How does gulf stream affect northern europe

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, times greater than the same volume of air and about four times larger than it is for soil. Water temperatures in the upper to 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. At about the latitude of Cape Hatteras, N. 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. A decade ago, however, Richard Seager of Columbia University's Lamont-Doherty Earth Observatory and his colleagues produced an explanation for Europe's warmer winter that had nothing to do with the Gulf Stream. Seager's modeling study indicated that when the atmospheric jet stream, which flows around the earth from west to east, hits the Rocky Mountains, it begins to oscillate north and south.

The oscillation produces winds that flow from the northwest over the western side of the Atlantic basin and from the southwest over the Atlantic's eastern side. The northwesterly winds bring cold continental air to the northeastern U. In this view, it is not heat carried by the Gulf Stream that moderates the European climate. Instead heat that is stored off the shores of Europe, in the upper meters of the ocean during the summer, is released to the atmosphere in winter when the southwesterly winds mix the surface ocean waters.

In this scenario, the classic conjecture of Maury is incorrect: large-scale wind patterns directed by mountain ranges, plus local storage of heat by the ocean near Europe, set the temperature differences between the western and eastern sides of the Atlantic [ see box on next two pages ].

They put forth a counterargument that offered some modern support for Maury's historical ideas. After examining archived sea-surface temperature data, the two oceanographers concluded that the amount of heat stored in the upper layer of the eastern Atlantic Ocean at the latitudes of northern Europe is enough to maintain mild air temperatures only through December of an average year. The additional heat required to moderate the climate over the remainder of the winter had to be imported from elsewhere.

The most likely source: the northeastward-flowing Gulf Stream. Measurements showed that at 35 degrees north latitude—roughly the latitude of North Carolina—the North Atlantic transports about 0. Yet at 55 degrees north latitude—the latitude of Labrador in Canada—this poleward heat transport is negligibly small. Where does all the heat go? The prevailing winds then carry the heat eastward, where it moderates the European climate.

In Yohai Kaspi, now at the Weizmann Institute of Science in Rehovot, Israel, and Tapio Schneider of the California Institute of Technology unveiled a third idea, based on novel numerical experiments of the atmosphere and the ocean.

They suggested a degree of truth in both the Seager and Rhines scenarios but concentrated mostly on patterns of atmospheric pressure. Kaspi and Schneider's model indicated that the loss of heat from the ocean to the atmosphere along the path of the Gulf Stream where it leaves the U. East Coast generates a stationary, atmospheric low-pressure system to the east—on the European side of the Atlantic.

When a spinning ice skater does as much, by spreading his arms, the conservation of angular momentum slows his spin. An atmospheric column going up a mountain behaves in a similar way and swerves to the south to gain some clockwise spin, which offsets part of the counterclockwise planetary component of its spin.

Figure 8. The waviness in the flow of the mid-latitude westerlies that is responsible for keeping European winters mild results from a fundamental principle of physics: the conservation of angular momentum. Because the top of the troposphere acts as something of a lid, air flowing from the Pacific over the Rocky Mountains must compress vertically and, as a consequence, expand horizontally.

Conservation of angular momentum demands that a package of air depicted as white cylinder undergoing such a horizontal expansion must develop a component of clockwise spin to reduce the predominantly counter-clockwise spin it has by virtue of its location in the Northern Hemisphere.

The length of the red arrows indicates relative amount of spin, which is derived from both local air movements and the revolution of the planet. The new component of clockwise spin manifests itself as a gentle swerve to the south in what is predominantly west-to-east flow.

When this package of air then moves over the eastern side of the continent and on over the Atlantic, it does the opposite, expanding vertically and contracting horizontally, which allows it to veer back toward the north.

The wavelike pattern sends air heated over the Atlantic to the northeast, where it warms Europe. On the far side of the Rockies, the reverse happens: The air begins to stretch vertically and contract horizontally, becoming most contracted in the horizontal when it reaches the Atlantic.

