Energy balance of the Arctic

Abstract

The available aerological material now permits a more accurate estimate than before of the various terms in the heat budget. It is difficult to find an area for which all energy budget terms have been evaluated. The research at McGill University has attempted to fill this need for the Polar Ocean. In such discussions the heat fluxes at two levels must be known: in the present investigation, 300 mb and earth's surface were chosen. The heat budget calculations were carried out for several areas of the Polar Ocean. Independent calculations of all terms having been made, it was possible to check the accuracy. Both for the Polar Ocean and the Norwegian-Barents Sea a satisfactory balance was obtained. The surface energy budget shows that the radiative terms are far greater than all other influences, and the long-wave components are the greatest in all areas and months. The sensible heat flux from atmosphere to ground is negligible. In winter, all energy expenditure is radiative from the Polar Ocean, but 20% is non-radiative over the Norwegian-Barents Sea. There, the readily available energy from the ocean compensates for the progressively smaller input by radiation through the winter, and the energy budget remains extraordinarily stable during the winter. Looking at the tropospheric energy budget over the Arctic, there is a sharp increase in importance of non-radiative terms on the income side, and an even more pronounced decrease on the expenditure side. Calculations for the earth-atmosphere energy budget show that the result of no advection into the North Polar regions would be a temperature drop of 35° C over the Norwegian-Barents Sea and about 50° over the Central Polar Ocean. The various energy currents are represented pictorially, setting the total incoming energy at the top of the atmosphere equal to 100 units. All discussions refer to the average conditions over the Arctic Ocean. It would be most valuable to know which changes in the individual terms are possible and can be realised under the existing conditions of the world in which we live. The data available from the present investigation will be used for such a study of climatic change.