Climatic and Dynamic Glacier Mass Balance Components - Ashley Van Beusekom , U.S. Geological Survey (co-authors: Shad O’Neel, Ashley Medin, Ed Josberger)

ABSTRACT

Glaciers are a key component of local, regional and global hydrological cycles, capable of rapid, sometimes unpredictable response to climate forcing. Remote sensing efforts are revealing a global trend of sustained mass loss, which is mirrored by more detailed measurements made by the USGS Water Resource Discipline’s Glacier Mass Balance Program. Our data reveal the state of health of three glaciers, and help to resolve glacier response to climate forcing.

However, direct climate forcing is not the sole control of glacier mass balance. Dynamical instabilities exist where ice flows directly into the sea and is grounded below sea level. When triggered, these instabilities manifest as order of magnitude increases in ice flux, as best documented at Alaska’s Columbia Glacier. While this condition is met at a relatively small percentage of glaciers, the instability results in dramatic ice losses in very short time periods. This instability is extremely volatile, and results in the largest uncertainty in global sea level rise. Our focus is turned to Alaska’s glaciers for two primary reasons. First, large volumes of ice are sensitively posed along the Gulf of Alaska coastline and exhibit one of the strongest responses to ongoing climate change. Second, Columbia Glacier, located in Prince William Sound, is approximately halfway through a catastrophic retreat that has been the target of intense study since its onset. Largely due to USGS efforts, Columbia Glacier has become the best-studied calving glacier on Earth, and holds great potential to elucidate physical processes that govern dynamic instability at calving glaciers around the globe.

We will present recent improvements in mass balance analysis at the USGS benchmark glaciers and discuss them in light of climate forcing. These results will be compared to recent efforts at Columbia Glacier, demonstrating the relative magnitudes of mass balance components and low level of comprehension of dynamic component.

Topic: Climate Change