Category: Antarctic Glacier retreat

Snowcover Free Glaciers in Antarctica in 2023

On By mspeltoIn Antarctic Glacier retreat

Eastern Ice Cap on Vega Ice Cap is snow free in Feb. 19, 2023 Sentinel images. Bedrock areas at Point A and B will expand with snow free conditions.

In 2023 the near complete loss of snowcover is apparent on a number glacier and ice caps In Antarctica, on several islands along the Antarctic Peninsula. This yields a more extensive bare ice and firn surface area, that increses melt rate and increases the density of light absorbing particles on the surface.  This snowcover loss is the result not of a heat wave but of a consistenly warm summer. At Esparanza Base:

  • November mean temperature 2.5 C above average
  • December mean temperature 0.5 C above average
  • January mean temperature 1.5 C above average
  • February mean temperature 1 C above average

This yields an mean melt season temperature 1.5 C above average compared to 2020 that had a mean average temperature 0.5 C above average.  The most anomalously warm month was November. Monthly temperature anomlies for the region are evident in the global monthly maps from NCEI NOAA, see below. The net amount of melt for these temperatures is still low, which indicates the limited accumulation in the region.

On Vega Island the eastern end features an ice cap that has no retained snowcover from the north to south shore, with two expanding areas of bedrock amidst the glacier at Point A and B. Snowcover begins at 300 m on an ice cap toward center of island. On Vega Island’s western end the ice cap has lost 70% of its snowcover, with snow retained above 400 m.

On the Ulu Peninsula of James Ross Island three of five glaciers along the Lachman Crags are snowcover free. Triangular, Lachman and San Jose Glacier lack snowcover and have a much darker surface, which further enhances melting, then seen in field photographs of these glaciers (Davies, 2020) and Jennnings et al (2021). Glasser and Lachman North Glacier both have significant snowcover above 500 m.

Whisky Glacier is a tidewater glacier terminating in Whisky Bay. This glacier is 90% snowcover free on Feb. 19, 2023. Snow patches are evident above 250 m near the ice divide, note green arrow. The southwest extension (SW) is also snow free.

As reported separately, Eagle Island Ice Cap in Sentinel image from Feb. 19, 2023 has only small patches of snowcover left, 5-10% of ice cap all above 300 m. The peripheral ice caps and glaciers here are not an indicator of the larger ice sheets. They are an indicator that snowcover free glaciers are now occurring not just at temperate latitudes. These glaciers like many glaciers in the Central Andes of Chile and Argentina have lost nearly all their snowcover.

 

A series of glaciers on the Ulu Peninsula of James Ross Island Feb. 19, 2023 Sentinel images. San Jose, Lachman and Triangular have lost all snowcover and have a low albedo. Glasser and Lachman North Glacier have snowcover above 500 m.

Whisky Glacier on the Ulu Peninsula of James Ross Island Feb. 19, 2023 Sentinel image, illustrating 90% of the snowcover has been lost, green arrow is ice divide.

Western Vega Island Ice Cap in Feb. 19, 2023 imnage is 70% snowcover free with snow along summit area above 400 m.

Eagle Island Ice Cap in Sentinel image from Feb. 19, 2023 illustrating only small patches of snowcover left, 5-10% of ice cap. 

NCEI NOAA Monthly Global temperature anomalies.

 

Eagle Island Ice Cap, Antarctica Loses its Snowcover in 2023

On By mspeltoIn Antarctic Glacier retreat, Uncategorized

Screenshot

Eagle Island Ice Cap in Sentinel image from Feb. 19, 2023 illustrating only small patches of snowcover left, 5-10% of ice cap. 

On February 19, 2023 Eagle Island Ice Cap, Antarctica has less than 10% snowcover. This is less snowcover than observed even after the period of record warm weather over the Antarctic Peninsula in February 2020.  Temperature when the all time Antaractica temperature record was set at Esperenza Base. That year also led to record melt and ponding on the George VI Ice Shelf  (Banwell et al, 2021). Here we examine Landsat and Sentinel imagery of the Eagle Island Ice Cap (63.65 S 55.50W), 40 km from Esperanza, to identify surface melt extent and surface melt feature development in 2020, 2022 and 2023. The summit of the ice cap is at 250-300 m and it has an area of 21 km².

