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Antarctica’s sea ice has declined to record-low levels in recent years. All four of the continent’s lowest recorded sea-ice extents have occurred within the past four years.
Operative Information Center-OMM reports that satellite monitoring of Antarctic sea ice has been conducted since 1979.
According to this year’s data, the sea-ice cover reached a maximum of 17.59 million square kilometers on Sept. 14. That is about 1 million square kilometers below the average maximum, equivalent to roughly twice the area of Spain.
Walt Meier, an expert at the National Snow and Ice Data Center at the University of Colorado, said researchers were not rushing to announce the maximum because variability remains high at this stage of the Antarctic sea-ice cycle. However, he said the ice level had declined since Sept. 14 and that the maximum had likely been reached.
Antarctica’s sea ice melts during the summer, falling below 2 million square kilometers in February, then expands again through the winter to cover more than 17 million square kilometers in September. Records for unusually low levels in both winter and summer in recent years have raised concerns that global warming is accelerating ice loss.
Ariaan Purich, a Southern Ocean specialist at Monash University in Melbourne, said sea-ice maximums had been at record-low levels during each of the past four winters. According to Purich, this is no longer a one-off event, and sea ice is not covering the same area of the ocean as it did previously.
Temperatures on the Antarctic Peninsula were 20 degrees Celsius above normal in June. Scientists have highlighted the emergence of an open-ocean area the size of France in a region where ice would normally be expected.
Although sea ice was expected to expand steadily in early August, major ice loss occurred across much of the Amundsen Sea in the South Pacific. Purich said the decline could be linked to wind changes associated with the “El Nino” climate pattern observed in the tropical Pacific.
Phil Reid, an expert at the Australian Bureau of Meteorology who monitors Antarctic conditions, said “El Nino” changes the paths of storm systems around Antarctica. This can cause some storms to remain over the same area and stir the sea ice from below.
Reid said a similar situation could occur even without “El Nino.” He noted that although the atmosphere plays a role, water temperature is ultimately decisive: when the water is warmer, the area covered by sea ice decreases.
The melting of sea ice does not directly raise sea levels because the ice is already floating on the water. However, the loss of sea ice can expose ice shelves more directly to the ocean, potentially weakening them.
Ice shelves slow the movement of glaciers and the continent’s vast ice sheet toward the ocean. If that ice sheet reaches the ocean, global sea levels could rise by several meters.
Sea ice provides habitat for algae and krill, which are key elements of the continent’s food chain. Unstable ice conditions also create additional risks for several species, including emperor penguins, which breed and raise their chicks on the ice.
Will Hobbs, an Antarctic sea-ice specialist at the University of Tasmania, said the ice cover had declined faster than normal after reaching its maximum earlier this month. He said another low-ice summer could significantly increase concerns about impacts on ice shelves.
Hobbs stressed that scientists are still studying the sensitivity of the global climate system to sea-ice loss, but said the system was changing faster than previously thought.
