MADISON, WI (SPECTRUM NEWS) — Researchers from the University of Wisconsin have released a new study suggesting that the antarctic ice sheet could collapse as oceans warm. That collapse could lead to massive sea level rise.
Feng He, atmospheric scientist with UW-Madison, co-led the study with Oregon State's Peter Clark. Other researchers at UW-Madison like Andrea Dutton, a geoscience professor, co-wrote the study.
The study looks at the last time the earth's climate was in a similar spot as it is now. He said while this type of comparison isn't an exact predictor for the future, but he said it's a good example.
“We want to see in the past what happened, and maybe that will tell us about the future,” He said.
125,000 years ago when the earth was in another interglacial state, as it is now, was the last time average temperatures were close to the same level as they are now — about one degree higher than pre-industrial levels.
“That actually surprised us, because at that time sea level was about six to nine meters higher than the pre-industrial time,” He said.
Six to nine more meters of sea level rise would cause widespread damages or submergence of infrastructure in coastal cities or islands. Right now 70 percent of the world's largest cities are near a coast. 40 percent of the U.S. Population is on a coast.
“If we have large and very fast sea level rise all the infrastructure probably won't have enough time to accommodate that,” He said.
The study used three different models to look at climate and ice sheets. He said it took about four years to run the models at half-hour simulation intervals to look back 125,000 years.
He said with the similar temperatures — and even higher carbon dioxide levels — as the last time the polar ice sheets melted, it suggests eventually polar ice will melt.
“Sad news for us because it means if given long enough time actually sea level will rise that much,” He said.
He said rising ocean temperatures are forcing ice to melt quicker than the rising air temperature. Especially in the antarctic, where a large portion of the ice is underwater.
He said the melting ice leads to slowed circulation in the ocean. Less water movement between the tropical regions and the polar regions allows the water to warm up more. It also allows sea ice to form, insulating the water and allowing it to warm more underneath the water.
All of that allows for the ocean water temperature to further warm, and further melt ice.
“Our study actually adds to the support that we should really increase our effort to monitor the subsurface ocean warming,” He said.
He said already about half the ice melt in the antarctic happens underwater. He points out that air temperatures in the polar regions will remain largely cold, slowing the melt from the air. However, he points out that if water gets warmer, that melt will be more rapid. He even said the study suggests the Western Antarctic Ice Sheet would collapse.
The National Oceanic Atmospheric Addministration reports that in 2010 sea levels had risen globally by 10 inches above pre-industrial times. In 2014, NOAA reported that they were rising an eighth of an inch each year.
The rise in ocean levels has been visible to many. Madison's Gotham Bagles owner Joe Gaglio is a Long-Nsland native. The New Yorker said he can see the island essentially shrinking.
“A lot has changed, the beaches have changed a lot since I was younger, it's not a myth it's happening,” Gaglio said.
Gaglio points out a favorite spot of his, the Montauk Light House. Commissioned by George Washingtion in 1796, the historic lighthouse used to sit 300 feet from the shore. Now it's 100 feet away. New York State and the Federal Government have committed $24 million in efforts to save the lighthouse.
“I think it's a serious problem, Long Island has had that problem for a long time, even before it became national news,” Gaglio said.
Other communities are experiencing that problem. High-tide floods are making things difficult for some coastal towns and cities like Venice, Italy. Higher sea levels are even believed to be a contributing factor in an increase in severity of hurricanes and damage from them.
He said previous projections on sea level rise have been wide. The study gives a more narrowed projection, but there is still variability. The study suggests that by 2200 there could be 7.5 meters of sea level rise. In the last 150 years, He said there has been about 20 centimters of rise.
“We have already seen the damage,” He said about the current sea level rise.
Current estimates for the next 80 years, by the end of the century, put sea level rise at a range of .2 to 2 meters.
“Our study actually suggests maybe it should be on the higher end,” He said. “At the end of this century, like 80 years from now, we probably will get one meter.”
He said one meter could put more than half of the land on some island coutnries underwater, it could all-but submerge others.
He also said multiple meters of sea level rise will continue to make storms worse. He also said it could threaten inland water tables, potentially mixing fresh water aquifors with sea water.
“This is the biggest question for the future of climate change,” He said. “We are definitely into unprecedented territory.”
You can watch He deliver a presentation on his study here: https://www.youtube.com/watch?v=-GASfGadr7A