Glacier flow is typically modeled using a power law rheology known as the Glen–Nye flow law, with the power n assumed to be 3. However, recent research and past observations suggest that n=4 may better represent ice flow in some locations. We lack a quantitative understanding of how much this exponent affects ice loss projections, and its significance relative to other sources of uncertainty. Here, we test the effect of n=3 versus n=4 in a series of 300-year forward simulations of the Amundsen Sea Embayment, West Antarctica. We find that in periods of rapid grounding line retreat, uncertainty in n leads to a larger spread in ice loss projections than the spread due to uncertainty in climate forcing. The spatial sensitivity of n is generally proportional to the change in strain rates, so we expect regions undergoing more moderate dynamic change to be less sensitive to n.

A document by Liwei Cao. Click on the document to view its contents.

The concept of optimality in geostatistical inversion is traditionally rooted in a Euclidean framework, which often oversimplifies complex spatial relationships in geological structures, potentially leading to suboptimal representations of subsurface properties. This study challenges this conventional approach by introducing manifold embedding, a method that incorporates non-Euclidean geometries to better capture the complex and non-stationary nature of geological structures. Through the application of Kalman filtering (KF) and geostatistical principal component adaptation evolution strategy (GPCA-ES), we explore how different geometric frameworks influence the outcomes of hydraulic conductivity estimations in a synthetic aquifer. Our results demonstrate that while Euclidean-based methods may provide a single “optimal” solution, they do not necessarily yield the most geologically accurate models. By incorporating manifold geometries, we reveal a broader range of plausible subsurface interpretations, all of which produce similar hydraulic responses at observation points. This finding highlights the limitations of relying solely on Euclidean assumptions and challenges the conventional notion of a unique optimal solution in hydrogeological inverse problems. The study underscores the importance of adopting a more comprehensive geometric perspective in hydrogeological modeling, offering a pathway to more geologically meaningful and potentially more reliable subsurface characterizations. These findings advocate for a fundamental shift in the approach to geostatistical inversion, emphasizing the need to move beyond traditional optimality criteria and toward a more nuanced understanding of subsurface environments that acknowledges the inherent complexity and non-uniqueness of geological structures.

Abstract The global gravitational gradient field has not been observed since the decommission of GOCE in 2013. Based on the foundational work of Peidou and Pagiatakis (2019), we advance the concept of GRACE gradiometer mode (GM) for the purpose of using GRACE, GRACE-FO and future gravity space missions as ‘gradiometer missions’. Certainly, the GRACE missions have never carried a gradiometer, it is only the concept of GM that creates a fictitious gradiometer system very similar to GOCE, only the GRACE ‘gradiometers’ have long and variable baselines, an unprecedented paradigm for space-based gravitational gradiometry that extends the bandwidth of the gradient solution. In this contribution, we develop a new configuration for GM that views an individual satellite as the ‘gradiometer’, in order to directly use Level 1A accelerometer measurements in a 10 Hz sampling interval. We apply the new method in geodynamically active regions around the globe, and we demonstrate that using GRACE-C as a ‘gradiometer’ in the single-satellite gradiometer mode (SS-GM) produces higher-fidelity gravitational gradient estimates, clearly delineating tectonic plate boundaries and subduction zones in the Himalayas and North Africa regions, the Aleutian trench, the Java trench, and the Peru-Chile trench. Over Canada, we see the delineation of the Canadian shield, and the effect of glacial isostatic adjustment (GIA) is apparent. We also observe well-known signals resembling terrestrial water storage (TWS) changes in Africa, among others, demonstrating the usefulness of the GM for a wide variety of geoscience applications.

On 8 April 2024, a rare total solar eclipse (TSE) passed over western New York State (NYS), the first since 1925 and the last one until 2079. The NYS Mesonet (NYSM) consisting of 126 weather stations with 55 on the totality path provides unprecedented surface, profile, and flux data and camera images during the TSE. Here we use NYSM observations to characterize the TSE’s impacts at the surface, in the planetary boundary layer (PBL), and on surface fluxes and CO2 concentrations. The TSE-induced surface cooling occurs 20 minutes after the totality and is 2.75°C on average with a maximum value of 6.9°C. It results in night-like surface inversion, calm winds, and reduced vertical motion and mixing, which leads to the shallowing of the PBL and its moistening due to reduced vertical mixing. Surface sensible, latent and ground heat fluxes all decrease whereas near-surface CO2 concentration rises as photosynthesis slows down.

A document by Sushel Unninayar. Click on the document to view its contents.