In 2020 we observed blue ice areas (BI) and saturated snow areas (SS) rapidly developed from a snow covered ice cap during the heat wave (NASA EO, 2020). The impact of short term melt events like this on an ice cap like this, is visible and significant for annual mass balance, but not large in terms of long term glacier mass balance (volume change) and area. In 2022 a similar patter nof blue ice developed, but no saturated snow. In 2023 the loss of snowcover is nearly completely yielding a more extensive bare ice and firn surface area. This is the result not of a heat wave but of a consistenly warm summer. At Esparanze Base:

  • November mean temperature 2.5 C above average
  • December mean temperature 0.5 C above average
  • January mean temperature 1.5 C above average
  • February mean temperature 1 C above average

This yields an mean melt season temperature 1.5 C above average compared to 2020 that had a mean average temperature 0.5 C above average.  The most anomalously warm month was November. This led to a mostly snow free ice cap by January 10. The ice cap then experienced a month of mostly snow free conditions with the darker ice melting more rapidly then the snow would. This in particular will lead to marginal retreat of the ie cap along bare rock margins.

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Eagle Island Ice Cap in Sentinel image from Jan. 10, 2023 illustrating only 15-20% snowcover left.

eagle-2-2020

Eagle Island Ice Cap, Antarctica in Landsat images from Feb. 4, 2020 and Feb. 13, 2020.  Point E indicates an are area of snow/firn that is saturated with meltwater. Point A and B indicate locations where the amount of bare rock/ground and hence albedo have changed dramatically. 

King George Bay, Antarctica Glacier Retreat Expands Turret Point Oasis and Releases New Island

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King George Bay Glacier retreat releases a new island (Point B) and expanded ice free oases in 1989 and 2022 Landat Images. Point A marks an area where the glacier had reached the coast until after 2005. Point B is the new island, Point C= new oasis, PI=Penguin Island, TP=Turret Point Oasis

King George Bay is on the southeast coast of King George Island. This coastline is comprised mainly of glacier margins ending in th sea, with limited ice free areas. The east end of the bay features the Turret Point Oasis, with Penguin Island just offshore. This oasis is a location used for breeding by Chinstrap and Adelie Penguins, and is a significant breeding area is for southern giant petrels, and Antarctic ‘blue-eyed’ shags. Elephant seals and fur seals are numerous in the latter part of the season (Korczak-Abshire,et al 2018). Here we examine Landsat images from 1989-2022 to identify changes in the glacier margin and the impact on this oasis and generation of a new island.

King George Bay Glacier retreat releases new island in Sentinel images from 2018 and 2022. Point A marks an area where the glacier had reached the coast until after 2005. Point B is the new island, Penguin Island=PI, TP=Turret Point, Point C is the new oasis.

In 1989 the Turret Point Oasis had an area of ~1 km². The King George Bay Glacier terminated on a bedrock rise at Point B. The glacier reached the coast between Turret Point and Point A. To the west there is no other ice free coastline, Point C. In 2005 the glacier was still terminating on the bedrock rise at Point B. The glacier is still reaching the coast between Point A and Turret Point and there is no ice free area near Point C. By 2018 there is a narrow finger of ice connecting to the Point B Bedrock rise and the shoreline between Turret Point and Point A is now free of glacier.  there is a small strip of ice free coast near Point C. In 2022 the glacier has receded from the new island at Point B. The retreat at Point B is 950-1000 m since 1989, with a similar retreat across the broad front of the King George Bay Glacier to Point C.  Glacier retreat from the shoreline near Point A has been 400 m. The Turret Point Oasis has expanded to 2 km², a doubling in size that expands oppportunity for greater diversity of flora and fauna.  There is a new ~0.6 km² oasis that has formed at Point C.  This is a narrow 200-400 m wide strip that is 1.7 km long. In the false color Sentinel images red indicates plant life for 12-24-2022 the Point C oasis does not have enough flora to be visible. This is in contrast to Turret Point and Penguin Island. The retreat here fits the pattern seen further west on King George Island on the Warsaw Ice Cap.

