Mount Cheops Cirque Glacier: Response of a Small Debris Covered Glacier to Climate Change
S.J. Rubin V00197024
Geography 477, Field Studies in Physical Geography, University of Victoria. (E-mail: [email protected])
ABSTRACT Global climate change is evident in the alpine regions of British Columbia, effects of which were observed and explored during field school investigations of a microclimate cirque glacier on Mount Cheops in Glacier National Park of Canada. Rapidly receding glaciers are becoming an important water resource concern for British Columbia. We are beginning to understand that our water supply is not inexhaustible, similar to that realization regarding BC’s timber resources in the late twentieth century. Water is vital not only as a resource for human use; changes in glacial hydrological systems are also changing patterns of vegetation and wildlife that are adapted to alpine conditions. A hydrological survey was conducted to estimate the contribution of the Cheops glacial melt waters into the Connaught Creek drainage system, by comparing discharges at various locations along the valley bottom and within the cirque. Simple observations, such as water clarity and discharge fluctuations during the day, help to provide insight into the glacial hydrological system. Another particular consideration is the effect of debris cover in helping to preserve glacial ice, which was observed on more than half of the Mount Cheops glacier. Using a series of air photos, a temporal assessment of the Cheops glacier is made possible. There have been very few studies on small glaciers in the area, and the ones that have been done, including this one, are limited by being conducted in one location at one time. This project seeks to understand the significance of small glaciers and their role as water resources, and how debris cover slows the retreat rate of some glaciers. There is no inventory of the small glaciers that are disappearing, and basically no baseline study to build our knowledge upon. This paper will illustrate the importance of continued studies and monitoring of these crucial water resources, which are threatened by increasing global air temperatures, and other climate change variables. Keywords Cirque glacier; debris cover; microclimate; climate change
BACKGROUND LOCATION Mount Cheops is located at the summit of Rogers Pass within Glacier National Park of Canada in the Selkirk Mountain range. The park is approximately 48 kilometers east of Revelstoke. Mount Cheops is accessed via the Balu Pass trail, with the trailhead at the Rogers Pass Visitor Center on the Trans-Canada Highway. The Selkirk Mountains are a prime example of interior rainforest, receiving approximately 2000mm of precipitation per year (Parks Canada). Compared with our 800mm on the coast in Victoria, we see that Glacier National park is very wet or very snowy all year round. The study site in the north
Figure 1, Topographic map of Rogers Pass cirque of Mount Cheops is challenging to access, and includes bushwhacking a short distance through nearly impenetrable aspen groves, followed by scrambling up a steep boulder field until reaching the terminal moraine and beyond.
SIGNIFICANCE OF CHEOPS ICE IN THE SELKIRKS The Selkirk Range and surrounding mountainous regions are extensively glaciated. There are a few large glaciers and ice fields, such as the Illecillewaet Nevé, but there are a vast amount of small patches of glacier ice. This is due primarily to the influence of microclimates produced in mountainous areas. The main requirement to produce a small microclimate glacier is a large north facing headwall, creating nearly constant shade on the slope below. The headwall also helps build deeper snowpack in the winter, because it is too steep for snow to stick to, creating avalanche accumulation on the slope below. These two factors
Figure 2, False colour satellite image of the northern have helped to create the small Selkirk Mountains, blue is glacier ice. glacier on Mount Cheops, and many other glaciers in the region, and around the world. In this false colour image, compare the amount of large blue areas with the small blue areas. It can be argued that the accrued influence of all the small glaciers combine into a very important water resource. If the influence of the Mount Cheops glacier were studied on it’s own, it would be insignificant, so this study assumes that the Mount Cheops cirque glacier is representative of a type of glacier that is very common in the region, and that type of glacier’s combined abundance is a significant resource. The Cheops glacier is very small, about 1/1031 the surface area of the Illecillewaet Nevé, yet the Cheops glacial discharge is 1/8th of the Illecillewaet discharge measure during field school. It is also important to note the altitude of tongue of each glacier; the Illecillewaet Glacier terminus was at approximately 1975 meters above sea level this summer, compared to the Cheops tongue at about 1800 meters. The effects of microclimate at the Cheops glacier sheds light on this discrepancy. The disproportionate surface area to runoff is likely due to the difference in exposure of glacial ice to direct sunlight. The Cheops glacier is mostly in the shade and covered by insulating debris, leaving it susceptible to melt, due to warm air temperatures. The Illecillewaet Nevé, however, is entirely exposed to direct insolation, and is therefore susceptible to sublimation, or a direct phase change from solid ice to water vapour. This is a direct rational for believing that small microclimate glaciers are an important source of freshwater for river headwaters: they melt more than they evaporate, unlike the bigger glaciers in the region.
