Derivation and analysis of a complete modern-date glacier inventory for Alaska and northwest Canada

Abstract

ABSTRACT. We present a detailed, complete glacier inventory for Alaska and neighboring Canada using multi-sensor satellite data from 2000 to 2011. For each glacier, we derive outlines and 51 variables, including center-line lengths, outline types and debris cover. We find 86 723 km 2 of glacier area (27 109 glaciers >0.025 km 2 ), �12% of the global glacierized area outside ice sheets. Of this area 12.0% is drained by 39 marine-terminating glaciers (74 km of tidewater margin), and 19.3% by 148 lake-and river-terminating glaciers (420 km of lake-/river margin). The overall debris cover is 11%, with considerable differences among regions, ranging from 1.4% in the Kenai Mountains to 28% in the Central Alaska Range. Comparison of outlines from different sources on >2500 km 2 of glacierized area yields a total area difference of �10%, emphasizing the difficulties in accurately delineating debris-covered glaciers. Assuming fully correlated (systematic) errors, uncertainties in area reach 6% for all Alaska glaciers, but further analysis is needed to explore adequate error correlation scales. Preliminary analysis of the glacier database yields a new set of well-constrained area/length scaling parameters and shows good agreement between our area-altitude distributions and previously established synthetic hypsometries. The new glacier database will be valuable to further explore relations between glacier variables and glacier behavior.

The challenge of monitoring glaciers with extreme altitudinal range: mass-balance reconstruction for Kahiltna Glacier, Alaska

“…at the terminus to 6108 m a.s.l. near the summit of Denali (statistics from Kienholz and others, 2015), one of the greatest elevation ranges of any glacier globally.…”

“…Firn areas are located at elevations above the long-term ELA established by the NPS (1925 m a.s.l.). The Kahiltna Glacier's terminal debris cover map comes from the Alaska-wide glacier inventory compiled by Kienholz and others (2015), who derived the map using a band ratioing technique applied to Landsat 5 imagery, following a similar method as in Paul and others (2004).…”

“…Their approach derives height change rate (dh/dt) profiles from the repeat centerline data, integrates these over the full glacier hypsometry obtained from the Randolph Glacier Inventory (Pfeffer and others, 2014;Kienholz and others, 2015), and calculates a mass change estimate by means of a density assumption. Lateral extrapolation assumes no errors in the glacier hypsometries, and that the centerline elevation changes are representative of the full glacier width.…”

“…We use an outline for the Kahiltna Glacier from the Randolph Glacier Inventory v3.2 (Pfeffer and others, 2014;Kienholz and others, 2015). These outlines are derived from a mosaic of Landsat 5/7 ETM+ images from the mid-2000s using a semiautomated approach with manual adjustments to ensure that debris-covered ice is included.…”

“…Combined with a high-latitude setting and abundant precipitation, this topography gives rise to glaciers covering similarly large altitudinal ranges. Twenty-four Alaska glaciers have elevation ranges in excess of 4000 m, with a combined area of over 17 000 km 2 , or 20% of the total glacierized area in Alaska (Kienholz and others, 2015). Of these, eight glaciers totaling 11 800 km 2 in area, or 14%, have elevation ranges > 5000 m, including the Kahiltna Glacier with a span of 5844 m.…”