The thicknesses of sea ice and the snow that rests upon it are recognised as Essential Climate Variables by the WMO, critical for understanding, monitoring, and predictions of Earth’s climate. However, snow depth on sea ice is difficult to measure by satellite due to how radar penetrates and scatters off the ice, presenting challenges for assessing sea ice thickness.

The challenges surrounding quantifying this variable can have knock on considerations for monitoring ice mass balance, understanding of polar climate feedbacks, the operational safety of shipping routes, and ecosystems. As snow depth on sea ice is dynamic and precipitation and snow pack properties can evolve through seasons as well as varying over longer timescales due to warming, the gap in understanding could become increasingly consequential over time.

A discovery with the KuKa radar was developed into a novel snow depth retrieval approach. KuKa can be operated looking straight down (using Altimeter mode); and looking at an incidence angle (using Scatterometer Mode); both provide can both waveforms and normalised radar cross section values. Scientists have found that polarisation can help to determine snow depth on Arctic and Antarctic sea ice, which would also support estimations of sea ice thickness.

On Friday 8 May, Dr Rosemary (Rosie) Willatt (UCL) will present at EGU26 on the progress of the Polarimetric Synthetic Aperture Radar Altimeter concept (PoSARA) — a novel satellite instrument concept using polarimetric capability to estimate snow depth on sea ice, land ice and land from space. She will share with the audience how well the technique works over Arctic and Antarctic sea ice, lake ice and Arctic tundra, derived from multiple field campaigns.

“Making the unexpected discovery that using polarisation of waveforms provided accurate estimates of snow depth on sea ice in the initial MOSAiC dataset was exciting – nobody had predicted it but it made sense given existing theory on depolarisation in snow and we found one example of another instrument which observed something similar over a glacier. We then found our approach also worked with KuKa data from the Southern Ocean, and over tundra and lake ice in Churchill and Resolute.” – Said Rosie, commenting on the project for CPOM.

The team has developed the concept through to Scientific Readiness Level (SRL) 3 as part of ESA’s NEOMI initiative (New Earth Observation Mission Ideas). NEOMI aims to scientifically advance new Earth Observation mission ideas, empowering emerging scientists as lead investigators for potential future satellite missions and bold new EO research, and to formulate and develop a new scientific idea for an Earth Observation mission up to SRL 3.

Rosie, who is also CPOM’s Principal Investigator (PI) for Sea Ice Earth Observation, was awarded the ESA inaugural Konrad Steffen Award for a presentation on the early stages of this work, and is PI of the project, developing the concept for space application.

The science behind it has been actively tested in the field more recently too. In April 2025, an all-female field team of polar scientists from CPOM and UCL, including Rosemary Willatt, Julienne Stroeve, Carmen Nab and Alicia Fallows, visited Resolute Bay to investigate the use of this frequency radar and different polarisations on ice and snow.

You can watch a video the team made about the fieldwork here: https://cpom.org.uk/testing-kuka-in-the-arctic-new-video/

Satellites observing Earth’s polar regions give scientists the information they need to monitor how ice sheets and sea ice are changing, quantify their contribution to rising seas, and better understanding the complex ways that melting ice reshapes global weather systems.

Read the abstract and find out more about this ‘Highlight’ presentation on the EGU26 website.

Header image credit: Professor Alison Banwell

Feature image credit: Dr Amy Swiggs

CPOM PhD Researcher Ben Graves (KCL) will present this science as part of Session HS2.1.4 on Tuesday, 05 May, 11:55–12:05 (CEST) in Room 3.29/30.

Meltwater from glaciers is an important source of water for downstream communities, so monitoring and projecting the impacts of glacier retreat on these water sources is important when planning for future changes.

But in regions where there are monsoons this can be particularly challenging, as heavy rainfall can obfuscate contributions from glaciers.

This study, led by Ben, used measurements of the isotopes of oxygen and hydrogen found in water samples to estimate the origin of water flowing in the Dudh Koshi river, Nepal.

Isotopes are different versions of the same chemical element that have the same number of protons but a different number of neutrons in their nucleus. This means they have the same chemical behaviour but slightly different masses.

The research integrated new and previous observations from river and snow samples showing different isotopes, in glacio-hydrological modelling, to trace the water sources.

Preliminary results from samples taken post-monsoon revealed the highest contribution of meltwater ever seen in this region.

Find out more by reading the abstract and attending their presentation online or in-person at EGU26.

