HR: 09:15h
AN: C11A-06    [PDF]
TI: Hydrological Changes in the Arctic in Response to a Changing Climate
AU: * Hinzman, L D
EM: ffldh@uaf.edu
AF: University of Alaska Fairbanks, Water and Environmental Research Center, Fairbanks, AK 99775-5860 United States
AU: Kane, D L
EM: ffdlk@uaf.edu
AF: University of Alaska Fairbanks, Water and Environmental Research Center, Fairbanks, AK 99775-5860 United States
AU: McNamara, J P
EM: JMCNAMAR@boisestate.edu
AF: Boise State University, Department of Geosciences, Boise, ID 83725-1535 United States
AU: Nolan, M A
EM: fnman@uaf.edu
AF: University of Alaska Fairbanks, Water and Environmental Research Center, Fairbanks, AK 99775-5860 United States
AU: Romanovsky, V E
EM: ffver@uaf.edu
AF: University of Alaska Fairbanks, Geophysical Institute, Fairbanks, AK 99775-7320 United States
AU: Yang, D
EM: ffdy@uaf.edu
AF: University of Alaska Fairbanks, Water and Environmental Research Center, Fairbanks, AK 99775-5860 United States
AU: Yoshikawa, K
EM: ffky@uaf.edu
AF: University of Alaska Fairbanks, Water and Environmental Research Center, Fairbanks, AK 99775-5860 United States
AB: The broadest impacts of climate change to the terrestrial arctic regions will result through consequent effects of changing permafrost structure and extent. As the climate differentially warms in summer and winter, the permafrost will become warmer, the active layer (the layer of soil above the permafrost that annually experiences freeze and thaw) will become thicker, the lower boundary of permafrost will become shallower and permafrost extent will decrease in area. These simple structural changes will affect every aspect of the surface water and energy balances. As the active layer thickens, there is greater storage capacity for soil moisture and greater lags and decays are introduced into the hydrologic response times to precipitation. When the frozen ground is very close to the surface, the stream and river discharge peaks are higher and the base flow is lower. As permafrost becomes thinner, there can be more connections between surface and subsurface water. As permafrost extent decreases, there is more infiltration to groundwater. This has significant impacts on large and small scales. The timing of stream runoff will change, reducing the percentage of continental runoff released during the summer and increasing the proportion of winter runoff. This is already becoming evident in Siberian Rivers. As permafrost becomes thinner and is reduced in spatial extent, the proportions of groundwater in stream runoff will increase as the proportion of surface runoff decreases, increasing river alkalinity and electrical conductivity. This could impact mixing of fresh and saline waters, formation of the halocline and seawater chemistry. Other important impacts will occur due to changing basin geomorphology. Currently the drainage networks in arctic watersheds are quite immature as compared to the more well-developed stream networks of temperate regions. These stream channels are essentially frozen in place as the major flood events (predominantly snowmelt) occur when the soils and streambeds are frozen solid. As the active layer becomes thicker, there could be significantly increased sediment loads delivered to the ocean. Presently, most small streams ($\lessim$1,000 km2) in the Arctic are completely frozen from the bed to the surface when spring melt is initiated. However, in lower reaches of the rivers there are places where the channel is deep enough to prevent complete winter freezing. Break-up of the rivers differs dramatically in these places where the ice is not frozen fast to the bottom. Huge ice chunks are lifted by the flowing water, chewing up channels bottoms and sides and introducing massive sediments to the spring runoff.
DE: 1600 GLOBAL CHANGE (New category)
DE: 1655 Water cycles (1836)
DE: 1823 Frozen ground
DE: 1866 Soil moisture
DE: 9315 Arctic region
SC: Cryosphere [C]
MN: 2003 Fall Meeting