South Cascade Glacier

Map showing the location of the South Cascade Glacier

Elevation Range: Approximately 1640-2300 meters
Location: Latitude: 48°21'23.00"N, Longitude: 121°3'26.65"W
Area: Late September 2007 = 1.73 km2

Terminus of South Cascade Glacier, July 2013
Terminus of South Cascade Glacier, July 2013

South Cascade Glacier located in a north-northwest facing valley near the crest of the Cascade Range in northwest Washington state. Dominated by a maritime climate, the glacier receives heavy annual precipitation, exceeding 4.5 m in places (PRISM Climate Group, 2006) and is heavily influenced by climate conditions in the Pacific Ocean (Walters and Meier, 1989). In 2007, South Cascade glacier had an area of 1.73 km2 in the 6.14 km2 South South Cascade Lake Basin. The glacier spans nearly 660 m in elevation in the steep sided basin which forms the headwaters of the South Fork of the Cascade River.

In 1959 scientists with the USGS began collecting mass balance data on South Cascade Glacier, one of four "benchmark glaciers" in the US. R Repeated point measurements at established index sites, in conjunction with local meteorology and runoff data, are used to estimate glacier-wide mass balances. These data constitute the longest continuous set of mass-balance data in North America (Josberger and others, 2007) which are used to understand glacier dynamics and hydrology, and to measure the glacier's response to climate change.

Research

South Cascade Glacier research sites and 1958/2013 extents
Seasonal mass balance has been monitored at this ablation stake site since 1957.  This stake array includes a time lapse camera and a sun-shielded temperature sensor, maintained at a constant 2m above the glacier surface.
Seasonal mass balance has been monitored at this ablation stake site since 1957. This stake array includes a time lapse camera and a sun-shielded temperature sensor, maintained at a constant 2m above the glacier surface.

In 1959 the USGS began a suite of continuous mass balance measurements at South Cascade Glacier, one of four benchmark glaciers in North America. Extensive glaciological measurements within the basin include: streamflow runoff, precipitation, air temperature, barometric pressure, snow thickness and density, ice ablation, surface speed, and surface altitude. Multiple site visits are made annually for facility maintenance, instrument repair and installation, and direct measurement of snow and ice. There are six stakes dispersed along a center transect from the terminus to the head of the glacier where measurements of ice ablation, and snow depth and density are repeated annually.

South Cascade weather station
South Cascade weather station

Meteorological observations began in 1959 with installation of temperature and precipitation instruments at several locations in the basin. At the Salix Creek and Middle Tarn gaging station air temperature is measured with thermistor-based sensors in passively ventilated radiation shields, between 3-3.5 m above the ground. At the Hut, air temperature, wind speed, and incoming solar radiation are measured about 1.5 m above the roof.

Air temperature at a constant height of 2.0 m above the glacier surface has also been collected during summer months for a portion of the period of record at South Cascade Glacier.

Liquid precipitation is measured by means of tipping bucket rain gage at Salix and Middle Tarn gaging stations. These unheated gages do not account for precipitation in the form of snow so the record of precipitation at both sites is limited to summer catch.

Current data available from the South Cascade weather station (USGS 12181110) includes:

  • Temperature, air
  • Wind direction
  • Wind speed
  • Precipitation
  • Solar Radiation

Middle Tarn gaging station
Middle Tarn gaging station

Runoff from Middle Tarn basin was computed from discharge of the South Fork of the Cascade River where it empties from Middle Tarn. Details of calculations and determination of rating curves can be found in USGS summaries of balance years.

South Cascade Glacier has retreated dramatically since the beginning of mass balance studies when the historic photo was taken in 1959.
South Cascade Glacier has retreated dramatically since the beginning of mass balance studies (1959 photo on left).

South Cascade glacier, the site of one of North America's longest glacier mass balance records, has been the focus of many facets of glacier research over the years. The world's first radio-echo sounding measurements in temperate ice were conducted on South Cascade Glacier and subglacial water flow have been studied on this glacier, among various other studies aimed at advancing the understanding glaciers. An abbreviated list of published research included in Selected Publications.

Summary of USGS monitoring program

South Cascade Glacier aerial image time-series
1928
1928
1959
1959
1979
1979
2006
2006
2014
2014

Ski tracks connect survey points on a spring survey trip at South Cascade Glacier. 5/3/2013
Ski tracks connect survey points on a spring survey trip at South Cascade Glacier. 5/3/2013
Research team installs telemetry equipment at stake P1. 5/4/2013
Research team installs telemetry equipment at stake P1. 5/4/2013
Guided by GPS navigation, researchers use a sled to carry ablation stakes and equipment between sites. 5/5/2013
Guided by GPS navigation, researchers use GPS navigation and a sled to carry ablation stakes and equipment between sites. 5/5/2013
Seasonal snow has melted, leaving this ablation stake at terminus site.
Seasonal snow has melted, leaving this ablation stake at terminus site.
A researcher traverses the terminus of South Cascade Glacier to reach the lowest ablation stake.
A researcher traverses the terminus of South Cascade Glacier to reach the lowest ablation stake.
Fieldwork in early May reveals a snow-covered landscape as researchers climb a chute on South Cascade Glacier. 5/3/2013
Fieldwork in early May reveals a snow-covered landscape as researchers climb a chute on South Cascade Glacier. 5/3/2013
Researchers traverse South Cascade Glacier.
Researchers traverse South Cascade Glacier.
Preparing to collect a snow core sample using Kovacs ice drill.  Steam drill in background is used to drill small holes for inserting ablation stakes.
Preparing to collect a snow core sample using Kovacs ice drill. Steam drill in background is used to drill small holes for inserting ablation stakes.
Recording field data at a stake site. 6/4/2011
Recording field data at a stake site. 6/4/2011