Brooks Range Explained

Brooks Range
Country Type:Countries
Subdivision2 Type:States/Provinces
Length Mi:700
Length Orientation:East-west
Width Mi:150
Width Orientation:North-south
Highest:Mount Isto
Elevation Ft:8976
Range Coordinates:68.2°N -167°W
Coordinates:69.2025°N -143.8022°W
Age:Cretaceous
Orogeny:Laramide

The Brooks Range (Gwich'in: Gwazhał[1]) is a mountain range in far northern North America stretching some from west to east across northern Alaska into Canada's Yukon Territory. Reaching a peak elevation of on Mount Isto, the range is believed to be approximately 126 million years old.

In the United States, these mountains are considered a subrange of the Rocky Mountains, whereas in Canada they are considered separate, as the northern border of the Rocky Mountains is considered to be the Liard River far to the south in the province of British Columbia.[2] [3]

While the range is mostly uninhabited, the Dalton Highway and Trans-Alaska Pipeline System run through the Atigun Pass (1,415 m, 4,643 ft) on their way to the oil fields at Prudhoe Bay on Alaska's North Slope. The Alaska Native villages of Anaktuvuk and Arctic Village, as well as the very small communities of Coldfoot, Wiseman, Bettles, and Chandalar, are the range's only settlements. In the far west, near the Wulik River in the De Long Mountains is the Red Dog mine, the largest zinc mine in the world.

The range was named by the United States Board on Geographic Names in 1925 after Alfred Hulse Brooks, chief USGS geologist for Alaska from 1903 to 1924.

Various historical records also referred to the range as the Arctic Mountains, Hooper Mountains, Meade Mountains and Meade River Mountains. The Canadian portion of the range is officially called the British Mountains.[4] Ivvavik National Park is located in Canada's British Mountains.

Peaks

History

Bob Marshall explored the North Fork Koyukuk River area of the range in 1929. He named Mount Doonerak, explaining "the name Doonerak I took from an Eskimo word which means a spirit or, as they would translate it, a devil." Marshall described the mountain as, a "towering, black, unscalable-looking giant, the highest peak in this section of the Brooks Range."[5]

Ecology

The Brooks Range forms the northernmost drainage divide in North America, separating streams flowing into the Arctic Ocean and the North Pacific. The range roughly delineates the summer position of the Arctic front. It represents the northern extent of the tree line, with little beyond isolated balsam poplar stands occurring north of the continental drainage divide. Trembling aspen and white spruce also occur north of the Brooks Range, though they are limited to sites that have been disturbed by human activity.[6] [7] Southern slopes have some cover of black spruce, Picea mariana, marking the northern limit of those trees.[8] As the global mean temperature increases, tree line has been observed to move further north, changing the boundaries of where these trees are found.[9] An increase in shrub abundance is also being experienced in areas which were previously dominated by tundra, impacting the ecology of the area.[10] [11]

As one of the most remote and least-disturbed wildernesses of North America, the mountains are home to Dall sheep, grizzly bears, black bear, gray wolf, moose and porcupine caribou.

In Alaska, the Western Arctic Caribou herd (490,000 strong in 2004) traverses the Brooks Range in its annual migration. The smaller Central Arctic herd (32,000 in 2002), as well as the 123,000 animal Porcupine Caribou herd, likewise migrate through the Brooks range on their annual journeys in and out of the Arctic National Wildlife Refuge. The migration path of the Porcupine Caribou herd is the longest of any terrestrial mammal on earth.[12] [13]

Paleontology

Because the rocks of the range were formed in an ancient seabed, the Brooks Range contains fossils of marine organisms. In addition to the coral fossils shown, trilobites and brachiopods from the middle Cambrian have been found in the sandy limestones of the Central Brooks Range.[14]

During the middle of the Cretaceous, the Brooks Range thrust belt underwent significant regional extension.[15]

Remains of a woolly mammoth that died about 17,100 years ago were found north of the Brooks Range. A research report on its movement range was published in 2021.[16]

Climate

While other Alaskan ranges to the south and closer to the coast can receive 250inches to 500inches of snow, the average snow precipitation on the Brooks Range is reported at 30inches[17] to 51inches.[18] Due to a changing climate, between the years 1969–2018 the Eastern and Western portions of the Brooks Range have experienced a 17.2% increase in annual precipitation.[19]

As measured at the Anaktuvuk Pass weather station (elevation 770m (2,530feet)), the average summer temperatures are 16°C as a high and 3°C as a low. During the winter the average high is -22°C while the average low is -30°C.[18] Polar amplification is a force experienced in this region as global temperatures are rising. The northern and western regions of Alaska, where the Brooks Range lies, is experiencing a warming rate twice that of southeastern Alaska. The Brooks Range has experienced an increase in average summer temperature between 4.2 °F and 5.8 °F between the years 1969–2018.[19]

In certain areas of the Brooks Range, year round snow cover or "perennial snowfields", can be found. In 1985, 34 square miles of snowfields were recorded, where as that number has dropped to under four square miles in 2017.

