Glacier Bay Basin - Geography

Geography

Glacier Bay is subsumed within the larger about 3.3-million-acre (13,000 km2) National Park and Preserve. The preserve, which is a spectacular ensemble of marine and terrestrial life, is delimited by: The Tongass National Forest borders on the east and north east; by the international boundary with Tatshenshini-Alsek Wilderness Provincial Park in British Columbia, Canada on the north; by the waters of Cross Sound and Icy Strait border on the south; and by the Pacific Ocean on the west. When President Calvin Coolidge declared the Glacial Bay to be a national monument, in 1925, the objective clearly stated was:

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"a number of tidewater glaciers ... in a magnificent setting of lofty peaks ...; a great variety of forest covering consisting of mature areas, bodies of youthful trees which have become established since the retreat of the ice which should be preserved in absolutely natural condition, and great stretches now bare that will become forested in the course of the next century; a unique opportunity for the scientific study of glacial behavior and of resulting movements and developments of flora and fauna and of certain valuable relics of interglacial forests; historic interest, having been visited by explorers and scientists since the early voyages of Vancouver in 1794 who left valuable records of such visits and explorations. "

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The Alaska National Interest Lands Conservation Act of 1980 changed its status to a National Park and Reserve covering an area of 3,283,000 acres (1,329,000 ha) including 57,000 acres (23,000 ha) as a preserve: However,2,670,000 acres (1,080,000 ha) have been declared as Wilderness. The Glacier Bay also encompasses about 400 acres (160 ha) of two mining claim groups, and about 3,000 acres (1,200 ha) allotted to Alaska Natives; some small private tracts are also reported within the limits of the Glacier Bay.

The Glacier Bay Basin is now a myriad combination of tidewater glaciers, snow-capped mountain ranges, ocean coastlines, deep fjords, and freshwater rivers and lakes that provide widely varying land and seascape and “hosts a mosaic of plant communities and a variety of marine and terrestrial wildlife.”

Glacier Bay is covered with 1,375 square miles (3,560 km2) of glaciers which accounts for 27% of the Park area with most glaciers originating in mountains with elevation range of 8,000–15,000 feet (2,400–4,600 m). There are over 50 named glaciers (both tidewater and terrestrial glaciers); 10 tide water glaciers - one on the east arm of the bay and all others on the west arm reach shorelines and calved) (literal meaning: "breaking off") to produce icebergs. Seven of these glaciers are reported to be active tidewater glaciers, which depict the calving phenomenon, which means that they break into icebergs and fall into the sea with thundering noise raising large waves. The McBride Glacier is the only tidewater glacier in the eastern arm at a distance of 40 nautical miles (74 km) from Bartlett Cove. Of the other glaciers on the western arm, Johns Hopkins Glacier is at the farthest end – 63 nautical miles (117 km) from the entrance to the bay while the Margerie Glacier is about 55 nautical miles (102 km) away.

The National Park Service manages a total of 607,099 acres (245,684 ha) of marine waters of the Glacier Bay. It covers a coastline of 1,180 square miles (3,100 km2) including some reach of the coast outside the Bay. Glacier Bay Basin as such has a coast line of 760 square miles (2,000 km2) including all islands; the coast line without counting islands accounts for statute 563 miles (906 km). The deepest point in the bay is 1,410 feet (430 m) below sea level with the diurnal tides occurring every 6 hours, with a tide range of -5–18 feet (−1.5–5.5 m) (upper limit of the range is reported to be23 feet (7.0 m).

According to the recorded findings, most glaciers are retreating except the Johns Hopkins Glacier, which is advancing and the Margerie Glacier which is stable. The glacier thinning or retreating process is attributed to lesser incidence of snowfall on the hills, raising temperatures in the winter season followed by decrease in cloud cover and precipitation during the summer season.

A Research ship of NOAA in the Glacier Bay

Post Little Ice Age Rebound in the Glacier Bay Basin has been studied by researchers of the Geophysical Institute, University of Alaska Fairbanks, Alaska in association with National Park and Preserve Service, under a National Science Foundation grant using GPS geodesy combined with studies of raised shorelines and tide gauges. The studies have established that the fastest rates of glacier rebound in the world are now taking place in the Glacier Bay region. The studies have also reported that “these adjustments to LIA loading and unloading are producing significant stresses on the earth’s crust which can affect seismicity and regional tectonics. The rising land also is continually changing the geomorphic texture of shoreline throughout the Park and causing changes in hydrologic patterns, erosion, and sedimentation. All these changes have a direct impact on the ecosystems of the Park."

Glacier Bay can be approached only by boats or ships and partly by hiking along three trails (10 miles (16 km)) and by kayaking along 700 miles (1,100 km)) of shore line. The nearest road head and airport are in the small town of Gustavus, which is known as the southern gateway to the Glacier Bay. However, Gustavus as such is approachable only by air and sea. Juneau, the capital of Alaska, is about 60 miles (97 km)). The approximate distance between Anchorage and Juneau is 567 miles (912 km)}.

The advancing and retreating characteristics of the glaciers in the Glacier Bay are explained in simple terms as a steady state of snow getting converted into ice on the hills. Ice, as a lens of water on the base of bedrock, slides by gravity downwards. The good moraine of rock and rubble insulates it from water erosion. As a result, during freezing temperatures that exists all the year, the glacier advances. When the insulation and erosion effect of the hills gets reduced erosion sets in and along with rising temperatures the glaciers start retreating. Another unpredictable phenomenon that is observed in many glaciers in the Glacier Bay is that of calving. Calving is a process in which blocks of ice get detached or break off from the glacier, irrespective of weather conditions, all the year round, and crash into the sea with thundering noise creating a boiling like turbulence.

The Glacier Bay was closed for ships almost a decade after the 1899 earthquake (magnitude 8.4 on the Richter Scale). This was on account of the shattered ice blocks which filled the Bay consequent to the earthquake. Even though the Bay is in volcanic activity region of the Pacific "Rim of Fire", active volcanoes have not been recorded within the Glacier Bay Basin. However, these two factors have been inferred to have effects on the environmental changes occurring in the Glacier Bay.