DEFIANT: Drivers and Effects of Fluctuations in sea Ice in the ANTarctic
Lead Research Organisation:
NERC BRITISH ANTARCTIC SURVEY
Department Name: Science Programmes
Abstract
Since the start of the industrial revolution the CO2 concentration in the atmosphere has steadily risen. Scientists have confirmed that the recent loss of Arctic sea ice in summer directly follows this rise in human-induced CO2 emissions, reducing from about 7 million km2 of Arctic sea ice in the late 1970s to around 3.5 million km2 in the 2010s.
While climate models suggest Antarctic sea ice extent should also reduce in response to rising CO2, satellite observations reveal that during 1979-2015 the opposite was in fact true. The trend in Antarctic sea ice extent has been a small increase of approximately 1.5% per decade. In 2016, however, this increase was abruptly interrupted by a dramatic reduction in sea ice extent that was far outside the previously observed range. Since the extreme event in 2016, Antarctic sea ice extent has almost returned to its pre-2016 values, highlighting the significant variability in Antarctic sea ice conditions that can occur from one year to the next. These variations in sea ice are important to the whole Earth's climate, because they affect the melting of the glacial Antarctic Ice Sheet, and the capture of atmospheric heat and CO2 by the Southern Ocean.
The recent extreme swings in Antarctic sea ice extent, and the challenge of accurately predicting, understanding and modelling them, emphasise the need to:
(i) increase our knowledge of the processes that drive Antarctic sea ice variations, including extreme events, and
(ii) understand the drivers and climate implications of Antarctic sea ice loss over different time-scales, from weeks to decades.
To address this knowledge gap requires a significant research programme, one that takes year-round observations, including throughout the harsh Antarctic winter, and is effective in improving the underlying processes in the latest computer climate models.
Our project, known as DEFIANT (Drivers and Effects of Fluctuations in sea Ice in the ANTarctic), will embark on one of the most ambitious observational campaigns aimed at understanding Antarctic sea ice variability. Scientific measurements from the German research ship Polarstern, the UK's new polar research ship Sir David Attenborough, the British Antarctic Survey's Rothera research station, aircraft overflights and satellites will work seamlessly together with cutting-edge robotic technologies (including the underwater vehicle Boaty McBoatface and a suite of on-ice buoys) to provide us with comprehensive, year-round measurements of atmosphere, sea ice and ocean. The knowledge gained from these observations will enable our team to develop new ocean and climate models in order to more accurately represent Antarctic sea ice processes.
The analysis of these improved models will allow us to better understand the underlying drivers of the sudden decrease in Antarctic sea ice, determine the impact of these extreme events on the global ocean circulation, and forecast the implications for the movements of heat and CO2 through the climate system. By developing new observations, new satellite records, and new models, DEFIANT will deliver a major advance in our understanding of the Antarctic sea ice system and its wider impacts on global climate.