In 2016 the Arctwoski Station research survey found ~150 pairs of breeding Adlelie Penguins and 220 breeding pairs of southern giant petrels (Korczak-Abshire,et al 2018). In the Antarctic Treaty Turret Point oasis has specific visitor guidelines.  The confluence of threats from climate change and human activity (Lee et al, 2022) makes Turret Point an important location to monitor. The retreat of glaciers opening up new potential breeding and feeding areas has been observed at Stephenson Lagoon on Heard Island and at Hindle Glacier on South Georgia.

Map illustrating  locations bird and penguin species onTurret Point and Penguin Island from a UAV flight in 2016 from Korczak-Abshire,et al (2018)

King George Bay Glacier false color Sentinel image. Vegetation is evident on Turret Point=TP and Penguin Island=PI, but not at Poiunt C oasis.

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

Talking about Iceberg Melt Rates and Glacier Frontal Ablation: Seller and Heim Glacier, Antarctica

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Figure 1: Study sites considered in this article: Seller Glacier and Heim Glacier (Landsat-8 image courtesy of the U.S. Geological Survey)

Post by Mariama Dryak

Iceberg melt is caused by the temperature of the water in which an iceberg floats and the velocity of the water flowing around the iceberg. As a result, iceberg melt is an excellent indicator for the ocean conditions in which an iceberg resides. Given the remote location of Antarctica, and the difficulty in taking direct oceanographic measurements immediately in front of glacier termini in Antarctica, icebergs near glacier fronts can act as a useful proxy for what the ocean conditions are in these areas, especially under changing climate.

Dryak and Enderlin (2020) compared remotely-sensed iceberg melt rates (2013 – 2019) from eight study sites along the Antarctic Peninsula (AP) to glacier frontal ablation rates (2014 – 2018) where they overlapped in time and found a significant positively correlated relationship between the two. In general, iceberg melt rates were found to be much lower on the eastern AP where ocean waters are characterized as very cool relative to the heterogeneous, but generally warmer, waters on the western AP–where iceberg melt rates were higher. When we take a closer look at the data and consider what this means in the context of a stratified water column, the iceberg melt rate magnitudes also make sense relative to one another and what is known of regional ocean conditions.

Here we take a look at the results from two of those study sites: Seller Glacier and Heim Glacier.

Seller Glacier is the southernmost study site considered in our study on the Antarctic Peninsula, and produces very large, sometimes tabular icebergs with relatively high mean melt rates. Figure 2 indicates the changes in the same iceberg at two points in time. These icebergs are larger than and different in style to all of the other study sites, with the Seller Glacier terminus also being the widest of all the glaciers considered in the study. Due to the large area of the icebergs produced, we know that the keel depths of these icebergs also extend deep into the water column (See Table 1, Dryak and Enderlin, 2020), contacting warm subsurface waters (and some contacting Circumpolar Deep Water (CDW)) as characterized by Moffat and Meredith (2018) in Figure 3 below. In the upper layers these icebergs also sit in the very cold Winter Water (WW) layer and expanded section of Antarctic Surface Water (AASW) prevalent in the Seller region.

Figure 2: An iceberg from Seller Glacier in 2014 and later in 2016. Mean submarine melt rates for the Seller Glacier icebergs from this time period were 6.54 cm/day (Imagery © [2019] DigitalGlobe, Inc.)

Figure 3: Figure 3 from Moffat and Meredith (2018).

Frontal ablation rates at Seller Glacier are higher than expected given iceberg melt rates at the other sites on the western Antarctic Peninsula (Figure 4). Dryak and Enderlin (2020) suggest this to be because of a long-term dynamic adjustment of the Seller Glacier in response to the collapse of the Wordie Ice Shelf, which occurred between 1966 and 1989 (Vaughan, 1991)-a similar case to the sustained elevated velocities witnessed at Crane Glacier on the eastern Antarctic Peninsula following the collapse of the Larsen B Ice Shelf in 2002.

