Steffen Glacier, Chile Calving Retreat Acceleration 2019

On November 16, 2019April 24, 2024 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 km²in 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 km²in 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 November 10, 2019April 24, 2024 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 October 31, 2019April 24, 2024 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.

Falcon Glacier, British Columbia Wings Clipped by Climate Change

On October 22, 2019April 24, 2024 By mspeltoIn British Columbia glacier retreat1 Comment

Falcon Glacier in 1985 and 2019 Landsat images indicating the 2000 m retreat. Red arrow is 1985 terminus location, yellow arrow the 2019 terminus location. I=icefall locations joining the glacier.

Falcon Glacier in southwest British Columbia drains east from the Compton Neve into the Bishop River, which then joins the Southgate River. The Southgate River is one of three major watersheds emptying into the head of Bute Inlet. The Southgate River is known for the large runs of Chum Salmon. The area was the focus of a proposed Bute Inlet hydropower, that at present is no longer being pursued. The region has experienced large negative mass balances 2000-2018 (Menounos et al 2018), that is driven retreat of many glaciers in the immediate area such as Bishop Glacier and Klippi Glacier. Here we examined Landsat images from 1985 to 2019 to determine the response to climate change of Falcon Glacier.

In 1985 Falcon Glacier terminated at 980 m and was over 10 km long (red arrow). There were two icefalls (I) feeding the glacier along with the two principal tributaries. By 2002 the glacier had retreated 800 m, with narrow ponding in front of the terminus. The two icefalls were still active and the medial moraine extending to the terminus had increased prominence. By 2015 the glacier had retreated another 800 m and the two icefalls are barely connected to the main glacier. The snowline is higher in 2015 at 1850 m. By 2019 Falcon Glacier had retreated 2000 m, losing 20% of its length since 1985. The eastern icefall no longer rejoins the main glacier. The western icefall is barely connected. The snowline in early August 2019 is already at 1850 m indicating a limited accumulation area again. The high snowlines and continued expansion of bedrock areas even at 2000 m indicates the glacier will continue its rapid retreat.

Falcon Glacier in 2002 and 2015 Landsat images indicating the 2000 m retreat. Red arrow is 1985 terminus location, yellow arrow the 2019 terminus location. I=icefall locations joining the glacier.

Map of Falcon Glacier indicating flow direction and icefalls (I).

Nordenskjold Glacier, South Georgia Retreat Accelerates

On October 18, 2019April 24, 2024 By mspeltoIn south georgia glacier retreat

Nordenskjold Glacier in 1993 and 2019 Landsat images. Red arrow is the 1989 terminus location, yellow arrows the 2019 terminus location. Purple arrow is a tributary that has separated. Point #1 and #3 is expanding bedrock ribs. Point #2 is an impounded glacial lake.

Nordenskjold Glacier is a tidewater glacier flowing into Cumberland East Bay on the east coast of South Georgia, Island. Cook et al (2010) and Gordon et al (2008) noted a pattern island wide with many calving glaciers having the fastest retreat. Gordon et al., (2008) observed that larger tidewater glaciers remained in relatively advanced positions from the 1950’s until the 1980’s, followed by significant recession, this retreat was delayed on Nordenskjold Glacier until 2000. The map below from the British Antarctic Survey indicates the slow retreat from 1957-1998 and a more rapid retreat since. Here we use Landsat imagery from 1989-2019 to identify changes.

In 1989 the glacier terminated at approximately the same location as in 1957. Vegetation extended quite close to the terminus with a minimal trimline or recently deglacated zone evident. At Point #1 and #3 are bedrock ridges that generate medial moraines. At Point #2 is a glacial lake impounded by a secondary terminus. At the purple arrow is a tributary glacier joining the main glacier. By 1993 there has been a limited retreat exposing some newly deglaciated unvegetated terrain adjacent to the shoreline and glacier terminus. There was limited additional retreat up to 2000. This is unusual as the neighboring glaciers had all retreated substantially by 2000. By 2016 the glacier had retreated substantially, ~900 m. The tributary at the purple arrow no longer reaches the main glacier. At Point #2 the impounded lake has expanded slightly and is open water. The snowline is also at 500 m above Point #1 and #3. In 2019 the snowline is again above 500 m. The area of bedrock at Point #1 and #3 has expanded significantly indicating glacier thinning, and greater ablation at this elevation. The terminus has retreated an average of 1250 m from 1989-2019. There is a significant trimline and recently deglacited terrain on the western shore of the bay.

