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Slides courtesy of Jason E. Box Department of Geography Byrd Polar Research Center The Ohio State University Columbus, Ohio, USA Research supported by Greenland Ice Sheet Slide 2 Orientation 2.16 x 10 6 km 2 2.16 x 10 6 km 2 81% ice covered 81% ice covered 3 x Texas 3 x Texas 10% global land ice 10% global land ice 7.4 m sea level equivalent 7.4 m sea level equivalent Max elevation of 3208 m @ Summit Max elevation of 3208 m @ Summit Greenland Slide 3 3 http://en.wikipedia.org/wiki/File:Geography-of-greenland.svg Slide 4 4 The surface slope over most of the Greenland Ice Sheet is barely 1 o, but is much greater at the margins which is also characterized by numerous fiords and associated valley glaciers that drain the ice sheet. Greenland has an estimated ice volume of is 2.93 10 6 km 3 and is the source of most of the icebergs found in the North Atlantic. Slide 5 5 With adjustment for isostatic rebound, the water locked up in the Greenland Ice Sheet corresponds to an approximate global sea level equivalent of 7.2 m. At present, 88% of the coterminous ice sheet lies in the accumulation zone (where annual mass gains exceed mass losses), with the other 12% lying in the ablation zone (where annual mass losses exceed more than loss gains). Slide 6 6 Beginning in 1987, an automatic weather station (AWS) network was established in Greenland. Data from these stations provide a valuable addition to the few previous expedition measurements. The high elevation, large extent and high albedo of the ice sheet are significant factors for local and regional surface air temperatures although latitude and distance inland are also involved. Slide 7 7 For both the eastern and western slopes of the ice sheet, surface air temperatures (SATs) decrease by about 0.8 o C per degree of latitude and by about 0.71 o C per 100 m. The ice sheet is characterized by pronounced low-level inversions, which are most strongly expressed during winter. February tends to be the coldest month in Greenland. For instance, at Summit, summer maxima reach -8 o C, whereas winter minima attain -53 o C; however, there is strong daily variability in winter, which is associated with synoptic activity and katabatic winds. Slide 8 8 Coastal Weather Stations Upernavik, 2005 Greenland Weather Station, 1945 Slide 9 9 Greenland Climate Network (GC-Net) Automatic Weather Stations (AWS) Steffen, K. and J.E. Box, 2001: Surface climatology of the Greenland ice sheet: Greenland Climate Network 1995-1999, J. Geophys. Res., 106(D24), 33951-33964. Slide 10 10 NGRIP Slide 11 Slide 12 12 Box, J.E., Survey of Greenland instrumental temperature records: 1873- 2001, International Journal of Climatology, 22, 1829-1847, 2002. Slide 13 13 Annual Surface Air Temperature Box, J.E., Survey of Greenland instrumental temperature records: 1873- 2001, International Journal of Climatology, 22, 1829-1847, 2002. Slide 14 14 January Surface Air Temperature Box, J.E., Survey of Greenland instrumental temperature records: 1873- 2001, International Journal of Climatology, 22, 1829-1847, 2002. Slide 15 15 Source: Serreze and Barry (2005) Slide 16 16 A prominent feature of the Greenland climate, just as in Antarctica, is its katabatic wind regime; dynamically, katabatic winds in Greenland are the same as those found in Antarctica. They relate to flows that are forced by radiational cooling of the lower atmosphere adjacent to the sloping terrain on the ice sheet. Greenlands katabatic winds, while not greatly influenced by topography, tend to flow with a pronounced component across the fall line because of the Coriolis force; however, winds near the coast are channeled by valleys and fiords. Slide 17 17 Measurements at Swiss Camp during 1990-99 yield a maximum monthly mean wind speed of 9-11 m s -1 during November-January, and a minimum of 5 m s -1 in July, with the prevailing wind direction is from 120-130 o, reflecting a katabatic regime. Winds show strong directional constancy over most of the ice sheet. Slide 18 18 Snow Transport 1991-2000 Box, J.E., D. H. Bromwich, L-S Bai, 2004: Greenland ice sheet surface mass balance for 1991-2000: application of Polar MM5 mesoscale model and in-situ data, J. Geophys. Res., Vol. 109, No. D16, D16105, 10.1029/2003JD004451. Slide 19 19 Direct observations of Greenland precipitation are particularly scant, with long records are limited to the coasts. In recent years, data over the ice sheet have been acquired from automatic stations. The main features of precipitation distribution over Greenland are very low accumulation ( 58 This loss of the Greenland Ice Sheet would be irreversible without major cooling. In contrast, important mass loss from surface melting of Antarctic ice is not expected in existing scenarios, although grounding-line retreat along the major ice shelves is modeled for basal melting rates >5 to 10 m yr -1, causing the demise of WAIS ice shelves after a few centuries and retreat of coastal ice toward more firmly grounded regions after a few millennia, with implied rates of sea-level rise of up to 3 mm yr -1. Slide 59 Estimates of Global Sea Level Rise from Tide Gauge Records 1.5( IPCC, 2001) The University of Texas at AustinThe University of Texas at Austin, Center for Space Research Slide 60 Leuliette, E. W, R. S. Nerem, and G. T. Mitchum, 2004 : Calibration of TOPEX/Poseidon and Jason altimeter data to construct a continuous record of mean sea level change. Marine Geodesy, 27(1-2), 79-94. Slide 61 61 (Source: Alley et al., 2005). Slide 62 62 (Source: Alley et al., 2005).