Global impacts of climate extremes in the polar regions: is Antarctica reaching a tipping point?

Ice shelves, the floating extensions of the Antarctic Ice Sheet, are melted from below by the ocean. Increased ice shelf melting is the main mechanism by which Antarctica currently contributes to global sea level rise. As melt rates are sensitive to temperature, salinity, and circulation in tiny pockets of the Southern Ocean, predicting how they might respond to climate change is not straightforward. Projecting future ice shelf melting is at the forefront of coupled Earth system modelling, as most climate and ocean models still do not include ice shelves at all. This talk will summarise what is and is not known about how ice-ocean interaction may respond to climate change. In some regions, such as the Amundsen Sea in West Antarctica, relatively warm ocean water already accesses the ice shelves. However, climate change is expected to make these regions warmer still, by increasing the volume of warm water flowing onshore. Other regions, such as Antarctica's largest ice shelves, the Ross and Filchner-Ronne, are currently bathed in cold water and melt rates are stable. Unfortunately, models predict that with sufficient climate change, these cavities could suddenly flip into a warm state similar to the Amundsen Sea. While some changes are likely already committed, other changes may or may not be triggered, depending how much the climate warms. Therefore, the trajectory of future carbon emissions will likely have a large impact on Antarctica's long-term contribution to sea level rise.

Dr Kaitlin Naughten

British Antarctic Survey, UK

Dr Kaitlin Naughten

British Antarctic Survey, UK

Kaitlin Naughten is an ice, ocean, and climate modeller at the British Antarctic Survey. She develops models to simulate interactions between the Southern Ocean, the Antarctic Ice Sheet, and the broader climate system. Kaitlin's research focuses on how ice shelf-ocean interactions change in responds to a warming climate. She studies warm ice shelf cavities which could get warmer (eg the Amundsen Sea) as well as cold cavities which could suddenly flip to a warm state (eg the Ross and Filchner-Ronne Ice Shelves). Her research on West Antarctic ice shelf melting was the #7 most covered climate study of 2023 by the international media (Carbon Brief). Kaitlin is a member of the core development team for the UK Earth System Model, the world's first global climate model to include an Antarctic Ice Sheet fully coupled to the ocean.

Antarctic sea ice, after enjoying a period of sustained, steady growth, supplemented by several above average sea ice extents in winter and summer over the satellite-observed era has, since 2016, apparently transitioned to a period of sharply reduced sea ice extent (SIE), manifested by extremely low SIE in summer (2017, 2022, 2023, 2024, 2025) and extremely low SIE in winter 2023, 2024 and 2025 (projected). Such unexpected behavior of the Antarctic sea ice system is not reproduced in climate models, which may indicate some major deficiencies in our understanding and in the skill of projections. However, it has prompted the questions - is this a short-term change, or has there been a structural change in the sea ice system? Is this abrupt change associated with natural variability or a forced signal related to anthropogenic activities? To begin answer these questions, we place the present SIE variability within the context of SIE variability for the 20th century using an ensemble of SIE reconstructed using Bayesian statistics. We query the characteristics of the SIE to find out if the variability that we see fits the picture of structural change. Results indicate that there has been a structural change in the Antarctic sea ice system, specifically that SIE no longer reverts to the mean. Instead, it has become a system characterized by extremes. We discuss what that means for the future of Antarctic sea ice and the ecosystems which it supports and how certain are we about it.

Professor Marylin Raphael

University of California Los Angeles, USA

Professor Marylin Raphael

University of California Los Angeles, USA

Professor Marilyn Raphael is a physical geographer interested in climate variability and change in the high latitude Southern Hemisphere. Her work focuses on Antarctic sea ice variability, specifically the way in which the sea ice and the largescale atmospheric circulation interact, thereby creating potential for prediction of Antarctic climate change at the seasonal, interannual and decadal timescales. The results of her research have implications for the Antarctic climate, global climate change and the global, societal response. Marilyn is a Professor of Geography at the University of California, Los Angeles and former President of the American Association of Geographers. Marilyn is also a Member of the US National Academy of Sciences, a Fellow of the American Academy of Arts and Sciences and a Member of the American Philosophical Society. She is co-Chair of the SCAR expert group, Antarctic Sea ice Processes and Climate (ASPeCt). In this role she promotes research on Antarctic sea ice observations and modeling and coordinates the efforts of the international science community bringing together expertise on the observational and modeling aspects of the climate.

