Weddel Glacier Retreats from Tidewater, South Georgia Island

On By mspeltoIn south georgia glacier retreat

Weddel Glacier in 1989 and 2020 Landsat images.Red arrow marks the 1989 NW terminus, orange dots the terminus location, purple arrows locations of ice spilling over a ridge, pink arrow a tributary glacier and yellow arrow the base of an icefall.

Weddel Glacier is on the southeast coast of South Georgia Island terminating in Beaufoy Cove  just north of Gold Harbor. The change in glacier terminus position was documented by Alison Cook at British Antarctic Survey in a BAS retreat map.  In 1958 it reached within 400 m of the outlet of Beaufoy Cove.  For Weddel Glacier the retreat was rapid from 1960 to 1974 and was slow from 1992-2003.  Here we examine Landsat imagery from 1989 to 2020 to visualize and update this change.

In 1989 the glacier terminates near the tip of a peninsula, red arrow in each image. The calving front extends southeast, orange dots. At the yellow arrow the glacier fills a small side valley adjacent to the main glacier. At the purple arrows are two locations where ice spillovers a bedrock ridge.  The pink arrow indicates a low elevation tributary glacier joining the main glacier, its highest elevation is 500 m.  In 2002 there is only minor retreat between the red and yellow arrow, but thinning has led to the small extension of the main icefall being almost cutoff by bedrock. By 2015 the glacier has retreated 200-300 meters from the 1989 position and the main terminus is narrower and calving has essentially ceased. At the purple arrow this is just bedrock now, there is no glacier extension flowing down the bedrock step. At the pink arrow the tributary glacier connection has narrowed, but is still connected. The glacier connection to Beaufoy Cove is almost gone in 2015.  By 2020 the glacier has receded from the tidewater of Beaufoy Cove.  The greening of the area around the cove is also evident. The tributary on the east side at pink arrow is no longer connected to the main glacier. The ridge at the upper purple arrow is just bedrock, while the lower purple arrow marking a pass to Bertrab Glacier has narrowed and bedrock has emerged at this 500 m glacier divide.

Weddel Glacier retreat is a 400 m since 1989, which is quite limited compared to Neumayer Glacier which retreated 8.8 km from 1999-2020 or Hindle Glacier which retreated 4.4 km from 1989-2017. This retreat of glaciers on South Georgia is portrayed in NASA Earth Observatory feature.

Weddel Glacier in 2002 and 2015 Landsat images. Red arrow marks the 1989 NW terminus, orange dots the terminus location, purple arrow indicates ice spilling over a ridge, pink arrow a tributary glacier and yellow arrow the base of an icefall.

Weddel Glacier flow.

 

 

Is Harlequin Lake, Alaska the fastest Growing Glacier Lake in North America this Century?

On By mspeltoIn alaska glacier retreat

Yakutat Glacier, Alaska in 1999 and 2020 Landsat image illustrating expansion of Harlequin Lake by 40.5 km². Yellow line is the 1999 margin, orange line is the 2020 margin, and yellow dots indicate the margin of the lake shoreline. Point A indicates the 1987 terminus location, Point X and Y the 1999 terminus location. Main terminus now extends south near Point C. Northern terminus extends west from Point B.

Yakutat Glacier, Alaska has experienced a spectacular retreat in the last decade losing 45 km² from 2010-2018 (Pelto, 2018).  During the  1894-1895 Alaskan Boundary Survey Yakutat Glacier ended on a flat coastal outwash plain. A decade later the glacier had retreated from the plain and a new lake was forming, Harlequin Lake.  From 1906-1987 the glacier retreated  ~10.5  km. From 2000-2010 the terminus area thinned ~10 m/year, the glacier retreated ~1200 m losing 5.8 km² of area (Trussel et al 2013).  Here we examine Landsat imagery to quantify the retreat from 1999-2020 to identify Harlequin Lake expansion during this century.

In 1999 the glacier has a single terminus extending 4.1 km across the lake from Point Y to Point X.  Point B is under the glacier near the junction of the tributaries, while Point C is in the midst of the glacier.  A ~1.4 km retreat up to 2010 with faster retreat on the north side and an expansion of the lake along the southern margin led to a 5.7 km long main calving front, and a 4 km long southern margin. An aerial image of the glacier in 2010 indicates significant rifting, blue arrows,  that pre-conditioned the glacier for a substantial 2013 breakup.  The rifts extend through the width of the glacier and typically form when thinning has led to a glacier region reaching approximate flotation (Benn, Warren and Mottram, 2007). In 2013 the glacier has separated into two separate calving fronts. The calving front extending west from Point B is  3 km wide, and the calving front extending south from Point B is  6.5 km long. There is a large area of icebergs and ice melange in front of the terminus, yellow dots in image below, resulting from the collapse.  In 2015 the snowline is quite high at 2200 m, leaving very little of the glacier in the accumulation zone. In 2015 a large iceberg detached pink arrow, that is  ~3.7 km², indicating continued rapid calving retreat. From 2013 to 2018 the glacier retreated from Point B to Point C on the northern side  a distance of 4.6 km in five years 920 m/year. By 2018 the Peninsula extending across the lake from Point C is 2.5 km long. The terminus is resting on this and adjacent shoals across 50% of its width.   The northern terminus extending west from Point B has changed little from 2013-2018. The 2018 image compares the 2010 position (yellow dots) with 2018 (orange dots)  indicating an area of 45 km² lost in eight years, though not all of it is lake (Pelto, 2018; NASA 2018).  The comparison of 1999 to 2020 illustrates the area of lake expansion between the 1999 (yellow) terminus position, 2020 terminus position (orange) and yellow dots along the lake shoreline.  The lake area growth is 40.5 km² since 1999 with an overall area loss of ~56 km².