MICROCLIMATE The Mount Cheops cirque glacier is greatly influenced by a unique geomorphic and climatic system. The temperature range in the region is very prone to lots of freeze/thaw cycles, which is essential for the weathering processes involved in cirque formation. “Cirques are often preferentially oriented according to the direction of solar radiation” (Graf, 1976). “Cirques result from two separate groups of processes: 1. Mechanical weathering and mass wasting, and 2. Erosion by cirque glaciers” (Ritter et al., 2002). The north side of the mountain has a very steep exposed rock headwall that descends from the summit down to a cirque valley that is occupied by the small glacier. The layout of this valley is consistent with descriptions of cirque formation and morphology. The large northern facing wall provides permanent shade on most of the glacier, with only a small portion of debris-covered ice extending far enough from the wall to receive direct sunlight at midday during the summer months. The headwall serves two functions in Figure 3, Base of last winter's avalanche cone on top of older deposits. the balance of the glacier; lots of snow falls on the wall, but it is too steep for snow to cling to during the winter months, avalanches deposit the snow from the wall down on the surface of the glacier, creating a large cone of snow at the edge of the headwall. The other function that the headwall serves is a source for debris cover. Alpine areas are subject to a strong freeze-thaw cycle, creating very extensive mechanical weathering in the area. The headwall is eroding almost constantly, and provides an enormous amount of debris to cover and preserve the glacier ice.
DEBRIS COVER The Cheops cirque glacier is significantly influenced by the presence of debris cover. The debris is primarily composed of large angular boulders, but
Figure 4, Debris cover high on the glacier, 450 meters below the head wall. there are areas of ice covered with fine silty sediments. There is an enormous amount blocky debris cover over a large area, creating landforms typical of rock glaciers. These landforms include arcuate ridges of debris and hummocky ablation moraines, which are consistent with findings at other rock glaciers, such as the Wenkchemna glacier in the Rocky Mountains (Gardner, 1977). The Cheops rock glacier feature is ice-cored, “containing subsurface ice with a superficial coating of rock fragments (up to several meters thick)… The coarse block layer may act as a thermal filter to protect the permanently frozen ice core if snow cover is thin or absent” (Ritter et al., 2002; Humlum, 1997). Gardner’s Wenkchemna paper also suggests that debris cover is responsible for creating a lag time in glacial activity relative to non-debris covered Figure 5, Hummocky ablation moraines indicate rock glacier stagnation. glaciers in the region. The Wenkchemna glacier, for example, was estimated to lag 70 years behind other glaciers reaction time to climatic change.
METHODS SITE SELECTION The Cheops cirque glacier was selected as a safe site to explore over the coarse of two daytrips. Other glaciers in the area are more difficult to access, and would have limited the amount of time at the site for observations. The Cheops cirque is located about 2 km from the Glacier Compound, and the Balu Pass trail allows close access to the site. The trail is along Connaught Creek, and accessing the cirque is easiest at the confluence of the cirque drainage creek into Connaught Creek. The drainage from the glacier descends a steep block field, with its loose and wet rocks, it is a dangerous area to travel through. A thin, active glacier is located in the cirque along the steep headwall, with ice extending over 1 km down slope from the wall. There was nearly constant rockfall all over the headwall, posing a hazard while exploring on the glacier. The Cheops cirque glacier proved to be a dynamic landscape, with changes noticed just between the two days. One change, for example, was the collapse of a snow bridge that was present over a crevasse on the first day, but was gone on the second day. Another change was due to weather conditions, while the first day was clear; the second day’s weather conditions were fog and rain. The drainage creek acted very differently between the two days. Unfortunately, the hydrological survey was only conducted on day two.
SURVEY – MAKING A FIELD MAP Simple surveying techniques using a digital rangefinder (Nikon Forestry 550), measured distances and angles between landmarks. These were used to create an estimate of the size of the glacier, and to determine how much wastage has occurred based on the height of lateral moraines above the surface of the ice. This height difference indicates the amount of glacial wastage, which is an important consideration because glaciers do not only recede at their tongues. The field survey also attempted to calculate the amount of glacial surface area that is debris covered compared to the surface area of exposed ice and firn.
Figure 6, The Mount Cheops cirque is an intricate setting for surveying.
TRANSECT PROFILES A topographical profile is a good visualization for understanding how the aspect and topography of the Cheops cirque creates a microclimate glacier, with a good accumulation zone, lots of source rock for debris cover, and protection from direct sunlight. A cross sectional profile of the glacier and moraines helps to illustrate the down wasting of the glacier.
