Sheridan Glacier, Alaska Retreat Causes Rapid Lake Expansion

On July 15, 2021April 23, 2024 By mspeltoIn alaska glacier retreat

Sheridan Glacier in 2002 and 2020 Landsat images illustrating retreat of the margin and expansion of the lake. Red arrow is 2002 margin on small island, yellow arrow is 2020 terminus location just north of Sherman Glacier stream and purple dots are the snowline.

Sheridan Glacier in the Chugach Mountains of Alaska begins at 1500 m and flow southwest out of the mountains with the terminus spreading out in a lake basin on the low slope coastal plain. Sheridan Lake is a proglacial lake at the terminus that drains into the Sheridan River which 12 km later reaches tidewater. From 1950 to 2000 Sheridan Glacier experienced modest retreat, with the terminus, with a fringing proglacial Sheridan Lake persisting, followed by a terminus disintegration from2000-2016. (Shugar et al 2018). Here we examine Landsat imagery from 2002-2020 to identify the retreat and resultant lake expansion.

In 2002 the proglacial lake has an area of 3.8 km², with the terminus crossing one small island in the lake. The snowline is at 750 m. In 2013 there is a 4 km2 terminus area that has disintegrated, the terminus has retreated off of the island. The snowline is at 850 m. By 2016 the terminus has retreated north of the glacier stream from Sherman Glacier entering from the east, though much of the lake is still filled with an iceberg melange. The snowline is at 925 m. In 2020 the Sheridan Lake area has expanded to 11.2 km², representing a retreat of 7.4 km²since 2002. The snowline in 202o is at 970 m. In June 2021 there are a significant number of new icebergs indicating ongoing lake expansion during 2021. Sheridan Lake is not a large glacial lake by Alaskan standards, but is bigger than any glacial lake in most alpine regions such as the Himalaya. The ability to be so large is in large part due to the ability to develop larger basin on low sloped terrain near the coastline.

The amount of terminus retreat here is less than that at Excelsior Glacier or Yakutat Glacier, but the lake expansion rate is comparable to Excelsior Glacier.

Sheridan Glacier in 2013 and 2016 Landsat images illustrating the breakup of a large terminus region generating a melange of icebergs. Red arrow is 2002 margin on small island, yellow arrow is 2020 terminus location just north of Sherman Glacier stream and purple dots are the snowline.

June 2021 Sentinel Image indicating considerable new iceberg activity leading to ongoing lake expansion in 2021.

Paarliit Sermia, Southern Greenland Terminus Separation

On June 25, 2021April 23, 2024 By mspeltoIn Greenland glacier retreat2 Comments

Paarliit Sermia in 2000 and 2020 Landsat images. The red arrow indicates the 2000 terminus location and the yellow arrow the 2020/21 terminus location. A denotes the junction of two main glacier branches, while B,C and D indicate tributaries

Paarliit Sermia is one of the most southerly tidewater glaciers in Greenland. It is an outlet glacier of a mountain icefield and not part of the main ice sheet. Similar to other icefield outlet glaciers whether in Alaska (Dawes Glacier) or Patagonia (Upsala) retreat is leading to glacier separation. Greenland tidewater outlet glaciers in this region have experienced substantial retreat since 1990, Weidick et al (2012) and Howat and Eddy (2011). There was also an increase in sea surface temperature (Straneo et al, 2013). Moon et al (2020) noted a there is a rapid reconfiguration of the Greenland Ice Sheet Coastal margin due to retreat. The retreat of glaciers in southern Greenland is changing the physical geography and hence the physical oceanography of the fjords. Here we examine Landsat imagery from 2000-2021 to identify the changes of Paarliit Sermia.

The Greenland Topographic map indicates the terminus down fjord from tributary B, 6.5 km from the main junction of two glacier branches at Junction A. Tributary B, C and D all feed the main glacier. By 2000 the glacier has retreated beyond tributary B and C. The snowline is between 550 m and 600 m in 2000 and 2002. In 2017 the glacier has retreated beyond Tributary D, and the snowline is slightly above 600 m. The two main branches are still joined, with the terminus now just 1 km from Junction A. Former Tributary C and D no longer reach tidewater. In 2020 the two main branches have separated and Point A is no longer a junction glacier has separated into two branches, the snowline is at ~600 m. In mid-June of 2021, the snowline is already at 500 m, despite being early in summer. Paarliit Sermia has retreated 2.4 km from 2000-2021, a rate of ~200 m/year.

Nearby Kangersuneq Quingordleq Glacier retreated 2.8 km from 1999-2016. To the northeast Qaleraliq has experienced a 3.2 km retreat of its west arm and 1.2 km of its east arm from 1992 to 2012. To the northeast Tingmiarmiit Glacier’s retreat from 1999-2015 has led to complete separation of the western and northern tributary. The western tributary is the main glacier and has retreated 2.4 km and the northern tributary has retreated 2.2 km in the 16 year period. In the case of nearby Tasermiut Fjord retreat has led to the fjord losing its tidewater connection.

Paarliit Sermia in 2002 and 2017 Landsat images. The red arrow indicates the 2000 terminus location and the yellow arrow the 2020/21 terminus location. A denotes the junction of two main glacier branches, while B,C and D indicate tributaries

Paarliit Sermia in 1980’s Greenland Topographic map (from Nuna GIS) and 2021 Landsat images. In the Landsat image the red arrow indicates the 2000 terminus location and the yellow arrow the 2020/21 terminus location. On both map and image A denotes the junction of two main glacier branches, while B,C and D indicate tributaries

Dawes Glacier, Alaska Retreat Driven Separation

On June 17, 2021April 23, 2024 By mspeltoIn alaska glacier retreat1 Comment

Dawes Glacier retreat in 1985 and 2020 Landsat images. Red arrow 1985 terminus, yellow arrow 2020 terminus. Point 1-3 are tributaries joining the main glacier. The glacier is about to separate into two calving termini.

Dawes Glacier terminates at the head of Endicott Arm in the Tracy Arm-Fords Terror Wilderness of southeast Alaska. Endicott Arm is a fjord that has been extending with glacier retreat, and is now 58 km long. Dawes is a major outlet glacier of the rapidly thinning Stikine Icefield. Melkonian et al (2016) observed a rapid thinning of the Stikine Icefield of -0.57 m/year from 2000-2014. Here we compare Landsat imagery to identify changes from 1985-2020. Endicott Arm is host to a population of harbor seals that prefer hauling out on icebergs during the day supplied by Dawes Glacier (Blundell and Pendleton, 2015)

In 1985 the glacier terminated at the red arrow in each image, the tributaries at points 1,2 and 4 connected with the main glacier. Point 3 is the junction point of two tribuataries. The northern arm is 1.3 km wide and the eastern arm is 2.5 km wide. The snowline was at 1100 m. In 1987 the snowline on the glacier was at 1150 m. By 1999 the glacier had retreated 900 m since 1985 and the snowline was at 1300 m. In 2019 the tributaries at Point 1, 2 and 4 have detached from the the main glacier. At Point 3 the northern arm has declined to 0.7 km wide and the eastern arm is 1.8 km wide. In 2019 the snowline is at a record 1450-1500 m.This fragmentation of Dawes Glacier will continue, which leads to a reduced ice flux to the terminus reach. By 2020 Dawes Glacier has retreated 3.8 km since 1985, a rate of 105 m/year. The snowline is again exceptionally high at 1400-1450 m. Of equal importance the glacier terminus is separating into two individual calving termini, that could become fully separate this summer of 2021.

McNabb et al (2014) reported a thinning of 62 m/year from 1985-2013. The reduced inflow and up glacier thinning is ongoing and has driven the increased retreat rate despite a reduction in water depth at the cavling front. A key mechanism for retreat over the last century has been calving. The 2007 Hydrographic map of the area indicates water depth at the calving front still over 100 m, with a depth of 150 m 1 km down fjord of the terminus (see bottom image). The depth more recently has declined to 60 m at the calving front in 2013 (Melkonian et al 2016), yet retreat has increased driven by enhanced melting. The glacier thinning is continuing, but the retreat rate will decline as the fjord head is approached.

At the glacier front the velocity was 13 m/day in 1985, increasing to 18 m/day by 1999 and declining to 5 m/day by 2014 (Melkonian et al 2016).

This reduction will reduce calving and iceberg production. As icebergs are reduced harbor seals will be disappointed as they prefer icebergs to haul out on. The Alaska Department of Fish and Game has been monitoring harbor seals in the fjord and noting that females travel to pup on the icebergs in the spring and also utilize them for mating. ADFG attached satellite tags to harbor seals to monitor their movements beyond the breeding and puppin season finding that that adult and sub-adult seals captured in Endicott Arm spent the late summer and fall months in Stephens Passage, Frederick Sound, and Chatham Strait. How will a reduction in icebergs affect this population overall?

The retreat leading to separation is also happening at other outlets of Stikine Icefield such as Baird Glacier and Sawyer Glacier.

Dawes Glacier retreat in 1985 and 2020 Landsat images. Red arrow 1985 terminus, yellow arrow 2020 terminus and purple dots the snowline. Point 1-4 are tributaries joining the main glacier.

Dawes Glacier in June 2021 Sentinel image. Indicating the impending separation of the terminus.

Hydrograh of Endioctt Arm from 2007.

