Bayesian hierarchical model for bias-correcting climate models
Jeremy Carter, Erick A. Chacón-Montalván, and Amber Leeson
Geosci. Model Dev., 17, 5733–5757, https://doi.org/10.5194/gmd-17-5733-2024, 2024
Climate models are essential tools in the study of climate change and its wide-ranging impacts on life on Earth. However, the output is often afflicted with some bias. In this paper, a novel model is developed to predict and correct bias in the output of climate models. The model captures uncertainty in the correction and explicitly models underlying spatial correlation between points. These features are of key importance for climate change impact assessments and resulting decision-making.
A new 3D full-Stokes calving algorithm within Elmer/Ice (v9.0)
Iain Wheel, Douglas I. Benn, Anna J. Crawford, Joe Todd, and Thomas Zwinger
Geosci. Model Dev., 17, 5759–5777, https://doi.org/10.5194/gmd-17-5759-2024, 2024
Calving, the detachment of large icebergs from glaciers, is one of the largest uncertainties in future sea level rise projections. This process is poorly understood, and there is an absence of detailed models capable of simulating calving. A new 3D calving model has been developed to better understand calving at glaciers where detailed modelling was previously limited. Importantly, the new model is very flexible. By allowing for unrestricted calving geometries, it can be applied at any location.
Characterization of a new Teflon chamber and on-line analysis of isomeric multifunctional photooxidation products
Finja Löher, Esther Borrás, Amalia Muñoz, and Anke Christine Nölscher
Atmos. Meas. Tech., 17, 4553–4579, https://doi.org/10.5194/amt-17-4553-2024, 2024
We constructed and characterized a new indoor Teflon atmospheric simulation chamber. We evaluated wall losses, photolysis rates, and secondary reactions of multifunctional photooxidation products in the chamber. To measure these products on-line, we combined chromatographic and mass spectrometric analyses to obtain both isomeric information and a high temporal resolution. For method validation, we studied the formation yields of the main ring-retaining products of toluene.
An international research team—including scientists from the University of East Anglia (UEA)—deployed an unmanned submersible beneath the Dotson Ice Shelf in West Antarctica. The underwater vehicle, "Ran," was programmed to dive into the cavity of the 350 meter thick ice shelf and scan the ice above it with an advanced sonar.
Abstract
Based on multi-model large-ensemble experiments provided by Polar Amplification Model Intercomparison Project (PAMIP), we investigate the influence of the projected sea ice loss in Barents-Kara Seas (BKS) and Sea of Okhotsk (SOK) on the Arctic stratospheric polar vortex (SPV). Results show that future BKS sea ice reduction leads to a weakened SPV during November-February by enhancing the upward-propagating planetary wave 1, which is more pronounced during Quasi-Biennial Oscillation (QBO) easterly than westerly phase. Through weakening the upward-propagating planetary wave 2, future SOK sea ice reduction is favorable for a strengthened SPV during January-April. Inter-model spread in the magnitudes of SPV responses to BKS sea ice reduction can be largely explained by the divergent planetary wave responses, but less so for SOK sea ice reduction. Results from a linearized baroclinic model further validate the importance of the planetary-scale wave responses in explaining the differing SPV responses to sea-ice loss over the two regions.
Abstract
In order to identify relations between mechanical behavior, deformation mechanisms, microstructural properties, and H2O distribution, Tana-quartzite samples with added H2O ranging from 0 to 0.5 wt.% were deformed by axial shortening at constant displacement rates, at 900°C and 1 GPa, reaching up to ∼30% bulk strain. Samples with lower quantities of added H2O (0.1 and 0.2 wt.%) were in average ∼30 MPa weaker than the as-is samples with no added H2O. In contrast, samples with more than 0.2 wt.% added H2O revealed more variable mechanical behavior, showing either weaker or stronger trend. The weaker samples showed strain localization in their central parts in the vicinity of the thermocouple, that is, the hottest parts of the samples, whereas the stronger samples showed localization in their upper, slightly colder parts. Bulk deformation is accommodated by crystal plasticity and dissolution-precipitation processes. Distribution of H2O in our samples revealed systematic decrease of H2O content in the interiors of original grains, caused by increasing strain and H2O draining into grain boundary regions. With increasing content of added H2O, the quartz recrystallization gradually changes from subgrain-rotation-dominated to crack-induced nucleation, along with increasing quantity of melt/fluid pockets. The unexpected strain localization in the upper parts of stronger samples most likely results from mode-1-cracking that led to drainage of grain boundaries (GB) due to the crack dilatancy effect, and inhibited dissolution-precipitation in the hottest part of the samples next to the thermocouple. The locus of deformation is then shifted to colder regions where more H2O is available along GB.
