Quantifying ice sheet flow characteristics



Advances have been made in describing ice sheet motion, but in situ rheology (characteristics that affect the flow) of the ice has been hard to measure in the field.Gillet-Chaulet et al. show that they can measure ice rheology and strain rates in situ using a phase-sensitive radar. They used the technique on the Greenland ice sheet to quantify the rheology there. The researchers were able to achieve sufficient resolution to measure a flow phenomenon known as the Raymond effect, in which the ice sheet shows horizontal variations of the vertical strain rate pattern, sometimes creating anticlines in radar-detected stratigraphic layers that are known as Raymond arches. This effect is due to a highly viscous plug of nearly stagnant ice under an ice ridge. The study is, the researchers believe, the first direct confirmation of the Raymond effect. Their results suggest that laboratory ice studies do not capture the full range of ice flow that exists in nature, so additional field studies are needed. (Geophysical Research Letters, doi:10.1029/2011GL049843, 2011)