Record-low Antarctic sea ice in 2023 increased ocean heat loss and storms – Andrew Meijers

Declining Antarctic sea ice cover is generating unprecedented ocean heat loss to the atmosphere and more storms, according to a new study led by the UK’s National Oceanography Centre (NOC) and contributing to BIOPOLE outputs. The study, published in the journal Nature, focused on the record low Antarctic winter sea ice cover in 2023 and provides the first clear picture of the impacts of the disappearing sea ice. 

Using data from the atmospheric layer just above the ocean surface, it found that ice concentrations in the Weddell, Bellingshausen and Ross seas was reduced by up to 80% and accompanied by an unprecedented doubling of mid-winter ocean heat loss. Also, there was a phase shift in the time of peak heat loss from late April to mid-June, with weaker than normal heat loss in the austral autumn. The winter surface-heat-loss intensification was found to be accompanied by substantial changes on both sides of the ocean–atmosphere interface. These include increases in both atmospheric-storm frequency and surface-heat-loss-driven dense water formation. 

The study also warns of potentially far-reaching impacts on the deeper ocean circulation, due to the heat loss making Antarctic surface waters denser than previously seen.  Lead author Professor Simon Josey says the results point to an urgent need to use state-of-the-art ocean and climate simulations to better understand the broader impacts of Antarctic sea ice loss. 

“Based on our study, years of low sea ice like this will continue to have more storms and greater changes to ocean properties that could impact the wider ocean circulation. Repeated low ice cover conditions in subsequent winters will strengthen these impacts and may result in profound changes further afield, including the Tropics and Northern Hemisphere.” 

Co-author Dr Andrew Meijers, from the British Antarctic Survey, explains further, “The location of this new denser surface water is relatively far from the sites at the Antarctic shelf where the densest and deepest waters of the global ocean are formed.  However, this cooling and subsequent sinking of waters previously covered by sea ice has the potential to release deeper warm waters that would normally be kept away from the ice by an insulating surface layer. In turn this has the potential for increasing sea ice melt in future years.” 

“Further analysis is urgently needed to understand these processes and their complex feedbacks, and determine how the massive decline of winter sea ice in 2023, and again this year, will impact the Southern Ocean circulation. This is key to understanding the climatically critical ocean uptake of atmospheric heat and carbon, and the rate of melt of the Antarctic continent.” 

Read the full study in Nature here. 

The author of this article Andrew Meijers (British Antarctic Survey)