The retreat is much less than on Neumayer, Twitcher or Hindle Glacier. The upglacier thinning suggests this process will continue, with a 3.2 km wide calving front in water of unknown depth calving will continue to be a key driver of retreat.

Nordenskjold Glacier in 1989 and 2016 Landsat images. Red arrow is the 1989 terminus location, yellow arrows the 2019 terminus location. Purple arrow is a tributary that has separated. Point #1 and #3 is expanding bedrock ribs. Point #2 is an impounded glacial lake.

Map of terminus change from the British Antarctic Survey map platform

Taku Glacier, Alaska Retreat Begins: A Two Century Long Advance Reversed by Climate Change

On October 9, 2019April 24, 2024 By mspeltoIn alaska glacier retreat10 Comments

Taku Glacier in 2016 and 2019 Sentinel 2 images. The Hole in the Wall Tributary (HW) is upper right, Taku Glacier main terminus (MT). Yellow line is the 2016 terminus location. The arrows denote locations where thinning is apparent as the area of bare recently exposed bedrock has expanded. A closeup is below. Pink and brown areas between blue ice and yellow line in 2019 indicates retreat.

The Taku Glacier is the largest outlet glacier of the Juneau Icefield in Alaska. Taku Glacier began to advance in the mid-19^th century and this continued throughout the 20^th century. At first observation in the 19^th century the glacier was calving in deep water in a fjord. It advanced 5.3 km between 1890 and 1948 moving out of the fjord into the Taku River valley, see maps below (Pelto and Miller, 1990). At this time calving ceased resulting in positive mass balance without the calving losses. The glacier continued to advance 2.0 km from 1948-2013 (Pelto, 2017). The advance was paralleled by its distributary terminus, Hole in the Wall Glacier. This advance is part of the tidewater glacier cycle (Post and Motyka, 1995), updated model by Brinkerhoff et al (2017) . At the minimum extent after a period of retreat the calving front typically ends at a point of constriction in fjord width and or depth that limits calving. With time sedimentation in front of the glacier reduces water depth and calving rate, allowing the glacier to begin to advance. In the case of the Taku Glacier after a century of advance the glacier had developed a substantial proglacial outwash and moraine complex that had filled in the fjord and the glacier was no longer calving, images below from 1961 and 1981 illustrate this. This allowed the advance to continue through the rest of the 20^th century and into the 21^st century. The slowing of the advance in the latter half of the 20^th century has been attributed to the impedance of the terminus outwash plain shoal (Post and Motyka, 1995; Pelto and Miller, 1990). There is a concave feature near the terminus with an increase in crevassing where the push impacts flow dynamics as seen at black arrow in 1975 and 1998 images below. In 1980’s the Taku Glacier’s accumulation area ratio was still strong enough for Pelto and Miller (1990) to conclude that the Taku Glacier would continue to advance for the remaining decade of the 20^th century, which it did.

Beginning in 1946 the Juneau Icefield Research Program began annual mass balance measurements that is the longest in North America. In conjunction with JIRP and its first director Maynard Miller we compiled and published an annual mass balance record in 1990. From 1990 to the present in conjunction with JIRP and Chris McNeil we have continued to compile and publish this annual mass balance record (Pelto et al 2013). This mass balance record has been updated as of April 2020 (McNeil et al 2020). Much of the remarkable data record of JIRP has this month been made accessible to the public, particularly through the efforts of Seth Campbell, JIRP director, Scott McGee, survey team director and Chris McNeil, mass balance liaison with USGS.

**The ELA in 2018 and 2019 in Landsat images, purple dots indicate the record high snowlines for the 1946-2019 period that occurred both in 2018 and again 2019, Pelto (2019)**

Taku Glacier is one of the thickest known alpine temperate glacier, it has a maximum measured depth of 1480 m and its base is below sea level for 40-45 km above the terminus (Nolan et al 1995). Moytka et al (2006) found that the glacier base was more than 50 m below sea level within 1 km of the terminus, and had deepened substantially since 1984. This suggests a very long calving retreat could occur. The glacier had a dominantly positive mass balance of +0.42 m/year from 1946-1988 and a dominantly negative balance since 1989 of -0.34 m/year (Pelto et al 2013). ^.This has resulted in the cessation of the long term thickening of the glacier. On Taku Glacier, the annual ELA (end of summer snowline altitude) has risen 85 m from the 1946-1988 period to the 1989-2019 period. During the 70+ year annual record the ELA had never exceeded 1225 m until 2018, when it reached 1425 m ( Pelto (2019) ). In 2019 the ELA again has reached a new maximum of 1450 m (see above images). Contrast the amount of the glacier above the snowline in 2018 and 2019 to other recent years that had more ordinary negative balances (see Landsat images below).

