HR: 0830h
AN: C11B-0817    [PDF]
TI: Significant glacial advance during Younger Dryas, Annapurna region, Nepal
AU: * Pratt-Sitaula, B A
EM: pratt@crustal.ucsb.edu
AF: University of California Santa Barbara, Department of Geological Sciences Webb Hall, Santa Barbara, CA 93106 United States
AU: Burbank, D W
EM: burbank@crustal.ucsb.edu
AF: University of California Santa Barbara, Department of Geological Sciences Webb Hall, Santa Barbara, CA 93106 United States
AU: Heimsath, A
EM: arjun.heimsath@dartmouth.edu
AF: Dartmouth College, Department of Earth Sciences, Hanover, NH 03755 United States
AU: Putkonen, J
EM: putkonen@ess.washington.edu
AF: University of Washington, 63 Johnson Hall Box 351310, Seattle, WA 98195 United States
AB: $^{10}$Be exposure ages of moraine boulders and glacially-carved bedrock walls in the Annapurna region of central Nepal show that small glaciers ($<$8 km$_{2}$) were at their maximum extent during the Younger Dryas cold period. Preliminary dates from several large glaciers also show advances during the Younger Dryas. Analyses of past and present small glacier ELAs (equilibrium line altitudes) and modern weather records also indicate that these glaciers require colder temperatures (on the order of 6$\deg$C cooler) to advance to their maximal positions with ELAs 400-1200 m below modern levels. Some valleys that once contained glaciers are now entirely below the summer snows and require cooling to fill with ice. The observation that Younger Dryas glacial advances may be as big or bigger than LGM (late glacial maximum) advances is unusual. However the Younger Dryas may have provided the necessary balance between cold temperatures and moderate precipitation. Other recent research on the timing of Himalayan glaciations have suggested that increased precipitation is the primary factor in glacial advance. The results of this study indicate that significant glacial advances cannot occur in this region if climate is either too arid (i.e. the LGM) or if precipitation is accompanied by too much warming (i.e. early Holocene).
DE: 1620 Climate dynamics (3309)
DE: 1824 Geomorphology (1625)
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
DE: 9320 Asia
SC: Cryosphere [C]
MN: 2003 Fall Meeting