Geikie Inlet, Glacier Bay

Geikie Inlet, Glacier Bay

by | Dec 9, 2021

Geikie Inlet is a fjord about 8 miles (13 km) long that trends generally northeast from the mouth of the Geikie River to the western coast of Glacier Bay, in Glacier Bay National Park and Preserve, about 130 miles (209 km) southeast of Yakutat and 32 miles (51 km) northwest of Gustavus, Alaska. The Geikie River drains the eastern side of the Brady Icefield and flows about 5.5 miles (9 km) from the terminus of the Geikie Glacier to Geikie Inlet. The terminus of Geikie Glacier is now about 5.4 miles (9 km) inland from the head of the inlet. In 1879, John Muir observed Geikie Glacier when it still filled the inlet but after it had separated from Muir Glacier. He named the glacier for James Geikie, a Scottish geologist who worked with the British Geological Survey and then became professor of geology at Edinburgh University from 1882 to 1914. Geikie was the author of ‘The Great Ice Age and its Relation to the Antiquity of Man‘ and other geological publications. When Harry F. Reid visited Glacier Bay in 1892, he found that the Geikie Glacier had retreated to within several kilometers of the head of the inlet and had become two smaller glaciers. He retained the name ‘Geikie’ for the larger and more northerly of the two and called the other smaller glacier ‘Wood’. In 1910, Geikie Glacier retreated from tidewater. William O. Field with the American Geographical Society visited Geikie Glacier in 1935, 1941, 1950, and 1958, noting limited retreat from tidewater up to 1935, though considerable frontal thinning was evident. In 1950, the glacier had retreated 1.3 miles (2.1 km) from tidewater with a rate of 50 m/year, and the glacier was fed by four tributary glaciers. By 1986, the terminus had retreated 2.7 miles (4.3 km) from tidewater and the tributary glaciers had separated from the main ice stream. In 2014, 2015, 2018, and 2019 the entire glacier lost all of its snow cover, indicating that this glacier cannot survive since a consistent accumulation zone is essential. The demise of Geikie Glacier is less complete than that of nearby Wood Glacier which has now disappeared.

The retreat of continental ice sheets covering Glacier Bay following the Last Glacial Maximum was probably well underway by about 14,000 years ago. But during the Holocene, ice advanced and retreated several times into Glacier Bay from the Fairweather and Takhinsha Mountains. These cycles of advance and retreat may have begun as early as 10,000 years ago and were separated by periods of forest growth and soil development. The most recent advance occurred about 800 years ago during the Little Ice Age when ice from several major tributary glaciers coalesced and expanded southward, reaching a maximum extent in Icy Strait about 1750 AD. In 1794, the expedition of Captain George Vancouver was the first to observe and map the tidewater ice margin of the massive glacier emanating from Glacier Bay, which at that time was already retreating. The sustained retreat over 75 miles (120 km) of the glacier that had covered most of Glacier Bay started shortly after the mid-1700s and is one of the best documented in the world. The retreating glacier exposed forest debris from multiple intervals of ice advance during the Holocene, including logs and rooted stumps. Western hemlock and Sitka spruce logs found in Geikie Inlet were generally located within outwash plains and alluvial fans along the valley margins. Increment cores and sections were cut from these logs for tree ring dating and radiocarbon isotope aging to learn more about the history of Geikie Glacier and the inlet over the last two millennia. These data indicate that Geikie Glacier advanced periodically about 2800, 1900, 1100, and 500 years ago. The last advance was in response to the Little Ice Age maximum and involved the largest changes in relative sea level seen during the Holocene. The subsequent emergence of the coastal zone due to glacier retreat and post-glacial rebound is well-documented, with peak rates of 1.2 inches/yr (30 mm/yr), the fastest rate of uplift observed anywhere in the world.

Today, the vegetated slopes and valleys surrounding Geikie Inlet are home to a subspecies of the American black bear with silver-blue or gray hair formally named Emmons’ black bear but are also referred to as glacier bears or blue bears. The color variant was first reported by William Healey Dall in 1895 and is endemic to Southeast Alaska, although color variants in black bears are not uncommon. White colored bears were documented in the Pacific Northwest as early as 1805, during the Lewis and Clark Expedition. In the 19th century, British Columbia indigenous people called white bears ‘Spirit bears’ and were known to bring in white bearskins to fur traders. The white fur coloration in bears is caused by a single recessive gene that is involved in melanin production. Melanin is primarily responsible for the pigmentation of the skin, hair, and eyes of humans and other animals. The chemistry produced by this gene causes some bears to have white or black fur. If both a female and male have the recessive gene, one of their four offspring will have white hair and two of them will have recessive genes for white hair. A white-furred bear mating with a bear with the recessive gene will have two white bears and two with the recessive gene. There are also other genes related to thyroid hormone production that create combinations of white and black fur colors in bears. Because of genetic variation, there is a greater propensity for certain color variations to be located in specific regions. Pale blue-grey, colored individuals of a black bear litter were more common near glaciers in the area from Mount Saint Elias to the Skeena River and hunters often called these ‘glacial bears’. George Emmons recorded observations of Tlingit hunters in the 1890s who called glacier bears ‘klate-utardy-seek’ meaning ‘snow-like black bear’. In the early 1900s, Frederica De Laguna learned from the Tlingit that black bears found along coastal glaciers were much smaller than the ordinary American black bear, and in addition to the usual black and brownish colors, many from the same litter are blue-gray or maltese. At that time, there was an over-abundance of new species and subspecies of bears named on the basis of sometimes flimsy physical evidence. For example, in 1905, the naming and promotion of black bears with the recessive genes for white fur were mistakenly given status as a separate species called the Kermode bear after the Royal British Columbia Museum director Frank Kermode. Read more here and here. Explore more of Geikie Inlet here:

About the background graphic

This ‘warming stripe’ graphic is a visual representation of the change in global temperature from 1850 (top) to 2022 (bottom). Each stripe represents the average global temperature for one year. The average temperature from 1971-2000 is set as the boundary between blue and red. The color scale goes from -0.7°C to +0.7°C. The data are from the UK Met Office HadCRUT4.6 dataset. 

Credit: Professor Ed Hawkins (University of Reading). Click here for more information about the #warmingstripes.

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