AIRPHOTO & FALSE COLOUR INTERPRETATION Airphoto interpretation proved to be challenging. The first obstacle is obtaining the airphotos of the location. The airphoto warehouse located in the Vancouver Island Technology Park houses provincial airphotos dating back to the 1950s. Airphotos of Mount Cheops were found from 1951, 1986, 1991 and 1996. These airphotos do not easily match up, as scale and angles from the plane to the glacier were different in all of the photos. Instead of creating the classic receding glacier airphoto image, the four images are displayed next to each other, so that the changes on the landscape can be easily identified. The classic interpretation method of drawing the glacial extent from previous years did not work well because of the challenges associated with lining up landmarks in all four photos. The extent of ice does not appear to have changed drastically over the roughly fifty year period, but the debris covered area of the glacier seems to be completely reworked between all of the photos. False colour satellite images are useful in assessing the glaciation in the region. The blue areas of these photos clearly shows exactly where glacial ice is located. Using a grid overlay, the surface area of the Mount Cheops glacier was compared to the Illecillewaet Nevé. Using a small grid, the Cheops glacier was first compared to the Ursus Major glacier, and then that glacier was compared to the Illecillewaet using a larger scale grid. The comparison between the Cheops glacier and Illecillewaet is relevant because drainage data was collected from both sites. All of the Cheops glacier runoff converges at a creek just above the Connaught Creek, allowing for the measurement of all of the Cheops runoff. At the Illecillewaet, however, runoff data cannot be assumed to be of the entire Nevé, because it likely drains through various systems, but discharge was collected at the Illecillewaet River. Using the false colour photo surface area comparison, the comparison of discharge from the two locations becomes a meaningful measurement.
HYDROLOGICAL BASELINE STUDY Discharge measurements were taken at various locations, and at various times, including repeat measurements at some locations. The goal of these measurements was to determine how much water the Cheops glacier contributes to Connaught Creek. To do this discharge was measured above and below the confluence of the Cheops drainage into Connaught creek, and the main Cheops drainage creek itself. Also, to further understand the hydrological processes of the Cheops glacier, melt water discharges were measured along transects below the glacier. This was done in an attempt to estimate the amount of surface runoff near the terminus of the glacier compared to the discharge at the valley bottom, with a presumption that a large portion of the total melt water travels down slope beneath the surface. Because it was raining during the hydrological survey, observations of water quality were important. It is easy to discern which creeks originate at the glacier because that water was heavily sedimented, while rainwater runoff was clear.
RESULTS FIELD MAP & TRANSECTS
Figure 7, Profile of the Mount Cheops cirque showing the altitudinal extent of the cirque glacier.
Surveying is an important step in understanding how the glacier is reacting to climate change. The main challenge in assessing the extent of this type of glacier is determining the margins of the ice. It is practically impossible to see
Figure 8, Mount Cheops cirque glacier cross-section where the glacier ends and debris showing approximately 11 meters of down wasting. field begins because the glacier is covered with so much rock. The cross section was measured at an area where there was exposed ice at the margin, simplifying the task. The ice is lying up against the inner lateral moraine, leading to an assumption that the glacier has not receded very quickly since its last surge.
AIR PHOTOS & FALSE COLOUR SURFACE AREA COMPARISON The air photo series is very difficult to use meaningfully for a variety of reasons, including low resolution of the images, the small size of the study site, shadows cast by the headwall, etc. What is clear from looking at these airphotos, however, is the fact that the large debris fields are completely reworked between photos in the series. This suggests active glacial processes are at work under the cover of debris, and shows many signs associated with rock glaciers. A large feature is visible on the lower section of debris-covered glacier in 1951 that is completely gone by the next photo. Arcuate ridges, furrows and hummocky ablation moraines are clearly seen changing through time. The extent of the glacier does not appear to have changed drastically over the nearly 50 year period covered by these airphotos.
Figure 9, Air photo series: from left to right, 1951, 1986, 1991, 1996.
HYDROLOGICAL STUDY Approximately 70% of the water flowing down Connaught Creek originates in the Mount Cheops cirque. By measuring discharge above and below the Cheops input, and the Cheops discharge itself, a detailed assessment of the origin of water in the creek was made possible. These findings suggest that the Cheops glacier supplies a significant amount of water into the hydrological system. Other components of this survey included measuring the discharges of surface runoff channels along transects below the glacier. This was done in hopes of comparing the surface runoff high on the mountain with the discharge creek in the valley. Only a small proportion of the water measured in the discharge creek in the valley was accounted for across the slope, suggesting that a large amount of water is flowing downhill under the surface of the slope. This is not surprising considering that the slope is primarily made up of large boulders. It is also interesting to note that the combined measurements of the Cheops drainage and the other drainage opposite Cheops combine to 1.29 m3/s, very close to the total of 1.38 m3/s measured downstream of the confluence. This suggests that the discharge measurement techniques used were fairly accurate.
Figure 10, Airphoto showing location drainages and survey sites.
DISCUSSION LOCATION, HISTORY & ENVIRONMENTAL IMPACT Mount Cheops is located in the Selkirk Range of the Columbia Mountains. The region has been known as ‘Big Bend Country’, referring to the course of the Columbia River, which binds the Selkirks to the east, north and west. This region was first explored in the 19th century, during the gold rush era. Subsequently, the region was thoroughly explored during the discovery and surveying of the first Trans-Canadian railroad route. In 1881 the decision was made for the Canadian Pacific Railway (CPR) to cross the Great Divide at Kicking Horse Pass, east of Mount Cheops and Rogers Pass, in the Rocky Mountains. The route west from Kicking Horse Pass was in need of discovery, and Major A.B. Rogers was the man hired to find it. The easiest place to route the railway would have been along the Columbia River, but the ‘Big Bend’ creates an enormous detour, over 400 km. A pass directly through the Selkirk Range was the shortcut that was needed. Major Rogers began his search for the shortcut from what is now Revelstoke, and traveled east through the mountains up the Illecillewaet River. Following the river brought Major Rogers very close to the summit of the pass, but not all the way. Mount Cheops lies just north of the Illecillewaet River headwaters, and creates the only part of the route not along a river. Mount Cheops has literally played a role in Canadian history, primarily as one of the most avalanche prone areas that the transportation corridor goes through. Mount Cheops has been the site of some of the worst disasters in Canadian transportation history. In the railway’s first thirty years of operation, nearly 200 employees died in the area, including 62 men buried in an avalanche that cut off of Mount Cheops in March of 1910. That experience prompted the decision to dig a tunnel directly under the pass, averting the worst of the avalanche hazards to the transportation route. The tunnel opened in 1916, and the summit route along the base of Mount Cheops was abandoned until the construction of the Trans-Canada Highway in 1956. The region became Glacier National Park of Canada in 1886, two years after construction of the railway through the pass. Rogers Pass National Historic Site is also part of the park, commemorating the importance of the development of the trans-continental railway through the pass. This area would have never become easily accessible without the development of the transportation corridor, and therefore, we would have not had our Field School there without the railway, this being the first significant point of the study site on Mount Cheops. Since the Trans-Canada Highway opened, the region has become home to the world’s largest active avalanche control program run by the Canadian Military. The Snow Punchers operate 105 mm Howitzer guns, used to bomb the most prone avalanche starting zones. The slides are started while the highway is closed to traffic, which has greatly reduced the avalanche hazards in the area. Evidence of this activity was found on a moraine high on the north side of Mount Cheops, where unexploded ordinance was found during a field school excursion. The environmental impact of the transportation corridor is clearly evident upon exploration of the glaciated areas of the park. Black soot is clearly seen in annual layers deposited on the ice in some places, increasing the amount of solar energy absorbed at the surface of the ice by lowering the albedo. Imagine over a century of locomotives burning fuel at the feet of these great mountains, 50 years of millions of cars passing through, and image millennia of no combustion engines. It seems so obvious now that the transportation industry has drastic impacts on the landscape. Between 1916 and 1988 the CPR operated ‘pusher’ locomotives to help heavy trains make it up the steep grades in the Selkirks. These ‘pushers’ added 70,000 horsepower to each train; in this respect the environmental impact is quite shocking. Glaciers in the park are racing up the mountains, disappearing before our eyes. When considering the effects of sublimation on the large exposed glaciers, the input of black soot on the surface makes an enormous difference in the energy balance of the glacial ablation.
Figure 11, A 1966 oil company advertisement bragging about their environmentally destructive capabilities.
CLIMATE CHANGE TO MICROCLIMATE The glaciers in Glacier National Park of Canada are diminishing rapidly. Since the first photograph of the Illecillewaet Glacier was taken in 1887, the tongue has retreated over 2000 meters. A National Park survey approximates that large glaciers in the park are a third of their size compared to when they were first surveyed in 1850. “Only 27% of the 99 km2 area of Glacier National Park covered by glaciers in 1850 remained by 1993” (Pelto, 2009).
