Showing posts with label Gulf Stream. Show all posts
Showing posts with label Gulf Stream. Show all posts

Saturday, September 26, 2015

Blob of cold water in North Atlantic has scientists worried


Blob of cold water in North Atlantic has scientists worried.(Wapo).

There's a blob of cold water in the North Atlantic Ocean, following a summer of abnormally warm temperatures -- and that has scientists concerned.

While the world appears to be heating up, an area south of Greenland and Iceland has been seeing the coldest temperatures in recorded history, according to data released by the National Oceanic and Atmospheric Administration (NOAA).

Researchers say there's no mistake in the data. The chillier-than-usual area is densely-populated with buoys and along a well-observed shipping line.

There's no definitive answer as to why the blob is there, but scientists think it has to do with the slowing of circulation in the Atlantic Ocean.

In March a team of scientists published a paper in Nature Climate Change, arguing a massive ocean current called the Atlantic Meridional Overturning Circulation (AMOC) is weakening.

AMOC is driven by temperature differences and the salinity of the water -- but a sudden injection of cold water can weaken the circulation.

So -- where is the cold water coming from?

The suggested source is melting glaciers in Greenland -- an area that's losing more than a hundred billion tonnes of ice annually.

Scientists aren't sure what this all means, but they're keeping a close eye on the area.


For years, climatologists have debated the effect global warming will have on the thermohaline circulation, and the Gulf Stream in particular. The currents are driven in part by cold, salty water sinking to the bottom of the North Atlantic, where it then flows south.

Even cold freshwater doesn't sink. The melting of the North American ice sheets at the end of the last Ice Age is considered the most likely explanation for the Younger Dryas event, when temperatures plunged again.

However, it's been less than clear how much melt would create a serious impact. According to Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research, whatever is required, we've had more. In Nature Climate Change, Rahmstorf and colleagues collate evidence that the Gulf Stream has weakened by 15-20%—an extent that is unprecedented in at least the last thousand years and it's probably our fault.

“Maps of temperature trends over the twentieth century show a conspicuous region of cooling in the northern Atlantic,” the paper notes, which is indicative of a loss of warm waters from the south. The authors calculate that more than 400 cubic kilometers (96 cubic miles) of runoff a year from Greenland glacial melt is diluting the once salty waters of the area. They have expressed concern that the trend could get worse.

A question of salinity.

Water with a lower salt concentration does not drop easily to the ocean depths, which is what usually happens to the Gulf Stream to the north of Iceland. It is here that this famous current plunges to the ocean floor before returning to the tropics and then, further south, towards the Antarctic Ocean. In other words, this deep ocean current is the ‘return’ of the surface Gulf Stream.

After more intense rainfall, however, the additional fresh water in the mix inhibits the Gulf Stream’s drop towards the ocean floor, and jams up this vast, worldwide climatic mechanism. This in turn interferes with, or even blocks off, the Gulf Stream on the surface.

If the Gulf Stream malfunctions, then Europe, deprived of its effects, will in turn lurch towards a new era of lower temperatures. In other words, winters in Lisbon may become as rigorous as those in New York.
Source pic. 

Fact or fiction? 

The climatic history of our planet shows that such a development in the past – a considerable influx of fresh water in the North Atlantic resulting from a massive offloading of ice from the American ice sheet – has already seen the Gulf Stream mechanism put “out of order”. Hmmmm......Mother Nature has a way of handling things, i would start worrying seriously about Global Cooling......Maunder Minimum style. Read the full story here.

Related: Gulf Stream is slowing down faster than ever, scientists say. ICYM.......Gulf Stream stops Britain from freezing over in Winter.




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Wednesday, March 27, 2013

Huge patches of warm air over the Arctic.Arctic sea ice, may well disappear altogether this summer

                                                


Huge patches of warm air over the Arctic.Arctic sea ice, may well disappear altogether this summer.(AN).
Over the past month or so, huge patches with temperature anomalies of over 20 degrees Celsius have been forming over the Arctic.
The three images below show such patches stretch out from Svalbard to Novaya Zemlya (top), north of Eastern Siberia (middle) and over West Greenland and Baffin Bay (bottom).

Paul Beckwith, regular contributor to the Arctic-news blog, comments:

"The problem with this type of pattern is that there is a tendency for what is termed the AD (Arctic Dipole) consisting of exceptionally high pressures over Northern Canada to Greenland. When the air leaves this region heading for the low pressure regions (winds) it curves to the right (due to Coriolis force) and is thus driven from the Bering Strait region to the North Pole and then out Fram Strait, this conduit is like flushing the toilet on the ice. Warm water is pulled to the cold North Pole and the ice is driven out the Fram Strait into the warm Atlantic where it is melted."

"But the really big problem is that this high pressure area over Northern Canada is a ridge (blocking) that stays pretty stationary over the summers and is directly causing the heat waves and drought in the western US (2003, 2011, 2012).
Another really big problem is that the part of the ridge over Greenland (or large GBI = Greenland Blocking Index); as discussed by Overland, Francis, et. al. in 2012 causes excessive melt in Greenland (as we saw in July, 2012 when 97% of Greenland was melting on the surface instead of the usual 40%). This is sending the Greenland albedo into a steep drop, causing even more heat absorption and melting."

Paul adds: "The Greenland high could reach 1070 mb in next few days; that will bring huge temperatures! By comparison, the world record highest was 1085 in Mongolia in December 19, 2001".

Indeed, as the jet stream slows down and becomes more wavier, such patches of warm air can be expected to extend more regularly into the Arctic. The result can be a huge melt of Arctic sea ice, as well as a huge melt of snow cover in Greenland, which also dramatically lowers albedo, as occurred in 2012 and as discussed in the earlier post Greenland is melting at incredible rate.

This spells bad news for the Arctic sea ice, which may well disappear altogether this summer.

Paul further adds: "For the record; I do not think that any sea ice will survive this summer. An event unprecedented in human history is today, this very moment, transpiring in the Arctic Ocean. The cracks in the sea ice that I reported on my Sierra Club Canada blog and elsewhere over the last several days have spread and at this moment the entire sea ice sheet (or about 99% of it) covering the Arctic Ocean is on the move. Clockwise. The ice is thin, and slushy, and breaking apart."

"This is abrupt climate change in real-time. Humans have benefitted greatly from a stable climate for the last 11,000 years or roughly 400 generations. Not any more. We now face an angry climate. One that we have poked in the eye with our fossil fuel stick and awakened. And now we must deal with the consequences. We must set aside our differences and prepare for what we can no longer avoid. And that is massive disruption to our civilizations."Hmmmmm........Shutdown of thermohaline circulation.Read the full story here.
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