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About Keith Patton
Expertise
I can answer questions concerning physical and historical geology, environmental geology/hydrology, environmental consulting, remote sensing/aerial photo interpretation, G&G computer applications, petroleum exploration, drilling, geochemistry, geochemical and microbiological prospecting, 3D reservoir modeling, computer mapping and drilling.I am not a geophysicist.

Experience
I have 24 years experience split between the petroleum and environmental industries. I have served as an expert witness in remote sensing, developmental geologist, exploration geologist, enviromental project manager, and subject matter expert in geology and geophysical software development.

Organizations
American Association of Petroleum Geologists
American Association of Photogrammetrists and Remote Sensing

Education/Credentials
Bachelor and Master of Science
Registered Geologist in State of Texas

You are here: Experts > Science > Geology > Geology > North Atlantic Current shutdown

Geology - North Atlantic Current shutdown

Expert: Keith Patton - 11/3/2009

Question
How much ice would need to melt and flow into North Atlantic to shut down the North Atlantic Current? What effect would the shutdown of the North Atlantic Current have on the world climate (and on Europe in particular)? How much would this raise sea level? Could the impact of an asteroid (a small one, not a big world-destroying one) in Greenland be a reasonable cause for the melt, as opposed to global warming?

I know the effect would be nothing like in the movies. I'm writing a story where European civilization collapses before Columbus sails to the Americas, and I need a scientifically plausible cause for the demise of European society but not other societies. Thanks!

Answer
I don't know how much ice would have to melt, the mathmatics are beyond me. The current could be disrupted by the influx of fresh water diluting the hypersaline water flowing south which would upset the Gulf Stream fed North Atlantic current which keeps N. Europe warm.

One look at a map of the world with an eye to the northern latititudes should tell you what would happen to N. Europe should the current be disrupted. Great Britain is on the same latitude as Hudson Bay. France is on the same latitude as the Dakota's and Montana. Norway and Findland...forget about it. Large areas of the most productive agricultural land in W. Europe would see massive temperature drops, and areas that usually have ice free ports year round would start to freeze up. Almost all of most populous areas of W. Europe are on the same latitude as Montana and S. Canada. There is a reason most of the Canadian population lives within 300 miles of the U.S. border. N. Canada turns into a deep freeze in winter. I have seen -30F below zero in the Montana flatlands in November.

I answered this same question for a screen writer about 7-8 years ago. The movie the Day After Tomorrow came out the next year. He sped the time line up from about 10,000 years to several weeks for dramatic impact. The big storms were a fiction too.

Assuming that all the ice caps melted, 80 meters (240 feet) is the accepted estimate in the rise of sea level. Greenland alone would account for only a modest 6.5m (20 foot) rise in seal level.
Antarctic is the monster with almost 30 million km3 of the worlds' glacial ice. It would result in a 73m (219 feet) rise.

A meteor impact would melt ice and break up the ice sheet speeding up the melting process, but that would be short term. In fact, the disruption of the current would lead to a plunge into a cooling cycle.

http://pubs.usgs.gov/fs/fs2-00/

Your on the right track. I should think that the a meteor impact which could cause a rapid melting if only temporary surge of fresh water could cause a major albeit temporary disruption of the current, leading to a series of horrible winters, leading to ice bound ports, destruction of fishing fleetes (the Basques were fishing the New Foundland cod banks during this time feeding the insatiable hunger of Christian Europe for fish for their religious observances. (See Mark Kurlansky's Cod: The fish that changed the world for more background info)

This breakdown of systematic order could lead to a wave of chaos like that seen during the 100 years war and during the black death. Remember too that people would be forced inside for warmth as would their nemisis the rat, leading most likely to outbreaks of the Black Death and Scrub Typhus as refugees crowded into the cities as crops failed and live stock died. Religious zealotry would also take hold as opportunistic "prophets" spread the word of the second coming and end of days stuff like occurred during the times of plague. There might also be another incursion of nomadic invaders from Central Asia as they also migrated in search of warmer and more fertile grass lands on which to graze their horse herds.

There would be a domino effect of sorts that could last for a number of years.
Here is the article I referenced to the other writer published in the Atlantic Monthly on the disruption of the Atalantic current:

http://williamcalvin.com/1990s/1998AtlanticClimate.htm

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