HR: 16:15h
AN: B12G-02    [PDF]
TI: The effect of Arctic warming and sea ice loss on the growing season in northern terrestrial ecosystems
AU: * Noone, D
EM: dcn@caltech.edu
AF: California Institute of Technology, Division of Geological and Planetary Sciences, 1200 E. California Blvd., Pasaedna, CA 91125 United States
AU: Randerson, J
EM: jranders@uci.edu
AF: Department of Earth System Science, University of California at Irvine, 3212 Croul Hall, Irvine, CA 92697-310 United States
AU: Yung, Y
EM: yly@gps.caltech.edu
AF: California Institute of Technology, Division of Geological and Planetary Sciences, 1200 E. California Blvd., Pasaedna, CA 91125 United States
AB: High-latitude regions are particularly sensitive to climate change, with warming over three times the global mean expected in the twenty-first century. One aspect of polar climate that can exacerbate Arctic change is the sea ice state. Here the impact of sea ice loss on Arctic warming and growing season length is evaluated using an atmospheric general circulation model. High-latitude change in a simulation representative of 2080 conditions with enhanced greenhouse forcing was contrasted with change deduced from a simulation in which only the sea ice state was degraded. In winter, sea ice loss advances the timing of minimum temperature and promotes heating of the atmosphere by the ocean. Because of this, high-latitude terrestrial systems experience earlier thaw, however, only with enhanced greenhouse forcing did the summer maximum temperature increase and did the onset of freezing become substantially delayed. The sea ice alone accounted for an increase in the growing season length of typically 5-7 days because of earlier onset; lengthening of the growing season by 9-12 days was realized with enhanced greenhouse forcing because of the delayed freeze. Gross primary production also increased because of greater water availability in summer, associated higher precipitation rates throughout the year. As such, while changes in the atmospheric circulation conditions at non-polar latitudes in response to greenhouse forcing are important also in the Arctic, the role that sea ice plays in amplifying high-latitude change is of equal concern. It was also found that warmer Arctic conditions decreased variations in near surface temperature associated with both storminess and the diurnal cycle. The probability of freezing point in the 36 days near the onset of growing halved when change due to sea ice was considered in concert with other changes with greenhouse forcing, while there was a slightly greater probability of frost when changes due to sea ice were considered alone. These results suggest that the susceptibility of high-latitude net ecosystem production will depend on changes in the probability of extreme weather as well as the mean state.
DE: 0315 Biosphere/atmosphere interactions
DE: 1615 Biogeochemical processes (4805)
DE: 3309 Climatology (1620)
DE: 3349 Polar meteorology
DE: 9315 Arctic region
SC: Biogeosciences [B]
MN: 2003 Fall Meeting