China’s Asejiaguo Glacier Is Retreating

Asejiaguo Glacier drains east from the China-Nepal border and is at the headwaters of the Yarlung Tsangpo, which becomes the Brahmaputra River. The Yarlung Tsangpo powers the 510 megawatt Zangmu Hydropower Station.  Gardelle et al (2013) identified this glacier as part of the West Nepal region, which experienced mass loss averaging -0.32 meter/year from 1999-2011. The changes of the Asejaguo Glacier are examined for the 1993 to 2018 period using Landsat imagery. Neckel et al (2014) examined changes in the surface elevation of the glaciers and found this region lost 0.37 m/year from 2003 to 2009.

In 1993 the glacier terminated in a small proglacial lake that is ~1 kilometer long at 4,900 m. At Point 1-2 there is limited exposed bedrock at 5,400-5,600 m, which is near the snowline; the head of the glacier is at 6,000 m.  There is a prominent medial moraine that begins at 5,300 m where the north and south tributaries join.  The greater width of the southern tributary indicates this is the large contributor. In 1994, the snowline is higher, at 5,500 m, but there is still only a small outcrop of bedrock at Point 2. By 2016 the proglacial lake has expanded to a length of over 2 km. At Point 1 and 2 there is a greatly expanded area of bedrock and the separation of a former tributary near Point 1 from the main glacier. In November 2018 there is fresh snowfall obscuring the exposed bedrock at Point 1 and 2. The retreat from 1993-2018 is 1.5 km, and the expanding proglacial lake is over 2.5 km long. The expanding bedrock areas in the 5,400-5,600 m range indicate the reason rise in snowline that has generated mass loss and ongoing retreat.

Asejiaguo Glacier in Landsat images from 1993 and 2018. The yellow arrow indicates the 2018 terminus and the red arrow the 1993 terminus location. Point 1 and 2 are areas of expanding bedrock at the elevation of 5,400-5,600 meters.
Asejiaguo Glacier in Landsat images from 1994 and 2016. The yellow arrow indicates the 2016 terminus and the red arrow the 1994 terminus location. Point 1 and 2 are areas of expanding bedrock at the elevation of 5,400-5,600 meters.
Asejiaguo Glacier, blue arrows indicate flow direction. M indicates the medial moraine; the China-Nepal border is also noted.

This article originally appeared on the American Geophysical Union blog From a Glacier’s Perspective.

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Chickamin Glacier Retreat Generates Separation and Lake Expansion

Chickamin Glacier in southeast Alaska glacier drains south from an icefield near Portland Canal and straddles the border with British Columbia. The glacier ended on an outwash plain in 1955 at an elevation of 250 meters.  Shortly thereafter a lake began to form, and by 1979 a Landsat image indicates a lake that is 1,300 meters long and a retreat of ~2.5 kilometers from 1902-1979 (Molnia, 2008). The glacier at that time was fed by a substantial tributary entering from the south ~5 km above the terminus, Through Glacier, pink arrow in the image below.

Here we examine Landsat images from 1985-2018 to identify the response to climate change.

In 1985, the glacier terminated at an elbow in the lake, where the lake both narrows temporarily and turns east, red arrow. The glacier had terminated close to this location for 30 years. The snowline is at 1,150 m, and Through glacier still connects to Chickamin Glacier.  At point 1 and 2, the area of exposed bedrock is limited. In 1994, the glacier has retreated 500 m from the elbow. Through Glacier has separated from Chickamin Glacier. The snowline in 1994 is at 1,125 m. In 2013, Through Glacier has retreated 1,600 m from Chickamin Glacier. Chickamin Glacier has retreated 2 km since 1985, and the snowline is at 1,250 m.  By 2018, Chickamin Glacier has retreated 3.5 km since 1985 at a rate of just over ~100 m/year, yellow arrow.

Chickamin Glacier, Alaska in 1985 and 2018 Landsat images indicating the 3.5 kilometer retreat and associated lake expansion. Red arrow is 1985 terminus location, yellow arrow is the 2018 terminus location, pink arrow is former junction area with Through Glacier.  The purple dots indicate the snowline. Point 1 and 2 are locations of bedrock expansion above the equilibrium line altitude. 

