Satellite Imagery Reveals the Road Map for “Horizontal Ice Coring”
NASA and The Geological Survey of Denmark and Greenland (GEUS) have used high-resolution satellite imagery to push glaciologist Niels Reeh’s theory of horizontal ice coring into reality over a large area of the ice sheet.
Niels Reeh collecting ice surface samples at the Paakitsoq profile in 1994. Photo: Henrik Højmark Thomsen.
For ten years, between 1985 and 1998, Niels Reeh, a glaciologist at GEUS, travelled all around the margin of the Greenland Ice Sheet. He was trying to understand how patterns in the color of the ice visible at the ice-sheet surface were related to the age of the ice itself.
When snow falls in the center of the ice sheet, it becomes buried and turns into ice, as it descends vertically down into the ice sheet. Over time, horizontal flow brings this ice from the ice-sheet center towards its margin. Eventually, this ice will be exposed again at the ice-sheet surface in the ablation area, which is snow-free by the end of every summer.
During his decade of Greenland trips, Reeh explored the idea of a “horizontal ice core”. He found that the patterns of ice bands exposed in the snow-free ablation area could allow dating individual ice bands. Unfortunately, at the time it was difficult to map individual ice bands over large areas with oblique aerial photos from helicopter windows.