The 2023 late summer was another remarkable season around the Arctic. This post looks at temperature and precipitation for July through September (JAS) 2023. I covered the 2023 sea ice minimum here and the 2023 June through August mid-summer season here.
Temperatures
With decreasing solar heating and into the time of maximum change in sea ice extent over the Arctic Ocean, temperature departures can be larger than in mid-summer, and we see that in Fig. 1 with departures in excess of +0.5°C over a large part of the Arctic Ocean. Like 2023 mid-summer, the warmth was widespread, but even less area had even slightly below normal temperatures.
In Canada, both the Northwest Territories and the Yukon Territory had the highest JAS average temperature since (at least) 1950. The record warmth extended in parts of Northeast Alaska and and smaller areas in northern Greenland and the northwest Russian Arctic.
More than 20 percent of the Arctic had either the warmest or second warmest JAS since 1950, so it’s no surprise that in Fig. 2 this year sets a new record for highest average temperature, more than 0.2°C higher than JAS 2016, the previous highest.1
Because the Arctic is an ocean surrounded largely surrounded by land, it can be handy to have the time series just for the land area. The temperature time series pattern is similar to the full Arctic, but as we would expect, with somewhat higher year-to-year variability. The 2023 JAS average temperature over land was nearly 0.5°C higher than previous record set in JAS 2016.
Precipitation
Figure 4 plots the JAS total precipitation as a percent of the 1991-2020 average. Much of the western Canadian Arctic and southeastern Greenland were unusually dry. The European Arctic, northeast Canadian Arctic and most of Greenland as well as parts of Alaska and eastern Russian Arctic were significantly wetter than average. However, unlike temperatures, only small areas in the Scandinavian Arctic, northeast Canada and northern Greenland and northwest Alaska were at or near record high precipitation totals. Small areas in Arctic Canada, southeast Greenland and the Russia Arctic were at or near record low JAS total precipitation.
A quick glance at Fig. 4 might suggest a lot of area with well below normal precipitation. However, closer inspection shows that much of the dryness is in areas between 50°N and 60°N (Canada, eastern Europe), so outside the definition of the Arctic used here (60°to 90°N).
Figure 5 plots the Arctic-wide JAS precipitation since 1950. 2023 ranks as the seventh highest total and is line with the trend that is evident this century. Prior to 2005 there was only late summer season (1989) that has more precipitation than this year.
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 that allows rapid ERA5 regional rankings and time series.
Not shown here but probably a topic for a future post are longer temperature time series reconstructions for the Arctic. For example, the Berkeley Earth average July through September temperature for the Arctic since 1900 shows decadal scale varibility but no long-term trend into the 1980s and then the same dramatic increase as seen in ERA5. There is no doubt at all that JAS 2023 was the warmest late summer season for the Arctic in centuries.
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