The old rocky structure at the heart of the Ice Shelf Ross helps determine where Antarctic ice is melting and where the ice remains solid and frozen.
This structure is an ancient tectonic boundary that may have formed during or immediately after the birth of the Antarctic continent. According to a new study published on May 27 in the journal Nature Geoscience, this barrier protects the tip of the earth from chunks of ice, the point where it is thick enough to extend the seabed. The geology created by the border keeps warm and melting sea water from this part of the shelf. However, the ocean circulation, led by the same geology, caused summer destruction on the eastern edge of the shelf.
“We can see that the geological boundaries make the East Antarctic hand seafloor much deeper than the West, and this affects the way seawater circulates among ice masses,” said study leader Kirsty Tinto, a researcher at Lamont-Doherty Earth at Columbia University observatory , he said in a statement.
Ross Ice Shelf
Ross Ice Shelf is an ice surface covering 185,000 square miles (480,000 square kilometers) and hundreds of feet thick. Ice flows from the Eastern and Antarctic terrestrial ice shields to the shelves. Today, ice cages, Tinto and his colleagues write in Nature Geoscience, but geological and marine records show that they collapsed in the past.
To understand the dynamics of ice sheet, Tinto and his colleagues used data from an aviation instrument called IcePod, which contains tools that collect information about the thickness and structure of ice sheets, as well as devices that detect under magnetic ice sheets and rock anomalies. Magnetic minerals such as those found in magma and other aggregates in Antarctica can alter magnetic field readings in locations such as underwater topography that can affect gravity measurements. Using this data, the researchers reconstructed a map of ice and rock shelves underneath.
They found that the transition zone was divided into layers of ice. If Antarctica is a wheel, the border will look like talking from a point outside the center. This transitional area is actually the border between West Antarctic and East Antarctic geology. Western rock is a sedimentation and magmatic combination formed by tectonic interactions in the mouth of the ocean and tectonic plates. East Antarctica is an ancient continental material known as Canton.
The newly discovered tectonic boundary that divides the Ross shelf is important because it helps form the seafloor under the ice. In the east, the sea floor is deeper with an average of 690 meters. In the west, the average depth is 560 meters.
The researchers used computer models to show how seawater circulated because of these new geological findings. The good news is that the geometry of the seafloor saves the warmest sea water on Ross Ice Shelf. Instead, the coastal area called the Pollina Shelf Ross absorbs heat, deep sea water, cools it before it can flow under the ice shelf. But on the front edge of the ice shelf (where the sea meets), a lot of ice melts especially in summer. The highest summer melting is near Ross island on the East Antarctic side.
What does all this mean to warm Antarctica? In the near future, the earth’s line of ice (the point where it is connected to the ocean floor) must remain stable, at least in the face of moderate climate change, the researchers wrote. However, local climate change has a major influence on the melting rate of the leading edge of the chunks of ice. These variations might include reducing the decline in sea ice or reducing cloud cover, said Lori Padma, senior Earth scientist and Oregon Space Researcher and co-author of the study.
“We have found that we need to understand this local process to make reliable predictions,” Tinto said.