Date of Award

2007

Level of Access

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Sciences

Advisor

Gordon S. Hamilton

Second Committee Member

Roger LeB. Hooke

Third Committee Member

Peter O. Koons

Abstract

Ice mass from the interior of Greenland and Antarctica is transported to the ocean by numerous large, fast-flowing outlet glaciers. Changes in the flow configuration of these outlet glaciers modulate ice sheet mass balance and sea level. Several recent studies have highlighted rapid increases in glacier speed in both Greenland and Antarctica, implying that the near-term contribution to sea level from ice sheets is under-estimated by current models. Here, the mass balance and force budget of several large outlet glaciers in East Greenland and East Antarctica are investigated using remote-sensing and field-based measurements. Recent estimates show that Greenland’s contribution to sea level more than doubled in the past decade, and that the majority of this additional mass loss is due to changes in the dynamics of a few large outlet glaciers. Our measurements indicate that up to ~10% of global sea level rise over the period 2001 – 2006 was contributed by just two glaciers, Helheim and Kangerdlugssuaq, in Southeast Greenland. We also find a latitudinal pattern of glacier behavior in East Greenland, where large and rapid changes are taking place south of 70°N while glaciers north of 70°N are stable. The East Antarctic Ice Sheet is Earth’s largest source of freshwater and has the potential to raise sea level by 57 m. The dynamics of outlet glaciers draining the ice sheet through the Transantarctic Mountains are largely unknown, but the glaciers are often assumed to be stable. In this study we investigate the dynamics of four large East Antarctic outlet glaciers. Together, these glaciers drain ~1,500,000 km2, or 12% by area of the entire Antarctic Ice Sheet. Mass balance calculations show modest imbalances for some glaciers, and a large imbalance for Byrd Glacier. Observations indicate a possible recent increase in flow speed, but this is insufficient to explain the large imbalance. We argue that catchment–wide estimates of accumulation rate contain large errors. This research provides new insights into the dynamic character of ice sheet outlet glaciers. In addition to quantifying recent changes, it also provides baseline data against which future behavior can be assessed.

Files over 10MB may be slow to open. For best results, right-click and select "save as..."

Included in

Glaciology Commons

Share