The video is of a single day of field work on Rainbow Glacier on 8-7-2018. This was our 702nd day of fieldwork during the project that began in 1984. On this day the field team consisted of Mariama Dryak, Erin McConnell, Jill Pelto and Mauri Pelto. Rainbow Glacier is a valley glacier on the northeast flank of Mount Baker, a stratovolcano and the highest mountain in the North Cascade Range, Washington. The glacier begins at a saddle at 2200 m sharing a divide with Mazama and Park Glacier. The glacier descends from the saddle through an icefall at 1950 m into the Rainbow Creek valley terminating at 1400 m. The consistent accumulation area extends from 1800 m to the saddle region above 1950 m. The glacier tongue features a deeply incised supraglacial stream channel. From 1984-2018 cumulative mass balance loss has exposed several bedrock knobs along the southern margin of the glacier.
Runoff from the glacier drains into Baker Lake, a reservoir for the Baker Dam hydropower facilities that have a generating capacity of 215 MW. Rainbow Glacier advanced during the 1950-1979 period building a terminal moraine. At the time of the first field season in 1984 the glacier was still in contact with this moraine. From 1984-2018 the glacier has retreated 620 m. In 2018 the mass balance was -0.53 m.
Terminus of Rainbow Glacier in 2018
Figure 1 is a map of the Rainbow Glacier indicating the mass balance measurement network.
Mass balance map of Rainbow Glacier in 2017 with mass balance isoline in m of water equivalent (Map by Ben Pelto)
April 1 winter accumulation at the longer term North Cascade SNOTEL stations (Fish Lake, Lyman Lake, Park Creek, Rainy Pass, Stampede Pass and Stevens Pass).
For North Cascade glaciers the accumulation season provides that layer of snow, that must then last through the melt season. A thin layer sets the glaciers up for a mass balance loss, much like a bear with a limited fat layer would lose more mass than ideal during hibernation. The 2019 winter season in the North Cascade Range, Washington has been unusual. On April 1 the retained snow water equivalent in snowpack across the range at the six long SNOTEL sites is 0.72 m, which is ~70% of average. This is the fifth lowest since 1984. The unusual part is that freezing levels were well above normal in January, in the 95% percentile at 1532 m, then were the lowest level, 372 m of any February since the freezing level record began in 1948. March returned to above normal freezing levels. As is typical periods of cold weather in the regios are associated with reduced snowfall in the mountains and more snowfall at low elevations. In the Seattle metropolitan area February was the snowiest month in 50 years, 0.51 m of snow fell, but in the North Cascades snowfall in the month was well below average. From Feb. 1 to April 1, snowpack SWE at Lyman Lake, the SNOTEL site closest to a North Cascade glacier, usually increases from 0.99 m to 1.47 m, this year SWE increased from 0.83 m to 1.01 m during this period.
The Mount Baker ski area snow measurement site has the world record for most snowfall in a season 1140 inches (28.96 m) during the 1998/99 snow season. The average snowfall is 633 inches (16.07 m) with snowfall this year as of April 15th at 533 inches (13.53 m). Below is a Landsat image from April 15, 2019 indicating the snowline at ~1000 m in the Nooksack River Valley and 900-1000 m in the Baker Lake valley.
This year for the 36th consecutive year the North Cascade Glacier Climate Project will be in the field measuring North Cascade glaciers, the early signs point towards a seventh consecutive negative balance year.
Freezing levels at Mount Baker, WA from the North American Freezing Level Tracker. February lowest mean freezing level since 1948.
Mount Baker Cloaked in winter snow in 4/15/2019 Landsat image MB=Mount Baker, MS=Mount Shuksan, NR=Nooksack River
From 1984-2014 we have monitored the mass balance of the Rainbow Glacier on Mount Baker, North Cascade Range, Washington. This entails detailed monitoring of snowpack depth in July and August, and subsequent ablation to the end of the melt season. On July 13th the glacier was completely snowcovered. By August 10th the snowline had risen to 1575 m, with 1.4 m of ablation since July 13th. We measured the snowdepth at 85 locations on the glacier, with only 6 measurements exceeding 3.5 m on Aug. 10th.Ben Pelto and Ashley Edwards examining crevasse stratigraphy both the 2013 and 2014 layers evident.
