HOT AND COLD: The melting polar ice caps are sending large amounts of fresh water into the world's oceans. Many climate scientists fear that if the climate warms fast enough and melts off the remaining polar ice rapidly, the influx of freshwater could stall the Gulf Stream and rob the northeastern U.S. and northwestern Europe of their natural heating source, plunging the two continents into a cold snap that could last decades or longer.
Image: Getty Images
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Dear EarthTalk: If the ice caps are melting, what is happening to the salt content of the oceans? And might this contribute to weather patterns or cause other environmental problems?
—George Boyer, via e-mail
It’s true that the melting of the polar ice caps as a result of global warming is sending large amounts of freshwater into the world’s oceans. Environmentalists and many climate scientists fear that if the climate heats up fast enough and melts off the remaining polar ice rapidly, the influx of freshwater could disturb ocean currents enough to drastically change the weather on the land as well.
The Gulf Stream, a ribbon of ocean water that delivers heat from the tropics up to the North Atlantic, keeps northeastern U.S. and northwestern Europe weather much milder than other areas at the same latitude around the globe. In theory, less salt in the ocean could stall out the Gulf Stream and rob some of the world’s greatest civilization centers of their natural heating source, plunging the two continents into a cold snap that could last decades or longer—even as the rest of the globe warms around them.
The Gulf Stream keeps running because the warmer water travelling north is lighter than cold water, so it floats on top and keeps moving. As the current approaches the northern Atlantic and disgorges its heat, it grows denser and sinks, at which point it flows back to the south, crossing under the northbound Gulf Stream, until it reaches the tropics to start the cycle all over again. This cycle has allowed humans and other life forms to thrive across wide swaths of formerly frozen continents over thousands of years. But if too much dilution occurs, the water will get lighter, idling on top and stalling out the system.
Some scientists worry that this grim future is fast approaching. Researchers from Britain's National Oceanography Center have noticed a marked slowing in the Gulf Stream since the late 1950s. They suspect that the increased release of Arctic and Greenland meltwater is to blame for overwhelming the cycle, and fear that more warming could plunge temperatures significantly lower across land masses known as some of the most hospitable places for humans to live.
Of course—not surprisingly—others have noted a contradictory trend: Some parts of the world’s oceans are getting saltier. Researchers from the UK’s Met Office and Reading University reported in a recent issue of the peer-reviewed journal Geophysical Research Letters that warmer temperatures over southerly sections of the Atlantic Ocean have significantly increased evaporation and reduced rainfall from Africa to the Caribbean in recent years, concentrating salt in the water that’s left behind. In fact, the Atlantic in this region is about 0.5 percent saltier than it was four decades ago.
But given how little we really know about the future effects of our carbon loading of the atmosphere, calling these two trends contradictory might be premature—as the two regions of ocean interact with one another and are part of a larger whole. Looking instead at the big picture, it’s clear that climate change is already having a relatively large effect on the world’s oceans by fundamentally altering evaporation and precipitation cycles. Only time will tell how dramatic the results of these changes will be.
CONTACTS: National Oceanography Center, www.noc.soton.ac.uk; Met Office, www.metoffice.gov.uk; Geophysical Research Letters, www.agu.org/journals/gl/
EarthTalk is produced by E/The Environmental Magazine. GOT AN ENVIRONMENTAL QUESTION? Send it to: EarthTalk, c/o E/The Environmental Magazine, P.O. Box 5098, Westport, CT 06881; submit it at: www.emagazine.com/earthtalk/thisweek/, or e-mail: earthtalk@emagazine.com. Read past columns at: www.emagazine.com/earthtalk/archives.php
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11 Comments
Add CommentThe real question is: will there be any warning signs if that can happen - or will it just change quickly?
Reply | Report Abuse | Link to thisIf there are no warning signs then skeptics and deniers will keep talking against it until it is more than obvious that it has changed, which will (of course) be too late to do anything about it.
Even though I am extremely interested in Climate Change, I think SciAm ought to do a better job of reporting.
Reply | Report Abuse | Link to thisJust the other day in the BBC news:
The Gulf Stream does not appear to be slowing down, say US scientists who have used satellites to monitor tell-tale changes in the height of the sea.
Confirming work by other scientists using different methodologies, they found dramatic short-term variability but no longer-term trend.
http://news.bbc.co.uk/2/hi/8589512.stm
Maybe you ought to do a better job or reading also,
Reply | Report Abuse | Link to this"... the Gulf Stream does not appear to be slowing down"
"Appear" is a key word, that just means we cannot show that by measurements. It may actually be changing - one way or another - we just cannot see it.
In addition there is the question of whether the change, if it occurs, will be slow and incremental or an immediate quantum type of change.
This article is yet another example of the AGW alarmist hysteria encouraged by Scientific American.
Reply | Report Abuse | Link to thisI was looking through older articles on this site and the bias is undeniable. Look at the 3/09 article "Climate Change Makes Refugees in Bangladesh".
The article states:
"A growing body of evidence, including analyses from military experts in the United States and Europe, supports the estimate that by midcentury, climate change will make vast parts of Africa and Asia uninhabitable. Analysts say it could trigger a migration the size of which the world has never before seen."
What a complete crock of XXX. Does ANYONE currently believe that vast amounts of Africa and Asis will be uninhabitable in 40 years? If they do there is certainly no data to support their fear.
If SciAm had a bunch of articles noting how the earth was round, would you attribute that to bias?
Reply | Report Abuse | Link to thisMaybe, just maybe, data and measurements back up all these articles?
Also "vast" can mean different things. Vast in terms of square miles IS possible. Areas like Bangladesh are very low and can easily be flooded. That is a vast area. You seem to interpret vast as meaning a huge percentage - which shows YOUR bias.
And, yes, there is a whole mountain (and decades) of data to support that - people like you just refuse to accept any of it as valid.
@candide - Don't waste your breath, people like that drag you down to their level and then beat you with experience.
Reply | Report Abuse | Link to thisThe statement 'appear' has to do with actual data not someone's opinion. I advocate expanded data collection not assumption either way.
Reply | Report Abuse | Link to thisReport data not opinions.
candide - Technically, the Earth is not round. Since it's three dimensional, it is nearly, but not quite, spherical. Sorry - I just had to do it.
Reply | Report Abuse | Link to thisYes, I am aware of that - I was over simplifying.
Reply | Report Abuse | Link to thisThough if you want to get even more technical the earth is (roughly) an oblate spheroid, though not truly symmetrical to a given precision. ;)
candide - I was hoping you'd say that! Just kidding.
Reply | Report Abuse | Link to thisthe gulf stream is either changing, or it isn't. if our measurements are unable to detect data that indicates an instability toward a trend, then it's irresponsible to post affirmations. all in all, as far as sciam's track record for posting reactionary blogs, and biased articles, I'd say this one is pretty level.
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