Temperature Monitoring Under Different Land Covers on the North Slope of Alaska

Abstract:

Arctic greening describes the thickening of herbaceous layers and northward encroachment of larger woody species into tundra environments. This study aims to evaluate the hypothesis that changes related to Arctic greening can trigger either positive or negative feedbacks for the underlying permafrost system depending on species composition. Some vegetation types can maintain cooler temperatures in summer while increases in shrubs can promote snow accumulation and winter warming. This hypothesis is assessed using long-term data from the Circumpolar Active Layer Monitoring (CALM) network, specifically from a north-south transect of sites within homogenous vegetation types representative of the North Slope of Alaska. At these sites, air and soil-surface temperatures have been monitored over the last 25 years (1995-2019) using miniature temperature data loggers. Temperatures are recorded at the ground surface and at standardized meterological instrument height (2 m) for the air. This work analyzes seasonal temperature offsets between the air and soil-surface to quantify the insulation provided by snow cover and different vegetation types. Documented thermal trends are then examined in conjunction with trends in active layer depth over the 25-year period to analyze the impact on the permafrost system. Results presented in this study provide a better understanding of the implications of Arctic greening and associated data can be used to validate regional to global scale permafrost models.