Exploradores Glacier Lake Development, Chile

On By mspeltoIn chile glacier retreat1 Comment

Exploradores Glacier  (EX) in 1987 Landsat and 2020 Sentinel image.  Points A-E are consistent locations discussed.  B=Bayo Glacier.

Exploradores Glacier is an outlet glacier at the northeast corner fo the Northern Patagonia Icefield (NPI).  Glasser et al (2016) note the recent 100 m rise in snowline elevations for the NPI, which along with landslide transport explains the large increase in debris cover since 1987 on NPI from 168 km2 to 306 km2  On  Exploradores  Glacier debris cover expanded by 5.5 km2 from 1987-2015.   Loriaux and Casassa (2013) examined the expansion of lakes on the Northern Patagonia Ice Cap. From 1945 to 2011 lake area expanded 65%, 66 km2.  Davies and Glasser (2012) noted the fastest retreat during the 1870-2011 period was from 1975-1986 for Exploradores Glacier. Here we examine the response of the glacier to climate change from 1987 to 2020.

In 1987 Exploradores Glacier has a 12 km2 terminus lobe with a couple of small proglacial pond with a total area under 0.2 km2 near Point D.  The snowline is at 1400 m near Point E.  A small lake is impounded by a lateral moraine of Bayo Glacier at Point A.   In 2000 there is now a single small pond near Point D and a small proglacial pond 0.1 km2 near Point C.  The snowline is at  1400 m near Point E. In 2016 small fringing proglacial ponds exist near Point C and D.  A substantial proglacial lake has developed at Point B with an area of ~1 km2 on the east margin of the glacier.  The impounded lake at Point A has not changed. In 2020 the proglacial ponds have expanded at Point C and D.  At Point B the proglacial lake has expanded to ~1.4 km2.  The snowline is above Point E at 1500 m. At Point A the impounded lake has drained somewhat and is now at a lower lake level.  The lake breached the lateral moraine, which had been increasing in relief from the thinning Bayo Glacier.  The snowline on January 1, in the middle of the melt season is already above Point E at 1500 m. The debris cover has extended 5 km up the middle of the glacier from the terminus.

The terminus lobe of the Exploradores Glacier is now collapsing, this is a process that has already occurred at Steffen Glacier, San Quintin Glacier and Colonia Glacier.  The terminus lobe is relatively stagnant as indicated by the minimal surface slope.  The retreat has been slow compared to adjacent Fiero Glacier. The result will be a new substantial proglacial lake.

Exploradores Glacier  (EX) in 2000 and 2016 Landsat images.  Points A-E are consistent locations discussed.  B=Bayo Glacier.

GLIMS view of the terminus indicating the 200 m contour and Point B-D in same location as on images.

 

Fiero Glacier, Chile Retreat Lago Fiero Expansion

On By mspeltoIn chile glacier melt, chile glacier retreat1 Comment

Fiero Glacier in 1987 Landsat and 2020 Sentinel images.  Red arrow indicates 1987 terminus location, yellow arrow 2020 terminus lcoation, and purple dots the snowline. Point A,B and C represent locations where bedrock has expanded.

Fiero Glacier is an outlet glacier draining the northeast quadrant of the Northern Patagonia Icefield (NPI) terminating in Lago Fiero. Loriaux and Casassa (2013) examined the expansion of lakes of the Northern Patagonia Ice Cap. From 1945 to 2011 lake area expanded 65%, 66 km2.  Davies and Glasser (2012) noted the fastest retreat during the 1870-2011 period was from 1975-1986 for Fiero Glacier.  They noted that Fiero Glacier proglacial lake had an area of 6.6 km2.  Glasser et al (2016) note the recent 100 m rise in snowline elevations for the NPI, which along with landslide transport explains the large increase in debris cover since 1987 on NPI including Fiero Galcier. Here we examine the response of the glacier to climate change from 1987 to 2020.

In 1987 the glacier terminated at a narrow point in the 4.2 km long Lago Fiero that has an area of 5.6 km2.  By 2001 the glacier had retreated 500 m and the transient snowline is at 1000 m.  At point A there is a narrow rock rib. at Point B there are isolated rock rib and knobs and at Point C the rock rib is limited.  In 2015 the lake has expanded to an area of 7.3 km2, and the debris cover has also expanded. The transient snowline is at 1200-1300 m.  In 2020 the lake has expanded to an area of 9.5 km2 and a length of 6.5 km.  The 2.3 km retreat has led to a near doubling in the area of the Lago Fiero, the retreat since 2011 is the fastest rate observed. At Point A the rock rib is now a prominent separation, at Point B and C the rock rib has become continuous much like at Point A. The snowline on January 1, 2020 is at 1200 m, midway through the melt season.  The glacier slope increases 500-1000 m from the current terminus near a surface elevation of 600 m, which could mark the expansion limit of Lago Fiero (see map below).

