Drivers and Effects of Fluctuations in sea Ice in the ANTarctic

Despite global warming, Antarctic sea ice expanded during most of the first four decades of satellite observations. However, in 2016 the Antarctic sea ice area plummeted, in a change far outside the range of previously observed variability. Neither the increasing trend nor the rapid decline are authentically simulated by climate models, casting doubt on their ability to represent associated processes including Southern Ocean heat and carbon uptake, melting of the Antarctic Ice Sheet, and many other aspects of the Southern Hemisphere climate.

Research Topics

Determination of causes of Antarctic sea ice variability

Work Package 1: The aim of work package 1 is to determine the causes of variability in Antarctic sea ice extent, and particularly rapid changes such as occurred in 2016 in the Weddell Sea. We will utilise a range of observations, techniques and methods to better quantify sea ice extent, area and volume, and investigate how this is impacted by various atmospheric and oceanic drivers.  

Improving modelling capabilities

RQ2. Can these processes be represented reliably in models to reproduce observed changes in Antarctic sea ice extent? We will use the atmosphere, sea ice and ocean observations in WP1 to calibrate and test model physics linked to Antarctic sea ice variability.

Impacts and predictability

Research topic 3 will extend DEFIANT’s scope to cover longer timescales and broader geographical regions. We will achieve this aim using an interdisciplinary approach, combining CMIP6 analysis, new simulations with the NEMO-SI3 and HadGEM3-GC5 models, and analysis of observations and state estimates.

Synthesis and dissemination

The strategic objective for this WP is to ensure (i) the knowledge gained is promoted and disseminated to the widest audience; (ii) training and education activities are provided; (iii) a White Paper on the State of Antarctic sea ice is delivered to relevant stakeholders and decision makers.


The Specific Objectives (SOs) of DEFIANT map one-to-one onto the RQs of HTD: Drivers and climate implications of recent rapid loss of Antarctic sea ice, with an additional synthesis objective:


Identify the atmospheric and oceanic processes that caused the 2016 rapid decline in Antarctic sea ice.


Improve the physical representation of the processes responsible for historical changes in Antarctic ice, ocean, and atmosphere models, including the decadal growth and recent collapse.


Identify the short-term (<10 years) effect of the sudden decrease in Antarctic sea ice on global oceanic circulation patterns using model simulations with improved physics.


Combine historical observations and model predictions to assess whether enhanced variability and loss of sea ice constitute a new normal and examine the implications for exchange and redistribution of heat and CO2 over decadal timescales.


Synthesise advances from above SOs, disseminate knowledge gained and deliver new climate modelling tools.