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Subglacial freshwater discharge from beneath Antarctic glaciers likely has a strong impact on ice shelf basal melting. However, the difficulty in directly observing subglacial flow highlights the importance of modeling these processes. We use an ocean model of the Totten Ice Shelf cavity into which we inject subglacial discharge derived from a hydrology model applied to Aurora Subglacial Basin. Our results show (a) discharge increases melting in the vicinity of the outflow region, which correlates with features observed in surface elevation maps and satellite-derived melt maps, with implications for ice shelf stability; (b) the change in melting is driven by the formation of a buoyant plume rather than the addition of heat; and (c) the buoyant plume originating from subglacial discharge-driven melting is far-reaching. Basal melting induced by subglacial hydrology is thus important for ice shelf stability, but is absent from almost all ice-ocean models.

This presentation was held at the OCEAN:ICE WP3 EO Workshop exploring Antarctic fluxes in observations and climate and ice sheet models. The workshop took place in Copenhagen, Denmark from the 23rd to 24th of May in 2023. Noel Gourmelen delivered thispresentation on May 23rd, 2023 during Session 1of the workshop, Antarctic surface datasets from in-situ and Earth Observations. &nbsp

This presentation was held at the OCEAN:ICE This presentation was held at the OCEAN:ICE WP3 EO Workshop exploring Antarctic fluxes in observations and climate and ice sheet models. The workshop took place in Copenhagen, Denmark from the 23rd to 24th of May in 2023. Benjamin Davison delivered thispresentation on May 23rd, 2023 during Session 1 of the workshop, Antarctic surface datasets from in-situ and Earth Observations. &nbsp

This presentation was held at the OCEAN:ICE WP3 EO Workshop exploring Antarctic fluxes in observations and climate and ice sheet models. The workshop took place in Copenhagen, Denmark from the 23rd to 24th of May in 2023. Katie Lowery delivered this presentation on May 23rd, 2023 during Session 1, Antarctic surface datasets from in-situ and Earth Observations. &nbsp

Funder: Carnegie Trust for the Universities of Scotland; doi: https://doi.org/10.13039/501100000582, Funder: Prince Albert II of Monaco Foundation (Prince Albert II Foundation); doi: https://doi.org/10.13039/501100011592, Funder: Scottish Alliance for Geoscience, Environment and Society (SAGES); doi: https://doi.org/10.13039/100008083, West Antarctica has experienced dramatic ice losses contributing to global sea-level rise in recent decades, particularly from Pine Island and Thwaites glaciers. Although these ice losses manifest an ongoing Marine Ice Sheet Instability, projections of their future rate are confounded by limited observations along West Antarctica's coastal perimeter with respect to how the pace of retreat can be modulated by variations in climate forcing. Here, we derive a comprehensive, 12-year record of glacier retreat around West Antarctica's Pacific-facing margin and compare this dataset to contemporaneous estimates of ice flow, mass loss, the state of the Southern Ocean and the atmosphere. Between 2003 and 2015, rates of glacier retreat and acceleration were extensive along the Bellingshausen Sea coastline, but slowed along the Amundsen Sea. We attribute this to an interdecadal suppression of westerly winds in the Amundsen Sea, which reduced warm water inflow to the Amundsen Sea Embayment. Our results provide direct observations that the pace, magnitude and extent of ice destabilization around West Antarctica vary by location, with the Amundsen Sea response most sensitive to interdecadal atmosphere-ocean variability. Thus, model projections accounting for regionally resolved ice-ocean-atmosphere interactions will be important for predicting accurately the short-term evolution of the Antarctic Ice Sheet., Carnegie Trust for the Universities of Scotland Carnegie PhD Scholarship Scottish Alliance for Geoscience, Environment and Society (SAGES) Prince Albert II of Monaco Foundation NSF Grant 2045075 European Space Agency

