![]() During the most recent glacial interval, which culminated about 20,000 y ago, the Ahklun ice cap covered approximately 15,800 km 2 and by about 12,000 y ago, it had receded in response to warming climate ( Manley et al. 2001), sculpting the deeply scoured landscape of the range. The Ahklun ice cap advanced and retreated during multiple glacial–interglacial cycles of the Pleistocene ( Kaufman et al. Study Area and Backgroundĭuring the late Pleistocene Epoch, the Ahklun Mountains supported an extensive ice cap ( Manley and Kaufman 2002 Figure 1) disjunct by >100 km from the Cordilleran Ice Sheet, which covered most of southern Alaska ( Kaufman and Manley 2004). In this study, we conducted an inventory of glaciers remaining in the Ahklun Mountains, quantified the extent and rate of change in glacier coverage since 1957, and predicted the duration of glacier persistence. Molnia (2008) summarized the known status of the Ahklun Mountain glaciers, concluding that all glaciers there have lost mass since 1984. (2010) conducted a digital inventory of Alaskan glaciers using a sequential digital elevation model analysis, refining the sea-level contributions estimated by Arendt et al. (2002) used laser altimetry to measure elevation change on 67 Alaskan glaciers, only one of which occurred in the Ahklun Mountains, and quantified their contribution to sea level rise. He found 106 glaciers with a median size of 0.26 km 2 and a total area of 59.6 km 2. Geological Survey (USGS) topographic maps, to calculate 32 physical parameters of the Ahklun Mountain glaciers, including area and elevation. Manley (1999 see also Molnia 2007, 2008) used a geographic information system (GIS) applied to digital elevation models, which were based on 1970s U.S. (1998), who found that the terminus had retreated at an average rate of approximately 21 m/y and that the glacier's area had decreased by approximately 9% over the 39-y period. Chikuminuk Glacier, the largest Ahklun Mountain glacier, was mapped in 1957 ( American Geographical Society 1960) and then resurveyed in 1996 by Sapiano et al. However, the Ahklun Mountain glaciers in southwestern Alaska are relatively unstudied. There are comprehensive hydrological and glaciological data available for approximately 100 glaciers globally ( World Glacier Monitoring Service and National Snow and Ice Data Center 2012) and about 198,000 glaciers (most of the glaciers of the world) have more limited archival data of some key properties ( Arendt et al. As glacial ice is diminished, the moderating influence of glaciers is also weakened, likely resulting in a shift in peak discharge from summer to spring and possibly a reduction in summer flows (Jiménez Cisneros 2014). When in equilibrium, glaciers reduce interannual variability of water by storing water during cold years and releasing it during warm years (Jiménez Cisneros 2014). Glaciers strongly affect the discharge of sediment and water downstream, and thereby influence the ecology of riparian and lacustrine habitats within their drainage basins. For southwestern Alaska, however, it is likely that the largest impacts of glacier diminution are ecological. These documents emphasize that most glaciers are in precipitous decline, and with their decline, some regions will or are already experiencing significant impacts on water resources. 2014) and the 5th Assessment of the Intergovernmental Panel on Climate Change ( Vaughan et al. The links between climate change and water supplies were underscored for the United States and the world as a whole by the recent National Climate Assessment ( Walsh et al. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |