Matthew J. Beedle

Remote sensing and GIS technology in the Global Land Ice Measurements from Space (GLIMS) Project

Global Land Ice Measurements from Space (GLIMS) is an international consortium established to acquire satellite images of the worlds glaciers, analyze them for glacier extent and changes, and to assess these change data in terms of forcings. The consortium is organized into a system of Regional Centers, each of which is responsible for glaciers in their region of expertise. Specialized needs for mapping glaciers in a distributed analysis environment require considerable work developing software tools: terrain classification emphasizing snow, ice, water, and admixtures of ice with rock debris; change detection and analysis; visualization of images and derived data; interpretation and archival of derived data; and analysis to ensure consistency of results from different Regional Centers. A global glacier database has been designed and implemented at the National Snow and Ice Data Center (Boulder, CO); parameters have been expanded from those of the World Glacier Inventory (WGI), and the database has been structured to be compatible with (and to incorporate) WGI data. The project as a whole was originated, and has been coordinated by, the US Geological Survey (Flagstaff, AZ), which has also led the development of an interactive tool for automated analysis and manual editing of glacier images and derived data (GLIMSView). This article addresses remote sensing and Geographic Information Science techniques developed within the framework of GLIMS in order to fulfill the goals of this distributed project. Sample applications illustrating the developed techniques are also shown.

Glacier Water Resources on the Eastern Slopes of the Canadian Rocky Mountains

Maps of glacier area in western Canada have recently been generated for 1985 and 2005 (Bolch et al., 2010), providing the first complete inventory of glacier cover in Alberta and British Columbia. Western Canada lost about 11% of its glacier area over this period, with area loss exceeding 20% on the eastern slopes of the Canadian Rockies. Glacier area is difficult to relate to glacier volume, which is the attribute of relevance to water resources and global sea level rise. We apply several possible volume-area scaling relations and glacier slope-thickness relations to estimate the volume of glacier ice in the headwater regions of rivers that spring from the eastern slopes of the Canadian Rocky Mountains, arriving at an estimate of 55 ± 15 km3. We cannot preclude higher values, because the available data indicate that large valley glaciers in the Rocky Mountains may be anomalously thick relative to what is typical in the global database that forms the basis for empirical volume-area scaling relations. Incorporating multivariate statistical analysis using observed mass balance data from Peyto Glacier, Alberta and synoptic meteorological conditions in the Canadian Rockies (1966–2007), we model future glacier mass balance scenarios on the eastern slopes of the Rockies. We simulate future volume changes for the glaciers of the Rockies by using these mass balance scenarios in conjunction with a regional ice dynamics model. These projections indicate that glaciers on the eastern slopes will lose 80–90% of their volume by 2100. Glacier contributions to streamflow in Alberta decline from 1.1 km3 a−1 in the early 2000s to 0.1 km3 a−1 by the end of this century.

Validation of high-resolution GRACE mascon estimates of glacier mass changes in the St Elias Mountains, Alaska, USA, using aircraft laser altimetry

We acquired center-line surface elevations from glaciers in the St Elias Mountains of Alaska/northwestern Canada using aircraft laser altimetry during 2000-05, and compared these with repeat measurements acquired in 2007. The resulting elevation changes were used to estimate the mass balance of 32 900 km 2 of glaciers in the St Elias Mountains during September 2003 to August 2007, yielding a value of -21.2±3.8Gta -1 , equivalent to an area-averaged mass balance of -0.64±0.12 m a -1 water equivalent (w.e.). High-resolution (2 arc-degrees spatial and 10 day temporal) Gravity Recovery and Climate Experiment (GRACE) mass-balance estimates during this time period were scaled to glaciers of the St Elias Mountains, yielding a value of -20.6 ± 3.0 Gt a -1 , or an area-averaged mass balance of -0.63 ± 0.09 m a -1 w.e. The difference in balance estimates (altimetry minus GRACE) was -0.6 ± 4.8 Gta -1 , well within the estimated errors. Differences likely resulted from uncertainties in subgrid sampling of the GRACE mass concentration (mascon) solutions, and from errors in assigning an appropriate near-surface density in the altimetry estimates. The good correspondence between GRACE and aircraft altimetry data suggests that high-resolution GRACE mascon solutions can be used to accurately assess mass-balance trends of mountain glacier regions that are undergoing large changes.

Blowing Snow Fluxes in the Cariboo Mountains of British Columbia, Canada

Abstract The Cariboo Mountains form the northern extension of the Columbia Mountains, spanning a distance of about 300 km in central British Columbia (BC), Canada. Cool air temperatures, abundant snowfall, and strong winds (especially above treeline and along exposed ridges) would suggest frequent and intense blowing snow events. The occurrence of intense blowing snow episodes is confirmed by automated wind and snow depth measurements at several sites in the area. Simulations conducted with a numerical model forced by meteorological observations recorded from 2006 to 2009 reveal a high frequency of blowing snow episodes at three high-elevation sites in the Cariboo Mountains. This process is especially prominent on the exposed ridge of Browntop Mountain (elevation of 2031 m a.s.l.) where snow transport by wind is calculated to occur as much as two-thirds of the time during some winter months. Simulated blowing snow fluxes remain high at this site with monthly transport and sublimation rates reaching 5301 Mg m−1 and 31 mm snow water equivalent (SWE), respectively. Blowing snow is also shown to be a dominant process in snow accumulation at the upper Castle Creek Glacier site (elevation of 2105 m a.s.l.), with strong winds generating sharp declines in snow depth and the erosion of more than 200 cm of snow depth during two successive winters. The results presented in this study suggest that blowing snow contributes significantly to snow accumulation and the mass balance of glaciers in BCs Cariboo Mountains.

