Ice shelf-ocean interactions in a general circulation model : melt-rate modulation due to mean flow and tidal currents

• Main Author: Dansereau, Véronique
• Other Authors: Patrick Heimbach., Woods Hole Oceanographic Institution., Joint Program in Physical Oceanography, Woods Hole Oceanographic Institution, Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
• Format: Thesis
• Language: English
• Published: Massachusetts Institute of Technology 2012
• Subjects: Joint Program in Physical Oceanography; Earth; Atmospheric; and Planetary Sciences; Woods Hole Oceanographic Institution; Ocean circulation; Ocean currents; West Antarctica; Antarc*; Antarctica; Ice Shelf; Pine Island
• Online Access: http://hdl.handle.net/1721.1/78549

Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012. Cataloged from PDF version of thesis. Includes bibliographical references (p. 121-123). Interactions between the ocean circulation in sub-ice shelf cavities and the overlying ice shelf have received considerable attention in the context of observed changes in flow speeds of marine ice sheets around Antarctica. Modeling these interactions requires parameterizing the turbulent boundary layer processes to infer melt rates from the oceanic state at the ice-ocean interface. Here we explore two such parameterizations in the context of the MIT ocean general circulation model coupled to the z-coordinates ice shelf cavity model of Losch (2008). We investigate both idealized ice shelf cavity geometries as well as a realistic cavity under Pine Island Ice Shelf (PIIS), West Antarctica. Our starting point is a three-equation melt rate parameterization implemented by Losch (2008), which is based on the work of Hellmer and Olbers (1989). In this form, the transfer coefficients for calculating heat and freshwater fluxes are independent of frictional turbulence induced by the proximity of the moving ocean to the fixed ice interface. More recently, Holland and Jenkins (1999) have proposed a parameterization in which the transfer coefficients do depend on the ocean-induced turbulence and are directly coupled to the speed of currents in the ocean mixed layer underneath the ice shelf through a quadratic drag formulation and a bulk drag coefficient. The melt rate parameterization in the MITgcm is augmented to account for this velocity dependence. First, the effect of the augmented formulation is investigated in terms of its impact on melt rates as well as on its feedback on the wider sub-ice shelf circulation. We find that, over a wide range of drag coefficients, velocity-dependent melt rates are more strongly constrained by the ...