 

Figure 4:     Scatterplot of iceberg melt rates and frontal ablation  for nearby glaciers over near-coindicdent time periods. Symbols indicate median frontal ablation rates. Figure 8 from Dryak and Enderlin (2020)

In contrast, the study site at Heim Glacier, north of Seller Glacier, contains smaller, shallow icebergs with low iceberg melt rates on par with iceberg melt rates found on the eastern Antarctic Peninsula. The glacier that produced the sampled icebergs, though not the smallest of the sites sampled, produces icebergs small in area that often do not last from one season to the next. The keel depths of the sampled icebergs at Heim Glacier likely do not reach below the cold WW layer (Table 1, Dryak and Enderlin, 2020), terminating in the very cold water layer or above in the compressed and comparatively cool AASW. However, the Heim study site is also located near the Marguerite Trough, an area of deep bathymetry known for the presence of warm waters, so the low melt rates here may be surprising to some without taking a closer look at the specific locale. Our study suggests that the bathymetry of the area in which the icebergs reside might be sheltered due to the presence of Blaiklock and Pourquoi Pas Islands, which may deflect warmer waters from reaching the Heim Glacier.

Frontal ablation rates at Heim Glacier are low, and of a similar magnitude to eastern Antarctic Peninsula sites, corresponding in magnitude to the low iceberg melt rates for the site as well (Dryak and Enderlin, 2020; Figure 8).

Overall, this paper re-emphasizes the importance of considering the ocean’s role in forcing changes on glaciers that terminate in the ocean around Antarctica, especially under changing climate. With the ocean acting as a large sink for excess heat in the atmosphere, evaluating the consequences of the storage of this heat in the ocean is essential when attempting to understand the feedback mechanisms associated with such change. The moral of the story is that we must keep one eye on the ocean going forward and how it could lead to changes in glacier dynamics, which could lead to changes in the contributions of glaciers to sea level and the marine ecosystems that exist within the ocean.

For full results and discussion of all of the study sites considered along the western and eastern sides of the Antarctic Peninsula, read the full Dryak and Enderlin (2020) article in the Journal of Glaciology.

*Note the Seller Glacier like many others in the region have experience rapid retreat in the last 30 years, Fleming Glacier, Sjogren Glacier and Boydell Glacier.

Huron Glacier Retreat, Livingston Island, Antarctica 2001-2020

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Huron Glacier (H) and Kaliakra Glacier (K) in 2001 and 2020 Landsat images.  Extensive retreat at bedrock locations Point A and B with limited retreat at C and D.

Livingston Island, Antarctica is part of the South Shetland Island chain and is primarily covered by glaciers.  At the eastern end is Huron Glacier. Huron Glacier and the adjacent Kaliakra Glacier are tidewater outlet glaciers terminating in Moon Bay on the east end of Livingston Island. Molina et al (2007) noted that persistent warming had led to mass loss  from 1956-2000 on Johnson and Hurd Glacier further west on the island. Osmanoglu et al (2014) observed the velocity and frontal ablation rates of Livingston Island glaciers.  Frontal ablation includes losses from calving and surface melting of the ice face from contact with the ocean and air.  They observed that frontal ablation losses were the same magnitude as surface ablation. Huron Glacier had the highest frontal ablation by a significant amount from 2007-2011 and the higest location of velocity at 250 m/year.  Here we examine Landsat images from the 2001-2020 period to illustrate the retreat of the glacier fronts in Moon Bay.

