HYDROLOGICAL AND BIOGEOCHEMICAL RESPONSE OF A HIGH ARCTIC GLACIERIZED CATCHMENT TO CLIMATE CHANGE; A LONG TERM STUDY FROM BAYELVA WATERSHED; SVALBARD

This thesis examines the Bayelva watershed (Svalbard) between 1974 and 2010 in order to investigate its response to climate change. Hydrological changes are revealed that are most significant during the last ten years, when winters have become warmer and wetter. Water balance modelling shows that more rainfall is offsetting any reduction in flow caused by continued glacier shrinkage. An optimised water budget for 1974/75 to 2009/10 shows that inter-annual changes in water storage can no longer be ignored, despite permafrost and cold-based glaciers being present. Hydrograph analysis suggests that since the transfer of meltwater through the channel network is becoming increasingly efficient, then the deepening active layer is responsible for the new delayed water flowpaths.
To explore the biogeochemical consequences of the above hydrological changes, long-term datasets in Bayelva were examined and new data from separate moraine, talus and soil micro-catchments were collected. Unlike the main river, a significant microbial effect upon runoff geochemistry was seen in all the micro-catchments, causing high NO3- and SO42- concentrations and contributing to high pCO2, especially during end of summer low flows. Evidence for the deepening active layer was clear in the soil micro-catchment, because uplifted marine sediments were found to enrich runoff Cl- concentrations. However, the recently exposed glacier forefield emerges as the most chemically active part of the watershed, for example, when causing a prolonged “flush” of ions and significant pCO2 depletion following sudden channel migration at the immediate glacier margin. In addition, solute acquisition from glacial sediments in the downstream floodplain contributes significantly to watershed solute export. This means that the overall watershed biogeochemical response to climate change is dominated by a ‘glacial signal’ resulting from rapid chemical weathering reactions. Therefore, understanding Arctic landscape biogeochemical response to climate change can only be uncovered by studying small-scale environments within it.