Jacobsen Glacier, BC Separation Nearly Complete

On June 10, 2021April 23, 2024 By mspeltoIn British Columbia glacier retreat, Canada glacier retreat

Jacobsen Glacier in Landsat images from 1987 and 2019. Red arrow 1987 terminus location, yellow arrow 2019 terminus location and pink dots the snowline. Point A indciates ice marginal lake in 1987, Point C is the glacier junction, Point B an emerging rock rib and Point D a nunatak.

Jacobsen Glacier is part of the Monarch Icefield of the Coastal Range of British Columbia. VanLooy and Forster (2008) noted that the glacier retreated at a rate of 30 meters/year from 1974 to 1992 and 47 meters/year from 1992-2000. Menounos et al (2018) identified a mass loss for glaciers in this region of ~0.5 m year from 2000-2018 which is driving retreat. The glacier is at the headwaters of jacobsen Creek, which joins the Talchako River and then Bella Coola River. The Bella Coola River is one of the most important salmon producing rivers on the British Columbia’s central coast. It supports the largest chinook and chum salmon populations, surveyed at 23k and 190k in surveys during the last decade (Pacific Salmon Foundation, 2021) The sockeye and pink salmon runs have largely collapsed this century (Pacific Salmon Foundation, 2021). In this post we examine Landsat satellite imagery from 1987-2019 and Sentinel imagery from 2021 to illustrate the changes.

In 1987 the glacier terminated in a 1.8 km long proglacial lake at an altitude of ~1080 m . The north margin had a separate terminus in the proglacial lake at Point A. The terminus in the main proglacial lake 900 m wide. At Point B there is an icefall, but not exposed bedrock. The snowline was at 2050 m. By 1995 the glacier had retreated 500 m. The glacier was in contact with the proglacial lake at Point A. The snowline was at 2100 m. By 2000 the glacier has retreated from the proglacial lake at Point A, due to thinning. In 2016 the snowline is at 2150 m. The glacier is now separated from the proglacial lake at Point A by ~500 m. The southern tributary no longer reaches the expanding proglacial lake. In 2018 there is bedrock exposed at Point B. The snowline is at 2100 m. In 2019 the proglacial lake has expanded to a length of 3.3 km, a retreat of 1500 m from 1987-2019. The retreat and lake expansion has been 1500 m from 1987-2019, a rate of 47 m/year, only a slight change from the 1990-2000 reported rate. The snowline is at 2100 m. In May 2021 the Sentinel image indicates the medial moraine has widened to the point there is no interaction between the northern and southern tributary of Jacobsen Glacier. The terminus in the expanding lake is now 400 m wide. The lake basin likely ends before Point C, based on surface slope changes of Jacobsen Glacier.

The retreat rate during this period is less than the ~120-130 m/year at Bridge Glacier, Franklin Glacier or Klinaklini Glacier, and slightly more than at Bishop Glacier and Klippi Glacier. The combined loss in glacier area impacts glacier runoff particularly in late summer. Moore et al (2020) examining the Columbia River basin headwaters of Canada noted, “that glacier-melt contributions to August runoff have already have passed peak water, and that these reductions have exacerbated a regional climate-driven trend to decreased August streamflow contributions from unglacierized areas.”

Jacobsen Glacier in Landsat images from 1995 and 2018. Red arrow 1987 terminus location, yellow arrow 2019 terminus location and pink dots the snowline. Point A indciates ice marginal lake in 1987, Point C is the glacier junction, Point B an emerging rock rib and Point D a nunatak.

Jacobsen Glacier in Landsat images from 2000 and 2016. Red arrow 1987 terminus location, yellow arrow 2019 terminus location and pink dots the snowline. Point A indciates ice marginal lake in 1987, Point C is the glacier junction, Point B an emerging rock rib and Point D a nunatak.

Sentinel Image from May 2021

Valdez Glacier, Alaska Significant Calving Retreat in 2020

On May 31, 2021April 23, 2024 By mspeltoIn alaska glacier retreat

Valdez Glacier terminus in Sentinel images from 6-27-2020, 8-21-2020 and 5-23-2021. In June the glacier’s terminus area is poised to collapse with extensive rifting and marginal proglacial lakes along the east and west margins. In July the terminus breaks up and in August the lake is filled by a flotilla of icebergs. The May image indicates the icebergs are still present.

Valdez Glacier is an outlet glacier from the Chugach Mountains that in the early 20th century descended onto a glacial outwash plain that the city of Valdez, Alaska is built upon. Today the glacier has retreated into a mountain valley and is calving into an expanding lake. David Arnold in the Double Exposure project documenting climate change photographically has a pair of images from 1938 and 2007 of the glacier. This post examines Landsat, Sentinel and Digital Globe images from 1986-2021 to document the retreat and lake expansion.

