Alaska: Influence of natural ice microstructure on rheology in general shear
Understanding the loss of ice from glaciers and ice sheets, and the resulting sea-level rise, is of critical importance. Both the Greenland and Antarctic Ice Sheets, as well as mountain glaciers, discharge primarily through rivers of ice; understanding what controls the type of flow that occurs in these rivers of ice is therefore central to understanding and predicting sea-level rise. Among the least-understood factors that are thought to be important in affecting ice flow is internal strength of the ice near the sides of a flowing glacier. This viscous strength, in turn, may be affected by the micro-scale structure of the ice crystals in the glacier. The investigators will examine these relationships in detail on Jarvis Glacier, in the eastern Alaska Range, with the ultimate goal of being able to represent the effects of microstructure in numerical models of glacial flow. The purpose of this project is to correlate ice microstructure with velocity gradients in order to constrain microstructural control on/feedbacks with glacial mechanics to be able to make more informed glacial models. As part of the research, surface-to-bed ice cores will be collected across lateral and vertical flow gradients, and the microstructure (e.g., grain size distribution, crystallographic fabric) in the ice cores will be compared to in-situ and modeled velocities and temperatures.
Greenland: Refreezing in the Firn of the Greenland Ice Sheet
This project will collect several shallow firn cores from the southwestern sector of the Greenland Ice Sheet to investigate the stratigraphy, density, temperature and liquid water content of the firn cover and investigate spatial and temporal variations (the latter by comparing to previous cores from the literature in some of the sites). The aim of the project is to better understand how the surface meltwater generated in the summer makes its way from its location on the ice sheet to the ocean. Two competing but not mutually exclusive theories are 1) the meltwater percolates into the ice sheet pores and is stored for a relatively long time. 2) The initial infiltrating meltwater refreezes at shallow depth in the firn, forming a hard pan that prohibits further infiltration. The project will test these two hypotheses through a combination of fieldwork, remote sensing from satellites, and modeling.
Greenland: Dynamic Observations of the Microstructural Evolution of Firn Under Load
The Greenland ice sheet is rapidly melting due to extraordinary Arctic warming. All told, the ice sheet stores enough water to raise sea level by 6 meters. How fast the ice sheet will melt is still an open question. One important factor controlling the ice sheet melt is its physical properties. In this work, the investigators will extract an 80 meter core from the Summit Station, Greenland. Working in a cold room at Dartmouth the investigators will impose the natural temperature conditions on the two ends of the near surface part of the core and compression tests on the deeper part of the core. A suite of spectroscopy techniques will be used to monitor the 3-dimensional real-time densification of the core and the evolution of the crystal orientation. These experiments will provide the values of the numerous physical parameters required for simulation modeling, which will be used to determine the melt rates over the coming decades.
Greenland: a Greenland Traverse for Accumulation and Climate Studies (GreenTrACS)
This project will use a hand auger and sidewinder to drill several shallow (30 meter depth) ice cores along a traverse in western Greenland. Continuous ground penetrating radar data will also be collected during the traverse. The research objectives include: (1) determining the patterns, in time and space, of snow accumulation in Western Greenland over the past 20-40 years; and (2) evaluating surface melt refreeze and englacial meltwater storage in the Western Greenland percolation zone over the past 20-40 years.
North America: Microbes Promote Ice Formation in Inland Waters
This project involves the seasonal (winter) acquisition of cores from ice-covered northern (U.S. midwest) temperate lakes and rivers to investigate the spatial and temporal distribution of planktonic ice nucleating activity in fresh water ecosystems.
Greenland: Camp Century Monitoring Programme
The goal of this Danish-sponsored project is to drill a 100-meter core at Camp Century, Greenland, and compare its density profile to an analogous core drilled in 1967.