A new insight into visualizing the bottom of thousands-meter-thick ice in Antarctica and Greenland

As medical doctors look the inside of your body using X ray, glaciologists use radar to peer into the deep blue ice and its bottom interface to the rock and ocean.

Illustration

Glaciologist Kenny Matsuoka s modeling work suggests that spatial variability in the surface snow accumulation and geothermal flux, which are in general poorly known, results in a complicated pattern of the effects of the overburden ice on the radar-signal strength. Figure: Beth Tully / University of Washington

Illustration

Radio waves transmitted from the radar transmitter travel through the ice, are reflected from the ice bottom, and travel back to the radar receiver. Photo: Rene Forsberg

Radio waves transmitted from the radar transmitter travel through the ice, are reflected from the ice bottom, and travel back to the radar receiver. The strength of the radar signals back from the ice bottom has been used as a viable parameter to diagnose the bed of thousands-meter-thick ice in Antarctica and Greenland. Brighter beds include more water so that ice slips more easily, yielding a much faster response of the ice sheets to climate change.

A Norwegian Polar Institute (NPI) glaciologist, Kenny Matsuoka, conducted new theoretical work and demonstrated that the radar signals back from the ice bottom are strongly dependent on ice temperature. His modeling work suggests that spatial variability in the surface snow accumulation and geothermal flux, which are in general poorly known, results in a complicated pattern of the effects of the overburden ice on the radar-signal strength. This «side effect» has been ignored in most previous studies, but Matsuoka’s work clearly shows that accurate extraction of this side effect is critical to diagnose the bed conditions.

His finding has a significant and immediate impact on ongoing research in Antarctica and Greenland, because radar has been used to delineate subglacial lakes and wet-bed ice. The former is a premier resource of habitats isolated from other worlds for millions of years, and the latter is a controlling factor of the ice-sheet mass balance and hence the sea-level change. Kenny says “I am not arguing that all of known subglacial lakes are not real. Radar is still the most powerful tool to diagnose the bed conditions, but more rigorous data-interpretation models are crucial to draw rigorous conclusions about the least known part of our world.” He emphasizes that now several international programs are conducting airborne radar surveys in Antarctica and Greenland, and data from such campaigns should be better interpreted using the new scheme of the analytical algorithms.

His research is published by American Geophysics Union in Geophysical Research Letters on March 11th, 2011:
Matsuoka, K. (2011), Pitfalls in radar diagnosis of ice-sheet bed conditions: Lessons from englacial attenuation models, Geophys. Res. Lett., 38, L05505, doi:10.1029/2010GL046205.