The retreat of this glacier is larger than that of Colonia Glacier and Pared Nord Glacier further south and Verde Glacier to the north of the NPI.  All the outlet glaciers of NPI have retreated significantly in the last 30 years most leading to expanding proglacial lakes (Loriaux and Casassa, 2913;  Pelto, 2017).

Fiero Glacier in 2001 and 2015 Landsat images.  Red arrow indicates 1987 terminus location, yellow arrow 2020 terminus lcoation, and purple dots the snowline. Point A,B and C represent locations where bedrock has expanded.

Terminus of Fiero Glacier from the Randolph Glacier Inventory in 2001 (Green) and 2011 (blue).  the 500 m, 600 m and 700 m contour are indicated.  Note the steeper slope near 600 m which likely is beyond the expansion limit of Lago Fiero. Base map from GLIMS

Sona and Meola Glacier Retreat Dhauliganga Basin, India

On By mspeltoIn India glacier retreat1 Comment

Sona Glacier (SG) and Meola Glacier (MG) in 1993 and 2019 Landsat images. Red arrow indicates 1993 terminus location of Sona Glacier and Yellow arrow the 2019 terminus location.  The orange arrow marks the 1993 downglacier limit of clean ice, below is debris covered ice.  Point A marks a small expanding rock outcrop amidst glacier. Point B marks north lateral moraine exposure of Meola Glacier.

The Dhauliganga River is in the Uttarakhand District, India and is fed by a significant number of large glaciers.  The glacier runoff is a significant contributor to streamflow for the Dhauliganga Power Station 280 MW run of river hydropower. The reservoir is only 1 km long.  Sattar et al (2019) examined glacier volume and velocity of 15 large glaciers in the basin and found a 6.9% loss in area from 1968-2016.  The velocity tends to be highest in the upper ablation zone and declines toward the debris covered terminus regions.  Here we utilize Landsat imagery from 1993-2019 to focus on two glaciers Sona and Meola Glacier that were previously joined in Survey of India map (NH-44-06).

In the map below Sona Glacier and Meola Glacier are joined near Point B. In 1993  and 1994 Sona Glacier descends a steep slope terminating at the red arrow a short distance from Meola Glacier.  At Point A the rock outcrop is minor.  At Point B the lateral moraine slope above the glacier surface is limited.  By 2016 Sona Glacier has retreated to the top of the steep slope.  The orange arrow indicates clean ice on Meola Glacier has retreated upwards. By 2019 Point A has expanded and is now a ridge separating the glacier into two terminus tongues.  Sona Glacier has retreated 1200 m from 1993-2019.  The retreat was enhanced by the steep slope that the thin terminus descended in 1993. At Point B the lateral moraine slope above the glacier surface is notably larger indicating Meola Glacier thinning. The debris cover/clean ice transition on Meola Glacier has moved 600 m upglacier.

The retreat of the Sona Glacier and expansion of debris cover indicate the expansion of ablation zones that is also seen at nearby  Khatling Glacier, Gangotri Glacier and Ratangrian Glacier.

Sona Glacier (SG) and Meola Glacier (MG) in 1994 and 2016 Landsat images. Red arrow indicates 1993 terminus location of Sona Glacier and Yellow arrow the 2019 terminus location.  The orange arrow marks the 1993 downglacier limit of clean ice, below is debris covered ice.  Point A marks a small expanding rock outcrop amidst glacier. Point B marks north lateral moraine exposure of Meola Glacier.

Map indicating Sona Glacier (SG) and Meola Glacier (MG) draining into the Dhauliganga.

Mount Everest Region Glaciers December 2019 Limited Accumulation Area

On By mspeltoIn Himalaya glacier retreat1 Comment

Mount Everest region snowline identified on Dec. 11, 2019 Landsat image (yellow dots).  Green dots indicate the terminus and pink arrows flow direction of specific glaciers: T=Trakarding, DN=Drogpa Nagtsang, M=Melung, BK=Bhote Koshi, S=Shalong, Y=Yanong, G=Gyabarg, YN=Yanong North, GY=Gyachung, J=Jiuda, R=Rongbuk, ER=East Rongbuk, I=Imja, L=Lhotse, M=Marala, K=Khumbu, N=Ngozumpa.

The winter monsoon for the Himalaya is a dry cold period with limited new snow accumulation.  The Landsat image of Dec. 11, 2019 highlights the snowline at 5500-6200 m on glaciers around Mount Everest.  This high of an elevation indicates the accumulation area of the glaciers is too small to sustain the current ablation areas. This is explored in detail below. King et al (2019) found during the 2000-2015 period Himalaya mass balance losses of debris-covered and clean-ice glaciers to be substantially the same, with mass balance loss for lake-terminating glaciers being significantly higher. The overall mean was −0.39  m/year.  Maurer et al (2019) found a doubling of the average rate of loss across the Himalaya during 2000–2016 relative to the 1975–2000 interval. King et al (2017) observed the mass balance of 32 glaciers in the Mount Everest area from 2000-2015 finding a mean mass balance of all glaciers was −0.52 m/year, increasing to -0.7 m/year for lake terminating glaciers. Brun et al (2017) identify a mean balance of -0.33 m/year for 2000-2016 in Eastern Nepal, similar to King et al (2019) and not the highest loss rate in the region. Dehecq et al (2018) examined velocity changes across High Mountain Asia from the 2000-2017 period identifying a widespread slow down in the region.  The key take away is warming temperatures lead to mass balance losses, which leads to a velocity slow down, and both will generate ongoing retreat.

