Field Notes on the Athabasca Glacier and Columbia Icefields Region
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FIELD NOTES ON THE ATHABASCA GLACIER AND COLUMBIA ICEFIELDS REGION These notes were adapted from course field-trip notes. While not specifically written for the conference field trip to the Columbia Icefield, they will still give participants a good general overview of the features of the region. Summary These field notes give a brief overview of the climatological and glaciological setting of the Athabasca Glacier and Columbia Icefields region. During the visit we will focus on the climate, physical environment, and glacial history in the area, with emphasis on glacier advance and retreat during the Little Ice Age and 20th century. Sections 1-3 briefly outline the climatological and glaciological points that we will discuss at the Crowfoot Lake, Bow Summit, and Athabasca Glacier stops on the Icefields Parkway. Weather permitting, we will take some time at the Athabasca Glacier to travel on the glacier surface and in the forefield, where we will examine a number of glacial landforms. The recent demise of the Athabasca is vividly evident in the short walk from the Icefields Parkway to the terminus of the glacier. What to Bring Expect anything in October! Average October temperatures in Lake Louise are 1ºC, and precipitation is just as apt to be snow as rain. On the Icefields Parkway this means that sub-freezing temperatures are likely and snow is very possible. Bring a winter jacket, toque, gloves, and sturdy footwear. There are also glorious autumn days on the Icefields Parkway in October, so hope for the best! Good running shoes or light hikers are fine for the walking that we will do. If there is too much new snow, we will limit the hiking and do most of the discussions close to the tour bus. 1. The Columbia Icefields: Climatology A suite of climate records from Environment Canada weather stations in the Icefields vicinity is shown in Tables 1 and 2, with Calgary Airport thrown in for good measure. These are the 30-year climate normals for the period 1971-2000, with temperature data (min, max, and mean) derived from daily averages. These stations are all in valley settings, well below the elevation of the Icefields. Sunwapta Pass, which divides Jasper and Banff Parks, is at 2035 m, while the present glacier terminus is close to 2100 m and the icefall that you can see from the road is at 2700 m. The upper accumulation plateau of the Icefield extends above this to 3500 m. Despite being at too low an altitude to really tell us what is going on in the upper reaches of the Icefield, the Lake Louise and Sunwapta climate normals give some idea of the background climatic state needed to support glaciers and icefields. Mean annual Field Notes October 2003 temperatures at both sites are just below 0ºC, with average daily summer (June July, August) temperatures of close to 10ºC. With typical cooling rates of 6ºC/km in the lower troposphere, one can approximate mean annual and summer temperatures of ca. −3ºC and 7ºC at Sunwapta Pass. At 3000 m, representative of the Icefield plateau, there are no long-term meteorological observations but similar extrapolation gives mean annual and summer temperatures of −9ºC and 1ºC. The latter number is key; it is cool enough for relatively little summer melt, while precipitation that falls at upper elevations is likely to be snow in most months of the year. Winter snow accumulations in Lake Louise and Sunwapta also illustrate the higher amount of snowfall in the continental divide region. The sparse vegetation on Sunwapta Pass and in the vicinity of the Athabasca Glacier gives testimony to the harsh climate in the Icefields region. The Columbia Icefield straddles the continental divide, providing a relatively smooth passage for nasty wet B.C. weather systems that bring low clouds and precipitation. Average annual snow accumulations of ca. 7 m (water equivalent) are typical on the Icefield. It can snow in any month of the year; in fact, there were several