Climate change, in conjunction with human-induced pressures, has left no region untouched, including Antarctica. From 1992 to 2020, the Antarctic ice sheet lost ice mass at an average rate of 92 ± 2.2 gigatons per year, contributing to a global sea level rise of about 12 cm, mostly due to the West Antarctic Ice Sheet and the Antarctic Peninsula ice losses. Deep uncertainty exists regarding future Antarctic contribution to sea level rise with the potential for rapid, nonlinear responses due to marine ice sheet instability, marine ice cliff instability and hydrofracturing. The latter is enhanced by melt water and rainfall – the phenomena linked to extreme warming events already impacting Antarctic marginal zones and moving further inland. Many of these warming events are associated with atmospheric rivers, which are projected to roughly double in frequency by 2100 with an increase in precipitation delivering intense rain-on-snow and warm/moist air spiking surface melt and preconditioning ice shelf hydrofracturing and accelerated grounded ice loss. At the same time increased snowfall is also projected over Antarctica especially due to extreme weather events, offsetting dynamic mass loss. Thus, large uncertainty exists, and questions remain if with continued warming surface melt and rainfall bringing enhanced risk of hydrofracturing and ice-shelf loss will dominate the increase in snowfall and its accumulation inland. Increased magnitude and probability of occurrence of extreme events, along with their high impacts on the Antarctic surface mass balance and large future uncertainty require detailed understanding of the underlying large-scale, regional and local drivers, using comprehensive and high-resolution observations and modeling. In this presentation, I will discuss recent advances in our understanding of extreme weather events, particularly atmospheric rivers, their present-day drivers and impacts and future uncertainties.

Dr Irina Gorodetskaya

CIIMAR - Interdisciplinary Centre of Marine and Environmental Research of the University of Porto, Portugal

Dr Irina Gorodetskaya

CIIMAR - Interdisciplinary Centre of Marine and Environmental Research of the University of Porto, Portugal

Irina Gorodetskaya is a polar meteorologist and climate scientist studying extreme weather events and atmosphere-ocean-cryosphere interactions in the polar regions. She has a PhD in Atmospheric Science from Columbia University (USA) and worked in France, Belgium and Portugal. Currently she is a principal researcher at the Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto. Participated in expeditions in the Arctic, over the Antarctic ice sheet and in the Southern Ocean, with ongoing measurement projects over the Antarctic Peninsula focusing on atmospheric rivers and their impacts. Contributing to major international initiatives, including the WMO’s Polar Prediction Project and its flagship activity, the Year of Polar Prediction (YOPP) and AntClimNow – SCAR research programme on near-term variability and prediction of the Antarctic climate system. She is part of the Scientific and National Coordination of the AntarcticaInsync – a globally coordinated scientific initiative bringing together observing and modeling systems to tackle Antarctic and Southern Ocean environmental change. Bringing science to society as a lead author of the Intergovernmental Panel on Climate Change (IPCC) 6th Assessment Report and an invited speaker and delegate to the UN Climate Change Conferences.

The Southern Ocean CO2 sink has shown important variations in the recent past, with a reduction during the 1990s, a reinvigoration in the 2000s, and a levelling off emerging in the last decade. These decadal variations have been attributed in part to the increase in winds resulting from the depletion of stratospheric ozone, modulated in time and space by contributions from a range of thermodynamical processes. The presence of large decadal variations in the Southern Ocean CO2 sink during the recent past could suggest a potentially strong response to future climate change. However, this is unlikely to be the case as several factors combine to dampen the response of the Southern Ocean CO2 sink to climate change this century. First, the expected healing of the ozone layer leads to a reversal of its intensifying effect on winds. As a result, the influence of projected changes in mixed-layer depth on carbon nearly cancels that of projected changes in overturning circulation. In addition, the influence of changes in physical dynamics on CO2 diminishes with the level of warming due to the reduction in the vertical gradient of dissolved inorganic carbon. Overall, the carbon-climate feedback originating from the Southern Ocean decreases this century in a warming climate and becomes increasingly dominated by the effect of warming on CO2 solubility, which is well represented in models. The response of marine ecosystems to projected changes in nutrients driven by changes in ocean dynamics is unlikely to alter this conclusion, but it would influence the equilibrium CO2 level in the atmosphere in the long-term. The potential influence of more complex ecosystem-driven changes on the Southern Ocean CO2 sinks this century and beyond has not been thoroughly tested with models. It would benefit from the development and use of a new generation of Ocean System Models (OSMs) designed to address marine challenges, maintained by leading oceanography institutes, and grounded in the best available observations.

