Italy’s mountains have been experiencing a warm summer, rivaling their warmest summer in the last couple of centuries, 2003. The impact on the glaciers will be considerable melting. Here we look at the retreat of the Sabbione Glacier. The glacier drains into Lago Sabbione an artificial lake that in turn drains into Lago Morasco, which is a 29MW hydropower facility. The lake also has good fishing. This glacier in 1988 reached the shore of Lago Sabbione.
In a series of Landsat images from 1988, 2006 and 2010 and a picture from Lago Sabbione in 2007, the retreat from the lake is evident. Tthe 1988 terminus is indicated by a red arrow, the 2010 terminus by a yellow arrow, the new outcrop in the midst of the glacier by a magenta arrow and the outcrop that has reached the margin of the glacier in 2010 a green arrow. The retreat during this period has been 450 meters. of greater concern for the future of the glacier is the emergence of rock outcrops in the midst of the middle portion of the glacier, and smaller ones on the upper glacier. This indicates a glacier that is not in equilibrium lacks a persistent accumulation zone, indicating it will not survive current climate.
The retreat is similar to the losses experienced across Italy from the smaller Dosde Glacier, the larger Forni Glacier and the Presena Glacier, ski area. On the latter on Aug. 12, 2012 from the ski area webcam you can see the attempts to use blankets, grooming and snowmaking to supplement the glacier, which off the ski run is bare ice.
The 2011/12 winter was a La Nina winter that led to the typical La Nina excellent snowpack. By May 1 the 2012 snowpack was one of the top five snowpacks of the last 30 years. After an average May and a cool June, the snowpack was still high on July 1. July and August tied 1998 and 2009 as the warmest over the last 30 years in the North Cascades, leading to rapid glacier melt. The result with four to six weeks left in the melt season is that glaciers are going to finish the year with a mix of glaciers that gained and lost mass despite the good winter. The duration and intensity of melt if sustained above average will leave most glaciers with a loss.
We started on Columbia Glacier, a low elevation cirque glacier fed by tremendous avalanching, that had received considerable snow accumulation from avalanching off the slopes of Columbia Peak. Our measurements found an average snowpack of 4.2 meters at the start of August. The glacier lost 9 feet of snow pack during the month of August. The glacier will likely finish the season with a small positive balance, unless September is significantly above average in temperature.
We were joined by Oliver Grah, Nooksack Indian Tribe Water Resource Manager in assessing Rainbow and Sholes Glacier. Average melt and runoff was 11 cm/day from Sholes Glacier. On Rainbow Glacier snowpack was well above average on the lower half of the glacier below 1600 meters, but had very little increase with elevation and only average accumulation at the top of icefall at 1800-2000 m. The Rainbow Glacier will likely have a positive mass balance. Sholes Glacier had an an average snowpack of 3.5 m in early August, and 1.5 meters by the end of August. This will likely lead to a close to equilibrium balance.
On Lower Curtis Glacier the south facing terminus does not retain snowpack well, and is more sensitive to summer conditions. As a result the high ablation of July and August had led to rapid melt of the terminus seracs and icefall. We were able to get beneath the glacier, where the rapid melting has led to the glacier being off its base in many areas. The glacier will finish the year with negative mass balance, regardless of September weather.
The next stop was Easton Glacier where Oliver Grah, his assistant Jezra Beaulieu, Western Washington U., Peter Sinclair videographer joined us. The lower kilometer of the glacier was mostly blue ice already by August 12. By the end of August little snowpack remained below the 2000 meter bench. This glacier does not receive avalanching and again is more susceptible to summer conditions. Like Lower Curtis Glacier this glacier will finish the season with a negative mass balance. Snowpack remaining rose from 3.2 m at 2000 m to 5.7 meters at 2500 meters in mid-August. A detailed survey of crevasse with, length and depth that will be repeated will hopefully be able to identify glacier velocity changes going forward.
On Mount Daniels we examined Ice Worm Glacier, Daniels and Lynch Glacier. The snowpack on these glacier the furthest south and east that we observe was the best of anywhere. Ice Worm Glacier is an avalanche fed small cirque glacier that had excellent snowpack. Daniels Glacier for the first time since 1999 was fully snowcovered even on August 16th. Lynch Glacier had good snowpack as well with the blue ice area limited to less than 10% of the glacier. All three of these glaciers will finish the year with a positive mass balance.
