Investigation of Multi-Decadal Uutlet Glacier Surface Ice Velocities in Greenland

• Main Author: Martin, Nathanael Raymond
• Format: Text
• Language: unknown
• Published: CU Scholar 2012
• Subjects: Glaciology; Greenland; Helheim Glacier; Jakobshavn Isbrae; Surface ice velocities; Environmental Sciences; Geography; glacier; Ice Sheet; Jakobshavn
• Online Access: https://scholar.colorado.edu/geog_gradetds/35; https://scholar.colorado.edu/cgi/viewcontent.cgi?article=1036&context=geog_gradetds

Potential impacts to the global climate system, ocean and atmospheric circulation, sea levels, and the environment from dynamic changes in recent decades to the Greenland ice sheet have brought significant attention to two of Greenland's larger outlet glaciers and fast moving ice streams, Jakobshavn Isbrae and Helheim Glacier. These changes include accelerations in surface ice velocity, and are related to a number of glaciological and physical processes, including increased calving, changes in ice stream margins, terminus retreat, and glacial thinning. While there is available data on current surface velocities for outlet glaciers in Greenland, including satellite-derived velocity measurements and ground-based observations, pre-1990 flow velocity field and structure estimates are not as widely available. This thesis study adopts a classic inventory-based approach and documents historical center-line and cross-sectional transect surface ice velocities through the analysis of pre-1990 satellite imagery. Evaluating the baseline surface ice velocity data, in combination with surface velocity estimates, qualitative assessment of imagery, and published research analyzing recent accelerations on Jakobshavn Isbrae and Helheim Glacier, enables a multi-decadal investigation into glaciological and physical change. This investigation fills in existing data gaps in the historical record of observed surface ice velocities by providing 20.0-30.0 km upstream centerline tracks of maximum surface velocity and numerous cross-sectional transects of surface velocities at Jakobshavn Isbrae and Helheim Glacier, confirms the pre-acceleration velocity structures on Jakobshavn Isbrae and Helheim Glacier, documents the changes to near-frontal surface velocity fields pre- and during, and post-acceleration, and documents multi-decadal frontal position changes of thirteen notable outlet glaciers with varying dynamics in western and eastern Greenland.