In 2008 and 2012 JIRP was at the terminus, creating the map below. There was no change at the east and west side of the margin since 2008 and 55 to 115 m of advance closer to the center. The glacier did not advance significantly after 2013, and did not retreat appreciably until 2018. The Taku Glacier cannot escape the result of three decades of mass losses, with the two most negative years of the record being 2018 and 2019. The result of the run of negative mass balances is the end of a 150+ year advance and the beginning of retreat. Sentinel images from 2016 and 2019 of the two main termini Hole in the Wall Glacier right and Taku Glacier left. The yellow arrows indicate thinning and the expansion of a bare rock trimline along the margin of the glacier. The Hole in the Wall terminus has retreated more significantly with an average retreat of ~100 m. The Taku main terminus has retreated more than 30 m along most of the front. A terminus change record has been published as of April 2020 (McNeil et al 2020).

The retreat is driven by negative balances, mainly by increased surface melt. The equilibrium flow of the Taku Glacier near the long term ELA for the 1950-2005 period was noted by Pelto et al (2008). This occurred during a period of glacier thickening, average profile velocity was 0.5 md^-1 (Pelto et al 2008). Since 1988 the glacier has not been thickening near the snowline as mass balance has declined slightly (Pelto et al 2013). The remarkable velocity consistency measured by JIRP surveyors led by Scott McGee each year at profile 4 has continued. It is below this profile that surface ablation has reduced the volume of ice headed to the terminus.

All other outlet glaciers of the Juneau Icefield have been retreating, and are thus consistent with the dominantly negative alpine glacier mass balance that has been observed globally (Pelto 2017). Now Taku Glacier joins the group unable to withstand the continued warming temperatures. Of the 250 glaciers I have personally worked on it is the last one to retreat. That makes the score climate change 250, alpine glaciers 0.

**1890 United States Coast Guard Map indicating deep water in the fjord in front of Taku Glacier.**

**Map of terminus change from Lawrence (1950).**

**Taku Glacier aerial photograph from US Navy in 1948. Still minor calving on right (east side).**

**Taku Glacier in 1961 photograph indicating calving had ended.**

Taku Glacier in 1981 photograph with the well developed outwash plain (Pelto).

**Map of Terminus Change from Miller and Pelto (1990)**

**Maynard Miller image of Taku Glacier and Norris Glacier in 1975, not concave flexure point at black arrow.**

**Photograph of Taku Glacier and Norris Glacier in 1998, not concave flexure point at black arrow (Pelto)**

**JIRP terminus survey map of 2008 and 2012 surveys.**

**Equilibrium line altitude (ELA) from 1946-2019.**

**ELA in 2013, 2014, 2015 and 2017 in Landsat images.**

**This is a view across the glacier accumulation area that until 2018 had always been snowcovered at the end of summer (Pelto).**

Ofhidro Glacier, Chile Retreat 1986-2019

On October 1, 2019April 24, 2024 By mspeltoIn chile glacier retreat

Ofhidro Glacier glacier terminus change an accumulation zone changes from 1986-2019 in Landsat images. Red arrow=1986 terminus, yellow arrow=2019 terminus change, orange arrows expanding bedrock areas and purple dots snowline.

Ofhidro Glacier is an outlet glacier on the northwest corner of the Southern Patagonia Icefield (SPI), that has a northern and southern arm terminating in a proglacial lake. Sakakibara and Sugiyama (2014)a examine the terminus change and velocity of SPI glaciers the northern arm retreating 50 m per year from 1985-2011 and the southern arm 100 m/year 1985-2011. They also noted a decline in velocity Here we examine Landsat imagery from 1986-2019 to identify the change.