The 1948 map of the glacier indicates no lake at the terminus of the glacier, and the braided glacier emanating from the end of the glacier still building the outwash plain, note airport just southwest of terminus on plain.The terminus is marked by red arrows in map below. Seven kilometers upglacier of the terminus is a secondary terminus in a side valley. In the 1948 map, see bottom image, this glaciers is just in contact with Valdez Glacier, dark red arrow. With time both glacier termini retreat. By 1986 Landsat imagery indicates the development of a lake at the terminus and that the outwash plain is stabilizing, as indicated by complete vegetation development. The lake has an area of 1.1 km², and it is 1 km from the southern shore of the lake to the glacier. In 1986 and the snowline on the glacier is at 1000 m. By 2002 the west side of the lake is 1.5 from north to south and has an area of 1.8 km², the east side still extends to the southern shore of the lake. The snowline in 2002 is at 1300 m.

In 2011 the lake is 2 km from north to south. The snowline in 2011 is at 1300 m. In 2019 the lake is 2.3 km from north to south. Indicating a slow expansion continuing from 2011-2019. The snowline is at 1300 m in 2019. In June of 2020 the terminus is still in the same location though rifting and expansion of marginal open water indicates the terminus is poised to collapse. It does collapse in July and by August the significant calving event that occurred has generated numerous icebergs. The lake is now 4.4 km² and 3.4 km from the southern shore. The main terminus has retreated 2.8 km since 1986 and the tributary that was just separating in 1948 from the east has retreated 3 km from Valdez Glacier. The lake has increased 300% in area with, 30-40% of this change occurring in 2020. The snowline in 2020 was again at ~1300 m.

In the May 23 Sentinel image the icebergs are still filling a good portion of the lake. As summer 2021 commences anticipate more calving retreat as several significant rifts exist within 0.5 km of the calving front. The snowline elevation at 1300 m in late summer has been a common feature, which leaves 70% of the glacier in the ablation zone. Wouters et al (2019) report that Alaskan mountain glaciers have contributed more to sea level rise than any other region. The retreat at Valdez Glacier is not as large as that at Ellsworth Glacier that also had a significant calving in 2020. The retreat is much less than at Excelsior Glacier or Yakutat Glacier.

Valdez Glacier terminus in 1986, 2002, 2011 and 2020 Landsat images. Red arrow indicates 1986 terminus location and yellow arrows the 2020 terminus locations. Slow lake expansion from 1986-2019. The iceberg flotilla is evident in the middle of the lake in 2020.

Valdez Glacier in 1986 and 2020 Landsat images. Red arrow is the 1986 terminus, yellow arrow the 2020 terminus and purple dots the snowline.

Valdez Glacier in 2002 and 2019 Landsat images. Red arrow is the 1986 terminus, yellow arrow the 2020 terminus and purple dots the snowline.

1948 USGS Topographic map before a lake had formed. Red arrows indicate the terminus.

Vista Glacier, Glacier Peak WA Retreat and Snow Line Rise

On May 28, 2021April 23, 2024 By mspeltoIn North Cascade Glaciers1 Comment

Vista Glacier in 1998 and 2016 Digital Globe images with the the 1984 terminus red arrow and 2015 terminus yellow arrow, Point A is the rock seen below the glacier in 1994 image below and Point B is where the advance moraine reached the valley bottom.

Vista Glacier is a valley glacier flowing down the northeast side of Glacier Peak (Dakobed) that drains into the Suiattle River. The glacier begins at 2475 m beneath Kennedy Peak. We examined all of the glaciers around Glacier Peak in detail from 1993-1997 to document their changes since first closely observed by C.E. Rusk 100 years earlier. The glacier during the LIA joined the Ermine Glacier and extended down to 1345 m. By 1900 when Asahel Curtis photographed this glacier it had retreated 1300 m. By 1946 the glacier had retreated 1900 m from its LIA moraine, separated from Ermine Glacier and terminated at ~1900 m. In 1955 the glacier began a slow advance, all major Glacier Peak glaciers advanced during this period, that had ended by 1975 with a total advance of 105 m (Pelto and Hedlund, 2001).

Vista Glacier in 1988 aerial image illustrating the glacier is still adjacent to advance moraine.

In 1985 at our first visit the glacier was again retreating, total retreat was 10-20 meters from the advance moraine. By 1994 the glacier had retreated 90-100 m with the lower part of the glacier thin and crevassed. By 1997 the glacier had retreated beyond the 1946 position. The retreat accelerated after 2003 and had retreated and by 2016 the retreat from the 1984 mapped position was 410 m, a rate of ~13 m/year. The terminus is now at 1900 m.

In 1994 Cliff Hedlund and I were surveying the terminus when we found a beautiful ice cave beneath the glacier, see below. The rock just behind Cliff in the cave is apparent now out in the open in the Digital Globe image from 2016 and the LIDAR image from 2015 (Point A). Cliff was ahead of his time with the homemade neon colored gear that is perfect in an ice cave.