For an alpine glacier to be in equilibrium requires at least 50% of its area to be in the accumulation zone, this is the accumulation area ratio (AAR).  On Dec. 11, 2019 the snowline indicates where the accumulation zone begins.  The elevation ranges from 5500 m on Melung Glacier to 6200 m East Rongbuk Jiuda and Gyabarg Glacier.  The area above the snowline, AAR, is less than 30% of the total glacier on: Trakarding, Drogpa Nagtsang, Melung, Bhote Koshi, Shalong, Yanong, Gyabarg,  Jiuda, Rongbuk, East Rongbuk, Imja, Lhotse, Marala Glacier.  Gyachung and North Yanong Glacier have an AAR between 30 and 40%. Khumbu and Ngozumpa Glacier have a high mean elevation and an AAR of close to 50%.

In 2015 and again in 2018 high winter snowlines indicated the same process in the Mount Everest region. See below the rise from Nov. 2017 to Feb. 2018 to similar elevation as seen in Dec. 2019. The high snowlines indicate an accumulation area that is too small to maintain these glaciers, which drives continued retreat, such as reported at Drogpa Nagtsang and Yanong Glaciers.

Dec. 11, 2019 snowline:

6200 m =East Rongbuk, Jiuda, and Gyabarg

6100 m = Gyachung,

5900 m= Rongbuk, Imja, Lhotse

5800 m=Trakarding, Melung, Yanong North

5700 m= Ngozumpa, Drogpa N., Yanong, Shalong, Bhute Khosi

5600 m= Marala, Khumbu

5500 m= Melung

Landsat images from Nov. 17 2017 and Feb. 10 2018 indicate a rise in the snowline, purple dots, on glaciers east of Mount Everest, indicating ablation even in winter from the terminus to the snowline. Rongbuk Glacier=R, East Rongbuk Glacier=ER Far East Rongbuk Glacier=F, Kada Glacier=K,  Barun Glacier=B,  Imja Glacier=I and Kangshung Glacier=KX.

Kerguelen Island Glacier Retreat Expands Lake District

On By mspeltoIn Kerguelen glacier retreat1 Comment

Eastern Outlet glaciers of Cook Ice Cap in a 2001 Landsat and 2019 Sentinel image indicating retreat from 2001 terminus positions (red arrows) to 2019 terminus location (yellow arrows).

The east side of the Cook Ice Cap on Kerguelen Island outlet glaciers have retreated expanding and forming a new group of lakes (Pelto, 2016).  Here we examine the changes from 2001-2019 along using Landsat and Sentinel imagery. Retreat of glacier in the region was examined by Berthier et al (2009) and is exemplified by the retreat of Ampere Glacier.  Verfaillie et al (2016) examined the surface mass balance using MODIS data, field data, and models.  The accelerating glacier wastage on Kerguelen Island was observed do be due to reduced net accumulation and resulting rise in the transient snowline since the 1970s, when a significant warming began.  This has led to nunatak expansion on the ice cap.

In 2001 the northern outlet glacier terminates in a wide portion of the proglacial lake #1.  The central outlet, #2, has two terminus locations the northern is in a proglacial lake that is 2.5 km long and the southern arm terminates on land.  The southern outlet terminates on land.  By 2011 the northern outlet has retreated into a narrow section of the proglacial lake. The center terminus has retreated with a new lake forming in front of its southern arm. The southern outlet has retreated revealing a new developing lake.  In 2014 the northern terminus has retreated from the primary proglacial lake. The central terminus is producing icebergs from both arms. The lake continues to expand at the southern outlet.  The 2019 image is from early in the melt season. The northern terminus has retreated 1100 m since 2001 and is no longer calving in a substantial lake. The central terminus has retreated with the northern and southern arm retreated 1500-1800 m, with a new lake forming in front of the southern arm.  The southern outlet glacier has retreated the most, 2100 m since 2001, leading to the formation of a new lake of the same length. Outlet glaciers of the ice cap that are not calving are also retreating indicating that the retreat has been driven by rising snowline and enhanced by calving. The central and southern outlets continue to calve and should continue retreat more rapidly than the northern outlet.

Eastern Outlet glaciers of Cook Ice Cap in a 2011 and 2014 Landsat images indicating retreat from 2001 terminus positions (red arrows) to 2019 terminus location (yellow arrows).

Digital Globe image of the Cook Ice Cap, with the main outlet, Ampere Glacier and the three glaciers examined here 1-3.

 

Stave River, BC Run of River Hydropower Changes with Glacier Retreat

On By mspeltoIn British Columbia glacier retreat1 Comment

Stave Glacier area in 1992 and 2019 Landsat images illustrating the loss of glacier area.  Red arrows indicate 1992 terminus location, yellow arrow 2019 terminus location, Point 1-3 are proglacial lake that are evolving, P=Piluk Glacier and S=Stave Glacier.

Stave River drains into Stave Lake and has a 40 km length above the lake.  The basin has a glaciated area of 32 km2. The basin above Stave Lake has two Run of River Hydropower plants (RORH) .  The 17.5 MW RORH project on the Northwest Stave River was built by Innergex Resources and was opened in 2013. The facility is 18 km upstream of Stave Lake and has 1.9 km long diversion reach. The 33 MW RORH project on the Upper Stave River was built by Innergex Resources and was opened in 2011.  Stave River has a substantial fall run of Coho and Chum.  A decline in the salmon runs beginning in 2000 led to development of a Lower Stave river water use plan to reduce blockage at the Ruskin Dam hydropower site, which is not an RORH.  This has not led to a recovery of salmon, in fact the 2008-2012 population numbers are lower than prior [Ladell and Putt, 2015].  Stave River has a peak flow in June and mean July-September runoff is 37.4 m3s-1.

RORH lack significant reservoirs by definition and as a result cannot alter the discharge of a river or store water, including glacier runoff.  RORH divert a portion of a rivers discharge through the power system, reducing discharge for the diversion reach of the power system, before returning the water to the river. Mountainous nations with substantial hydropower potential and glaciers are expanding their use of RORH [Orlove, 2009].  The growth of RORH has been due to the lower cost of development and reduced environmental impact, which result from the absence of a large storage reservoir.

Peak streamflow in the alpine regions of the Pacific Northwest occur during the spring snow melt season. Glacier runoff peaks in the mid to late summer during the height of the ablation season, coincident with minimum streamflow of late summer and early fall.  The loss of glacier area from these watersheds thus reduces streamflow primarily during late summer minimum flow periods.  This has been observed in several Pacific Northwest basins where a decline of more than 20% in glacier area has led to a decrease in glacier runoff [Stahl and Moore, 2006; Pelto, 2011].  In such basins RORH will have a reduced seasonal production capacity.

Stave Glacier, the largest glacier in the watershed, declined from 11.38 km2 in 1988 to 9.45 km2 in 2005 [Koch et al 2009] and 8.6 km2 in 2019. The terminus retreated 1900 m during the 1992-2019 period.  Piluk Glacier terminated in a proglacial lake in 1992.  By 1998 it had retreated from this lake and by 2015 a new proglacial lake was forming at Point 2. The glacier retreated 800 m from 1992 to 2019, and the area was reduced from 3.5 km2 to 2.0 km2 . The glacier lost all of its snowcover in 2015, and more than 90%in 2016 and 2019, indicating it cannot survive current climate. Point 1 indicates where a glacier terminates in a proglacial lake in 1992 at what is more of a pass than a valley.  This is still the case in 1998, but in 2015 the lake is no longer proglacial and only 20% of the 1992 glacier remains. Point 3 in 1992 is a glacier filled basin that is narrowly attached to an adjacent glacier. In 1998 the glacier still fills the basin but is no longer attached to the adjacent glacier. By 2015 the basin is mainly a proglacial lake.  In 2019 only a small section of glacier remains at the southwest edge of the lake.  There are two other glaciers between Stave Glacier and Piluk Glacier that are unnamed where red arrows indicate the 1992 terminus location.  The northern flowing of these glaciers has retreated 850 m, while the south flowing glacier retreated 400 m.  In both cases this represents more than 30% of the total glacier length.

Stave River Basin, British Columbia indicating hydropower plants and glaciers in the basin (Map created by Ben Pelto)

Future Glacier Runoff and Hydropower Implications

Recent glacier runoff is determined from a mean observed regional summer balance of -2.9 m w.e.  Summer glacier runoff is 98.6 million m3, yielding a mean summer discharge of 7.5 m3s-1, which is 20 to 24% of total stream discharge.The rate of glacier area loss was 0.53%/year from 1985-2005 [Bolch et al 2010].  A continuation of this trend up to 2050 would yield a 24% area decline, with glacierized area in the basin of approximately 26 km2 in 2050.  Since 2005 the area loss has accelerated to ~1% /year.  This would lead to an area of  22.4 km2. A greater decline is likely however, as modeled warming of 2.2 ˚C by 2050 would lead to higher ablation rates [Clarke et al 2015].  Using the temperature index model and applying the increased temperature yields a mean summer balance of -3.5 m w.e., yielding 78.4 million m3.  This is equivalent to mean summer discharge of 5.9 m3s-1, a 20% decline from present glacier runoff. in 2050. The reduced glacier runoff will add to the earlier snowmelt runoff in the region through 2050 leading to significantly reduced late summer discharge and hydropower potential in the Stave River basin. Peak glacier runoff has passed and an ongoing decline will occur as is the case at many basins in the region including the Nooksack Basin in Washington (Pelto, 2015).

