Thursday, January 24, 2013

Endless Feedback Loops

Two pieces of interesting reading today on the melting of the Greenland ice sheet.  First, a profile of Jason Box, a handsomely named gentleman, and his work which now focuses on the interaction between microbes and soot particles on the ice sheet and subsequent warming-induced melting.  Second, a new Nature paper (pdf) looking at Greenland ice cores and concluding that the ice sheet has survived warmer temperatures before and therefore might not be as likely to completely melt (although that means that West Antarctica could be trouble).  See also Andy Revkin's summary and colloquy with Richard Alley: click me.

All of this is qualitatively clear but quantitatively fuzzy to me.  For instance, there seem to be several feedback loops at play:

  • warmer oceans -> more glacier calving and underbelly erosion -> higher sea levels -> more glacier calving and underbelly erosion (I don't think underbelly erosion is the right term, but whatever)
  • warmer temperatures -> greater surface melt -> warmer ice -> greater surface melt
  • more surface melt pools -> lower albedo -> more warming -> more surface melt -> more surface melt pools
  • more soot particles in surface -> lower albedo -> greater ice warming -> greater melting -> greater ice warming
  • more dark microbes -> lower albedo -> greater ice warming -> greater melt ponds -> more dark microbes
...but I have no real sense of the relative contribution of each feedback loop.  And that list doesn't take into account the other climate variables that aren't loops (warmer atmospheric temperatures, faster glacier travel because of lubrication caused by melt-lake drainage, etc).  I wish someone (media or scientist) would clarify how much each of these factors impact the overall melting of the ice sheet. 

Bottom line: scientists and science media needs to do a better job using holistic models to show what's major, what's minor, and, ultimately, what matters.

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