Such ice could provide astronauts with drinking water, oxygen, and rocket propellants, reducing the cost of lunar operations.

But new research has found that astronauts might not have to dig very deep or journey especially close to the Moon’s poles to find water ice. A recent study published in Communications Earth and Environment says the critical resource for future lunar explorers might lurk tantalizingly close to the surface on pole-facing slopes at lower latitudes. The Sun shines at a low angle on such regions, which may allow ice to accumulate just centimeters below the surface, where it would be insulated by lunar regolith.

The Moon’s low axial tilt means that craters and low-lying areas near the south pole never see direct sunlight. This lack of sunlight would allow even surface ice deposits to remain frozen for a long time—perhaps billions of years. Because of the likely presence of ice, both NASA and China’s space agency have announced plans to land astronauts near the south pole and eventually establish permanent outposts there.

The Chandrayaan-2 orbiter photographed the Vikram lander from orbit. Credit: Indian Space Research Organisation

Locations farther from the poles “can also become potential locations for future human habitats, with better illumination and smoother topography than the poles. These regions pose less technical challenges for landing and operations.”

“Our study reveals that the poles are not the only options for future exploration,” said K. Durga Prasad, lead author of the report and a planetary scientist at the Physical Research Laboratory in Ahmedabad, India. Locations farther from the poles “can also become potential locations for future human habitats, with better illumination and smoother topography than the poles. These regions pose less technical challenges for landing and operations.”

“This result is very much consistent with both theoretical modeling studies and observations made by Lunar Reconnaissance Orbiter,” said Timothy McClanahan, an emeritus planetary scientist at NASA’s Goddard Space Flight Center who was not involved with the study.

First Measurements Since Apollo

The new lunar temperature data come from Chandra’s Surface Thermophysical Experiment (ChaSTE), an instrument aboard the Vikram lander, which itself was part of India’s Chandrayaan-3 mission. Vikram touched down on 23 August 2023 at 69° south latitude, the most southerly landing site at that time. (Two subsequent landers, both built by the American company Intuitive Machines, landed farther south, but both tipped over on landing and were unable to achieve all of their science goals.)

ChaSTE collected data continuously from 24 August to 2 September, shortly before the Sun set on the solar-powered lander (a lunar day lasts about 29.5 Earth days). The probe penetrated 10 centimeters into the regolith, with temperature sensors spaced at 1-centimeter intervals. The instrument also heated the regolith to measure its thermal conductivity.

ChaSTE provided the first direct subsurface lunar temperature measurements since the Apollo 15 and 17 missions of the early 1970s. The Apollo heat probes drilled deeper than ChaSTE did but provided fewer measurements of the top 10 centimeters. The Apollo sites also were close to the equator, where temperatures are likely to remain too warm for water ice even well below the surface, Prasad said.

An enlarged version of the Pragyan image of Vikram indicates the location of the ChaSTE instrument, which measured thermal conductivity and temperatures, and the Instrument for Lunar Seismic Activity (ILSA). Credit: Indian Space Research Organisation

Vikram landed on the rim of a shallow crater in a Sun-facing area with a 6° slope. ChaSTE and other instruments aboard the lander recorded a peak daytime surface temperature of 355 K (81.85°C). That was higher than expected on the basis of both models and observations by Diviner, an infrared instrument aboard the Lunar Reconnaissance Orbiter that has compiled temperature maps of much of the lunar surface. (Temperatures at the probe’s maximum depth ranged from 55 K to 85 K colder than surface temperatures, depending on the time of day.)

However, the temperature on a flat area just 1 meter from the ChaSTE site peaked at only 332 K (58.85°C), suggesting that a location’s slope could play a significant role in its subsurface temperatures.

The findings “validated the idea that topographic variation, even toward meter scales, has an important impact on locations where we might expect water ice to occur,” McClanahan said.

Taking the Right Angle

Modeling showed that at high latitudes, poleward-angled slopes of 14° or greater could remain cold enough to preserve ice at depths of just a few centimeters. The Sun would hit such tilted regions at a low angle, minimizing heating, and the fine-grained top layer of the regolith would be an efficient thermal blanket, effectively insulating the shallow subsurface.

“Depending on the slope, you can have a lot of temperature variation even in craters as small as a meter. One side might be quite warm, but…you could have conditions that are suitable for water ice on the poleward-facing slope.”

“Depending on the slope, you can have a lot of temperature variation even in craters as small as a meter,” McClanahan said. “One side might be quite warm, but given the low thermal conductivity of the regolith, you could have conditions that are suitable for water ice on the poleward-facing slope.” The slope angle suitable for hosting ice increases as you move farther from the pole, he added.

The Vikram team is continuing to analyze the ChaSTE observations to learn more about the thermal characteristics of the landing site and of high lunar latitudes in general, Prasad said. In addition, because temperatures are important for any lunar lander, “future missions will definitely carry similar instruments that will also help substantiate our results,” he said.

—Damond Benningfield, Science Writer

Citation: Benningfield, D. (2025), Lunar ice might be easier to reach than we thought, Eos, 106, https://doi.org/10.1029/2025EO250136. Published on 11 April 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Deflected Dikes Perturb the Plumbing System

EOS - Fri, 04/11/2025 - 12:00
Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: AGU Advances

Magma transport involves interactions of rocks and volatiles in their solid, fluid, and gas phases that must be captured by physical models across a vast range of scales. What complicates matters further is that eruptions respond to heterogeneous and time-variable source conditions modulated by a crust that experiences hysteresis due to its volcano-tectonic history. Any efforts of interpreting signals such as the multi-decadal unrest at the Campi Flegrei, Italy volcanic fields thus must find the balance between honoring the regional specifics and fundamental volcano dynamics.

Numerical scenario computation illustrating how dike populations may respond to the large-scale caldera stress field. Credit: Buono et al. [2025], Figure 7l

Buono et al. [2025] present a sweeping review that seeks to integrate rock physics, seismic tomography, and mechanical modeling into a systems-level understanding of the Campi Flegrei setting. It appears that the combination of caldera geometry and lithology leads to a crustal stress state that affects volcanic dike ascent which in turn may feed back into crustal deformation behavior. This suggests the importance of a resulting weak crustal layer for subsequent magma and gas pathways and perhaps an evolutionary scenario for similar volcanic centers. While the modeling is suggestive, there are a range of interactions and features left to be explored. However, the range of geophysical and geological constraints that are accessible in well instrumented volcanic systems points toward the potential of future, fully integrated models that might be capable of assimilating time dependent observations for improved, physics-based forecasting of volcanic hazards.

Citation: Buono, G., Maccaferri, F., Pappalardo, L., Tramelli, A., Caliro, S., Chiodini, G., et al. (2025). Weak crust owing past magmatic intrusions beneath Campi Flegrei identified: The engine for bradyseismic movements? AGU Advances, 6, e2024AV001611. https://doi.org/10.1029/2024AV001611

—Thorsten Becker, Editor, AGU Advances

Text © 2024. The authors. CC BY-NC-ND 3.0
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Industrial carbon producers contribute significantly to sea level rise, modeling study finds

Phys.org: Earth science - Fri, 04/11/2025 - 10:50
Research led by the Union of Concerned Scientists reports that emissions from the world's largest fossil fuel and cement companies have contributed significantly to both present-day and long-term sea level rise. Products from 122 major producers have contributed up to 37% of the rise in global sea level observed through 2022 and may account for an additional 0.26 to 0.55 meters by 2300.

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