Grantee Research Project Results

Constraining Oceanic Circulation and Basal Melting Rates Beneath Ice Shelves

EPA Grant Number: F6E21111
Title: Constraining Oceanic Circulation and Basal Melting Rates Beneath Ice Shelves
Investigators: Little, Christopher
Institution: Princeton University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2006 through September 1, 2009
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2006) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Fellowship - Physical Oceanography , Fellowship - Climatology , Climate Change

Objective:

I intend to constrain the magnitude and spatial distribution of melting of continental ice sheets at the ocean-ice interface. Initially, I will isolate key dynamic controls on ocean circulation using idealized numerical models. As the ice-shelf and ocean physics incorporated into the model approach a realistic representation of the interface, my research will probe the mechanisms by which advected heat drives basal melting, including tides, winds, and open ocean dynamics.

My overarching goals are to understand the factors controlling the location and rate of basal melting, as well as its sensitivity to changed oceanic conditions, and its influence on ice shelf/sheet stability, oceanic freshwater balance, and global climate.

Approach:

I will rely primarily on a numerical ocean model (the Hallberg Isopycnal Model) to describe the transport and mixing of water masses and heat. I have divided my research into four phases (see table), in which the complexity of the model and the physical processes it represents are incrementally increased.

Phase	Key Process Investigated	Key Variables	Model Configuration
I	Topographic control Role of eddies	Layer topography Viscous parameterization	Surface pressure field Two layers
II	Vertical boundary layers Buoyant plumes	Boundary layer thickness Vertical viscosity	Ice-ocean frictional interface Additional isopycnal layers
III	Melt rate	Melt/freeze parameterization	Thermodynamically active ice-ocean interface
IV	Ocean/climate change analyses	Temporally and spatially variable forcing	Ice shelf front Buoyancy/wind/tidal forcing

Expected Results:

Initial experiments indicate that large-scale topographic features drive dramatic changes in meridional boundary currents (which supply the vast majority of melt-producing water). Current experiments add additional isopycnal layers, illuminating the role of top and bottom boundary layers in the mass transport of dense and light water plumes. The location and strength of these flows exerts a strong influence on the cavity circulation as a whole. A preliminary analysis implies that the circulation is sensitive to melt rate, the slopes of the ice shelf and ocean floor, and stratification, viscosity, and thickness of the boundary layers. It is likely that the addition of thermodynamic feedbacks (freshwater input from ice melt, ocean mixing and dissipation, and meltwater stabilization) will result in a nonlinear response to changes in advected heat.

Supplemental Keywords:

oceanography, Antarctica, ice shelves, ice sheet, cryosphere, numerical model, isopycnal coordinate, climate, sea level rise,, RFA, Air, Scientific Discipline, Atmosphere, Air Pollution Effects, climate change, Environmental Monitoring, circulation model, ecosystem impacts, Global Climate Change, hydrologic models, aquatic ecology, continental ice sheets

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.