HR: 0800h
AN: C51A-1019    [Abstracts]
TI: Recent Climate Change as Documented by Ice Core Evidence, Glacier Retreat, and Borehole Temperatures for the Gregoriev Ice Cap, Central Asia
AU: * Mikhalenko, V N
EM: vladimir@mikhalenko.ru
AF: Institute of Geography, Russian Academy of Sciences, 29 Staromonetny per., Moscow, 119017 Russian Federation
AU: Thompson, L G
EM: thompson.3@osu.edu
AF: Byrd Polar Research Center, The Ohio State University 1090 Carmack Road, Columbus, OH 43210 United States
AU: Kutuzov, S S
EM: stasan-kora@mtu-net.ru
AF: Institute of Geography, Russian Academy of Sciences, 29 Staromonetny per., Moscow, 119017 Russian Federation
AU: Arkhipov, S M
EM: arhipov@1system.ru
AF: Institute of Geography, Russian Academy of Sciences, 29 Staromonetny per., Moscow, 119017 Russian Federation
AU: Nagornov, O V
EM: nagornov@dpt39.mephi.ru
AF: Moscow Engineering Physics Institute, Mashirskoe Shosse 31, Moscow, 115409 Russian Federation
AU: Lin, P
EM: lin.25@osu.edu
AF: Byrd Polar Research Center, The Ohio State University 1090 Carmack Road, Columbus, OH 43210 United States
AB: From 1990 to 2003 five shallow ice cores were recovered from the summit of the Gregoriev Ice Cap ($41.98\deg$N; $77.916\deg$E; 4609 m asl) in the Tien Shan, Central Asia. The 1990 ice core was analyzed for stable isotopes, microparticle concentrations, major ions and total Beta-activity. The 2001 and 2003 cores were analyzed for stable isotopes and concentrations of radionuclides. The cores were dated using major both reference horizons and annual microparticle concentrations. The detailed stratigraphic records for the top sections of the 1990 and 2001 cores indicate a mean annual net accumulation of 0.35 m ice equivalent (i.e.) for that period compared with the net accumulation from 1963 to 1990 of 0.42 m i.e. At the 4450 m site a decrease of the firn pack depth from 9 to 6 meters has been observed between 1962 and 2003 and over the same period the concentration of infiltration ice increased as a result of greater melt water percolation. Stable isotopic enrichment is evident in the top sections of both the 1990 and 2003 cores. The local meteoric water line is compared with the global one and the relationship between $\delta$$^{18}$O in the cores and mean summer air temperature is compared with that from other glacier areas. Borehole temperatures measured on the top of the Gregoriev Ice Cap (4609 m) in 1990, 2001 and 2003 reveal a $\sim$$1\deg$C warming at 10 m depth over that period. Likewise from 1962 to 2003 boreholes drilled at 4450 m indicate temperature increases of $\sim$$2.5\deg$C at 10m and $0.5\deg$C at 30 m depth. A comparison of airborne images from 1943, 1956 and 1988 along with a satellite image from 2001 shows considerable retreat of the glacier terminus. The rate of retreat is compared to that determined from LIA moraine positions. These glaciological observations, suggesting that a regional warming is underway, are consistent with meteorological observations from the Tien Shan Meteorological Station.
DE: 9320 Asia
DE: 3344 Paleoclimatology
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
DE: 1600 GLOBAL CHANGE (New category)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting