Antarctica’s coastal McMurdo Dry Valleys rank among the most extreme deserts on Earth. Nearby mountains block out inland ice and have left the region largely devoid of ice cover. The neighboring valleys, however, hold alpine glaciers like the Mullins and Friedman ice floes, both of which may contain some of the oldest ice on the planet. The ice is preserved beneath a layer of surface dust and rocks that can range from just a few inches to more than 2 feet thick.
Mackay et al. used radar, ice cores, mapping, and numerical modeling to study these glaciers and found that their upper reaches are largely devoid of debris. After that, thin bands of internal debris occur at regularly spaced intervals and intersect the ice surface to produce curved ridges. The authors think this pattern could hold clues to ancient climate conditions.
The researchers conclude the layers are caused by cyclical environmental changes at valley headwalls. They believe the debris layers build up on the surface during times of reduced ice accumulation, only to be buried by snow and ice when the cycle begins again. The implication is that the internal structure and surface morphology of these cold-based, debris-covered glaciers preserves a record of climate and environmental change over the last several hundred thousand years.
Cold-based debris-covered glaciers are common in Antarctica and have been reported on Mars, so the interpretation could also have important implications for climate research elsewhere. (Journal of Geophysical Research: Earth Surface, doi:10.1002/2014JF003178, 2014)
—Eric Betz, Freelance Writer
Citation: Betz, E. (2015), Glacial debris hints at ancient climate change, Eos, 96, doi:10.1029/2015EO026447. Published on 20 March 2015.