Arctic sea ice growth was slower than average through most of the month, but with extent slightly declining towards the end of the month. Antarctic sea ice extent returned to near-record daily lows after a brief excursion out of the lowest five years.
Overview of conditions
The year 2024 began with an average January Arctic sea ice extent of 13.92 million square kilometers (5.37 million square miles), the twentieth lowest in the 45-year satellite record (Figure 1a). During the month, extent increased by 1.09 million square kilometers (421,000 square miles), which was slower than the 1981 to 2010 average increase of 1.33 million square kilometers (514,000 square miles) (Figure 1b). Extent actually declined for a few days at the end of the month. During the growth season, such short-term declines are not unusual and are caused by weather systems that temporarily melt or push back areas of the extensive ice edge at this time of year.
Extent was low in the Barents Sea with open water extending offshore of the northwest tip of Novaya Zemlya, as well as in the Gulf of St. Lawrence. Elsewhere, extent was near average.
Conditions in context
Overall, it was relatively warm over the Arctic Ocean during January (Figure 2a). Air temperatures at the 925 millibar level (about 2,500 feet above sea level) were up to 6 degrees Celsius (11 degrees Fahrenheit) above average over the central Arctic Ocean and the Canadian Archipelago. Air temperatures in the Bering Sea were 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) above average. It was slightly cooler than average over the East Siberian Sea.
The sea level pressure pattern was characterized by low pressure over the Barents and Bering Seas and a saddle of relatively high pressure extending from Eastern Siberia across the Arctic Ocean into northwestern Canada (Figure 2b). Overall, pressure gradients were not particularly strong, indicating slack winds.
January 2024 compared to previous years
The downward linear trend in Arctic sea ice extent for January over the 45-year satellite record is 41,000 square kilometers (16,000 square miles) per year, or 2.8 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, January has lost 1.73 million square kilometers (668,000 square miles) of ice since 1979. This is equivalent to the 2.5 times the size of state of Alaska or the country of Iran. However, the relatively high ice extent for January 2024 is notable.
Arctic sea ice thickness update
Sea ice thickness can be estimated from satellite-borne altimeters. Currently, two altimeters are providing thickness estimates over the Arctic Ocean. One is the NASA Ice, Cloud, Land elevation Satellite 2 (ICESat-2), a laser altimeter; ICESat-2 data products are archived at the NASA Snow and Ice Distributed Active Archive Center (DAAC) at NSIDC. The other is the European Space Agency’s (ESA’s) CryoSat-2, a radar altimeter. In combination with estimates for thin regions from the ESA Soil Moisture Ocean Salinity (SMOS) satellite, CryoSat-2 provides daily updated weekly average thickness (Figure 4a).
As Arctic sea ice extent starts approaching its maximum, ice thickness can provide an indication of the state of the ice cover. The most recent (mid-December 2023) thickness analysis from the ESA SMOS & CryoSat-2 Sea Ice Data Product Processing and Dissemination Service at Alfred Wegener Institute indicates up to 1.25 meters (4.1 feet) thicker ice than the 2011to 2023 average over the Siberian side of the Arctic, with ice on the North American side up to 1.25 meters (4.1 feet) thinner than average (Figure 4b). This suggests that there may be a slower melt out of ice in the Siberian coastal seas, but perhaps faster in the Beaufort Sea.
Antarctic sea ice
Sea ice extent in the Antarctic started the year at 6.37 million square kilometers (2.46 million square miles), or sixth lowest in the satellite record for January 1. As the melt season continued in the Southern Hemisphere, a rapid decline in daily extent led to it ending the month at 2.58 million square kilometers (996,000 square miles), tying for second lowest with 2017 for that date. Antarctic sea ice extent for January overall averaged 3.96 million square kilometers (1.53 million square miles), tying for fourth lowest extent with 2022. Extent was particularly low in the Ross, Bellingshausen, and Amundsen Seas, but has been near average in the Weddell Sea. Little ice remains in the East Antarctic sectors.
A team from the University of Colorado and the Instituto Argentino Antartico are en route to the Antarctic Peninsula and the Larsen B embayment. This region’s glaciers have become more active again after an area of multiyear fast ice broke away in 2022.