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Abstracts
SEARCH Open Science Meeting
October 27, 2003
Seattle, Washington, USA
Permafrost Thawing and Hydrologic Response Over the Russian Arctic Drainage Basin
Tingjun Zhang1, Roger G. Barry2, Mark Serreze3, Daqing Yang4, Andrew J. Etringer5, David Gilichinsky6, Oliver Frauenfeld7, Hengchun Ye8, Christoph Oelke9, Feng Ling10, Sveta Chudinova11
1National Snow and Ice Data Center, University of Colorado at Boulder, 449 UCB, Boulder, CO, 80309-0449, USA, Phone 303-492-5236, Fax 303-492-2468, tzhang@nsidc.org
2NSIDC/CIRES, University of Colorado at Boulder, 449 UCB, Boulder, CO, 80309-0449, USA, Fax 303-492-2468, rbarry@nsidc.org
3NSIDC/CIRES, University of Colorado, 449 UCB, Boulder, CO, 80309-0449, USA, serreze@kryos.colorado.edu
4Water and Environmental Research Center, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA, ffdy@uaf.edu
5NSIDC/CIRES, University of Colorado, 449 UCB, Boulder, CO, 80309-0449, USA
6Institute for Physicochemical and Biological Problems in Soil Science, Pushchino, Russia
7NSIDC/CIRES, University of Colorado, 449 UCB, Boulder, CO, 80309-0449, USA, oliverf@kryos.colorado.edu
8Department of Geography and Urban Analysis, California State University, Los Angeles, Los Angeles, CA, 90032-8222, USA, hengchun.ye@calstatela.edu
9NSIDC/CIRES, University of Colorado, 449 UCB, Boulder, CO, 80309-0449, USA, coelke@kryos.colorado.edu
10NSIDC/CIRES, University of Colorado, 449 UCB, Boulder, CO, 80309-0449, USA, ling@kryos.colorado.edu
11Russia
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 key 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 cubic kilometer in the Ob, 1,699 to 2,462 cubic kilometer in the Yenisey, and 3,523 to 4,227 cubic kilometer in the Lena basin. Based on ground-based measurements, mean annual soil temperature at 40 cm depth has increased about 1.3 degree Celsius in the Ob, 0.8 degree Celsius in the Yenisey, and 1.6 degree Celsius 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 15 cm from the mid 1960 to the mid 1980 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. The onset of the thawing season started earlier in spring and the last date of thaw season became later in the autumn. As a result, the length of thaw season increased by 15 to 25 days. An increase in the length of thaw season and thickening of the active layer delay the freeze-up date of the active layer. Late freeze-up of the active layer partly explains the increased runoff during winter months.
Abstract Categories: Changes on Land
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