Baird Glacier, Thomas Bay

Baird Glacier, Thomas Bay

by | Mar 22, 2022

Baird Glacier starts in the Stikine Icefield in the Boundary Ranges of the Coast Mountains near the Alaska-British Columbia border, and flows generally southwest for 24 miles (39 km) to its terminus at an outwash plain 2 miles (3.2 km) north of the head of Thomas Bay, about 100 miles (162 km) southeast of Juneau and 22 miles (35 km) north-northeast of Petersburg, Alaska. Thomas Bay extends about 10 miles (16 km) northeast into the Coast Mountains from Frederick Sound. The bay was named for Lieutenant Commander Charles M. Thomas of the U.S. Navy who commanded the U.S. Coast and Geodetic Survey Carlile P. Patterson from 1887 to 1889. The glacier was named in 1887 by Thomas for Spencer F. Baird, a pioneer American naturalist noted for his studies of North American birds and for being the Secretary of the Smithsonian Institution from 1850-87, and U.S. Commissioner of Fish and Fisheries from 1871-87. The Coast Mountains consists of three subdivisions known as the Pacific Ranges, the Kitimat Ranges, and the Boundary Ranges with the latter being the largest and most northerly subrange. The Boundary Ranges are formed by granitic intrusions generally called the Coast Mountains Batholith, or the Coast Plutonic Complex, that are remnants of a Late Cretaceous volcanic arc system called the Coast Range Arc. The batholith now separates the Stikine terrane to the east from the Alexander terrane to the west. The Stikine Icefield and the Baird Glacier overlies the Coast Plutonic Complex, represented by a sill consisting mostly of tonalite and quartz diorite that intruded in Late Cretaceous and Paleocene on the geological time scale during the last stages of deformation and metamorphism in the Coast Mountains. Much of the Alexander Archipelago of Southeast Alaska is underlain by the Paleozoic and Early Mesozoic rocks of the Alexander terrane that collided and accretion to the western margin of the Stikine terrane during the mid-Cretaceous about 100 million years ago. Metamorphism and plutonism accompanied and followed the accretionary event and contributed to the evolution of the Coast Plutonic Complex. The metamorphic rocks of the Alexander terrane that underlies Thomas Bay and are associated with the formation of the Coast Plutonic Complex are called the Ruth Assemblage. One notable plutonic rock formation in the headwaters of the Baird Glacier is Devils Thumb or Taalkhunaxhkʼu Shaa in the Tlingit language. This peak rises above the Stikine Icefield and is named for its projected thumb-like appearance. The name in the Tlingit language means ‘the mountain that never flooded’ and is said to have been a refuge for people during the mythical Great Flood.

Various ancient cultures of indigenous people have continuously occupied present-day Southeast Alaska for roughly 10,000 years. Tlingit oral histories tell of movement out of their Stikine homeland at a time when the fjords and straits were generally ice-filled, and they encountered a more ancient people on the coast that were either defeated or assimilated. An abundance of alpine cairns were reported shortly after World War II as a commonly encountered feature along the lower Stikine River by geologists surveying west-central British Columbia. Cairn sites occurred on both sides of the river but were most prominently mentioned at Geology Ridge and Pereleshin Mountain where more than 20 cairns were seen. According to a recent study, these structures were probably built around 500 AD as boundary markers between cultural groups. The U.S. Forest Service has reported archaeological evidence that Thomas Bay was a traditional hunting and trapping area of the Stikine Tlingit of the Taalkweidí clan who inhabited a year-round village located at the mouth of the bay and at least one additional camp in the bay prior to European contact. The first Europeans to explore this area were probably on Russian and British vessels engaged in the maritime fur trade in the late 1700s. In 1793, James Johnstone, one of Captain George Vancouver‘s officers during his voyage of discovery, surveyed Frederick Sound but did not show Thomas Bay on subsequent charts. Following the Alaska Purchase of 1867, miners and fishers started arriving to exploit the new territory. In 1921, a gold lode was discovered at a feature called Elephant Head on the north arm of Thomas Bay and developed by Colp & Lee of Petersburg. Another gold vein was found in the southeast arm of Thomas Bay south of Spray Island. In 1915, the first documented beam trawl shrimp fishery in Southeast Alaska occurred in Thomas Bay, Floating canneries located in the bay processed this catch, and by 1921, five processors were operating. Fleet size, production capacity, and expansion of fishing grounds occurred well into the 1950s. Prior to 1959, the beam trawl fishery in Southeast Alaska was the major shrimp fishery in the state.

Baird Glacier drains the west side of the Stikine Icefield and flows from an elevation of over 6,000 feet (1829 m) to a proglacial lake filled with icebergs that calved from the ice front, now at an elevation of about 33 feet (10 m). The lake is drained by a stream that flows for about 2 miles (3.2 km) through a large outwash plain connected to the head of Thomas Bay. The Witches Cauldron is a basin filled with a glacier that flows from the south and merges with the Baird Glacier at about 8.5 miles (14 km). The Oasis Glacier flows from the north and merges at about 16 miles (26 km), and the North Baird Glacier flows from the north and merges at about 22 miles (35 km). The terminal moraine of the Baird Glacier is a prominent, long mound of cobble, boulders, and sand left behind when the glacier terminus was grounded for many years. Decades of sand and gravel deposition from a relatively stable glacial terminus, as well as post-glacial rebound, formed an extensive outwash plain of sand, gravel, and boulders in front of the terminal moraine. This dynamic landscape receives periodic flooding, contained mainly in the carved-out water channels of the outwash plain, due to outburst floods draining supraglacial lakes at higher elevations. The Baird Glacier down-wasted substantially between 1948 and 2000 and presently impounds large volumes of water in the Witches Cauldron where the tributary glacier experienced an ice flow reversal of 6 miles (9.5 km). It is likely that glacial outburst floods, also known as jökulhlaups, have occurred from a lake at the head of this tributary based on observations of stranded icebergs in satellite imagery. If Baird Glacier continues to down-waste, which is the most likely scenario, glacier-dammed lakes in the Witches Cauldron and other tributaries will grow in size and number resulting in an increased frequency of glacial outburst floods that in turn will destabilize the glacier terminus at the outwash plain. Abandonment of the outwash plain will trigger a catastrophic retreat because Baird Glacier is probably grounded well below sea level. The retreat of the Baird Glacier is now joining the rest of the Stikine Icefield glaciers already in retreat, such as the Sawyer Glacier, Patterson Glacier, and Great Glacier. Read more here and here. Explore more of Baird Glacier and Thomas Bay here:

About the background graphic

This ‘warming stripe’ graphic is a visual representation of the change in global temperature from 1850 (top) to 2021 (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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