In 2001 the icefront is 3 km beyond Point A a bedrock knob at the end of a ridge, 3.5 km beyond Point B also bedrock at the end of a ridge, 1800 m beyond Point C and 1500 m beyond Point D.  Snowcover extends to the ice front.  In 2004 there is not a significant change in the ice front position and snowcover again extends to the ice front.  By 2015 the ice front has retreated to within 1 km of Point A. In March 2018 there is evident ablation in the lowest reaches of Huron Glacier.  In February 2020 the ice front has retreated to the bedrock knob at Point A , a 3000 m retreat since 2004. The ice front is 2 km from the bedrock ridge at Point B, a 1500 m retreat since 2004. The ice front retreat on the north side of Kaliakra at Point C has retreated 400 m since 2004.  Retreat on the south margin of Huron Glacier at Point D has retreated 500 m.  Surface melting is also evident in 2020 from Point B to the ice front, with a lateral moraine exposed as was the case in 2018. The 2020 melt season featured record high temperatures in this region of Antarctica leading to high surface melt, such as at Eagle Island Ice Cap.  Surface melt on Livingston Island is less extensive than on the Warsaw Icefield on King George Island  (Petlicki et al, 2017). Retreat of Huron Glacier has been more rapid than on other glacier fronts on Livingston Island this is reflective of the higher frontal ablation rate, which is significantly due to its high velocity.  Osmanoglu et al (2014) note a significant summer velocity increase on Livingston Island glaciers, will increased melt enhance basal water pressure and velocity or lead to a more mature drainage reducing basal water pressure limiting summer velocity increases? The retreat of the calving front is similar to that of Endurance Glacier on Elephant Island.

Huron Glacier (H) and Kaliakra Glacier (K) in 2004 Landsat image and 2015 Landsat image based contour map from Antarctic REMA Explorer.  

Huron Glacier (H) and Kaliakra Glacier (K) in 2018 Landsat image portrayed in Antarctic REMA, note surface melt and lateral moraine material near Point A and B.

Boydell Glacier Accumulation Zone Rapid Melt Feature Development February 2020

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Boydell Glacier terminates at the island adjacent to Point A.  The accumulation zone between Point A, B and C is on January 12, 2020 has limited gray area indicating bare firn.  By Feb. 13 there is considerable cobalt blue snow/firn areas saturated with melt water. The yellow dots mark the margin of the ice sheet and pink dots the margin of the ablation zone on Feb. 13, 2020. 

The Boydell Glacier, Antarctic Peninsula is fed in part by a plateau to its north.  Boydell Glacier has experienced a substantial retreat of 6.5 km from 2001-2017 and in 1990 was part of the Prince Gustav Ice shelf that has disintegrated (Cook and Vaughan, 2010). Antarctic temperature records were set at Esperenza and Marambio Base. in early February 2020.  Here we examine the  impact of period of record warm weather over the Antarctic Peninsula on a portion of the Boydell Glacier’s accumulation zone north of its terminus (64.1 S 58.9 W), ~100 km from Esperanza, using Landsat images from January 12-February 13, 2020 to identify surface melt extent and surface melt feature development. A.

Xavier Fettweis, University of Liege Belgium, using the MAR climate model output forced by the Global Forecast System (GFS) to generate daily melt maps for Antarctica, for Esperanza the melt map for recent weeks, shown below indicates that daily melt increased to above 30 mm/day, with a maximum temperature on the warmest day of 18.3 C (65 F). On the Boydell Glacier accumulation plateau  is dominated by surface snowpack on January 12, 2020.  On Feb. 13, 2020 significant cobalt blue snow/firn melt water saturated zones have developed in the accumulation zone covering 4 km2 and in a few localities in the ablation zone. This melt water will likely refreeze in the firn/snowpack of the accumulation zone and not be lost from the system, whereas melt in the ablation zone near Point A and Point D would be quickly lost from the system.  The ablation zone is denoted by pink dots for Feb. 13, 2020..

The Boydell Glacier accumulation zone in 207 and 2018 lacks any melt water saturation features.

The accumulation zone in REMA Antarctica image indicating surface contours at 100 m intervals.

Meltwater production time series at Esperanza Base from MAR-GFS From Xavier Fettweis. 

 

Record Antarctic Temperatures in Feb. 2020 Impact on Eagle Island Ice Cap

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Eagle Island Ice Cap, Antarctica in Landsat images from Feb. 4, 2020 and Feb. 13, 2020.  Point E indicates an are area of snow/firn that is saturated with meltwater. Point A and B indicate locations where the amount of bare rock/ground and hence albedo have changed dramatically.
This post was source for an article by Kasha Patel published by NASA Earth Observatory, CNN and Washington Post.

