Quantification and consequences of glacier volume loss on meltwater fluxes and organic matter since 1971, Edgeøya, Svalbard.

Abstract

Due to increasing temperatures in the Arctic, the 36,000 km2 of glacier ice on Svalbard is decreasing rapidly. Consequently, this will affect meltwater fluxes and organic matter release, which influences the marine ecosystem. The organic matter in glaciers has its source by biological production, wind-blown dust and soil/bedrock erosion and can be degraded to the greenhouse gas CO2 when released in rivers and ocean. The aim of this research project is to quantify the changes in glacier volumes and its meltwater fluxes over the last 40 years and to characterize the organic matter in these glacial meltwater rivers at Svalbard. Ice volume estimates have been conducted for the years 1971, 2004 and 2014 by volume/area- scaling and a GIS approach based on Weertman’s sliding law. The ice area, based on remote sensing and topographic maps, is used to initialize and calibrate a cryospheric hydrology model to model the consequence of ice loss on meltwater flow. During the Dutch Scientific Expedition Edgeøya Spitsbergen (SEES) water samples of 13 of these glacial meltwater rivers have been collected. These samples are analyzed for stable isotopes in meltwater (δ2H and δ18O) and organic matter (δ13C), which elucidate the source of the water (glacial or snow) and organic matter (terrestrial or autochthonous), respectively. We also determine the total amount of organic carbon (dissolved and particulate) transport, as well as its molecular characteristics and its bioavailability. Results show over 40% ice volume loss since 1971 and all ice will be gone prior to 2100. The base flow and number of glacier melt days are slightly increasing from 1971 onwards. This suggests that glacier melt per unit area is increasing with time to counteract glacier area decline. Whether the total annual discharge is already declining due to area loss or if this is going to happen in the near future is unclear, since the modeled data is not verified with field data. In meltwater rivers we measured 0.5-5*103 mg/L of total suspended matter, containing 0.80-1.5% organic carbon. These values are low, which can be explained by the thin and poorly developed soils in this high-Arctic setting. Organic matter is mainly from terrestrial sources (-24‰ - -29‰). The source of the river water was mainly from glacier water. We estimate that the additional ice mass loss leads to an increase of 1.5Mton/yr organic carbon loading, important for near coastal zone ecosystems. These results help to assess the degree of sensitivity of these Arctic river systems for a warming future.