| Summary: | Abstract: Modern process studies conducted on Arctic glaciers provide valuable insight into dynamic responses observed in the high latitudes due to global scale climate change, with telltale implications for environmental change in the lower latitudes. This research was conducted on Spitsbergen, the largest island of Svalbard, as part of an NSF funded Research Experience for Undergraduates program. The Norwegian High Arctic, containing Svalbard, is influenced by the northern extent of the Gulf Stream and the advection of warm air and moisture to the high latitudes. Its position creates highly variable conditions which directly affect the mass balance of glaciers on Svalbard. Work by Hagen et al. (2003) calculated the surface mass balance of Svalbard to be -4.5+/-1 km3 Yr/1. Understanding the factors influencing glacier mass balance and quantifying ablation rates provides ground-truthed data to gauge the Arctic’s reaction to changing climatic conditions and its influence in the global climate system. A compilation of mass balance measurements, local meteorological data, stream gauge, and suspended sediment concentrations were studied over a five week period during the summer 2006 melt season. High resolution data was collected in 30-minute intervals and manual readings were taken at eight glacier ablation centerline stakes on Linnèbreen. Comparisons were made directly to meteorological data, affording assessment of the correlations between the local and regional weather data and the dynamic behavior of this glacier. Summer precipitation was found to be the main agent of surface lowering on Linnèbreen. Days of high precipitation correlate directly with days of greater surface lowering and peak suspended sediment in the meltwater stream. High rates of lowering are interpreted to be the result of latent heat release caused by meltwater and precipitation percolating down into and refreezing below the glaciers surface. This triggered the removal of overlying ice, providing a glassy surface until such time that eolian debris and new sediment could accumulate and melt in differentially due to contrasts in albedo. Sediment flux to the meltwater stream is derived by erosion of sediment liberated by prior glacial activity. Supply is dominated by active layer thawing around the meltwater stream, resultant of rising temperatures and precipitation induced high discharge. The rise and fall of discharge, allowing temporary storage in ice-marginal channels and braidplains, display a diurnal SSC trend. Linnèelva operates in a dominantly supply limited mode due to the lack of active glacial erosion, with signs of complete sediment depletion over the meltseason. Sedimentation rates are likely to rise as the active layer deepens around the proglacial meltwater stream due to rising temperatures, and proposed increases in the Arctic’s precipitation budget allow for high discharge events. A net mass balance of -1.14m water equivalent was measured for Linnèbreen in 2006, producing a volumetric melt of 0.0028km3. 93.6% of Linnèbreen’s mass now lies entirely below the modern ELA at 458m. Extensive mass loss, associated with the ice margin retreat of ca. 1200m from its maximum extent during the LIA, could signal a significant change in thermal regime from its previous inferred warm based structure. The vast supraglacial and ice marginal meltwater network strongly supports the instrumental data and conclusion that Linnèbreen is composed almost entirely of cold based ice. The 4-6°C warming at the end of this century proposed by Alley et al (2006), based on the literature and IPCC (2007), is expected to have vast consequences on Svalbard. These temperatures are over two times higher then values estimated for the warmer early Holocene by Hald et al. 2004 and Overpeck et al. 1997. The average ELA on the archipelago was calculated at ca. 450m by Hagen et al. (2003) coinciding with the altitude containing the most ice mass. Further warming, changes in moisture advection, and a freshening of the Arctic Ocean are expected to cause a rise in the regional ELA. This will result in accelerated deglaciation of Svalbard, a situation unprecedented during the Holocene.
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