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Global WarmingOceansScience

Warming North Atlantic Warming Arctic

The water that flows north into the Arctic Ocean from the North Atlantic Ocean is the warmest it has been in 2,000 years and is likely related to the amplification of global warming in the Arctic, says a new study published in the most recent edition of the journal Science.

The study showed that the water running through the Fram Strait – which runs between Greenland and Svalbard – has warmed roughly 2.06 degrees Celsius (3.5 degrees Fahrenheit) over the past century.

Conversely, the Fram Strait water is approximately 0.6 degrees Celsius (1.08 degrees Fahrenheit) warmer than during the Medieval Warm Period which saw temperatures in the North Atlantic heat up between roughly 900 and 1300 AD and affect the climate in Northern Europe and northern North America.

Lead author Robert Spielhagen of the Academy of Sciences, Humanities and Literature in Mainz, Germany and his team believe that the rapid warming of the Arctic and recent decrease in the Arctic sea ice are linked to the heat transfer from the North Atlantic Ocean.

“Such a warming of the Atlantic water in the Fram Strait is significantly different from all climate variations in the last 2,000 years,” said Spielhagen, also of the Leibniz Institute of Marine Sciences in Keil, Germany.

According to study co-author Thomas Marchitto, a fellow at CU-Boulder’s Institute of Arctic and Alpine Research, the new observations are crucial for putting the current warming trend of the North Atlantic in the proper context.

“We know that the Arctic is the most sensitive region on the Earth when it comes to warming, but there has been some question about how unusual the current Arctic warming is compared to the natural variability of the last thousand years,” said Marchitto, also an associate professor in CU-Boulder’s geological sciences department. “We found that modern Fram Strait water temperatures are well outside the natural bounds.”

The team drilled ocean sediment cores dating back 2,000 years to add to the 150 years’ worth of meteorological and oceanographic data from Fram Strait to determine the past temperatures, together with a separate independent method that involved analysing chemical composition of sea shells.

The Fram Strait branch of the North Atlantic Current is the major carrier of oceanic heat to the Arctic Ocean. In the eastern part of the strait, relatively warm and salty water enters the Arctic. Fed by the Gulf Stream Current, the North Atlantic Current provides ice-free conditions adjacent to Svalbard even in winter, said Marchitto.

“Cold seawater is critical for the formation of sea ice, which helps to cool the planet by reflecting sunlight back to space,” said Marchitto. “Sea ice also allows Arctic air temperatures to be very cold by forming an insulating blanket over the ocean. Warmer waters could lead to major sea ice loss and drastic changes for the Arctic.”

“We must assume that the accelerated decrease of the Arctic sea ice cover and the warming of the ocean and atmosphere of the Arctic measured in recent decades are in part related to an increased heat transfer from the Atlantic,” said Spielhagen.

Source: University of Colorado at Boulder
Credit: Nicolas van Nieuwenhove (IFM-GEOMAR, Kiel)




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