The terminus is currently at a point where the lake narrows, which should reduce the retreat rate. In 2018, the snowline reached 1,525 m, leaving only 10-15 percent of the glacier in the accumulation zone. The exceptionally high  snowline in 2018 was also noted at Taku Glacier. The snowline from 2014-2018 has persistently been above 1,350 m, which indicates substantial negative mass balance for the glacier that will drive continued retreat. The persistent snowline elevation above 1,250 m is indicated by the expansion of bedrock areas at Point 1 and 2 from 1985 to 2018, which both are located in what was the typical accumulation zone prior to that time.

The sustained mass balance losses follow that of Lemon Creek Glacier, which has a long-term record from 1953-2018 indicating a loss of  ~-0.5 m/year (Pelto et al. 2013).  The retreat and lake expansion has become a chorus with more than 20 coastal Alaskan glaciers having at least a 2 km lake expansion due to retreat since 1984, documented individually in previous posts at this blog.

Chickamin Glacier, Alaska in 1994 and 2013 Landsat images indicating the 3.5 kilometer retreat and associated lake expansion. Red arrow is 1985 terminus location, yellow arrow is the 2018 terminus location, pink arrow is former junction area with Through Glacier. The purple dots indicate the snowline. Point 1 and 2 are locations of bedrock expansion above the equilibrium line altitude. 
US Geological Survey map of Chickamin Glacier based on 1948 aerial photographs

This story originally appeared on the AGU blog From a Glaciers Perspective.

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North Cascade 2019 Winter Accumulation Assessment

For North Cascade glaciers the accumulation season provides a layer of snow that must last through the melt season. A thin layer sets the glaciers up for a mass balance loss, much like a bear with a limited fat layer would lose more mass than ideal during hibernation.

The 2019 winter season in the North Cascade Range, Washington has been unusual. On April 1, the retained snow-water equivalent in snowpack across the range at the six long SNOTEL sites is 0.72 meters, which is ~70 percent of average. This is the fifth lowest since 1984. The unusual part is that freezing levels were well above normal in January, in the 95 percentile at 1,532 m, then were the lowest level, 372 m of any February since the freezing level record began in 1948. March returned to above normal freezing levels.

April 1 winter accumulation at the longer term North Cascade SNOTEL stations (Fish Lake, Lyman Lake, Park Creek, Rainy Pass, Stampede Pass, and Stevens Pass).

As is typical, periods of cold weather in the regions are associated with reduced snowfall in the mountains and more snowfall at low elevations. In the Seattle metropolitan area February was the snowiest month in 50 years, 0.51 m of snow fell, but in the North Cascades snowfall in the month was well below average. From Feb. 1 to April 1, snowpack SWE at Lyman Lake, the SNOTEL site closest to a North Cascade glacier, usually increases from 0.99 m to 1.47 m. This year, SWE increased from 0.83 m to 1.01 m during this period.

The Mount Baker ski area snow measurement site has the world record for most snowfall in a season: 1,140 inches (28.96 m) during the 1998-99 snow season. The average snowfall is 633 inches (16.07 m) with snowfall this year, as of April 15, at 533 inches (13.53 m). Below is a Landsat image from April 15, 2019 indicating the snowline at ~1000 m in the Nooksack River Valley and 900-1000 m in the Baker Lake valley.

Freezing levels at Mount Baker, WA from the North American Freezing Level Tracker. February was the lowest mean freezing level since 1948.

This year, for the 36th consecutive year, the North Cascade Glacier Climate Project will be in the field measuring North Cascade glaciers. The early signs point towards a seventh consecutive negative balance year.

Mount Baker cloaked in winter snow in an April 15, 2019 Landsat image. MB=Mount Baker, MS=Mount Shuksan, NR=Nooksack River

This article was originally published on the blog From a Glacier’s Perspective.

