Inter-Annual Variability in the Winter Beaufort High and its Impacts on the Arctic Climate

Abstract:

The Beaufort High (BH) is a region of high sea level pressure, characteristic of the winter Arctic atmosphere. The atmospheric circulation and sea ice motion associated with the BH plays an important role in Arctic climate. The sea level pressure of the High itself shows considerable interannual variability with higher pressures associated with anti-cyclonic winds and ice motion, colder temperatures and thicker sea ice in the western Arctic. The anti-cyclonic winds associated with the BH drive the Beaufort Gyre which stores the majority of the Arctic ocean’s fresh water. A down-spinning of the gyre is cause for concern as it would release the accumulated fresh water and further inhibit sea ice formation. The 2017 mean winter sea level pressure was nearly two standard deviations below the mean from 1979 to present and was associated with a reversal in ice motion in the western Arctic. A warmer fall season is expected to result in thinner sea ice, thus allowing for thermal fluxes from ocean to atmosphere which would otherwise be inhibited. It is hypothesized that these increased thermal fluxes caused by an unusually warm fall in 2016 added sufficient energy to allow extratropical cyclones originating in the North Atlantic to intrude into the Western Arctic, leading to a collapse of the BH. Here we investigate other winters that were associated with anomalously low sea-level pressures associated with the BH. Spatial correlations and composites were computed between an index of the winter BH and winter sea ice thickness and 2m temperatures. As expected, negative correlations were observed in the Western Arctic between temperature and BH index. An overall positive, but weak correlation was shown between the BH index and sea ice thickness in the Western Arctic. Results for the preceding fall were not as robust with a strong signal occurring for those winters with extreme values of the BH index. These results confirm earlier work regarding the impact that BH variability plays in the winter Arctic climate.