Atlantic Ocean flow reversed 10,000 years ago, slowing down again [Nature, ArsTechnica]

Article in plain English:

The flow of top- and bottom-level currents in the Atlantic Ocean appear to be slowing down and may be due for a reversal like one that happened 10,000 years ago, according to new data. By studying sediment samples, scientists have found that, some time after the last glacial maximum, the undercurrent of the Atlantic Ocean switched from flowing north to flowing south, thanks in large part to changing temperatures.

Recently, discussions about the flow of the ocean have centered around what role it plays in climate change. The "conveyor belt" flow of the Atlantic Ocean, which currently goes south on the underside and north closer to the surface, helps regulate the temperature of the water and can distribute heat to normally cold areas. If it were to stop, it might allow for a bit of localized cooling in areas that are otherwise melting.

To get a better history of the Atlantic's flow, researchers studied sediment samples, specifically looking for the elements protactinium and thorium. They noted that a short time after the Last Glacial Maximum (LGM), the gradient of these elements in the North and South Atlantic reversed.

This indicates that the ocean used to flow north on the underside and south on the surface, the opposite of the way it does now. The ocean was likely at an effective standstill at some point, probably around the beginning of the Holocene between 10,000 and 12,000 years ago. The authors attribute the changes to surface cooling during the LGM, as well has an increase in seawater salinity in the Southern Ocean.

According to a graph in the paper that shows water mass travel time in the ocean, the flow speed increased for a while, but has become lethargic in the past few thousand years, indicating it may be on its way to a stoppage. Of course, it will likely be on the order of a thousand years or more before this happens naturally and, even if it does, the climate may be radically different by then anyway.

source: arstechnica.com...

Article for the scientists who are able to comprehend it:

The meridional overturning circulation (MOC) of the Atlantic Ocean is considered to be one of the most important components of the climate system. This is because its warm surface currents, such as the Gulf Stream, redistribute huge amounts of energy from tropical to high latitudes and influence regional weather and climate patterns, whereas its lower limb ventilates the deep ocean and affects the storage of carbon in the abyss, away from the atmosphere. Despite its significance for future climate, the operation of the MOC under contrasting climates of the past remains controversial. Nutrient-based proxies1, 2 and recent model simulations3 indicate that during the Last Glacial Maximum the convective activity in the North Atlantic Ocean was much weaker than at present. In contrast, rate-sensitive radiogenic 231Pa/230Th isotope ratios from the North Atlantic have been interpreted to indicate only minor changes in MOC strength4, 5, 6. Here we show that the basin-scale abyssal circulation of the Atlantic Ocean was probably reversed during the Last Glacial Maximum and was dominated by northward water flow from the Southern Ocean. These conclusions are based on new high-resolution data from the South Atlantic Ocean that establish the basin-scale north to south gradient in 231Pa/230Th, and thus the direction of the deep ocean circulation. Our findings are consistent with nutrient-based proxies and argue that further analysis of 231Pa/230Th outside the North Atlantic basin will enhance our understanding of past ocean circulation, provided that spatial gradients are carefully considered. This broader perspective suggests that the modern pattern of the Atlantic MOC—with a prominent southerly flow of deep waters originating in the North Atlantic—arose only during the Holocene epoch.

source: www.nature.com...

Pretty interesting stuff.

The Times, They Are A-Changin...

reply to post by tetsuo

And if Art Bell/Whitley Strieber were correct in The Coming Global Superstorm, then that means we are heading for an ice age.

Maybe that's how the Earth controls its temperature and avoids these "feedback loops" of temperature rises: the ocean currents shut down, and things cool off.

If so, then the Global Warming theorists better start prepping us for the next ice age, ironically enough.

P.S. Flag for links, but no star because you really should provide a summary of the points the articles make.

reply to post by harrytuttle


Good call. I don't get the whole flags and stars thing, it's just a dick sizing contest. But thank you for the thingie. And suggestion - I hate it when all there is in a thread is a link.

There was a thread recently that I agreed with that stated Global Warming shouldn't be referred to as just that. It should be appropriately referred to as Global Climate Change due to the Extremities of the weather patterns at both ends of the spectrum if this should come to pass.

There is a discussion at watts....wattsupwiththat.com... some seem to draw collations with solar activities that show up at interval times in the past ....I can see Europe as well as other local areas being affected from ocean currents ....I live in the Bay of Fundy area and when its hot inland a drive to the bay the temp drops as much as 10 degrees just from the air off the water that runs down from the north ...Maybe it will help them figure out what sort of a future climate we may expect .....peace

good observations. the gulf current and global ice age have been coming up alot lately.

no need for a summary you provided enough info for people to either be lazy and not read or read and thank you for the info. sometimes a summary is annoying I want to interpret the article myself not here someones opinion of the article right of the bat.