Title: A tale of two outlet glaciers: is it the best of times, or worst of times?
The Greenland Ice Sheet is sensitive to changes at its marine terminating outlet glaciers where observed fast retreat is triggered by ocean warming at depth. Specific pathways by which gyre-scale ocean temperature changes reach outlet glaciers are little known.
We present ocean fjord observations and a global ocean model to identify two 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.
David Holland graduated from Memorial University of Newfoundland with a B.Sc. in Physics and a B.A. in Mathematics in 1985. His graduate studies included a M.Sc. in Physical Oceanography in 1987 and a Ph.D. in Atmosphere-Ocean Science from McGill University in 1993. Since 1998 he has been a faculty member of the Courant Institute of Mathematical Science at New York University (NYU), becoming a full professor in 2008.
His current research focuses on gathering field data and understanding mechanisms by which significant sea level change could arise from the great ice sheets, Greenland and Antarctica, over the coming decades. A veteran of 10 years of Greenland and Antarctic field expeditions, Professor Holland continues to spend summers collecting vital information about the state of the glaciers in those regions. This data is used in improving computer modeling of the interaction of the great ice sheets with warming global ocean waters leading to more robust projections of global sea level change.
He has published more than 100 peer-reviewed articles on polar environmental science. He was awarded an NSF Career Award in 2000. He served as Director of the Center for Atmosphere-Ocean Science in the Courant Institute during 2008-2013 and since 2013 he has become the Director of the Center for Sea Level Change at NYU New York and Abu Dhabi.