And as with an ice skater pulling in his arms, conservation of angular momentum demands that the air gain counterclockwise spin. It does so by swerving to its left. But having moved to the south after crossing the mountains, it is now at a latitude where the planetary component of its angular moment is less than it was originally.

To balance this reduction in angular momentum, the air acquires more counterclockwise spin by curving back around to the north. This first southward and then northward deflection creates a waviness in the generally west-to-east flow of air across North America and far downwind to the east.

Such waves are of massive scale. The southward flow takes place over all of central and eastern North America, bringing Arctic air south and dramatically cooling winters on the East Coast. The return northward flow occurs over the eastern Atlantic Ocean and western Europe, bringing mild subtropical air north and pleasantly warming winters on the far side of ocean. Topographically forced atmospheric waves contribute significantly to the large difference in winter temperature across the Atlantic.

When Battisti and I removed mountains from our climate models, the temperature difference was cut in half. Our conclusion was that the large difference in winter temperature between western Europe and eastern North America was caused about equally by the contrast between the maritime climate on one side and the continental climate on the other, and by the large-scale waviness set up by air flow over the Rocky Mountains.

Evidence from ocean sediments suggests that at times during the last Ice Age the North Atlantic thermohaline circulation was considerably weaker than it is today, or perhaps it even shut down entirely. One such event took place about 12, years ago, during the last deglaciation, and is called the Younger Dryas after a European cold-dwelling flower that marks it in some terrestrial records. The Younger Dryas began with a dramatic reversal in what was a general warming trend, bringing near-glacial cold to the North Atlantic region.

This episode ended with an even more dramatic warming about 1, years later. In Greenland and western Europe, the beginning and end of the Younger Dryas involved changes in winter temperature as large as 20 degrees taking place in little more than a decade.

But the Younger Dryas was not a purely North Atlantic phenomenon: Manifestations of it also appeared in the tropical and southern Atlantic, in South America and in Asia. For many years, the leading theory for what caused the Younger Dryas was a release of water from glacial Lake Agassiz, a huge, ice-dammed lake that was once situated near Lake Superior.

This sudden outwash of glacial meltwater flooded into the North Atlantic, it was said, lowering the salinity and density of surface waters enough to prevent them from sinking, thus switching off the conveyor. The North Atlantic Drift then ceased flowing north, and, consequently, the northward transport of heat in the ocean diminished.

The North Atlantic region was then plunged back into near-glacial conditions. Or so the prevailing reasoning went. Recently, however, evidence has emerged that the Younger Dryas began long before the breach that allowed freshwater to flood the North Atlantic.

What is more, the temperature changes induced by a shutdown in the conveyor are too small to explain what went on during the Younger Dryas. Some climatologists appeal to a large expansion in sea ice to explain the severe winter cooling. I agree that something of this sort probably happened, but it's not at all clear to me how stopping the Atlantic conveyor could cause a sufficient redistribution of heat to bring on this vast a change.

In any event, the still-tentative connections investigators have made between thermohaline circulation and abrupt climate change during glacial times have combined with the popular perception that it is the Gulf Stream that keeps European climate mild to create a doomsday scenario: Global warming might shut down the Gulf Stream, which could "plunge western Europe into a mini ice age," making winters "as harsh as those in Newfoundland," or so claims, for example, a recent article in New Scientist.

This general idea been rehashed in hundreds of sensational news stories. The germ of truth on which such hype is based is that most atmosphere-ocean models show a slowdown of thermohaline circulation in simulations of the 21st century with the expected rise in greenhouse gases.

The conveyer slows because the surface waters of the subpolar North Atlantic warm and because the increased transport of water vapor from the subtropics to the subpolar regions where it falls as rain and snow freshens the subpolar North Atlantic and reduces the density of surface waters, which makes it harder for them to sink. These processes could be augmented by the melting of freshwater reserves glaciers, permafrost and sea ice around the North Atlantic and Arctic.

But from what specialists have long known, I would expect that any slowdown in thermohaline circulation would have a noticeable but not catastrophic effect on climate. The temperature difference between Europe and Labrador should remain. Temperatures will not drop to ice-age levels, not even to the levels of the Little Ice Age, the relatively cold period that Europe suffered a few centuries ago. The North Atlantic will not freeze over, and English Channel ferries will not have to plow their way through sea ice.

