TRANSPORT OF SUSPENDED PARTICULATE MATERIAL BY ICE SHELF WATER COLD TONGUES: A NEW OBSERVATION FROM THE SPILLANE FJORD (CRANE GLACIER), ANTARCTICA

Following the collapse of the Larsen B ice shelf in 2002, the Crane Glacier receded into its bedrock valley along the Oscar II coast, exposing a fjord approximately 16km long, up to ~5.5 km wide, and over 1200m deep. The calving line was observed to be afloat in water depths exceeding 1250m. The grounding line lies at least several hundred meters in from the calving front, in deeper water. This produces a cavity in which ice shelf water can form. In April 2006, we evaluated the physical oceanography of this fjord and described ice shelf water cold tongues as a mechanism of suspended particulate material transport. Bottom melting of ice shelves leads to supercooled tongues of ice shelf water, which migrate out into the fjord. These cold tongues carry a load of suspended particulate material. We used data from five vertical profiles of temperature, conductivity, and transmissivity in and around the fjord trough. Filtration and grain size analysis were performed on 17 collected water samples. These measurements ensure that light transmittance was not affected by frazil ice, an important consideration in -2.0ºC seawater. Particulate matter from the cold tongues was also analyzed for grain size via laser diffraction along with a scanning electron microscope examination, to check for grain shape and composition. This evaluation includes volume of SPM and rate of transport along with comparisons between ISW transport and other common processes of sediment transport in fjords, such as ice rafting and estuarine circulation. This process may be more important than previously thought due to the lack of observed data deep within sub-ice shelf cavities.