Feature image credit: Professor Andrew Shepherd

Header image credit: Professor Alison Banwell

CPOM Doctoral Researcher Yiliang Ma (SCENARIO DTP, University of Reading) will present this science as part of Session CR2.2 on Monday, 04 May, 17:00–17:10 (CEST) in Room L2.

Ice–climate feedbacks, the ways in which ice and climate mutually influence and compound each other, are a crucial element in the mechanisms of ice loss in ice sheets. However, many Earth System Models, designed to project climate change, fail to treat ice sheets as interactive components.

This study, led by Yiliang Ma, uses state-of-the-art UK Earth System Model (UKESM) to run two multi-century climate simulations under high-emissions forcing (SSP5–8.5) to compare and quantify the difference between projects of an evolving Greenland ice sheet against a static one.

Yiliang and the team explored the impacts of incorporating ice-climate feedbacks which showed that a reduction in surface albedo as ice is replaced by darker rock, combined with reduced ice sheet elevation, causes more solar energy to be absorbed and accelerates warming, increasing mass loss.

This research emphasises the importance of Earth System Models incorporating a dynamic Greenland ice sheet. As the ice sheet could contribute 7m to global sea levels it’s crucial feedback loops like those identified in these simulations are reflected in future projections of ice melt, particularly when predicting sea level rise.

Find out more by reading the abstract and attending their presentation online or in-person at EGU26.

Feature image credit: Professor Mal McMillan

Header mage credit: Professor Ali Banwell

This study, led by Dr Lauren Gregoire, uses state-of-the-art coupled model FAMOUS–BISICLES (General Circulation Atmosphere–ice-sheet model) to examine ice sheet changes in the Northern Hemisphere during the two most recent deglaciations (which took place around 21,000 to 7,000 years ago and 140,000 to 128,000 years ago).

The FAMOUS model (Fast Met Office—UK Universities Simulator) produces simulations for atmosphere–ocean, while BISICLES, which was developed in partnership with CPOM scientists, simulates ice sheet dynamics using adaptive mesh refinement for higher resolution in critical areas such as the grounding line of the ice sheet. By bringing these two models together FAMOUS-BISICLES can simulate climate-ice sheet interactions over thousands of years.

Following PMIP4 (Palaeoclimate Model Intercomparison Project 4) protocols, the team used ongoing climate model outputs for sea surface temperatures and sea ice to drive the simulations. They assessed the impact of concentrations of greenhouse gases, variations in the Earth’s orbit and orientation relative to the Sun, and uncertainties in model parameters and sea surface temperature, on the model projections of the patterns of ice retreat.

The study projected that there was an acceleration of ice retreat during the final stages of the last glacial person (referred to as Bølling warming), but results varied dependent on the type of terrain and the abruptness of sea surface temperatures. The study also identified marine-based sections of the ice sheet as particularly sensitive to ocean changes.

Understanding how and why ice sheets retreated during previous deglaciations gives us a longer-term perspective on ice sheet behaviour, extending far beyond the few decades of satellite observations. Coupled models like FAMOUS-BISICLES can be tested against these past events, helping us refine and validate the tools we use to project current and future ice loss.

Find out more by reading the abstract and attending their presentation online or in-person at EGU26.

Feature image credit: Dr Amy Swiggs

Header mage credit: Professor Ali Banwell

The European State of the Climate (ESOTC) 2025 report released today, paints a picture of accelerated rising temperatures across the globe, with Europe warming at more than double the speed of the global average.

The report points to the latest assessment of ice mass balance from the Ice Sheet Mass Balance Intercomparison Project (IMBIE) led by CPOM’s Co-Director of Science Dr Inès Otosaka, which shows ice loss from the Greenland ice sheet at 139 billion tonnes during 2025* (see figure 1).

The polar ice sheets, in Greenland and Antarctica, store a significant proportion of the Earth’s freshwater. When they melt, they contribute this freshwater to the oceans, not only increasing sea levels, but also affecting ocean circulation. Estimates of the Antarctic and Greenland Ice Sheets mass balance produced by IMBIE, an international collaboration of polar scientists led by CPOM and supported by the space agencies ESA and NASA, are used in this report’s key climate indicator on Ice Sheets.

The report also includes other events across the cryosphere related to warming, including a three-week heatwave in sub-Arctic Fennoscandia with Arctic temperatures going over 30°C*. Glaciers across Europe also retreated, including in Iceland where the country saw the second worst loss of glaciers in recorded history*.

