School of Earth and Climate Sciences

Project Overview

Glacier and ice sheet mass balance is one of the highest impact components of climate change, due in large part to its affect on sea level. Both Greenland and Antarctica, as well as alpine glaciers, discharge primarily though streaming flow, so the dynamics of that flow is central to the overall mass balance of the cryosphere. In glaciers and ice streams, the resistance to flow at the bed is important, but equally important is the internal viscous strength of the ice near the margins. In many cases, the lateral margins support >50% of the resisting stress. At present, there is moderate to high uncertainty of the factors controlling the viscous strength of streaming ice under natural conditions. We propose a plan to measure three-dimensional velocity, temperature, and microstructural parameters on Jarvis Glacier, in the eastern Alaska Range, in order to determine the relationship among microstructure, strain rate, and the constitutive laws necessary to numerically reproduce the observed kinematics.

To do this, we will first use surface velocity measurements, knowledge of the glacier geometry derived from ground penetrating radar, and numerical modeling to identify a site for drilling. We will then collect surface-to-bed cores across lateral and vertical strain rate gradients. Velocity and temperature measurements derived from the boreholes will complement the surface measurements and allow us to produce a more sophisticated three dimensional numerical model to test rheologic sensitivity within the study area. We will compare the microstructure (e.g., grain size distribution, crystallographic fabric) in the ice cores to the in-situ and modeled velocities and temperatures.

Project Goals & Methods

• Quantify the three-dimensional glacial geometry and surface kinematics. GPR and GPS.
• Model the internal kinematics to identify lateral and vertical strain rate gradients. Elmer/Ice.
• Collect surface-to-bed cores across selected strain rate gradients.
• Measure the temperature and strain rate distribution in the core holes. Freeze-in temperature and tilt sensors in two holes and multiple measurements of an open hole.
• Characterize the microstructural changes across the gradient. Cryo-stage SEM EBSD for crystallographic orientation. Thin sections and optical pictures for grain size.
• Evaluate the sensitivity of ice kinematics to observed microstructural and thermal variation. Elmer/Ice.

Collaboration with Kimberley Rain Miner who will be using portions of the Jarvis glacier ice core for her study:

Developing a risk assessment model for release of legacy pollutants in glacial outflows
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Starting in 1950, organic pollutants in the form of pesticides and industrial byproducts were released into the atmosphere and distributed through precipitation onto alpine glaciers throughout the world. Recent abrupt climate change is increasing the melt rate of these glaciers, introducing the toxins to the watershed. While studies have demonstrated the existence of legacy pollutants within glaciated ecosystems, no one has used standard toxicological testing methods to assess the risk posed by pollutants when released in glacial outflows. Therefore, the goal of this study is to develop a framework to assess the conditions under which glacial release of persistent organic pollutants are a risk to the health of downstream communities.

Collaboration with University of Alaska: What role do glaciers play in terrestrial subarctic hydrology?