Landsat images from 2010 and 2018 with terminus indicated by yellow dots in both, the orange dots indicate 2010 margin on 2018 image, and pink arrows indicate icebergs. 

The ability to produce icebergs as large as in 2015 has been lost as the calving front has been restricted by the Peninsula which is now 3 km long, leaving less than a 3 km wide calving front.   The narrower calving front and reduced water depth should in the short term reduce retreat of the main terminus.  The northern terminus is at a narrow point, as it recedes further the embayment widens and the retreat should increase.

The glacier thinned at a rate of ~4 m/year from 2000-2010 indicating how far out of equilibrium the glacier has been (Trussel et al 2013). The Yakutat Glacier does not have a high accumulation zone and the recent increase in the snowline elevation and thinning of the glacier have led to a substantial shrinking of the accumulation zone and thinning of the glacier in the accumulation (Truessel et al 2013). This glacier does not have a persistent significant accumulation zone in 2015, 2016 and 2018 and 2019 cannot survive (Pelto, 2010; NASA 2018).

2010 image of the Yakutat Glacier terminus reach with blue arrows indicating rifts.

Yakutat Glacier in 2013 Landsat image.

Yakutat Glacier in 2015 Landsat image.

Nangpa La and Nup La, Mount Everest Region are snow free through December 2020

On By mspeltoIn Himalaya glacier retreat

Nangpa La (NPL) and Nup La  (NL)  in Landsat images from 10-13-2020 and 12-16-2020, CO=Cho Oyu Peak and purple dots indicate the snowline. Both passes can be crossed without traversing snow on December 16.

The winter monsoon for the Nepal Himalaya is a dry cold period with limited precipitation or new snow accumulation.  Mount Everest region glaciers are summer accumulation type glaciers with ~75% of annual precipitation occurring during the summer monsoon (Wagnon et al 2013; Baker Perry et al 2020). The summer monsoon also is the period of the highest melt rates lower on the glaciers. October has been considered the end of the melt season in the region with little precipitation early in the Post Monsoon and early winter season (October-December), averaging ~3% of the total annual precipitation (Baker Perry et al 2020).   The limited snowpack with warmer winter temperatures have led to higher snowlines during the first few months of the winter season in recent years (Pelto, 2019).  Here we use a combination of Landsat images from Oct. 13 and Dec 16. to indicate the snowline rise in the vicinity of four high passes between Nepal and China (Tibet) along with The Rolex-National Geographic Perpetual Planet Expedition real time weather data, which  for Dec. 16 indicate clear dry, low humidity conditions on Mount Everest, see image below.local weather records. The four passes are  Nangpa La (NPL)  at the glacier divide between Gyarbarg and Bohte Koshi Glacier,  Nup La (NL) at the glacier divide of Ngozumpa and Rongbuk Glacier,  Lho La (LL) on a ridge between Rongbuk and Khumbu Glacier and Pethangtse Col (PC) at the top of Barun Glacier. Nangpa La is the only pass that is gentle enough that it can be crossed without mountaineering experience and has been used as a trading route across the Himalaya. Further information at NASA Earth Observatory and paper published by Pelto et al 2021.

On October 13, 2020 the snowline is at 5700 m on the Gyarbarg Glacier and Bhote Khosi Glacier that flow north and south from Nangpa La respectively. At Nup La the snowline is at 5750 m short of the pass on the Rongbuk Glacier and Ngozumpa Glacier that flow north and south from the divide respectively.  At Lho La the snowline is at 5700 m on Rongbuk Glacier and 5500 m on Khumbu Glacier that flow north and south from the divide respectively.  At Pethangtse Col the snowline is at ~6000 m on Barun Glacier that flows south from the col.  Two months later on Dec. 16 the snowline has risen above Nangpa La, allowing for a snow free crossing, and is at ~5800 m. There is also a snow free crossing at Nup La, with the snowline above the pass at 5850 m. At Lho La the snowline is below the pass on Rongbuk Glacier at 5800 m and at ~5600 m on Khumbu Glacier. At Pethangtse Col the snowline reaches the crest at the top of Barun Glacier at over ~6100 m.  Nup La and Nangpa La remain snowfree through January 1, 2021, see below. The rise of ~100 m at each site since October 13 indicates significant ablation during the period, indicative of greater mass losses lower on these glaciers. Bocchiola et al (2020) report that on West Kangri Nup Glacier, tributary to Khumbu Glacier, in the 5400-5500 m range significant accumulation is no longer being retained through the summer monsoon. This is indicative of the ~100 m rise in summer freezing level since 1980 reported by Baker Perry et al (2020). 