The Southern Ocean is wild and dynamic. It experiences Earth's strongest winds and largest waves. It is home to city-sized icebergs and the biggest ocean current on the globe, as well as tiny turbulent flows that fit inside a teacup.
It's time to take a thorough, more serious look at using geoengineering to protect the planet's icesheets, according to a group of scientists who have released a new report examining the issue. Glacial geoengineering is an emerging field of study that holds some hope for Earth's diminishing glaciers and ice sheets.
Space hurricanes are a recently discovered geomagnetic phenomenon in which plasma interacts with Earth's magnetosphere, the area of space dominated by Earth's magnetic field. Spiral arms of plasma, hundreds of kilometers long, stretch across the sky and turn clockwise around a calm "eye" in the center—forming aurorae shaped much like the hurricanes that occur closer to Earth's surface in the troposphere. Electrons from space rain down into Earth's upper atmosphere, where they have the potential to disrupt satellite communications.
Scientists from UC San Diego's Scripps Institution of Oceanography have detected geochemical signatures of magma pooling and melting beneath the subsurface during the "Fagradalsfjall Fires," that began on Iceland's Reykjanes peninsula in 2021.
Scientific studies have filled the pages of AGU journals for more than a century. These articles reveal how the study of geophysics has evolved alongside technology and societal interests and they tell the story of our expanding knowledge of Earth and space science.
Abstract
We exploit nonlinear elastodynamic properties of fractured rock to probe the micro-scale mechanics of fractures and understand the relation between fluid transport and fracture aperture under dynamic stressing. Experiments were conducted on rough, tensile-fractured Westerly granite subject to triaxial stresses. We measure fracture permeability for steady-state fluid flow with deionized water. Pore pressure oscillations are applied at amplitudes ranging from 0.2 to 1 MPa at 1 Hz frequency. During dynamic stressing we transmit ultrasonic signals through the fracture using an array of piezoelectric transducers (PZTs) to monitor evolution of interface properties. We examine the influence of fracture aperture and contact area by conducting measurements at effective normal stresses of 10–20 MPa. Additionally, the evolution of contact area with stress is characterized using pressure sensitive film. These experiments are conducted separately with the same fracture and map contact area at stresses from 9 to 21 MPa. The measurements are a proxy for “true” contact area for the fracture surface and we relate them to elastic properties using the calculated PZT sensor footprints via numerical modeling of Fresnel zones. We compare the elastodynamic response of the fracture using the stress-induced changes in ultrasonic wave velocities for transmitter-receiver pairs to image spatial variations in contact properties. We show that nonlinear elasticity and permeability enhancement decrease with increasing normal stress. Additionally, post-oscillation wave velocity and permeability exhibit quick recoveries toward pre-oscillation values. Estimates of fracture contact area (global and local) demonstrate that the elastodynamic and permeability responses are dominated by fracture topology.
A new study has revealed that changes in the ocean floor impact currents, giving new insight into the deep-sea pathways of nutrients and pollutants.
Abstract
The wintertime North Atlantic Oscillation (NAO) and East Atlantic Pattern (EA) are the two leading modes of North Atlantic pressure variability and have a substantial impact on winter weather in Europe. The year-to-year contributions to multi-model seasonal forecast skill in the Copernicus C3S ensemble of seven prediction systems are assessed for the wintertime NAO and EA, and well-forecast and poorly-forecast years are identified. Years with high NAO predictability are associated with substantial tropical forcing, generally from the El Niño Southern Oscillation (ENSO), while poor forecasts of the NAO occur when ENSO forcing is weak. Well-forecast EA winters also generally occurred when there was substantial tropical forcing, although the relationship was less robust than for the NAO. These results support previous findings of the impacts of tropical forcing on the North Atlantic and show this is important from a multi-model seasonal forecasting perspective.
