Researchers have assembled an unparalleled view of the Ross Ice Shelf, its structure, and how it has been changing over time as part of a three year, multi-institutional data collection survey of Antarctic ice. The ROSETTA-Ice team published the study in Nature Geoscience whey they detail how they discovered an ancient geologic structure that restricts where ocean water flows. The discovery suggests that local ocean currents may play a crucial role in the ice shelf's ultimate retreat.
While ice shelves are massive expanses of floating ice, they also slow down the flow of Antarctic ice into the ocean. ROSETTA-Ice collected data from the massive Ross Ice Shelf aid the slow flow of about 20 percent of Antarctica's grounded ice into the ocean, an equivalent of 39 feet of global sea level rise. At present, Antarctica's ice is melting at an accelerating rate. As the planet continues to warm, predicting how the ice shelf will require understanding the complex ways in which the ice, ocean, atmosphere, and geology interact with each other.
Like explorers making their ways into a new planet for the first time, the multidisciplinary ROSETTA-Ice team approaches the Ross Ice Shelf to gain a better understanding of these processes. The researchers faced the critical challenge of how to gather data from a region the size of Spain, and where ice that is frequently more than a thousand feet thick prevents more traditional ship-based surveys of the seabed.
The team found the solution in IcePod, a first-of-its-kind system designed to collect high-solution data across the polar regions. Columbia University's Lamont-Doherty Earth Observation developed the IcePod and mounted on a cargo plane. Its instruments measure ice self height, thickness and internal structure, and the magnetic and gravity signal of the underlying rock.
Anytime the researchers flew across the ice shelf, the IcePod's magnetometer (which measures the magnetic field of the Earth) showed a low and almost unchanging signal. That is, until halfway across the ice shelf, when the instrument came alive, displaying significant variations, much like the heartbeat on a cardiogram. After mapping out their results, it became clear to the team that this "heartbeat" always appeared in the middle of the ice shelf, identifying a previously unmapped segment of the geologic boundary between East and West Antarctica.
With the help of the IcePod's measurements of Earth's gravity field, the researchers model the shape of the sea floor beneath the ice shelf. The lead author of the study and the Lamont research scientist who led all three field expeditions, Kirsty Tinto, explained that they could see that the geological boundary was making the seafloor on the East Antarctic side much deeper than the West, and that affects the way the ocean water circulates under the ice shelf.
The results of the research, overall, indicate that models used to predict Antarctic ice loss in future climates must consider changing local conditions near the ice front, not just the large-scale changes in the circulation of warm deep water.