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Big Chills

North American ice melt has flooded the North Atlantic more than once in recent memory, causing European temperatures to plummet

2 min read

As every educated European knows--that is to say, virtually every European--the continent's benign climate depends on an anomaly: Atmospheric warming by the Gulf Stream, which Benjamin Franklin first noticed. Were it not for the Atlantic's warming surface currents--and, perhaps too, deflection of high-atmosphere winds by the Rocky Mountains--Paris and London might resemble Winnipeg, and Scandinavia would be virtually uninhabitable. Because of this precariousness, notions of abrupt or catastrophic climate change have more currency in Europe than in the United States--especially the "big chill" scenario developed, ironically, by the American geochemist Wallace Broecker.

Broecker's 50 years of work at Columbia University's Lamont Doherty Earth Observatory got a recent celebration at the laboratory. Anybody wanting a quick and easy introduction to his main accomplishments can do no better than to watch and listen to the songs written for the occasion by folksinger Tom Chapin, who happens to be Broecker's brother-in-law, and Penn State geologist Richard Alley, author of a nice general-reader book about ice coring.

Broecker's big chill started about 10,500 years ago and lasted about 1,200 years, in a period now known as the Young Dryas, named after a Scandinavian flower whose wanderings testified to sudden climate change. In that event, an ice dam blocking a huge inland lake, Agassiz, burst, sending a flood of freshwater into the North Atlantic; the effect was to shut down the North Atlantic conveyor, plunging western and northern Europe into a mini-ice age.

In 1997, Alley published a paper identifying a similar event, one that occurred about 8,200 years ago, in which freshwater abruptly flooded the Hudson Bay. Now, in a recent Science paper, Shi-Yong Yu and colleagues report on an event about 9,300 hundred years ago, with a similar pattern yet again. That episode had "a Northern Hemispheric expression with a spatial pattern nearly identical to that of [Alley's] '8.2 kyr event,' a widespread cooling associated with the sudden drainage of the glacial Lake Agassiz-Ojibway complex through the Hudson Straight."

Commenting, Alley says there do indeed seem to be several significant "wiggles" in Earth's recent temperature record. The basic mechanism starts with the relative saltiness of the Atlantic, a result of trade winds carrying vapor from the Atlantic across Central America to the Pacific. When the salty Atlantic waters reach the region around Greenland and Norway they sink, to start their return journey south. But when there's a sudden freshwater infusion, the waters fail to sink, temporarily shutting down the conveyor mechanism. In the extreme case, says Alley, the surface freshwater freezes off Norway, giving the regional climate a really nasty kick. In any case, "the emerging picture is that the North Atlantic [climate] does care about freshwater."

The Conversation (0)
This photograph shows a car with the words “We Drive Solar” on the door, connected to a charging station. A windmill can be seen in the background.

The Dutch city of Utrecht is embracing vehicle-to-grid technology, an example of which is shown here—an EV connected to a bidirectional charger. The historic Rijn en Zon windmill provides a fitting background for this scene.

We Drive Solar

Hundreds of charging stations for electric vehicles dot Utrecht’s urban landscape in the Netherlands like little electric mushrooms. Unlike those you may have grown accustomed to seeing, many of these stations don’t just charge electric cars—they can also send power from vehicle batteries to the local utility grid for use by homes and businesses.

Debates over the feasibility and value of such vehicle-to-grid technology go back decades. Those arguments are not yet settled. But big automakers like Volkswagen, Nissan, and Hyundai have moved to produce the kinds of cars that can use such bidirectional chargers—alongside similar vehicle-to-home technology, whereby your car can power your house, say, during a blackout, as promoted by Ford with its new F-150 Lightning. Given the rapid uptake of electric vehicles, many people are thinking hard about how to make the best use of all that rolling battery power.

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