Posts Tagged mount baker glacier retreat

Roosevelt Glacier Retreat, Mount Baker, Washington

Roosevelt Glacier is on the northwest side of Mount Baker, Washington with its accumulation zone joined with the Coleman Glacier. My first visit to Roosevelt Glacier was in 1984, when the glacier had just completed a 30 year period of advance from 1949-1979.  Since 1979 the glacier has been retreating, image below. roosevelt 79This post examines Google Earth imagery from 1993, 2003 and 2009 along with field observations from the glacier. The purple line indicates the advance moraine that the glacier emplaced during the 1949-1979 period of advance. We mapped the location of this moraine in 1985, when it was still recent and very evident. The red line is from 1993, yellow line from 2003 and green line from 2009. In 1993 the area below the lip of lava flow cliff is thin and stagnant, cliff noted by purple arrow. By 2003 the glacier has retreated to the top of the cliff and by 2009 the glacier has pulled back from the edge of the cliff. By 2012 the lower glacier, viewed from the edge of the Coleman Glacier, is thin and uncrevassed in the lower 350 meters of the glacier, up to the red arrow. The glacier retreated 190 meters from 1979 to 1993 and 220 meters from 1993 to 2009. The rate of 14 m/year has been relatively consistent.roosevelt terminus 1993

roosevelt terminus 2003

roosevelt terminus 2009

roosevelt 2012
The glacier is fed by three principal accumulation zones: 1) A glacier tongue that descends from the summit plateau at 3200 meters, 2) an avalanche fed and direct snowfall region beneath the north ridge, at 2200 meters 3) an avalanche and direct snowfall fed region beneath the northwest face, at 2400 meters. The annual snowline has averaged 2150 meters on Roosevelt Glacier from 1984-2010, which has led to a similar retreat of 14 m/year and mass balance loss -0.52 m/year of all Mount Baker glaciers, Pelto and Brown (2012). Each summer we investigate the retained snow depth retained in the crevasse stratified exposures on Mount Baker in the 2400 meter range. Below are several images from this investigation. In the second image the magenta arrows indicate specific annual layers that have been retained. Typical thicknesses are 1.75 to 2.25 m. The next two images are from when we are in an icefall looking for the best exposure to measure the annual layer stratigraphic thickness. The behavior of this glacier parallels that of Deming Glacier, Boulder Glacier and Rainbow Glacier all on Mount Baker. roosevelt profile

crevasse roosevelticefall strat

icefall strat2

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Mount Baker Glacier Mass Balance

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.

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Deming Glacier Terminus Retreat

The reduction in width and crevassing in the Deming Glacier Icefall indicates a reduced flow into the terminus reach of the Deming Glacier. This post examines the retreat of the Deming Glacier from 1984-2010. The glacier has retreated significantly as have all 47 glaciers we observe in the field. The retreat parallels that of other Mount Baker glaciers, Boulder Glacier and Easton Glacier (Pelto,2006). Each year since 1990 we have been able to observe the terminus of the Deming Glacier from afar at our survey point. Only in two years have we actually visited the terminus 1996 and 2002. The latter proved hazardous enough to discourage further attempts. Deming Glacier advanced dramatically during the 1950′s and did not retreat substantially until the late 1980′s. The first set of images are from the survey point in 2003, 2006, 2007, 2008 and 2010. The yellow arrows indicate the narrowing of the debris free section of ice in the middle of the glacier. The red arrows indicate the moraines from the advance ending around 1980 including the lateral moraines and two sets of terminal moraines. The closer set of terminal moraines is where the glacier ended in 1996 when we visited the glacier. Both the lateral and end moraines are indicated. The stream issuing from the glacier front feeds the Middle Fork Nooksack River, which supplies some of Bellingham, WA water supply. We conducted a. The next set of images include a 1979 Austin Post USGS image from 1979 and the rest are from the Google Earth showing in order the 1984 map position (blue), 1994 terminus (magenta), 2006 terminus (green) and 2011 terminus (yellow). Note similarity of blue line and 1979 terminus. The glacier retreated 160 m from 1984-1994, 16 meters/year. From 1994 to 2006 the glacier retreated 240 m, 20 meters/year. From 2006-2011 the glacier retreated 120 m, a rate of 24 meters/year. The rate is still on the increase. deming closeup 1979The top image in the sequence below is a view from 2002 showing the end of the glacier (survey point from red X. The front was still steep at the time and the width of the debris near the terminus limited, clean ice width is 200 m.. By 2011 the terminus is not nearly as steep and most of the glacier width is debris covered. The view in Google Earth imagery from 1998 and 2011 indicates the change and the survey point is indicated by the red x. The last image is a 2011 closeup view in Google Earth the debris free ice section is 40 meters wide. What is causing the narrowing of the debris free ice is the reduction in velocity, the increased thinning of the clean ice in the center compared to the insulated debris covered ice at the edges. As the elevation difference increases debris slides off the side of the developing debris covered ridge (Pelto, 2001: 35).

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Mazama Glacier Retreat, North Cascades, Washington

Mazama Glacier flows down the north side of Mount Baker, a strato volcano in the North Cascades of Washington. The glacier begins at the summit plateau, 3260 meters, and terminates at the head of Wells Creek 1470 meters. This is a glacier we visit briefly each summer since 1984, but is not a focus of detailed observations. In 2010 we descended from its divide with Rainbow Glacier at 2100 meters to just above the terminus. In the 1970′s the USGS map (top image in sequence) indicates the terminus extended down valley to 1200 meters, this was after a period of advance for the glacier. The glacier advance 450 meters from 1950-1980 (Pelto and Hedlund, 2001). In 1987 we observed the glacier to have begun to retreat. By 1993 the glacier had retreated 200 meters. From 1993 (middle) to 2009 (bottom image) the glacier retreated an additional 750 meters. The rate of retreat has been higher for this glacier because of the loss of the low elevation debris covered terminus that had existed from the 1950′s-1990′s. The glacier is still heavily crevassed and active. The retreat will continue as indicated by thinning near the snowline of the glacier from 1993 to 2009. Note the expansion of the rock outcrop in glacier center (A) from the top image, 1993 to 2009 bottom image. There is also considerably less crevassing near Point A. Also note the stranded glacier ice at Point B and C in 2009. This loss has been due to 7 of the last 10 years having a snowline that rose above the elevation necessary for equilibrium. In 2009 at the end of the summer just 36% of the glacier was snowcovered, 65% needs to be snowcovered for equilibrium. .
In two weeks we will be visiting Mazama Glacier again. Given the heavy 2011 snowpack it is unlikely we will get to see the terminus which should be under avalanche debris.

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