While climate models suggest Antarctic sea ice extent should also reduce in response to rising CO2, satellite observations reveal that during 1979-2015 the opposite was in fact true. The trend in Antarctic sea ice extent has been a small increase of approximately 1.5% per decade. In 2016, however, this increase was abruptly interrupted by a dramatic reduction in sea ice extent that was far outside the previously observed range. Since the extreme event in 2016, Antarctic sea ice extent has almost returned to its pre-2016 values, highlighting the significant variability in Antarctic sea ice conditions that can occur from one year to the next. These variations in sea ice are important to the whole Earth's climate, because they affect the melting of the glacial Antarctic Ice Sheet, and the capture of atmospheric heat and CO2 by the Southern Ocean.
The recent extreme swings in Antarctic sea ice extent, and the challenge of accurately predicting, understanding and modelling them, emphasise the need to:
(i) increase our knowledge of the processes that drive Antarctic sea ice variations, including extreme events, and
(ii) understand the drivers and climate implications of Antarctic sea ice loss over different time-scales, from weeks to decades.
To address this knowledge gap requires a significant research programme, one that takes year-round observations, including throughout the harsh Antarctic winter, and is effective in improving the underlying processes in the latest computer climate models.
Our project, known as DEFIANT (Drivers and Effects of Fluctuations in sea Ice in the ANTarctic), will embark on one of the most ambitious observational campaigns aimed at understanding Antarctic sea ice variability. Scientific measurements from the German research ship Polarstern, the UK's new polar research ship Sir David Attenborough, the British Antarctic Survey's Rothera research station, aircraft overflights and satellites will work seamlessly together with cutting-edge robotic technologies (including the underwater vehicle Boaty McBoatface and a suite of on-ice buoys) to provide us with comprehensive, year-round measurements of atmosphere, sea ice and ocean. The knowledge gained from these observations will enable our team to develop new ocean and climate models in order to more accurately represent Antarctic sea ice processes.
The analysis of these improved models will allow us to better understand the underlying drivers of the sudden decrease in Antarctic sea ice, determine the impact of these extreme events on the global ocean circulation, and forecast the implications for the movements of heat and CO2 through the climate system. By developing new observations, new satellite records, and new models, DEFIANT will deliver a major advance in our understanding of the Antarctic sea ice system and its wider impacts on global climate.
Organisations
- NERC BRITISH ANTARCTIC SURVEY (Lead Research Organisation)
- University of California, Los Angeles (UCLA) (Collaboration)
- Alfred-Wegener Institute for Polar and Marine Research (Collaboration)
- Meteorological Office UK (Collaboration)
- Oregon State University (Collaboration)
- National Centre for Polar and Ocean Research (Collaboration)
- Ludwig Maximilian University of Munich (LMU Munich) (Collaboration)
- Norwegian Meteorological Institute (Collaboration)
- European Space Agency (Collaboration)
- Australian Antarctic Division (Collaboration, Project Partner)
- University of Manitoba (Collaboration)
- Norwegian Metrological Institute (Project Partner)
- MET OFFICE (Project Partner)
- Alfred Wegener Institute (Helmholtz) (Project Partner)
- Oregon State University (Project Partner)
- European Space Agency (International) (Project Partner)
- Southern Ocean Observing System (SOOS) (Project Partner)
- University of Manitoba (Project Partner)
- University of California Los Angeles (Project Partner)
- Princeton University (Project Partner)
- University of Huddersfield (Project Partner)
- National Centre for Polar and Ocean Res (Project Partner)
Publications