Glacier change in the Cariboo Mountains, British Columbia, Canada (1952–2005)

We applied photogrammetric methods with aerial photography from 11 different years between 1946 and 2005 to assess changes in area and volume of 33 glaciers in the Cariboo Mountains of British Columbia for the latter half of the 20th century. These are used to identify changes in extent and elevation primarily for the periods 1952–1985, 1985– 2005, and 1952–2005. All glaciers receded during the period 1952–2005; area retreat averaged −0.19± 0.05 % a. From 1952 to 1985, nine glaciers advanced; following 1985, retreat rates accelerated to −0.41± 0.12 % a. Thinning rates of a subset of seven glaciers likewise accelerated, from −0.14± 0.04 m w.e. a (1952–1985) to −0.50± 0.07 m w.e. a for the period 1985–2005. Temperatures increased from the earlier to the latter period for the ablation (+0.38 C) and accumulation (+0.87 C) seasons, and average precipitation decreased, particularly in the accumulation season (−32 mm, −3.2 %). Our comparison of surface area change with glacier morphometry corroborates previous studies that show primary relations between extent change and surface area. We also find that the strength and sign of these relations varied for different epochs. Our results also indicate that the 1985 glacier extent for the study area reported previously by other studies may be slightly overestimated due to errant mapping of late-lying snow cover.

Quality in the GLIMS Glacier Database

Global Land Ice Measurements from Space (GLIMS) is an international initiative to map the world’s glaciers and to build a geospatial database of glacier vector outlines that is usable via the World Wide Web. The GLIMS initiative includes glaciologists at 82 institutions, organized into 27 Regional Centers (RCs), who analyze satellite imagery to map glaciers in their regions of expertise. The results are collected at the U.S. National Snow and Ice Data Center (NSIDC) and ingested into the GLIMS Glacier Database. A concern for users of the database is data quality. The process of classifying multispectral satellite data to extract vector outlines of glaciers has been automated to some degree, but there remain stages requiring human interpretation. To quantify the repeatability and precision of data provided by different RCs, we designed a method of comparative image analysis whereby analysts at the RCs and NSIDC could derive glacier outlines from the same set of images, chosen to contain a variety of glacier types. We carried out four such experiments. The results were compiled, compared, and analyzed to quantify inter-RC analysis consistency. These comparisons have improved RC ability to produce consistent data, and in addition show that in the lower reaches of a glacier, precision of glacier outlines is typically 3 to 4 pixels. Variability in the accumulation area and over parts of the glacier that are debris covered tends to be higher. The ingest process includes quality control steps that must be passed before data are accepted into the database. These steps ensure that ingested data are well georeferenced and internally consistent. The GLACE experiments and ingest time quality control steps have led to improved quality and consistency of GLIMS data. This chapter presents the GLACE experiments and the quality control steps incorporated in the data ingest process. More recent similar studies are referenced.

Multispectral image analysis of glaciers and glacier lakes in the Chugach Mountains, Alaska

The Chugach Mountains contain the largest nonpolar alpine glaciers in the world and include a wide variety of glacier types: some are land terminating; some calve variously into tidewater, lakes, and rivers; some are heavily debris covered; some are surge-type, whereas others are neither debris covered nor surge type. Nearly all are retreating, thinning, or both, though some rare ones are advancing, and some are thickening at high elevations. To assist the further documentation of changes, we establish an inventory of glaciers in the eastern Chugach Mountains. Several case studies of diverse glacier types showcase remotesensing applications and are used to derive new knowledge of their current states and dynamical behavior. Several of these glaciers currently discharge into the Copper River and can be used to understand the processes governing glacier damming of large rivers. The Copper River, along with other major valley outlets from the Copper River Basin, was dammed several times by ice during the Pleistocene, forming a lake 10,000–20,000 km2 in area, called Glacial Lake Ahtna. Insights from the modern Childs, Miles, and Allen Glaciers—each of which fronts the Copper River—show that damming is not easily accomplished; direct encroachment, complete crossing, and successful damming require very low river discharge and probably introduction of abundant rock debris from a landslide onto the glacier. The last century has involved degradation of the Little Ice Age piedmont lobes of many valley glaciers in the Chugach Mountains and especially its Copper River corridor. These glaciers are generally losing over a meter per year of surface elevation. In another chapter highlight, we have found that crenulation and chevron folding of medial moraines does not require surging, as is commonly assumed; rather, the deformation can occur by flow diversion, without any surge activity, into ice-marginal lakes—a process we term a glacial aneurysm.