By Richard W. Spinrad and Ian Boydoct
Ocean and coastal waters around the world are beginning to tell a disturbing story. The seas, like a sponge, are absorbing increasing amounts of carbon dioxide from the atmosphere, so much so that the chemical balance of our oceans and coastal waters is changing and a growing threat to marine ecosystems. Over the past 200 years, the world’s seas have absorbed more than 150 billion metric tons of carbon from human activities. Currently, that’s a worldwide average of 15 pounds per person a week, enough to fill a coal train long enough to encircle the equator 13 times every year.
We can’t see this massive amount of carbon dioxide that’s going into the ocean, but it dissolves in seawater as carbonic acid, changing the water’s chemistry at a rate faster than seen for millions of years. Known as ocean acidification, this process makes it difficult for shellfish, corals and other marine organisms to grow, reproduce and build their shells and skeletons.
About 10 years ago, ocean acidification nearly collapsed the annual $117 million West Coast shellfish industry, which supports more than 3,000 jobs. Ocean currents pushed acidified water into coastal areas, making it difficult for baby oysters to use their limited energy to build protective shells. In effect, the crop was nearly destroyed.
Increasing acidity is hitting our waters along with other stressors. The ocean is warming; in many places the oxygen critical to marine life is decreasing; pollution from plastics and other materials is pervasive; and in general we overexploit the resources of the ocean. Each stressor is a problem, but all of them affecting the oceans at one time is cause for great concern. For both the developing and developed world, the implications for food security, economies at all levels, and vital goods and services are immense.
This year, the first nationwide study showing the vulnerability of the $1 billion U.S. shellfish industry to ocean acidification revealed a considerable list of at-risk areas. In addition to the Pacific Northwest, these areas include Long Island Sound, Narragansett Bay, Chesapeake Bay, the Gulf of Mexico, and areas off Maine and Massachusetts. Already at risk are Alaska’s fisheries, which account for nearly 60 percent of the United States commercial fish catch and support more than 100,000 jobs.
It is, for our home planet, an extremely warm year.
Indeed, last week we learned from the National Oceanic and Atmospheric Administration that the first eight months of 2015 were the hottest such stretch yet recorded for the globe’s surface land and oceans, based on temperature records going to 1880. It’s just the latest evidence that we are, indeed, on course for a record-breaking warm year in 2015.
Yet, if you look closely, there’s one part of the planet that is bucking the trend. In the North Atlantic Ocean south of Greenland and Iceland, the ocean surface has seen very cold temperatures for the past eight months. What’s up with that?
In March, several top climate scientists, including Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research and Michael Mann of Penn State, published a paper in Nature Climate Change suggesting that the gigantic ocean current known as the Atlantic Meridional Overturning Circulation, or AMOC, is weakening. It’s sometimes confused with the “Gulf Stream,” but, in fact, that’s just a southern branch of it.
The current is driven by differences in the temperature and salinity of ocean water (for a more thorough explanation, see here). In essence, cold salty water in the North Atlantic sinks because it is more dense, and warmer water from farther south moves northward to take its place, carrying tremendous heat energy along the way. But a large injection of cold, fresh water can, theoretically, mess it all up — preventing the sinking that would otherwise occur and, thus, weakening the circulation.
In the Nature Climate Change paper, the researchers suggested that this source of freshwater is the melting of Greenland, which is now losing more than a hundred billion tons of ice each year.
Temperatures may keep rising, yet public opinion has held steady: Most Americans have only low levels of concern about climate change, a new poll by Gallup finds.
Just 34 percent of adults said they worried “a great deal” about “global warming,” about the same as last year. Meanwhile, 35 percent said they felt the same way about “climate change,” just a 2 percentage points more than last year.
“A major challenge facing scientists and organizations that view global warming as a major threat to humanity is that average citizens express so little concern about the issue,” Gallup said.
The poll was conducted in early March, yet the results were released Friday – just one week after a comprehensive report by a United Nations climate panel reasserted that not only is climate change a man-made phenomenon, but its effects are already being felt around the world, they’re worse than previously predicted and no matter what actions are taken, they’ll persist for centuries to come.