What is it about?

Each summer, water melts at the top surface of Greenland glaciers, and some of it trickles into crevasses, where it refreezes. This warms and softens the ice, leading to faster ice flow -- just as it is easier to squeeze out warm honey than cold honey -- and thus higher sea levels. However, we show here that this refreezing process is virtually absent in the fast-moving glaciers that contribute >60% of ice flow from Greenland into the ocean. Thus, other processes are likely more important in determining sea-level rise from Greenland.

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Why is it important?

The recent IPCC report (a 2013 summary of current climate science) identified this mechanism (cryo-hydrologic warming) as an important unknown in how Greenland glaciers will respond to a warming climate. Our work constrains the influence that refreezing water will have on global sea level. It is important to note that our work DOES NOT indicate that Greenland glaciers are "safe" from climate change. Other mechanisms (warm ocean water, loss of ice shelves, warmer air temperatures) will continue to lay waste to the ice; we simply assert that our studied mechanism will have less influence than these others.

Perspectives

Field measurements of meltwater that refreezes in certain Greenland glaciers are quite striking -- they show substantially warmer ice that does flow faster, just like warm honey. But in other Greenland glaciers, this does not occur. I wanted to combine these field measurements (taken by others) and physically based numeric model results (my own) to add perspective to how refreezing meltwater is likely to affect the health of all Greenland glaciers, not just areas here and there that have been studied directly.

Kristin Poinar
NASA Goddard Space Flight Center

Read the Original

This page is a summary of: Englacial latent-heat transfer has limited influence on seaward ice flux in western Greenland, Journal of Glaciology, October 2016, Cambridge University Press, DOI: 10.1017/jog.2016.103.
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