Retreating and thinning glaciers are icons of climate change and impact the local hazard situation, regional runoff as well as global sea level. For past reports of the Intergovernmental Panel on Climate Change (IPCC), regional glacier change assessments were challenged by the small number and heterogeneous spatio-temporal distribution of in situ measurement series and uncertain representativeness for the respective mountain range as well as by spatial and temporal limitations and technical challenges of geodetic methods. Towards IPCC SROCC and AR6, there have been considerable improvements with respect to available geodetic datasets. Geodetic volume change assessments for entire mountain ranges have become possible thanks to recently available and comparably accurate digital elevation models (e.g., from ASTER or TanDEM-X). At the same time, new spaceborne altimetry (CryoSat-2, IceSat-2) and gravimetry (GRACE-FO) missions are in orbit and about to release data products to the science community. This opens new opportunities but also comes with new challenges for glacier mass-change assessments.In this presentation, we introduce the Glacier Mass Balance Intercomparison Exercise (GlaMBIE; https://glambie.org) of the European Space Agency, which is building on existing activities and the network of the International Association of Cryospheric Sciences (IACS) working group on Regional Assessments of Glacier Mass Change (RAGMAC) to tackle these challenges in a community effort. We will present our approach to develop a common framework for regional-scale glacier mass-change estimates towards a new data-driven consensus estimate of regional and global mass changes from glaciological, DEM-differencing, altimetric, and gravimetric methods., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Satellite and airborne observations of surface elevation are critical in understanding climatic and glaciological processes and quantifying their impact on changes in ice masses and sea level contribution. With the growing number of dedicated airborne campaigns and experimental and operational satellite missions, the science community has access to unprecedented and ever-increasing data. Combining elevation datasets allows potentially greater spatial-temporal coverage and improved accuracy; however, combining data from different sensor types and acquisition modes is difficult by differences in intrinsic sensor properties and processing methods. This study focuses on the combination of elevation measurements derived from ICESat-2 and Operation IceBridge LIDAR instruments and from CryoSat-2’s novel interferometric radar altimeter over Greenland. We develop a deep neural network based on sub-waveform information from CryoSat-2, elevation differences between radar and LIDAR, and additional inputs representing local geophysical information. A time series of maps are created showing observed LIDAR-radar differences and neural network model predictions. Mean LIDAR vs. interferometric radar adjustments and the broad spatial and temporal trends thereof are recreated by the neural network. The neural network also predicts radar-LIDAR differences with respect to waveform parameters better than a simple linear model; however, point level adjustments and the magnitudes of the spatial and temporal trends are underestimated.

Surface melt over the Antarctic ice shelves is one of the largest uncertainties related to sea level rise over the 21st century. However, current climate models still struggle to accurately represent it, limiting our comprehension of processes driving melt spatial and temporal variability and its consequences on the stability of the Antarctic ice sheet. Recent advances in Earth monitoring thanks to satellites have enabled new estimations of Antarctic melt extent. They can detect if and where melt occurs, while the amount of meltwater produced can only be deduced from model simulations. In order to combine advantages of both tools, we present new melt estimates based on a regional climate model assimilating the satellite-derived melt extent. This improves the comparison between model and satellite estimates paving the way for a re-estimation of the amount of melt produced each year on the surface of the entire Antarctic ice sheet.

Reference and repeat-observations of land-ice topography is critical to identify causal links between climate and ice trends, generate an accurate record of ice mass balance, and quantify land ice contribution to sea level change. Over the last 30 years, radar altimetry has been instrumental in monitoring ice sheets and their contribution to sea level change. Launched in 2010, the European Space Agency Altimetry mission CryoSat-2 was the first radar altimetry mission with a SAR/Interferometry radar altimeter payload. The aim of this new technology was to gain a better insight into the evolution of the cryosphere, in particular over the steep slopes typically found along ice sheet margins and glaciers where the majority of the mass loss is taking place. CryoSat’s revolutionary design features a Synthetic Interferometric Radar Altimeter (SIRAL), with two antennas for interferometry, the corresponding SAR Interferometer (SARIn) mode of operation increases spatial resolution while also increasing the accuracy of the geo-location by resolving the angular origin of off-nadir echoes occurring over sloping terrain. While the elevation of the Point Of Closest Approach (POCA), or level-2, is the standard product of the CryoSat-2 mission, the Interferometric mode of CryoSat-2 provides the ability to resolve substantially more than just the elevation at the POCA and thus led to a paradigm shift in radar altimetry of land ice. The so-called “swath processing” exploit the fact that over sloping terrain, CryoSat-2 altimeter operates in a manner such that the interferometric phase of the altimeter echoes may be unwrapped to produce a wide swath of elevation measurements across the satellite ground track, well beyond the POCA only. This technique provides the opportunity to increase spatial resolution and to recover elevation over regions where conventional radar altimetry fails; providing an opportunity to monitor land ice trends globally from radar altimetry. Here I will discuss work done over the last decade to develop and apply swath processing over all components of land ice including the Greenland and Antarctic Ice Sheets, ice shelves, and glaciers worldwide, mapping ice mass balance, sub-glacial lakes, ice shelves melting, and improving the understanding of processes linking ice trends to climate forcing. Finally, I will discuss remaining challenges and the opportunities brought by CRISTAL whose primary mode over land ice will be SARIn and who will have swath processing as a core technology to derive time-dependant ice topography.

