Juneau Icefield

View of the Juneau Icefield.

The Juneau Icefield is an ice field located just north of Juneau, Alaska, continuing north through the border with British Columbia, extending through an area of 3,900 square kilometres (1,500 mi2) in the Coast Range ranging 140 km (87 mi) north to south and 75 km (47 mi) east to west. The icefield is the source of many glaciers, including the Mendenhall Glacier and the Taku Glacier. The icefield is home to over 40 large valley glaciers and 100 smaller ones. The Icefield serves as a tourist attraction with many travellers flown in by helicopter for quick walks on the 240-to-1,400-metre (790 to 4,590 ft) deep ice and the massive, awe-inspiring moist crevasses.

Glaciers

Locational map of major features of the Alaska Panhandle area including the Juneau Icefield in the northern portion.

Eight kilometers to the north, the Herbert Glacier has retreated 540 m (0.34 mi), while Eagle Glacier retreated 700 m (0.43 mi), Gilkey Glacier 3,500 m (2.2 mi) and Llewellyn Glacier 2,800 m (1.7 mi). On the south side of the icefield, the Norris Glacier retreated 1,740 m (1.08 mi), the East Twin Glacier 1,100 m (0.68 mi), the West Twin Glacier 570 m (0.35 mi) with only the Taku Glacier advancing. Surveys reveal the Taku as one of the deepest glaciers of the sub-temperate icefields surveyed at nearly 1,370 metres (4,490 ft) thick.

History

In 1890, John Muir viewed Taku Glacier from a steamer in Taku Inlet and described an iceberg-calving front about three-quarters of a mile wide. The first United States Coast and Geodetic Survey chart of the inlet, also made in 1890, shows the glacier ending at the head of a deep tidal basin. Between 1890 and 1948, the glacier advanced 5.3 km (3.3 mi), and sediment gradually filled the once-deep tidal basin in front of it. Calving had largely ceased by about 1950, after the glacier's sediment moraine rose above the water surface.

From 1948–1986, the glacier had a positive glacier mass balance driving the advance. From 1987–2009, the glacier has had a slightly negative mass balance, not enough to end the advance, but if it continues will soon slow it.[citation needed]

The icefield, like many of its glaciers, reached its maximum glaciation point around 1700 and has been in retreat since.[citation needed] Much of the icefield is contained within the Tongass National Forest. Since 1948, the Juneau Icefield Research Program has monitored glaciers of the Juneau Icefield. On the west side of the icefield, from 1946 to 2009, the terminus of the Mendenhall Glacier has retreated over 700 metres (0.43 mi).

Peaks

Notable peaks on the Juneau Icefield are Devils Paw, Nelles Peak, Emperor Peak, The Snow Towers, Taku Towers, Camp 15 Peak, and the Mendenhall Towers.

See also

References

  1. ↑ "Juneau Icefield Research Program". www.juneauicefield.org.
  2. ↑ Nolan, Matt; Motkya, Roman J.; Echelmeyer, Keith; Trabant, Dennis C. (1995). "Ice-thickness measurements of Taku Glacier, Alaska, U.S.A., and their relevance to its recent behavior". Journal of Glaciology. 41 (139): 541–553. doi:10.3189/S0022143000034870. ISSN 0022-1430.
  3. ↑ Muir, John (1915). "In Camp at Glacier Bay". Travels in Alaska. Houghton Mifflin.
  4. 1 2 Motyka, Roman J. (April 1989). Taku Glacier Advance – Preliminary Analysis (PDF) (Report). Public-data File 89-12. Alaska Division of Geological & Geophysical Surveys.
  5. ↑ Pelto, M. S.; Miller, M. M.; Adema, G. W.; Beedle, M. J.; McGee, S. R.; Sprenke, K. F.; Lang, M. (2008). "The equilibrium flow and mass balance of the Taku Glacier, Alaska 1950–2006". The Cryosphere. 2 (2): 147–157. doi:10.5194/tc-2-147-2008.
  6. ↑ McNeil, Christopher; Amundson, J. M.; O'Neel, S.; Motyka, R. J.; Sass, L.; Truffer, M.; Zechmann, J. M.; Campbell, S. (18 February 2021). "The imminent calving retreat of Taku Glacier". Eos. 102. doi:10.1029/2021EO154856.
  7. ↑ Pelto, M.; Kavanaugh, J.; McNeil, C. (2013). "Juneau Icefield Mass Balance Program 1946–2011". Earth System Science Data. 5 (2): 319–330. doi:10.5194/essd-5-319-2013.

58°36′N 134°30′W / 58.600°N 134.500°W / 58.600; -134.500