The red arrow in the image below looking down glacier in 1997 indicates the ice surface level in 1985, the glacier has thinned 20 meters in this region. Measuring snow depth up the middle of this glacier in 1994 and 1997 we found limited areas with accumulation of greater than 2 m in early August. This glacier is prone to losing most of its snow cover in many years such as occurred 2005, 2009, 2015 and 2019. Overall. This indicates considerable retreat will occur even with present climate. From 2013-2020 the end of summer snowline avearaged 2350 m, leaving just 35% of the glacier in the accumulatioin zone each year. To have an equilibrium balance North Cascade glaciers need an AAR of at least 55%, the percentage of glacier in accumulation zone (Pelto and Brown, 2012). We will back in the field this coming summer for the 38th consecutive year measuring the response of North Cascade glaciers to climate change.

1984 USGS Map of Vista Glacier and 2015 LIDAR (WA DNR) of Vista Glacier. Red line is the 1984 terminus and yellow line the 2015 terminus location. Note lack of crevasses in lower half of glacier.

Terminus change map of Vista Glacier from 1984-2015.

Cliff Hedlund in subglacial tunnel leading to Rock A in 1994.

View across lower half of glacier in 1997 towards Ermine Glacier indicating limited crevassing and flow of this thin section of the glacier

Vista Glacier in 2006 with the blue dots indicating the margin and resulting moraines emplaced by the advance from the 1950’s into the 1970’s.

Mena Kang West Glacier retreat and lake expansion, Tibet, China

On May 22, 2021April 23, 2024 By mspeltoIn china glacier retreat, Himalaya glacier retreat

Mena Kang West Glacier in 2002, 2020 and 2021 Landsat images. Red arrow is the 2000 terminus location, yellow arrow the 2021 terminus location and pink dots the snowline.

“Mena Kang West” Glacier is an unnamed glacier that is to the west of Mena Kang (6140 m) at 28 N, 91.6 W in Tibet, China. The glacier drains into the Nyamjang Chu, which flows south in Arunachal Pradesh, India. This region has seen the rapid expansion of many proglacial lakes due to glacier retreat. Allen et al (2019) mapped 1291 glacial lakes with an area greater than 0.1 km2, of these 204 posed a glacial lake outburst (GLOF) threat. Nyamjang Chu is not a basin that has experienced a significant GLOF. This basin does have a proposed hydropower project downstream in Arunachal Pradesh, but the project has not yet begun. Glacier retreat led to a 20% increase in the number of glacier lakes in the Pumqu region, the adjacent basin to the west (Che et al, 2014).

In 2000 the glacier terminates, at ~4820 m, in a 400 m long glacial lake with an area of 1.6 km². The snowline is near the top of an icefall at 5300 m. In late October 2002, the snowline is at 5100 m, the lake area is 1.7 km². By 2016 the glacial lake has expanded to 1000 m in length, the terminus is just below a crevassed area (C), indicating the calving front is leading to an acceleration of the glacier near its terminus. The snowline is at the top of the icefall at ~5300 m. In October 2020 a snowstorm has lowered the snowline to 5000 m. A warm dry early winter and particularly January throughout the region (NASA, 2021), has led to the snowline have risen and remained high at 5300-5400 m from January 16 -January 28, 2021. This is a summer accumulation glacier receiving the bulk of its snowfall in summer, but winter is supposed to be a period with some snowcover and limited ablation. That was not the case in the snow free winter to the end of January in 2020/21 (Pelto, 2021). By 2020 the glacier has retreated 600 m since 2000 and the lake area has expanded to 0.3 km². The high snowlines in recent years have been driving further retreat as noted at other glaciers in the area; Shie Glacier and Bailang Glacier.

Digital Globe imagery from 2018 of Mena Kang West Glacier illustrating the Icefall (I) at ~5300 m, the terminus crevasse zone (C), flow directions (blue arrows), snowline (pink dots) and recessional moraines (M).

Mena Kang West Glacier in 2000 and 2018 Landsat images and a 2021 Sentinel image. Red arrow is the 2000 terminus location, yellow arrow the 2021 terminus location and pink dots the snowline.

Herz Glacier, South Georgia Loses 25% of its Length 1989-2021

On May 13, 2021April 23, 2024 By mspeltoIn south georgia glacier retreat

Landsat images from 1989-2021 of Herz Glacier. Red arrow is 1989 terminus location, yellow arrows the 2021 terminus location. I=Iris Bay.

Herz Glacier is on the southeast coast of South Georgia Island, and is adjacent to the Twitcher Glacier. The terminus change of this tidewater glacier ending in Iris Bay was completed by the British Antarctic Survey for the 1960-2011 period, see map below (Gordon et al, 2008). This map indicates the slow retreat from 1960-1988 and a more rapid retreat since. Here we utilize Landsat imagery from 1989-2021 to examine terminus change.