In 2015, 2016, 2018 and again in 2019 high winter snowlines indicated the same process in the Mount Everest region (Pelto, 2019). On December 11. 2019 the snowline in the Everest Region was notably high, averaging 5800 m, but high passes such as Nup La and Nangpa La still had snowcover (Pelto, 2019). There had been no significant snowfall from the end of the summer monsoon in 2019 through Dec. 11, a snow storm occurred from Dec. 12-14 (Baker Perry et al 2020).  The result is an expanded ablation season that extends beyond October into December or later in the winter. The melt rates due to the limited solar radiation or sublimation are small, but are significant on many glaciers (Wagnon et al 2013). This has occurred due to increasing air temperatures since the 1980’s, with mean annual air temperatures  increasing  0.62 °C per decade over the last 49 years; the greatest warming trend is observed in winter, the smallest in summer (Yang et al., 2011).In recent years a white early winter can only be found high on the glaciers of the Khumbu Region.

The Lho La (LL) and Pethangtse Col (PC) region in Landsat images from 10-13-2020 and 12-16-2020, Lh=Lhotse Peak, EV=Everest, R=Ronguk Glacier, K=Khumbu Glacier, B=Barun Glacier and purple dots indicate the snowline.

Here we continue to document the extension of mass balance losses through the post monsoon and into the winter season, which we have also reported on for the Gangotri Glacier, India and Lhonak Glacier, Sikkim.  The question for Himalayan glaciers now is when does the ablation season end?  The answer will depend on the specific glacier, but a combination of satellite imagery and local weather records are key to answering, such as the ongoing programs noted by Baker Perry et al (2020) and Wagnon et al (2020).  The Rolex-National Geographic Perpetual Planet Expedition provides real time weather data from Everest and daily images of conditions that provide an opportunity to document the end of ablation conditions. King et al (2019) found during the 2000-2015 period mass balance losses of debris-covered and clean-ice glaciers to be substantially the same in the Mount Everest region. They observed the mass balance of 32 glaciers finding a mean mass balance of all glaciers was −0.52 m/year, increasing to -0.7 m/year for lake terminating glaciers. 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.

 

Nangpa La and Nup La in Dec. 16, 2020 (above), and January 1, 2021 (below) Landsat images indicating both are snow free, purple dots indicate snowline.

Image from Rolex-National Geographic Perpetual Planet Expedition  on Dec. 16 indicating the lack of snow accumulation to date on bare rock surfaces below 5600 m in foreground including weather conditions indicating 7% humidity.

Is San Quintin Glacier Lake the fastest expanding lake this century in South America?

On By mspeltoIn chile glacier retreat

Landsat images of San Quintin Glacier from 2001 and 2020 indicate the expansion of both Lake A and Lake B due to glacier retreat. The Lake A basin as defined by the transect at the eastern narrow point, yellow line, has a total area of 41 km2 with the lake surface area now comprising 35.1 km2.

San Quintin is the largest glacier of the Northern Patagonia Icefield (NPI) at 790 km2 in 2001, flowing ~50 km west from the ice divide in the center of the ice cap.  San Quintin Glacier terminated largely on land until 1991 (Davies and Glasser, 2012). The velocity at the terminus has increased from 1987 to 2014 as the glacier has retreated rapidly into the expanding proglacial lake (Mouginot and Rignot, 2015).  As Pelto (2016) noted 19 of the 24 main outlet glaciers of the Northern Patagonia Icefield ended in a lake in 2015, all the lake termini retreated significantly in part because of calving losses leading to lake expansion in all cases. Glasser et al (2016) observed that proglacial and ice-proximal lakes of NPI increased from 112 to 198 km2. Loriaux and Cassasa (2013) reported that the combined area of the multiple San Quintin Glacier lakes expanded the most of any NPI from 1945-2011 increasing by 18 km2. The large evident crevasses/rifts perpendicular to the front indicate the terminus tongue has been partially afloat since at least 2014  Here we examine Landsat images from 1987-2020 to illustrate the changes. NASA’s Earth Observatory has high resolution images indicating the terminus in June 2014 and April 2017

In 1987 it is a piedmont lobe with evident minimal marginal proglacial lake development beginning, with an area in Lake A of  3.2 km2 and Lake B of 2.2 km2.  The main lake, Lake A, in 2001 had expanded to an area of 14 km2, while Lake B had expanded to 6.5 km2. The main lake, Point A, had an area of 23.8 km2 in 2011 (Loriaux and Cassasa, 2013) . Lake B developing on the north side of the glacier, due to a 3500 m retreat, by 2015 had an area of 9.2 km2.  For Lake A the main terminus retreat of  2200 m from 1987-2015 and led to lake expansion to 34.3 km2. The southern terminus at Point C, has a narrow fringing lake and a retreat of 1100 meters from 1987-2015.