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Nevado Ausangate Glaciers, Peru Retreat, and Lake Formation

Here we examine three Ausangate Glaciers in Peru, which descend south from the Nevado Ausangate group of peaks in the Cordillera Vilcanota. A circumnavigation trek around Nevado Ausangate is a favorite for visitors to the Machu Picchu area.

Digital Globe image of the Ausangate Glaciers. Red arrows indicate 1995 terminus location and yellow dots the 2018 terminus location.

The glaciers are just west of Laguna Sibinacocha, and drain into the Rio Vilcanota. Retreat of glaciers in the Cordillera Vilcanota has been rapid since 1975, Veettil et al (2017) noted that ~80 percent of glaciated area below 5,000 meters was lost from 1975-2015, and glacier area overall area had declined 48 percent.  Henshaw and Bookhagen (2014) observed that from 1988-2010, glacial areas in the Cordillera Vilcanota declined annually by ~ 1 percent per year.

Ausangate Glaciers in 1995 Landsat and 2018 Sentinel image. Red arrows indicate 1995 terminus location and yellow arrows the 2018 terminus location. The development of three proglacial lakes at the terminus of each glacier is evident.

In 1995 the three glaciers all terminate in incipient proglacial lakes. The terminus of #3 is debris covered. By 2000 each of the glaciers is still terminating in an expanding proglacial lake. Glacier #1 and #2 have developed to a size of ~0.1 square kilometers. Glacier #3 still shows limited lake development.

By 2018 Glacier #1 has retreated 450 m and is now separated from the lake. Glacier #2 has retreated 400 m and no longer reaches the lake. Glacier #3 is still in contact with the lake which still has debris covered stagnant ice covering a portion of the basin. This lake has an area of 0.13 square kilometers, and could reach an area of ~0.2 square kilometers depending on debris cover thickness.

The terminus of each glacier has retreated above 5,000 m since 1995. The glaciers each have extensive crevassing and maintains a snow covered accumulation zone, indicating they can survive current climate. Veettil et al (2017) noted that glacier area above 5,300 m was relative stable, for Ausangate Glaciers the area above 5,200 m is in the accumulation zone and has been relatively stable.

The formation of new lakes and the retreat from proglacial lakes has been a common occurrence in recent decades for Andean glaciers in Peru such as Manon Glacier and Soranano Glacier. The key role of glaciers to runoff is illustrated by the fact that 77 percent of lakes connected to a glacier watershed have maintained the same area or expanded, while 42 percent of lakes not connected to a glacier watershed have declined in area, according to Henshaw and Bookhagen (2014). The Ausangate Glaciers supply runoff to the Machupicchu Hydroelectric Power Plant managed by EGEMSA, which has an operating capacity of 90 megawatts. The Vilcanota River becomes the Urubamba River further downstream.

Ausangate Glaciers in a 2000 Landsat image. The development of two of the three proglacial lakes at the terminus of each glacier is evident.

This article was originally published on the American Geophysical Union blog From a Glacier’s Perspective.

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Heard Island Glacier Retreat Enables Lagoon Development

The Australian Antarctic Division (AAD) manages Heard Island and has undertaken a project documenting changes in the environment on the island. One aspect noted has been the change in glaciers. The Winston, Brown, and Stephenson glaciers have all retreated substantially since 1947 when the first good maps of their terminus are available.

Fourteen Men by Arthur Scholes (1952) documents a year spent by 14 men of the Australian National Antarctic Research Expedition that documented the particularly stormy, inclement weather of the region. Their journey to the east end of the island noted that they could not skirt past the glaciers along the coast. After crossing Stephenson Glacier they visited an old seal camp and counted 16,000 seals in the area. It is a rich area for wildlife that will benefit from the lagoon formation overall. Three species of seal commonly breed on Heard Island, southern elephant seals, Antarctic fur seal, and sub-antarctic fur seals (AAD, 2019).

Stephenson Glacier (SG), Stephenson Lagoon (SL), Winston Glacier (WG), and Winston Lagoon (WL) are seen in a 2019 Sentinel Image.

