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Post Info TOPIC: Thermohaline Circulation


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Posts: 131433
Date:
Gulf Stream Watch
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Current status of the Gulf Stream
Images of relative Gulf Stream velocity fields are derived from near-realtime data from the radar altimeters of the  Envisat, Jason-1, TOPEX/Poseidon, and GFO satellites.

  • These maps are updated daily. An archive of the images is here.
  • For more information about the images, follow this link.
  • Animations of the Gulf Stream velocities are here.
  • Some related links about projects using this information or providing alternative near real-time Gulfstream velocity solutions.
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Posts: 131433
Date:
The Arctic Ocean
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0.93005W_79.91534N
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11.52268W_89.94270N
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Some 20 million years ago, the Arctic Ocean was best described as a very large lake, whose fresh water leaked southwards through a narrow strait into the Atlantic.
Then, 18.2 million years ago, something happened. Drawn by shifting tectonic plates, the strait began to widen. Slowly, over the course of hundreds of thousands of years, salt water from the Atlantic began flowing into the Arctic turning it into the ocean we know today.
Martin Jakobsson of Stockholm University in Sweden and colleagues have been analysing the first core of sediments from the bottom of the Arctic Ocean, which was extracted in 2004. It reveals what was has been piling up on the bottom of the Arctic Ocean for the past 53 million years.

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RE: Thermohaline Circulation
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An international team responsible for coring the Arctic have presented scientists with long sought-after information on the regions natural history.
Sediment cores retrieved from the Arctics deep-sea floor by the Integrated Ocean Drilling Programs Arctic Coring Expedition (ACEX) have provided long-absent data to scientists who report new findings in the 21 June issue of Nature.
A team of ACEX researchers reports that the Arctic Ocean changed from a landlocked body of water (a lake stage) through a poorly oxygenated estuarine sea phase to a fully oxygenated ocean at 17.5 million years ago, during the latter part of the early Miocene era.
The authors attribute the change in Arctic conditions to the evolution of the Fram Strait into a wider, deeper passageway that allowed an inflow of saline North Atlantic water into the Arctic Ocean.
Scientists believe that the deep-water connection between the northern Atlantic and Arctic Oceans is a key driver of global ocean circulation patterns and global climate change.

In 2004, the offshore ACEX research team cored a 428-meter thick sediment sequence from the crest of the Lomonosov ridge in the central Arctic Ocean, near the North Pole.
These sediments provide the first geological validation of the Cenezoic paleoenvironmental history of the Arctic Ocean.
Current evidence of the onset of the ventilated circulation system is preserved in the chemical and physical properties and the micropaleontology of the recovered seafloor sediments.

"If we can learn what has happened in the geological past, we can begin to use that knowledge to look into the future. Scientists engaged in climate change studies are advancing an important area of knowledge about the planet we live on" - Co-chief scientist Jan Backman, Stockholm University.
 
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Posts: 131433
Date:
The Gulf Stream
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From the deck of a research ship moored in these gusty north Atlantic islands, workers are offloading three bright orange buoys whose sonar devices will help Bogi Hansen fill more gaps in an intriguing twist on climate change forecasts.
For the past year, the Faeroese scientists sonar has been pinging the Gulf Stream, the warm ocean current that has kept this subpolar archipelago unfrozen for centuries. His findings are of big interest because they contradict one of the most catastrophic predictions linked to global warming: that Arctic melting will strangle the Gulf Stream, thrusting Europe into a new Ice Age.
In fact, Hansens research and recent climate models raise a tantalising possibility: Can the slight weakening of the Gulf Stream expected over the next century actually help to offset the effects of global warming in northern Europe?

