 is the warmest in this infrared image of the Atlantic; yellow, green,blue and purple zones are progressively cooler.)
Red-hot: Gulf Stream water (red) is the warmest in this infrared image of the Atlantic; yellow, green,blue and purple zones are progressively cooler.
Image: COURTESY OF PETER MINNETT AND BOB EVANS University of Miami/MODIS/NASA
In Brief
- Three new climate studies indicate that our long-held belief about the Gulf Stream's role in tempering Europe's winters may not be correct. Yet the studies themselves do not agree.
- Two of the three studies ascribe a surprisingly large role to the direction of the prevailing winds, and one focuses on the heat lost from the ocean.
- Many climate models indicate that extensive melting of Arctic ice would not actually shut down the Gulf Stream, as previously thought.
- The ocean's influence on climate in Europe and elsewhere should become clearer within a decade, now that a global array of more than 3,000 floating ocean sensors called Argo is making near-real-time maps of temperature and salinity down to 2,000 meters.
More In This Article
For a century, schoolchildren have been taught that the massive ocean current known as the Gulf Stream carries warm water from the tropical Atlantic Ocean to northwestern Europe. As it arrives, the water heats the air above it. That air moves inland, making winter days in Europe milder than they are in the northeastern U.S.
It might be time to retire that tidy story. The explosion of interest in global climate has prompted scientists to closely study the climatic effects of the Gulf Stream only to discover that those effects are not as clear as conventional wisdom might suggest. Based on modeling work and ocean data, new explanations have emerged for why winter in northern Europe is generally less bitter than winter at the same latitudes in the northeastern U.S. and Canada—and the models differ on the Gulf Stream's role. One of the explanations also provides insight into why winter in the U.S. Northwest is warmer than it is across the Pacific in eastern Russia.
At the same time, recent studies have been casting doubt on the popular conjecture made a few years ago that melting of Arctic ice could “shut down” the Gulf Stream, thereby wreaking havoc with Europe's weather. Yet the studies do suggest that climate change could at least affect the strength of the Gulf Stream, which could lessen the impact of global warming on northern Europe.
Competing Theories
Climate variations across the globe stem primarily from the earth's spherical shape. Because the sun's rays are more perpendicular to the earth's surface at lower latitudes, they impart more heat per unit area there than at higher latitudes. This differential heating leads to the prevailing atmospheric winds, whose instabilities redistribute that heat from the tropics to the poles. The oceans, covering 70 percent of the earth, also play a major role in this redistribution. The upper two meters of the oceans store more solar heat than the entire atmosphere above the seas because the specific heat (a property that determines the capacity to store heat) of a cubic meter of water is about 4,000 times greater than the same volume of air (and about four times larger than it is for soil). Water temperatures in the upper 100 to 200 meters of the oceans at midlatitudes might vary by 10 degrees Celsius over a year, storing and releasing an immense amount of heat compared with the atmosphere or the land. And because ocean currents, such as the Gulf Stream, move water around the globe, heat gained in the summer at one locale can later be released to the atmosphere thousands of kilometers away.
Given that movement and the oceans' ability to store heat, it is easy to hypothesize that ocean currents might be responsible for the fact that winter air temperatures in Ireland, at about 50 degrees north latitude, are nearly 20 degrees C warmer than they are at the same latitude across the Atlantic in Newfoundland. Similarly, air temperatures at 50 degrees north latitude in the eastern Pacific, near Vancouver, are about 20 degrees C warmer than they are at the same latitude at the southern tip of Russia's Kamchatka Peninsula.
In the 19th century geographer and oceanographer Matthew Fontaine Maury was the first to attribute the relatively mild climate of northwestern Europe to the Gulf Stream. This powerful ocean current flows northward along the southeastern U.S. coast, a product of warm waters from the subtropics and tropics. At about the latitude of Cape Hatteras, N.C., the Gulf Stream turns to the northeast and flows out into the Atlantic. Maury surmised that the Gulf Stream supplies heat to the overlying westerly winds that move across the Atlantic toward northwestern Europe. He also speculated that if the Gulf Stream were somehow diminished in strength, the winter winds would be much colder and that Europe would experience Arctic-style winters. Over the years Maury's idea became almost axiomatic—and until recently, it also remained largely untested.
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9 Comments
Add CommentThere are lots of palm trees in Scotland, and there seems to be a subtropical climate on some sections of the coast.
Reply | Report Abuse | Link to thisThe palm trees are apparently native or "wild" so it's not just an effect of people planting and nurturing them.
This has been attributed to the gulf stream's warming effect, and in this case, I think it's likely since the climate at least locally along the coast is subtropical, which is amazing at such high latitudes.
