Geology topics

Adam Clark

Publications and source records attributed to Adam Clark.

3 recordsLinked to original sources

USGS2018

Glacier-derived August runoff in northwest Montana

The second largest concentration of glaciers in the U.S. Rocky Mountains is located in Glacier National Park (GNP), Montana. The total glacier-covered area in this region decreased by &sim;35% over the past 50 years, which has raised substantial concern about the loss of the water derived from glaciers during the summer. We used an innovative weather station design to collect in situ measurements on five remote glaciers, which are used to parameterize a regional glacier melt model. This model offered a first-order estimate of the summer meltwater production by glaciers. We find, during the normally dry month of August, glaciers in the region produce approximately 25 × 10 6 m 3 of potential runoff. We then estimated the glacier runoff component in five gaged streams sourced from GNP basins containing glaciers. Glacier-melt contributions range from 5% in a basin only 0.12% glacierized to >90% in a basin 28.5% glacierized. Glacier loss would likely lead to lower discharges and warmer temperatures in streams draining basins >20% glacier-covered. Lower flows could even be expected in streams draining basins as little as 1.4% glacierized if glaciers were to disappear.

Montana↗

USGS2017

Glaciological measurements and mass balances from Sperry Glacier, Montana, USA, years 2005–2015

Glacier mass balance measurements help to provide an understanding of the behavior of glaciers and their response to local and regional climate. In 2005 the United States Geological Survey established a surface mass balance monitoring program on Sperry Glacier, Montana, USA. This project is the first quantitative study of mass changes of a glacier in the US northern Rocky Mountains and continues to the present. The following paper describes the methods used during the first 11 years of measurements and reports the associated results. From 2005 to 2015, Sperry Glacier had a cumulative mean mass balance loss of 4.37 m w.e. (water equivalent). The mean winter, summer, and annual glacier-wide mass balances were 2.92, −3.41, and −0.40 m w.e. yr −1 respectively. We derive these cumulative and mean results from an expansive data set of snow depth, snow density, and ablation measurements taken at selected points on the glacier. These data allow for the determination of mass balance point values and a time series of seasonal and annual glacier-wide mass balances for all 11 measurement years. We also provide measurements of glacier extent and accumulation areas for select years. All data have been submitted to the World Glacier Monitoring Service and are available at doi:10.5904/wgms-fog-2016-08 . This foundational work provides valuable insight about Sperry Glacier and supplies additional data to the worldwide record of glaciers measured using the glaciological method. Future research will focus on the processes that control accumulation and ablation patterns across the glacier. Also we plan to examine the uncertainties related to our methods and eventually quantify a more robust estimate of error associated with our results.

Montana↗

USGS2016

Case study: 2016 Natural glide and wet slab avalanche cycle, Going-to-the-Sun Road, Glacier National Park, Montana, USA

The Going-to-the-Sun Road (GTSR) is the premier tourist attraction in Glacier National Park, Montana. The GTSR also traverses through and under 40 avalanche paths which pose a hazard to National Park Service (NPS) road crews during the annual spring snow plowing operation. Through a joint collaboration between the NPS and the U.S. Geological Survey (USGS), a forecasting program primarily dealing with wet snow avalanche problems serves to aid worker safety. The objective of this case study is to examine the meteorological metrics and snowpack characteristics leading up to a noteworthy wet slab and glide avalanche cycle that occurred 16-22 April, 2016 during a period of unseasonably warm and sunny weather. Continuous above freezing temperatures at upper elevations with daily maximum values reaching 10-15° C persisted for four days. The nearby Flattop Mountain SNOTEL station reported a steady loss of SWE of approximately 1.25 cm/day. River height and discharge on the Middle Fork of the Flathead River (app. 20-35 km away from starting zones) increased from 1.26 m and 139.60 m3/s (4930 cfs), respectively, on April 18 to 1.69 m and 267.59 m3/s (9450 cfs) on April 22. The ensuing avalanche cycle began with three small glide avalanches on 17 April and culminated in three large wet slab avalanches that released on wet, basal facets. These wet slabs were triggered by glide avalanches releasing above and cascading over cliffs. Four of these avalanches crossed plowed sections of the road, resulting in a three day delay in plowing operations. Finally, this specific case was compared to previous statistical models for wet snow avalanches in this transportation corridor. Out of 12 avalanche days, the model correctly predicted six of those days as avalanche days. This case study allowed for a greater understanding of a wet slab and glide avalanche cycle that occurred during a prolonged spring warming event and can serve as a reference for future similar cycles.

Conference Paper↗