In 1989 the glacier is 10 km long with the terminus located in the east trending arm of Iris Bay at a point where it widens substantially. Point A is the midway point of the glacier. By 2002 the terminus has retreated ~1.1 km to Point B in a narrower portion of the fjord. The calving front is 0.9 km wide in 2002. By 2009 the glacier had retreated 1.8 km on the north side of the fjord and 2.2 km on the south side. The overall 2 km retreat is a rate of 100 meters/year and is 20 % of the total glacier length (Pelto, 2017). By 2015 the terminus has retreated into an even narrower portion of the fjord, which would reduce calving. The snowline in both 2002 and 2015 is ~1000 m. In 2021 the terminus has continued to recede and could be nearing the head of the fjord. The snowline in 2021 is somewhat above 1000 m in the early March landst image.

The retreat has been 2.5 km in the 32 year period from 1989-2021, a rate of 78 m/year. The glacier is nearing the inland end of the ridge separating Herz from Twitcher. As both Twitcher Bay and Iris Bay have expanded there are certainly new locations for both elephant seal and penguin colonies (BAS, 2018). The retreat of this glacier is comparable to that of other South Georgia glaciers noted by NASA Earth Observatory; Neumayer Glacier, Twitcher Glacier and Hindle Glacier.

Landsat images from 2002 and 2015 of Herz Glacier. Red arrow is 1989 terminus location, yellow arrows the 2021 terminus location. I=Iris Bay.

Map of Herz Glacier area from the British Antarctic Survey, illustraing glacier front changes 1988-2011. Yellow crosses mark elephant seal beaches and purple dots penguin colonies, which can expand to new locations in this opening fjord.

Upsala Glacier Separation from Bertacchi Glacier, Argentina

On May 7, 2021April 23, 2024 By mspeltoIn argentina glacier retreat1 Comment

Upsala Glacier (U) in Landsat images from 1999, 2016 and 2021 illustrating both retreat and the separation from Bertacchi Glacier (B). Cono Glacier (C) is the next tributary to the north.

Upsala Glacier is a major outlet glacier of the Southern Patagonia Icefield. The glacier terminates in Lago Argentina and retreated substantially, 7.2 km from 1986-2014 (NASA, 2014). The retreat accelerated after 2008 (Sakakibara et al 2013). From 2014-2019 the rapid retreat had slowed, but given mass losses upglacier and consistent high snowlines ~1300 m in 2018-2021, not for long.

Landsat images from 1999-2021 illustrate the retreat of the glacier. In 1999 the terminus is 3 km south of the junction. By 2016 the terminus has retreated to the junction. The combined calving front has a width of 2.8 km, and there is a 1.3 km long connection zone between Bertacchi and Upsala. By April and May 2021 the separation is nearly complete with a 0.3 km long connection zone, and in increase to 3.3 km wide calving front, in a Sentinel 2 image from May 5, 2021. The glaciers that have been joined for many centuries if not millenia, provide stability to each other at the junction, as there is converging flow that buttresses both. As this buttressing is removed, the terminuses of both glaciers in the vicinity of the current terminus will be less stable.

De Angelis (2017) noted the equilibrium line for Upsala Glacier was 1170 m based on 2002 and 2004 observations, which equates to an AAR of 65%. On Feb 14, 2018 the TSL reached its highest observable elevation at 1275-1300 m. On March 14, 2019 the TSL reached 1300 m again. On April 8, 2020 the TSL reached 1325-1350 m upglacier of Point A and nearly to the Viedma Glacier divide. On April 17, 2020 the TSL had descended slightly to 1300 to 1325 m. The ELA of ~1350 m is the highest annual observation for Upsala Glacier and equates to an AAR of ~48%. On April 17, 2021 the snowline on Upsala Glacier is again at ~1300 m. The consistently high snowlines drive mass balance losses, which leads to thinning and reduced flux to the terminus. Malz et al (2018) indicated a 3.3 m thinning of Upsala glacier with significant thinning extending to the Viedma Glacier divide. Popken et al (2019) mapped the velocity at the confluence. The much slower Bertacchi has a low terminus velocity, in part due to the buttressing of Upsala.

The separation of Upsala Glacier due to rapid retreat parallels this pattern observed at other Southern Patagonia icefield outlet glaciers; Lago Onelli and Dickson Glacier

May 5, 2021 Sentinel image of terminus zone of Upsala and Bertacchi Glacier.

Snowline on Upsala Glacier in April 2020 and 2021 Landsat images-pink dots, both years above 1300 m.

Terminus of Bertacchi and Upsala glacier in Apil 2020 and March 2021, note icebergs in March of 2021 from recent calving.

Shafat Glacier Separation and Stagnation, India

On April 30, 2021April 23, 2024 By mspeltoIn India glacier retreat, Kashmir glacier change

Shafat Glacier in 1997 and 2020 Landsat images. 1-6 are different tributaries with the main glacier being #1. A marks the junction of #1 and #6.

