EAS Fall 2018 Seminar Series Presents: Dr. David Holland, Center for Atmosphere Ocean Science, NYU

A Tale of Two Ice Sheets: Is it the Best of Times, or Worst of Times?

The Greenland and Antarctic Ice Sheets are sensitive to changes at their marine terminating outlet glaciers where observed fast retreat is triggered by ocean warming at depth. Specific pathways by which ocean temperature changes reach outlet glaciers are little known.  

We present ocean fjord observations and a global ocean model to identify mechanisms responsible for the variability of glacier fjord deep waters. We find that thermodynamic cooling by deep convection sets the inter-annual variability of this deep water at its source. 

Further, dynamic Ekman transport across the continental shelf break introduces intra-annual variability into this water mass.   Warm waters arriving at outlet glaciers has been argued to have caused loss or breakup of the ice shelves.  

It has been suggested that absent an ice shelf, the ocean’s role in modulating outlet glacier behavior may be diminished, here we provide evidence to the contrary.  We observe that, absent an ice shelf, intra- and  inter-annual varying ocean warm-water intrusions still lead to grounding line retreat, rapid thinning at the terminus, and speedup of a glacier.  

This response to warm-water intrusions indicates that outlet glaciers, even those without floating ice shelves, are largely sensitive to ocean temperature change.