Study Finds Subglacial Water in West Antarctica Considerably More Active than Previously Observed
19.02.2007 - Other
Using NASA satellite data, a team of scientists led by research geophysicist Helen Fricker of the Scripps Institution of Oceanography detected for the first time the subtle rise and fall of the surface of fast-moving ice streams as the lakes and channels below nearly a half-mile of solid ice filled and emptied.
The study provides the first evidence that subglacial water is stored in a linked system of reservoirs underneath the ice and can move quickly into and out of those reservoirs. This activity may play a major role in controlling the rate at which ice moves off the continent.
The surface of the ice sheet appears stable to the naked eye, but because the base of an ice stream is warmer, water melts from the basal ice to flow, filling the system's "pipes" and lubricating flow of the overlying ice. This web of waterways acts as a vehicle for water to move and change its influence on the ice movement. Moving back and forth through the system's "pipes" from one lake to another, the water stimulates the speed of the ice stream's flow a few feet per day, contributing to conditions that cause the ice sheet to either grow or decay., what can influence sea level and ice melt worldwide.
MODIS, the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Aqua satellite, continuously takes measurements of broad-sweeping surface areas at three levels of detail, revealing the outline of under-ice lakes. ICESat's GLAS instrument uses laser altimetry technology to measure even the smallest of elevation changes in the landscape of an ice sheet. Together, data from both have been used to create a multi-year series of calibrated surface reflectance images, resulting in a new technique called satellite image differencing that emphasizes where surface slopes have changed.