Just a general warming effect on the Atlantic would probably not generate a sub-tropical climate, although it would certainly have a moderating effect, so probably there is a combination, localized subtropical climates from the Gulf Stream, and a more generalized moderating effect on Western Europe as a whole from the generalized warming effect of the Atlantic with southwesterlies winds having a moderating effect. This would be responsible for the notorious London fogs, with fog developing from the southwesterlies humid winds off the western Atlantic, colliding with the cold continental air masses originating off the arctic and Siberia.
I lost interest in whose model said what, and don't care which model might be more correct (at least in some peculiar circumstances). Any wonder why there is little confidence in unvalidated climate models?
Reply | Report Abuse | Link to thisThe most obvious conjecture is that both the ocean and the atmosphere are dynamically involved in global thermal exchanges - effective climate models most likely must reasonably represent both (and any other contributing factors).
It is clear why the American public does not believe in climate warming and its effect: all science is in meters and centimeters, as well as in centigrade for the temperature. Since the American population can only think in archaic measurements, they are missing it.
Reply | Report Abuse | Link to thisIt is indeed an amazing event to hit the "North Wall" of the Gulfstream in your sailboat on an Atlantic Crossing. The boat makes odd popping noises as the hull and structure expand at differing moduli, the water changes from that North Atlantic black-blue to a more Pacific color, maybe with a bit of sargassum thrown in like an erstwhile Cajun stew; and wherein you suddenly find yourself sweating in the New England Sound jacket which was absolutely necessary even 2 hours prior. I would suppose that such an amount of thermal energy would have to step to Entropy somewhere. The Entropy of that Somewhere would also be changed.
Reply | Report Abuse | Link to thisThe “Old theory” as well as all of the “New Theory” explanations appear to involve the Gulf Stream in various ways and are not exclusionary. It seems likely that several of these effects will be found to apply and explain multiple mechanisms by which the original narrative remains essentially true.
Reply | Report Abuse | Link to thisSo true sir! When will the rest of the world come into the modernity of feet and inches, one wonders?
Reply | Report Abuse | Link to this(Truthfully, I have a heck of a time with the metric system, having lived in the US for 6 decades. Sure, I can do the conversions, but I don't have the same 'feel' for the length of an inch vs that of a centimeter).
I really enjoyed this very balanced article, and feel like I learned a lot.
Reply | Report Abuse | Link to thisIt was long enough to explain the theories and point out the pros and cons of each.
I am particularly happy to hear that the flow of the Gulf Stream is not in danger of disruption from the effects of global warming:
"Yet recent modeling studies with higher resolution of ocean currents suggest that fresh Arctic meltwater may pour mostly into currents that are more restricted to the coastlines and therefore have less influence on the open ocean, where downwelling primarily occurs. Even if freshwater significantly affected the amount of waters downwelled in the North Atlantic, it turns out to be highly unlikely that this change would effectively shut down the Gulf Stream. A shutdown is unlikely because the path and the strength of the Gulf Stream depend largely on the speed and direction of the large-scale midlatitude winds. In most climate change scenarios, the general direction of the large-scale winds does not change significantly as Arctic ice melts, so the general path and strength of the Gulf Stream do not change much either."
Ocean currents drive weather patterns. This is not the debate, the debate is over how big of role these currents will play in climate change. The effects of ice melt upon upwelling ocean currents is being examined here, but this article also states that data resources are lacking.
Reply | Report Abuse | Link to thisI feel it is critical to look at as many variables as we can to determine implications of Arctic and Antarctic thaw, or redistribution of ice in these regions. With more data in locally effected areas, areas where ice melt is impacting thermo-haline gradients in any measurable way, it would be easy to make vague statements about how Europe might change in climate because of the effected Gulf Stream.
It is much better to look at this in terms of atmospheric events along with ocean currents to model weather. It is also a big deal that the ocean, itself, is vastly unknown and the role of deep ocean currents for thing like nutrient turnover, salinity gradient, and climate stability may play a much larger part in all of this when compared to high and low pressure systems.
This is interesting. No doubt the specific heat of water is 4000 times larger than that of air, and 4 times larger than that of soil. The explanation assumes that water moves horizontally from one location of the earth to another. It overlooks the vertical movements up and down in the ocean. However, the ocean floor is not at the same temperature eveywhere. At locations where volcanic eruptions occur in the ocean bed, the warm water there could move upward (vertically), displacing the colder (denser) water mass above. It would be nice to consdier this geothermal effecct on top of the solar effect explanied in the ariticle. Just a thought. I could be wrong.
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