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Title: Past and projected future changes in snowpack and soil frost at the Hubbard Brook Experimental Forest, New Hampshire, USA

Author
item CAMPBELL, J - Forest Service (FS)
item OLLINGER, S - University Of New Hampshire
item Flerchinger, Gerald
item WICKLEIN, H - University Of New Hampshire
item HAYHOE, K - Texas Tech University
item BAILEY, A - Forest Service (FS)

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2010
Publication Date: 4/20/2010
Citation: Campbell, J.L., S.V. Ollinger, G.N. Flerchinger, H. Wicklein, K. Hayhoe, and A.S. Bailey. 2010. Past and projected changes in soil frost at the Hubbard Brook Experimental Forest, New Hampshire, USA. Hydrological Processes 24(17):2465-2480. DOI: 10.1002/hyp.7666

Interpretive Summary: Long-term data from the Hubbard Brook Experimental Forest in New Hampshire indicate a warming climate, with increased air temperature by about 1 °C over the last half century and significant declines in snow depth, and snow cover duration. It has been suggested that warmer air temperatures may result in colder soils and more soil frost, as warming leads to a reduction in snow cover insulating soils during winter. However, results from simulated soil freezing and thawing to the year 2100 using a soil energy and water balance model driven by climate change projections from three Atmosphere-Ocean General Circulation Models indicated no major changes in maximum annual frost depth. The most important change suggested by the model is a decline in the number of days with soil frost, stemming from a concurrent decline in the number of snow covered days. This shortening of the frost-covered period has important implications for forest ecosystem processes such as tree phenology and growth, hydrological flowpaths during winter, and biogeochemical processes in soil.

Technical Abstract: Long-term data from the Hubbard Brook Experimental Forest in New Hampshire show that air temperature has increased by about 1 °C over the last half century. The warmer climate has caused significant declines in snow depth, snow water equivalent, and snow cover duration. Paradoxically, it has been suggested that warmer air temperatures may result in colder soils and more soil frost, as warming leads to a reduction in snow cover insulating soils during winter. Hubbard Brook has one of the longest records of direct field measurements of soil frost in the U.S. Historical records show no long-term trends in maximum annual frost depth, which is possibly confounded by high interannual variability and infrequency of major soil frost events. As a complement to field measurements, soil frost can be modeled reliably using knowledge of the physics of energy and water transfer. We simulated soil freezing and thawing to the year 2100 using a soil energy and water balance model driven by statistically downscaled climate change projections from three Atmosphere-Ocean General Circulation Models under two CO2 emission scenarios. Results indicated no major changes in maximum annual frost depth and only a slight increase in number of freeze-thaw events. The most important change suggested by the model is a decline in the number of days with soil frost, stemming from a concurrent decline in the number of snow covered days. This shortening of the frost-covered period has important implications for forest ecosystem processes such as tree phenology and growth, hydrological flowpaths during winter, and biogeochemical processes in soil.