Rising sea surface temperatures, marine heatwaves, reduced river flows, and extensive wildfires are included in the report as key impacts of the rapid warming*.

About the European State of the Climate report

The European State of the Climate report is an annual report compiled by the Copernicus Climate Change Service (C3S) and the World Meteorological Organization (WMO) and implemented by ECMWF on behalf of the European Commission.

With 100 scientific contributors, including experts in cold environments, the report features graphics and visuals reflecting the most up-to-date data, providing an all-encompassing view of the state of the climate and important changes in climate indicators impacting the continent.

Climate change, and the associated impact on the cryosphere, affects ecosystems around the world. Although the report references important actions in European policy and frameworks focussing on improving ecosystem resilience, this report calls for enhanced and ‘accelerating’ progress in protecting nature and biodiversity, in light of rapidly increasing changes in the climate.

About IMBIE

The IMBIE Project (Ice Sheet Mass Balance Intercomparison Project) was launched in 2011, and funded by the European Space Agency (ESA) and NASA. IMBIE aims to reconcile satellite-based measurements of ice sheet mass balance through community efforts, to reduce uncertainties in estimates of Antarctica and Greenland ice loss and constrain projections of future sea level rise. Data produced by the IMBIE Team are widely used by leading organisations, including by the Intergovernmental Panel on Climate Change (IPCC).

The IMBIE Team has produced three assessments during this period, in 2012, 2018 and 2023.

*C3S/ECMWF and WMO, 2026: C3S-WMO European State of the Climate 2025, climate.copernicus.eu/ESOTC/2025, doi.org/10.24381/zy93-sb27

It is with great sadness that the Centre for Polar Observation and Modelling (CPOM) learned of the passing of Professor Lord Julian Hunt of Chesterton. We write to convey our deepest condolences to his family and all who were close to him.

Julian was an early and influential member of CPOM when the Centre was established at University College London, and his involvement in those early years left an enduring mark on what it became. He brought to CPOM a wealth of experience that few could match. Having served as Director General and Chief Executive of the Met Office from 1992 to 1997 — one of the most senior scientific leadership roles in British science — he arrived at UCL with an exceptional command of atmospheric dynamics, environmental fluid mechanics, and the practical demands of weather and climate prediction at the highest level. It was this breadth, spanning fundamental theory and real-world application, that made his contribution to CPOM’s early meteorological programme so distinctive.

At CPOM, Julian led research into polar atmospheric boundary layer processes and mesoscale meteorology — the complex dynamics of atmospheric flows over polar surfaces, coastlines, and topography that are so critical to understanding the cryosphere. This work was both theoretically rigorous and of direct practical relevance to polar forecasting. He collaborated widely, producing research that made a lasting contribution to the field. His work included studies of Coriolis effects in mesoscale flows with sharp changes in surface conditions as well as investigations into the influence of coastal geometry and surface discontinuities on polar wind patterns. Together they also advanced understanding of how changing surface heat fluxes affect atmospheric boundary-layer flow, work carried out with colleagues across several institutions and reflective of Julian’s natural gift for building international scientific collaborations.

Those of us fortunate enough to work alongside Julian remember him not only for his formidable intellect, but for the tremendous energy and kindness he brought to everything he did. He was warm and thoughtful in equal measure, and made those around him feel both challenged and supported. He had an inexhaustible enthusiasm for ideas and for the people pursuing them. Beyond his science, Julian stood apart for his fierce commitment to social justice and his deep conviction that science must serve the public good. These values animated his work and his public life in equal measure. He was also a man who spoke openly and proudly of his family, and it was clear to all who knew him that they were his greatest source of pride.

Julian’s legacy lives on in the work of CPOM and in the many researchers whose careers and thinking he shaped. He will be greatly missed, and fondly remembered.

With our sincere condolences,

Professor Andrew Shepherd, CPOM Director
Professor Sir Duncan Wingham, Founding CPOM Director
Dr Andrew Orr
Professor Danny Feltham
Ms Leisa Clemente

Between 1979 and 2023, the Antarctic Ice Sheet lost on average 107 Gt of ice per year, contributing a total of 13.4 mm to sea level rise. As global temperatures continue to rise, accelerated melting is expected as well as increased contributions to global sea levels.

Tracking that loss accurately depends on satellites measuring ice sheet height from space and on understanding exactly how robust those measurements are over complex terrains in the cryosphere.

