Atlantic 'Conveyor Belt' Not Slowing, NASA Study Finds

Illustration depicting the overturning circulation of the global ocean. Throughout the Atlantic Ocean, the circulation carries warm waters (red arrows) northward near the surface and cold deep waters (blue arrows) southward. (Credit: NASA/JPL)

ScienceDaily (Mar. 29, 2010) — New NASA measurements of the Atlantic Meridional Overturning Circulation, part of the global ocean conveyor belt that helps regulate climate around the North Atlantic, show no significant slowing over the past 15 years. The data suggest the circulation may have even sped up slightly in the recent past.

The findings are the result of a new monitoring technique, developed by oceanographer Josh Willis of NASA's Jet Propulsion Laboratory in Pasadena, Calif., using measurements from ocean-observing satellites and profiling floats. The findings are reported in the March 25 issue of Geophysical Research Letters.

The Atlantic overturning circulation is a system of currents, including the Gulf Stream, that bring warm surface waters from the tropics northward into the North Atlantic. There, in the seas surrounding Greenland, the water cools, sinks to great depths and changes direction. What was once warm surface water heading north turns into cold deep water going south. This overturning is one part of the vast conveyor belt of ocean currents that move heat around the globe.

Without the heat carried by this circulation system, the climate around the North Atlantic -- in Europe, North America and North Africa -- would likely be much colder. Scientists hypothesize that rapid cooling 12,000 years ago at the end of the last ice age was triggered when freshwater from melting glaciers altered the ocean's salinity and slowed the overturning rate. That reduced the amount of heat carried northward as a result.

Related thread ....:

Ocean Conveyor Belt Confounds Climate Science

********************************EXCERPT INTRO*****************************************

theresilientearth.com ^ | Thu, 04/08/2010 - 14:27 | Submitted by Doug L. Hoffman

Posted on Sun 22 Aug 2010 08:15:56 AM PST by Ernest_at_the_Beach

The Atlantic Meridional Overturning Circulation (AMOC), also known as the “Ocean Conveyor Belt,” has been the subject of much study since its discovery. The AMOC is primarily responsible for Europe's temperate climate and some scientists have warned that global warming could cause the ocean's flow to slow down or even stop. This rather counter intuitive result of a warming climate would result in a much colder Europe—perhaps even a new mini-ice age. A new analysis of data from satellites and drifting sensors finds no evidence that the conveyor belt is slowing. In fact, a NASA backed study indicates that the conveyor is far less susceptible to throttling by climate change than some climate change alarmists feared.

The heat transported by the AMOC makes a substantial contribution to the moderate climate of maritime and continental Europe. Scientists have long feared that any significant slowdown in the overturning circulation would have profound implications for climate change. In a 2005 Nature paper, “Slowing of the Atlantic meridional overturning circulation at 25°N,” Harry L. Bryden, Hannah R. Longworth and Stuart A. Cunningham analyzed temperature and salinity measurements made during five brief ship surveys between 1957 and 2004. These data seemed to indicate that the northward flow of the Atlantic conveyor suffered a 30% decline in volume around the turn of the century. These findings led to warnings that a scenario similar to the disaster film The Day After Tomorrow could be just around the corner.

“'Mini Ice Age' May Be Coming Soon, Sea Study Warns,” was the headline on the National Geographic News site. “Chilling new evidence from the Atlantic Ocean is raising fears that western Europe could soon be gripped by a mini ice age,” reported their 2005 news article. “The study supports computer model predictions suggesting that global warming will switch off the North Atlantic current in the next 50 to 100 years.” But even in 2005, it was noted that the magnitude of these findings did not seem to match up with observed climate variation.

***************************************EXCERPT INTRO*************************************

JoNova ^ | June 12th, 2010 | William Kininmonth Guest post

Posted on Fri 11 Jun 2010 11:07:22 AM PST by Ernest_at_the_Beach

Ever wondered how the whole planet could suddenly “get warmer” during an El Nino, and then suddenly cool again? William Kininmonth has the answer. As I read his words I’m picturing a major pool of stored “coldness” (bear with me, I know cold is just a lack of heat) which is periodically unleashed on the surface temperatures. The vast deep ocean abyss is filled with salty and near freezing water. In years where this colder pool is kept in place we have El Ninos, and on years when the colder water rises and mixes up near the surface we have La Ninas. The satellites recording temperatures at the surface of the ocean are picking up the warmth (or lack of) on this top-most layer. That’s why it can be bitterly cold for land thermometers but at the same time the satellites are recording a higher world average temperature, due to the massive area of the Pacific.

In other words, just as you’d expect, the actual temperature of the whole planetary mass is not rising and falling within months, instead, at times the oceans swallow the heat on the surface and give up some “coldness”. At other times, the cold stays buried deep down and the heat can collect and loll about on the surface.

William Kininmonth was chief of Australia’s National Climate Centre at the Bureau of Meteorology from 1986 to 1998. Below, he describes how a vast pool of cold water filled the deep ocean abyss over 30 million years, and why this water and the currents that shift it have a major impact our climate. The so-called Bottom Layer is not just pockets or pools, it forms around Antarctica, then sinks and flows along the bottom all the way across the equator and into the Northern Hemisphere. Bear in mind the average depth of the ocean is around 4 kilometers, and yet almost all the water below a depth of 1000 m is around 4°C or colder. The Antarctic Bottom Water itself is close to 0°C. The equivalent heat energy of the entire atmosphere is stored in just the top few meters of water. It gives us all some perspective on the relative importance of different factors affecting the climate. His thoughts are in response to the latest debate essay from Dr Andrew Glikson, so the figures 1 and 2 come from that article.

Kininmonth points out that small changes in the rate of the Thermohaline Circulation (also known as the Ocean’s Conveyor Belt) makes a huge difference to all corners of the globe, and that the climate models make large assumptions about the flow of energy. Since the cold bottom layer was created by a kind of “Antarctic Refridgerator” (set into play by the circumpolar current) this colossal cold pool of water will presumably hang around until the continents shift. That’s quite a few election cycles.

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.