A narrow terminus tongue extending from the main terminus had an area of 0.6 km2 and extended to within ~1.5 km of  the Lake A western shore in March 2018.   By November 10, 2018 this narrow tongue had disintegrated.   In February 2020 the area of Lake A is 35.1 km2 and Lake B is 9.7 km2, a combined area of 44.8 km2 vs 20.5 km2 in 2001.  Gourlet et al (2015) examined the thickness across sections of the NPI, weather prevented the survey of the terminus area of San Quintin Glacier, but there results do hint that the bed is below sea level between Lake A and B basins, and they should connect. In the Landsat images of 2001 and 2015 a transect across the narrow point at the east end of Lake A indicates an area of 41 km2 if the entire main terminus tongue collapses. The ~24 km2 lake expansion at the two main terminus locations of San Quintin Glacier from 2001-2020 represent the fastest lake expansion from glacier retreat, is it the fastest overall for South America? Steffen Glacier is another example of rapid retreat and lake expansion. The retreat is much less than at HPS-12, but that is an example of fjord expansion.

Landsat images of San Quintin Glacier from 1987 and 2015 indicate the expansion of both Lake A and Lake B due to glacier retreat as well as retreat at Point C.

San Quintin in  March and November 2018 Landsat images indicating loss of narrow terminus tongue pink dots.

Blondujökull, Iceland Retreat Exposes Broad Landscape

On By mspeltoIn iceland glacier retreat

Blöndujökull in Landsat images from 2000 and 2020 illustrating terminus position, yellow line is 2020 and red line is 2000.

Blöndujökull  is an outlet glacier on the west side of Hofsjökull, Iceland. The National Land Survey of Iceland has developed a DEM application that provides a detailed view of the islands glaciers and their immediate landscape. Johannesson (1997) reported the response time for Blöndujökull  to a climate change as ~90-100 years, with significant warming beginning in 1985. Since 1995 Hofsjökull has had only two years with a positive mass balance (Aðalgeirsdóttir et al 2020).  They further report the ice cap has lost 56 m w.e. from 1890-2019 with ~50% of that loss since 1995. Belart et al (2019) reported near equilibrium conditions for 14 Icelandic glaciers from 1960-1994 and mass losses of ~-1.2 m w.e. per year from 1994-2010.The ice cap geometry leads to the maximum area being in the terminus zone.  The result is instead of a larger retreat distance of a narrow outlet terminus with a limited area loss, there is a smaller retreat distance with a large area loss (see below).  This leads to divergent flow at the terminus, which also enable better formation and preservation of glacial deposits as there is limited glacial runoff reworking. Here we examine the response of this outlet glacier using Landsat imagery from 2000-2020.

Blöndujökull in 2000 ends on a gently sloping at ~750 m and has no proglacial lake near the terminus.  The snowline is a patchwork  at ~1550 m this leads to an accumulation area ratio of  ~25%.  In 2019 the glacier has retreated exposing a proglacial lakes.  The snowline in 2019 is at 1200 m at the start of August.  A close up view of the proglacial lake using the National Land Survey of Iceland, also indicates the flow directions parallel the supraglacial streams. The image also reveals the fluted moraine on the newly deglaciated terrain. By 2020 the terminus has retreated on average ~550 m. This has exposed an area of nearly 4 km2 of deglaciated terrain.

Retreat has been the consistent response of more than 90% of  Iceland glaciers since 2000 (Iceland Glaciological Society), including the outlets of Hofsjökull, Tungnafellsjökull and Norðurjökull.  Aðalgeirsdóttir et al (2020) note that mass losses of the largest Iceland Ice Caps has tripled from the 1900-1990 period to the 1995-2019 period, which give the response time noted earlier illustrates the glaciers are still far from having adjusted to the climate of the 1990-2020 period.

Terminus of Blöndujökull in National Land Survey of Iceland orthophoto. Flow direction indicated by blue arrow, which parallel supraglacial streams and which are also diverging. Blue dots indicate the 2000 terminus position with the new proglacial lakes evident.

 

Blöndujökull in Landsat image from 2000 and 2019 illustrating snowline-purple dots.

Kvislajökull and Blöndujökull drainage basin on Hofsjökull in GLIMS. Note the expanding width of the basin from the summit to terminus.

Soler Glacier Retreat and Lake Expansion

On By mspeltoIn chile glacier melt, chile glacier retreat

Soler Glacier in 1987 and 2020 Landsat images.  Red arrow indicates 1987 terminus location, yellow arrow indicates 2020 terminus location on north side of glacier.  Yellow dots indicate margin of lake and purple arrows indicate specific locations where glacier thinning is evident.

Soler Glacier is an outlet glacier on the east side of the Northern Patagonia Icefield (NPI). The terminus response of this glacier has been slower and more limited than on most NPI glaciers.  Aniya and Fujita (1986)  reported a total retreat of 200-350 m from 1944 to 1984.  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 .  Loriaux and Casassa (2013) examined the expansion of lakes on the Northern Patagonia Ice Cap reporting that from 1945 to 2011 lake area expanded 65%, 66 km2. For Soler Glacier lake formation did not occur until the last decade and debris cover has changed little as well. Willis et al, (2012) identified thinning of ~2 m/year in the ablation zone from 1987-2011. This thinning is now leading to the development of a significant proglacial lake that is examined using Landsat images from 1987-2020.

