A surface heat flux climatology over a region of the eastern Bering Sea

Abstract

The eastern Bering Sea shelf is a vast area with weak net circulation. As a result, heat exchange with the atmosphere mainly accounts for changes in heat content of the water column. This region also has marked changes in atmospheric and water properties: for example, winds are light in summer but are relatively strong in winter; air temperatures are 10°C or more in summer but are below freezing in winter; and sea surface temperatures vary from ∼10°C to 1°C. A 29 year time series of cloud cover, relative humidity, wind speed, and air temperature was derived from observations made at St. Paul Island (Pribilof Islands) in the eastern Bering Sea. A time series of sea surface temperature near St. Paul Island was also obtained. Cloud cover during 1965–1994 did not undergo significant changes; relative humidity decreased by a barely significant 3%. Mean wind speed during 1965–1979 was 7.2 m s –1 compared with 6.5 m s –1 during 1980–1994. Air temperature during 1965–1976 was 1.3°C cooler than during 1977–1994. The mean annual sea surface temperature maximum increased from 8.7°C during 1965–1976 to 9.3°C during 1977–1994. The seasonal cycles of cloud cover, relative humidity, wind speed, air temperature, and sea surface temperature were then derived from these data and used to calculate the mean monthly and the mean annual surface heat fluxes. Insolation was the dominant flux, followed by latent heat, sensible heat, and net longwave radiation. All of these fluxes have marked seasonal variation. There is a net annual imbalance of 20 W m –2, which is not statistically significant. It could, however, be compensated by weak heat advection from the northward moving currents in the area.