snowfalls on the Icefield this past August. When clear skies prevail at Sunwapta Pass, the area is still buffeted by cold katabatic winds that drain through the Athabasca valley. Site Banff Calgary Jasper Lake Louise Sunwapta Elevation (m) 1383.7 1084.1 1062.2 1524 1554.5 Latitude 51˚ 11'N 51˚ 07'N 52˚ 53'N 51˚ 26'N 52˚ 27'N 115˚ Longitude 114˚ 01'W 118˚ 04'N 116˚ 13'W 117˚ 27'W 34'W Tmax (ºC) 8.9 10.5 9.2 7.0 6.8 Tmin (ºC) −2.9 −2.4 −2.6 −7.7 −7.3 Tmean (ºC) 3.0 4.1 3.3 −0.3 −0.3 Tsummer (ºC) 13.6 15.2 14.1 11.0 10.6 Total Precipitation 472.3 412.6 398.8 569.3 488.9 (mm) Rain (mm) 296.2 320.6 296.7 265.0 284.1 Snow (cm) 234.1 126.7 138.0 304.3 205.2 Winter (DJF) 106.6 48.7 79.1 164.7 92.0 Snowfall (cm) Spring (MAM) Snowfall (cm) 67.6 47.0 26.9 59.3 55.9 Table 1. Climate normals for several sites in the Canadian Rockies, derived from daily data, 1971−2000. Field Notes October 2003 Of course, this climate does offer a hospitable environment for glaciers to thrive. In fact, it is an ideal mix of cold continental and moist maritime conditions; most months of the year are cold enough for snow, while prevailing westerlies nourish the icefield with moist Pacific air masses. Summer heat can still be intense, with temperatures reaching 20ºC. This can be punishing on the outlet glaciers, which experience several m of summer melt. The net annual accumulation vs. loss of snow on a glacier is known as its mass balance. The mass balance is key to determining whether a glacier will grow or shrink in a given year. Studies relating regional meteorological data with long-term mass balance observations on the Peyto Glacier, an outlet of the Wapta Icefield, indicate a strong correlation between summer temperature and annual mass balance (Young, 1981; Yarnal, 1984). It has long been thought that summer temperatures are the primary control of glacier health in the Rockies, typical of continental climates. As discussed in a bit more detail below, this view has recently been questioned thanks to solid evidence of a strong maritime (North Pacific) influence on mass balance in the Rockies. Lake Louise, AB (1524 m) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year T (°C) −13.8 −10.2 −5.4 0.5 5.6 9.4 12.0 11.6 6.8 1.0 −7.9 −13.7 −0.3 R (mm) 0.1 0.0 2.3 5.7 35.9 53.5 57.3 54.3 39.4 15.2 1.3 0.0 265.0 S (cm) 52.9 40.2 33.2 19.7 6.4 0.3 0.0 0.0 3.2 20.0 56.9 71.6 304.3 P (mm) 53.0 40.2 35.4 25.4 42.3 53.8 57.3 54.3 42.5 35.2 58.2 71.6 569.3 Sunwapta, AB (1555 m) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year T (°C) −12.3 −2.1 −5.1 0.7 5.7 9.3 11.4 11.0 6.4 0.9 −7.9 −12.9 −0.3 R (mm) 0.0 0.0 0.0 3.3 27.3 57.2 67.4 70.3 38.6 17.2 2.7 0.0 284.1 S (cm) 30.9 24.6 28.2 20.6 7.1 1.3 0.3 0.0 3.9 18.1 33.6 36.5 205.2 P (mm) 30.9 24.6 28.2 23.6 34.4 58.6 67.7 70.3 42.5 35.3 36.2 36.5 488.9 Jasper, AB (1061 m) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year T (°C) −9.8 −6.3 −1.2 4.3 9.1 12.8 15.0 14.5 9.8 4.5 −4.0 −9.2 3.3 R (mm) 4.5 2.8 5.1 12.0 28.7 54.7 60.1 59.0 35.9 22.1 8.3 3.4 296.7 S (cm) 30.5 18.3 16.9 8.6 1.4 0.3 0.0 0.2 1.9 8.0 21.6 30.3 138.0 P (mm) 26.9 16.0 17.6 18.8 29.9 55.0 60.1 59.1 37.3 28.7 24.5 24.8 398.8 Table 2. Monthly climate normals at Lake Louise, Sunwapta, and Jasper, 1971-2000 data. Temperature data represents monthly averages and rainfall (R), snowfall (S), and precipitation (P) represent monthly totals. Figure 1 illustrates the 20th century mean-annual temperature trend in Banff, Alberta, based on Environment Canada observations that date to 1894. With the exception of recent winter temperatures, it is difficult to visually detect trends in this plot. Indeed, available meteorological records from the Canadian Rockies do not indicate as much 20th century warming as is seen elsewhere in Canada (e.g., the MacKenzie Valley). However, it is also a matter of perspective; Field Notes October 2003 20th century warming in Banff is of order 0.7ºC and is difficult to detect due to the fact that interannual variability is greater than this. The 1990s are telling, however, as seen in Table 3.