| dc.description.abstract | Glaciers and ice masses are very important components of the earth system both in terms of global water storage and as climate indicators. The amount of water tied up in glaciers and ice caps is equivalent to about 69 meters of sea-level (Church and others, 2001). Recent predictions from global climate models indicate the arctic will experience enhanced changes as compared to the lower latitudes linked to the rise of greenhouse gases in the next 100 years (ACIA report, 2005). Svalbard glaciers and ice masses may therefore experience a rapid response to a change in climate (Hagen and others, 2003a). It is thus beneficial to document both present and the long term past glacier fluctuations to increase the comprehension of climatic changes.
Svalbard is a high arctic archipelago, located in a climatically sensitive area at the northern extremity of the warm North Atlantic ocean current. Approximately 36000 km2 is covered by glaciers consisting of ice caps, tidewater, outlet, and smaller cirque and piedmont glaciers (Hagen and others, 1993). In this study, a 54 year geodetic balance of Svalbard glaciers is derived by comparing the oldest topographic map series of Svalbard (1936/38) to modern digital elevation models (DEM) from 1990. The errors of the older maps are assessed where precision is limited, but accuracy is sufficient for glacier studies. Elevation changes are analyzed for 7 regions in Svalbard (~5000 km2), where significant thinning was found at glacier fronts, and elevation increases in the upper parts of the accumulation areas. All regions experience volume losses and negative geodetic balances, although regional variability exists relating to both climate and topography. Many surges are apparent within the elevation change maps. Estimated volume change for the regions is -1.59±0.07 km3a-1 (ice eq.) for a geodetic annual balance of -0.30 m a-1 (w. eq.), and the glaciated area has decreased by 16% in the 54 year time interval.
For recent balance estimations, differential GPS (2004) and laser altimetry (1996 & 2002) measurements are compared to the 1990 DEM over four glaciers in northwest Svalbard, and along two 60 km profiles in southern Svalbard. For both regions, the rate of frontal thinning has increased dramatically. The annual geodetic balances have become twice as negative for two smaller glaciers, Midtre and Austre Lovenbreen, while becoming more than three times more negative on the larger Kongsvegen. In southern Svalbard, while the glacier fronts are thinning faster in these recent measurements, complex dynamic behavior is occurring at higher altitudes, which complicate the elevation change signal. A number of dynamical events occurred in Wedel Jarlsberg Land between 1990 and 1996.
The glaciers of Svalbard are losing ice volume at a faster rate more recently which can be attributed to a changing climate. The large scale synoptic patterns in atmospheric and oceanic circulation, and possibly temporal changes associate with them, is leading to increased thinning at the glacier fronts and slight increases at higher altitudes. Climate change is not only affecting glacier surface change in the form of temperature, but also in the form of precipitation. These changes progress through the glacier creating complicated dynamic patterns. Nonetheless, the present glacial-climate signal is that of increased volume loss. | nor |