Films

See also

Further reading

Notes and References

  1. Web site: GNIS Account Login. geonames.usgs.gov. 23 April 2018.
  2. https://books.google.com/books?id=Ygo1AAAAMAAJ&q=%22Columbia+Mountains%22+and+%22Brooks+range%22 The Encyclopedia Americana
  3. Safire, William. The New York Times guide to essential knowledge: a desk reference for the curious mind, page 623 (Macmillan 2007).
  4. Web site: Download Geographical Names Data. 2011-06-02. www.nrcan.gc.ca. 23 April 2018.
  5. Book: Marshall . Robert . Marshall . George . Arctic Wilderness . 1956 . University of California Press . Berkeley . 22.
  6. Ackerman. Daniel. Breen. Amy. 2016-06-06. Infrastructure Development Accelerates Range Expansion of Trembling Aspen (Populus tremuloides, Salicaceae) into the Arctic. Arctic. en. 69. 2. 130–136. 10.14430/arctic4560. 1923-1245. free.
  7. Elsner. Wendy K.. Jorgenson. Janet C.. 2009-09-11. White Spruce Seedling (Picea glauca) Discovered North of the Brooks Range Along Alaska's Dalton Highway. Arctic. en. 62. 3. 342–344. 10.14430/arctic155. 1923-1245. 2016-06-13. https://web.archive.org/web/20171015202403/http://arctic.journalhosting.ucalgary.ca/arctic/index.php/arctic/article/view/155. 2017-10-15. dead. free.
  8. C. Michael Hogan, Black Spruce: Picea mariana, GlobalTwitcher.com, ed. Nicklas Stromberg, November, 2008
  9. Larsen, J.N., O.A. Anisimov, A. Constable, A.B. Hollowed, N. Maynard, P. Prestrud, T.D. Prowse, and J.M.R. Stone, 2014: Polar regions. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Barros, V.R., C.B. Field, D.J. Dokken, M.D. Mastrandrea, K.J. Mach, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L.White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1567-1612. https://www.ipcc.ch/site/assets/uploads/2018/02/WGIIAR5-Chap28_FINAL.pdf
  10. Anisimov, O.A., D.G. Vaughan, T.V. Callaghan, C. Furgal, H. Marchant, T.D. Prowse, H. Vilhjálmsson and J.E. Walsh, 2007: Polar regions (Arctic and Antarctic). Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, 653-685. https://www.ipcc.ch/site/assets/uploads/2018/02/ar4-wg2-chapter15-1.pdf
  11. Web site: NASA Studies Details of a Greening Arctic. Ramsayer. Kate. August 6, 2017. NASA.gov.
  12. http://www.adfg.alaska.gov/static/home/library/pdfs/wildlife/porcupine_caribou_news/porcupine_caribou_news_summer_2017.pdf "Porcupine Caribou News" (PDF)
  13. Web site: Porcupine Caribou News. Summer 2017. Alaska Department of Fish and Game.
  14. J.T. Dutro et al, November 1984, "Middle Cambrian Fossils from the Doonerak Anticlinorium, Central Brooks Range, Alaska", Journal of Paleontology Vol. 58 No. 6, pages 1364-1371
  15. Miller . Elizabeth L. . Hudson . Travis L. . August 1991 . Mid-Cretaceous extensional fragmentation of a Jurassic-Early Cretaceous Compressional Orogen, Alaska . . en . 10 . 4 . 781–796 . 10.1029/91TC00044 . 30 September 2023.
  16. https://www.theguardian.com/science/2021/aug/12/woolly-mammoth-walked-far-enough-circle-earth-twice-study Woolly mammoth walked far enough to circle Earth twice, study finds
  17. Book: Shulski. Martha. Wendler. Gerd. The Climate of Alaska. 16 December 2012. 2007-12-15. University of Alaska Press. 9781602230071. 148–.
  18. Book: Gallant, Alisa L.. EcoRegions of Alaska. 16 December 2012. 1998-05-01. DIANE Publishing. 9780788148965. 15–.
  19. Thoman, R. & J. E. Walsh. (2019). Alaska’s changing environment: documenting Alaska’s physical and biological changes through observations. H. R. McFarland, Ed. International Arctic Research Center, University of Alaska Fairbanks.

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