Stave Glacier area in 1998 and 2015 Landsat images illustrating the loss of glacier area.  Red arrows indicate 1992 terminus location, yellow arrow 2019 terminus location, Point 1-3 are proglacial lake that are evolving, P=Piluk Glacier and S=Stave Glacier.

 

Austre Torellbreen, Svalbard Retreat and Nunatak Expansion

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Austre Torellbreen in 2000 and 2019 Landsat images.  Red arrow is the 2000 terminus location, yellow arrow the 2019 terminus location. Point 1,2 and 3 are nunatak areas that are expanding.

Austre Torellbreen is an outlet glacier on the southwest coast of Svalbard.  It is just west of calving glacier that are retreating such as Paierbreen and Samarinbreen and adjacent to the land terminating Nannbreen. Blaszczyk et al (2008) report the velocity of Austre Torellbreen near the calving front of 220-265 m/year. Nuth et al (2013) determined that the glacier area over the entire archipelago has decreased by an average of 80 km per year over the past 30 years, a 7% reduction.

In 2000 the calving front is 4.7 km wide and has a low slope at the terminus with the surface reaching 150 m 2.5 km from the calving front.  The calving front is at a point where the embayment widens upglacier and has outwash plains on either side of the margin. The snowline is at 300 m in 2000.  At Point 1 is an isolated nunatak and at Point 2 and 3 are limited ridges extending from nunataks. By 2014 the glaciers western margin has retreated into the widening embayment, with more limited retreat in the center and eastern margin of the glacier.  By 2019 the Austre Torellbreen western margin has retreated 2400 m, while the eastern margin has retreated 800 m. The terminus has narrowed to 4.2 km and is retreated from an area of low slope margins to a location between two peak Brattho and Raudfjellet. There is an area of extensive crevassing at the current calving front, suggesting that further calving retreat will occur. At Point 1 the nunatak has expanded in area and vertical relief. At Point 2 the ridge that was separated in two segments has joined into a single ridge.  At Point 3 the ridge has extended by 500 m and has a greater relief in 2019.  The nunataks and mountain ridges that are amidst and adjacent to Austre Torellbreen can be seen to emerge and expand from 2000 to 2019 as the glacier thins.  This thinning leads to the retreat that is enhanced by calving.

 

Austre Torellbreen in TopoSvalbard map from circa 2000 and in a visual image from 2014.

Austre Torllbreen in 2014 Landsat image. Red dots indicate the snowline at 350 m.

Wright Glacier, Alaska Snowline and Terminus Retreat

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Wright Glacier in 1984 and 2019 Landsat images.  The red arrow indicates 1984 terminus location, yellow arrow 2019 terminus location, pink arrow where the surface slope steepens and red dots indicate the snowline. 

Wright Glacier is the largest glacier draining an icefield just south of the Taku River and the larger Juneau Icefield. The glacier accumulation zone is mainly in British Columbia.  The glacier filled a lake basin in 1948 as illustrated by the USGS map and  NSIDC collection,  though the terminus is beginning to break up.

In 1984 the glacier ended at a peninsula in the lake where the lake turns east.  This was my view of this glacier during the summers of 1981-1984 from the Juneau Icefield with the Juneau Icefield Research Program. Our bad weather came from that direction so keeping an eye on that region during intervals between weather events was the practice. Here we examine Landsat imagery from 1984-2019 to document the retreat of Wright Glacier and the rise in elevation of the snowline.

In 1984 the lake had a length of 3.1 km extending northwest from the glacier terminus. The snowline in mid-August with a month left in the melt season was at 1150 m at a main glacier junction.  By 1993 the glacier had retreated little on the north side of the lake and 200 m on the south side. The snowline in mid-September close to the end of the melt season was at 1150 m. By 2013 the glacier had retreated 900 m and was terminating in a narrower portion of the expanding lake, 30 m/year. The snowline was again at the main junction near 1150 m. In 2018 the snowline on September 16th was at 1450 m with less than 25% of the glacier in the accumulation zone.  In 2019 on Aug. 2 the snowline was at 1500 m, likely the highest snowline in the last 70 years, as was the case at nearby Taku Glacier. The high snowlines of recent years has driven an acceleration of the retreat of 1000 m since 2013, 150+ m/year. The glacier has a steeper surface slope 2 km beyond the current terminus front indicating the lake ends either near this point, pink arrow.  This could lead to a reduction in the retreat rate, though calving has not been a major factor in retreat of this glacier.

The glacier drains the same icefield as the retreating West Speel and Speel Glacier.

Wright Glacier in 1993 and 2018 Landsat images.  The red arrow indicates 1984 terminus location, yellow arrow 2019 terminus location, pink arrow where the surface slope steepens and red dots indicate the snowline.

Wright Glacier in 2013 Landsat images and USGS Topo imagery.  The red arrow indicates 1984 terminus location, yellow arrow 2019 terminus location, pink arrow where the surface slope steepens and red dots indicate the snowline.