In 1987 the glacier is still up against the Little Ice Age moraine, though it had thinned considerably resulting in retreat down the slope of this vast moraine. By 2000 a small lake had developed both on the north and south side of the main terminus with a total area of ~0.3 km2, red dots. In 2016 and 2019 this lake had expanded, with the northern arm mostly filled with ice, orange dots.  In October 2020 the lake has an area of ~1 km2 and is mostly open water. The extensive thinning of the terminus tongue continues to drive both retreat and lake expansion.  The thining is evident at Point A where bedrock knobs have emerged from the ice near the snowline.  The three purple arrows on the south side of the glacier indicate thinning as these bedrock features are increasingly distant from the glacier. The terminus has retreated 500 m in the glacier center, 2100 m on the north side and 1300 m on the south side from 1987-2020.  The terminus tongue in its lowest 1.5 km continue to thin and will collapse in the lake in the near future. The end of summer snowline has averaged 1450 m in recent years leading to continued mass loss without calving in the lake (Glasser et al 2016).

Lake development here lags that of other glacier around the NPI such as Exploradores, Nef, Steffen and San Quintin.

Soler Glacier in 2000 and 2019 Landsat images.  Red arrow indicates 1987 terminus location, yellow arrow indicates 2020 terminus location on north side of glacier.  Red dots  and orange dots indicate margin of lake.

Soler Glacier in 2016 Landsat image.  Red arrow indicates 1987 terminus location, yellow arrow indicates 2020 terminus location on north side of glacier.  

Coley Glacier and Sjögren Glacier, Antarctic Peninsula Exhibit Rapid Melt Feb. 2020

On By mspeltoIn Antarctic Glacier retreat

Coley Glacier in Landsat images from Feb. 4, 2020 and Feb. 13, 2020. Magenta dots indicate the snowline

The impact of a period of record warm weather over the Antarctic Peninsula during February 2020 was rapid development of melt features and expansion of melt area on many glaciers near the tip of the Peninsula, where the temperature records were set at Esperenza and Marambio Base. Here we examine Landsat imagery at Coley Glacier on James Ross Island and Sjögren Glacier to identify surface melt extent and surface melt feature development (see map below). Coley Glacier is 30 km west and Sjögren Glacier 120 km west of Marambio Base respectively. Xavier Fettweis, University of Liege Belgium, used the MAR climate model output forced by the Global Forecast System (GFS) to generate daily melt maps for Antarctica, for Esperanza the melt map indicates that daily melt increased to above 30 mm/day on Feb. 6, with a maximum temperature on the warmest day of 18.3 C (65 F). The impact was noted at Eagle Island Ice Cap and  Boydell Glacier where melt ponds and melt saturated snowpack quickly developed. On Eagle Island Ice Cap melt averaged 22 mm/day ffrom Feb 6-Feb 11(Xavier Fettweis, 2020).

Coley Glacier retreated ~1.5 km from 2001-2015.  On Feb. 4 snowcover extends to the terminus of the glacier, this is a thin snowpack resulting from a recent summer snow event.  The bay is also largely filled with sea ice.  Nine days late on Feb. 13 the bay is free of sea ice and the snowline has rise to 400 m, at the base or just on top of the escarpment.  The loss of snow and sea ice in just nine days is a remarkable melt rate for Antarctica. On March 7 2020 the snowline is also at 400 m and melt plumes are evident at the glacier front indicating ongoing melt conditions.

Coley Glacier in March 7, 2020 viewed in the Antarctic REMA Explorer

Sjögren Glacier retreated 10-11 km from 2001-2016. On Sjögren Glacier on Feb. 11 the snowline is at 500 m, compared to ~200 m on January 12, having shifted 8 km upglacier. The false color Landsat image, deep blue coloration below the snowline indicates the presence of meltwater at the surface. Melt plumes are evident at the glacier front, yellow arrows.  The snowline is still at 500 m on March 7, with meltwater plumes indicating that significant meltwater is still exiting the glacier. The lower 15 km of the glacier was in the ablation zone for an extended period during the Antarctic summer of 2020.

The above examples added to those at Eagle Island Ice Cap and  Boydell Glacier illustrate the extent of the melt event.

Sjögren Glacier in Landsat images above from Feb. 11, 2020 and below from March 7, 2020 viewed in the Antarctic REMA Explorer.  Yellow arrows indicated meltwater plumes and magenta dots the snowline. Contours are at 100 m intervals.

Sjögren Glacier in Feb. 11, 2020 Landsat image indicating snowline with magenta dots.  The areas with significant surface meltwater have a deep blue color.

Base map for region indicating Esperanza Base=ES, Marambio=M, James Ross Island=JRI, Coley Glacier=C, Sjogren=Sj and Eagle Island=EI

Gangotri Glacier, India Smallest Observed Accumulation Zone in 2020

On By mspeltoIn India glacier retreat4 Comments

Gangotri Glacier snowline averaging 5600 m on Oct. 16, 2020 in Landsat image, magenta dots indicate the snowline.  Yellow line is the Randolph Glacier Inventory margin. Tributaries: K=Kirti; G=Ghanohim, Su=Sumeru, M=Maiandi, S=Swachhand.