Update in December 2022 snowcover is less extensive than observed in 2020 or 2021.

The impact of period of record warm weather over the Antarctic Peninsula has been the rapid development of melt features on some of the glaciers near the tip of the Peninsula, where the temperature records were set at Esperenza and Marambio Base. Here we examine Landsat imagery of the Eagle Island Ice Cap (63.65 S 55.50W), 40 km from Esperanza, from January 12-February 13, 2020 to identify surface melt extent and surface melt feature development. Xavier Fettweis, University of Liege Belgium, using the MAR climate model output forced by the Global Forecast System (GFS) to generate daily melt maps for Antarctica, for Esperanza the melt map for recent weeks, shown below indicates that daily melt increased to above 30 mm/day, with a maximum temperature on the warmest day of 18.3 C (65 F). This compares to melt rates seen on the warmest days on temperate glaciers, such as the North Cascade Range, Washington of 80 mm/day and averaging 24 mm/day for the warmest months (Pelto, 2018).  This short term weather event fits into the pattern of overall regional warming that has led to a rapid glaciological response, with 87% of glaciers around the Antarctic Peninsula receding Davies et al (2012). The event regionally was examined by Robinson et al (2020),who noted implications for flora.

On January 12, 2020 Landsat imagery indicates a substantial area of bare ice/firn (gray-blue) on the western outlet glacier near Point A.  The brighter electric blue color indicates accumulated snow from the most recent winter season, this covers 60% of the ice cap.  The Jan. 27 image shows little change in the snowcover extent or the extent of older firn and ice exposed by melt.  The Feb. 4, 2020 image indicates a new snowfall has covered the ice cap. The precipitation graph provided by Xavier Fettweis indicates two snow events between Jan. 28 and Feb. 4 of approximately 5 mm water equivalent each.  The warm temperatures began on Feb 5 and continued up to the date of the Landsat image on Feb. 13. At Point E is a ~1.5 km2 area of cobalt blue that indicates snow/firn pack that is saturated with meltwater that has quickly developed.  There is an additional ring of saturated snow/firn northeast of Point E.  The snow swamp that has developed is due to the combination of melt, a total of 106 mm by Xavier’s model from Feb.6-Feb.11 and a rain event that occurred on Feb. 12 of ~6 mm. Peak melt reached 30 mm on Feb.6 similar to that at Esperanza. Point E is at the summit of the icecap between 250 and 300 m elevation. The area of bare ice (blue-gray) has expanded at Point A and Point B.  This higher albedo will enhance ablation in the near future before new snowfall covers the ice cap again.  The bedrock area near Point B has also expanded merging a couple of isolated bedrock knobs.

The impact of short term melt events like this on an ice cap like this, is visible and significant for annual mass balance, but not large in terms of long term glacier mass balance (volume change) and area.  The accumulation rate on nearby James Ross Island is ~600 mm/year.  Hence, this one melt event represents the loss of ~20% of the seasonal accumulation (Abram et al. 2011).  In Antarctica specific anomalously warm days are when most mass balance losses occur. Barrand et al (2013) note a strong positive and significant trend in melt conditions in the region.The increasing frequency and cumulative impact of events like this is significant to mass balance. Mass balance regionally has been negative driving retreat and ice shelf disintegration as noted at nearby Mondor Glacier, Muller Ice Shelf and Eyrie Bay.

Eagle Island Ice Cap, Antarctica in Landsat images from Jan. 12, 2020 and Jan. 27, 2020.  Point E indicates the top of the ice cap and it is an area of snowcover. Point A is adjacent to outlet glacier that has bare ice exposed. Point B is above a fringing area of bare firn and ice at the southern margin of the ice cap and island.

Meltwater production time series at Esperanza Base from MAR-GFS From Xavier Fettweis. 

Meltwater production time series at Eagle Island from MAR-GFS From Xavier Fettweis. 

Precipitation time series at Eagle Island from MAR-GFS From Xavier Fettweis. 