Kropotkina, Novaya Zemlya Retreat Opens 12 km2 Embayment 1988-2019

On By mspeltoIn Novaya Zemlya glacier retreat1 Comment

Kropotkina Glacier, Novaya Zemlya in 1988 and 2019 Landsat images. Red arrow marks the 1988 terminus location and yellow arrow the 2019 terminus location.  Point A and B mark nunataks in 1988.

Kropotkina Glacier is a tidewater glacier on the southeast coast of Novaya Zemlya that drain into Vlaseva Bay.  The glaciers terminate in the Kara Sea and has been retreating like all tidewater glaciers in Novaya Zemlya LEGOS, 2006 .  The map shown below from this project indicates the lack of an embayment in 1952, red dashed line and limited retreat from 1952-1988. Carr et al (2014) identified an average retreat rate of 52 meters/year for tidewater glaciers on Novaya Zemlya from 1992 to 2010 and 5 meters/year for land terminating glaciers.  Carr et al (2017) found that between 2000 and 2013, retreat rates were significantly higher on marine-terminating outlet glaciers than during the previous 27 years. Here we examine Landsat imagery from 1988 to 2019 to identify changes in Kropotkina Glacier.

In 1988 the southern terminus is at the red arrow indicating a peninsula on the east side of the terminus, while the northern terminus is at the margin of a proglacial lake. Point A and B are nunataks. In 1998 the southern terminus has not changed significantly.  The northern terminus has not retreated significantly, but the proglacial lake has drained. By 2015 the terminus tongue in the embayment has largely collapsed, though a tongue of ice reaches across this embayment. An area of more 7 km2 has gone from glacier ice to embayment since 1998. Point A is no longer a nunatak as marginal retreat has reached this point.  The snowline in 2015 is also higher than is typically observed extending beyond the image area and is above 800 m.

By 2019 the main embayment is free of ice, having expanded by 12 km2, as the result of terminus retreat. The terminus is now oriented north-south with a 6 km long calving front. The 2019 snowline is at 750 m.Point B remains a nunatak, but not for long with the continued high snowlines seen in 2015, 2018 and 2019. The retreat has mainly been via calving, and with an expanding calving front and reduced pinning points along the margin, the rapid retreat and area loss is not over.  How deep the water is at the calving front will determine how limited calving will be going forward.  The retreat of this glacier is substantial as has been the norm for tidewater glaciers such as Inostrantseva Glacier, Vera Glacier,  Mack and Velkena Glacier or Chernysheva Glacier, with the formation of new islands and glacier separation common place Pelto (2017)  and GlacierHub.

Kropotkina Glacier, Novaya Zemlya in 1998 and 2015 Landsat images. Red arrow marks the 1988 terminus location and yellow arrow the 2019 terminus location.  Point A and B mark nunataks in 1988.

kropots map

Map of the region from  LEGOS, 2006 with elevations indicated.

Steffen Glacier, Chile Calving Retreat Acceleration 2019

On By mspeltoIn chile glacier retreat1 Comment

Steffen Glacier in 1987 and 2019 Landsat images.  Red arrow is 1987 terminus location, green arrow 2015 terminus location, yellow arrow 2019 terminus location, orange arrow an area of expanding debris cover and the pink arrow locations indicating water level decline in proglacial lakes by the northwest and midwest secondary terminus. The terminus locations are also noted by red dots for 1987 and yellow dots for 2019.

Steffen Glacier is the south flowing glacier from the 4000 square kilometer Northern Patagonia Icefield (NPI). Several key research papers have reported on the spectacular retreat of this glacier in recent years. Here we update those results using Landsat imagery from 1987-2019 to fully illustrate the changes. Rivera et al (2007) reported that Glaciar Steffen lost 12 km2 and had an average thinning of 1.5 m in the ablation zone from 1979-2001. A JAXA EORC, 2011 report compared parts of the Glaciar Steffen terminus change from 1987 to 2010. They noted a retreat of approximately 2.1 km of the main stem and 870 m of a western terminus.  Davies and Glasser (2012) in examining changes in Patagonian glaciers that the rate of area loss of the NPI increased dramatically after 2001, and has been 9.4 km2/year.  Glasser et al (2016) report that NPI proglacial lake area expanded from 112 km2 to 198 km2 from 1987 to 2015, debris cover area expanded from 4.1% of the NPI to 7.9% during the same period. After 2003 the snowline was noted to have risen ~100 m.  Dussaillant et al (2018) determined the annual mass loss of NPI at ~-1 m/year for the 2000-2012 period, with Steffen Glacier at -1.2-1.6 m/year.

In 1987 the lake at the terminus of the glacier was 1.3 km long from north to south. There are two substantial proglacial lakes with secondary termini on the west side of the glacier, the northwest extends 4 km west from the main trunk, the midwest tongue extends 1.7 km from the main trunk. In  1999 there is little retreat on the west side of the main terminus, but the east side has retreated 700 m.  The northwest secondary terminus has changed little, but the glacier tongue is showing signs of rifting.  The midwest tongue has retreated to within 0.5 km of the main trunk.  In 2004 the west side of the main terminus has retreated 600 m from a peninsula that had buttressed the terminus.  The entire last 3 km of the terminus tongue is in the proglacial lake with no buttressing by the shore, and is poised for breakup.