Gangotri Glacier, India is in the Bhagirathi River watershed and is the largest glacier in the Garhwal Range of the Himalaya.  Gangotri Glacier supports hydropower as its meltwater runoff passes through three hydropower plants generating 1430 Megawatts including the  Tehri Dam, Maneri Bhali I and II.  From 1968-2006 the glacier retreated 800 meters, ~20 meters/year (Bhambri et al 2011). The glacier has continued to thin and tributary inflow has declined with a tributary (Chaturangi) separating during this period .  Bhambri et al (2011) noted that recession rates have in the region have increased since 1990.  Bhattachaya et al (2016) expanded on this work noting that the velocity of Gangotri Glacier declined during 2006-2014  by 6.7% from 1993-2006, indicating a reduced volume of accumulation flowing downglacier. They also noted an increase in the rate of debris-covered area expansion on the main trunk of Gangotri Glacier from 2006-2015, indicative of an expanding ablation zone. Bhattachaya et al (2016)  report a retreat rate of 9 m/year 2006-2015, which is less than before, but the down-wasting in the same period 2006-2015 was higher than during 1968-2006.

Gangotri Glacier boundary and flow directions on Digital Globe image with GLIMS glacier outline indicated.

Gangotri Glacier is a summer accumulation glacier with the peak ablation period low on the glacier coinciding with peak snowfall high on the glacier during the summer monsoon.  In the post monsoon period of October and November precipitation is low and melt rates decline. Kundu et al (2015) noted that from Sept. 2012 to January 2013 the snowline elevation varied from 5080 m to 5174 m . This contrasts to an ELA of 4875 m reported by (Bhattachaya et al 2016) and 5100 m (Bhushan et al 2017).

On October 9, 2016  the snowline was at 4850 m on the main trunk and on the tributary Ghanohim Glacier, and 4750 m on the tributary Kirti Glacier.  By November 30th a Landsat image indicates the snowline has risen to 5400 m on the main trunk and Ghanohim, the snowline is at 5800-5900 m on the glaciers in the Swachhand tributary valley, at 5600 m on Maiandi Glacier and 5700 m on the last tributary entering from the north. A Landsat image from Dec. 9th indicate that the snowline remains approximately the same as on Nov. 30th. The substantial post monsoon snowline rise in 2016 is illustrated in this article on Gangotri Glacier.

Gangotri Glacier snowline purple dots in Landsat 11-30-16 image, red arrow is terminus.

On October 16, 2020 a warm/dry post monsoon season has led to the snowline rising rapidly on Gangorti Glacier. On Kirti the snowline is at 5500 m, on Ghanohim at 5400 m, on Sumeru at 5500 m, on the main stem 5600-5700 m, on Maiandi at 5700 m and on Swachhand at 5800 m.  The snowline is averages 5600 m the same as in 2016.  Below the snowline there is limited older firn exposed, indicating that limited snow is retained below 5400 m on Gangotri Glacier from year to year. The bare glacier ice has a lower albedo then snow increasing melt and further reducing glacier mass balance.

The accumulation area ratio is the percentage of a glacier in the accumulation zone and is typically above 50% for a glacier in equilibrium.  On Gangotri Glacier in November 30, 2016 the accumulation area ratio was 20-24%, indicating a large mass balance deficit. On October 16, 2020 the AAR of Gangotri Glacier was 23%.  More important the firn line indicates that the AAR is now consistently at ~25%. This will drive continued retreat and will accelerate the retreat. How far upglacier on Gangotri Glacier do you have to travel to reach the snowline?  On the central flow line 29-30 km along the 31-33 km length. The increase in temperature has led to a tendency for snowlines to rise in the post monsoon period and remain high into the winter season on other Himalayan glaciers such as West Rongbuk Glacier and around Mount Everest in 2019.

Central flowline for Gangotri Glacier, 32 km long, with 29.5 km in the ablation zone. Landsat image from 10-26-2020.

Mount Cayley Glacier, BC Loses 40% of Length 1985-2020

On By mspeltoIn British Columbia glacier retreat

Mount Cayley Glacier (MC) and Brandywine Glacier (B) near Callaghan Lake (CL) in 1985 and 2020 Landsat Images. Yellow arrow indicates 2020 terminus, red arrow indicates 1985 terminus location.

Mount Cayley Glacier and Brandywine Glacier drain the northeast flanks of Mount Cayley and Brandywine Mountain in the Coast Range,  25 km west of Whistler, BC.  Both glaciers drain in to Callaghan Creek, a tributary to Cheakamus Rover. Retreat of Mount Cayley Glacier has led to separation into two glaciers. Retreat of Brandywine Glacier has led to development of a proglacial lake. BC Hydro operates the 157 MW Cheakamus Generating Station with a tunnel and two penstocks carrying the water 11 kilometres from Daisy Lake Reservoir  to the Cheakamus GS. The Cheakamus River has substantial salmon populations including Pink, Coho, Steelhead and Chum. For Chum BC Hydro maintains an annual escapement and spawning survey.  The main run for Chum is in the fall from Oct. 15 to early December, with most years seeing more than 100,000 adult Chum heading upstream to spawn (Middleton et al 2019). This is a 4% survival rate from the typical salmon fry population that exceeds 2.5 million (Middleton et al 2019). Here we examine Landsat imagery to indicate the glacier change from 1985-2020.

