Micrometeorology and Heat Budget over the Arctic Tundra at Barrow, Alaska in the Summer of 1993

Abstract

The tundra ecosystem contains a large amount of organic matter in the seasonally thawed layer and permafrost which might be a source of greenhouse effect gases due to global warming. This study was carried out to determine whether or not the tundra ecosystem has become a source of greenhouse effect gases. The micrometeorology of the Arctic coastal tundra ecosystem near Barrow, Alaska was measured during the summer of 1993, in order to make clear the characteristics of the heat budget in relation to the global warming phenomena. Over this Arctic coastal tundra, the heat budget components changed remarkably due to air mass conditions. Cold and moist wind from the Polar Sea brought high levels of sensible heat flux H and the air temperature did not increase. Warmer and drier wind on clear days from inland tundra increased air and soil temperatures and reduced the relative humidity and H. The cold and moist wind was observed frequently in June and early July, and the warmer and drier wind was after late July. The ratio of sensible heat flux to net radiation H/Rn, increased with wind speed but that of latent heat flux lE to net radiation lE/Rn did not, when the tundra surface was dry. Analyses of lE/Rn and H/Rn showed that each active surface level of heat flux was different between lE and H under dry conditions. After heavy rain the surface of the tundra ecosystem turned into standing water conditions. That made the active surface levels the same for lE and H, which increased of lE/Rn with wind speed. The Arctic coastal tundra ecosyatem is characterized by a thick moss carpet whose diffusion resistance (canopy resistance rc) was examined. The canopy resistance for latent heat flux was larger under drier tundra conditions than under standing water conditions. Drying of the tundra ecosystem makes the contribution of sensible heat flux H/Rn larger which might affect greenhouse effect gas fluxes of CO2 and CH4, and will accelerate global warming. © 1996, The Society of Agricultural Meteorology of Japan. All rights reserved.