Mauri Pelto, Tom Hammond, Ben Pelto and Jill Pelto
2013 from June 17 Landsat image, yellow dots are icebergs generated in 2012, purple dots terminus, red arrow a rift that will lead to another significant calving event this summer, below this is compared to other images, including from late last summer, when more rifts existed that yielded the icebergs now dotted.
In an article Dan Bailey and I published at Skeptical Science, we observed that in northern Greenland high velocities extend far inland only on Zachariae and Petermann Glacier tapping into the midst of the ice sheet in northern Greenland. Further, it is the Zachariae Isstrøm (ZIS) that is likely the only of this group that would be comparable to a bank that is too big to fail as its increased velocity band extends well into the ice sheet. ZIS is one of the three main outlets of the northeast Greenland Ice Stream, Storstrommen and Nioghalvfjerdsfjorden (79N) are the other two. The extent of the high velocity zone is evident in the first image below from the exceptionally detailed work of Joughin et al (2010), and Joughin et al (2001). The area of high velocity versus the surrounding ice at over 100 m/year extends 350 km upglacier from the ZIS terminus. The velocity then increased from 100 to 400+ m/year from 200-100 km from the ice front. At the grounding line the velocity is 1100 m/year (Rignot et al, 2001). The velocity remains high to the ZIS icefront. The width of the ice stream identified by the zone of higher flow is 40 km wide 350 km above the terminus and remains at least 30 km wide all the way to the terminus region. The velocity is lower than on Jakobshavns, but the ice stream is also much wider.
A view of the basal topography from Joughin et al (2001) indicates that the acceleration occurs in the same area as the bed depth drops significantly below sea level 200 km from the ice front. The base of the glacier is 300-700 meters below sea level all the way to the ice front. The thickness at the grounding line is noted as 550-600 meters by Rignot et al (2001). The result is an ice flux at the grounding line of ZIS of some 11 cubic kilometers per year, this is much less than the 40+ cubic kilometers from Jakobshavn Isbrae and similar to the 12 cubic kilometers from Petermann Glacier. The red arrows in both images indicates the area of fast ice, discussed below and the yellow arrow the location of the new 2012 ice front.
This post examines recent changes in ZIS updating the work of Box and Decker (2011). They noted an average decadal rate of loss of 14 square kilometers/year and the evolving terminus position in the first image below from Jason Box at Meltfactor.org. Box and Decker (2011) also noted a potential advance in 2006-2007, that we will further explore here. The reduced sea ice in the region has exposed the ZIS terminus to increased open water in what was typically a region that was dominated by persistent sea ice. The enhanced surface melting is also a concern. In 2012 ZIS has experienced an additional retreat that has separated the main glacier from a melange of glacier ice and fast sea ice on the northeast side of the terminus, that had survived the last major tongue disintegration of the southern floating arm of ZIS in 2000-2001. The changes have been an going watch by several of the participants at the Arctic Sea Ice blog, which has developed into a wonderful community for daily detailed sea ice observations. Espen Olesen and I have discussed the split that occurred this August which warrants pointing out and. Here we examine Landsat imagery from 2006, 2008, 2009 and 2010 and MODIS imagery from 2011 and Aug. 19 2012 to depict the changes. The last image is a July 30 2012 Landsat with the purple terminus line indicated. The images are shown below with the fast ice zone (FI) noted in 2006 and the MODIS images from 2011 and 2012. The new 2012 terminus that has retreated to the corner of Lambert land, or Kap Zacharaiae is indicated by a yellow arrow, this is Kap Zachariae, and is separate from the ice to the northeast. The actual terminus in the Landsat images is indicated by purple dots, but based on the melange that exists on the east side and fast ice on the north side this is not a clear cut distinction. The fast ice is distorted in a convex pattern by the impinging ice front in the Landsat images. The new terminus is at the southeast corner of Lambert land and extends directly southwest to Heretugen Land and then Norreland
2006 Landsat image
2008 Landsat image
2009 Landsat image
2010 Landsat image
2011 MODIS image
2012 MODIS image
2012 Landsat image 2013 from June 17 Landsat image, yellow dots are icebergs, purple dots terminus, red arrow a rift that will lead to another significant calving event this summer.
The retreat follows the calving events on Petermann and Steesnby Glacier. Here there is no single large iceberg to observe. The retreat from 2010 to 2012 is approximately 10 km, the loss of area is particularly hard to accurately determine. Overlaying the 2006 and 2012 images I estimate the loss at 170 km2. The ice margin in 2000-2001 is even harder to accurately depict. Most maps and analysis to date have included much of the fast sea ice as part of the glacier. The fast ice has a velocity unconformity with the main ice and a profile that is not consistent with it being connected to ZIS. Whether it is fast sea ice or a combination of relict ice from ZIS and fast ice is unclear. Here based on the same assessment as used for the other years the retreat from 2001-2012 amount to the loss of 600 km2, most of which occurred abruptly in 2000-2001. The changes are seen in the composite below of two 2001 images, with the yellow being the tentative 2001 margin, green the 2006 margin and red the 2012 margin. A closeup of the area just south of Kap Zachariae indicates the change from 2006 on right to 2012 on left from an unrifted main outlet of ZIS, to an area of scattered ice bergs with rifts developing further west as well. This image from July 30, had turned to open water two weeks later. As of Sept. 2, 2012 there is still considerable open water in the embayment around ZIS, bottom image.
Steensby Glacier flows north from the Greenland Ice Sheet into the Arctic Ocean between Petermann Glacier to the west and Ryder Glacier to the east. The glacier terminates 100 km up the twisting Sankt George Fjord from the ocean after flowing 60 km down the twisting valley from the ice sheet. This distance and the fact that the fjord empties into the Arctic Ocean would suggest it is less easily reached by warming ocean water to melt the floating glacier tongue. The glacier has a thin floating ice tongue like Petermann Glacier at the terminus with a thickness of 75-105 m. The terminus as a result has a low velocity and would not accelerate and retreat via the same mechanism of backforce reduction that has led to retreat of almost all marine terminating outlet glaciers that do not have large floating ice tongues. The snowline was noted as 800 m in the 1970-1980’s, has in recent years been 1000 meters (Pelto, 2010). With the warm weather the past two summers it has seemed inevitable that Ryder and Steensby Glacier would have a terminus response. Steensby had last been observed in retreat back in 1947 (Ahnert, 1962). From 1947 to 1976 and since 1976 has changed little. On my return from glacier field work I checked the MODIS daily imagery from 8/15 and saw nothing. This glacier seemed a particularly likely culprit for retreat this summer because the terminus area is such a melange of ice as seen in the 2006 Landsat image (M),and as Ahnert had observed, the crack that created the icebergs is likely the same one visible in 2006, blue arrows. In the invaluable blog Arctic Sea Ice run by Neven, the calving event was noted by commenters on Aug. 24th Sphaerica, Twemoran and Espen Olsen. This is what makes the blog so valuable many of the participants are actively examining daily satellite imagery making interesting observations, and as a glaciologist this proves to be remarkably valuable and interesting resource time and again.
Here we first look at MODIS images of Steensby Glacier from 8/2010, 8/2011, and 2012. The 2012 images are from 8/12, 8/15 , 8/23 and 8/24, with the crack first appearing in the 8/15 and open water appearing on 8/23 and widening by 8/24. The icebergs approximate maximum dimensions are 4 km by 6 km. The last image is a terminus closeup.
Melting has been significant in northern Greenland for three straight summers. In 2010 the first image the melt area is below 1000 meters at the head of the Steensby Glacier outlet denoted by red arrows, this is a typical pattern of the last few years (P=Petermann, R=Ryder, S=Steensby). In 2012 the area of extensive melt has expanded from a zone around the head of the valley of Steensby and Ryder Glacier near 1000 m in July (blue arrows) to a wide zone extending all the way from Steensby to Ryder Glacier in August. Unlike Petermann Glacier, Steensby Glacier does not have a deep connection to the ice sheet as indicated by bedrock maps of the glacier from Bamber et al. (2011). The glacier is much narrower, thinner at the grounding line and its velocity is much less, volume wise the Steensby Glacier just lacks the importance in terms of influence on the larger ice sheet that Petermann Glacier has.
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. In this post we examine Landsat satellite imagery from 1992, 1994, 2010 and 2012 to illustrate the changes over the last two decades. There are three readily observable changes. The first, indicated by purple arrows, is the lateral recession 2.5 km upglacier of the current terminus. At this point the glacier was in contract with a proglacial lake. The lake shoreline has not changed from the 1992-1994 images, but the glacier margin is now 300 meters distant from the lake margin. The second change, indicated by yellow arrows, is of what was previously a secondary terminus that terminated in a small proglacial lake in 1992-1994. This small lake has turned into an embayment of the larger unnamed lake that the Jacobsen Glacier ends in. The secondary terminus has retreated 900 meters since 1992. The last change is the actual terminus retreat of Jacobsen glacier with the 1992 terminus indicated by the pink arrows and the 2012 terminus by the blue arrow on the northern margin. The retreat and lake expansion has been 1100 mters from 1992-2012, a rate of 55 meters/year, only a slight change from the 1990-2000 reported rate. The changes indicate a consistent mass balance loss that is typical of glaciers in the Coast Range from Lemon Creek Glacier to Bridge Glacier and Helm Glacier. The ongoing mass balance losses are resulting in substantial glacier area and volume losses ( Pelto, 2007; Scheifer et al, 2008).
Returned from the field yesterday. There was spectacular melting and forest fires in our field area of the North Cascades, Washington. Preliminary results will follow in 10 days. Alison Gletscher in western Greenland at 74.37 N and 56.08 W,had a spectacular retreat in the last decade. The 11 km retreat has been noted by Howat and Eddy (2011) and Joughin et al, (2010). The velocity of the glacier is typical of marine outlet glaciers increasing dramatically near the ice front to 3000 meters/year, image from Joughin et al, (2010). The recent increases in outlet glacier discharge have always been coincident with floating tongue losses. This causes reduced back pressure at the glacier front, letting up on the brakes; the resulting glacier thinning leads to less basal friction and further acceleration. If the glacier front retreats into deeper water the process will continue and increase. The acceleration is driven by changes at the calving front not by meltwater lubrication (Joughin et al, 2010) and (Bailey and Pelto, 2011). This post examines a 2000 and 2011 Landsat image of the glacier, the yellow arrows indicate the 2000 terminus and the red arrows the 2011 terminus location. . The glacier’s calving front is much longer than in 2000, however, there are a number of pinning points, purple arrows in image below that reduce the glacier velocity on the northern and southern margin. However, the high velocity, extensively crevassed middle section is still retreating. . MODIS imagery from 2012 indicates limited change to date this summer in the terminus position of Alison Gletscher, below is the August 9th image. This glacier is retreating similar to Kong Oscar, Upernavik and Epiq Sermia.
For the 29th summer in a row we will be measuring glacier mass balance in the field, in the North Cascades, Washington, over the next three weeks, no new posts during this period. Glacier mass balance is the most sensitive measure of glacier response to climate. In the past the only way to determine mass balance was detailed field measurements. Today there is sufficient satellite imagery to provide data that can be used in conjunction with ground truth to determine the mass balance of a glacier using a model. The ground truth we complete provides richer spatial detail than remote sensing can today. Satellite imagery provides excellent big picture and time specific data, but still needs ground truth. For example the National Operational Hydrologic Remote Sensing Center (NOHRSC) now provides daily snowpack and snowmelt maps that are based on satellite imagery and climate models. A snapshot is provided of two of these from early July 2012 in the area of Mount Baker, WA, where we will be working shortly note blue arrows indicating specific glaciers. The first image is the snowpack in snow water equivalent (SWE). It is assessed at over 30 inches remaining. The second is of the snowmelt in SWE for the same area over a 72 hour period ranging from 1.5 to 4 inches. NOHRSC products are not really designed for glaciated elevations or mid-summer conditions, the system has been well verified for most areas of our nation for most times of the normal snowcover season. The Sholes Glacier in summer fits neither. We will be measuring the snowpack at over 500 locations around the blue arrows. We will also be continuing to measure the snowmelt on the same glaciers as the summer progresses. Other satellite images provide a detailed look at a glacier, but are acquired only on occassion. This is indicated by the excellent images in Google Earth from Sept. 2009 and Sept. 2011 of Sholes Glacier which show a much different story in terms of snowpack extent. The blue dots indicate the 2009 snowline, where snow from the winter survived the summer melt season up to that date. In 2009 the glacier was 30% snowcovered at the end of the melt season, in 2011 the glacier was 95% snowcovered. We will be taking over 100 measurements of snow depth on this glacier to provide the detail that allows the pattern of snowcover alone to be used to identify the snowpack distribution and hence mass balance of the glacier.
