| Abstract: | Early reports of conditions in Portage Pass, Alaska, provide evidence that Portage Glacier was formerly larger and thicker. Past conditions, recent history, current retreat, and possible future changes are summarized from an analysis of reports, photographs of the glacier (1939, 1950, and annually since about 1960), and data on snow and ice balance and bathymetry (1972). Between 1900 and 1972, the glacier terminus retreated 3.4 kilometers, and the lower part of the glacier thinned 200 meters. Climatic change controlled the retreat until about 1930; since then deep water at the terminus has influenced the calving retreat. The calving rate and present terminus position cannot be sustained by current climatic conditions and rate of snow accumulation. Thus the glacier will continue to recede until the terminus stabilizes in shallower water, probably about 1.5 kilometers upvalley from the present terminus and in about year 2020, assuming no change in present climatic conditions and calving rate. Possible small climatic changes could cause a shift in the point at which annual snow accumulation equals annual ablation (500 meters) and a corresponding change in terminus behavior. Potential natural hazards include avalanches, outburst floods from ice-dammed lakes, and unstable icebergs. (Woodard-USGS) |
| Genre: | USGS Numbered Series |
| ProdID: | 68175 |
| Citation Author: | Mayo, L. R.; Zenone, Chester; Trabant, Dennis |
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| Citation Language: | ENGLISH |
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| Citation LatN: | 0606000 |
| Citation LatS: | 0603000 |
| Citation LonE: | -1483000 |
| Citation LonW: | -1491000 |
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| Citation Phsyical Description: | 1 map on two sheets. |
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| Citation Series: | Hydrologic Atlas |
| Citation Series Code: | HA |
| Citation Series Number: | 583 |
| Citation Search Results Text: | Reconnaissance hydrology of Portage Glacier basin, Alaska--1972; 1977; HA; 583; Mayo, L. R.; Zenone, Chester; Trabant, Dennis |
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| Citation Year: | 1977 |
| Type: | citation/reference |
| Text: | Reconnaissance hydrology of Portage Glacier basin, Alaska--1972; 1977; HA; 583; Mayo, L. R.; Zenone, Chester; Trabant, Dennis |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/usgs_thumb.jpg |
| URL (PLATE): | http://pubs.usgs.gov/ha/583/plate-1.pdf |
| URL (PLATE): | http://pubs.usgs.gov/ha/583/plate-2.pdf |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
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