Arctic sea ice reached its minimum extent on September 16, 2021, at 4.72 million square kilometers

On September 16, Arctic sea ice likely reached its annual minimum extent of 4.72 million square kilometers (1.82 million square miles). The 2021 minimum is the twelfth lowest in the nearly 43-year satellite record. The last 15 years are the lowest 15 sea ice extents in the satellite record. The amount of multi-year ice (ice that has survived at least one summer melt season), is one of the lowest levels in the ice age record, which began in 1984.

In the Antarctic, sea ice extent is now falling rapidly, but it is still too early to assume that the maximum has been reached. The maximum for Antarctic sea ice typically occurs in late September or early October. However, Antarctic sea ice extent is highly variable near the maximum because of storms acting to expand or compact the extended ice edge.

Please note that this is a preliminary announcement. Changing winds or late-season melt could still reduce the Arctic ice extent, as happened in 2005 and 2010. NSIDC scientists will release a full analysis of the Arctic melt season, and discuss the Antarctic winter sea ice growth, in early October.

Overview of conditions

On September 16, sea ice reached its annual minimum extent of 4.72 million square kilometers (1.82 million square miles) (Figure 1). In response to the setting sun and falling temperatures, ice extent has begun rising and will continue to rise through autumn and winter. However, a shift in wind patterns or a period of late season melt could still push the ice extent lower.

The minimum extent was reached two days later than the 1981 to 2010 median minimum date of September 14. The interquartile range of minimum dates is September 11 to September 19.

Figure 2. The graph above shows Arctic sea ice extent on September 16, 2021, along with several other recent years and the record minimum set in 2012. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data.

Conditions in context

This year’s minimum set on September 16 was 1.33 million square kilometers (514,000 square miles) above the record minimum extent in the satellite era, which occurred on September 17, 2012 (Figure 2). It is also 1.50 million square kilometers (579,000 square miles) below the 1981 to 2010 average minimum extent, which is equivalent to twice the size of Texas.

In the 43-year-satellite record, 15 of the lowest minimums have all occurred in the last 15 years.

Multiyear ice extent is one of the lowest on record. First-year-ice coverage increased dramatically since last year, jumping from 1.58 million square kilometers (610,000 square miles) to 2.71 million square kilometers (1.05 million square miles). The increase in total extent from last year’s minimum to this year’s is hence comprised of first-year ice.

The overall, downward trend in the minimum extent from 1979 to 2021 is 13.0 percent per decade relative to the 1981 to 2010 average. The loss of sea ice is about 80,600 square kilometers (31,100 square miles) per year, equivalent to losing the size of the state of South Carolina or the country of Austria annually.

Fifteen lowest minimum Arctic sea ice extents (satellite record, 1979 to present)

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