Land-ice is declining globally, raising sea levels worldwide and impacting glacial risks and access to fresh-water in high-mountain glaciers regions. CryoSat-2’s primary mission objectives are to monitor the changes affecting the world’s sea-ice and large ice sheets to quantify thickness, mass trends and contribution to sea-level change. In practice, CryoSat’s revolutionary interferometric design has allowed several technical breakthroughs and led to the application of radar altimetry to environments that were previously unforeseen. One such breakthrough is Swath processing of CryoSat’s SARIn mode making full exploitation of the information contained in CryoSat’s waveforms and leading to one to two orders of magnitude more measurements than the conventional so-called Point-Of-Closest-Approach (POCA) technique. Following on from the early demonstration of the technique and of its potential impact, the CryoSat ThEMatic PrOducts - SWATH Cryo-TEMPO” project aims to consolidate the research and development undertaken during the CryoSat+ CryoTop / CryoTop evolution / CS2 Mountain Glaciers ESA projects into operational products. The purpose of the thematic products is to make the data available to the wider scientific community in a form that does not require a detailed understanding of the sensor used and extensive post-processing. The first such product CryoTEMPO-EOLIS (Elevation Over Land Ice from Swath) consists of two distinct products; (1) a product containing point cloud of elevations with an associated uncertainty; and (2) a gridded product containing a spatial reduction of the point product onto a uniform grid of time-dependent elevation at 2km spatial posting and monthly temporal resolution, also with an associated uncertainty. In phase one of the project, these two products were released over the Greenland and Antarctic ice sheets. As part of phase two, CryoTEMPO-EOLIS point products were generated over land ice outside of the two largest ice sheets covering glaciers in Arctic Canada, Iceland, Svalbard, Alaska, Russian Arctic, Southern Andes, High Mountain Asia, Greenland Periphery and Antarctic Periphery. Gridded products were also produced over the Vatnajökull and Austfonna ice caps in Iceland and Svalbard respectively. These new gridded products contain a pixel level uncertainty value, allowing the user to refine the pixels used based on the magnitude of uncertainty. This dataset will further the ability of the community to analyse and understand trends across land ice globally. The poster will summarise the approach, provide an overview of the uncertainty and gridding methodologies, and show example use cases. The purpose of the presentation is to stimulate discussion and exchange ideas in the community about further useful products for user analysis and monitoring of climate change.

CRYO2ICE is a campaign that increased the ground track intersection of the CryoSat-2 and ICESat-2 satellites over short time intervals. The orbit change of CryoSat-2 is an enabling step for applications that require co-incident data, such as measuring snow depth and capturing the temporal variation. In addition to aligning the satellites, an efficient data access layer to identify coincident CryoSat-2 and ICESat-2 data measurements is required. The Cryo2Ice Coincident Data Explorer enables users to visualise the spatial intersections for a given time window and download the ESA and NASA data products. The website’s unique temporal separation time functionality allows users to select intersects that are close in time (e.g. 3 hours) up to a 28 day separation, providing useful application for Sea Ice, Land Ice and the Ocean. The intuitive and reactive interface enables users to choose the area of interest by specifying a bounding box or drawing a polygon. Easy to use download scripts allow users to download only their intersecting data, saving a large amount of both download time and data preparation time. The provided KML file allows users to save the visualisation component of their results and view it at a later time. The robust implementation makes it possible to run large queries in batch mode and receive the results via email. The website provides access to CryoSat-2 LRM, SAR and SARIn mode data and ICESat-2 ATL06, ATL07, ATL10, and ATL12 products. Combined datasets for CryoSat-2, linking the LRM, SAR, and SARIn L2 products, and for ICESat-2, linking the ATL06 and ATL07 products, allow users to view and intersect these products at the same time. Predicted ground track data is available, allowing users to view and plan for future CryoSat-2 and ICESat-2 satellite passes and intersections. The portal additionally provides access to CryoTEMPO-EOLIS Point and Gridded products. Airborne missions such as Operation IceBridge data sets are available, with the CryoVex data and its following campaigns coming in the future. The website allows intersections to be computed between any pair of available datasets from different missions, as long as they coincide in time. One could intersect the ICESat-2 ATL07 product with CryoSat-2 SAR mode data, or go outside of the CRYO2ICE scope and intersect airborne Operation IceBridge data with EOLIS Point Product’s swath elevation. Each dataset available on the website can also be queried in single mode, allowing users to view the data independently rather than searching for intersections. This poster will detail the Cryo2Ice Coincident Data Explorer and gather feedback for additional features, capabilities and datasets. A new combined CryoSat-2 and ICESat-2 product, created to make coincident data even easier to use and download, will also be presented.

