ROSETTA:Decoding ice, ocean and tectonic mysteries of the Ross Ice Shelf
The Ross Ice Shelf is a massive apron of ice stretching to an area of 487,000 sq. km (188,000 sq. mi) and a thickness of a few hundred meters. The edge of the ice shelf along the Ross Sea is a wall of ice towering above the water by as much as 50 m (~160 ft). However, ice shelves, like icebergs, are mainly below the waterline. This means that the majority of the shelf is not visible without the use of instruments. Our measurements tell us that at its thickest, back away from the floating edge where it is frozen to the ground below, the shelf is close to 1200 m (~4000 ft) thick. Closer to the Ross Sea where it has gone afloat it thins to less than 300 m (~1000 ft). This incredible ice feature is about the same size as the country of France and is being fed a constant flow of ice from glaciers draining from both the East and West Antarctic Ice Sheets. As new ice is added existing ice is being removed through melting at the base and ice calving at the front. Ross Ice Shelf plays a critical roll in stabilizing the Antarctic ice sheet, buttressing the ice that is constantly moving over the land surface. Studying how the ice, ocean and underlying land interact will inform us of potential change in the ice shelf from projected climate change.
ROSSETTA is a large multi-disciplinary and multi-institutional project with several major goals focused on different parts of the full ice shelf system. The project main goals include a focus on:
The Ice - Ice moves into and across the shelf at a range of speeds from 200-1000 m/yr, taking between 500 and 1000 years to travel from where it first goes afloat to where it ends at the calving edge. However evidence collected suggests that the shelf is sensitive to atmospheric and ocean variability, and can change dramatically on short time scales. Understanding this more fully is a project goal.
The Underlying Bed - The bed structure underneath the ice shelf influences ocean circulation below. Through time pre-glacial coastal erosion followed by glacial scouring has carved deepened trenches in the sediment, while the overlying ice has flattened the tops of bedrock ridges. The bed features influence the ocean circulation beneath the ice.
The Ocean - General ocean circulation, tidal currents and the overall mixing in the Ross Sea embayment, including beneath the ice shelf, are sensitive to the geology below as well as changes in the ice shelf extent and ice thickness below the ice surface.
The coupled system of ice, underlying bed and ocean interaction that is the focus of this project requires involvement from an interdisciplinary team of oceanographers, geologists, geophysicists and instrumentation engineers. The project partners include an integrated airborne team from Lamont-Doherty Earth Observatory, glaciologists from Scripps, geologists from Colorado College and oceanogrpahers from ESR. In the field we have gravimeter support from GNS and Dynamic Gravity Systems, geophysical support from U.S.G.S., air support from the New York Air National Guard and LCL productions filming the technology and airborne science.
The platform to be used in data collection is the icepod imaging system designed to collect a fully integrated dataset of ice thickness and accumulation (radar), ice surface (lidar and surface imagery). In addition two gravimeters and a magnetometer have been added to the instrument suite to identify the geology and the depth of th Ross embayment below the ice shelf.