In 1985 Mount Cayley Glacier had two branches that merged and terminated in a proglacial lake at  1520 m. The east arm flowed north from the west ridge of Brandywine Peak and the west branch drained the east side of Mount Cayley.  The west arm was 3.75  km long and the east branch 1.8 km long. Brandywine Glacier was 1.2 km long terminating at 1575 m. By 1993 the two arms of the Cayley Glacier had separated. The snowline was particularly high with less than 10% of each glacier retaining small snowpatches above 2000 m.  The end of winter in 2015 a UBC Ski trip  across this area illustrates how beatiful it is and how snowy. Depsite this snow covered look, the snowpack in 2015 was low and near the end of a warm summer the snowline was again above 2000 m. In 2017 the proglacial lake in front of Brandywine Glacier is 300 m long.  The snowline is lower at 1850 m. In 2020 Brandywine Glacier  continues to terminate in the small proglacial lake and has retreated 400 m during the 1985-2020 period. The east arm and west arm of Cayley Glacier have retreated  950 m and 1400 m respectively in this 35 year interval. In both case this is 40% of the entire length of the glacier lost. The glacier now terminates at 1720 m.

In 2020 the snowline was  1900-1950 m.  The continued limited area of the accumulation zone is driving mass balance losses and retreat.  Across this region Menounos et al (2018) identified a mass loss for glaciers in this region of ~0.5 m year from 2000-2018.  This has driven retreat of small and large glaciers such as Franklin Glacier, Bridge Glacier and Stave Glacier. In 2015 the snowline was the highest of the last 37 years in the North Cascades, WA a short distance south (Pelto, 2018).

Mount Cayley Glacier (MC) and Brandywine Glacier (B) near Callaghan Lake (CL) in 1993 and 2017 Landsat Images. Yellow arrow indicates 2020 terminus, red arrow indicates 1985 terminus location.

Mount Cayley-Powder Mountain Icecap in 2015 illustrating lack of retained snowcover in late August. Purple dots indicate snowline above Mount Cayley Glacier. MC=Mount Cayley Glacier, B=Brandywine Glacier

Canadian National Atlas map of region indicating flow direction of Mount Cayley and Brandywine Gacier.

Baqupu Glacier, China Merging Supraglacial Lakes 1998-2020

On By mspeltoIn Himalaya glacier retreat

Baqupu Glacier in Landsat images from 1998 and 2020 indicating the expansion of supraglacial lakes in the terminus zone.  Purples dots indicate the snowline in October of each year.

Baqupu Glacier is in the Poiqu River watershed in southern Tibet, China.  The Poiqu River becomes the Bhote Koshi as it crosses into Nepal before joining the Sun Koshi River. The terminus of the glacier extending from 4500-4800 m is debris covered. An icefall extends from 4800-5300 m, above which the accumulation zone extends up to 5900 m. Shrestha et al (2010) examined the risk of a glacier lake outburst flood in the Sun Koshi basin from a Lumichimi Lake further north in the Poiqu Basin.  They identified the potential for damage to the  45 MW Bhote Koshi Hydropower Plant.  A  July 2016 GLOF in the basin did in fact severely damage the Bhote Koshi Hydropower Plant. In a 2020 ICIMOD report (Bajracharya et al 2020) inventory of glacial lakes and potentially dangerous ones in the Koshi, Gandaki and Karnali Basin’s was updated. In the Sun Koshi Basin they mapped 181 lakes with an area of over 0.02 km2 with four being potentially dangerous lakes. The developing Baqupu Lake is not listed as potentially dangerous.

In 1998 Baqupu Glacier features a 0.03 km2 network of small supraglacial ponds at its surface at ~4500 m.  The snowline is near the top of the icefall at 5200 m in October.  By 2000 some evident expansion of the ponds is evident.  The snowline in October is again near the top of the icefall at 5200 m.  By 2018 there are four substantial ponds that have nearly coalesced. In 2019 the ponds have coalesced into two lakes.  The snowline is just above the icefall at 5300 m.  In 2020 the supraglacial lake system has an area of 0.24 km2.  Average area of  glacial lakes in basin is 0.12 km2 (Bajracharya et al 2020). The snowline is above the icefall at ~5400 m.  The persistent equilibrium line above the icefall during this period is reducing the flux through the icefall to the debris covered tongue.  The tongue is increasingly stagnant and the thinning will lead to continued lake expansion into what will be a proglacial lake.  This expansion is similar to that on Rongbuk Glacier, while other nearby lakes have had expanding proglacial lakes, Drogpa Nagtsang Glacier and Yanong Glacier.

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Baqupu Glacier in Landsat images from 2000 and 2018 indicating the expansion of supraglacial lakes in the terminus zone.  Purples dots indicate the snowline in October of each year.

Baqupu Glacier in Digital Globe image from 2019. A=Accumulation zone; D=Debris cover, I=Icefall, S=Supraglacial lake. 

