“Mendenhall Glacier”的意思、由来-开放百科全书

The Juneau Icefield Research Program has monitored the outlet glaciers of the Juneau Icefield since 1942, including Mendenhall Glacier. The glacier has also retreated {{convert|1.75|mi|km}} since 1929, when Mendenhall Lake was created, and over {{convert|2.5|mi|km}} since 1500. The end of the glacier currently has a negative glacier mass balance and will continue to retreat in the foreseeable future.^[4]

Given that average yearly temperatures are currently increasing, and the outlook is for this trend to continue, it is actually possible that the glacier might experience a period of stabilization or slight advance during its retreating march. This is because increasing amounts of warm, moist air will be carried up to the head of the icefield, where colder ambient temperatures will cause it to precipitate as snow. The increased amount of snow will feed the icefield, possibly enough to offset the continually increasing melting experienced at the glacier's terminus. However, this interesting phenomenon will fade away if temperatures continue to climb, since the head of the glacier will no longer have cold enough ambient temperatures to cause snow to precipitate.

Name

It was originally known as Sitaantaago ("the Glacier Behind the Town") or Aak'wtaaksit ("the Glacier ("the Glacier Behind the Little Lake"), also Latinized as Aakwtaaksit,^[5] by the Tlingit. The glacier was named Auke (Auk) Glacier by naturalist John Muir for the Tlingit Auk Kwaan (or Aak'w Kwaan) band in 1879. In 1891 it was renamed in honor of Thomas Corwin Mendenhall. It extends from the Juneau Icefield, its source, to Mendenhall Lake.

The glacier's retreat

Climate change

The glacier has recently come to the forefront of the international debate on global warming. The US Forest Service, which manages the Mendenhall Glacier, says "because glaciers are a product of climate, they respond to climate change."^[6] The Mendenhall glacier has been in retreat since the end of the Little Ice Age in the 1700s.^[7] In a joint article for the Juneau Empire Geologist Cathy Connor and Geophysicist Roman Motyka, both professors of the University of Alaska said "climatic warming coupled with ice loss through iceberg calving are the reasons the Mendenhall Glacier is retreating and shrinking."^[8] It is expected the glacier face will soon pull out of the lake. The Mendenhall receded 2.5 miles since circa 1500 due to a combination of natural and man-made climate change.

Negative consequences

The retreat of the Mendenhall Glacier and other glaciers in the area is believed by some to be a result of broader retreat and breakup of the Juneau Icefield. The Juneau Icefield is the fifth largest icefield in North America.^[9] For many populations near glacial areas these glaciers are a source of fresh drinking water. Once these glaciers are gone the people relying on this fresh water will be out of their familiar fresh water source. For example, Anchorage is the most populated city in Alaska and many people there city rely on the Eklutna glacier for their freshwater. If the recession of this glacier continues they will be out of their main source of water.^[10]^[11]

Benefits

Although there are many negative effects of the recession of the Mendenhall Glacier and glaciers in general, there are also a few positive outcomes from it as well. With the retreat of the Mendenhall Glacier, the Mendenhall Lake has formed. The lake is a result of the run-off from the glacier and is increasing in size as the glacier continues to retreat. The lake began formation in 1929 and has continued to grow since then.^[12] The lake has its own unique ecosystem and is a nursery for a variety of fish including several type of salmon, Dolly Varden char, and cutthroat trout.^[13]^[14]

Ancient forest uncovered

Recently, a new discovery has been made regarding the Mendenhall Glacier and its retreat. In 2012, tree stumps and logs with roots and bark still attached appeared from under the glacier as it has been retreating. They are being found in their original growth position, preserved by what was believed to be a protective gravel casing covering them. By uncovering these tree stumps and logs, scientists are able to uncover information on the ecosystem's past, from a pre-glacial time. Scientists observing the area are able to determine how old the trees were when they died by looking at their preserved remains. One of the scientists, Cathy Conner, was reported as finding "The most recent stumps emerging from the Mendenhall are between 1,400 and 1,200 years old. The oldest are around 2,350 years old. Some have dated around 1,870 to 2,000 years old."^[10]^[15]

Visitor Center

The United States Forest Service operates the Mendenhall Glacier Visitor Center as part of the Tongass National Forest, offering interpretive programs throughout the year for children and adults. The Mendenhall Glacier Visitor Center and surrounding area offer stunning views of a lake-terminating, calving glacier. The center is open year-round and receives close to 500,000 visitors each year, many coming by cruise ship in summer. There are two accessible entrances – an upper entrance with a ramp and a lower entrance with elevators.

This was the first U.S. Forest Service visitor center built in the nation; it was designed by Linn A. Forrest and dedicated in 1962. The building was expanded, renovated and rededicated in 1999.

The Sidtya restaurant originally served pie and coffee in the center. This section has been adapted for use as a gift shop, selling books, videos and souvenirs to glacier visitors.

Exhibits in the center cover the history of Mendenhall Glacier, showing how it covered the valley at the time when Joseph Whidbey, master of {{HMS|Discovery|1789|6}} during George Vancouver's 1791–95 expedition, explored the area in 1794. This is contrasted with current conditions today, related to climate change. The exhibits also depict the variety of wildlife in the area including mountain goats, black bears, and salmon in the nearby streams. Rangers provide interpretive information and children's nature programs, point out wildlife, and answer questions about the area.

