Changing Oceans

Changing Oceans Photo Credit: Clipart.com

The effect of climate change on the world's oceans may have dire consequences for humans.


Our radical ocean experiment. I'm Bob Hirshon and this is Science Update.

Climate change is transforming the world's oceans, at a potentially huge cost. This according to a landmark study published in the journal Science. Co-author John Bruno, of the
University of North Carolina at Chapel Hill, says there are rapid changes in store that would take ages to occur naturally. For instance, in the next couple decades, melting Arctic sea ice will open a passage between the North Atlantic and Pacific.

And there'll be just thousands of species migrating from the one ocean into the other. And these two biogeographic regions have been independent for just about a million years.

That will destabilize the food web, which could lead to extinctions. Bruno says irreversible changes like these will affect millions of people who depend on the sea for food and work. I'm Bob Hirshon, for AAAS, the science society.

Making Sense of the Research

Although there has been much research on the effects of climate change on land, relatively little attention has been devoted to the effect on the oceans. Since the oceans cover over 70 percent of earth's surface area, this would seem to be a major oversight—especially since what happens in the oceans can have far-reaching consequences.

This study, published in Science, has been labeled the first comprehensive review of the research on our changing oceans. The report paints a complex and worrisome picture. According to Bruno, we're altering just about every measurable aspect of the oceans: we're warming them, we're changing their acidity, we're contributing to sea level rise, and we're altering the populations of creatures that live there, to name a few. 

What's more, he says some of the changes are approaching "tipping points," which will render them irreversible. A good example is the opening of the Arctic sea ice you just heard about. Shipping companies are already planning to take advantage of this opening by sending cargo ships through it, just as airliners sometimes fly over the North Pole (to get from the U.S. to Asia, for example). 

However, as you heard, there will be other passengers who take advantage of this new trans-Arctic canal: marine organisms. For the first time in a million years, sea creatures will be able to migrate easily from the North Atlantic to the North Pacific. Whenever two previously isolated populations come into contact for the first time, it greatly changes the ecological balance: some organisms will face new predators; others will find easy-pickings in new hunting grounds. Many other interactions could greatly upset the food web in northern waters.

Other changes involve domino effects that are less than intuitive. For instance, every summer since 2002, a so-called "dead zone" has emerged off the coast of Oregon. Within the dead zone, which has covered an area the size of New Jersey, massive amounts of fish die in oxygen-starved water. Scientists have learned that climate change has shifted wind patterns in the area, which has increased the upwelling of nutrients in the offshore waters. 

At first, you would think this was a good thing, since more nutrients can theoretically support more life. But what actually happens is that the nutrients breed more plankton and other small creatures than the top predators can eat. As these plankton die, they sink to the bottom of the sea, where they're consumed by bacteria that use up oxygen in their metabolic cycle. As oxygen levels drop, marine animals suffocate, just as we would if the air ran low on oxygen. Their dead bodies provide even more fuel to the bacteria, which consume even more oxygen. 

The death of marine life has a direct impact on humans, since many of us rely on the ocean for food and work. Even land-locked vegetarians would feel the economic impact of massive fish kills, as the populations near the Gulf Coast learned in the wake of the BP oil spill. A catastrophic change in fish populations also could make people leave some coastal areas in droves, as they look for other places to earn a living. 

Coastal cities are also threatened by sea level rise, another consequence of climate change. The change in sea level comes primarily from melting glacier ice that runs off land and finds its way to the sea, and a physical property of water called "thermal expansion," or the tendency to take up more space as it's heated. Rising sea levels may contribute to greater flood risks for cities from New York to Tokyo, and may wipe some low-lying islands, like the Maldives off the coast of India, completely off the map. Even with our best efforts to curb climate change, some of these changes will be inevitable, and humans will be forced to adjust to a rapidly changing ocean over the next century.

Now try and answer these questions:

  1. What are some of the effects of climate change on the oceans?
  2. How does something as simple as sea ice melting in the Arctic have far-reaching consequences?
  3. How does disrupting marine food webs impact humans, directly and indirectly?
  4. How does the "dead zone" off the coast of Oregon illustrate the complexity of humans' effects on the planet?

You may want to check out the July 23, 2010, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: the potential effects of climate change on the world's oceans, how global warming could influence carbon dioxide levels in the Arctic, and the search for more efficient air conditioners.

Going Further

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