Here we examine the retreat of Stephenson Glacier and Winston Glacier from 2001-2019 and the consequent lagoon expansion. As Kiernan and McConnell observed, retreat of Stephenson Glacier had begun by 1971. The glacier had retreated a kilometer from the south coast and several hundred meters from the northern side of the spit. This retreat by 1980 caused the formation of Stephenson Lagoon.

Retreat of Stephenson Glacier and Winston Glacier from 2001 (red arrows) to 2018 (yellow arrows) seen in Landsat images.

In 2001 Stephenson Glacier has two separate termini: Doppler to the south and Stephenson to the east. There are numerous icebergs in Doppler lagoon but none in Stephenson Lagoon, indicating the retreat is underway. Winston Glacier terminates where the lagoon widens.

In 2008 the two lagoons in front of Stephenson Glacier are joined with a narrow eastern channel, the lagoons are filled with icebergs as a terminus collapse is underway. Winston Glacier has retreated into a narrower inlet from the wider Winston Lagoon.

By 2010 Stephenson Glacier had retreated from the main now singular Stephenson Lagoon and, like Winston Glacier in 2001, terminates at narrow point where the glacier enters the main lagoon.

By 2018 Stephenson Glacier has retreated from the main lagoon: The northern arm of the glacier experienced a 1.8 km retreat from 2001 to 2018 and the southern arm a 3.5 km retreat. The lagoon is free of ice for the first time in several centuries if not several millennia. The period of rapid retreat due to calving of icebergs into the lagoon is over and the retreat rate will now be slower. Winston Glacier has retreated 600 meters from 2001-2018. The overall lagoon expansion has been limited as the glacier has retreated up an inlet that is 500 m wide.

The AAD has a number of images in their gallery of Heard Island glaciers including Stephenson Glacier. The climate station at Atlas Cove indicates a 1°C temperature rise in the last 60 years. The AAD will also certainly be looking at how this new lagoon impacts the local seal and penguin communities. The population of king penguins increased sharply from the 1940’s into the 21st century, while rockhopper, gentoo, and macaroni penguin numbers declined over the same period (AAD, 2019).

The map below indicates the importance of Stephenson Lagoon and Winston Lagoon for wildlife, king penguins, and cormorants are noted by AAD. The retreat of this glacier follows the pattern of glacier retreat at other glaciers on islands in the circum-Antarctic region Cook Ice Cap, Kerguelen IslandHindle Glacier, and Neumayer Galcier, South Georgia.

A map of Heard Island. (Source: Australian Antarctic Division)

Stephenson Glacier and Winston Glacier are seen in Landsat images from 2008 and 2010. The 2001 terminus locations are indicated by red arrows and terminus locations in 2018 are indicated by yellow arrows.

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Argentina’s Retreating Turbio Glacier Creates a New Lake

Turbio Glacier is at the headwaters of Argentina’s Turbio River and flows into Lago Puelo. The glacier descends east from the Chile-Argentina border at 1,500 meters, descending into a low-slope valley at 1,300-1,000 m.

From 1986-2018 this glacier like many others nearby has retreated substantially leading to development of a new lake. Wilson et al. (2018) noted a substantial growth in the number of lakes in the Central and Patagonian Andes due to the ongoing rapid retreat. Masiokas et al. (2008) reported that significant warming and decreasing precipitation over the 1912–2002 interval in the region. Harrison et al. (2018) observed the number of glacier lake outburst floods have declined despite the increase in lakes.

Turbio Glacier retreat from 1986 to 2018 in Landsat images. Red arrow is 1986 terminus location, yellow arrow 2018 terminus location, and pink arrow glacier across the border in Chile.

In 1986 the glacier terminated at the southeast end of a buttress at the junction with another valley (red arrow in the image above). The glacier was 4.3 kilometers long and was connected to a headwall segment that extends to 1,500 m. There is no evidence of a lake at the terminus of Turbio Glacier.

Across the divide in Chile, the glacier, seen with a pink arrow in the above image, has a length of 3 km. In 1998 the retreat from 1986 has been modest and no lake has formed at Turbio. Across the border in Chile the glacier has divided into two sections.

Turbio Glacier retreat from 1998 to 2017 in Landsat images. Red arrow is 1986 terminus location, yellow arrow 2018 terminus location and pink arrow glacier across the border in Chile.

By 2017 Turbio Glacier has retreated exposing a new lake. The glacier is essentially devoid of retained snowpack, illustrating the lack of a significant accumulation zone that can sustain it. Across the border in Chile the glacier has nearly disappeared with the lower section revealing a new lake and little retained snowpack indicating it cannot survive.

By 2018 Turbio Glacier has retreated 1.3 km, which is over 30 percent of its total length in 32 years. The glacier is separated from the headwall glacier, which can still shed avalanches onto the lower glacier. It is possible that with additional retreat another lake will be revealed in this valley. The substantial retreat here is comparable with that of nearby Argentina glaciers such as Pico Alto Glacier and Lago Cholila . The retreat is greater than on Tic Toc Glacier to the southwest in Chile.

Turbio Glacier in a Digital Globe image from 2013. Red arrow is 1986 terminus location, yellow arrow 2018 terminus location, blue arrows show glacier flow, and pink arrow indicates glacier across the border in Chile. The border is also indicated.

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South Georgia Island’s Novosilski Glacier Is Retreating Rapidly

Novosilski Glacier is a large tidewater outlet glacier on the west (cloudier) coast of South Georgia,  terminating in Novosilski Bay. It shares a divide with the rapidly retreating Ross and Hindle Glacier on the east coast.  

Gordon et al. (2008) observed that larger tidewater and calving outlet glaciers generally remained in relatively advanced positions from the 1950’s until the 1980s. After 1980 most glaciers receded; some of these retreats have been dramatic.

The change in glacier termini position that have been documented by Cook et al (2010) at British Antarctic Survey in a BAS retreat map identified that 212 of the peninsula’s 244 marine glaciers have retreated over the past 50 years and rates of retreat are increasing.

Pelto (2017) documented the retreat of 11 of these glaciers during the 1989-2015 period.

Here we examine Landsat images from 2001-2018 and the British Antarctic Survey GIS of the island to identify the magnitude of glacier change.

The Novosilski Glacier is seen in Landsat images from 2001 and 2018. The red arrow indicate 2001 terminus location, yellow arrow the 2018 terminus location, pink arrows the fringing grounded sections of marginal ice. The South Georgia BAS map, lower image, indicates glacier margin position and elevation contours.

In 2001 Novosilski Glacier terminated in shallow water just east of a small island that acted as a pinning point (red arrow).  By 2009 the glacier had retreated only a minor amount from this island into deeper water.

A rapid retreat ensued, and by 2016 the glacier had retreated into a narrower fjord reach. The north and south margins featured remnant ice that was based above tidewater (pink arrows). The blue arrows in the 2016 Landsat image indicate the large accumulation area feeding Novosilski.  

The Novosilski Glacier is seen in Landsat image from 2016. The red arrow indicates 2001 terminus location, yellow arrow the 2018 terminus location, pink arrows the fringing grounded sections of marginal ice, and blue arrows the glacier flow directions.

By 2018 the 2-kilometer-wide calving front had retreated 2.5 km from the 2001 position. There is little evident thinning upglacier of the terminus, and there is a significant increase in surface slope suggesting that unless calving rate increases the terminus can remain near its current position.

The snowline is below 500 meters in each of the satellite images of the glacier. This is not a particularly hospitable section of coastline and the BAS has only identified gentoo penguins having colonies in the area.

The Novosilski Glacier is seen in a Landsat image from 2009. The red arrow indicates 2001 terminus location, the yellow arrow shows the 2018 terminus location.

This article originally appeared on From a Glacier’s Perspective, a blog published by the American Geophysical Union.

