The Greenland ice sheet loses mass due to changing surface mass balance, direct melting on the surface, ice flow through the numerous outlet glaciers, and basal melt. My Ph.D. thesis focuses on the outlet glaciers terminating in Godthaabsfjord near Nuuk in West Greenland, with Kangiata Nunaata Sermia (KNS) being the main contributing glacier. The mass loss of this glacier forms a small contribution to the total mass loss of the Greenland ice sheet, but it will have a large impact on the local ecosystem when there is a large freshwater flux into the fjord. Here, two independent methods are used to estimate the total mass loss by KNS and its neighboring outlets, namely an ice sheet model applied to KNS and stable oxygen isotope measurements in the fjord. The Parallel Ice Sheet Model (PISM) is applied to model current and future mass loss. A parameter study is conducted to select the best parameter settings matching observed surface velocities and observed ice thickness. A monthly mean climatic forcing is applied to these best settings to investigate the individual components of the total fluxes. The model reproduces the present behavior of KNS. Also, seasonal variations are modeled. The modeled solid ice flux, surface velocities, and total mass flux agree well with the observed surface velocities, calving flux estimates, and elevation changes.Also, available data on freshwater fluxes from land and glaciers and measurements of salinity and stable oxygen isotopes in Godthaabsfjord, taken between 2007 and 2010, are used in order to determine the relative contribution from the various freshwater sources into the fjord. To this end, the seasonal signal of salinity and stable oxygen isotopes is analyzed.A box model is used to compute the freshwater contributions from the glaciers from oceanographic measurements.

In the ECAL group of the CMS detector.