Modeling present hydrological conditions as a key to predict the future - results from a case study of a periglacial catchment in Greenland

Abstract:

The routing of water through periglacial landscapes is closely connected to the presence of permafrost, and freezing and thawing processes. To predict responses in the landscape to climate driven changes, we need to better understand the present day hydrology. The present hydrological processes, and the uncertainties in the data used to describe them, must be investigated and understood before we can develop models describing possible future conditions. In this work we have studied the hydrology of a catchment in the Kangerlussuaq region, Greenland. Johansson et al. (2015) presented a hydrological model of the catchment based on a new hydrological and meteorological data set from the catchment area. The present water balance was quantified, and the spatial and seasonal dynamics of the main hydrological fluxes were presented. It was shown that the model was able to reproduce the measured lake level dynamics and the measured components of the water balance. Based on this work we have used the numerical model to investigate the sensitivity in hydrological responses to different meteorological, geological and geometrical model input data. The aim with this study is to investigate the importance of the use of local data, but also to highlight the importance of present day site understanding when developing and applying the model for predicting responses to a changing climate. The results show that the site specific model is highly sensitive to the meteorological input data. Driving the model with precipitation data from a meteorological station only 30 km away from the catchment instead of local data from the studied catchment, or using local precipitation data not corrected for wind and adhesion losses, resulted in large discrepancies between measured and calculated lake levels. The modelled intra-annual dynamics of the active layer groundwater was shown to be sensitive both to the applied soil temperatures but also to the active layer depth and sediment stratigraphy.