Figure 12, Mount Sir Donald and the Illecillewaet Glacier, 1887 (unknown photographer) and 2009 (S.J. Rubin). Scientists have been aware of the effects of pollutants in the atmosphere since at least the mid 20th century. An estimate from a 1958 publication states: Our industrial civilization has been pouring carbon dioxide into the atmosphere at a great rate. By the year 2000 we will have added 70 percent more carbon dioxide to the atmosphere. If it remained, it would have a marked warming effect on the earth’s climate, but most of it would probably be absorbed by the oceans. Conceivably, however, it could cause significant melting of the great icecaps and raise sea levels in time. (N.A.S., 1958) This estimate was based on a solid understanding of Earth’s energy Figure 13, Cover of a 1958 publication that predicts global warming as a result of anthropogenic changes to balance, and that the addition of the atmosphere. greenhouse gases into the atmosphere causes changes in the amount of heat being trapped near Earth’s surface. The authors understood that there would be implications for Earth’s ice, and sea level, but their estimates were off. The population more than double in the time since the book was written until the year 2000, and with it the demand for fossil fuels has grown exponentially. Their estimate of a 70% increase in carbon dioxide turned out to be more like a 300% increase, and their prediction that most of the CO2 would be absorbed in the oceans was also quite far off, the oceans have absorbed only 30% of atmospheric CO2 (E.I.S., 2009). Also, the authors did acknowledge changes in atmospheric temperatures, but they did not seem to forecast the changes this would cause to ocean water chemistry. Acidification of the oceans due to increased absorbed CO2 is one of the greatest problems our society is facing today. Many sensitive oceanic ecosystems are slowly being destroyed, such as bleaching coral reefs all over the world. Global sea level rise is also a major problem, with the potential of creating millions of climate refugees all over planet Earth. The focus of this paper, however, is on the effect of melting glaciers to future water security issues. Million of people around the world depend on snowmelt and glacial runoff for their drinking, agricultural, and industrial water supply. It is therefore extremely important to understand how climate change is affecting snowpack and glacial mass balance in the world’s mountainous regions. Changes in glacier run-off have profound effects on the volume and timing of water discharged into rivers, with important consequences for water supplies, hydro-electricity generation, maintaining river and riparian habitats, fish populations and recreational use. This study was conducted with the goal of helping to add to baseline knowledge of how small microclimate glaciers are reacting to climate change in British Columbia. According to the Intergovernmental Panel on Climate Change (IPCC), air temperature is considered to be the most important factor
Figure 14, Global near surface air temperature. Known as the 'Hockey controlling glacier retreat. Stick' graph. Their studies show that for a typical mid-latitude glacier, a 1oC temperature rise would have the same effect as a 30% decrease in cloudiness and a 25% reduction in precipitation. The ICPP also states that since the 1970s winter snow depth and spring snow cover have decreased in Canada, particularly in the west, where air temperatures have consistently increased. There is also evidence that the April 1st snow water equivalent has decreased 15-30% since 1950 in the western mountains of North America, particularly at lower elevations in spring, primarily due to warming air temperatures rather than to changes in precipitation. These changes in snowpack greatly affect the amount and timing of discharge, which in turn affects the entire eco-system. These vulnerabilities exist along the entire course of the rivers with headwaters in alpine areas.
CONCLUSIONS Knowing that the Illecillewaet glacier has retreated over 2000 meters since 1887, it is interesting to imagine the Cheops glacier barely changing in comparison. The effects of microclimate are essential in the creation and preservation of small cirque glaciers. Without the shade, avalanche accumulation and source rock from the north facing headwall it would be impossible to maintain a small glacier with current climatic conditions. The fact that there are some glaciers that do not appear to be disappearing as fast as other glaciers in the region is intriguing, it seems timely to consider these remaining glaciers as important sources of water in the future, but more detailed studies and inventories are essential. While the climate change debate wages on in politics and media, the glaciers of our alpine regions are disappearing at an alarming rate. Glacial data and visualization is one way to end the debate; warming temperatures have irreparable effects on our water reserves. Repeat photography of glacial landscapes is leaving humanity with a legacy of bedrock where there used to be ice. Resource managers can take steps in reducing the environmental impact of transportation through the park, for example filters on the railway tunnel exhaust systems could capture much of the soot released in the park. Now that there is a solid understanding that increased atmospheric CO2 is warming the planet and causing glaciers to disappear, it is time to mitigate humanity’s pollution habit. Glacier are not a renewable resources, they have been developing over tens of thousands of years, and we have the capabilities to destroy them within a century.
REFERENCES Extreme Ice Survey.