Arctic sea ice cover retreated rapidly in July 2024, pushing the daily ice extent at the end of the month to the third lowest in the 46-year satellite record. Extensive low-concentration areas of sea ice are found in the Beaufort and East Siberian Seas, reaching 85 degrees North. In the Southern Ocean, sea ice is nearing the extreme low record extent set just last year, caused mostly by a large ice-free area in the southwestern Indian Ocean. As a result, global sea ice extent is at record lows for this time of year.
Overview of conditions
Ice loss during the month was greatest in the Kara and East Siberian Seas, Baffin Bay, Hudson Bay, and the Canadian Archipelago. Extensive low-concentration areas of sea ice are found in the Beaufort and East Siberian Seas (Figure 1c). A small patch of ice remains in western Hudson Bay, unusual for this time of year. There is still sea ice in both the northern and southern Northwest Passage routes according to passive microwave satellite data. On the Siberian side, the unusually packed area of sea ice south of Wrangel Island remains. Note that icebreakers and ice-capable liquefied natural gas (LNG) carriers routinely traverse the Northern Sea route along the Russian coast even with fairly thick sea ice.
Arctic sea ice retreat in July proceeded at a pace of 113,000 square kilometers (44,000 square miles) per day, faster than the 1981 to 2010 average pace of 87,000 square kilometers (34,000 square miles) per day and only slightly slower than the record pace of 117,000 square kilometers (45,000 square miles) per day set in 2020.
Conditions in context
Air temperatures at the 925 hPa level (approximately 2,500 feet above the surface) were near average overall, with several areas slightly below average. Relatively warm conditions prevailed over the Barents Sea with temperatures 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) above average. In the Kara Sea, temperatures were only 1 degree Celsius (2 degrees Fahrenheit) above average. Below average temperatures persisted in a wide swath extending from the East Siberian Sea, over the Beaufort Sea, and onto the Canadian Archipelago and northern Labrador with temperatures 2 degrees Celsius (4 degrees Fahrenheit) below average.
July featured a large area of low sea level pressure centered over Greenland and the Canadian Archipelago, but covering much of the Arctic Ocean.
July 2024 compared to previous years
Including 2024, the downward linear trend in Arctic sea ice extent for July is 66,000 square kilometers (25,000 square miles) per year, or 6.9 percent per decade relative to the 1981 to 2010 average. Based on the linear trend, since 1979, July has lost 2.95 million square kilometers (1.14 million square miles) of sea ice, which is roughly equivalent to 63,646 Olympic-sized swimming pools.
A new reconstruction of early twentieth century Arctic sea ice
A new reconstruction of Arctic sea ice back to 1901 has recently been published (Semenov et al., 2024). This new reconstruction generally compares well with other pre-satellite reconstructions: Sea Ice Back to 1850 (SIBT1850, Walsh et al., 2017) and the Hadley Centre Global Sea Ice and Sea Surface Temperature (HadISST) 1.1 (Rayner et al., 2003). However, the new data set shows more variability in the pre-1953 period. It also depicts lower September extents during the 1930s and 1940s in the western Arctic like the Beaufort and Chukchi Seas. While there are inherent uncertainties in sea ice reconstruction, results from this new approach support the conclusion that the satellite era trend in extent is outside of the range of natural variability. Nevertheless, caution is needed when interpreting these results because of sparse observations of sea surface and air temperatures.
Antarctic sea ice in 2024: Déjà vu
Antarctic sea ice extent in late July stood very close to the levels seen in 2023, which ended up with the lowest seasonal minimum and maximum in the satellite data record (Figure 5a). At the end of July 2024, sea ice was more than 2.1 million square kilometers (811,000 square miles) below the 1981 to 2010 average, and 190,000 square kilometers (73,000 square miles) above 2023. The July extent is particularly low in the southwestern Indian Ocean, where sea ice actually retreated during the month, despite it being mid-winter in the Southern Hemisphere (Figure 5b). This was a result of a pair of intense warm air intrusions, linked to strong high pressure near Enderby Land. Moreover, sea surface temperatures in the southwest Indian Ocean, south of South Africa, were 1 degree Celsius (2 degrees Fahrenheit) above average. Extent is near average in the Pacific Ocean sector and the Ross Sea, whereas in the western Weddell and Bellingshausen Seas, the ice is more extensive than average. Since July 31, sea ice extent has increased rapidly, with most of the growth in the easternmost Weddell Sea and the southwestern Indian Ocean sector.
Further reading
Rayner, N. A., D. E. Parker, E. B. Horton, C. K. Folland, L. V. Alexander, D. P. Rowell, E. C. Kent, and A. Kaplan. 2003. Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. Journal of Geophysical Research Atmospheres, 108(D14). doi:10.1029/2002JD002670.
Semenov, V. A., T. A. Aldonina, F. Li, N. S. Keenlyside, and L. Wang. 2024. Arctic sea ice variations in the first half of the 20th century: A new reconstruction based on hydrometeorological data. Advances in Atmospheric Sciences, 41(8), 1483-1495. doi:10.1007/s00376-024-3320-x.
Walsh, J. E., W. L. Chapman, F. Fetterer, and J. S. Stewart. 2019. Gridded Monthly Sea Ice Extent and Concentration, 1850 Onward, Version 2 [Data Set]. Boulder, Colorado USA. National Snow and Ice Data Center. doi:10.7265/jj4s-tq79.
Walsh, J. E., F. Fetterer, J. Scott Stewart, and W. L. Chapman. 2017. A database for depicting Arctic sea ice variations back to 1850. Geographical Review, 107(1), 89-107. doi:10.1111/j.1931-0846.2016.12195.x.