Tungnafellsjökull, Iceland Recession and Thinning 1999-2020

On By mspeltoIn iceland glacier retreat

Tungnafellsjökull Ice Cap in 1999 and 2020 Landsat images indicating  terminus changes at three northern outlets, red arrows, and at four locations of bedrock exposure.

Tungnafellsjökull Ice Cap is a ~32km2 ice cap located between Vatnajökull and Hofsjökull.  Gunnlaugsson (2016) reported on the mass balance changes of the Tungnafellsjökull Ice Cap and found it had lost 20 of its volume and 16% of its area from 1960-2013.  The ice cap was essentially in balance from 1960-1986 and had a slight mass balance loss from 1986-1995.  Almost all of the loss has been since 1995. Belart et al (2020) report on losses from 14 smaller glacier in Iceland including Tungnafellsjökull and found signficant increase in mass loss from a near equilibrium 0.07 m/year from 1960-1994 to -1.20 m/year from 1995-2010. Here we examine the impact of the 25 years of sustained mass loss on Tungnafellsjökull using Landsat images.

In 1999 the transient snow line in August is at ~1200 m.  Point A,B and D indicate bedrock knobs amidst the ice cap and Point C a bedrock ridge that the ice cap flows over near Point C.  The three northern outlets terminate at the red arrows. From east to west they are Nordur Tungnafellsjökull, Innri Hagajökull and Fremri Hagajökull. In 2000 the transient snowline in August is again at ~1200 m. In 2014 the snowline was above 1500 m laving the ice cap without any retained snowpack from the previous winter.  The area of exposed firn encompasses 40% of the ice cap indicating the size of the accumulation zone in the several years prior to 2014. By 2016 the ice cap no longer flows over the ridge near Point C.  The transient snowline is at ~1400 m. In 2020 the transient snowline is at ~1350 m.  The bedrock knob at Point B is no longer surrounded by the ice cap. The bedrock at Point A and D have expanded.  The retreat from 1999-2020 is most significant at the three northern outlet glaciers, where Gunnlaugsson (2016)  indicated thinning was greatest. The retreat has been 200 m at Nordur Tungnafellsjökull,  600 m at Innri Hagajökull and  500 m at Fremri Hagajökull.

With an accumulation area covering approximately 40% of the ice cap, mass balance losses will continue and the ice cap will continue to retreat.  Retreat has been the consistent response of more than 90% of  Iceland glaciers since 2000 (Iceland Glaciological Society), such as at Norðurjökull.

Tungnafellsjökull Ice Cap in 2000 and 2016 Landsat images indicating  terminus changes at three northern outlets, red arrows, and at four locations of bedrock exposure.

Landsat image in August 2014 indicating the lack of retained snowcover.  The glacier surface is bare ice blue-gray and exposed firn indicated by the zone inside of the yellow dots.

Whiting River Headwater Glacier, British Columbia Separates into Four

On By mspeltoIn British Columbia glacier retreat3 Comments

Whiting River headwaters glaciers in 1984 and 2020 Landsat images.  The red arrows indicate 1984 terminus positions, yellow arrow the 2020 terminus locations, pink arrows locations of glacier detachment and purple dots the snowline.

In Northwest British Columbia on the northeast side of the Stikine Icefield the Whiting Rver drains a series of glaciers, many unnamed.  Here we are focusing on a pair of glaciers just west of Whiting Lake the headwater of Whiting River, which is on the east margin of the Landsat images from 1984-2020. Glacier mass loss in the region has been extensive leading to substantial glacier recession. Melkonian et al (2016) dentified a mass loss for glaciers for Stikine Icefield of ~0.6 m year from 2000-2013 which is driving retreat.

In 1984 the four branches of the westernmost glacier: west (W), main (M), south (S) and east (E) join together at ~900 m and the glacier flows downvalley to approximately 2 km to an elevation of 700 m.  The snowline is at 1250 m on the main branch. By 1999 the east branch has separated both from the south branch but also from the higher icefield at arrow #4. The snowline of the main branch is at 1300 m. By 2018 the west glacier has separated from the main branch at arrow #1, the south branch has also separated from the main branch near arrow #3. The four former tributaries are all separated.  The snowline in 2018 is the highest observed at 1550 m with a very limited accumulation area less than 10%, this year was a record high for the previous 70 years at nearby Taku Glacier. By 2020 the main branch has retreated 2300 m since 1984.  At arrow #2 there is a further detachment occurring from the east side accumulation are to the main branch. The eastern Whiting River Glacier has retreated 1250 m in this same period.

The retreat here is substantial in terms of the overall glacier length, and illustrates detachment as also noted for Farragut River, Alaska near the southwest corner of the Stikine Icefield. The retreat is less than that observed for the large outlet glaciers of Stikine Icefield such as South Sawyer, Dawes and Great Glacier. Whiting River is a remote and wild river that is host to six salmon species.


Whiting River headwaters glaciers in 1999 and 2018 Landsat images.  The red arrows indicate 1984 terminus positions, yellow arrow the 2020 terminus locations, pink arrows locations of glacier detachment and purple dots the snowline.