Unusual West Arctic Storm Activity During Winter 2020: Another Collapse of the Beaufort High?

Weather and sea ice forecasts provided in support of the U.S. Navy's Ice Exercise winter 2020 campaign in the Beaufort Sea noted frequent storms in the absence of the climatological Beaufort High which coincided with anomalous eastward drift of the region's ice cover. To place the 2020 Beaufort‐Chukchi regional atmospheric conditions in historical context, we evaluated winter low sea‐level pressure (SLP) extremes and storm characteristics in the region over the 1948–2020 period. March 2020 SLP in the Beaufort‐Chukchi region was the lowest of the modern reanalysis era (1009.07 hPa) with record counts of passing storms and days with SLP at least two standard deviations below the climatological mean. The Beaufort High collapse in winter 2020 continued a recent pattern of Beaufort High collapses dating back to 2010. Unlike other recent collapses, such as 2017, most of the late‐winter 2020 cyclones originated locally over the western Arctic Ocean. Plain Language Summary: Unusually stormy winter weather occurred in the southern Beaufort Sea during February and March 2020, affecting the U.S. Navy's Ice Exercise (ICEX) operations. Instead of the typical Beaufort High pressure pattern and associated easterly winds, frequent and at times intense storms moved across the Chukchi and Beaufort Seas, ushering westerly winds and eastward drift of sea ice and the ICEX camp. To quantify how unusual these weather conditions were, we evaluated storm activity from 1948 to 2020. March 2020 set a low pressure record for the month, in part because a record‐number of intense storms that moved across the area. This storminess was supported by an unusually strong atmospheric circulation pattern over the Arctic Ocean that aided repetitive storm passage. Since 2010, the late‐winter Beaufort High has been less common amidst more frequent storm activity, and three of the lowest four March mean sea‐level pressure values on record have occurred during the last 4 years. This change in weather conditions has broad implications for the Arctic environment. Key Points: March sea‐level pressure (SLP) in 2020 was the lowest since 1948 over the Beaufort and Chukchi SeasFrequent and intense storms contributed to anomalous eastward sea ice motion in the regionMarch 2020 continued a recent trend of Beaufort High collapse events as three of the four lowest March SLPs have occurred since 2017 [ABSTRACT FROM AUTHOR]