by mcgowanjm » Wed 10 Feb 2010, 21:12:12
$this->bbcode_second_pass_quote('pstarr', 'D')idn't I hear that the
Atlantic conveyor, the planetary ocean current system that brings warm Gulf Stream waters north, is starting to fail? That could account for these extreme weather events. The movie "Day After Tomorrow" was actually based on reasonable scientific conjecture, first posited at the Woods' Hole Oceangraphic Institute.
The global thermohaline circulation is the oceanic overturning mode, which is manifested in the North Atlantic Ocean as northward-flowing surface waters which sink in the Nordic (Greenland, Iceland and Norwegian) seas and return southwards—after overflowing the Greenland–Scotland ridge—as deep water. This process has been termed the 'conveyor belt', and is believed to keep Europe 5–8 °C warmer than it would be if the conveyor were to shut down1. The variability of today's conveyor belt is therefore an important component of climate regulation. The Nordic seas are the only Northern Hemisphere source of deep water and a previous study3 has revealed no long-term variability in the outflow of deep water from the Nordic seas to the Atlantic Ocean. Here I use flows derived from hydrographic data to show that this outflow has approximately doubled, and then returned to previous values, over the past four decades. I present evidence which suggests that this variability is forced by variability in polar air temperature, which in turn may be connected to the recently reported Arctic warming4.
http://www.nature.com/nature/journal/v3 ... 871a0.html Nature 394, 871-874 (27 August 1998) | doi:10.1038/29736; Received 3 March 1997; Accepted 27 May 1998
Decadal variability in the outflow from the Nordic seas to the deep Atlantic Ocean
Sheldon Bacon
The Arctic Oscillation
The Arctic Oscillation refers to opposing atmospheric pressure patterns in northern middle and high latitudes.
The oscillation exhibits a "negative phase" with relatively high pressure over the polar region and low pressure at midlatitudes (about 45 degrees North), and a "positive phase" in which the pattern is reversed. In the positive phase, higher pressure at midlatitudes drives ocean storms farther north, and changes in the circulation pattern bring wetter weather to Alaska, Scotland and Scandinavia, as well as drier conditions to the western United States and the Mediterranean. In the positive phase, frigid winter air does not extend as far into the middle of North America as it would during the negative phase of the oscillation. This keeps much of the United States east of the Rocky Mountains warmer than normal, but leaves Greenland and Newfoundland colder than usual. Weather patterns in the negative phase are in general "opposite" to those of the positive phase, as illustrated below.
http://nsidc.org/arcticmet/patterns/arc ... ation.htmlThe Arctic Oscillation on Physics Forums Blogs
The Figure shows that December 2009 was the most extreme negative Arctic Oscillation since the 1970s. Although there were ten cases between the early 1960s ...
www.physicsforums.com/blog.php?b=1673