Abstract
Bristlecone pine (Pinus longaeva) (PILO) trees exhibit exceptional longevity. Their tree-ring width (TRW) series offer valuable insights into climatic variability. Maximum latewood density (MXD) typically correlates better with temperature variations than TRW, yet PILO MXD records are non-existent due to methodological challenges related to tree-ring structure. Here, we used an X-ray Computed Tomography (X-ray CT) toolchain on 51 PILO cores from the California White Mountains to build a chronology that correlates significantly (r = 0.66, p < 0.01) with warm-season (March-September) temperature over a large spatial extent. This led to the first X-ray CT-based temperature reconstruction (1625–2005 CE). Good reconstruction skill (RE = 0.51, CE = 0.32) shows that extending MXD records across the full length of the PILO archive could yield a robust warm-season temperature proxy for the American Southwest over millennia. This breakthrough opens avenues for measuring MXD in other challenging conifers, increasing our understanding of past climate further, particularly in lower latitudes.
Heavy rain and flooding in Brazil in November could tell forecasters whether December, January and February in Britain will be cold and dry or mild and wet.
Climate has an important role to play in viticulture (wine production) due to the impacts on grape harvest from variability in parameters such as temperature, precipitation and aridity. Warmer and drier climates with long growing seasons benefit grapevine growth, although beyond a tipping point, it can be damaging in climates akin to the Mediterranean. The Moselle Valley, spanning north-eastern France, south-western Germany, and eastern Luxembourg, has historically been and continues to be a major source of wine production in climatically-sensitive central and southern Europe.
Abstract
This study presents the implementation and evaluation of scale-dependent localization (SDL) in the hurricane analysis and forecast system 4D Ensemble Variational (4DEnVar) Data Assimilation (DA) system. The SDL capability is compared with the traditional Single-Scale Localization (SSL) method to assess its benefits and necessity for hurricane prediction. The experiments focus on Hurricane Laura (2020) and involve single observation experiments as well as real observation DA cycling experiments. The results indicate that the SDL experiment, which incorporates the Fast Almost Gaussian Filtering approach for scale decomposition, consistently outperforms the corresponding SSL configurations in almost all aspects. Further diagnostics show that due to its multiscale nature, the SDL approach demonstrates better track prediction over small-scale SSL due to improved environmental analysis and better analyzed vortex position and structure, and superior intensity prediction during the rapid intensification over both the large-scale SSL and the small-scale SSL owing to enhanced inner-core thermodynamic analysis.
Early in 2024, inside the Arctic Circle—thousands of miles from the Naval Postgraduate School (NPS) campus in Monterey—a small team of students and faculty undertook a critical scientific research expedition, working with the Undersea Warfighting Development Center's Arctic Submarine Laboratory (ASL) at the biennial Operation Ice Camp.
Abstract
We simulate the Madden-Julian oscillation (MJO) over an aquaplanet with uniform surface temperature using the multiscale modeling framework (MMF) configuration of the Energy Exascale Earth System Model (E3SM-MMF). The model produces MJO-like features that have a similar spatial structure and propagation behavior to the observed MJO. To explore the processes involved in the propagation and maintenance of these MJO-like features, we perform a vertically resolved moist static energy (MSE) analysis for the MJO (Yao et al., 2022, https://doi.org/10.1175/jas-d-20-0254.1). Unlike the column-integrated MSE analysis, our method emphasizes the local production of MSE variance and quantifies how individual physical processes amplify and propagate the MJO's characteristic vertical structure. We find that radiation, convection, and boundary layer (BL) processes all contribute to maintaining the MJO, balanced by the large-scale MSE transport. Furthermore, large-scale dynamics, convection, and BL processes all contribute to the propagation of the MJO, while radiation slows the propagation. Additionally, we perform mechanism-denial experiments to examine the role of radiation and associated feedbacks in simulating the MJO. We find that the MJO can still self-emerge and maintain its characteristic structures without radiative feedbacks. This study highlights the role of convective MSE transport in the MJO dynamics, which was overlooked in the column-integrated MSE analysis.
