Thus, the difference in the climate across the Atlantic arises not only because western Europe warms but also because eastern North America gets colder. Both regions have their characteristic temperatures because of the atmospheric circulation pattern established by heat loss from the ocean in the vicinity of the Gulf Stream.
The amount of heat loss from the Gulf Stream that is required to establish this circulation cannot be sustained only from heat that the mid-Atlantic gains during the summer, however. Heat transported by the Gulf Stream, from lower latitudes, is also needed. In this sense, Kaspi and Schneider lend some credence to Maury's earlier ideas. Although the atmospheric low- and high-pressure systems are created without any need to invoke the influence of the Rockies on the jet stream, this new work does highlight the importance of the southwesterly winds in bringing warmth to Europe.
Interestingly, the Kaspi-Schneider model can also explain why western Oregon, Washington State and British Columbia have much milder winters than what Kamchatka endures. This transpacific contrast has never been attributed to the presence of the Kuroshio, the counterpart of the Gulf Stream in the Pacific, primarily because the Pacific is a much larger ocean and the Kuroshio is a considerably weaker current than the Gulf Stream across much of it. Yet the Kaspi-Schneider result would suggest that heat lost over the Kuroshio could induce a stationary, atmospheric-pressure system similar to the one near the Gulf Stream in the Atlantic. The system would deliver cold polar air to northwestern Asia via northwesterly winds there, and southwesterlies would deliver warmer air to the northern U.S. Pacific Coast.
Shutting Down the Gulf Stream
The jury is still out on which model is correct, although the Kaspi-Schneider scenario seems plausible. The second part of Maury's conjecture—that a cessation of the Gulf Stream would lead to more intense winters over northwestern Europe—has also recently generated considerable interest. For many years the nature of the Gulf Stream's role in climate change has been framed as this question: If a warmer climate melts Arctic ice, will the excess freshwater that enters the ocean in the northern Atlantic decrease the overturning circulation there, shut down the Gulf Stream and rob northwestern Europe of an important source of heat?
The overturning circulation consists of warm upper waters in the North Atlantic that move northward toward the pole and of cold deep waters that move southward toward the equator. These shallow and deep currents link to form something of a conveyor belt by the sinking, or downwelling, of surface waters at high latitudes in the Labrador and Nordic seas and by deep water elsewhere in the global basin that rises, or upwells, to the surface. In essence, the cold waters that sink in the northern North Atlantic are replaced by relatively warm surface waters that upwell elsewhere in the global ocean.
In many climate-warming scenarios, the melting of Arctic ice would add a large quantity of freshwater to the ocean at high latitudes. Because freshwater is less salty (and thus less dense) than seawater, it might not sink—so the downwelling that feeds the deep currents of the overturning circulation would be inhibited. In this case, there would be no physical requirement for warm deep waters to rise up elsewhere because there would be no downwelling to compensate for; in consequence, with no new warm water rising to the surface, the northward flow of such water—the Gulf Stream—might be diminished. Alternative scenarios hold that freshwater additions at high latitudes would divert the Gulf Stream farther south or diminish its strength. In either case, a weakened or diverted Gulf Stream would provide less heat for European winters. Many models strongly predict that a decrease in the overturning circulation correlates with a subsequent cooling in the North Atlantic and northwestern Europe.
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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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