Antarctic sea ice has many crucial roles in the global climate system through its high albedo (reflectivity) and by acting as a barrier to the exchange of gases between the ocean and atmosphere. Sea ice also has a key role in the formation of dense, salty water masses and consequently driving global ocean circulation, as well as providing a vital habitat for many Antarctic organisms. 

In the past, the global climate has oscillated between cold ‘glacial’ and warm ‘interglacial’ states, with the last 130,000 years covering a full cycle back to the last interglacial period. Investigating how Antarctic sea ice has responded to a changing climate across a full interglacial to glacial cycle, and the impacts on other areas of the global climate system is important in understanding both past and future climate transitions.

In a new publication, “Compilation of Southern Ocean sea-ice records covering the last glacial-interglacial cycle,” Chadwick and colleagues, members of the Past Global Changes (PAGES) Global Research Network of Future Earth, compiled a series of long duration sea-ice records from across the Southern Ocean to investigate the patterns and timing of sea-ice advances and retreats in different areas of the Southern Ocean during the last 130,000 years. These records are mainly reconstructed from cores of marine sediment, where the fossils of a group of siliceous microalgae – diatoms – act as a proxy for the past sea-ice conditions in a region. Specifically, the abundance of certain diatom species preserved in seafloor sediments can indicate the amount and duration of winter sea ice that was present above that location, and by analysing diatom abundances down through a sediment core the sea-ice conditions can be reconstructed further back in time.

Overall, all records indicate the same general pattern of sea ice for the last 130,000 years, with the most sea-ice during the glacial period and the least during the interglacial period. However, the short-term patterns and magnitude of sea ice changes varied by region. The areas at the outflows of Southern Ocean gyres, large circular rotating ocean currents, displayed the greatest sensitivity to changing climate, with the largest and fastest changes in the sea-ice extent. It is likely therefore that under the current warming climate it is these areas that will see the greatest and earliest reductions in sea-ice cover, with knock-on consequences for both the climate system and the ecology in these areas.

PAGES (Past Global Changes) supports science aimed at understanding the Earth’s past environment in order to make predictions for the future.

PAGES scope of interest includes the physical climate system, biogeochemical cycles, ecosystem processes, biodiversity, and human dimensions, on different time scales that reach back centuries to hundreds of thousands of years. PAGES facilitates activities that address past changes in the Earth System in a quantitative and process-oriented way in order to improve predictions of future climate and environment, and inform strategies for sustainability.

Learn about other Global Research Networks.