Professor Corinne Le Quéré CBE FRS

University of East Anglia, UK

Professor Corinne Le Quéré CBE FRS

University of East Anglia, UK

Professor Corinne Le Quéré CBE FRS, is Royal Society Research Professor at the University of East Anglia, where she conducts research on the interactions between the carbon cycle and climate change, particularly those mediated by the world’s oceans. She leads two projects in the NERC’s programme on the Role of the Southern Ocean in the Earth System (RoSES), one examining Southern Ocean CO2 variability in recent decades, one exploring its evolution this century. More broadly, she spearheaded the development of marine carbon-cycle models with new ways to represent plankton diversity and ecology. She also led for over a decade the annual update of the ‘global carbon budget’, an international effort to keep track of global carbon emissions and their fate in the environment, and authored three assessment reports of the Intergovernmental Panel on Climate Change (IPCC).

Sponge beds and coral gardens are dominant Antarctic deep-sea ecosystems. These vulnerable marine ecosystems (VME) are rarely studied and hard to maintain ex situ making understanding their responses to climate change a substantial logistical challenge. The outcomes of the few experiments undertaken are mixed but overall predictions for these ecosystems are seemingly poor. Known climate change (marine temperature and water acidity changes) impacts include necrosis, reduced fecundity, and weaker skeletons. Habitat suitability modelling infers the envelope for life for this organisms under future climate change scenarios is greatly reduced, a smaller area of Earth will be suitable for their existence. Community network analysis predicts wide scale impacts for the most abundant deep-sea fauna should some sponge species cease to exist. Worryingly, with the measured in situ water chemistry changes of ocean acidification and reduced oxygen, there has been rapid deterioration of sponge beds over only a six-year time scale in Canadian waters. Climate change impacts in deep Antarctic waters are harder to monitor and predict.

Dr Michelle Taylor

Ocean Census and University of Essex

Dr Michelle Taylor

Ocean Census and University of Essex

Dr Michelle Taylor’s research focuses on how well-connected populations in the deep sea are genetically across depth, areas, and time – looking at their evolutionary relationships, their community structures, and what drives where they thrive. She is Head of Science for Ocean Census, a Nekton-The Nippon Foundation initiative to accelerate marine species discovery. And she runs a lab group at the University of Essex that has a focus on marine population genomics, video surveying for community analyses, and habitat suitability modelling. Her favourite taxa are corals, and she has described and discovered many of them globally on the dozen expeditions she has partaken in and led. Her PhD was undertaken on Antarctic deep-sea coral.

Dr Taylor has worked at the universities of Imperial College, Oxford and Essex primarily but has grants and projects with several international academic institutions and is President of the Deep-sea Biology Society.

The Scientific Committee on Antarctic Research (SCAR) initiates, develops and coordinates high quality international scientific research in the Antarctic region, and on the role of the Antarctic region in the Earth system. SCAR also provides objective and independent scientific advice to the Antarctic Treaty System and other bodies. The Antarctic Treaty Parties have made specific requests to SCAR for updates on climate change and its impacts on the Antarctic environment, which SCAR provides using the best available scientific information on climate change and its impacts, to support their decision-making.

Warming and in the increased frequency, severity and duration of extreme events in the near term will mean that many terrestrial, freshwater, coastal and marine ecosystems are at very high or high risks of losing biodiversity (IPCC AR6). This underscores an urgent need for robust scientific advice to inform policy decision-making, particularly on the conservation of Antarctic biodiversity. Extreme climate and weather events such as record low sea ice extent, heatwaves and the collapse of ice shelves will also present new challenges for unique Antarctic ecosystems as well as for the management of human activities in Antarctica.

In this talk we will showcase SCAR's work that synthesises complex scientific findings on climate extremes and their impacts, communicates accessible information, and delivers actionable advice to the Antarctic Treaty System, including through the regularly updates SCAR Antarctic Climate Change and the Environment reports.

Chandrika Nath

SCAR, UK

Chandrika Nath

SCAR, UK

Dr Chandrika Nath has over 20 years’ experience of working at the science/policy interface in a wide variety of national and international contexts.

A former glaciologist, she is currently Executive Director of the Scientific Committee on Antarctic Research (SCAR), the leading global organisation supporting collaboration in Antarctic Research and providing advice to the Antarctic Treaty System. With an international membership of 46 nations and 9 scientific unions, SCAR plays a leading role in facilitating international scientific collaboration in Antarctic Research, coordinating over 30 research groups across all disciplines and organising the Antarctic community’s most well attended international conference every two years. It also plays a key role in providing objective advice to the Antarctic Treaty Consultative Meeting, the Committee on Environmental Protection and the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).

