HR: 0800h
AN: B41A-0090    [Abstracts]
TI: Importance Of Recent Shifts In Soil Thermal Dynamics On Growing Season Length, Productivity, And Carbon Sequestration In Terrestrial High-Latitude Ecosystems
AU: * Euskirchen, S
EM: ffese@uaf.edu
AF: Institute of Arctic Biology, University of Alaska Fairbanks, 211 Irving I, Fairbanks, AK 99775 United States
AU: McGuire, A D
EM: ffadm@uaf.edu
AF: U.S. Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, University of Alaska Fairbanks, 211 Irving I, Fairbanks, AK 99775 United States
AU: Kicklighter, D W
EM: dkick@mbl.edu
AF: The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543 United States
AU: Zhuang, Q
EM: qzhuang@mbl.edu
AF: The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543 United States
AU: Clein, J S
EM: fnjsc@uaf.edu
AF: Institute of Arctic Biology, University of Alaska Fairbanks, 211 Irving I, Fairbanks, AK 99775 United States
AU: McDonald, K C
EM: kyle.mcdonald@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 300-233 4800 Oak Grove Drive, Pasadena, CA 91101 United States
AU: Smith, N V
EM: nicolev@gps.caltech.edu
AF: Geological and Planetary Sciences, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91101 United States
AU: Kimball, J S
EM: johnk@ntsg.umt.edu
AF: Flathead Lake Biological Station, Division of Biological Sciences, The University of Montana, 311 BioStation Lane, Polson, MT 59860 United States
AU: Dargaville, R J
EM: Roger.Dargaville@cea.fr
AF: Laboratoire des Sciences du Climate et de l'Environment, L'Orme des Merisiers, Batiment 701, Gif-sur-Yvette, 91191 France
AU: Dye, D G
EM: dye@jamstec.go.jp
AF: Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, 3173 Showa-machi, Kanazawa-ku, Yokohama-shi, Kanagawa-ken, Yokohama, 236-0001 Japan
AB: In terrestrial high-latitude regions, observations indicate recent phenological changes in snow cover extent and soil freeze-thaw transitions due to climate change. These modifications may result in temporal shifts in the growing season and the associated rates of terrestrial productivity. Changes in productivity will influence the ability of these ecosystems to sequester atmospheric CO$_{2}$. We use the Terrestrial Ecosystem Model (TEM), which simulates the soil thermal regime, in addition to terrestrial carbon, nitrogen and water dynamics, to explore these issues by examining trends over recent decades in extratropical regions ($30\deg$-$90\deg$ N). The TEM simulations indicate snow cover duration has decreased by approximately 6-8 days between the years 1972-2000. This result is generally consistent with NOAA satellite observations, which show a decrease between 3-6 days per decade since 1972. This modeled decrease in snow cover is associated with a trend towards an earlier thaw date of frozen soils and the onset of the growing season in the spring by approximately 1-2 days between 1960 and 1980 and 3-5 days from 1980-2000. Between 1988 and 2000, satellite records show a slightly stronger trend in thaw and the onset of the growing season, averaging between 5-8 days earlier. Although the 1960s-1980s showed a less pronounced trend in earlier thaw dates and increased growing season length, our model analyses indicate increasing net carbon uptake at the decadal scale. The regions between $60\deg$ - $90\deg$ N have acted as a source of 0.05 Pg C in the 1960s, 0.03 Pg C in the1970s, 0.01 Pg C in the 1980s, and ultimately shifting to a sink of 0.04 Pg C during the 1990s. Taking into account the effects of changes in land-use in the region between $30\deg$ - $60\deg$ N, the TEM results show a gradual enhancement in net carbon uptake from 0.56 Pg C in the 1960s to 1.0 Pg C in the 1990s. Our results reveal noteworthy patterns of phenological change in growing season and productivity over the past four decades, indicating that prediction of terrestrial carbon dynamics from one decade to the next will require that large-scale models adequately take into account the corresponding changes in soil thermal regimes.
DE: 4805 Biogeochemical cycles (1615)
DE: 4203 Analytical modeling
DE: 1600 GLOBAL CHANGE (New category)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting