Posts Tagged Greenland glacier retreat

Koge Bugt Outlet Glacier, Southeast Greenland

Koge Bugt Glacier is an outlet of the Greenland Ice Sheet on the southeast Coast. The glacier empties into the bay of the same name, and has three main calving fronts. This glacier is the the sweet spot for high snowfall and hence, despite its smaller size is one of the larger outlet glaciers in terms of volume. Koge Bugt Glacier is not an oft mentioned glacier it is not as fast as Helheim or Jakobshavn, does not have as long a calving front as Humboldt Glacier. Does not calve icebergs nearly as large as Petermann Glacier. Does not penetrate into the midst of the ice sheet as far as Zachariae Ice Stream or 79 Glacier. However, according to observations of Enderlin et al (2014), Koge Bugt has the second largest volume flow for the entire ice sheet. They further note that the glacier has had the third greatest volume anomaly since 2000, that is increase in discharge. Murray et al (2010) indicate Koge Bugt had accelerated and thinned in concert with other glaciers in the region. The second image below is Figure 1 from their paper indicating the 27,000 square kilometer drainage area of Koge Bugt.

Howat and Eddy (2011) examing 210 outlet glacier in Greenland noted that 191 retreated from 2000-2010 including 89% in SE Greenland. Howat and Eddy (2011) data indicated limited retreat of Koge Bugt Glacier before 2000. From 2000 to 2010 they noted a retreat of 2300 m of outlet C, 1650 m for outlet B and 300 m for outlet A. Each of these outlets has a heavily crevassed active calving front having widths of 5000 m for A, 3500 m for B and 3500 m for C. Outlet B has calved a large iceberg, and there is a substantial rift near the calving front.

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Greenland Velocity map with Koge Bugt indicated by red arrow.
koge bugt murray
Koge Bugt Drainage area from Murray et al (2010)

koge bugt map
Danish Geologic Survey map of Koge Bugt area, outlets labelled A-C.

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Google Earth image outlet A

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Google Earth image outlet B

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Google Earth image outlet C

Below is a sequence of Landsat images from 2001-2013 of the Koge Bugt Glacier three main termini. In each case the red dots indicate the calving front, the purple arrow is at the same spot on the north side of terminus A, the yellow arrow at the same spot on the west side of terminus B and the red arrow at the same spot on the west side of terminus C. From 2001 to 2011 terminus A has retreated little on the south side, but has retreated 1.5 km on the north side. Terminus B has retreated from halfway along the island on the southwest side of the terminus to the north of this island by 2011, a retreat of 2.2 km. Terminus C has retreated beyond the north end of the Peninsula noted by the red arrow, a distance of 600 m. Given the size and velocity of Koge Bugt this is a minor retreat, that can be erased by a year with more limited calving. The melt zone in these July and August images indicates how limited the ablation zone is compared to the west side of the ice sheet, this also limits the occurrence of supraglacial lakes.

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Landsat Image 2001

koge bugt 2002
landsat Image 2002

koge bugt 2005
Landsat Image 2005

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Landsat image 2010

koge bugt 2011
Landsat image 2011

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Bussemand Gletscher Retreat East Greenland

Bussemand Gletscher in East Greenland has a mixed tidewater and land based terminus. This glacier is 50 km west of Tasiilaq and just west of Nattivit Kangertivat Fjord. In this post we compare Landsat imagery from 2000 and 2012 to determine the response of this glacier to recent climate change. Espen Olsen provided the base map below and noted that Bussemand translates to bogey man.Bussemandgletscher. The first two images below are a 2000 and 2012 Landsat image. On these two images the terminus in three locations is noted. The main tidewater terminus at the orange arrows is exposing a new island or peninsula as it retreats. Two orange arrows point to small prominence’s on the side of the inlet that the glacier almost reached in 2000 and has retreated 800 m from on the west side and 400 m on the east side by 2012. At the purple arrow a new proglacial lake has formed and the terminus retreated 400 m from 2000 to 2012. At the secondary tidewater terminus the glacier has retreated 700 m from the red arrow to the yellow arrow. There are also a series of letters A-F at the same location in each image each highlighting changes. Point A denotes the expansion of a nunatak within the ice. Point B indicates the expansion of a nunatak and the lateral moraine extending from the nunatak; Point C is where an area of bedrock at the margin of the western tidewater terminus has doubled in size. Point D was a small outcrop at the edge of the glacier and is now a developing peninsula. Point E was a narrow connection to the neighboring Apuseerseerpia Glacier that is now bedrock. Point F is a location where several new bedrock knobs have emerged at the surface of the glacier. Collectively they indicate the thinning of the glacier across its entire front and several kilometers inland of the front. bussemandgletscher 2000

bussemandgletscher 2012
Below is a closeup of the terminus the two active calving embayments are indicated with blue arrows. As these narrow and the water depth drops, calving will be reduced. However, it is not clear that there is not embayment inland of this point where the proglacial lake is developing at the purple arrow. Note the channels for example between Kitak Island and the mainland in the first image. The retreat of this glacier follows that of other glaciers in the region big and small. Mernild et al (2012) noted the widespread retreat of many small glaciers including Mittivakkat. Larger glaciers were detailed by Bjork et al (2012), for example Apuserajik and Thrym.
bussemandgletscher terminus

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Epiq Sermia retreat, Greenland

Epiq Sermia is an outlet glacier of northwest Greenland, 70 km north of Jakobshavn Glacier. Epiq Sermia discharges 2-3% of the ice volume that Jakobshavn discharges. The glacier was observed to have had a small retreat in the first half of the 20th century and a minor advance in the 1960′s. Currently it is undergoing a more rapid retreat. This outlet glacier behaves as other Greenland marine terminating outlet glaciers, thinning at the terminus induced by greater basal and surface melting, triggers thinning which reduces basal friction and allows for acceleration and retreat. The glacier and its neighbor Kangilergnata Sermia have attracted recent research Rignot et al (2010) examined melting beneath the terminus tongue of both glaciers. They found rates of submarine melting 100 times larger than surface melt rates, but comparable to rates of iceberg discharge. Rignot et al (2010-PR) identified melt along the submerged bottom of Kangilergnata and Epiq Sermia where it comes into contact with warm ocean waters, which melts the glacier bottom, thinning the ice, shifting its grounding line, increasing its flotation, which leads to retreat. Figure 1 from Rignot et al (2010) indicates that water depths at the calving front are between 200-300 m deep, not that deep for the ice thickness observed..

A comparison of a 2001 and 2011 Landsat image overlain on Google Earth imagery identifies recent changes. The image comparison indicate average retreat of 1.1 kilometers over the 10 years for Epiq Sermia and 2.5 km for Kangilergnata Sermia, the yellow line is the 2001 margin and red line the 2011 margin. Thinning of Epiq Sermia is also apparent in the retreat upglacier from the terminus with the trimline being exposed and retreat at the secondary terminus into the lake. Retreat of the Epiq Sermia and Kangilergnata Sermia mirror that of other outlet glaciers, Howat and Eddy (2011) found that from 1964-2010 64% were retreating and from 2000-2010 98% of the outlet glaciers in NW Greenland were retreating. The also noted the average retreat rate rose from 20 m/year to 125 m/year, Howat and Eddy (2011). Specific examples of Umiamako Glacier, Upernavik Glacier and Kong Oscar Glacier.

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Mittivakkat Glacier Retreat, Greenland

A paper by Mernild and others (2011) focusses on the Mittivakkat Glacier on the east coast of Greenland. The glacier is separate from the Greenland Ice Sheet and its climate response as a result more rapid and more similar to other alpine glaciers. Mernild and others (2011) observe that the glacier has retreated 1300 meters since 1931 and that it has had a considerable negative mass balance since 1995. Sebastian Mernild at the Climate, Ocean, and Sea Ice Modeling Group, Computational Physics and Methods, Los Alamos National Laboratory, Los Alamos, New Mexico has provided the pictures that document the terminus change. The field observations is completed in conjunction with Aarhus University and University of Copenhagen, both in Denmark. Notice the glacier ends just short of the coastline in 1931, but in 2006 is 1500 meters from the coastline. Mittivakkat Glacier has a mass balance record since 1995, that is reported to the World Glacier Monitoring Service. During the 1995-2010 period the glacier’s average balance has been -0.87 meters/year. The cumulative loss is -13 m, with the highest loss being in 2010 at -2.16 m. The 13 m loss in water equivalent snow-ice is equivalent to more than 14 m of ice thickness and 15% of the glaciers entire volume. The problem for the glacier is the loss of essentially all of its snow cover in four of the last ten years, this is not a recipe for long term glacier survival (Pelto, 2010). The image immediately below is a Digital Globe image from July 2005 indicating the snow covered area with six weeks left in the melt season is already limited, the glacier is in the center of the image and is the largest ice mass by far. The middle image from 2006 has areas of firn exposed indicated with blue arrows, this is not the end of the melt season yet. The lower image is from August 26 2010 and is a MODIS image catalogued by the Danish Meteorological Institute.The arrow indicates the glacier which has only 10% snow covered area, with a couple of weeks of melting left in the season. In 2010 air temperatures at Tasiilaq a few kilometers from the glacier were in the range of 1.5 C above average leading to twice the normal melt rate at the terminus, which will generate an even more rapid retreat for 2010 and 2011. The high temperatures in 2010 were not limited to this location as noted by Jason Box of Ohio State. The high melt rates were as a result not limited to the Mittivakkat Glacier as observed by the record melting reported in the Arctic Report Card. The recent large negative balances will generate ongoing retreat. Mernild observes that in 2011 the mass balance was even larger than -2.45 m An image provided by Sebastian Mernild indicates a whole in the glacier near the terminus, indicating rapid retreat in the near future.

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