Lumding Glacier, Nepal terminates in Lumding Tsho, a proglacial lake, in Dudh Khosi Valley in the Mount Everest region of Nepal. This lake poses a hazard for a glacier lake outburst flood n the Dudh Khosi valley. The lake expansion results from retreat of the Lumding Glacier.Bajracharya et al (2008) in a International Centre for Integrated Mountain Development (ICIMOD) study examined the changes in Lumding Tsho from 1962-2000 and found the lake grew from 0.2 km2 in 1962 to 0.77 km2 in 2000. ICIMOD has an ongoing specific focus on assessing glacier lake outburst flood potential. This was the result of a retreat of 40 meters/year from 1976-2000 and 35 meters/year from 1962-2007, as noted in figure below from Bajracharya et al 2008). Here we update the changes to 2013 using Landsat imagery.
This would lead to a lake length increase of about 800 m. The lake was 625 meter long and had an area of 0.1 km2, by 2007 the lake was 2180 meters long with an area of 0.9 km2 (Bajracharya et al 2008)Here we look at a 1992, 2009 and 2013 Landsat image and 2008 Google Earth imagery. The lake begins at the end of the heavily debris covered Lumding Glacier. Yellow arrow on each Landsat image indicates 1992 terminus and red arrow 2009 terminus location. The lake was 1675 meters long in 1992, 2325 meters long in 2009 and 2500 meters in 2013. This represents a retreat of 40 meters/year. The lake at 2.5 km in length now has an area of over 1 square kilometer. The glacier is fed largely by avalanching off the flanks of, blue arrows. The larger problem for the glacier in the future is the retreat of the terminus of the tributary glaciers that avalanche onto the lower Lumding Glacier. The blue arrows around the letter A in the Landsat images indicate the retreat of these feeder glaciers. The retreat of the two noted in the Landsat images has been approximately 300 meters. The lower section of the Lumding Glacier is heavily debris covered, brown arrow in Google Earth image, which insulates the underlying ice, reducing melting and retreat. This also indicates the avalanche source of much of the accumulating snow and ice. The increased distance to the feeding snow and ice slopes will reduce this input.
1992 Landsat image
2009 Landsat image
2013 Landsat Image
2008 Google Earth
The Lumding Glacier retreat is similar to the retreat of nearby Menlung Glacier, Tibet, Imja Glacier, Nepal and North Lhonak Glacier, Sikkim each retreating continually leading to lake expansion. This also fits with the general area extent losses and retreat that dominate the high mountains of central Asia.
I came across De Reste Bugt Glacier reviewing a recent paper by Walsh et al (2012). They identify a retreat of 1 km for the 2000-2010 period and a thinning of 40 m 15 km upglacier of the terminus and acceleration Walsh et al (2012). This is the typical model for glaciers along the Blosseville Coast of East Greenland, where 29 of 37 glaciers they examined retreated at least 500 meters from 2000-2010. This glacier does not reach the main ice cap, but drains the East Greenland Coastal mountain range. In this post we review Landsat imagery from 1985, 2000 and 2011 to identify changes. The terminus retreated 2.7 km from 1985-2000 and 1100 meters from 2000-2011. The 1985 terminus is marked by purple dots, 2000 by blue dots and 2011 by green dots. The yellow arrow indicates a prominent spot at the1985 terminus, the purple arrow the island just beyond the 1985 terminus, the blue arrow and red arrow the eastern side of prominent tributaries for comparison, the green arrow the 2011 terminus location. Beyond the terminus change of De Reste Bugt, there are substantial retreats of the tributaries 1-4. In 1984 all had much larger active fronts ending at lower elevations than today. This indicates that the changes are not due to just to terminus dynamics but that the mass balance that controls these smaller glaciers has been quite negative, as has been noted to the south on Mittivakkat Glacier by Mernild et al (2011). The summer of 2012 has every indication of being a record melt year for much of the Greenland Ice Sheet, and this will certainly have an impact going forward on De Rest Bugt and its neighboring glaciers. De Reste Bugt is just north of Sortebrae Glacier with the gorgeous twisting lateral moraines that is also retreating.