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Erasmo Glacier, Chile Terminus Collapse and Aquaculture

Cerro Erasmo at 46 degrees South latitude is a short distance north of the Northern Patagonia Icefield and is host to a number of glaciers, the largest of which flows northwest from the mountain. This is referred to as Erasmo Glacier with an area of ~40 square kilometers. Meltwater from this glacier enters Cupquelan Fjord, which is host to a large aquaculture project for Atlantic salmon, producing ~18,000 tons annually. This remote location allows Cooke Aquaculture to protect its farm from environmental contamination.

Runoff from Erasmo Glacier is a key input to the fjord, while Rio Exploradores’s large inflow near the fjord mouth limits inflow from the south. Davies and Glasser (2012) mapped the area of these glaciers and noted a 7 percent decline in glacier area from 1986-2011 of Cerro Erasmo. The recent retreat of the largest glacier in the Cerro Erasmo massif indicates this area retreat rate has increased since 2011. Meier et al (2018) note a 48 percent reduction in glacier area in the Cerro Erasmo and Cerro Hudson region since 1870, with half of that occurring since 1986.

In 1987 Erasmo Glacier had a land-based terminus at the end of a 6-km-long, low-sloped valley tongue. The snowline was at 1,100 meters.  In 1998 there is thinning but limited retreat, and the snowline is at 1,250 m.

By 2013 a proglacial lake had formed and there are numerous icebergs visible in the lake (Note Digital Globe image). The snowline is at 1,200-1,250 m in 2013 at the top of the main icefall. By 2016 a large lake had formed, and the snowline is at 1,200 m again at the top of the icefall.  By 2016 the terminus has retreated 2.9 km since 1987, generating a lake of the same length.

Erasmo Glacier retreat in Landsat image from 1987 and Sentinel image from 2018. Red arrow is 1987 terminus, orange arrow 2016 terminus and yellow arrow 2018 terminus. Points A-D mark areas of expanding bedrock exposure. (Source: Digital Globe)

The snowline in 2016 was at 1,200 m at the top of the icefall. From 2016 to 2018 a further 0.9 km retreat occurred. The 3.8 km retreat from 1998 to 2018 is a rate of ~200 m/year. Thinning upglacier to the expanding ridge from Point A-D is evident. Thinning at Point C has eliminated the overflow into the distributary glacier that had existed. The collapse is ongoing as indicated by the number of icebergs in the lake in 2018. There is an increased glacier surface slope 1 km behind the 2018 glacier front, suggesting the lake will not extend passed this point.

Breakup of Erasmo Glacier terminus in Digital Globe image from 2013. Purple arrow indicates largest iceberg. (Source: Digital Globe)

The retreat is consistent with retreat documented at Reichert GlacierHornopirén Glacier, and Cordillera Lago General Carrera Glacier. The impact on inflow to Cupquelan Fjord due to glacier retreat will be increased stream runoff during the wet winter season and reduced flow during the drier summer period December-February.  The summer season is still relatively wet.

This article originally appeared on From a Glacier’s Perspective, a blog published by the American Geophysical Union. 

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Brady Glacier, Alaska Nunatak Expansion and High Snowline 2018

This post was originally published on the American Geophysical Union blog on September 24, 2018.

Brady Glacier is a large Alaskan tidewater glacier in the Glacier Bay region that is beginning a period of substantial retreat (Pelto et al. 2013). Pelto et al. (2013) noted that the end of season observed transient snowline averaged 725 m from 2003-2011, well above the 600 m that represents the equilibrium snowline elevation for the glacier to sustain its current size. In 2015, 2016 and 2018, the snowline has been at 900-1000 m. This is leading to thinning across what was much of the accumulation zone. Here we examine Landsat images from 1986 to 2018 to identify signs of this thinning.

Emergence of Nunataks at Point A, B and C at 850 m on Brady Glacier from 1986 and 2018 Landsat Images. Transient snowline on 9/21/2018 indicated by purple dots (Source: AGU).