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RE: Thermohaline Circulation
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Sargassum seaweed, famous in nautical lore for entangling ships in its dense floating vegetation, has been detected from space for the first time thanks to an instrument aboard ESAs environmental satellite, Envisat. The ability to monitor Sargassum globally will allow researchers to understand better the primary productivity of the ocean and better predict climate change.
Using optical radiance data from the Medium Resolution Imaging Spectrometer (MERIS) aboard Envisat, Dr Jim Gower and Stephanie King of the Canadian Institute of Ocean Sciences and Dr Chuamin Hu of the US University of South Florida were able to identify extensive lines of floating Sargassum in the western Gulf of Mexico in the summer of 2005.

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Southern Ocean Circulation
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A novel analysis of water flow in the Southern Ocean surrounding the Antarctic is revealing previously hidden structures that are crucial in controlling the transport of drifting plants and animals as well as the distribution of nutrients and pollutants that affect ocean life.
Researchers at the University of New South Wales in Australia and the Universitat Paderborn in Germany discovered that barriers to currents, which can lead to swirling gyres and eddies that trap material for long periods, may escape detection with traditional analyses that concentrate on monitoring average water flow or sea surface height.
Rather than tracking flow in the ocean point by point, as is typical of most ocean studies, the researchers applied a more holistic approach based on a mathematical technique known as Lagrangian analysis. In effect, the method allows them to simultaneously consider all the possible ways that currents can move in the ocean, and then pick out the most likely solution.
When the team tested their approach on a simulated model of ocean current flow, they found that regions where drifting material might be trapped in seas near the Antarctic were clearly identified with the Lagrangian approach. Traditional analyses, however, can only hint at the regions' locales. The researchers plan to extend their study to encompass current flow on a global scale. The work should help to provide a clearer picture of the currents that are vital to the health of our planet's oceans-American Physical Society

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Posts: 131433
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RE: Thermohaline Circulation
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'Short-circuit' discovered in ocean circulation
Scientists have discovered how ocean circulation is working in the current that flows around Antarctica by tracing the path of helium from underwater volcanoes. The details are published in Nature this week.
The team of scientists, led by Alberto Naveira Garabato of the University of Southampton's School of Ocean and Earth Science at the National Oceanography Centre, Southampton, has discovered a 'short-circuit' in the circulation of the world's oceans that could help predictions of future climate change.

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Posts: 131433
Date:
Ocean Circulation
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Deep Ocean Waters Don't Run Still
Can sticky isotopes help us measure how water flows deep in the ocean?
The oceans circulation is thought to play an important role in our climate by transporting heat from tropical regions toward Earths poles. Of particular interest is the circulation in the Atlantic Ocean, where warm, shallow waters from the tropics flow northward and release heat in the North Atlantic region. There, the waters become colder and denser; they sink to the abyss and flow back southward in deeper parts of the oceans.
To understand how our climate operates then, we need a deeper understanding of how our oceans operate. In particular, we need a deeper understanding of the abyss (roughly below the top 1,000 meters or 3,280 feet), which represents 70 to 80 percent of the oceans volume. But the difficulty, time, and expense of collecting measurements in the depths leave us with a severe scarcity of data. Despite considerable progress over the last decades, we still have an incomplete and somewhat fuzzy picture of the motion of waters in the abyss.
However, two naturally occurring radioisotopes in the sealike breadcrumbs in Hansel and Gretels forestmay offer us another means to track circulation in the deep.

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Arctic sea ice
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A new NASA study has found that in 2005 the Arctic replaced very little of the thick sea ice it normally loses and replenishes each year. Replenishment of this thick, perennial sea ice each year is essential to the maintenance and stability of the Arctic summer ice cover.
The findings complement a NASA study released in fall 2006 that found a 14-percent drop in this perennial ice between 2004 and 2005. The lack of replenishment suggests that the decline may continue in the near future.    
Perennial ice coverage fluctuates seasonally for two reasons: summer melting and the transport of ice out of the Arctic. When perennial ice, which is 10 or more feet thick, is lost in these ways, new, thinner, first-year seasonal ice typically replaces it. Some of this seasonal ice melts in the following summer, and some is thick enough to survive and replenish the perennial ice cover.

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