Antarctica's Effect on Sea Level Rise in Coming Centuries
How will Antarctica's melting ice sheet affect sea level rise hundreds of years in the future? Scientists now have a more accurate model to answer this question.
There are two primary causes of global mean sea level rise - added water
from melting ice sheets and glaciers, and the expansion of sea water as it
warms. The melting of Antarctica's ice sheet is currently responsible for
20-25% of global sea level rise.But how much of a role will it playhundreds
of yearsin the future?Scientists rely on precise numerical models to answer questions like
this one. As the models used in predicting long-term sea level rise improve, so
too do the projections derived from them. Scientists at NASA's Jet Propulsion
Laboratory in Pasadena, California, have discovered a way to make current
models more accurate. In doing so, they have also gotten one step closer to understanding
what Antarctica's ice sheet - and the sea level rise that occurs as it melts -
will look like centuries from now."Unlike most current models, we
included solid Earth processes - such as the elastic rebound of the bedrock
under the ice, and the impact of changes in sea level very close to the ice
sheet," said JPL's Eric Larour, first author of the study. "We also
examined these models at a much higher resolution than is typically used - we
zoomed in on areas of bedrock that were about 1 kilometer instead of the usual
20 kilometers."The scientists found that projections for the next 100 years are within
1% of previous projections for that time period; however, further into the
future, they observed some significant differences."We found that around the year 2250, some of these solid Earth
processes started to offset the melting of the ice sheet and the consequent sea
level rise," Larour said. In other words, they actually slowed the melting
down.The team noted that a hundred years even further into the future - by 2350
- this slowdown means that the
melting of the ice sheet is likely to contribute 29% less to global sea level
rise than previous models indicated."One of the main things we learned was that as grounded ice retreats
inland, the bedrock under it lifts up elastically," said Erik Ivins, a
co-author of the study. "It's similar to how a sofa cushion decompresses
when you remove your weight from it. This process slows down the retreat of the
ice sheet and ultimately the amount of melting."Although this sounds like good news, the scientists say it's important
to keep it in perspective. "It's like a truck traveling downhill that
encounters speed bumps in the road," said Larour. "The truck will
slow down a bit but will ultimately continue down the hill" - just as the
ice sheet will continue to melt and sea level will continue to rise.The breakthrough of this study, he added, was to
"reach resolutions high enough to capture as many of these 'speed bumps'
as possible and determine their effects in Antarctica while also modeling sea level
rise over the entire planet."The study, titled "Slowdown in Antarctic
Mass Loss from Solid Earth and Sea-Level Feedback," was published today in
Science.More information on the study can be found at:https://vesl.jpl.nasa.gov/sea-level/slr-uplift