Prior to joining SCAR, Dr Nath was Acting Head of the UK Parliamentary Office of Science and Technology (POST), an office providing scientific advice to Members of both Houses of Parliament. She has briefed UK policymakers on a wide range of areas spanning environment, energy, security, ICT and international development.

Dr Nath has a keen interest in capacity building and has worked with parliaments and researchers across the world to support uptake of research evidence in policy-making. Prior to working for Parliament, Chandrika worked as a glaciologist at the British Antarctic Survey from 1998-2002. She has a PhD in High Energy Physics from Oxford University.

The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is responsible for the conservation of Antarctic marine ecosystems, yet extreme events - such as marine heatwaves and storms - are disrupting these ecosystems, posing new challenges to CCAMLR's ecosystem-based fisheries management approach. While some progress has been made by CCAMLR in considering extreme events, practical action is lacking. This review examines current progress in integrating extreme events into ecosystem-based management and identifies critical gaps in understanding, predicting and responding to such events. Recent studies have demonstrated that extreme events significantly impact species' habitats, distribution, and key demographic factors such as breeding success and mortality rates, making it essential to incorporate the consideration of such events into management strategies. Drawing on recommendations from a recent CCAMLR workshop, we proposed improved approaches to data collection and analysis, including the development of predictive models that enhance understanding of the impacts of extreme events. We explore the integration of extreme event data into fisheries monitoring, the need for adaptive management policies and prioritisation of long-term resilience, and the strengthening of collaboration among relevant scientific disciplines, stakeholders, and policymakers. A more comprehensive and dynamic approach that explicitly incorporates extreme events is crucial for ensuring the sustainable management of Antarctic marine ecosystems amid the challenges posed by climate change.

Dr Rachel Cavanagh

British Antarctic Survey, UK

Dr Rachel Cavanagh

British Antarctic Survey, UK

Dr Rachel Cavanagh is an Ecosystem Scientist at the British Antarctic Survey (BAS) with over two decades of experience encompassing interdisciplinary research, international programme leadership and technical advice for policy. Rachel holds a BSc in Applied Zoology and PhD in Population Ecology, and before joining BAS was Executive Officer of the International Union for Conservation of Nature (IUCN) Shark Specialist Group, leading efforts in global shark conservation and management. With a strong interest in the role of science in informing policy, Rachel's current research is focused on integrating climate change considerations into marine conservation and management. Rachel is a Scientific Advisor on the UK delegation to the Commission for the Conservation of Antarctic Marine Living Resource (CCAMLR), Co-Chief Officer of the Scientific Committee on Antarctic Research (SCAR) Flagship Scientific Research Programme Near-term Variability and Prediction of the Antarctic Climate System and serves on SCAR's Standing Committee on the Antarctic Treaty System.

Antarctica and the Southern Ocean provide for the world’s human population in multiple ways. Effective governance, with adequate environmental protection, is required to sustain these services and functions, including climate regulation and the maintenance of global ocean health and productivity. Such governance must be underpinned by scientific evidence, much of which requires observational data from Antarctica and the Southern Ocean. The Southern Ocean Observing System (SOOS) is the leading international organisation coordinating the collection and dissemination of observational data from the Southern Ocean. By collaborating across geographic, disciplinary and career stage boundaries, SOOS enables and mobilises the international community to collect and use high-quality Southern Ocean data for scientific, policy and educational purposes.

In this talk, I will outline the work that SOOS does in various policy spheres, including the Antarctic Treaty System, the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), the UN Framework Convention on Climate Change (UNFCCC) and UN Oceans. I will highlight the importance of robust and representative data in underpinning evidence-based decision making and of taking an equitable and inclusive approach in these international contexts. I will also discuss some of the challenges and opportunities for scientists of all career stages engaging in the policy space.

Dr Sian Henley

University of Edinburgh, UK

Dr Sian Henley

University of Edinburgh, UK

Dr Sian Henley is a Reader in Marine Science at the University of Edinburgh. She has a diverse range of research interests from climate and environmental change in the polar oceans to climate change impacts on children worldwide. Her research in the polar regions focuses on marine biogeochemistry and ecosystem functioning in both the Arctic and the Antarctic. Sian is active at the science-policy interface with a focus on Earth’s polar regions, making significant contributions to high-profile policy events such as the UN Climate Change Conferences COP26, COP27, COP28 and COP29 and the UN Ocean Conferences 2022 and 2025. Sian currently serves on the International Advisory Committee for the UN Ocean Decade Coordination Centre for the Southern Ocean Region, the UK National Committee for the Antarctica In Sync initiative, and was Co-Chair of the Southern Ocean Observing System (SOOS) 2022-2025. In addition to her wide-ranging research, Sian is a passionate lecturer, educator and communicator on issues around climate and environmental change and sustainable development.

