Speaker : Sebastian H. Mernild
  Summary : Ample evidence indicates the Arctic climate, cryosphere, and hydrological cycle is changing. Fluctuations in surface melt extent, mass balance, and freshwater runoff from the Greenland Ice Sheet (GrIS), and glaciers and ice caps (GIC) peripheral to the Ice Sheet, follows climate fluctuations, and response has already been observed and marked by glaciers retreating and thinning along the periphery. Most GIC are out of balance with the current climate, and farther from balance than previously believed. GIC peripheral to GrIS will likely lose at least 70% of its current area and 80% of its volume even in the absence of further climate changes. For GrIS, a high-resolution (5-km) model was used to simulate surface melt extent and trends before the satellite era (1960-1979) and during the satellite era through 2010. The period 1960-1972 had a 6% average decrease in melt extent, and 1973-2010 had an increase of 13%, with record melt extent in 2010. The runoff contribution to the ocean is likely playing a role in global eustatic sea level rise, and thermohaline circulation in the Greenland-Iceland-Norwegian Seas. Presently, we lack detailed information about the spatial and temporal runoff distribution to the ocean from non-glaciated and glaciated areas in Greenland. Runoff hydrographs at catchment outlets were simulated and represents an integrated response of the upstream watershed to precipitation and hydrometeorologic snow and ice processes. Total Greenland runoff to the surrounding oceans averaged 48185 km3 y-1 from 1960 through 2010. Overall, Greenland runoff increased by 30% since 1960. Averaged over the period, 70% of the runoff to the surrounding seas originated from the GrIS, and 30% came from outside the GrIS from melting glaciers and ice caps, and rain. Regionally, average runoff was greatest in the western regions than in the eastern regions of Greenland, with a pronounced runoff increases in western regions, with the greatest increases occurring in the southwest and the lowest increases found in northwest Greenland.