Coleman Glacier flows north from the Reef icefield on the northeast flank of Mount Robson. This glacier is 6 km long and has a relatively low slope descending from 2500 m to a terminus just above 2100 meters. Coleman Glacier flows north from the British Columbia, in an inventory of western Canada glaciers Bolch et al (2010) found that from 1985-2005 Alberta glaciers lost 25% of their area and BC glaciers 11% of their area. Marshall et al (2011) examining the impact on streamflow of glacier volume loss, estimate an 80-90% volume loss for Alberta glaciers by 2100 with a commensurate decline in runoff. By the time a glacier has lost more than 20% of its area glacier runoff declines as the reduced area exposed for melting has a larger influence than the increased melt rate per unit area (Pelto, 2011). A comparison of Landsat images from 1991 (top image) and 2009 (middle Image) indicate a retreat of 250 m. Formation of a new lake at the terminus is evident at the burgundy arrow. The third image is from the Google Earth imagery of 2006, the purple line is the 1991 margin, the burgundy line the 2000 margin. The retreat from 1991-2006 is 250 m, with 50 m of further retreat by 2010. A more detailed look at the 2006 Google Earth Imagery illustrates a more detailed story. This glacier in 2006 has an accumulation zone that is too small to support the current glacier size, a glacier needs at least 60% of its area to be snowcovered at summers end, and only 30% is snowcovered. . This is simply not just a bad year either. The number of annual layers exposed at the surface is at least 50, such layers emerge at the surface below the snowline as a glacier thins below the snowline. The annual layers emerging at the surface are marked by dark horizons which indicate the former snow surface of a layer, which collects dust throughout the summer and is dirtier than the bulk of an annual layer. Above the snowline layers are progressively buried by more recent winter layers and below the snowline layers are exhumed as the layers above melt away (second image). The location and number of annual layers indicate that today the accumulation zone is typically fairly close to the 2006 snowline. . The terminus area and lower 1 kilometer of the Coleman Glacier is quite stagnant as indicated by the degree of incision of surface glacier streams, the lack of crevassing and the smooth nature of the debris cover on the western side of the glacier. This section of the glacier is melting away. Glacier streams in an active flowing glacier will exploit any current or fairly recent crevasse feature to drain toward the glacier bottom often through a moulin. The lack of such drainage indicates a lack of movement that generates crevassing. The bottom image is a closeup of the main supraglacial stream with the blue arrows identifying the channel. This glacier is further north than the Columbia Glacier or Apex Glacier but is following the same trend.
Just published in Hydrologic Process is a paper from our 28 years of research on Mount Baker.
“Mass Balance Loss of Mount Baker, Washington glaciers 1990-2010” Mass balance is really the annual bank account for the glacier. Deposits are snow accumulation, withdraws are melting. A glacier that has greater income has a positive mass balance and increases in volume. Greater melting leads to losses in volume.
Mount Baker,North Cascades, WA has a current glacierized area of 38.6km2. From1984 to 2010, the North Cascade Glacier Climate Project has monitored the annual mass balance (Ba), accumulation area ratio (AAR), terminus behaviour and longitudinal profiles of Mount Baker glaciers. The Ba on Rainbow, Easton and Sholes Glaciers from 1990 to 2010 averaged 0.52mw.e. a1(m a1).
Terminus observations on nine principal Mount Baker glaciers, 1984–2009, indicate retreat ranging from 240 to 520 m,with amean of 370m or 14ma1. AAR observations on Rainbow, Sholes and Easton Glaciers for 1990–2010 indicate a mean AAR of 0.55 and a steady state AAR of 0.65. A comparison of Ba and AAR on these three glaciers yields a relationship that is used in combination with AAR observations made on all Mount Baker glaciers during 7 years to assess Mount Baker glacier mass balance. Utilizing the AAR–Ba relationship for the three glaciers yields a mean Ba of 0.55m/year for the 1990–2010 period, 0.03ma1 higher than the measured mean Ba. The mean Ba based on the AAR–Ba relationship for the entire mountain from 1990 to 2010 is 0.57m/year. The product of the mean observed mass balance gradient determined from 11 000 surface mass balance measurements and glacier area in each 100-m elevation band on Mount Baker yields a Ba of 0.50 m/year from 1990–2010 for the entire mountain. The median altitude of the three index glaciers is lower than that of all Mount Baker glaciers. Adjusting the balance gradient for this difference yields
a mean Ba of 0.77m/year from 1990 to 2010. All but one estimate converge on a loss of 0.5m/year for Mount Baker from 1990 to 2010. This equates to an 11-m loss in glacier thickness, 12–20% of the entire 1990 volume of glaciers on Mount Baker.
