B31D-0585
The Role of Snow Cover in Affecting Pan-Arctic Soil Freeze/Thaw and Carbon Dynamics
Wednesday, 16 December 2015
Poster Hall (Moscone South)
Yonghong Yi1, John S Kimball1, Michael A Rawlins2, Mahta Moghaddam3 and Eugenie Susanne Euskirchen4, (1)University of Montana, Numerical Terradynamic Simulation Group, College of Forestry & Conservation, Missoula, MT, United States, (2)University of Massachusetts Amherst, Amherst, MA, United States, (3)University of Southern California, The Ming Hsieh Dept. of Electr. Eng., Los Angeles, CA, United States, (4)University of Alaska Fairbanks, Fairbanks, AK, United States
Abstract:
Satellite data records spanning the past 3 decades indicate widespread reductions (~0.8-1.3 days decade-1) in mean annual snow cover and frozen season duration across the pan-Arctic domain, coincident with regional climate warming. How the northern soil carbon pool responds to these changes will have a large impact on projected regional and global climate trends. The objective of this study was to assess how northern soil thermal and carbon dynamics respond to changes in surface snow cover and freeze/thaw (F/T) cycles indicated from satellite observations. We developed a coupled permafrost, hydrology and carbon model framework to investigate the sensitivity of soil organic carbon stocks and soil decomposition to recent climate variations across the pan-Arctic region from 1982 to 2010. The model simulations were also evaluated against satellite observation records on snow cover and F/T processes. Our results indicate that surface warming promotes wide-spread soil thawing and active layer deepening due to strong control of surface air temperature on upper (<0.5 m) soil temperatures during the warm season. Earlier spring snowmelt and shorter seasonal snow cover duration with regional warming will mostly likely enhance soil warming in warmer climate zones (mean annual Tair>-5°C) and promote permafrost degradation in these areas. Our results also show that seasonal snow cover has a large impact on soil temperatures, whereby increases in snow cover promote deeper (≥0.5 m) soil layer warming and soil respiration, while inhibiting soil decomposition from surface (≤0.2 m) soil layers, especially in colder climate zones (mean annual Tair≤-10 °C). This non-linear relationship between snow cover and soil decomposition is particularly important in permafrost areas, where a large amount of soil carbon is stored in deep perennial frozen soils that are potentially vulnerable to thawing, with resulting mobilization and accelerated carbon losses from near-term climate change.
