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. The northeastward extension of the Gulf Stream—the relatively small branch that brings the warm upper waters to the subpolar regions—could potentially be disrupted, however. Thus, the weight of evidence indicates that the Gulf Stream would persist, but it is unclear how much Gulf Stream water would be carried northward under different climate scenarios.
More Data, Better Resolution
At present, answers to how climate change would affect Europe's weather come largely from modeling experiments. Still, the experiments have considerable uncertainties that can be reconciled only with more extensive data from the oceans. Few observations from the open oceans are older than a century, and we have satellite data for just the past 30 years or so.
Scientists have recently been making considerable progress in improving the oceanic database through the Argo project, an ongoing global collection of temperature and salinity measurements from more than 3,000 floating sensors scattered worldwide. The Argo array, deployed and operated by the U.S. and more than 30 other countries, allows scientists to make near-real-time maps of temperature and salinity in the upper 2,000 meters of the world's oceans. The complete array has been in place for less than a decade, and we are just beginning to use it to effectively examine the connection between atmospheric variability and changes in the large-scale ocean.
For example, a comparison of the Argo data with ocean observations from the 1980s, carried out by Dean Roemmich and John Gilson of the Scripps Institution of Oceanography, shows that the upper few hundred meters of the oceans have warmed by about 0.2 degree C in the past 20 years. Upper-ocean salinity also increased globally by a small 0.1 percent—yet below a few hundred meters, ocean waters appear to be considerably fresher than in previous decades. Whether these changes are enough to alter the climate in Europe or anywhere else remains an open question, but the data we are now getting from Argo offer some clues. For the earth to neither warm nor cool, the input of heat from the sun must equal the amount of heat radiated from the earth back into space. Accumulating greenhouse gases in the atmosphere are apparently upsetting this equilibrium. The observed warming of 0.2 degree C in the upper ocean is consistent with an excess of incoming solar radiation over outgoing radiation of approximately one watt per square meter.
Early results from our improved ocean observatory provide a powerful input for climate theories and models. The results also offer a hint at what will be possible in the coming decades. In the next 10 years, as scientists examine, in tandem, the sea-surface data from satellites, computer models and longer, subsurface data records from Argo, they should be able to assess the role of the ocean in climate with new precision. At that point, we may finally be able to determine how the Gulf Stream will affect climate change on our watery planet.
This article was originally published with the title Rethinking the Gulf Stream.
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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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