Science

‘Gravity Waves’ Offer Hope to Coral in a Warming Ocean

CLIMATEWIRE | A huge computer simulation showing ocean circulation patterns has given scientists new hope that some coral reefs might escape the damaging effects of global warming.

A new study — based on a long-term project called “Estimating the Circulation and Climate of the Ocean,” or ECCO — has shown that little-known underwater waves called “gravity waves” may be plentiful enough to help scientists preserve existing reefs and help the polyps create new ones.

“It’s what I hope will be the main takeaway from this study,” explained Scott Bachman, an oceanographer for the National Center for Atmospheric Research (NCAR).

The study explains that the waves, which can’t be seen by satellites, can bring up cooler water from ocean depths. That may help some existing reefs become what the study calls “thermal refugia,” or thermal refuges, from the warming waters.

Earlier studies have shown that steadily rising temperatures since 2009 may have caused as much as a 14 percent decline globally in coral reefs, which are needed to help sustain the world’s fisheries. Many fish species use the fortress-like reefs for shelter and to find food.

But warming water has caused some of the colorful reefs to bleach and eventually die, leaving limestone skeletons where coral polyps once thrived.

Bachman and Joan Kleypas, another NCAR oceanographer and fellow author of the new study, said in an interview that the underwater waves will help researchers find better places to locate new reefs.

“It helps us use our resources more wisely and figure out the best places for coral restoration,” Kleypas said, adding that grim projections that coral reefs might disappear in the next three decades have driven some researchers from the field.

“It was just getting more depressing, more and more doomsday,” she noted. “When you find a physical solution that can help us do what we do, that’s super cool.”

Coral polyps are tiny animals that have a sacklike body and a mouth encircled by tentacles. They grow cuplike protective shells by extracting limestone from seawater.

A variety of algae come to live in the polyps, giving them a range of exotic colors that have moved some enthusiasts to describe their colonies — the resulting coral reefs — as one of the world’s most beautiful ecosystems.

But there are attractions beyond their beauty. According to research by NOAA, the reefs of some 700 species of coral provide homes for more than 4,000 species of fish.

That gives coral reefs a global economic value of about $10 trillion a year, said Kleypas.

The bleaching caused by warming water drives the colorful algae away and makes it harder for the polyps to continue building their reef.

ECCO, the project the new study is based on, simulated ocean circulations using supercomputers from NASA, the Massachusetts Institute of Technology and seven other international research entities. It was completed in 2014 and has been used mainly to solve physics questions related to the oceans.

But its detailed depiction of the cooling gravity waves, sent upward when deep ocean currents hit underwater hills and mountains, may also yield answers about climate change.

“The novelty of this study,” Bachman explained, “is that there was only one ocean model in existence that allowed us to tackle this problem, or at least to give us a starting point.”

Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2022. E&E News provides essential news for energy and environment professionals.

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