C13E-08
Modeling Subglacial Meltwater Plumes across Greenland's Outlet Glaciers: Implications for Ice-Ocean Coupling in a Warming Climate
Monday, 14 December 2015: 15:25
3009 (Moscone West)
Dustin Carroll1, Dave Sutherland1, Twila A Moon1, Benjamin Hudson2, Brice Noel3, Denis Felikson4, Ginny A Catania4, Jonathan D Nash5, Emily Shroyer5, Timothy Bartholomaus6, Leigh A Stearns7 and Michiel van den Broeke1, (1)University of Oregon, Eugene, OR, United States, (2)Applied Physics Laboratory University of Washington, Seattle, WA, United States, (3)Institute for Marine and Atmospheric Research Utrecht, Utrecht, Netherlands, (4)University of Texas at Austin, Austin, TX, United States, (5)Oregon State Univ, Corvallis, OR, United States, (6)University of Texas, Institute for Geophysics, Austin, TX, United States, (7)University of Kansas, Department of Geology, Lawrence, KS, United States
Abstract:
Meltwater accumulated on the Greenland Ice Sheet (GrIS) drains to glacier beds, often discharging into outlet glacier fjords hundreds of meters below sea level. The injection of buoyant meltwater at depth drives a turbulent plume that entrains warm bottom water as it rises along the ice face, resulting in increased submarine melt rates. Recent studies have used remotely sensed data to identify distinct seasonal flow patterns in GrIS outlet glacier dynamics, suggesting some glaciers are especially sensitive to changes at the terminus. However, we currently lack an understanding of the corresponding regional patterns in near-glacier circulation that are a first-order control on submarine melt rates and indirectly modulate the resultant estuarine exchange flow and mixing of fjord waters. In this study, we use a buoyant plume model combined with a synthesis of shipboard hydrography, moored observations, estimates of subglacial discharge, and remotely sensed data on glacier characteristics, to provide an estimate of plume properties across GrIS outlet glaciers in both time and space. We validate our model results with detailed ice-ocean measurements from neighboring outlet glacier fjords in Uummannaq Bay, west Greenland. Model and observations agree that strongly stratified fjords with deep outlet glaciers result in warm, subsurface plumes, while shallow fjords result in surface-intensified plumes that retain their cold meltwater signature. We compare these results to a high-resolution ocean model to provide an estimate of submarine melt rates during peak summer discharge. One advantage of our approach is the rapid characterization of distinct plume regimes across GrIS outlet glacier parameter space. Finally, we compare these plume regimes with characteristics of glacier behavior (ice velocity, surface elevation, terminus position), over decadal and seasonal time-scales. This comparison allows us to investigate which outlet glacier systems might be more sensitive to changes in submarine melt rates, based on their geometry and flow regime.
