This post will be updated as additional data become available.
At the global scale, 2024 is “effectively certain” to be the warmest year on record in the ERA5 reanalysis as per the Copernicus Climate Change Service, breaking the previous record from 2023. In Alaska, the mean annual air temperature in 2023 was slightly above the 1991-2020 climate normal but well below the record years 2016 and 2019. Based on preliminary data through the end of November, 2024 looks to follow a similar pattern and mean annual temperatures for the state are likely to be above average but not record-breaking.
Temperature in detail
January brought warmer than average temperatures in western Alaska and some very cold weather in the Interior and Southcentral. February was also warmest in the west with moderate cool anomalies in the Interior. March and April were warmer than average. A cold May in most of the state was followed by a warm June in mainland Alaska, although regional cold anomalies persisted in the Bering and Chukchi Sea. July and August were moderately colder than normal most of the state. Positive temperature anomalies returned in September in most of the state, with slightly cooler conditions in the Southwest. Notably, the cold anomalies in the Chukchi and Bering Sea remained in place from May (arguably even from February) through September. In October, warmer than average conditions spread into the Chukchi and Bering Sea and broke the “cool spell”. Northern Alaska saw pronounced warm anomalies in October and November while the rest of the state experienced regionally variable temperatures. December was unusually warm in much of the state and many regions recorded their highest monthly temperature anomalies of the year in this month. The North Slope was an exception to this pattern. December in northern Alaska was slightly warmer than the 1991-2020 normal but anomalies remained substantially below the values recorded in the southern half of the state.
The figure below shows annual temperature anomalies compared to the 1991-2020 normals at selected First Order stations since 1950. 2024 data are included up to December 31 and give an indication of how this year will compare to the long term time series. Utqiaġvik was once again the warmest station in relative terms and had a similar deviation as last year of 3.34°F above normal. Kotzebue had the third year in a row with a negative deviation, although 2024 was only minimally below the climatological normal (-0.15°F). December was very warm in many regions of Alaska and shifted the statistics a little during the last weeks of the year. Most of the selected locations had a mean annual air temperature relatively close to the 1991-2020 average.
2024 brought some very pronounced temperature swings in different regions of the state. From late January into February, a prolonged cold spell brought very low temperatures and a reminder of just how cold “winter in Alaska” can be to Fairbanks and Anchorage. There were similarly pronounced warm and hot episodes over the course of the year. December felt almost balmy until recently and will likely be a warmer than average month in most regions. We will update this blog post in early January to complete the month of December in the figures.
The daily temperature anomalies shown below for Fairbanks, Anchorage, Utqiaġvik, and Juneau highlight the seasonal and regional variations of climate and weather in Alaska. The graphics are available on our website for additional stations.
Precipitation and Snow
As of mid-December, 2024 looks to have been a rather wet year in most of Alaska. The First Order stations all recorded at least 80% of normal precipitation and most are currently between 100% and 140%. Utqiaġvik and Nome had the highest deviations from normal. Southeast Alaska was relatively dry compared to the long term average. The southern regions of the Panhandle experienced abnormally dry conditions and moderate drought between July and September.
In western Alaska, January, February, April, July, and August stand out as considerably wetter than average based on ERA 5 reanalysis data. June, September, and November were unusually dry over the Chukchi and Bering Sea and much of mainland Alaska.
Long term time series of snow fall and snow depth are available from the First Order Stations in Anchorage, Fairbanks, Juneau, and Bettles. Snow depth at these four locations is visualised through mid-December in the plots below. Anchorage is currently at near average snow depth. A substantial snowfall in late October brought the start of the seasonal snow pack but mild weather and rain have since compacted the snow and lead to a decrease in snow depth since early November. Fairbanks is having an above average season to date, with notable snow fall events in mid-October and December. Juneau had a very snowy episode in late November followed by rain in December. Snow depth was briefly well above average but the snow at the airport weather station has largely melted again. In Bettles, the evolution of the snow pack has followed the long term average closely since the start of the 2024/25 snow season.
Arctic Sea Ice
The Arctic sea ice reached a minimum extent of 4.28 million square kilometers by mid-September 2024. This 2024 minimum sea ice extent corresponded to the seventh lowest area on the record since the start of reliable satellite derived sea ice data in 1978. This minimum 2024 sea ice extent tied with the 2023 minimum extent. Following the mid-September minimum, the sea ice increased but at a below average rate during the late fall/winter 2024 to currently 11 million square kilometers; this extent is tied with the all time minimum Arctic sea ice extent for late December.
Pacific decadal oscillation (PDO) and ENSO
The PDO is a large-scale circulation pattern related to sea surface temperatures in the Pacific north of 20° latitude. Like ENSO (El Niño Southern Oscillation), the PDO index has a “cool”, negative phase and a “warm”, positive phase. A positive PDO tends to coincide with above average temperatures in Alaska. For example, the 1976 phase shift of the PDO index from negative to positive has been linked to an increase in regional temperatures in the mid-1970s (Hartmann and Wendler, 2005).
Since early 2020, the PDO index has been negative. In 2024, the index dropped below -3 in several months, with the lowest value registered in October at -3.78. This is the lowest monthly value in the NOAA NCEI time series, which goes back to 1854. The strongly negative PDO may have dampened temperatures regionally. However, it is not possible to quantify the potential impact of the PDO on Alaska temperatures and the linkage is incompletely understood.
ENSO also affects weather and climate in Alaska and typically oscillates between positive and negative phases at time scales of 2 to around 5 years. PDO cycles are much slower and occur at roughly decadal scales. ENSO as expressed by the Oceanic Niño Index (ONI) transitioned from the “warm” el Niño phase and a strongly positive ONI to ENSO neutral conditions and slightly negative values during the summer months of 2024. ENSO forecasts have been favouring a transition into weak la Niña conditions in recent months and continue to predict decreasing values for the 2024/25 winter. To date, the ONI remains slightly negative in ENSO neutral conditions.
The graphic below shows the monthly PDO index since 1950 up to November 2024 in the upper panel and a 12-month rolling mean of statewide and selected division-wide temperature anomalies. “Division-wide” refers to the NCEI climate divisions for Alaska. The correlation of temperature anomalies and PDO varies seasonally and regionally. The graphic also highlights that temperature anomalies often differ considerably between different regions of Alaska.
References
Hartmann, B. and Wendler, G., 2005. The Significance of the 1976 Pacific Climate Shift in the Climatology of Alaska. Journal of Climate, 18, 4824-4839. https://doi.org/10.1175/JCLI3532.1