The ACES-II sounding rocket mission launched two payloads from Andøya Rocket Range into a post-dusk discrete auroral arc and observed field-aligned electron dispersions near inverted-V precipitation. Five repetitive suprathermal electron bursts (STEBs) associated with low frequency (< 8 Hz) Earth-ward traveling Alfvén waves are observed at 400 km altitude. The electron bursts occur both coincident and outside inverted-V electrons, with those nearest to inverted-V precipitation displaying higher peak energy and differential flux values than events further away. We interpret the events as wave-particle acceleration via inertial Alfvén waves along near-Earth field lines and employ time-of-flight methods to gauge source altitudes. We show the differences in STEB behavior are better explained by changes in the resonant source population and not from significant variation in Alfvén wave parameters, a result that agrees with previous simulated predictions.

Peatland permafrost ecosystems include culturally and ecologically important habitat for plants and wildlife. Widespread degradation of palsas and peat plateaus suggests vulnerability of these landforms to climate warming, but ecosystem changes, including landscape greening due to shrub expansion and related changes in snow distribution, are also expected to impact permafrost persistence. In this study, the Northern Ecosystem Soil Temperature model is used to simulate future ground temperature trajectories for nine peatland permafrost landforms along the Labrador Sea coastline. Ground temperatures are modeled for each site from 2024 to 2100 under six scenarios, which account for differences in future land cover, snow, and climate warming (RCP4.5). All scenarios incorporating a change in ecosystem characteristics or climate result in total loss of permafrost at all sites by 2100, with some sites experiencing loss of permafrost by 2036. Although permafrost thaw occurs at all sites under most scenarios, the study sites exhibit wide variations in thaw rates due to differences in latitude, geomorphological characteristics, and initial permafrost thicknesses. While most sites experience active layer thickening, four of the nine sites also see the development of supra-permafrost taliks, but this occurs almost exclusively in the four scenarios that incorporate ecosystem change. The development of taliks under these scenarios and the earlier loss of permafrost suggest that peatland permafrost in coastal Labrador may be more sensitive to ecosystem change than climate warming alone. These results provide important insights into the future evolution and climate sensitivity of permafrost peatlands in the discontinuous permafrost zone.

Representing glacial-interglacial changes in ocean carbon sequestration remains a major challenge for Earth system models (ESMs). Uncertainties in ocean circulation and biological carbon export are essential causes for model-proxy data mismatch. We quantify the impact of these factors by calibrating the Max Planck Institute-ESM. A shallower and weaker glacial Atlantic meridional overturning circulation (AMOC) than the present day, achieved by decreasing background vertical diffusivity, enables capturing the main features in observed δ13C, 14C and CO32-. Additionally, a new prognostic computation of marine aggregate sinking speeds enhances organic matter export efficiency in high latitudes. Together, the shallower AMOC and a comprehensive sinking scheme substantially improve the model-data comparison and carbon storage in the glacial Atlantic, but not in the Pacific and Indian oceans owing to low organic matter remineralisation. Our results yield that representing the glacial-interglacial ocean carbon storage in ESMs requires both constraining ocean circulation and improved biogeochemical processes.

Comprehensive climate models fail to capture historical sea surface temperature (SST) trends in the Southern Ocean, where multidecadal cooling occurred despite global warming. Efforts to explain this discrepancy have invoked underestimated mixed-layer freshening, which produces cold SST anomalies through enhanced stratification. However, single-model freshwater forcing experiments have produced a wide range of SST responses, and the relative importance of different freshwater sources remains unclear. To address these ambiguities, this study quantifies linear SST response functions for standardized freshwater flux increases across CMIP6 models and estimates the 1990-2021 SST cooling from observed freshwater inputs. We attribute the lack of SST cooling trends in CMIP6 to missing Antarctic Ice Sheet meltwater and underestimated precipitation increases, each producing similar 1990-2021 cooling tendencies. Adjusting SST trends for these missing sources improves model-observation agreement, quantifying, for the first time, the impact of missing freshwater forcing on Southern Ocean SST trends across a multi-model ensemble.

