Ten years of monthly mass balance of Conejeras glacier, Colombia, and their evaluation using different interpolation methods

摘要

Understanding global climate change and its impacts on glaciers in the inner tropics is challenged by an absent climate seasonality that requires glacier monitoring at increased frequencies. Conejeras glacier in Colombia has been monitored monthly for 10 years, contributing to the limited knowledge of glacier mass development in this region. We acquired a terrestrial Lidar digital elevation model (DEM) and performed a full homogenization of the time series. Applying a number of interpolation methods, we calculated glacier-wide balances and deduced respective uncertainties. All interpolation methods revealed comparable variations in monthly surface mass balance, but the profile method failed in certain cases. We recommend using the Index-site method for monthly and annual and the Contour-line method for annual surface mass balances. Even when strongly reducing the stake network, the Index-site method and geostatistical interpolations (Kriging and Topo to Raster) showed robust and reliable results. Conejeras glacier is strongly down-wasting with a mass loss of 29 400mm w.e. and an area shrinkage of 20% within 10 years. Surface mass balance variations were strongest from November to February and depend largely on the intensity of El Nino Southern Oscillation. With a repeat DEM in the near future the glaciological time series could be validated with the geodetic mass balance. We recommend continuing the monthly monitoring programme, but complementing it with an energy balance study using additional meteorological data to better explain the glacier-climate interactions. However, to track the glacier's mass variations, a monitoring network with lower measurement frequency and stake density would be sufficient.