Do changes in thermohaline circulation have immediate impact on regional climates?
March 31, 2010 10:13 AM   Subscribe

Do changes in thermohaline circulation have immediate impact on regional climates?

Boston has just experienced one of its wettest months ever. Every year I've lived here the spring rainy season seems to intensify. Cool weather persists, and in the later spring the area is typified by persistent fog and mist whenever the wind blows from the east or south. Last year's June was the cloudiest on record.

The progression has become intriguing to me. Researching as I could, I learned that the largest ocean change ever measured by modern instruments is the decrease in salinity of the north atlantic. This change must have effects on the thermohaline circulation that supposedly drives climate in the entire north atlantic region; but I have not heard a single mention of it by meteorologists. (Nor can I find publicly-available information about its variation).

The gulf stream is sitting to our east and south
. The cool labrador current runs close to the coast, keeping the coastal ocean temperature 20 deg F below that several hundred miles to the east. Wouldn't these starkly contrasting systems have profound impact on the climate of new england? Is there any resource which describes the degree of influence?

Communicating the immediate link between ocean currents and regional weather patterns might be an important mechanism for communicating the effects of climate change to the public at large.
posted by melatonic to Science & Nature (7 answers total) 1 user marked this as a favorite
Response by poster: Hmm... Perhaps I should have said "weather" instead of "climate" in the question title. I hope responders understand the confusion.
posted by melatonic at 10:14 AM on March 31, 2010

The simple answer to your question is, "No one knows."

But keep in mind that there is a huge amount of gaussian noise in plots of weather activity on a day-to-day, month-to-month, and even year-to-year basis. You can't judge anything from "wettest month ever" reports regarding climatic change, which at best requires multiple decades of data, if not millenia, to spot any kind of trend.
posted by Chocolate Pickle at 11:15 AM on March 31, 2010

Response by poster: A non-member contacted me to share a study which found no change in the northward thermohaline circulation since 1990, and corresponding discussion in the new york times.

This is very interesting, but does not quite address my question as it ignores the southward cold-water current (the labrador current). The coastal regions where this current is strongest were not sampled by the Argo float system whose data is analyzed in the paper, and much of the paper discusses methods to account for this systematic error using out-of-band sea surface height data.
posted by melatonic at 11:20 AM on March 31, 2010

Response by poster: Locals and long-term residents in Boston have noted that the sun shines less and less in springtime here from year to year. It's not so much an issue of one or two freak months. It's a trend.... The reports on extremes are simply a way of pointing out that the trend is extreme :)
posted by melatonic at 11:23 AM on March 31, 2010

I think you are right on target with your questioning of the implications of a freshwater lens forming in the N Atlantic. Many oceanographers/climatologists believe that deep water formation in the N Atlantic is the primary driver of the oceanic conveyor belt and if this shuts down or becomes attenuated by a freshwater cap- that would suck badly. Heat transfer via ocean currents (both vertical and horizontal) plays a HUGE role in driving climate so I would say the short answer to your question is "yes" but I'm not sure who does the research on that topic on the Atlantic coast. On the US West Coast, we pay attention to the Pacific Decadal Oscillation PDO in addition to ENSO. I recommend that you look up Wally Broecker and read this book if you have not yet.
posted by surfgator at 12:01 PM on March 31, 2010

To Follow the Water by Dallas Murphy is very informative on the Gulf Stream, the North Atlantic Gyre, and related subjects.
posted by Danf at 2:50 PM on March 31, 2010

Here are many more Wally Broecker citations.
posted by surfgator at 4:02 AM on April 3, 2010

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