HR: 0800h
AN: C21C-1118    [Abstracts]
TI: Response of Changes in Active Layer and Permafrost Conditions to Hydrological Cycle in the Russian Arctic
AU: * Zhang, T
EM: tzhang@nsidc.org
AF: University of Colorado at Boulder, NSIDC/CIRES, 449 UCB, Boulder, CO 80309-0449 United States
AU: Frauenfeld, O W
EM: oliverf@nsidc.org
AF: University of Colorado at Boulder, NSIDC/CIRES, 449 UCB, Boulder, CO 80309-0449 United States
AU: Barry, R G
EM: rbarry@nsidc.org
AF: University of Colorado at Boulder, NSIDC/CIRES, 449 UCB, Boulder, CO 80309-0449 United States
AU: Etringer, A
EM: etringer@nsidc.org
AF: University of Colorado at Boulder, NSIDC/CIRES, 449 UCB, Boulder, CO 80309-0449 United States
AU: McCreight, J
EM: mcceigh@nsidc.org
AF: University of Colorado at Boulder, NSIDC/CIRES, 449 UCB, Boulder, CO 80309-0449 United States
AU: Gilichinksy, D
EM: gilichin@online.stack.net
AF: Russian Academy of Sciences, Institute for Physiochemical and Biological Problems in Soil Science, Russian Academy of Sciences, 142290, Pushchino, Moscow Region, RUSSIA, Pushchino, 142290 Russian Federation
AB: Recent studies indicate that runoff over the Siberian arctic drainage basin in the past several decades has increased substantially. The source of water causing the runoff increase is unknown. In this study, we hypothesize that changes in the active layer and permafrost dynamics play a role in the recent changes in the Arctic hydrological regime. We document (i) permafrost and ground ice distribution; (ii) changes in permafrost temperature, active layer thickness, and length of thaw season over the past few decades, and (iii) their impact on the hydrologic cycle over three Siberian river basins: the Ob, the Yenisey, and Lena river basin. Permafrost underlies approximately 4 to 10% of the total area of the Ob basin, the least among the three river basins, 36 to 55% in the Yenisey basin, and 78 to 93% in the Lena basin. Consequently, total volume of the excess ground ice varies from approximately 302 to 854 km3 in the Ob, 1,699 to 2,462 km³ in the Yenisey, and 3,523 to 4,227 km³ in the Lena basin. Based on ground-based measurements, mean annual soil temperature at 40 cm depth has increased about 1.3°C in the Ob, 0.8°C in the Yenisey, and 1.6°C in the Lena river basin for the period from 1930 through 1990. The increase is more pronounced from the mid 1960s to 1990. An increase in the near-surface soil temperature leads to lateral thawing of permafrost and thickening of the active layer. Long-term soil temperature measurements indicate that permafrost has been degradating during the past several decades. Active layer thickness has increased about 30 cm from the mid 1950 to 1990 over the Lena river basin. Thawing index has increased substantially over all three river basins from the 1950s to 1990s, implying that the increase in active layer thickness is a widespread phenomenon over the Russian arctic drainage basin during the past few decades. Changes in active layer thickness of 15 cm are runoff equivalent of about 0.9 to 2.4 mm in the Ob, about 7.8 to 11.3 mm in the Yenisey, and about 15.3 to 19.4 mm in the Lena. Overall, changes in permafrost conditions in the Ob basin have a minimum impact on runoff. Lateral thawing of permafrost and thickening of the active layer may account for the significant increase in runoff over the Yenisey river basin. Melting of the excess ground ice through thickening of the active layer might be the major source of water to the runoff in the Lena river basin.
DE: 0702 Permafrost (0475)
DE: 0704 Seasonally frozen ground
DE: 0706 Active layer
DE: 1823 Frozen ground
DE: 1836 Hydrological cycles and budgets (1218, 1655)
SC: Cryosphere [C]
MN: Fall Meeting 2005