Limited snowpack below the main icefall at 1750 m on Aug. 10.
Limited snowpack below the main icefall at 1750 m on Aug. 10.By September 27th the snowline had risen to 1975 m with a few pockets of snow retained where the snowdepth had exceeded 3.2 m on Aug. 10th. Snowdepth at the Sept. 27th snowline had been 3.0 to 3.2 m on Aug. 10th. This indicated ablation of approximately 3 m of snowpack, 1.8 m of water equivalent from Aug. 10th to Sept. 27th. Ablation from July 13th to Sept. 27th was 5.3 m of snowpack and 3.2 m w.e. This was 5-10% more ablation than any other year since 1984. A comparison of images from the ground on Aug. 10th indicates the snowpack on the glacier from 1550-1950 m, the blue arrows indicate locations where a patch of 2014 snow remained on Sept. 27th. The Sept. 27th image was taken by Tom Hammond from Rainbow Ridge the only location where the whole glacier can be viewed. The firn is simply old snow that survived a summer and could be from 2012 or 2013. Aug. 10th accumulation zone view
Tom Hammond Image adusted to show firn, ice and retained snow. Sept. 27th
Winter snowpack was normal on Mount Baker, the record ablation then led to a large negative mass balance for the glacier of -1.8 m, but not a record loss. The ablation did lead to many significant surface streams on the glacier shown below, which drain into the glacier at moulins.
The terminus of glacier retreated rapidly from 1984 to 1998, but has slowed as it currently is in an avalanche runout zone. We visited the terminus in 1984 and all retreat is measured from that point when the glacier was in contact with an advance moraine from the 1955-1980 period of advance. A comparison of 1993 and 2006 Google Earth images indicates the retreat, red outline 2006 margin and black outline 1993. The 2014 image taken by Tom Hammond indicates that the terminus did get exposed in 2014 which will lead to additional retreat when we measure the terminus position next summer. Total retreat from 1984 to 2014 is 490 m. 1993 Google Earth view of terminus
2006 Google Earth view of terminus.Picture of the terminus in 2014 indicating the 214 and 1984 position. Taken by Tom Hammond from Rainbow Ridge.Ablation zone on Aug. 10
If glaciers did not change in response to climate, we would not have to think about their role in water resources in the watersheds that they reside. During the last two years in an ongoing study with the Nooksack Indian Tribe we have been working on quantifying the role glaciers play in that watershed. Glaciers comprise the headwaters of the Nooksack River and are a critical source of summer discharge and greatly influence summer stream temperatures. There are nine species of salmon in the watershed that the Nooksack Indian Tribe depends on for cultural, subsistence, and economic uses. Climate change is an additional new threat to salmon that has caused and will continue to cause an increase in winter flow, decreased summer baseflow, and increased summer water temperatures.
This post will focus on the changing impact of glaciers on streamflow and the evolving water temperature threat. The Nooksack River watershed has three significant watersheds, South Fork, Middle Fork and North Fork. The South Fork has no glaciers, the Middle Fork has four significant glaciers and 2% of the watershed area above the USGS gage is glaciated. The North Fork has 12 significant glaciers that cover 6% of the watershed area above the USGS gage. Here we examine stream discharge and water temperature at USGS gages on each stream to illustrate the different response to 12 warm weather events during the summers of 2009, 2010, 2012 and 2013. During each of these periods we have along with Oliver Grah and Jezra Beaulieu, working for the Nooksack Tribe, have been observing the ablation and runoff directly from the glaciers. The largest area of glaciers are those on Mount Baker, a strato volcano that is the highest mountain in the North Cascades. Pelto and Brown (2012) note that terminus observations on the nine principal Mount Baker glaciers, 1984–2009, indicate retreat ranging from 240 to 520 m, with a mean of 370 m or 14 m/year. Pelto and Brown (2012) observed that this is the result of a sustained mass balance loss averaging -0.5 m/year during the 1990-2010 period. This equates to an 11-m loss in glacier thickness, 12–20% of the entire 1990 volume of glaciers on Mount Baker. This summer we will for the 31st consecutive year be measuring glacier mass balance on Mount Baker.
Mazama Glacier headwaters North Fork
Deming Glacier headwaters Middle Fork
Crevasse examination
Probing snow depth
Outlet of Sholes Glacier, North Fork
Measuring snow depth in crevasse
During each of these events ablation was measured on glaciers in the basin. For stream discharge, a 10% increase is set as the key threshold for significant response to each warm weather event. For the North Fork 10 of 12 warm weather events exceeded the limit, in the Middle Fork 4 of 12 events had a significant response and for the South Fork none of the 12 events led to a 10% flow increase. It is apparent that warm weather events increase glacier melt, thus enhancing flow in the North Fork. In a basin without glacier runoff the hydrologic system consistently experiences reduced discharge.
For water temperature, an increase of 2° C is the threshold of significance used for response to warm weather events. In each the North Fork and Middle Fork, 2 of 12 events exceeded this threshold, and for the South Fork 12 of 12 events exceeded this threshold, each event is a green ellipse on the charts below. Warm weather events consistently generate a significant increase in stream water temperature only in the non-glaciated South Fork Basin. During 6 of these 12 warm events, runoff measurements below Sholes Glacier and ablation measurements on Sholes and Easton Glacier indicate daily ablation ranging from 0.05-0.06 meters per day, which for the North Fork currently yields 9.5-11 m3/second. This is 40-50% of the August mean discharge of 24 m3/second, despite glaciers only covering 6% of the watershed. Increased glacier discharge largely offset the impact of increased air temperature on stream water temperature during the warm weather events. In the charts below note the red line with diamond markers that is the South Fork stream temperature and the top brightest blue line that is North Fork discharge and what happens during the warm events, green ellipses. Also note the South Fork discharge bottom blue line does not respond nor does the North Fork stream temperature red line with triangles.
As the glaciers continue to retreat the North Fork will trend first toward the more limited impact of the Middle Fork and then the highly sensitive South Fork where warm weather leads to declining streamflow and warming temperatures. This will lead to a situation similar to the Skykomish River where the number of low flow days has sharply increased. The retreating glaciers include the Sholes, Roosevelt,Deming and Mazama.
Number of the 12 warm weather events with increased discharge, increased water temperature and the percent of glaciation in each basin
Streamflow and water temperature in the Nooksack in Summer 2009
Streamflow and water temperature in the Nooksack in Summer 2010
Streamflow and water temperature in the Nooksack in Summer 2012
Streamflow and water temperature in the Nooksack in Summer 2013
October 1 marks the end of the hydrologic year. For glaciers this should be the end of the melt season, though this year in the North Cascades it is not. The year began with excellent snowpack in the North Cascades 4th highest since 1984. The ablation is primarily June-September, after a cool June, the melt season has been sustained and warm. The June-Sept. period is the fourth warmest of the 1990-2012 period and the warmest for the July-Sept. There was not exceptional periods of heat, just sustained warmth due to the lack of cool wet systems in the region. This was evident from a period of 47 consecutive days with less than .01 inches of ppt at SeaTac Airport. The warm weather is projected to extend at least through Columbus Day. . Here we will examine Easton Glacier on Mount Baker. On July 20 the snowpack was still extensive covering 100% of the glacier. By August 10 the glacier had substantial blue ice. Note images from new video on research taken then. A series of Landsat images below are from July 20, August 25th and Sept. 26th. The orange areas point to the same locations. For the August and September image there is a second image, the last two in sequence, of each with the glacier outlined by yellow dots and the blue ice zones where the snowpack had melted away a darkened blue. The imagery does not distinguish the exposed 2011 firn from the 2012 snowpack. . Comparing images from 8/10/2012 and one month later 9/8/2012 the expansion of bare ice is evident. A marks the western terminus that was surveyed this summer as having experience 310 m of retreat from 1990-2012. B marks an area with average snow depth of 0.7 m on 8/10 and had lost snowpack and 1.4 m of ice by 9/8. The top of the C had snowpack of 1.8 m on 8/10 and by 9/8 was at the snowline. D marks an icefall that has expanded considerably. E marks an area with 5.5 m of snowpack on 8/10 and 3.8 m of snowpack on 9/8. By Sept 30 considerable additional melting had occurred. Final mass balance results will emerge over sometime in November. We measured snowpack depth at over 400 locations on Mount Baker using probing and crevasse stratigraphy, last two images.
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.
From a Glaciers Perspective 