The two small parking lots have access to several trails in the area. Photo Point Trail and the Steep Creek Trail are easy and accessible trails. Elevated boardwalks above Steep Creek provide salmon and bear viewing opportunities. Visitors can hike via the East Glacier Loop to an overlook within {{convert|1|mi|m}} of the glacier. Two routes traverse a series of wooden steps and a gradual elevation gain of {{convert|500|ft|m}} on this trail. The Trail of Time, which connects to East Glacier Loop, includes historical signs and handicapped accessibility. The {{convert|0.8|mi|m}} Nugget Falls Trail leads visitors to Nugget Falls, closer to the face of the glacier.^[16] Access to the outside area and trails is free. The West Glacier trail offers access to the glacier itself and the chance to view ice caves beneath it. This trail is located across the lake from the Visitor Center.

From May through September, a pass is required to view the exhibits and audio-visual presentations inside the center, and to use certain outside infrastructure, such as the Steep Creek trail, the Pavilion, the restrooms, and Photo Point trail. The fee is $5 per day, per person, or a Season's Pass can be purchased for $15 which is good for the pass holder and one friend. Federal Lands passes are also accepted. Kids 15 and under are free all year. This fee provides for maintenance of the facility, programs during summer, and updating exhibits in the center. Over 90% of the money collected from the fees remains on-site. There is no fee in the winter.

All other activities outside the center are free of charge, including Nugget Falls trail, the Trail of Time, and East Glacier/Nugget Creek trail. There is no fee for parking.

In addition to the busy summer season, the center hosts the Fireside Lecture series on Friday evenings, January through March. Programs cover ecological and cultural history, and events in Southeast Alaska. Inside the Visitor Center is a natural and cultural history bookstore run by Discovery Southeast, which is a non-profit organization supporting environmental education in Southeast Alaska. Trail guides, wildlife and bird guides, children's books and other materials are available here from May through September.

Gallery

See also

References

1. ^{{cite gnis|id=1406230|name=Mendenhall Glacier|accessdate=2012-07-14}}
2. ^{{cite web|last1=School of Arts & Sciences|title=Mendenhall Glacier Facts|url=http://www.uas.alaska.edu/arts_sciences/naturalsciences/envs/faculty_staff/pubs/mendenhall_glacier_facts_2010.pdf|publisher=University of Alaska Southeast|accessdate=7 August 2015}}
3. ^{{cite web|url=http://www.fs.fed.us/nepa/nepa_project_exp.php?project=37050|title=Forest Service|work=fs.fed.us}}
4. ^[https://www.nytimes.com/2013/07/23/us/alaska-looks-for-answers-in-glaciers-summer-flood-surges.html Alaska Looks for Answers in Glacier’s Summer Flood Surges] July 22, 2013 New York Times
5. ^{{cite web|url=http://noticias.terra.com.ar/sociedad/lugares-increibles-que-es-dificil-creer-que-existan,d05168ef568b5410VgnVCM20000099cceb0aRCRD.html|title=Lugares increíbles que es difícil creer que existan|work=Terra}}
6. ^{{cite web | url=http://www.foresthistory.org/aspnet/publications/region/10/mendenhall_glacIer.pdf | title=Mendenhall Glacier | publisher=USDA | accessdate=16 May 2015 | author=Tongass National Forest}}
7. ^{{cite web | url=http://www.fs.usda.gov/detail/tongass/about-forest/offices/?cid=stelprdb5401454 | title=Mendenhall Glacier & Ice Cave FAQs | publisher=United States Department of Agriculture | accessdate=16 May 2015 | author=US Forest Service}}
8. ^{{cite web | url=http://juneauempire.com/stories/010501/Com_Glacier.shtml | title=The shrinking Mendenhall Glacier | publisher=Juneau Empire | accessdate=16 May 2015 | author=Cathy Connor and Roman Motyka}}
9. ^{{cite web | url=http://www.polar-remotesensing.alaska.edu/case_glacier/area.html | title=A Case Study: Then Mendenhall Glacier | accessdate=17 October 2013}}
10. ^¹{{cite news|last=Poppick|first=Laura|title=Ancient Forest Thaws From Melting Glacial Tomb|url=http://www.livescience.com/39819-ancient-forest-thaws.html|accessdate=12 November 2013|newspaper=livescience|date=20 September 2013}}
11. ^{{cite web | url=http://www.livescience.com/17379-shrinking-glaciers-water-shortages.html | title=Shrinking Glaciers Point to Looming Water Shortages | date=December 8, 2011 | accessdate=17 October 2013 | author=Pappas, Stephanie}}
12. ^{{cite web | url=http://ece-distance.alaska.edu/arts_sciences/naturalsciences/envs/faculty_staff/pubs/motyka_2002.pdf | title=Twentieth Century Thinning of Mendenhall Glacier, Alaska, and its Relationship to Climate, Lake Calving, and Glacier Run-Off | date=March 14, 2002 | accessdate=17 October 2013 | author=Motyka, Roman}}
13. ^{{cite web | url=http://www.adfg.alaska.gov/static-sf/Region1/guides/PDFs/jnu_fishingspots.pdf | title=Haines-Skagway Sport Fishing Locations | accessdate=17 October 2013}}
14. ^{{cite web|title=Mendenhall Wetlands — State Game Refuge Fish and Wildlife|url=http://www.adfg.alaska.gov/index.cfm?adfg=mendenhallwetlands.species|website=adfg.alaska.gov|publisher=Alaska Department of Fish and Game/State of Alaska|accessdate=June 16, 2016}}
15. ^{{cite web|url=http://juneauempire.com/outdoors/2013-09-13/ancient-trees-emerge-frozen-forest-tomb#.VD7gDoSJm5f|title=Ancient trees emerge from frozen forest 'tomb'|work=Juneau Empire - Alaska's Capital City Online Newspaper}}
16. ^Nugget Falls Trail – Tongass National Forest