Antarctic sea ice is more than just a platform for penguins. The sea ice’s high reflectivity influences the whole Earth’s climate, and the ice is a key habitat for underwater as well as above-water ecosystems. Antarctic sea ice cover is becoming much more variable as the climate changes; there has been a string of record high years followed by years with record low areas of ice. Edward Doddridge and colleagues studied these record-low years, which they expect will become more common as the climate warms. Using observations and modeling, the authors find a host of effects of ultra-low ice years, including warming of the Southern Ocean, increased ice-shelf calving, and stronger phytoplankton blooms. Low sea-ice area negatively affects krill, small crustaceans that feed and find refuge beneath the sea ice, as well as fatty silverfish. Reductions in krill and fish populations affect their predators, including whales. Penguins and seals that use ice floes to moult, nest, or grow new fur will struggle if low sea ice continues for many years. Finally, a reduction in the area of firm ice affixed to the land makes it more difficult for humans to operate on the continent, affecting Antarctic science. According to the authors, additional research is needed to fully understand the impacts of low Antarctic sea ice on the physical, ecological, and societal systems within and around Antarctica, and they call, in particular, for reliable, year-round, long-term measurements of sea-ice thickness.
PNAS Nexus
Impacts of Antarctic summer sea-ice extremes
1-Jul-2025