Evapotranspiration from a Wetland Complex on the Arctic Coastal Plain of Alaska

Evapotranspiration (ET) from an arctic coastal wetland near Prudhoe Bay, Alaska, was studied during the summers between 1994 and 1996. The purpose of the study was to compare different ET models and to gain a better understanding of evapotranspiration from arctic wetlands. The models used to obtain ET from the watershed were the Bowen ratio energy balance (BREB), Priestley-Taylor (PT), Penman-Monteith (PM), Penman Combination (PC), energy balance (EB), water balance (WB), and WB based on Time Domain Reflectometry (TDR). For one of the ponds, evaporation determined by the EB, PT, PC, BREB, WB, and the aerodynamic (AD) methods were also compared. ET during the summer snow-free period for the watershed averaged 1.45 mm/day obtained via the BREB model. Evaporation from all ponds after spring snowmelt averaged 3.11 mm/day (obtained via the WB). Evaporation rate from ponds was on average twice that of the tundra as a whole. Latent heat flux was the dominant energy sink in wetlands and ponds, whereas sensible heat flux dominated in the drier upland area. The PT and PM models compared well to the BREB (used as the standard of comparison for ET) for 1994 and 1995, once parameters were properly calibrated using 1996 data. The BREB compared well with independent values of ET from the water balance and eddy correlation methods. For the pond, the EB, BREB, WB, PT, and AD methods gave very similar evaporation results for the summer.