CoAuthors

Sinead Louise Farrell (University of Maryland, USA); John M Kuhn (NOAA Laboratory for Satellite Altimetry, USA); Kyle Duncan (University of Maryland, USA)

The winter conditions of the surface ocean at high latitudes are characterized by stormy seas that pose challenges to coastal communities, fisheries and shipping. Here we investigate conditions in the Bering Sea in winter over the past 20 years using altimeter-derived significant wave height (SWH). Using observations from the Jason-1, -2 and -3 satellites as well as from ERS-2, Envisat, CryoSat-2,SARAL/AltiKa, Sentinel-3A and -3B, we have found that the prevalence of very-high and phenomenal sea state conditions in the Bering Sea have increased. These are sea state conditions with SWH > 9 m, generated by storm-force to hurricane-force winds.

Have winter conditions in the Bering Sea become stormier due to a retreating sea ice cover? We hypothesize that the clear decrease in sea ice extent increases the chance of extreme SWH by increasing ocean fetch and decreasing the dampening effects of sea ice on wave energy. To test this hypothesis, we analyze the spatial and temporal relationships between SWH, sea level pressure systems and surface winds. Atmospheric data are from ERA5 reanalysis. The temporal variability of the atmospheric forcing is investigated by tracking low pressure systems over the Bering Sea and comparing their frequency to the increasing frequency of observed SWH. The role of sea ice variability during the study period is also studied by comparing the spatial trends of sea ice extent to the location of extreme SWH events. This analysis is based on the NOAA/NSIDC Climate Data Record sea ice products. Under similar atmospheric conditions we expect the prevalence of stormy seas to increase for lower sea ice concentrations.