Diamond R
(2024)
CMIP6 Models Rarely Simulate Antarctic Winter Sea-Ice Anomalies as Large as Observed in 2023
in Geophysical Research Letters

Gilbert E
(2024)
2023's Antarctic sea ice extent is the lowest on record
in Weather


Jena B
(2024)
Occurrence of an unusual extensive ice-free feature within the pack ice of the central Weddell Sea, Antarctica
in npj Climate and Atmospheric Science

Meredith MP
(2023)
Tracing the impacts of recent rapid sea ice changes and the A68 megaberg on the surface freshwater balance of the Weddell and Scotia Seas.
in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

Rogers M
(2024)
Sea ice detection using concurrent multispectral and synthetic aperture radar imagery
in Remote Sensing of Environment


Turner J
(2022)
Record Low Antarctic Sea Ice Cover in February 2022
in Geophysical Research Letters

Willatt R
(2023)
Retrieval of Snow Depth on Arctic Sea Ice From Surface-Based, Polarimetric, Dual-Frequency Radar Altimetry
in Geophysical Research Letters
Description | Award still on active. Key findings will be reported at end of project |
Exploitation Route | Award still on active. Outcomes will be reported at end of project |
Sectors | Environment |
Title | Historical Occurrence of Antarctic Icebergs within Mercantile Shipping Routes and the Exceptional Events of the 1890s |
Description | This is the dataset created for the Journal of Glaciology paper "Historical Occurrence of Antarctic Icebergs within Mercantile Shipping Routes and the Exceptional Events of the 1890s" by Robert Headland, Nick Hughes and Jeremy Wilkinson (doi:10.1017/jog.2023.80). We have endeavoured to make the data as accessible as possible by providing it in a range of formats. Please see the README.pdf for a detailed description of the files, and the paper for the dataset. Version 1.1 contains additional reports from newspaper archives. |
Type Of Material | Database/Collection of data |
Year Produced | 2023 |
Provided To Others? | Yes |
URL | https://zenodo.org/doi/10.5281/zenodo.7728593 |
Description | AAD |
Organisation | Australian Antarctic Division |
Country | Australia |
Sector | Public |
PI Contribution | Staff time for WP1 tasks |
Collaborator Contribution | Staff time for WP1 tasks |
Impact | ongoing |
Start Year | 2022 |
Description | AWI Polarstern Cruise |
Organisation | Alfred-Wegener Institute for Polar and Marine Research |
Country | Germany |
Sector | Private |
PI Contribution | Between Feb and May 2022 three DEFIANT scientists participated in Antarctic field research on the German research vessels Polarstern |
Collaborator Contribution | Freeze-up is the season in the Antarctic where substantial changes occur in the upper-ocean, i.e. the warm-fresh summer stratification must be overcome to allow ice formation to progress. Thus, monitoring autumn mixing rates, heat fluxes, sea ice/snow mass balance and upper-ocean properties are essential for the DEFIANT project. Collaboration with AWI's HAFOS (Hybrid Antarctic Float and Ocean Observatory) project provided broad access to the Weddell Sea during freeze-up 2022, via the ship Polarstern. In addition to HAFOS' comprehensive ocean observations, the DEFIANT team also quantified large-scale survey of microstructure temperature variance (Chi-pods) and freshwater content via oxgyen isotope analysis. We also performed on-ice and helicopter surveys of snow depth and scattering using Ku/Ka band radar; with accompanying snow and sea ice properties and under-ice light measurements. Two ice-tethered assets were deployed. |
Impact | Outcomes still in progress. |
Start Year | 2022 |
Description | ESA |
Organisation | European Space Agency |
Department | Science and Operations Department |
Country | France |
Sector | Academic/University |
PI Contribution | ESA: change orbit of Cryosat2, supply airborne sensors and DEFIANT Advisory Board duties |
Collaborator Contribution | ESA: change orbit of Cryosat2, supply airborne sensors and DEFIANT Advisory Board duties |
Impact | ongoing |
Start Year | 2022 |
Description | LMU Munich |
Organisation | Ludwig Maximilian University of Munich (LMU Munich) |
Country | Germany |
Sector | Academic/University |
PI Contribution | WP1 sea ice and freshwater; WP2/3 Model integration |
Collaborator Contribution | WP1 sea ice and freshwater; WP2/3 Model integration |
Impact | ongoing |
Start Year | 2022 |
Description | National Centre for Polar and Ocean Reseach |
Organisation | National Centre for Polar and Ocean Research |
Country | India |
Sector | Public |
PI Contribution | Staff time to contribute to WP1&3 tasks of DEFIANT |
Collaborator Contribution | Staff time to contribute to WP1&3 tasks = 6PM/year @ £5k/PM |
Impact | Ongoing |
Start Year | 2022 |
Description | Norwegian Meteorological Institute |
Organisation | Norwegian Meteorological Institute |
Country | Norway |
Sector | Public |
PI Contribution | AI input and assess AI output |
Collaborator Contribution | AI input and assess AI output |
Impact | ongoing |
Start Year | 2022 |
Description | Oregon State University |
Organisation | Oregon State University |
Country | United States |
Sector | Academic/University |
PI Contribution | WP1: analysis of turbulence data and loan of Chi-pod system for SDA and Polarstern cruises |
Collaborator Contribution | WP1: analysis of turbulence data and loan of Chi-pod system for SDA and Polarstern cruises |
Impact | ongoing |
Start Year | 2022 |
Description | UCLA |
Organisation | University of California, Los Angeles (UCLA) |
Country | United States |
Sector | Academic/University |
PI Contribution | Advisory Board member |
Collaborator Contribution | Advisory Board member |
Impact | ongoing |
Start Year | 2022 |
Description | UK Met Office |
Organisation | Meteorological Office UK |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Staff time, GC5 access, supercomputer costs, analysis |
Collaborator Contribution | Staff time, GC5 access, supercomputer costs, analysis |
Impact | ongoing |
Start Year | 2022 |
Description | University of Manitoba |
Organisation | University of Manitoba |
Country | Canada |
Sector | Academic/University |
PI Contribution | Rothera radar work & analysis |
Collaborator Contribution | Rothera radar work & analysis |
Impact | ongoing |
Start Year | 2022 |