New research from Leeds University in England has confirmed that the grounding lines, the point where a glacier meets the ocean, of eight of the largest ice glaciers in Antarctica are retreating at an alarming rate. This finding could have major implications for future sea levels and ocean circulations.
The new study, published Monday in Nature Geoscience, shows evidence that an area of Antarctica's submerged ice roughly the size of London melted between 2010 and 2016. In addition, the grounding lines of eight of the 65 largest glaciers in Antarctica are retreating faster than they have since the end of the last ice age. This accelerated melting is the result of warming temperatures in the Southern Ocean, Phys Org reported.
When the ice in glaciers becomes too thin to rest on the bedrock of the Antarctic continent, they float. However, ice that no longer sits on the continent will melt into the ocean. This raises sea levels across the globe. In addition, because the ice sheet in Antarctica is freshwater, this melting would change ocean circulation, as this is partially driven by changes in the oceans' salt content, lead study researcher Hannes Konrad told Newsweek.
Konrad explained that it's not that the oceans are simply getting hotter but rather that from time to time warm water from the depth of the global oceans is rising up and melting floating bits of ice.
"This seems to be driven by wind activity and could be related to the ENSO [El Niño/La Niña] phenomenon," he said.
Related: Antarctica is melting from below—and it's getting worse
Grounding lines are more or less invisible because the floating parts of the glacier and the submerged parts tend to look the same. To measure these lines, the team used the CryoSat-2, a tool from the European Space Agency designed to measure changes in ice sheet elevation. They then used measurements of known grounding line position changes over the past seven years to give them the current grounding line positions.
Related: NASA photos reveal how fast Antarctic ice sheets are melting into the Oceans
The result is the first complete map showing how the grounding line level of Antarctica's ice sheet has changed. That sheet covers an area of land larger than the U.S. and Mexico combined. In eight of the ice sheet's 65 biggest glaciers, the grounding line retreat has been extreme. This change was most apparent in West Antarctica.
However, the study also revealed that while the retreat of the grounding line in certain glaciers has sped up, in others this retreat has completely stopped. According to Konrad, this is simply further proof of how complex and unstable ice sheet behavior is.