Antarctic climate change affects the cryosphere as well as terrestrial and ocean life. Cryosphere impacts have global implications, by affecting the global ocean conveyor and shaping sea level rise. Research on organisms and ecosystems allows testing unifying principles of effect and their specific implications for Antarctic life. Climate change drivers in the ocean entail ocean warming, acidification and loss of oxygen due to warming and enhanced stratification. These drivers individually and together affect ocean life. While some approaches compare the effect sizes of these individual drivers, other approaches strive to develop an integrative view for more realistic ecological projections. Temperature emerges as a master variable shaping the functioning of all life forms. Such functioning depends on the thermal performance curve as a reaction norm characterizing individual species and their life stages. Those principles also explain species vulnerability to climate change. Overlapping thermal performance curve as a reaction norm characterizing individual species and their life stages. Those principles also explain species vulnerability to climate change. Overlapping thermal performance curves characterize the temperature range at which species can co-exist at ecosystem level. The talk will put the drivers and their impacts into context and address how ocean oxygen and CO2 play a role in the thermal tolerance and performance of marine animal species. These findings indicate high vulnerability of Antarctic systems and have implications for Antarctic policy. Current debate focuses on conservation and associated spatial planning needs. Increasing economic and tourism pressures emphasize the need for future considerations of wider concepts such as Climate Resilient Development.

* Intergovernmental Panel on Climate Change, IPCC; Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, IPBES; German Advisory Council on Global Change, WBGU

Professor Hans-Otto Pörtner

Alfred Wegener Institute, Germany

Professor Hans-Otto Pörtner

Alfred Wegener Institute, Germany

Hans-Otto Pörtner is a researcher in marine ecophysiology and the impacts of climate change. He has established theory and evidence on effects of climate warming, ocean acidification, and hypoxia on marine animals and ecosystems. His efforts focus on linking biogeography and ecosystem functioning to molecular, biochemical and physiological mechanisms shaping organism tolerance and performance. In October 2015 he was elected Co-Chair of IPCC Working Group II for its 6th assessment cycle. He is an elected member of the European Academy of Sciences, the German Advisory Council on Global Change and a Web of Science highly cited researcher 2018 award.

Sea-level rise associated with warming of the climate system is characterised by long-term commitment for many centuries, with future ice sheet changes the dominant threat on these timescales. The current Environment Agency climate change allowances for UK sea-level rise by 2125 range from 1.0-1.6, depending on geographic region, with an H++ value of 1.9m for risk-averse decision makers (eg nuclear energy sector, long-lived infrastructure planning). However, poorly understood ice sheet instability processes in Antarctica could lead to global and UK sea-level rise of more than 10m by 2300, as highlighted in the most recent assessment report of the Intergovernmental Panel on Climate Change (IPCC). Even in the absence of such processes being triggered, the UK coastline is expected to see at least 1-2m of local sea-level rise by 2300, with strong regional variations. Given the large uncertainty in both global and UK sea-level rise, we present a flexible sea-level storylines framework that is designed to promote a risk-based assessment of future adaptation options in coastal planning. By combining our framework with a state-of-the-art UK flood model, we generate a first-order picture of the scale of the adaptation challenge under a range of future sea-level rise outcomes. Uncertainty in future projections, particularly those associated with Antarctic ice sheet instability processes, provide strong motivation for detailed observational monitoring and development of early warning indicators.

Dr Matt Palmer

Met Office Hadley Centre, UK

Dr Matt Palmer

Met Office Hadley Centre, UK

Dr Matt Palmer is a Science Fellow at the Met Office Hadley Centre and Associate Professor in Climate Science at the University of Bristol. His expertise includes observations and projections of sea level change, Earth's energy budget and ocean subsurface observations. Matt led the sea level work for the UK National Climate Projections (UKCP18) that included development of pioneering multi-century sea-level projections in response to stakeholder needs. He has worked on a variety of international projects providing sea level projections and observational analysis for other parts of the world. Matt was a Lead Author on the latest Intergovernmental Panel on Climate Change report (IPCC AR6) where his contributions included leading the assessment of the global energy and sea level budgets.