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Monday, March 02, 2009
10:30 AM - 11:30 AM
CNLS Conference Room (TA-3, Bldg 1690)

Seminar

Greenland Runoff from Observations to Modeling

Sebastian Mernild
International Arctic Research Center and Water & Environmental Research Center, University of Alaska Fairbanks

The freshwater flux from the Greenland Ice Sheet (GrIS) to the ocean is of considerable importance to the global eustatic sea level rise. A novel physically approach a state-of-the-art snow-evolution modeling system SnowModel was used to quantify the GrIS surface melt extent, surface mass-balance (SMB), including the freshwater flux for the period 1995 through 2007. The modeled GrIS SMB was merged with previous GrIS subglacial runoff (from geothermal melt) and GrIS calving studies in order to quantify the GrIS freshwater flux to the ocean. Meteorological observations from 25 meteorological stations located on the GrIS and in the coastal area were used as model input. A minimum GrIS surface melt extent of 29% occurred in 1996, while the greatest extent of 51% was present in 2007. The 2007 melt extent was around 20% greater than average extent for the period 1995 through 2006. Further, 2007 had the greatest GrIS runoff of 523 km3 y-1 and the lowest SMB of -3 km3 y-1 the only year with a negative GrIS SMB. The 2007 runoff was approximately 35% greater than average runoff for the period 1995 through 2006. The precipitation rate decreased while ablation increased from 1995 through 2007, showing an increasing average SMB loss of 127 km3. SMB, geothermal melting, and iceberg calving from the GrIS indicates a net mass-balance loss, averaging 265(83) km3 y-1 for the period. For the highest ablation year 2007, the GrIS mass loss was 392 km3 y-1, or 54% greater than the average loss for the period 1995 through 2006. This study suggests an average GrIS freshwater flux of approximately 786 km3 y-1 to the Ocean, where 45% occurs from iceberg calving and geothermal bottom melting. The average annual GrIS freshwater flux equals 2.10.2 mm w.eq. y-1 in eustatic sea level rise, indicating a cumulative flux of 28 mm w.eq. from 1995 through 2007. The average GrIS net loss contributes to a net sea level rise of 0.70.2 mm w.eq. y-1, indicating a cumulative net increase on 10 mm w.eq.

Host: Matthew Hecht, CCS-2