Eagle Island in Antarctica REMA viewer from Feb. 2017 indicating the snocovered ice cap with some melt area near the outlet glacier to the northwest and on the southern margin. the right hand image is the DEM of the area contoured in 25 m intervals With summit area of the ice cap above 250 m.

Eyrie Bay, Antarctic Peninsula Retreat 2000-2020

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From REMA Landsat images from Feb. 2016 and Oct. 2019 indicating the front of the Cugnot Ice Piedmont (CP)  and Broad Valley (BV) ice fronts in Eyrie Bay.  Point A, B, and C indicate specific bedrock knobs near the ice front.  Point D is just south of a side glacier entering the bay.

Eyrie Bay is near the tip of the Antarctic Peninsula and is rimmed by tidewater glaciers including the Cugnot Ice Piedmont.  The changes of the ice front fed by the Cugnot and from Broad Valley were mapped by Ferrigno et al (2008)   They noted a retreat from 1956-1977 averaging 36 m/year from 1977-1988 a retreat of 12 m/year, and 6 m/year from 1988-2000. Here we examine Landsat imagery from 2000-2020 to identify changes of the two glacier fronts. The continued significant warming air temperatures on the Antarctic Peninsula have increased surface ablation in the region (Barrand et al 2013), with 87% of glaciers around the Antarctic Peninsula now receding Davies et al (2012) . The most dramatic response has been the collapse of several ice shelves, Jones, Prince Gustav, Wordie, Larsen A and Larsen B. The  nearby Prince Gustav Ice Shelf connecting James Ross Island to the Trinity Peninsula collapsed after 1995 (Glasser et al 2011).

In 2000  the Broad Valley terminus (BV) extended 500 m beyond bedrock knob at Point A and 1400 m eastward beyond the bedrock knobPoint B. The Cugnot Ice Piedmont terminus (CP) extended from the northern tip of the bedrock knob at Point C. In 2016 the BV terminus in Eyrie Bay was 600 m east of the Point A bedrock knob and 1200 m east of the Point B bedrock knob.  By October 2019 the BV ice front had retreated to the bedrock knob at Point B and terminated near the western end of the bedrock knob at Point A, with just a narrow band of fringing ice around Point A. At Point C a small embayment has developed along the west margin of the CP terminus and the embayment near Point D has become wider and move concave.

The surface slope upglacier of the BV terminus rises quickly indicating a rising bedrock topography too, which should slow retreat in the near future.  The CP terminus has a gradual even slope suggesting there will be continued retreat. The retreat of glaciers in this region has been attributed to both atmospheric warming in the region driving surface melt increases , and in some cases increasing ocean temperatures and ice shelf bottom melting (Barrand et al 2013; Davies et al 2014).

Landsat images from 2000 and 2020 indicating the front of the Cugnot Piedmont (CP)  and Broad Valley (BV) ice fronts in Eyrie Bay.  Point A, B, and C indicate specific bedrock knobs near the ice front.  Point D is just south of a side glacier entering the bay.

From REMA Antarctica contour of Broad Valley (BV) and  Cugnot Ice Piedmont (CP), contour interval is 25 m.

Ongoing Evolution of Fleming Glacier, Antarctica

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

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

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

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

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

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

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

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

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

 

Boydell Glacier, Antarctica Rapid Retreat 2001-2017

On By mspeltoIn Antarctic Glacier retreat1 Comment

Boydell Glacier, Antarctica retreat in Landsat images from 2001 and 2017,  terminus in 2001 at red dots in 2017 at yellow dots.  A-E are reference points. 

Boydell Glacier flows east from the northern Antarctic Peninsula and prior to the 1980’s was joined with the Sjogren Glacier as a principal feeder glacier to Prince Gustav Ice Shelf.  This 1600 square kilometer ice shelf connecting the Peninsula to James Ross Island disintegrated in the mid-1990’s and was gone by 1995 (Cook and Vaughan, 2010).  Scambos et al (2014) noted a widespread thinning and retreat of Northern Antarctic Peninsula glaciers with the greatest changes where ice shelf collapse had occurred, Boydell/Sjogren Glacier being one of the locations.  A new paper by Seehaus et al (2016)  focuses on long term velocity change at Sjögren Glacier as it retreated.  This study illustrates the acceleration after 1996 from 0.7 m/day to 2.0 m/day in  2003 and then after separation Boydell Glacier, which is slower, has declined from  a velocity of 1.6 m/day in 2007 to  a velocity of 1.0 km day in 2015. Here we examine Landsat images from 1990, 2001, 2005 and 2017 to illustrate changes in terminus position of Boydell Glacier.

