HR: 09:45h
AN: C41A-08    [Abstracts]
TI: Intermittent Thinning of Jakobshavns Isbr‘ Since the Little Ice Age, Reconstructed From Photogrammetry, Remote Sensing and Glacial Geologic Evidence
AU: * Csatho, B
EM: csatho.1@osu.edu
AF: Byrd Polar Research Center, The Ohio State University, 1090 Carmack Rd., Columbus, OH 43210 United States
AU: van der Veen, C
EM: vanderveen.1@osu.edu
AF: Department of Geological Sciences, The Ohio State University, 125 South Oval Mall, Columbus, OH 43210 United States
AU: Schenk, T
EM: schenk.2@osu.edu
AF: CEEGS Department, The Ohio State University, 2070 Neil Av., Columbus, OH 43210 United States
AU: Thomas, R
EM: robert_thomas@hotmail.com
AF: EG&G Services, NASA Wallops Flight Facility, Building N-159, Wallops Island, VA 23337 United States
AB: Rapid thinning and velocity increase on major Greenland outlet glaciers (Jakobshavn Isbr‘, west Greenland; Kangerlussuaq and Helheim glaciers in southeast Greenland) during the last two decades may indicate that these glaciers became unstable as a consequence of the Jakobshavn effect, with terminus retreat leading to increased discharge from the interior and consequent further thinning and retreat. Potentially, such behavior could have serious implications for global sea level. However, the current thinning may simply be a manifestation of longer-term behavior of the ice sheet as it responds to the general warming following the Little Ice Age (LIA). Although Greenland outlet glaciers have been comprehensively monitored since the 1980s, studies of long-term changes mostly rely on records of the calving front position. Such records can be misleading because the glacier terminus, particularly if it is afloat, can either advance or retreat as ice further upstream thins and accelerates. To address this issue, we compiled a history of surface elevation changes of Jakobshavn Isbrae since the LIA. We first combined data from historical records, ground surveys, airborne laser altimetry, and field mapping of lateral moraines and trimlines. This record shows two periods of rapid thinning by about 70 meters, in the early 1950s and since 1997. Observed changes in glacier behavior during these two events are markedly different. The recent thinning, which involved several episodes of retreat followed by large thinning, resulted in a rapid retreat of the calving front toward grounding line. Thinning in the 1950s occurred during a period when the calving front was stationary with only minor annual fluctuations. Nevertheless, aerial photographs collected in the 1940s and 50s indicate that thinning extended far inland.
DE: 0720 Glaciers
DE: 0762 Mass balance (1218, 1223)
DE: 0774 Dynamics
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 4540 Ice mechanics and air/sea/ice exchange processes (0700, 0750, 0752, 0754)
SC: Cryosphere [C]
MN: Fall Meeting 2005