The two key measures of mass balance, which is direct measurements and measuring the snow covered fraction of the glacier at the end of the year, the accumulation area ratio. Below is the 2009 map of the snowcovered areas put together by Courtenay Brown, Simon Fraser University. This same year we were in the field and took measurements at the burgundy dots, in the second image. Each dot is worth three measurements. In two weeks we will adding more measurements to this data set for 2012. We do this largely by using a probe that can be driven through the snowpack from last winter, or in crevasses where the annual layering is evident like tree rings. The contrast between the snowpack distribution in September 2009 and 2011 is evident. The burgundy arrows point out bare ice regions. In 2009 the bare ice extent darker blue, was much larger than in 2011, when snowcover was quite good. The net trend over the last 20 years of mass balance loss is leading to the ongoing retreat of all Mount Baker glaciers.
In August we will be making a detailed study of the Easton Glacier for the 23rd consecutive summer. Our main focus is measurement of snow depth and snow melt on the glacier. We will be mapping the terminus position and two profiles of the surface elevation across the glaciers at 1800 m and 1950 m. We will also examine two new bedrock knobs that have melted out in the midst of the glacier at 2050 m. The Easton Glacier is important as a water resource for the Baker lake and Baker River Hydropower system. This hydropower system is capable of producing 170 MW of power. The runoff from Easton Glacier would normally flow into the Baker River below Upper Baker Dam, however it is extracted from the normal stream and routed through a pipeline to enter Baker Lake and then produce power via Upper Baker Dam (second image), note yellow dots showing runoff pathway. The Easton Glacier retreated over 2 km from its Little Ice Age maximum to 1955. By 1965 the glacier was advancing, this advance ended in the early 1980’s and by 1987 retreat from the moraine was evident. Beginning in 1990 we have made an annual survey of the glacier terminus noting a retreat of 320 m from 1987-2010. The first image below is of Easton Glacier from 1912 the second from 2011 with the same locations highlighted. A prominent knob on the upper glacier has changed little, ocher arrow. The lower margin of the glacier on either side of the main Easton at the blue arrow and red arrow show substantial thinning and retreat. The purple arrow indicates the terminus change. The lower Easton Glacier has changed a great deal in the last 100 years, not the upper glacier. This is an indication of a glacier adjusting to climate change that is retaining an accumulation and can survive. The last image in the sequence indicates the Little Ice Age terminus yellow line, the 1993 terminus orange, 1998 terminus is purple, 2004 terminus is green and 2009 terminus is ochre. In the above image the red arrows indicate the location of the two survey profiles we complete across the glacier. The green arrows indicate two locations of investigation for the summer, to the left is the top of the Deming Glacier Icefall that will visit and the right green arrow a new bedrock knob that emerged from beneath the glacier in 2009. A month from now we will be surveying the glacier covering the glacier top to bottom and side to side. We will be joned by Peter Sinclair who is going to use is videography skills to examine how we measure glacier change. The first image below is from Steph Abegg a superb climber and photographer who was with us in 2010 as part of Team Juicebox working on the Uncertain Ice documentary. The main goal of our research each year is assessing the glacier’s mass balance. This is the equivalent of its bank account, with snow accumulation being deposits and snow-ice melt being withdraws. We map the changes across the glacier and determine if the bank account grew or declined, 2011 map is below. Since 1990 the bank account has lost 10 meters of thickness of an average of 70 m total. Last year the glacier did gain over a meter. A key measure is the percent of the glacier in the accumulation zone (AAR), below 65% is a loss above a gain, bottom image. The 2012 winter was a La Nina which tends to lead to very good snowpack, the transition out of La Nina took place in late spring-early summer leading to greater melting than 2011, we will see in three weeks.
This glacier in 1988 reached the shore of Lago Sabbione.
From a Glaciers Perspective 