Deep seafloor troughs allow warm water to eat away at the ice from below, speeding shrinkage
Greenland is melting rapidly, but some glaciers are disappearing faster than others. A new map of the surrounding seafloor helps explain why: Many of the fastest-melting glaciers sit atop deep fjords that allow Atlantic Ocean water to melt them from below.
Researchers led by glaciologist Romain Millan of the University of California, Irvine analyzed new oceanographic and topographic data for 20 major glaciers within 10 fjords in southeast Greenland. The mapping revealed that some fjords are several hundred meters deeper than simulations of the bathymetry suggested, the researchers report online March 25 in Geophysical Research Letters. These troughs allow warmer and saltier waters from deeper in the ocean to reach the glaciers and erode them.
Other glaciers are protected by shallow sills, or raised seafloor ledges. These sills act as barriers to the deep, warm water, the new