On the Getz ice shelf on west Antarctica, photographed on Nov. 5, 2017, the ice is in the process of calving from the front of the shelf, soon to become an iceberg. Credit: NASA/Jeremy Harbeck
Antarctica has lost 3 billion tons of ice in the past 25 years, and that ice loss has accelerated in the past five years.
In a new study, the most comprehensive to date of the continent’s icy status, an international group of 84 researchers analysed the data of several satellite-surveys from 1992 to 2017.
They discovered that Antarctica is currently losing ice is about three times faster than it did to 2012, climbing to a rate of more than 241 billion tonnes (219 billion tons per year. Total ice loss during the 25-year period contributed to the increase of the sea level of about 0.3 inch (about 8 millimeters), approximately 40 percent of the approximately 0.1 inch (3 mm) — has happened in the last five years. [Photos: Antarctica’s Larsen C ice shelf By the Time]
Millimeters of sea level rise may not sound like much, but the earlier surveys suggested that the Antarctic’s huge ice sheets are not likely to be affected by climate change. The new findings suggest that the continent’s ice cream, the coverage is not as resistant to global warming as once thought, and a very different picture of Antarctica’s potential contribution to rising sea levels: Consider that if all of Antarctica’s ice is melted, the resulting water could raise the sea level by approximately 190 feet (58 m), the researchers reported.
Their study, published online today (13 June) in the journal Nature Research, is one of the five Antarctic reports released at the same time. Together, the studies evaluate past and present conditions in Antarctica to determine the impact of climate change and human activities on the continent, and to develop strategies for the future of the ecology and geology.
The track of the ice
For the new study, the scientists combined data from the three types of satellite measurements to track changes in the ice over time, study co-author Andrew Shepherd, a professor of Earth observation with the School of Earth and Environment, University of Leeds in the united kingdom, told Science.
Satellites that scanned the ice with altitude, evidence is collected about the volume; a different type of satellite measurements is kept of the speed of the glacial flow into the ocean; and a third type of observation is calculated with the severity of the landmasses on the whole planet, with a weight of the ice sheets in their entirety.
On their own, each of these techniques held uncertainties; certain factors, such as variable covering of new snow on top of ice cream or changes in the rock under the can affect the satellite measurements. By looking at all of these types of measurements together, the authors of the study may have more confidence reserved data that do not represent ice cover, Shepherd explained.
“Satellite measurements tell us that the antarctic ice sheet is much more dynamic than we think,” he said.
“If you take a look at the first IPCC [Intergovernmental Panel on Climate Change] assessment report — 30 years ago, before we had satellite measurements of the polar regions — you can see that the ice caps were not expected to respond to climate change. The general consensus in the glaciology was that the ice caps could not change quickly — but that is not the case,” the Shepherd said.
In total, an estimated 3 billion tonnes of ice gone from Antarctica during the 25-year analysis period. To put that in perspective, the huge iceberg that broke off of Antarctica’s Larsen C ice shelf in July 2017 — one of the largest icebergs in history — weighed in at more than 1 trillion tons, and is about the size of the state of Delaware. [Photos: Antarctica’s Larsen C ice shelf By the Time]
The largest change in annual ice loss in West Antarctica, with an average of about 58 billion tonnes in the year leading up to 2012, then skyrocketing up to 175 billion tonnes per year in the five years ago. Meanwhile, in the Antarctic Peninsula, the annual rate of ice loss has increased from approximately 7 billion tonnes from 1992 to 2012 to 36 billion tonnes from 2012 to 2017, mainly as a result of collapsing ice shelves.
Although Antarctica is covered with ice throughout the year, the ice caps retreat and advance in yearly cycles, a pattern that has persisted for thousands of years. But evidence from the geological record, suggest that climate change is driving ice loss in Antarctica is so much faster than during the periods of ice loss in the distant past, the Shepherd told Live Science. [Sample Antarctic Iceberg Gets Its Big breakthrough in First-of-Its-Kind Video]
Old ice sheets to leave behind signs of their presence in the country covered, and this evidence is clear when retreating glaciers exposed the ground beneath them. Scientists can also detect markers of where ice sheets once covered Antarctica by looking at the seabed around the western part of the continent, which keeps track of where glaciers were pinned in the past, Shepherd explained.
These signs help researchers to determine the pace of ice retreat in Antarctica — estimate in the past about 164 feet (50 meters) each year between glacial cycles, Shepherd said. However, ice retreat today is about more than 20 times that rate — more than 3200 feet (1 kilometer) per year.
The scientists also looked for traces of organisms that live beneath the floating ice shelves of the Antarctic Peninsula, specifically on the balance between the organisms that thrive in the light and that shining in the darkness. The results showed that the ice shelves in Antarctica have been in place for about 10,000 years”, so the fact that they are on the verge of collapse today is unprecedented, and the pace of the retreat and collapse of ice shelves is many times faster than we would expect from the normal glacial cycles,” the Shepherd said.
Original article on Live Science.