By 2015 the unbuttressed portion of the terminus had been lost with a 3.4 km retreat since 1987.  The northwest tongue has collapsed a retreat of 3.8 km, while the midwest termini has retreated 1.3 km since 1987. There are four large icebergs more than 0.2 km2 in the proglacial lake. From 2015-2018 the terminus is relatively stable and extends across the entire lake and on the west side is buttressed by a small peninsula.  In 2018 there are three large icebergs more than 0.2 km2 in the proglacial lake.  In 2019 the terminus has retreated 1 km from the 2018 position with  proglacial lake areas along the lowest 2 km on both the west and east margin.  This suggests this section of the terminus is similar to the main terminus in 1987 and 1999 that was poised for further calving retreat.  The 2019 image is from early in the melt season and the proglacial lake is filled with an extensive melange and one large iceberg. The retreat from 1987-2019 of 4.4 km, ~137 m/year, is driven by the 100 m rise in the snowline, resultant thinning, which then drives calving (Glasser et al 2016). Millan et al (2019) indicate the area of tributary glacier convergence near the northwest terminus and above the glacier is 700 m thick, and that the glacier has been retreating along an area where the glacier bed is below sea level, though the terminus now is close to sea level.  Note the Digital Globe image below with the yellow arrows indicating the end of the main lake basin and potentially end of the lake, the eastern margin of the glacier is fringed by proglacial lake up to that point.  Above this point there is another basin that may or may not connect to the current lake. The high snowline elevation in 2019 that is an indicator of increased melt area has led to an expansion of debris cover as well, note orange arrows for 1987 and 2019.

Steffen Glacier in 1999 and 2004 Landsat images. The red dots indicate terminus position, orange arrow where the terminus was buttressed on the eastern shore in 1999, green arrow where the glacier is buttressed on the western shore, the pink arrow indicates the northwest secondary terminus and yellow arrow the midwest secondary terminus.

Steffen Glacier in 2015 and 2018 Landsat images.  Red arrow is 1987 terminus location, green arrow 2015 terminus location, yellow arrow 2019 terminus location, orange arrow an area of expanding debris cover and the yellow dots the margin of the northwest and midwest secondary terminus.

Digital Globe image of lower reach of Steffen Glacier. Yellow arrows indicate an area where the bed rises as indicated by the increased crevassing and steeper surface slope. Note the extent of detachment of the glacier along the eastern margin up to that point.

Shie Glacier, Bhutan-China Retreat Reduces Lake Contact

On By mspeltoIn china glacier retreat1 Comment

Shie Glacier Bhutan-China in Landsat images from 1996 and 2019.  Red arrow is the southern terminus location in 1996, yellow arrow the 2019 terminus location and red dots the margin of the eastern terminus in contact with the lake in 1996.

Shie Glacier terminates in a lake on the northern flank of the Bhutan Himalaya draining north from Kangphu Kang, in a region that is claimed by both China and Bhutan.  Here we examine 1996-2019 Landsat imagery to identify glacier change. Bajracharya et al (2014) reported a 23% loss in glacier area from 1980-2010.  This retreat led to a 20% increase in the number of glacier lakes in the region  (Che et al, 2014)

In 1996 the glacier had two prominent termini ending the lake. The eastern terminus had a 1300 m wide front in the lake and the southern terminus a 400 m wide front.  The southern are terminated 800 m up a narrow inlet.  In 2000 there was a minor retreat of less than 100 m of both terminus locations since 1996.   in 2011 both glaciers had an active calving front in the lake, with the eastern terminus, between Point A and B, reduced to 800 m of front in contact with the lake. The southern terminus between Point C and D has retreated 350-400 m since 1996.

By 2018 the southern terminus had retreated 600 m further up the inlet. In 2018 the eastern glacier front reached the lake on a front less than 100 m wide. In 2019 the eastern terminus does not reach the lake on a measurable front.  The eastern terminus has retreated 400 m on the northern margin, 350 m in the glacier center and 800 m on the southern margin. The southern terminus has retreated 700-800 m since 1996.  The reduced connection of the glacier to this lake will alter the nutrient flux to the lake.  The lake has had a consistent water level during the entire period and the terminal moraine that helps impound the lake is deeply incised.  The combination along with reduced frontal suggests the GLOF threat is low

High snowlines in recent years will continue to drive retreat here and on adjacent Theri Kang and Lugge Glacier.

2011 Digital Globe image of Shie Glacier terminus, eastern terminus between Point A and B, southern terminus between Point C and D.

Shie Glacier Bhutan-China in Landsat images from 2000 and 2018.  Red arrow is the southern terminus location in 1996, yellow arrow the 2019 terminus location and red dots the margin of the eastern terminus in contact with the lake in 1996.