In 1986 the southern arm extended across the proglacial lake to the shallows of the western shore. The northern arm had been retreating in a narrower valley with a comparatively consistent width. In 1998 the southern arm in the broader lake reach had collapsed, a retreat of 1800 m. The northern arm had a retreat of 200 m. The snowline was at m. In 2015 the southern arm has retreated into a narrower valley, and the northern arm has retreated to a turn to the south in the valley. The orange arrows indicate the expansion of bedrock as the glacier thins. By 2019 the southern arm has retreated 2800 m (88 m/year) and the northern arm has retreated 1800 m (56 m/year). Jaber et al (2019) noted a thinning of 0.5 m/year from 2000-2012 increasing to 1.2 m/year from 2012-2016. Most of the thinning being in the valley tongues of each arm. There is an area of continuous exposed bedrock more than 3 km long. This fits the observations of Willis et al (2012) who observed that between February 2000 and March 2012 that SPI was rapidly losing volume and that thinning extends even to high elevations. The retreat of this glacier is similar to that of Lucia Glacier and Gabriel Quiroz Glacier to the east.

Ofhidro Glacier glacier terminus change an accumulation zone changes from 1998-2015 in Landsat images. Red arrow=1986 terminus, yellow arrow=2019 terminus change, orange arrows expanding bedrock areas and purple dots snowline.

Ofhidro Glacier image from 2015. Notice the trimlines and narrowing of both terminus tongues. Orange arrow indicates new bedrock knob.

Orsabreen, Svalbard Retreat leads to Lake Tripling in Size

On September 23, 2019April 24, 2024 By mspeltoIn svalbard glacier retreat

Response of Orasbreen (O), Glopeken (G) and Holmstrombreen (H) to climate change as indicated by 1995 and 2019 Landsat images. Red arrow is 1995 terminus, yellow arrow 2019 terminus, pink arrows a deepening supraglacial stream channel and purple dots the snowline.

Orsabreen terminates in an expansing prolgacial lake, Trebrevatnet, that is shared with a glacier it has separated from Holmstrombreen. The glacier shares an accumulation zone with Kronebreen, a glacier that is experiencing rapid retreat, and is fast flowing (How et al 2017). The high discharge of Kronebreen indicates a high volume of accumulation above 650 m in the shared accumulation zone, the Holtedahlfonna. Nuth et al (2010) from 1965-2007 reported the mean mass balance of Svalbard glaciers, excluding Austfonna and Kvitøya, as −0.36 m yr⁻¹ . They noted that Orsabreen had less volume loss −0.24 m yr⁻¹and did have an increase at higher elevation. Ruppel et al (2017) observed annual accumulation of 0.9 m w.e. at 1100 m on Holtedahlfonna from 2005-2015. Trebrevatnet expands both through glacier retreat and the melt out of ice cored moraine that comprises much of its margin, they observed 0.9 m of annual melt of the dead ice moraine areas (Schomacker and Kjaer, 2007).

In 1995, Trebrevatnet has an area of 4.0 km² the terminus of Holmstrombreen, Glopeken and Orsabreen merge, separated by medial moraines. In 2000 Holmstrombreen has retreated allowing Trebrevatnet to expand westward, while the medial moraine between Orsabreen and Glopeken still extends across the valley between Orsabreen and Trebrevatnet. The snowline in 2000 is at 550 m. In 2017 the snowline is at 600 m. Glopeken, Homstrombreen and Orsabreen have retreated into separate valleys. The medial moraine between Glopeken and Orsabreen has melted away. In 2019 the snowline is at 500 m, Trebrevatnet has expanded to an area of 13.5 km², more than tripling in area. This is due primarily to the 2200 m retreat of Orsabreen. The moraine melt out has expanded the length of the lake from 2.3 km to 7.5 km. The thinning of the lower Holmstrombreen is evident by the deepening of the supraglacial stream indicated by the pink arrows in the 2000 and 2019 images. A closeup view of the terminus from TopoSvalbard from prior to 2010 indicates both a deeply incised supraglacial stream indicating relative stagnation of the terminus (purple arrows), extensive crevasses that have become rifts near the terminus (green arrows) and the ice cored moraine that is now gone, blue arrows. This portion of the glacier has now been lost. In 2019 the lowest 1 km of the glacier is relatively stagnant and poised to be lost. The tongue of the glacier below 550 m is too large to be supported by the smaller accumulation area above this feeding from the Holtedahlfonna. The retreat here is less than most of the tidewater glaciers in Svalbard such as Hinlopenbreen or Paierbreen, but similar to lake terminating glaciers like Gandbreen.