Low-level mixed-phase clouds occur frequently and persistently in the central Arctic, and thus play a key role in climate feedback mechanisms, air mass transformations, and sea ice melt. Turbulent entrainment at cloud top driven by radiative cooling modulates these clouds by affecting the boundary-layer heat budget. However, reliable measurements of this small-scale process are scarce. This study presents new insights into entrainment in radiatively-driven cloudy mixed-layers at high latitudes based on a library of daily large-eddy simulations covering the full MOSAiC drift. The simulations are based on measurements, cover a periodic and homogeneously-forced small domain representing conditions observed at the Polarstern Research Vessel, and resolve Arctic turbulence and clouds to a high degree. Approximately 1 out of 3 simulated days contain cloud mass in liquid phase. Drift-average heat budget analyses show that the full column is roughly in radiative-advective equilibrium. In contrast, the cloudy boundary layer is not, being dominated by cloud top cooling. Warming by top-entrainment only partially counters this cooling, at efficiencies of about 30 %. Such efficiencies are much lower compared to previous findings for subtropical warm marine stratocumulus. Interestingly, a few outlying MOSAiC cases show similarly high efficiencies. Analysis of turbulence energetics reveals that high entrainment efficiency can be achieved in two ways: surface coupling and strong local wind shear. The former explains the high efficiencies in the subtropics, while the latter drives the highest efficiencies encountered during MOSAiC. In general, these findings emphasize the important role played by wind shear in boosting entrainment efficiency.

Jacob M Muinde

Lagrangian simulations based on 18 years (2002-2019) of high-resolution eddy-resolving thermohaline and three-dimensional velocity fields allow to revisit the fate and thermohaline changes of the upper-ocean Antarctic Circumpolar Current (ACC) waters that enter directly the South Atlantic Ocean basin. An advection-diffusion scheme applied to the climatological annual-mean and daily-mean fields allows accurate estimations of the mean pathways and seasonal variability, as well as the recirculation volume transports, times and depths in the South Atlantic Subtropical Gyre (SASG). On average, 94.8 Sv of the upper-ocean waters (up to the 28.00 kg m-3) that cross the Drake Passage remain in the ACC, while 15.1 Sv join the SASG. Among those entering the SASG, 10.3 Sv reach the North Brazil Current and contribute to the Atlantic Meridional Overturning Circulation returning limb, this contribution being substantially higher than previously stated. All these Drake Passage upper-ocean waters undergo substantial water mass transformations as they reach the eastern SASG, from intermediate-deep to surface layers (6.7 Sv) and increase their heat transport in 0.46 PW and their salt transport in 8.5 × 106 kg s-1, but remain largely unchanged in their westward drift to the western boundary at 21°S. Most waters within the SASG (78.1%) recirculate one single loop, taking an average of 25.2 ± 14.3 years, although some of them complete as many as three loops before exiting. Regarding seasonality, the transit times and transport fraction of the upper-ocean Drake waters, into the SASG show higher variability than those remaining in the ACC path.

Atmospheric photochemistry is essential for simulating atmospheric composition, impacting air quality and climate change. However, conventional numerical schemes of photochemistry within atmospheric models are computationally expensive, leading to simplifications or omissions of critical processes in weather and climate models. Previous attempts to leverage artificial intelligence (AI) scheme to reduce computational costs have faced obstacles such as the curse of dimensionality and error propagation, and most have been limited to box models without coupling into numerical models. Here, we develop an innovative AI PhotoChemistry (AIPC) scheme coupled into an atmospheric model (WRF-Chem). With Multi-Head Self-Attention algorithm (MHSA), we simulate 74 chemical species and 229 reactions following the SAPRC-99 mechanism. This marks the first implementation of a sophisticated photochemical mechanism within one unified AI model, enabling fast, accurate, and stable simulations without needing individual AI model for each species as previous works. Comparative analysis reveals that the AIPC scheme outperforms previous AI schemes using Multi-Layer Perceptron and Residual Neural Network algorithms, offering superior accuracy and computational efficiency. Moreover, fine-tuning learning rate and broadening network width within the MHSA algorithm are more effective for improving the AIPC scheme’s performance than adjusting batch size or increasing network depth. When coupling AIPC into WRF-Chem, this hybrid model with both physics and AI schemes reproduces the spatiotemporal distributions of various species on monthly time scale, and achieves substantial speed enhancement with ~8 times faster than conventional scheme. This advancement lays the groundwork for future development of weather and climate models with sophisticated chemical processes.

Snow avalanches pose a significant threat to settlements and their inhabitants. Consequently, hazard maps are a valuable tool for mitigating their impact. Dynamic models have been used to visualize areas affected by avalanches; however, these models require uncertain inputs. This study develops probabilistic hazard maps by quantifying uncertain input variables through probability density functions. These maps represent the probability of model outputs, such as maximum flow thickness, exceeding specific thresholds, allowing for more quantitative hazard assessments. Three uncertainty quantification methods—Monte Carlo, Latin hypercube sampling, and polynomial chaos quadrature (PCQ)—are employed to generate probabilistic hazard maps for snow avalanches. These maps are compared with a reference hazard map created using parameter sets that cover the entire parameter space. Among the three methods, PCQ yields the most accurate results for a given number of simulations, assuming a uniform distribution for each input. The optimal PCQ settings, which deliver superior results with fewer simulations, are then determined. Additionally, a PCQ application is proposed to generate hazard maps based on non-uniform input distributions without requiring extra simulations. This approach reduces the computational cost associated with creating hazard maps for non-uniform distributions if PCQ has already been applied to a uniform case. The application generates two types of probabilistic hazard maps: one considering all potential parameter ranges during the snow season using uniform distributions, and another reflecting non-uniform distributions that account for uncertainty near-term real-world snow cover conditions.

