Arctic sea ice recorded its minimum annual extent on September 19, 2023. It is the sixth lowest recorded by satellite, according to researchers at NASA and the National Snow and Ice Data Center (NSIDC).
Meanwhile, Antarctic sea ice reached its lowest maximum extent on record on September 10, at a time when it should have grown at a much faster rate during the darker, colder months.

Scientists are watching seasonal and annual variations because sea ice shapes Earth’s polar ecosystems and plays an important role in global climate. Researchers at NSIDC and NASA use satellites to measure sea ice as it melts and refreezes. They monitor sea ice extent, which is defined as the total ocean area in which the fraction of ice cover is at least 15%.

Between March and September 2023, the extent of Arctic ice shrank from 5.64 million square miles (14.62 million square kilometers) to 1.63 million square miles (4.23 million square kilometers).

It is about 770,000 sq mi (1.99 million sq km) below the 1981–2010 minimum average of 2.4 million sq mi (6.22 million sq km). The amount of sea ice lost was enough to cover the entire mainland.

Sea ice around Antarctica has reached its lowest point its maximum winter extent on September 10, 2023, at 6.5 million square miles (16.96 million square kilometers).

That’s 398,000 square miles (1.03 million square kilometers) below the previous record low reached in 1986 — a difference roughly the size of Texas and California combined. The average maximum area between 1981 and 2010 was 7.22 million square miles (18.71 million square kilometers).

Nathan Kurtz, laboratory chief of NASA’s Cryospheric Sciences Laboratory at the agency’s Goddard Space Flight Center in Greenbelt, Maryland, said that as the Arctic warms about four times faster than the rest of the planet, the ice is also getting thinner. “Thickness at the end of the growing period largely determines the survivability of sea ice. New research uses satellites such as NASA’s ICESat-2; (Ice, Cloud and land Elevation Satellite-2) to monitor how thick the ice is throughout the year.”

Kurtz said long-term measurements of sea ice are critical to studying what’s happening in real time at the poles. “At NASA we’re interested in making cutting-edge measurements, but we’re also trying to connect them to the historical record to better understand what’s driving some of these changes that we’re seeing.”

Scientists are working to understand the cause of the small growth of Antarctic sea ice, which could be due to a combination of factors such as El Nino, wind patterns and rising ocean temperatures.

Before 2014, the ice surrounding the continent was growing slightly at about 1% per decade to start counting down before reaching an all-time low today.

Melting sea ice at both poles amplifies the warming because while sea ice reflects most of the Sun’s energy back into space, open ocean water absorbs 90% of it. With larger areas of the ocean exposed to solar energy, more heat can be absorbed, which warms the ocean waters and further slows the growth of sea ice