HR: 13:55h
AN: H33K-02 INVITED    [Abstracts]
TI: Is the Arctic's Freshwater Cycle Changing?
AU: * Serreze, M C
EM: serreze@kryos.colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences, Campus Box 449, University of Colorado, Boulder, CO 80309-0449, United States
AB: Water evaporated in low and middle latitudes is transported poleward via the atmospheric circulation. Some condenses and falls to the surface at precipitation. Further evaporation returns some of this water back to the atmosphere, which may fall again as precipitation. However, as annual evaporation rates in high latitudes are in general modest, the end result is that most of the north polar region is characterized by positive net precipitation (precipitation minus evaporation, or P-E) in the annual mean. Ultimately, this freshwater excess must be returned to lower latitudes. In its broadest sense, the observed major features of the Arctic's mean annual freshwater budget reflect this large-scale balance requirement. Climate models tell us that as the climate warms in response in response to greenhouse gas loading, the hydrologic cycle should intensify, seen as a general increase in high latitude P-E and increased freshwater export to lower latitudes. Attendant changes in stocks should include more atmospheric water vapor and a fresher Arctic Ocean, with a shrinking proportion of this storage represented by sea ice. Observational evidence for these changes is incomplete and often conflicting, For example, while discharge from Siberian rivers to the Arctic Ocean has increased, this cannot be cleanly linked to changes in terrestrial precipitation, evaporation, or P-E. Oceanic freshwater transports are very difficult to assess. Although it seems clear that freshwater storage in the form of sea ice is declining, quantitative information is lacking. Change detection will always be hampered by deficiencies in available data sets and strong natural variability which characterizes the Arctic system. Finally, we must always remember that our best models are but simplifications of a climate system that often surprises us.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1818 Evapotranspiration
DE: 1833 Hydroclimatology
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1863 Snow and ice (0736, 0738, 0776, 1827)
SC: Hydrology [H]
MN: 2007 Fall Meeting