A168-06
Frequent winter 2020 storms over the Beaufort and Chukchi Seas continue recent trend
Monday, 14 December 2020: 19:20
Virtual
Thomas Ballinger1, John E Walsh2, Uma Suren Bhatt3, Peter Bieniek4, Brian Brettschneider5, Hajo Eicken6, Andrew R Mahoney7, Jacqueline Richter-Menge8, Lewis H Shapiro7 and Mark A Tschudi9, (1)International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK, United States, (2)Univ Alaska, Fairbanks, AK, United States, (3)University of Alaska Fairbanks, Fairbanks, AK, United States, (4)International Arctic Research Center, Fairbanks, AK, United States, (5)Postdoctoral Associate, IARC,UAF, Anchorage, AK, United States, (6)University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, AK, United States, (7)University of Alaska Fairbanks, Geophysical Institute, Fairbanks, AK, United States, (8)US Arctic Research Commission & University of Alaska Fairbanks, Hanover, NH, United States, (9)University of Colorado at Boulder, CCAR, Boulder, CO, United States
Abstract:
During late winter 2020, an interdisciplinary team of University of Alaska Fairbanks scientists, providing sea ice and weather forecasting support of the U.S. Navy’s biennial Ice Exercise (ICEX), noted frequent and, at times, anomalously strong cyclonic weather systems traversing the Chukchi and Beaufort Seas.
The occurrence of these low pressure patterns coincided with slow, anomalous eastward drift of the first- and multi-year sea ice pack.
Motivated by this seemingly unusual frequency of cyclonic systems over the forecast region at the expense of the climatological Beaufort High, and resulting effects on ice motion, we sought to quantify winter (January – March) cyclonic activity in terms of mean, variance, frequency, and duration characteristics across the region from 1948-2020 thereby allowing us to place winter 2020 in a historical context.
Analysis of Beaufort and Chukchi Seas areal mean sea-level pressure (MSLP) using NCEP/NCAR reanalysis data revealed March daily record minima on 19-20 March 2020 as well as a new record minimum (~1009 hPa) for March monthly MSLP. Preceding January and February 2020 monthly MSLP ranked in the lower quintile of the distribution with values at least -4 hPa below the long-term mean. An evaluation of extreme event duration (e.g. MSLP ≤-1 standard deviation for 3 consecutive days) indicated above-average but not record persistence of events in February and March 2020. In contrast, these months saw a record number of non-consecutive, negative MSLP anomaly days (n=25) in February and extreme days (n=5), where MSLP was ≤-2 standard deviations below the daily mean, during March. The active storm track across the Beaufort and Chukchi Seas in winter 2020 may reflect a record-high Arctic Oscillation (AO) value (i.e. January – March mean CPC AO = 2.83 standard deviations above the long-term mean) with cyclonic winds and ice motion across the Arctic basin. This stormy pattern of late winter 2020 continues a 5-6 year trend toward declining MSLP and a rather inactive Beaufort High and Gyre, which may have important implications for the region’s freshwater budget and sea ice processes in the near-term. During ICEX (February/March 2020), key consequences of high storm activity in the study area were idling of the sea ice rather than westward motion and fragmentation of ice floes deep inside the ice pack.
