October 2023 Climate Summary
Continued Warm and Wet
The end of September sea ice extent was low even by recent standards, especially on the Pacific side of the Arctic, and mid-latitude oceans very warm, so it is no great surprise that October 2023 in the Arctic overall turned out warm and wet.
Temperatures
For the Arctic (land and ocean poleward of 60°N) as a whole this was the sixth warmest October on record, with all five warmer Octobers having occurred since 2016. For Arctic land area only the month effectively tied with October 2021 and 2022 for the warmest. Figure 1 shows the October average temperature departure from the 1991-2020 baseline average (°C). The extent of relative warmth, with nearly all of Arctic Canada, northern Alaska and nearly the entire Asian portion of the Russian Arctic was outstanding and magnifies the below normal temperatures over Scandinavia.
Zooming into Alaska and vicinity in Fig. 2, we see northern and most of southern Alaska as well as the Russian far northeast and northwest Canada were all warmer than normal. A belt of near normal temperatures runs from southwest mainland Alaska northeastward into the central Yukon Territory. In much of this area this “near normal” was really a mix of below normal temperatures the first three weeks of October followed by significantly warmer than normal temperatures the week before Halloween. Temperatures in Alaska during the month ranged a high of 67°F (19.4°C) at Metlakatla on the 13ᵗʰ to a low of -13°F (-25.0°) at Robertson River cooperative station, west of Tok, on Halloween.
October Air Temperatures at Utqiaġvik
In a previous post I discussed the large scale importance of the loss of sea ice on October temperatures. Here I want to highlight the change at Utqiaġvik, Alaska. Alaska’s northernmost community has unbroken climate observations by the Weather Bureau/NWS since the fall of 1920.1 Figure 3, the century-long October temperature time series illustrates a stunning example of abrupt climate change. This year the average October temperature was 26.0°F (-3.3°C), the fourth highest in the past 104 years. However, it’s perfectly in keeping with every October since 2002. Utqiaġvik is located on a “fat” peninsula with the Chukchi Sea from southwest to north of town and the Beaufort Sea only a few miles to the northeast. So unless the wind is blowing from the east through due south, it’s an ocean wind. At 71.3°N, solar hearing in October is minimal, so the open ocean water are an important source of heat to the atmosphere. Since 2002 there hasn’t been significant sea ice near Utqiaġvik, and so air temperatures are strongly controlled by the water temperature. That occasionally happened prior to 2002, but there is simply no way to have October temperatures average lower than 15°F (-9°C) without significant ice cover most of the month. The loss of October sea ice has driven the birth of a new climate (for Utqiaġvik), with monthly temperatures now typically at or above what used to be near record high levels and there’s very limited year-to-year variability compared to pre-2002.
Precipitation and Snowfall
Precipitation is almost always much more variable over short distances than temperatures, and Alaska and vicinity illustrate this nicely this month. Arctic-wide precipitation this was the seventh highest average October precipitation on record in ERA5 data (last year was the highest), with both record wet and record dry areas. Figure 4 shows the monthly total precipitation as the percent of the 1991-2020 normal. In a dramatic change from early summer, most of Southcentral and southwest Alaska were much drier than normal (as always, there are local scale differences in details compared to station observations, especially near the coastal mountains). For many places in southwest Alaska this was the driest October in about a decade. North Slope precipitation was the highest October total since 2014 in the ERA5 data. The NOAA Climate Reference Network station at the NOAA Barrow observatory north of Utqiaġvik (different than the NWS ASOS at the Airport) reported 1.68 inches (42.7mm) precipitation for the month, making this the highest October total in the 22 year history of that site.
Snowfall observations are made in Alaska only at NWS cooperative weather stations and a small handful of NWS Forecast Office and FAA locations. Table 1 shows the selected snowfall totals and the National Ice Center’s (NIC) snow and ice cover analysis for October 31, 2023.2
Southcentral had little snow during the month, even at moderate elevations, and not unusually, there was very little low elevation snow in Southeast. The Interior had more significant snowfall. The Fairbanks area had the highest October snow total since 2004, though the total would not have been at all unusual in the late 20th cenutry. More significantly, the winter snowpack was established unusually early. For Fairbanks, the winter snowpack was established on October 6, which ties with several other years for the sixth earliest snowpack establishment in the past 94 years.
The most notable feature of the NIC’s October 31ˢᵗ snow and ice analysis is the large area in western and southwest Alaska without snow cover. In some of these areas north of the Yukon-Kuskokwim delta there was snow cover mid-month, but sustained mild weather weather (and on the western Seward Peninsula, rain) the last week of October melted out the thin low elevation snow cover.
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.
National Snow and Ice Center charts are available at: https://usicecenter.gov/Products/ImsCharts
Station climate data is available through scACIS website but use with caution: there is minimal or no quality control for most Alaska data in near real time: https://scacis.rcc-acis.org/
Like other rural Alaska National Weather Service offices, all snow measurements ended at Utqiaġvik in 2019.
The NIC snow cover analysis is binary: yes or no. There is no estimated of snow depth or snow water equivalent. Similarly with sea ice: in this product, only a binary yes/no is shown, with no concentration or other ice characteristics shown.