New research from CPOM, published last week in The Cryosphere led by Joe Phillips and Mal McMillan at Lancaster University used REMA, the Reference Elevation Model of Antarctica, a highly detailed map, to assess of the Sentinel-3 radar altimeter’s performance across the Antarctic Ice Sheet.

About Sentinel 3

Sentinel-3 has provided operational SAR altimetry coverage of Antarctica since 2016. Although primarily designed for ocean and land monitoring, it includes a high-resolution radar altimeter capable of measuring ice sheet elevation and sea ice thickness change. Thus, it a valuable operational complement to ESA’s CryoSat-2 Earth Explorer mission, the first such radar altimeter satellite primarily dedicated to studying the Earth’s ice.

Radar altimeters, like Sentinel-3’s however face a challenge in that measurement quality tends to degrade where terrain gets steep and rough, such as at the margins of ice sheets.

The study

The research used REMA to assess how accurately Sentinel-3 captures measurements over the Antarctic Ice Sheet’s complex terrain. Recent advances in data processing have allowed more data to be retrieved with over 94% of acquisitions successfully capturing the point of closest on the ice surface. A key requirement for reliable data is that the instrument records the point of closest approach on the ice surface, something made harder by Sentinel-3’s relatively narrow 60 m measurement window.

In this regard, the study showed how increasing the window size made a substantial difference. For example, with a 240 m window, like that operated by CryoSat-2, there was near-complete (99%) surface capture across the entire ice sheet, including the most complex margins (compared to a mean capture of 90.6% at 60 m). This is an important consideration for future missions, such as the Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL).

About Radar Altimetry

Radar altimetry works by firing pulses of microwave energy at Earth’s surface, timing how long it takes for the echo to return, giving a precise measurement of surface elevation. The echoes are recorded as a power waveform, (the echo returning through time), and the elevation measurement is taken from the first steep rise of the waveform with the assumption being that this peak relates to the Point of Closest Approach (POCA) giving a single elevation measurement per echo. Satellites return an echo of a limited recording window of time (range window), but if this is misplaced, the echo from the surface can be missed. Although previous assessments of Sentinel-3’s radar have focused on validations of the final elevation products, more detailed assessments of the instrument and processor performance are less common.

About the study

The team investigated how much of the ice sheet surface Sentinel-3 captures within its range window, whether the leading edge of the waveform can be attributed to the closest point on the surface, how consistently radar echoes look from one measurement to the next; and the role that key surface topography characteristics such as slope and roughness play on all of these effects.

They analysed over 8 million radar echoes from Sentinel-3A and 3B, comparing the latest processing version (BC-005) against its predecessor (BC-004) and produced accurate, continent-wide maps of ice surface slope and roughness from the Reference Elevation Model of Antarctica (REMA), a 100 m resolution mosaic built from satellite stereo imagery.

The results of the study found that for 57.4% of acquisitions, capturing 100% of the illuminated surface is impossible with the current 60 m window. It also found that, on average, Sentinel-3’s placement of the range window captured 89.2% of the maximum topographic signal that could be recorded within its range window.

By exploring the hypothetical impact of increasing the window size, the study found that this made a substantial difference. For example, implementing a 240 m window, like with CryoSat-2, there was near-complete surface capture across the entire ice sheet, including the most complex margins (compared to a mean capture of 90.6% at 60 m).

The study also produced the first slope-independent roughness map of the entire Antarctic continent (to their knowledge). The code for this can be found at https://github.com/Joe-Phillips/SAR-Altimetry-Flyover-Visualiser and a clip of the animation can be seen at the top of this article.

The future of radar altimetry for monitoring Antarctica

This bodes well for future retrievals from the CRISTAL mission, with its 256 m window. CRISTAL is ESA’s next-generation polar ice altimeter, planned for launch in 2027, and the successor of the CryoSat-2 mission.

By identifying and quantifying one of the main challenges of previous generations of altimetry – performance over complex Antarctic terrain – this study provides a strong evidence base for the next generation of instruments.

It’s vital we have the most accurate understanding of current and future ice loss, so we can plan for future changes in global sea levels.

The only way this is possible is by assessing, calibrating and improving the data we retrieve from satellite missions like Sentinel-3 and CryoSat-2 and informing future satellite missions like CRISTAL.

All image credits: Phillips, J. and McMillan, M.: Assessment of Sentinel-3 altimeter performance over Antarctica using high resolution digital elevation models, The Cryosphere, 2026.