Response of Orasbreen (O), Glopeken (G) and Holmstrombreen (H) to climate change as indicated by 1995 and 2019 Landsat images. Red arrow is 2000 terminus, yellow arrow 2017 terminus, pink arrows a deepening supraglacial stream channel and purple dots the snowline.

TopoSvalbard map and image of the Orsabreen terminus area and expansion of Trebrevatnet. Light blue arrows indicate ice cored medial moraine, light green arrows indicate rifts, and purple arrows a deep supraglacial channel.

Gilkey Glacier Retreat Leads to Rapid Lake Expansion in 2019

On September 17, 2019April 24, 2024 By mspeltoIn alaska glacier retreat

Gilkey Glacier in 1984 and 2019 Landsat images indicating retreat of 4300m, tributary separation and 5 km² lake expansion. A=Terminus tongue, B=Battle Glacier, G=Gilkey Glacier and T=Thiel Glacier.

Gilkey Glacier draining the west side of the Juneau Icefield has experienced dramatic changes since I first worked on the glacier in 1981. The Gilkey Glacier is fed by the famous Vaughan Lewis Icefall at the top of which Juneau Icefield Research Program (JIRP) has its Camp 18 and has monitored this area for 70 years. Here we examine the changes using Landsat images from 1984, 2014, 2018 and 2019. Landsat images are a key resource in the examination of the climate change response of these glaciers (Pelto, 2011). The August 17th 1984 image is the oldest high quality Landsat image, I was on the Llewellyn Glacier with JIRP on the east side of the icefield the day this image was taken. JIRP was directed by Maynard Miller at that time and by Seth Campbell now.

In 1984 Gilkey Glacier terminated in a new proglacial lake that had and area of 1.5 km² (#1). At #2 Thiel and Battle Glacier merged and then joined Gilkey Glacier. Arrow #3 and #4 indicates valleys which tongues of the Gilkey Glacier flow into, at #3 the glacier extended 1.6 km upvalley. At arrow #4 the glacier extended 1.5 km up Avalanche Canyon. At #6, #7 and #9 tributaries flow into the Gilkey Glacier. At #8 Antler Glacier is a distributary glacier terminus that spilled into a valley terminating short of Antler Lake.

By 2014 the proglacial lake had expanded to 3.65 km² as the glacier has retreated 3200 m. Thiel and Battle Glacier have separated from Gilkey Glacier and from each with a retreat of 2600 m for Thiel Glacier and 1400 m for Battle Glacier. The glacier no longer flows into the valley at #4. Tributaries at #6 and #9 no longer reach Gilkey Glacier. At #7 there is not a direct flow connection, but is still an avalanche connection. At #8 Antler Glacier has retreated 2200 m.

In 2018 and 2019 the snowline on the Juneau Icefield has been the highest of any year since observations began in 1984. This will accelerate mass loss and lead to continued extensive retreat. In 2018 the snowline was at 1600-1650 m on Sept. 16. In 2019 the snowline on Gilkey Glacier was 1650-1700 m on Sept. 10. In July of 2019 the terminus tongue of the glacier reached across the junction of the Gilkey and Battle Valley, separating the two proglacial lakes. By September 10, the glacier tongue had broken off leading to the two lakes joining expanding the size of the proglacial lake to 6.5 km². The terminus has retreated 4300 m since 1984, while the lake has increased in size by more than 400%. The retreat will continue leading to additional lake expansion just as is occurring at Meade and Field Glacier.

The expansion of Gilkey Lake into the Battle Valley in 2019 Landsat images.

Gilkey Glacier in 1984 and 2019 Landsat images indicating retreat of 4300m, tributary separation and 5 km² lake expansion. A=Terminus tongue, B=Battle, Bu=Bucher, G=Gilkey, T=Thiel, V=Vaughan Lewis. Snowline=purple dots.

Gilkey Glacier in 2014 and 2018 Landsat images indicating retreat, snowline elevation and lake expansion.

Glacier Crevasses As A learning Tool

On September 12, 2019April 24, 2024 By mspeltoIn glacier climate change, Glacier Observations3 Comments

Guest Post by Clara Deck

Instagram: @scienceisntsoscary

Crevasses on mountain glaciers are large cracks in the ice which often propagate from the surface downward. The initial break will happen when stress exceeds the inherent ice material strength. This article will focus on surface crevasses, though this basic physical understanding also applies to basal crevasses or large-scale rifts in ice sheet and shelf settings.