A slowdown in thermohaline circulation should bring on a cooling tendency of at most a few degrees across the North Atlantic—one that would most likely be overwhelmed by the warming caused by rising concentrations of greenhouse gases. This moderating influence is indeed what the climate models show for the 21st century and what has been stated in reports of the Intergovernmental Panel on Climate Change.

Instead of creating catastrophe in the North Atlantic region, a slowdown in thermohaline circulation would serve to mitigate the expected anthropogenic warming! When Battisti and I had finished our study of the influence of the Gulf Stream, we were left with a certain sense of deflation: Pretty much everything we had found could have been concluded on the basis of results that were already available.

Ngar-Cheung Lau of the National Atmospheric and Oceanic Administration's Geophysical Fluid Dynamics Laboratory GFDL and Princeton University had published in an observational study in which he quantitatively demonstrated the warming and cooling effects that large-scale waves in the atmosphere had in Europe and eastern North America, respectively. In the s, atmosphere modelers such as Brian J.

Hoskins and Paul J. Stouffer, had used a coupled ocean-atmosphere climate model to determine the climate impacts of an imposed shutdown of the North Atlantic thermohaline circulation. Their modeled climate cooled by a few degrees on both sides of the Atlantic and left the much larger difference in temperature across the ocean unchanged. Other published model experiments went on to show the same thing.

Further, the distinction between maritime and continental climates had been a standard of climatology for decades, even centuries. What is more, by the late s satellite data, and analyses of numerical models into which those data had been assimilated as part of the weather-forecasting process, had shown that in mid-latitudes the poleward transport of heat by the atmosphere exceeds that by the ocean several-fold.

All Battisti and I did was put these pieces of evidence together and add in a few more illustrative numerical experiments. Why hadn't anyone done that before? Why had these collective studies not already led to the demise of claims in the media and scientific papers alike that the Gulf Stream keeps Europe's climate just this side of glaciation?

It seems this particular myth has grown to such a massive size that it exerts a great deal of pull on the minds of otherwise discerning people. This is not just an academic issue. The play that the doomsday scenario has gotten in the media—even from seemingly reputable outlets such as the British Broadcasting Corporation—could be dismissed as attention- grabbing sensationalism.

Still, 10 centimeters can be significant. And if sea level is a little bit higher, maybe because of the Gulf Stream weakening, it only makes matters worse.

However, the Gulf Stream slowing up is going to be a rather minor part of the dangers of climate change, in my opinion. The thing that I would worry about is that extreme weather events are going to become more commonplace. The deserts are going to expand toward the poles in both hemispheres. Hurricanes are going to get stronger, and weather extremes will be more common. And then over the longer-term, over decades and centuries, the big concern is extreme increase in sea level because of glacial melt.

So those things worry me. It is possible, but it really has to be done soon before it becomes irreversible. Got a burning science question? Send us an email or message us on Instagram. Q1-are dryer deserts adding to climate change Q2- what would happen if we could wet the deserts [not flood] to climate change Q3- in wetting- would that help vegetation growth and ground water, how would that impact on climate change.

Drylands are particularly susceptible to land degradation because of scarce and variable rainfall as well as poor soil fertility, dry barren land is not capturing carbon or doing nothing. Q3, Yes in relation to Q1 also it will allow vegitation to start growing again, and that in effect is capturing carbon is it not?

Ive also been very curious on the aspects on turning desert land back to fertile land but each aspect has its own uses and benifits, if we were to terraform the saharah for example, how would the amazon rainforest get its supply of nutrients.

This review synthesizes paleoclimate archives, model simulations, and the instrumental record, which collectively suggest that decadal and longer-scale variability of the Gulf Stream's heat transport manifests in changes in European temperature, precipitation, and storminess. Given that anthropogenic climate change is projected to weaken the Atlantic Meridional Overturning Circulation, associated changes in European climate are expected.