Modeling Ice Shelf/Ocean Interaction in Antarctica
The most rapid loss of ice from the Antarctic Ice Sheet is observed where ice streams flow into the ocean and begin to float, forming the great Antarctic ice shelves that surround much of the continent. This paper describes the different ways in which ice shelf/ocean interactions are modeled and discusses emerging directions that will enhance understanding of how the ice shelves are melting now and how this might change in the future.
While basal melting below ice shelves plays an important role in Antarctic mass loss, accessing the ocean beneath ice shelves is extremely difficult, so numerical models are invaluable for understanding the processes governing basal melting. Our review provides a concise summary of the state of the art in ice shelf-ocean modeling while pointing out directions we expect (and encourage) model developers to take in the future.
In this paper, we summarize the physics of ice shelf/ocean interactions, including the thermodynamics (boundary conditions of heat, salt and mass conservation across the ice/ocean interface) and mechanics (drag and pressure loading on the ocean from the overlying ice). We explore the current state of modeling, including both one- and two-dimensional "plume" models and fully three-dimensional models, pointing out the importance of both numerical properties, such as high horizontal resolution, and the inclusion of dominant physical processes, such as tides, in producing results consistent with observations. We point out several emerging directions in the field, including future projections of sub-ice-shelf melt rates, dynamic ice shelves and coupled ice sheet/ocean models, model intercomparison projects, a technique for exploring model sensitivity known as adjoint modeling, and modeling at scales where turbulence can be better parameterized (large-eddy simulations) or fully resolved (direct numerical simulations). We conclude that the time scales of glaciological response to ice shelf melting, and resulting ice sheet feedbacks and instabilities, could be as short as a century or two. As a result, ice/ocean interactions are now considered to be a key ingredient in century-scale climate projections, and with advances in computing power, coupling of dynamic ice sheet models with full three-dimensional ocean circulation models is now being actively pursued.