Sampling the ‘grounding zone’ in Antarctica
Press release issued: 22 January 2015
Using a specially designed hot-water drill to cleanly bore through a half mile of ice, a National Science Foundation (NSF)-funded team of researchers, including Professor Martyn Tranter of the University of Bristol, has become the first ever to reach and sample the ‘grounding zone’, where Antarctic ice, land and sea all converge.
Data gathered from samples of sediment taken in the grounding zone will provide clues about the mechanics of ice sheets and their potential effects on sea-level rise.
Cameras sent down the drilling hole also revealed an unsuspected population of fish and invertebrates living beneath the ice sheet, the farthest south that fish have ever been found. The surprising discovery of fish in waters that are extremely cold (-2 Celsius, 28 degrees Fahrenheit) and perpetually dark poses new questions about the ability of life to thrive in extreme environments.
The newest discoveries stem from the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project's investigation of the grounding zone of Whillans Ice Stream of the West Antarctic Ice Sheet (WAIS), roughly 850 km (530 miles) from the edge of the Ross Ice Shelf in Antarctica's Ross Sea.
Using a powerful hot-water drill developed and built by the University of Nebraska-Lincoln, researchers punched through nearly 740 metres (nearly 2,500 feet) of the Ross Ice Shelf on 8 January 2015.
On 16 January, as more than 40 scientists, technicians and camp staff were working around-the-clock to collect as many samples and data as they could while the borehole remained open, the WISSARD team deployed a Remotely Operated Vehicle (ROV) called ‘Deep SCINI’ (Submersible Capable of under Ice Navigation and Imaging) to explore about 400 square metres (4,300 square feet) of the marine cavity around the borehole.
The ROV discovered a variety of fish and invertebrates including numerous amphipods, or marine crustaceans, components of an ecosystem that may provide new insights into how creatures survive and even thrive in one of the world's most extreme environments.
Although life has been found previously under the Ross Ice Shelf, this site is the closest to the South Pole where such marine life has been documented. The southernmost ocean waters in the world are only 70 kilometres (43 miles) south, under the Ross Ice Shelf at about 85 degrees South latitude.
The grounding zone is also extremely important for the stability of the ice sheet and ice shelf. The Texas-sized Ross Ice Shelf is the world's largest floating slab of ice. Numerous streams of ice in WAIS feed into the ice shelf, like rivers flowing into a lake.
Scientists are particularly interested in the dynamics between the ice, glacial sediments and water in order to understand how the system may respond to future changes in climate. Some climate models predict warmer seawater may intrude into grounding zones and cause melting at the base of the ice shelf.
A weakening or collapse of the Ross Ice Shelf would allow ice streams of WAIS, to flow more rapidly into the ocean, which would raise global sea level.
While going down the borehole, cameras observed rich sedimentary debris in the ice. These observations, combined with data from cores of sediment collected from the sea floor and water from the marine cavity, will add significant information to the scientific questions about how the ice sheet works and interacts with sediment and ocean waters in these settings. They can perhaps provide answers to the recent past and possible future behaviour of the massive West Antarctic Ice sheet.