The Copernicus Polar Ice and Snow Topography Altimeter(CRISTAL) mission, planned to be launched in 2027 will incorporate a dual Ku/Ka-band interferometric altimeter with specific transmission pulse sequences designed to enhance the performances over sea and land ice. The open burst mode will enable the generation of Fully Focussed products over sea ice with snow depth retrievals derived from the Ku/Ka range differences instead of taking them from external auxiliary data. In the same way, as in CryoSat-2, the closed burst interferometric mode over land ice will allow the generation of swath elevations for the full Greenland and Antarctica, improving the current coverage of the CryoSat-2swath products that are only produced in the ice margins. At this stage of the mission design, phase B2/C/D, the expected performances need to be evaluated against the requirements to verify the effectiveness of the mission configuration and assess its compliance. In this framework, an end-to-end validation environment has been designed. It is composed of the System and InstrumentSimulator (SIS), the Ground Processor Prototype (GPP), and the Performance assessment tool (PAT). Following the validation plan defined during the first stage of the project, the SIS will be in charge of generating datasets for the different scenarios that are foreseen to be of interest for the mission performance assessment (e.g. point targets, sea ice with different snow properties, ice sheet with small slope and uniform snow and ice characteristics, glaciers with different size, slope, and orientations, ocean tracks with different SWH and wind conditions, river and lakes for specific size and geometry). The GPP will process the simulated data using different processing chains to ensure compliance with the functional and performance requirements. It is composed among others of Level1 Calibration chains, Level1 Low Rate chains(LR-RMC, LR Over-Sampled, and the conventional LR), Level1Delay Doppler chain, Level1 Fully Focussed chain, Level2retrackers module (compilation of different retrackers tailored for the different thematic surfaces), Level2Geophysical corrections and retrievals (translating the information from the retrackers into sea ice, land ice, ocean and inland waters measurements). The PAT is in charge of closing the end-to-end chain: it will cross-check each of the geophysical parameters generated by the GPP against the corresponding requirement, starting from the knowledge of the simulated parameters, assessing and validating the end to end performance chain. This presentation will give an overview of the expected performances of the CRISTAL mission based on the end-to-end validation activity carried out in this project.

Over the past 30 years, altimetry has revolutionised our ability to monitor surface conditions, quantify changes of the world’s ice masses and its impact on sea level, water availability, and glacial risks. With two high resolution altimeters currently active – the interferometric radar altimeter CryoSat-2 and the laser altimeter IceSat-2 – the present period offers a unique opportunity to co-exploit the observations made by the two sensors and improve the monitoring of ice height and trends. Recent advances in swath altimetry processing, using the interferometric synthetic aperture radar (SARIn) mode of CryoSat-2, have enabled improved spatial resolution of surface elevation. Meanwhile, IceSat-2 provides enhanced resolution compared to the previous generation thanks to its six laser beams. However, Radar and laser altimeters have different intrinsic properties and behaviours. Joining and interpreting their measurements requires careful consideration of factors such as differences in electromagnetic interaction with the surface, impact of weather, and footprint size. Here we use a Deep Neural Network to combine elevation measurements acquired by ESA’s CryoSat-2, SARIn waveform parameters, NASA’s Operation Ice Bridge, IceSat-2, and surface conditions over the Greenland Ice Sheet. We explore the difference between radar and laser altimetry and its relationship with surface condition, the impact of penetration of radar waves into snow and firn, and the respective measurement uncertainties. While neural networks have been increasingly utilised in a wide variety of academic and commercial applications, their use for correcting elevation bias within the cryosphere is novel. The modelled elevation correction will be used to generate time-dependent Digital Elevation Models. Finally, we explore the potential to map ice, snow and firn surface conditions based on the relative differences between laser and radar instruments.