Ongoing Evolution of Fleming Glacier, Antarctica

On By mspeltoIn Antarctic Glacier retreat2 Comments

Fleming Glacier in 2000 and 2019 Landsat images. The 2000 glacier front is marked by red arrows on the north and south margin and red dots along the front. The 2019 glacier front is marked by yellow arrows and yellow dots.

During the 1980’s the glaciologic community was focused on increasing our baseline information and monitoring of Antarctic ice shelves. An understanding that  ice shelves had  a critical role along with a recognition that their specific role was not well understood, resulted in planning for and then having the instrumentation in place to observe the loss of several ice shelves in the next couple of decades. The following is the story of the continuing changes of Fleming Glacier that formerly fed the Wordie Ice Shelf.

Doake and Vaughan (1991) of the British Antarctic Survey reported on the disintegration of the Wordie Ice Shelf resulting from surface crevasses or rifts extending to the bottom of the ice shelf.  The ice shelf disintegrated from an area of 1900 km2  in 1970 and to an area of 100 km2 in 2009. They observed that rift formation that led to retreat of the ice front were enhanced by  a warming trend recorded in mean annual air temperatures in Marguerite Bay.  A few years later Vaughan and Doake (1996) analyzed a 50-year meteorological record that identified significant atmospheric warming on the Antarctic Peninsula and compared that to time-series observations of areal extent of nine ice shelves on the Peninsula.  At that time the five northerly ice shelves had retreated dramatically in the past fifty years, and further south there was no clear trend.

Fleming Glacier on the Antarctic Peninsula which had fed the Wordie Ice Shelf  was observed to be thinning rapidly from 2004-2008 leading to a velocity increase (Wendt et al, 2010). This led to the production of numerous tabular icebergs from the glacier front as seen in Landsat images from 2000-2019.  Freidl et al (2018)   updated this research identifying that acceleration coincided with strong upwelling events of warm circumpolar deep water into Wordie Bay.  They observed a grounding line retreat of ∼ 6–9 km between 1996 and 2011, resulting in flotation of an additional ∼ 56 km2 of the glacier tongue.  This has been driven by thinning of ~3 m/year from 2011-2014.  A greater area of flotation will reduce buttressing and friction, which likely led to the observed speedup of ∼ 1.3 m/day between 2008 and 2011 along the glacier centerline (Freidl et al 2018) .

In 1989, image below, the Wordie Ice Shelf is still tenuously connecting several different outlet glaciers.  The tabular icebergs are elongated perpendicular to ice front. In 2000 the calving front was near the mouth of an embayment.  There is a wide zone of rifted floating ice, with the actual ice front to the south hard to define based on which rift represents full separation. There are two main feeding arms, one between Point A and B, the main Fleming Glacier and the other north of Point A, the Seller Glacier and Airy Glacier.  By 2008 the glacier had lost most of the rifted area of the floating tongue seen in 2000.  In the 2017 Landsat image the northern arm has retreated towards a series of ice rumples indicating the glacier bed is resting on bedrock rises beneath the glacier. The main Fleming Glacier lacks evident rumples suggesting a deeper bed less interrupted by bedrock rises. There remains a series of tabular icebergs beyond the ice front and a single rift inland of the glacier front.  In 2019 there are two rifts near the ice front in February indicating two substantial tabular icebergs will soon be released.  The Fleming Glacier ice front has retreated 9.5 km from 2000 to 2019, o.5 km/year. The retreat of the calving front of Airy and Seller Glacier, north of Point A, is less.  The area extent loss at the front of the three glaciers from 2000-2019 has been ~125 km2.

Freidl et al (2018)  observe that the tongue of Fleming Glacier in 2016 was grounded  between ∼ −400 and −500 m below sea level and that  3–4 km upglacier of the grounding line the bed deepens to over 1000 m below sea level 10 km upglacier of the 2016 grounding line. This would suggest the breakup of Fleming Glacier is poised to increase.  The speedup of glaciers that had fed and been buttressed by the Wordie Ice Shelf continue to experience acceleration two decades after the major part of the ice shelf disintegrated.  This is similar to the pattern seen at Larsen A and Larsen B (Scambos et al 2004). The glaciologic community has more tools and more scientists than 35 years ago to focus on ice shelves.  Our increased understanding also allows a look back at events in the past where thanks to the foresight sufficient data/imagery was gathered, for example the recent work of  Robel and Banwell (2019) .  The ongoing dynamic changes illustrate the glaciologic community was focused on the right place beginning sustained examination of these ice shelves more than 30 years ago.

Fleming Glacier and Wordie Ice Shelf in 1989 Landsat image.  Pink dots mark the approximate ice shelf front in 1989, certainly there are disintegrating tongues.  Red arrows indicate 2000 glacier front location.  Point A and B are same location as in other images. 

Fleming Glacier in a Dec. 2017 Landsat image viewed using the Antarctic REMA . Black dots indicate the approximate calving front and black arrows rifts behind the calving front.

Fleming Glacier in a Dec. 2017 Landsat image viewed using the  Antarctic REMA . Black dots indicate the approximate calving front and black arrows rifts behind the calving front.