A pair of reports in the last couple weeks has delivered bad news for future ice loss in Antarctica. One described the possibility of committing ourselves to several meters of sea level rise if ice in the Wilkes Basin were to become destabilized. The other concluded that we likely have already committed ourselves to over a meter of long-term sea level rise from a portion of the West Antarctic Ice Sheet. In both cases, the ice loss tipping points are a result of the shape of the valleys in which the glaciers sit, which deepen as you move inland, reaching below sea level.
That configuration has long been known to exist below the West Antarctic Ice Sheet, but it wasn’t thought of as a factor in Greenland. Now, a new study from some of those same researchers has revealed that Greenland, too, has a number of deep valleys that dip below sea level. That means Greenland is susceptible to larger, more rapid losses of ice than previously thought.
The topography of the land beneath an ice sheet exerts a large amount of control over the flow of the ice, yet it’s largely hidden from view. Glaciologists have long been using airborne radar surveys to determine ice depth in much the same way that sonar can measure water depth below a ship.