As Antarctic sea ice continues its dramatic decline, we need more measurements and much better models

A layer of frozen seawater that surrounds the Antarctic continent, sea ice cycles from maximum coverage in September to a minimum in February. The summer minimum has also continued to diminish, with three record low summers in the past seven years.

Some scientists have suggested this year could mark a regime shift for Antarctic sea ice. The consequences could be far-reaching for Earth's climate, because sea ice keeps the planet cooler by reflecting solar energy back into the atmosphere and insulating the ocean. Its formation also generates cold, salty water masses that drive global ocean currents.

The annual freeze-thaw cycle of Antarctic sea ice is one of Earth's largest seasonal changes, but is a major challenge for climate models to predict accurately.

Since the 1970s, satellites have been tracking a quantity known as "sea ice extent," which is the total surface area where at least 15% is covered by sea ice.

This September, it reached a satellite-era record low for this time of year. The previous year, after tracking much lower than the median all winter, Antarctic sea ice extent made a late rally and was 18.3 million square kilometers at its maximum by September 2022, around 2% below the 1981–2010 median.

Credit: Jan Lieser, CC BY-SA

Antarctic sea ice has been in sharp decline in recent years and its winter maximum reached a record low this year. Credit: Ariaan Purich, CC BY-SA

Emperor penguins need sea ice to breed. In four out of five breeding sites in one region of sea ice loss, no chicks survived. Credit: Pat James/Australian Antarctic Division, CC BY-SA

At the time of its September maximum, Antarctic sea ice extent was nearly 9% below the 1981-2010 median for that time of year. Credit: Glenn Jacobson/Australian Antarctic Division, CC BY-SA