In mountain glacier systems, crevassing is likely to occur as ice flows over bedrock “steps.” Imagine you are baking a pie, and it is time to mold your pie crust to the pan. You must be very careful when bending the dough around the pie pan, because it may crack if you fold it too much or too suddenly.

Glaciers are the same way, and so another driver for crevasse formation is ice flow speed up in these areas. Other factors that could be at play are roughness of the underlying bed or drag along valley walls. The above photo of Rainbow Glacier shows a complex surface of crevassed and smooth areas, which hints to a similarly complex underlying bed.

During the 2019 field season of the North Cascades Glacier Climate Project, we measured these crevasses in a few different ways. Seven field seasons ago, Jill Pelto began collecting data on crevasse depth. She uses a cam line, which is essentially a weighted tape measure, to determine total crevasse depth on each glacier. This photo shows Jill measuring a crevasse on Easton Glacier. She tries to analyze crevasses in similar regions of the glaciers from year to year to achieve a cohesive dataset which could be useful on a long-time scale. This data has the potential to shed light on important glacial changes and how they may relate to regional warming or shifts in precipitation patterns in the North Cascades. The data could also illuminate differences in the behavior of each individual glacier. Overall the number of crevasses has declined, in 2019 average depth on Easton Glacier was 10-15 m.

Another technique we used in the field is crevasse stratigraphy. Upon looking inside open vertically-walled crevasses in the accumulation zone, there are clear layers exposed on the crevasse walls. The layers are the remaining snow from each accumulation season, with the most recent winter’s snow on top. Using a rope marked at each decimeter, we work together to measure the depth of each exposed snow layer. These measurements give a pinpointed measurement of mass balance, and thus glacial health, throughout the past couple of years.

In some open crevasse features, you can see that many more years of stratigraphy are preserved, like in this photo on Easton Glacier. Each visible layer is from a year during which the amount of snowfall exceeded the summer melt, and there is no remaining evidence from years with higher melt than snow accumulation.

Other information we can gather from crevasses is related to the internal stresses in the ice. Crevasses are opened by pull-apart forces which act perpendicular to the trend of the crevasse.

If you are able to relate the crevasse orientations to the stress within the glacier, it is useful in evaluating the dominant stresses and how they change throughout the glacier spatially. Identifying the locations of crevasse groupings is also a valuable observation, as it reveals the areas with high stress, and may give clues as to where bedrock steps exist below the glacier.

Crevasses are often perceived as scary and have a negative connotation, and while they are hazardous to glacial travelers (always be VERY careful and have the correct gear when navigating crevasses), they are actually a sign of glacial productivity. A healthy glacier’s crevasses are frequent and deep, because thick, flowing ice generates high stress conditions.

The North Cascades Glacier Climate Project has observed glacial thinning due to lower rates of snowfall paired with more intense summer melt seasons over the past 36 years. This has led to a reduction in the number of crevasses in many areas. During summer 2019, the glaciers we visited in the North Cascades will lose up to 2 meters of snow from their surfaces to melting. It is likely that as this pattern continues, there will be even less surface crevassing on the glaciers.

Retreat of West Barun Glacier and Barun Tsho expansion, Nepal 1994-2018

On September 9, 2019April 24, 2024 By mspeltoIn Himalaya glacier retreat

West Barun Glacier terminus retreat and lake expansion in 1994 and 2018 Landsat images. Red arrow is the 1994 terminus location, yellow arrow the 2018 terminus location, green arrow Seto Pohkari and purple dots the snowline.

The West Barun Glacier flows southwest from Baruntse Peak at 7100 meters ending at Lower Barun Tsho (Barun Tsho) at 4500 meters. Comparison of Landsat images from 1994, 2000, 2015 and 2019 indicate the retreat of the glacier and expansion of the lake. In the early 1990’s the lake was observed to have an area of 0.7 km² (ICIMOD, 2010). The importance of such lakes impounded in part by moraines, is the potential for glacier lake outburst floods (GLOF). The Lower Barun Tsho has no specific date for a GLOF observed. Rounce et al (2017) examined the risk posed by Lower Barun Tsho, part of which is another proglacial lake 3 km upstream, Seto Pohkari with an area of 0.41 km² and it is considered to be a high hazard as the avalanche. There are 33 buildings, 4 bridges and ~0-.8 km² of agricultural land at risk of GLOF damage below Lower Barun Tsho (Rounce et al 2017) .