In 1986, Point A and B have insignificant rock exposure, while C has a limited single rock nunatak.  By 2000, there is bedrock exposed west of Point A and B, with two small nunataks near C. By 2015, there is a 2 km-long bedrock ridge at Point A and a ~1 km-long bedrock ridge at Point B.  The snowline in 2015 is just above Point B and C at 900 m. In 2016, on 1 Oct. 2016, after the end of the typical melt season, the snowline is at 900 m. In 2018, the snowline on Sept. 21 is at 1000 m. At Point A the bedrock ridge is now 2300 m long and up to 300 m wide. At Point A, the ridge is 1100 m long. At Point C, a third nunatak has emerged, and the series of nunataks will soon merge into a single ridge.

The persistent high snowlines indicate the consistent accumulation zone is now above 900 m, below this point thinning will continue. The mean elevation of the glacier is at 720 m, and thinning is significant below 1000 m from 1995-2011(Johnson et al, 2013). That is far less than 50 percent the glacier is retaining snowpack, and widespread thinning will drive further retreat of the distributary glacier termini in expanding lakes, noted by Pelto et al. (2013) and a 2016 blog post. Brady Glacier abuts the adjacent Lampugh Glacier that has and will be impacted by a large landslide.

Trick Lakes: In 1986, North and South Trick Lake are proglacial lakes in contact with the glacier. By 2016, the two lakes are no longer in contact with the glacier, water levels have fallen and a third lake, East Trick Lake, has formed. The more recently developed East Trick Lake is the current proglacial Trick Lake, a large glacier river exits this lake and parallels the glacier to the main Brady Glacier terminus, going beneath the glacier for only several hundred meters.

North Deception Lake: Had a limited area in 1986 with no location more than 500 m long. By 2016, retreat has expanded the lake to a length over 2 km. The width of the glacier margin at North Deception Lake will not change in the short term, but the valley widens 2 km back from the current calving front, thus the lake may grow considerably in the future.

South Dixon Lake: This new lake does not have an official name. It did not exist in 1986, 2004, 2007 or 2010. It is nearly circular today and 400 m in diameter.

Dixon Lake: It is likely that retreat toward the main valley of Brady Glacier will lead to increased water depths at Dixon Lake, observations of the depth of this lake do not exist. Retreat from 1986 to 2016 has been 600 m.

Bearhole Lake: Is expanding up valley with glacier retreat, and there are no significant changes in the width of the valley that would suggest a significant increase in calving width could occur in the near future. Currently, the lake is 75 m deep at the calving front, and there has been a 1400 m retreat since 1986 (Capps et. al. 2013).

Spur Lake: It is likely that retreat toward the main valley of Brady Glacier will lead to increased water depths at Spur Lake. The depth has fallen as the surface level fell from 1986-2016 as the margin retreated 600 m, leaving a trimline evident in the 2016 imagery.

Oscar Lake: Has experienced rapid growth with the collapse of the terminus tongue. Depth measurements indicate much of the calving front, which has increased by an order of magnitude since 1986, is over 100 m. The tongue, as seen in a 2014 Google Earth image, will continue to collapse, and water depth should increase as well. The central narrow tongue has retreated less than 200 m since 1986, but the majority of the glacier front has retreated more than 1 km since 1986.

Abyss Lake: Continued retreat will lead to calving width expansion. The retreat from 1986 to 2016 has been 400 m. The water depth has been above 150 m at the calving front for sometime and should remain high.

Emergence of nunataks at Point A, B and C at 850 m on Brady Glacier from 2000 and 2015 Landsat Images. Transient snowline on 9/21/2018 indicated by purple dots (Source: AGU).

 

Landsat image of Brady Glacier on 9/21/2018 indicating the snowline (purple dots) and the emerging nunataks at Point A-C. Lakes noted are: A=Abyss, B=Bearhole, D=Dixon, N=North Deception, O=Oscar, Sd=South Dixon, Sp=Spur, T=Trick (Source: AGU).

 

Landsat image of Brady Glacier on 10/1/2016 indicating the snowline (purple dots) and the emerging nunataks at Point A-C (Source: AGU).

 

 

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