Impacts of Inverted Channels in Floating Ice Shelves on Ice Melt Rate
Melting of ice sheets from Greenland and Antarctica will lead to sea level change. It is critical that processes influencing the melt and glacier flow rates be understood and captured in models. Several Greenland and Antarctic ice shelves have deep inverted channels in the direction of ice flow and running along the underside of the ice floating over the ocean. U.S. Department of Energy researchers have developed a coupled ice-ocean model to understand the formation and evolution of submarine melt channels beneath the floating ice shelf of Greenland’s Petermann glacier. The model uses the Community Ice Sheet Model (CISM) to model the flow of grounded and floating (shelf) ice and an ocean layer (or “plume”) model to represent interaction with the underlying ocean. Melting, bedrock topography, and flow processes at the point where the glacier departs into the ocean stencils channels into the ice base as it passes by. These channels help to control and preserve the ice shelf against excessive submarine melting. The calculations revealed that warming of subsurface waters would increase submarine melting. Surprisingly, slight cooling of subsurface waters could also generate a reorganization of the submarine melt pattern and catastrophic thinning of the ice shelf. Increased discharge of (fresh) subglacial melt water at the grounding line also increases overall submarine melting through increased entrainment of relatively warm ocean waters. The study has revealed complex interactions in the ice-ocean system as well as conditions and variables that will require scrutiny and more detailed modeling in future studies.
Gladish, C.V., D. M. Holland, P. R. Holland and S. F. Price. 2012. “Ice-Shelf Basal Channels in a Coupled Ice-Ocean Model,” Journal of Glaciology 58(212), 1227-44. DOI: 10.3189/2012JoG12J003.