MIGRATION OF THE FROZEN/MELTED BASAL BOUNDARY LINKED TO ~100 KILOMETERS OF ICE MARGIN RETREAT, WESTERN GREENLAND ICE SHEET

• Main Author: Stansberry, Aidan Ripley
• Format: Thesis
• Language: unknown
• Published: University of Montana 2021
• Subjects: greenland; temperature; bed; frozen melted boundary; retreat; holocene; Glaciology; Greenland; Ice Sheet
• Online Access: https://scholarworks.umt.edu/etd/11791; https://scholarworks.umt.edu/context/etd/article/12895/viewcontent/Stansberry_Aidan_Thesis.pdf

The geometry and thermal structure of western Greenland ice sheet have evolved over the last 11 kyr in response to Holocene climate. Evolution of the frozen and melted fractions of the bed associated with the ice sheet retreat over this time frame remains unclear. We address this question using a thermo-mechanically coupled flowline model to simulate a 11 kyr period of ice sheet retreat in west central Greenland. Our transient flow-line modeling includes high order stresses, thermally active bedrock, a well-informed climate that is constrained by an established record of ice margin retreat. We partition the transient heat balance into the various components driving thermal evolution of the bed. Our results show that an episode of ~100 km of terminus retreat is commensurate with only ~14 km of inward migration of the frozen/melted basal boundary. The thermally active bedrock layer acts as a heat sink, tending to slow contraction of frozen-bed conditions as the ice sheet retreats. The majority of retreat of the frozen area is associated with enhancement of the frictional and strain heating fields, which are accentuated towards the retreating ice margin. Since the bedrock heat flux in our region is relatively low compared to other regions of the ice sheet, the frozen boundary is more advanced and therefore more susceptible to marginward changes in the frictional and strain heating fields. Migration of melted regions thus depend on both geometric changes and the antecedent thermal state of the bedrock and ice, both which vary considerably around the ice sheet.