In the 1990 Landsat image Boydell/Sjögren Glacier feed directly into the Prince Gustav ice Shelf which then By 1993 Seehaus et al (2016) note that Boydell/Sjögren Glacier had retreated to the mouth of Sjögren Inlet in 1993, this is marked Point A on Landsat Images. By 2001 the glacier had retreated to Point B,  a distance of 7 km.  Between 2001 and 2005  a 2.5 km ot 3 km retreat led to a separation of Boydell Glacier and Sjogren Glacier and a retreat to Point C.  In 2017, Boydell Glacier has retreated 6.5 km since 2001.  This is less then the  Sjögren Glacier retreat of 10-11 km from the 2001 location.   Seehaus et al (2016) Figure 1  indicates that the area of high velocity over 1.0 m/day on Boydell Glacier in the last decade extends the entire 12 km length of the valley reach, which is fed by an icefall from a higher plateau region. The high velocity and limited change in fjord width in the lower 6 km indicates there is not a new pinning point to slow retreat appreciably in this stretch. Figure 1 also illustrates the retreat from 1993-2014. The pattern of ice shelf loss and glacier retreat after loss has also played out at Jones Ice Shelf and Rohss Bay.

sjogren glacier 1990

1990 Landsat Image of Boydell/Sjogren Glacier and Prince Gustav Ice Shelf, terminus marked by red dots.

2005 Landsat Image of Boydell/Sjogren Glacier terminus marked by red dots.

Antarctic REMA Explorer view of Boydell (B)  and Sjogren (S) in 2002.

Cape Longing, Antarctica Transitioning to Island via Glacier Retreat

On By mspeltoIn Antarctic Glacier retreat

Cape Longing, Antarctica in 2001 and 2018 Landsat images. Point A-G are at specific locations. Yellow dots mark the margin of the glacier connecting the Cape to the main Antarctic Peninsula.

Cape Longing is on the Antarctic Peninsula between Larsen Inlet and Prince Gustav Channel.  Larsen Inlet along the south shore of Cape Longing was covered by the Larsen A Ice Shelf until its collapse in 1995. The Prince Gustav Ice Shelf extended across the channel from the north shore of Cape Longing until the 1980’s.  This 1600 square kilometer ice shelf disintegrated in the mid-1990’s and was gone by 1995 (Cook and Vaughan, 2010).   Here we examine changes in the glacier connecting Cape Longing to the Antarctic Peninsula from 2000 to 2018 using Landsat imagery.

In 2000 the glacier connecting Cape Longing with the main peninsula extended along a front from Point F to Point E. Northeast of Point G there is an area of rifted ice indicative of ice that had been grounded going afloat. On the southern margin the ice front extends southwest from Point A.  The glacier from the northern to the southern margin is ~9 km across.  In 2001 the southern margin has not changed, but the northern margin indicates an expanded ice melange between the active glacier and the ice front, making the exact terminus difficult to pinpoint.  By 2017 the northern ice margin has retreated to a line between Point B and Point G.  The southern margin extends west from Point A.  In 2018 it is 3.5 km from the northern to southern margin, more than 60% of this glacier connection to Cape Longing has been lost since 2000.  This connection appears to have a below sea level bed though the glacier is grounded.  This grounding should lead to a slower retreat. The ice shelf/glacier retreat at Cape Longing is significant though much less than the more dynamic nearby Sjogren Glacier.

View of Cape Longing in REMA Antarctic Explorer, which is the 2000 Landsat image.

Cape Longing, Antarctica in 2000 and 2017 Landsat images. Point A-G are at specific locations. Yellow dots mark the margin of the glacier connecting the Cape to the main Antarctic Peninsula.