Autumn 2023 Arctic Climate Review

Warm and Wet

Autumn in the Arctic marks the rapid transition from lingering summer to the winter darkness. On September 1ˢᵗ, there is still continuous daylight (civil twilight) north of 76°N and nowadays sea ice doesn’t reach the minimum annual extent until close to solstice. By November 30ᵗʰ the sun has set for the season north of 69°N and much of the Arctic has its seasonal mantle of snow.

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Temperatures

Autumn 2023 was a another very warm season for the Arctic. Temperature departures were especially high over northern Canada and Alaska and parts of central and western Siberia. For the Arctic a whole (land and sea north of 60°N) this was the third warmest autumn on record, behind only 2020 and (very slightly) 2016. Overall, 89% of the Arctic was warmer than the 1991-2020 baseline normal.

Fig. 1 September-November 2023 average temperature departure from the 1991-2020 baseline average. Data from ERA5 reanalysis.

Canada’s Northwest Territories and Nunavut had the warmest autumn on record. The only land area that was appreciably colder than normal was northern Scandinavia.

Just looking at land areas in the Arctic, autumn 2023 was the warmest on record, edging out 2020. The trend starting around 1990 is dramatic, and is of course fueled by the radical loss of sea ice in this season, which is most pronounced near the Asian and western North American land masses, but the later establishment of the seasonal snowpack is playing a role too.

Fig. 2 Average September through November temperature for land areas poleward of 60°N. Data courtesy ERA5 and processing with code by B. Brettschneider/NWS Alaska Region.

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Precipitation

As always, precipitation has much more spatial variability than temperatures, but overall, autumn 2023 precipitation, like temperature, ranks as the third highest for the Arctic. Unsurprisingly, four of the five wettest autumns have occurred since 2017. A total of 65 percent of the Arctic had above normal precipitation this fall, which is the highest for this season in the ERA5 dataset.

Fig. 3 September-November 2023 percent of normal precipitation relative to 1991-2020 baseline. Data from ERA5 reanalysis.

In parts of the Canadian Arctic Islands (especially Banks Island) and parts of central Nunavut, as well as portions of northern Siberia, this was the wettest autumn of record.

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Sea Ice

I wrote about the September 2023 Arctic sea ice minimum here, which was the sixth lowest in the 45-year satellite record. At the end of November the Arctic-wide sea ice extent was the fifth lowest on record. Per Fig. 4, ice extent was below median extent on both the Atlantic and Pacific sides of the Arctic and in Hudson Bay.

Fig. 4 Sea ice concentration for November 30, 2023. Image courtesy NSIDC.

In Fig. 5 I show the increase in sea ice extent between the sea ice minimum and the end of November. While there are some outliers, the year-to-year increase is fairly consistent. There is a clear increase around 2007, corresponding with the dramatic ice loss that occurred that year. 2023 was a typical year in regards to autumn ice extent increase.

Fig. 5 1979 to 2023 annual increase in sea ice extent between the sea ice minimum and November 30th. Data from NSIDC Sea Ice Index version 3.

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Technical details:

Technical details: Temperature and precipitation analysis spatial maps and time series from ERA5 reanalysis data from ECMWF/Copernicus. Code by B. Brettschneider/NWS Alaska Region allowing rapid ERA5 regional analysis is invaluable for my work.

NSIDC Arctic Sea Ice information, graphics and data available at https://nsidc.org/arcticseaicenews/