Shafat Glacier occupies the northeast flank of Nun Kun Peak in Ladakh India and drains into the Suru valley. The main valley glacier (1) has been fed by a decreasing number of tributaries. Shukla et al (2020) identified an increase in annual temperature has driven a 6% loss in regional glacier area and a 62% expansion in debris cover from 1971-2017. Here we compare Landsat imagery from 1997-2020 to identify this glaciers response to climate change.

In 1997 and 1998 tributary 2 and 3 join and then the debris covered sections connects to the main valley glacier #1. Tributary 4 terminus is the meeting point of two glacier tongues. The active non-debris covered ice of Tributary #6 reaches to the valley adjacent to Point A where it meets the main valley tongue. The active clean ice of the main tongue extends beyond Point A. In 1997-2000 the terminus is heavily debris covered with the main discharge from beneath the glacier at Point B. The active ice of Tributary 6 extends to within 1.5 km of the terminus, while the active/clean ice of the main tongue extends to within 1.3 km of the terminus. The snowline is at 4900 m in 1997 and 5100 m in 1998. By 2018-2020 the active ice area now ends 2.5 km from the terminus for Tributary 6 and 5.1 km from the terminus for the main glacier. Debris cover extends 5.3 km from the terminus up the main tongue and 2.7 km from terminus at Point B up Tributary 6. Retreat is hard to discern with the extensive stagnant debris covered area. Tributary 4 has separated into two parts, and tributary 2 and 3 have separated from each other and the main valley glacier. In 2018 the snowline is at 5200 m, while in 2020 it is 5050 m. The consistent high snowlines have led to glacier thinning, debris cover expansion, and increasing stagnation of the main glacier tongue. The stagnation is indicated by the increasingly concave cross profile and the lack of crevassing in the lower 5 km of the main glacier tongue below 4600 m. The low slope of the glacier from 4250-4400 m, of 4.8% suggests a proglacial lake could form in this reach of the main valley.

The glacier volume loss is more substantial than the area loss, with retreat less than on Kolahoi Glacier, but volume loss similar (Rashid et al 2019). Loss of glacier area leads to summer glacier runoff declines, which impacts irrigation Rashid et al 2019). The Suru River also has a 44 MW run of river Chutak Hydropower plant.

Shafat Glacier in 1998 and 2018 Landsat images. 1-6 are different tributaries with the main glacier being #1. A marks the junction of #1 and #6.

Digital Globe image of the terminus reach in 2000 and 2019. B marks the location of main river exiting from beneath the glacier. A marks the junction of the two glaciers. 1 and 6 indicate the two main glaciers that join 2 km above the Shafat Glacier terminus. Note debris cover spread particularly on main tongue.

Geikie Glacier, Alaska Lofty No More

On April 21, 2021April 23, 2024 By mspeltoIn alaska glacier retreat

Geikie Glacier (G) in 1986 and 2018 Landsat images. Pink arrow is the 1954 terminus, red arrow the 1986 terminus and yellow arrow the 2018 terminus location. GI is Geikie Inlet which the glacier withdrew from 110 years ago.

Geikie Glacier is on the west side of Glacier Bay, Alaska. John Muir in October 1879 observed Geikie Glacier in Geikie Inlet, which had separated from Muir Glacier within the last 20 years. He wrote in John Muir Travels in Alaska, “Its lofty blue cliffs, looming through the dragged skirts of the clouds, gave a tremendous impression of savage power, while the roar of the newborn icebergs thickened and emphasized the general roar of the storm.” By 1892 when surveyed by H.F. Reid it had retreated to within several kilometers of the head of the inlet. It retreated from tidewater in ~1910 (Field, 1966), with the full inlet being 15 km in length. I had the opportunity to visit the glacier in 1982 arriving by float pane at the X at the head of the inlet. There was no glacier even in sight, where a century before was buried beneath thick glacier ice. It took us four hours to reach the terminus through what was a mixed outwash plain with developing shrubs. Today that same journey would be much more difficult as the shrubs, trees and undergrowth have thickened. William O. Field with the American Geographical Society visited Geikie Glacier in 1935, 1941, 1950 and 1958, noting limited retreat from tidewater up to 1935. though considerable frontal thinning was evident. Here we examine the changes using Landsat images from 1986, 2018 and 2019 combined with the 1961 USGS Mount Fairweather C-2 topographic map based on 1948 and 1955 photographs.

By ~1950 the glacier had retreated 2.1 km from tidewater, a rate of 50 m/year. The retreat had been interrupted by a small advance around 1920 (Field, 1966). In 1950 the glacier is fed by four tributary glaciers, with three feeding in, as the glacier makes an eastward turn. By 1986 the terminus had retreated 4.3 km from tidewater, no longer rounding the eastward bend, the retreat rate since ~1950 had been ~60 m/year. Tributaries 1-3 had separated from the glacier.

