Surface moisture budget of tundra and boreal ecosystems in Alaska: Variations and drivers

• Published in: Polar Science
• Main Authors: Thunberg, Sarah M., Walsh, John E., Euskirchen, Eugénie S., Redilla, Kyle, Rocha, Adrian V.
• Language: English
• Published: 2021
• Subjects: Evapotranspiration; Arctic; Moisture budget; Tundra; Boreal forest; permafrost; Polar Science; Alaska
• Online Access: https://nipr.repo.nii.ac.jp/records/16818

The trajectory of land surface wetness is one of the most consequential unknowns in the Arctic climate system. The present analysis is intended to (1) document seasonal and interannual variations of surface moisture fluxes, (2) clarify the drivers of P-ET variations among Arctic vegetative types, and (3) evaluate the effects of wildfire disturbance on ET. The analysis is based on field measurements from sites in boreal forest and tundra ecosystems of Alaska. The surface moisture budget at boreal forest sites in permafrost areas generally shows a moisture deficit in late spring and early summer, followed by a moisture surplus from late summer into autumn. The annual net P-ET is generally positive but can vary interannually by more than an order of magnitude. The primary drivers of variations in evapotranspiration over weekly to monthly timescales are radiative fluxes, air temperature, relative humidity and wind speed. Overall, the ET at forest sites shows a stronger dependence on relative humidity and wind speed, while ET at tundra sites shows the stronger dependence on air temperature. These differences imply that tundra sites are more temperature-limited and forest sites are more humidity-dependent. Relative to a nearby unburned site, a burned forest site in interior Alaska shows an increase in ET for nearly a decade following the fire, while the recovery time for ET at a burned tundra site is only about three years. journal article