Study On Chukchi Sea Alaska Coastal Polynyas And Corresponding Ocean Processes

Using daily AMSR-E sea ice concentration data from2003to2011, thearea of Alaska Coastal Polynyas in the Chukchi Sea was studied.According to the characteristics of these polynyas, threshold method wasproposed to identify each polynya. Frequency of polynyas occurrence wasalso used to delimit the maximum range of polynyas in the studied region.Based on the information extracted from Alaska Coastal Polynyas, thetemporal and spatial variations and their major influence factors werestudied. To eliminate the effect of the open sea on the identificationof polynyas, the analysis was limited between January and April whenBering Strait was totally covered by sea ice.Every winter, five polynyas will appear along the Alaska Coastal areaand are almost parallel to the coastline. In addition to the typicalcoastal polynyas, flaw polynyas tend to appear off landfast ice in thenorthern Alaska Coastal area in late March and April. Daily changes inpolynya areas were dominated on synoptic scale, which is further relatedto the wind directions. Seaward winds favored the formation of coastalpolynyas, but since northeast and north winds prevail in the studiedregion, polynya sites are sometimes closed or diminished in extent forup to a few weeks. Under the effect of northerly winds, Pacific Inflowhas virtually no effect on the northern polynyas but has an importantinfluence on the spatial distribution of southern polynyas along Alaskacoastal area. Utilizing NCEP reanalysis data, heat flux and brine rejection ofpolynyas are studied. Sensible heat flux dominates heat balance ofAlaska Coastal Polynyas in winters. Heat loss which occurs on thesurface of polynyas depends not only on polynya areas, but also the timeof polynya appearance and seasonal changes.Daily salt production of polynyas show varied characteristics onsynoptic scale. From2003to2011, cumulative salt production in eachwinter is around2.8x1012kg; except2004where cumulative salt productionreaches6.8x1012kg, twice the amount of other years. Salt production isclosely related to polynya areas.Combined with field observation data, Polynya has a major impact onthe structure of Canadian Basin Halocline, which is manifested in thelag correlation between polynya salt production and the average salinityof winter Pacific water in the Canadian Basin, while the former lags thelatter one year. Using a polynya box model, halocline water productionis calculated. The annual mean halocline water production in each winterfrom2003-2011is0.15±0.1Sv, while the maintenance of Canadian BasinHalocline requires0.2±0.1Sv of dense water. Alaska Coastal Polynyashave a contribution of more than75%to the formation and maintenance ofCanadian Basin Halocline.