Date of Award

12-2013

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Interdisciplinary Program

Advisor

Gordon S. Hamilton

Second Committee Member

Emmanuel S. Boss

Third Committee Member

Jason E. Box

Abstract

Water frequently coexists with ice on glaciers and ice sheets where water can be found under, within, and on the surface of the ice. This dissertation is concerned with measuring the volume and extent of surface meltwater, and with the effects of ocean water beneath floating ice. Geographically, the investigations are focused on a marine-terminating glacier in southeastern Greenland, Helheim Glacier, a large outlet glacier with a floating ice tongue in northeastern Greenland, Nioghalvfjerds- fjorden (79N), and a large area of perennial landfast ice known as the Norske 0 (island) Ice Barrier (N0IB) in front of 79N. None of these places are very accessible; Helheim is the most easily reached but only relative to significant difficulties of reaching 79N so using satellite data to study these areas is an effective alternative to physically going to them.

However, to test a depth-finding algorithm previously developed required in situ measurements of a melt pond. Those measurements were made in July, 2008 on Helheim Glacier. An anaylsis of the data found the method to be reasonably accurate, ±0.5 m, and that the required assumptions had little impact on the derived depth.

Data from three regional weather stations in Northeast Greenland indicate that summers have warmed between 1986 and 2013. The area-averaged, annual surface melting rate on the 79N ice tongue has increased by ~40% and the basal melting rate has increased by ~35% between 1996-1998 and 2010-2012. There is evidence that ocean waters circulating beneath the ice tongue have warmed during the last 10-15 years and have caused the increased basal melting which may lead to the collapse of the tongue and increased flux at the grounding line.

Once considered a semi-permanent feature, the N0IB has broken up and dispersed ten of the last thirteen summers, 2001-2005, 2008, and 2010-2013. A statistical anaylsis indicates that June surface air temperatures and regional cyclones are good predictors of the N0IB breakup. What role, if any, the warming ocean waters circulating benath the ice barrier plays in the increasingly frequent breakups remains to be determined but observations point to large-scale changes off the coast of Northeast Greenland.

Comments

Interdisciplinary Remote Sensing and Glaciology.

As of 2002, Degree of Master of Science (MS) Quaternary and Climate Studies published under the auspices of the Climate Change Institute.

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