Abstract
Abstract. This study provides insights into surface mass-balance (SMB) and runoff exiting the Watson River drainage basin, Kangerlussuaq, West Greenland during a 30 year period (1978/1979–2007/2008) when the climate experienced increasing temperatures and precipitation. The 30-year simulations quantify the terrestrial freshwater output from part of the Greenland Ice Sheet (GrIS) and the land between the GrIS and the ocean, in the context of global warming and increasing GrIS surface melt. We used a snow-evolution modeling system (SnowModel) to simulate the winter accumulation and summer ablation processes, including runoff and SMB, of the ice sheet: indicating that the simulated equilibrium line altitude (ELA) was in accordance with independent observations. To a large extent, the SMB fluctuations could be explained by changes in net precipitation (precipitation minus evaporation and sublimation), with 8 out of 30 years having negative SMB, mainly because of relatively low annual net precipitation. The overall trend in net precipitation and runoff increased significantly, while SMB increased insignificantly throughout the simulation period, leading to enhanced precipitation of 0.59 km3 w.eq. (or ~60%), runoff of 0.43 km3 w.eq. (or ~55%), and SMB of 0.16 km3 w.eq. (or ~85%). Runoff rose on average from 0.80 km3 w.eq. in 1978/1979 to 1.23 km3 w.eq. in 2007/2008. The GrIS satellite-derived melt-extent increased significantly, and the melting intensification occurred simultaneously with the increase in local Kangerlussuaq runoff, indicating that satellite data can be used as a proxy (r2=0.64) for runoff from the Kangerlussuaq drainage area.
Highlights
Snow, glacier ice, and frozen ground influence runoff processes throughout the Arctic
The response has been manifested by an increasing surface melt extent, peripheral thinning, accelerating mass loss – especially in northwest Greenland, and increasing freshwater runoff
Our objectives were related to the changes in climate: (1) to simulate the variations and trends in the surface-water-balance components: precipitation, changes in storage, and freshwater runoff for the Kangerlussuaq catchment, and address whether Kangerlussuaq runoff can be used as a proxy for the whole Greenland Ice Sheet (GrIS) runoff; (2) to estimate the percentage of catchment runoff explained by GrIS runoff; and (3) to compare satellitederived GrIS melt-extent changes with the local Kangerlussuaq simulated runoff patterns to illustrate the link between surface melt and freshwater runoff, and whether satellite data are useful proxies of runoff from the Kangerlussuaq drainage area
Summary
Glacier ice, and frozen ground influence runoff processes throughout the Arctic. Significant responses in the structure and function of Arctic landscapes are likely, to occur in a warming climate (McNamara and Kane 2009). The Greenland Ice Sheet (GrIS) – the largest terrestrial permanent ice- and snow-covered area in the Northern Hemisphere – is sensitive to changes in the climate. Observational and model-based studies of the GrIS have provided intriguing insights into a system-wide response to climatic change and the effects of a warmer and wetter climate on cryospheric and hydrologic processes. Mernild et al.: Runoff and mass-balance simulations from the Greenland Ice Sheet at Kangerlussuaq
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