Global warming threatens the world’s oceans

by Mike Gaworecki

October 15, 2009

Being that I’m in the middle of the Pacific on an Oceans campaign, I thought it would be appropriate if I celebrated Blog Action Day ’09 with a post about the effects global warming is having on the world’s oceans.

I wrote yesterday about the obligation of the developed world to help developing nations deal with the impacts of climate change on the oceans, but I didn’t really specify what those impacts might be. Here are a few of the major impacts we can expect if global warming is not put in check:

Bleached coral reef• Coral bleaching
The world’s coral reefs are some of the most amazing and diverse ecosystems on the planet, but they’re in grave danger from global warming. Corals contain microscopic algae that provide the coral with food and give them their vibrant colors. Rising ocean temperatures cause corals to expel these algae, thus turning them white or "bleaching" them. Worse, the corals die if the algae don’t return.

Australia’s Great Barrier Reef, the world’s largest coral reef, experienced its worst ever case of coral bleaching in 2002, when over 60 percent of the reef was affected. Unless projected levels of climate change are slowed, much of the reef will be dead in decades. Worse, hundreds of species relying on the reef will also die out along with their living home.

Corals the world over are facing the threat of bleaching, from the Gulf of Mexico and the Caribbean to the Galapagos Islands and the Philipines.

•Global melting
As global temperatures rise, the world’s ice melts. It’s as simple as that. And we’re already witnessing this happening. Our recent Arctic Impacts expedition was all about documenting the meltdown of Greenland’s glaciers and trying to understand the mechanisms behind it.

The melting of the world’s sea ice and glaciers will have a number of implications, perhaps the most discussed being that as Arctic sea ice melts there will be less habitat for polar bears, further imperiling this already endangered species. But global melting will also contribute to sea level rise and change the salinity of the oceans, hurting fish stocks and disrupting ocean circulation patterns.

Most worrisome is the fact that as the ice melts, more land and ocean water is exposed. The white ice reflects the sun’s light, but the darker water and land absorbs it, thereby potentially creating a negative feedback loop in which the melting of the world’s ice and the heating of our planet is accelerated. Already the Arctic is melting much faster than anyone predicted.

•Sea level rise
Melting sea ice does not contribute to sea level rise because that ice is already floating, but melting glaciers most certainly will cause the world’s seas to rise. A very sobering report was released earlier this month by the United Nations Environmental Program that forecasted a 6.3 degrees Fahrenheit rise in global temperatures by the end of the century. This would mean as much as a six-foot rise in sea levels.

Even a sea level rise of just around three feet, meanwhile, is projected to displace millions of people who live in low-lying parts of the world. In fact, the president of the Maldives, a Pacific island nation that is only 4.9 feet above sea level on average, recently held a cabinet meeting underwater to highlight the threat that the looming climate crisis and sea level rise pose to his country.

You can check out this Google Map to see what various degrees of sea level rise might look like.

Mussels on beach•Threats to marine life
Coral and Polar bears aren’t the only species threatened by global warming. Rises in ocean temperatures will impact the entire web of marine life. For example, phytoplankton, which is the main food source of small crustaceans like krill, grow under sea ice. A reduction in sea ice implies a reduction in krill — and krill feeds many whale species, including the great whales.

Whole species of marine animals and fish are directly at risk. A recent study found that warmer waters, for instance, can lead to some species becoming more aggressive and more vulnerable to prey.

Ocean acidification is another problem threatening marine life. As more CO2 is pumped into our atmosphere, more CO2 is absorbed by the oceans, which decreases the pH level of the oceans. Unfortunately, ocean acidification is happening much faster than anyone predicted, making life harder and harder on organisms like molluscs that depend on calcium carbonate shells, which can be weakened or even dissolved by acid.

These are just some of the main impacts I wanted to talk about, but by no means all of them. I barely touched on what a change in ocean currents due to decreased salinity might mean to weather patterns, for instance. And speaking of weather patterns, you’re probably already aware that warmer ocean temperatures are widely considered to make tropical storms bigger and more frequent. There’s even some compelling evidence that climate change is causing the El Niño phenomenon to be more frequent and more persistent.

All of this, I think, makes it abundantly clear that we need to put pressure on President Obama and other world leaders to sign an ambitious climate treaty in Copenhagen this December.

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