The eastern tropical North Pacific oxygen deficient zone (ETNP-ODZ) exhibits a distinct physical and biological environment compared to other oxygenated water columns, leading to a unique scenario of particulate organic matter (POM) production and vertical transport. To elucidate these biological pump processes, we present the first comparison of δ¹⁵N values of nitrate, phenylalanine (Phe), and glutamic acid (Glu) within two distinct size fractions of particles collected along a productivity gradient in the ETNP-ODZ. Low δ¹⁵NPhe and δ¹⁵NGlu values in both particle pools at the secondary chlorophyll maximum (SCM), compared to the ambient δ¹⁵N-NO₃-, suggest the presence of recycled N-utilizing primary producers distinct from those at the primary chlorophyll maximum and their contribution to export. We observed reduced ¹⁵N enrichment of Phe in suspended particles and a narrower δ¹⁵NPhe disparity between the two particle size fractions compared to the results from oxic waters, likely due to slower microbial remineralization of suspended particles. Unique δ¹⁵NPhe and δ¹⁵NGlu signatures of particles were found at the lower oxycline, potentially attributable to chemoautotrophic production and zooplankton mediation. These findings underscore the need for further investigations targeting particles generated at the SCM, their subsequent alteration by zooplankton, and the new production by chemoautotrophs. This will allow for a better evaluation of the efficiency of the biological pump in the expanding ODZs.

This report highlights the complex interplay between cardiac func8on, metabolic disorders, and the impact of Oshtoran Syndrome on overall health. Par8cular emphasis is placed on the implica8ons of a le? ventricular ejec8on frac8on (LV-EF) decline, PDH cytopathy, and the resultant metabolic dysregula8on. Addi8onally, the cri8cal role of catecholamine suppression in preven8ng poten8ally life-threatening episodes is discussed. Introduc/on: Oshtoran Syndrome (H63D Syndrome Type-3) presents a mul8faceted clinical challenge, characterized by both cardiac and metabolic complica8ons. This report examines the deteriora8on in cardiac func8on, the metabolic impact of PDH cytopathy, and the systemic effects observed in a pa8ent with this syndrome, along with the essen8al role of catecholamine suppression. 1,4,5 Cardiac issues: Le? Ventricular Ejec8on Frac8on (LV-EF): The pa8ent's LV-EF has decreased from 63% to 49%, indica8ng a significant impairment in the heart's ability to pump blood and oxygen efficiently. This decline reflects a compromised cardiac func8on, likely contribu8ng to systemic hypoperfusion and metabolic stress. 9,10,11,12

Ocean alkalinity enhancement (OAE) can potentially remove gigatons of CO2 from the atmosphere for durable storage in the ocean. Before implementing OAE at climate-relevant scales, questions about its safety and verifiability must be addressed. Operational deployment poses a dilemma between pursuing large detectability, essential for effective monitoring, reporting, and verification (MRV), and ensuring environmental safety and satisfying regulatory requirements. In this study, we present a computationally efficient approach, based on a high-resolution, coupled circulation-dissolution model of Halifax Harbour, to simulating the addition, transportation, dissolution, and sinking of various theoretical alkaline feedstocks for different dosages, seasons, and addition sites. Detectability and exposure risk of OAE are quantified and an approach for optimizing OAE deployment is demonstrated. Mean residence times (MRT) are calculated for different subregions and seasons. Results show that for a given amount of feedstock, summer is more favourable from the perspective of detectability but also creates higher exposure risks than other seasons because of a longer MRT. The exposure risk can be mitigated while maintaining large detectability by choosing optimal feedstocks with different characteristics for different seasons. The exposure risk can also be reduced by spreading alkalinity over multiple addition sites. The optimum allocation, where the largest detectability is sought without violating regulatory requirements, is specific to each season, dosage, and choice of feedstock. OAE deployments should be tailored taking into account local hydrography, season, dosage, and feedstock characteristics. Our approach provides a practical avenue for optimizing deployments.