In 2014 and 2015 the glacier lost all of its snowcover (see below). In 2018 the glacier had retreated 4.1 km since 1986 and 8.3 km from the inlet. The rate had increased to ~125 m/year. Tributary 4 had separated from the glacier. The glacier shares a divide at ~600 m with a south flowing glacier and the head of the glacier is at ~1000 m. In 2014, 2015, 2018 and 2019 the entire glacier lost all of its snowcover, indicating a glacier that cannot survive, as a consistent accumulation zone is essential (Pelto, 2010). The demise of Geikie Glacier is less complete than that of nearby Burroughs Glacier, but with current climate no less certain. The glacier was ~14.5 km long when I journeyed there in 1982 and in 2018/19 is just 6.1 km long, a loss of 58% of its length in 36 years.

In 2018 and 2019 the snowlines were the highest of any year since at least 1946 on nearby Taku Glacier (Pelto, 2019) and on Brady Glacier. The rising snow lines on Brady Glacier had been observed in recent years by Pelto et al (2013). which has led to the start of a retreat. The lack of retained accumulation has also been noted at Lemon Creek Glacier and similar to Brady Glacier, Taku Glacier has now began a retreat ( McNeil et al, 2020).

Geikie Glacier (G) in 1961 USGS map and 2019 Landsat image. Red arrow the 1986 terminus and yellow arrow the 2018 terminus location. GI is Geikie Inlet which the glacier withdrew from 110 years ago.

US Navy aerial photograph of Geikie Glacier terminus in 1948, tributaries 1-3 labeled. Digital Globe Image of the glacier in 2014, Point A in both is head of eastward turn.

Benito Glacier, Chile 2021 Calving Event Drives Further Retreat

On April 13, 2021April 23, 2024 By mspeltoIn chile glacier retreat, climate change glacier retreat, glacier climate change

Benito Glacier in 2000 and 2021 Landsat images. Locations 1-6 are current or former distributary terminus locations. Red arrow is the 2000 terminus location and yellow arrow the 2021 terminus location. A small cloud is obscuring an iceberg near terminus. Purple dots are the snowline.

Benito Glacier is a temperate outlet glacier on the west side of the North Patagonian Icefield terminating in an expanding lake. The glacier is south of San Quintin Glacier and north of Acodado Glacier. Loriaux and Casassa (2013) examined the expansion of lakes of the Northern Patagonia Ice Cap. From 1945 to 2011 lake area expanded 65%, 66 square kilometers. Ryan et al (2018) identified thinning of 2.8 m/year in the ablation zone from 2000-2013, and that thinning of over 120 m extended from the terminus to ~750 m from 1973-2017. Mouginot and Rignot (2015) indicate that the velocity of Benito Glacier is between 200-500 m per year along the center line below the snowline. Glasser et al (2016) note the glacier has limited debris cover and that the average transient snowline in 2013-2016 is at 1000 m, substantially above the ~900 m average from earlier.

Benito Glacier in 1987 main terminus was on an outwash plain. The glacier has five distributary termini (1,2,34,5,6) two of which had open proglacial lakes in 1987. At Point 3 the glacier flows around a nunatak and reconnects. In 2000 a 1 km long proglacial has formed at the main terminus. Distributary termini 1,2 and 4 all have proglacial lakes. The snowline in 1987 and 2000 is 800-825 m. By 2015 there are five ending in lakes, with Lake 6 having retreated out of a lake basin. A lake has formed at the new distributary terminus at Lake 3. The two tributaries to the north indicated with arrows each retreat approximately 1 km from 1987 to 2015 and in both cases are no longer calving termini. The main glacier terminus has retreated into a proglacial lake, with a retreat of 2 km from 1987 to 2015. The lowest 1.5 km has a low slope and peripheral lakes suggesting the lake will expand substantially as Benito Glacier retreat continues. The transient snowline in 2015 is at 900 m. In 2021 a significant iceberg 0.4 km² has calved off the terminus. The terminus has retreated 2900 m from 1987-2021 with the lake area expanding to 2.8 km². The lower 1.5 km of the glacier remains low sloped suggesting significant lake expansion is ongoing. The glacier no longer reaches the former proglacial lake 2 or 6. Proglacial lake 1 has drained. Proglacial lake 2,3, and 4 continue to expand. The snowline on Feb. 6 2021 is at 875-900 m, rising to 925-950 m by March 16, 2021.

March 17, 2021 Landsat image indicating iceberg located off front of Benito Glacier

Benito Glacier comparison in Landsat images from 1987 and 2015 indicating the terminus position in 1987 red arrows, yellow arrows the 2015 terminus positions. Locations 1-6 are current or former distributary terminus locations. purple arrows where glacier thinning is expanding bedrock areas. The snowline is indicated by purple dots