A study published in Geophysical Research Letters on 09 March 2026 projects that by 2067, ice loss from Thwaites Glacier in West Antarctica could be 180-200 billion tons of ice per year, almost the current annual losses from the entire Antarctic ice sheet.

The study, led by Dr Dan Goldberg (University of Edinburgh) with co-authors Professor Noel Gourmelen (University of Edinburgh) and Professor Mathieu Morlighem (Dartmouth), tested two independent ice sheet models (STREAMICE and ISSM), training them using two types of satellite observation: velocity change from interferometry, and surface elevation data from altimetry missions.

The research found that calibrating models solely using surface elevation change data produced volume change predictions which were ten times more accurate than those using ice speed data. This shows the choice of calibration method has a significant effect on long-term projections.

This research is funded in the context of ESA’s 5D Antarctica project within the Polar Science Cluster.

Read more about this research on the ESA EO Science For Society website.

More information on the research

Goldberg, D. N., Morlighem, M., & Gourmelen, N. (2026). Recent observations of Thwaites Glacier, West Antarctica are consistent with high rates of loss in next 50 years. Geophysical Research Letters, 53, e2025GL118823. https://doi.org/10.1029/2025GL118823

News feature image credit: Professor Andrew Shepherd

Research from education charity Teach First in 2024 found that more than half of girls (54%) lack confidence studying maths compared to 41% of boys, with the gap even wider for science where 43% of girls say they lack confidence compared to only 26% of boys despite the fact that girls often outperform boys in these subjects. The consequences reach beyond the classroom: women only make up 26% of the UK’s Core-STEM workforce.

This International Women’s Day, we want to highlight how important it is to support girls to study STEM at school. This blog by CPOM PhD Researcher Alicia Fallows (UCL), explains how her teachers and family encouraged her journey into polar science, which has already taken her to the Arctic Circle.

Blog by Alicia Fallows

How a love of Physics at school led Alicia to the Arctic Circle

I’ve always adored the natural world and based upon my favourite subject at A-Level decided to pursue my undergraduate degree in Physics as a way to delve into this planet and its components.

Along the way I became very interested in quantum physics, something I still find fascinating, and followed a Master’s in a similar field. Towards the end of my Master’s I realised I wanted to apply my skills to something more tangible and come back to my love for the natural wonders of this planet, encouraged even more so in the context of climate change.

After working for a few years, I found the London NERC DTP as a perfect way to come back to research with a brilliant network of academics offering exciting PhD projects. By this time, I knew I wanted to focus on snow and ice, in part due to a love of glaciers formed visiting Mont Blanc when I was 17, as well as from watching David Attenborough’s Frozen Planet! I also felt the cryosphere was being heavily impacted by our changing climate.

I didn’t set out for a project specifically dedicated to the polar regions, as I didn’t even know it would be something within my reach. After meeting with my (now) supervisor Rosie (Dr Rosemary Willatt, UCL and CPOM), I realised how I could transfer my skills to sea ice and snow physics, with a focus on some of the most remote and important parts of our planet!

I feel lucky to have a family that have always supported me to pursue anything I wanted and additionally encouraged me to cherish our planet by getting outdoors a lot from a young age (not being afraid to get mucky). Time spent outside hiking, often with our beloved dog, and witnessing my families interests in botany, geology and adventure, only made me more interested in the sights I saw and the science behind them.

I was fortunate enough to have a few brilliant science teachers in both school and sixth form college who believed in me and supported my ambitions to study further, as well as showed their passion for physics and chemistry. And some brilliant drama/dance teachers who helped me to build confidence!

My parents were instrumental in my choice to apply to university, and my friends and partner have supported me throughout the years. At university my undergraduate dissertation supervisor was incredibly encouraging and made me believe I was capable to stay within science in the future. Nevertheless, turning up to a physics degree as one of a handful of women, with only a handful of women lecturers, was daunting. I hope we can turn this around further to encourage more girls and women to not only come into science, but to stay in it. Last year I was lucky enough to be part of an all-women field team – so hopefully we are on a good trajectory!

It never occurred to me the range of interdisciplinary subjects that can be studied at university, and being a scientist was never presented to me as a choice at careers meetings. I am grateful to have studied physics and the flexibility this has given me, but I’d like girls to know that there are so many options out there and the path doesn’t always have to be straightforward!

Stories like Alicia’s show why it’s so important to encourage all children and young people to engage with science. That’s we’ve created resources to help parents and teachers introduce children and young people to polar science.