In 1994 the lake is 1100 m long and has an area of ~0.6 km². By 2000 the lake was 1400 meters long and the area has increased to 0.9 km². The snowline in both 1994 and 2000 is ~5700 m. In 2009 the lake was 2000 meters long and had an area of 1.4 km²having doubled in size. By 2015 the lake is 2700 m long and has an area of ~1.6 km². Haritashya et al (2018) surveyed Lower Barun Tsho in 2015 and found a maximum depth of 205 m and a volume of 112.3 × 10⁶ m³. In 2018 the maximum length of the lake is 2800 m and the area 1.7 to 1.8 km². The snowline in 2015 and 2018 is at 6000 m, which is above the mean elevation of the glacier, indicating mass balance loss. In the 2009 Digital Globe imagery below, right half of image, the glacier is stagnant below the light green arrow. The medial moraines evident at the purple arrows indicate the area around 5700-5800 m that typically is in the ablation zone. The orange arrows indicate the outflow from Seto Pohkari. The dark green arrows indicate the wide moraine band. There is some melt out of this 1 km wide band resulting in lake expansion and pond development. The lake length and area has doubled since 2000. Glacier retreat has been 1500 m from 1994-2018. Haritashya et al (2018) expect faster growth and increasing risk from Lower Barun Tsho. The beginning of a stagnant zone below the icefall, light green arrow below, indicates rapid retreat can continue. The changes here are repeated at many glaciers in this region including Lumding, Lhonak, Yanong and Thulagi

Kirschbaum et al (2019) examined the cascade of hazard impacts that can work together to generate or accentuate geologic hazards in this regions including earthquakes, monsoon flood events, avalanches and GLOFs.

West Barun Glacier: Purple arrows indicate upper reach of lateral moraines, light green arrow the start of the stagnant zone below an icefall, orange arrows indicate the river draining the Seto Pohkari and dark green arrows indicate the partially ice cored moraine belt.

West Barun Glacier terminus retreat and lake expansion in 2000 and 2015 Landsat images. Red arrow is the 1994 terminus location, yellow arrow the 2018 terminus location, green arrow Seto Pohkari and purple dots the snowline.

Hutchinson Glacier, Greenland Releases New Island

On September 3, 2019April 24, 2024 By mspeltoIn Greenland glacier retreat1 Comment

Cape Deichmann becomes an island as it disconnects from Hutchinson Glacier. Landsat images from 2010 and 2019.

The Hutchinson (H) and Polaric Glacier (P) region of East Greenland indicating three locations of island forming or about to form in 2010 and 2019 Landsat images. Point #1 is Flado Island, Point #2 and Point #3 is Cape Deichmann

Ziaja and Ostafin (2019) noted the formation of a new island at Cape Deichmann (3) due to recession of Hutchinson Glacier (H). Here we use Landsat images from 2010-2019 to examine the release of this island and other islands and pinning points in the Hutchinson and Polaric Glacier area. This is one of a growing number of examples of glacier retreat leading to island formation.

In 2010 a tongue of Hutchinson Glacier connects to Cape Deichmann. Hutchinson Glacier also connects to five other islands along its front, helping provide stability to the ice front. Pinning points such as these islands reduce calving directly (Hill et al 2017), but also suggest limited water depth, which would reduce the impact of warm ocean water. The center of Polaric Glacier also has Island #2 that provides stability. At Flado Island (#1) the west margin of Polaric Glacier does not reach this island, but a melange of ice fills the space between the glacier front and the island, which does provide a degree of stability (Moon et al 2015). In 2012 there is no change in the Cape Deichmann or at Island #2. Flado Island has lost its melange during this summer of exceptional warmth, but an ice tongue still reaches to within 1 km of the island. In 2015 there is no change at Cape Deichmann or at Island #2. The gap between the Polaric Glacier front and Flado Island is filled by a melange again. In 2019 the Hutchinson Glacier ice tongue to Cape Deichmann is gone. The ice front is now 0.6 km from the now Deichmann Island. Island #2 is still embedded in the Polaric Glacier front. Flado Island has lost its melange in the warm summer of 2019, the central ice front of Polaric Glacier has also retreated 1.5 km, while the east and west margins changed little. This will make it more difficult to develop a persistent melange of ice between the glacier front and Flado Island. There will be new island formed in the near future in this region.