Study to focus on Arctic after Greenland Sea found to have warmed 10 times faster than global ocean


Study to focus on Arctic after Greenland Sea found to have warmed 10 times faster than global ocean

ABC By Phoebe McDonald – November 2, 2013, 4:57 pm

A crew member lowers a CTD probe - which measures conductivity and temperature - into the Greenland Sea.
ABC A crew member lowers a CTD probe – which measures conductivity and temperature – into the Greenland Sea.

Scientists have revealed plans to examine temperature changes in the Arctic Ocean after a long-term study found the Greenland Sea is warming 10 times faster than the global ocean.

Scientists from Germany’s Alfred Wegener Institute (AWI) analysed temperature data from the Greenland Sea between 1950 and 2010.

Their results show that during the past 30 years water temperatures between two kilometres deep and the ocean floor have risen by 0.3 degrees Celsius.

Dr Raquel Somavilla Cabrillo, AWI scientist and lead author of the study, says researchers are surprised by the results.

“For a long time it was considered that the deep Arctic region was in a stationary state …[but] much more than we thought is changing,” she said.

Dr Somavilla says that the contribution from the Greenland Sea to global rising sea levels is greater than expected, and that scientists must now examine the Arctic Ocean in more detail to fully understand how the world’s oceans react to climate change.

“Because the changes in temperature are so fast – faster than the average of the rest of the ocean – then the contribution [to rising sea levels] is larger than expected for this region,” she said.

“That is the reason that we have to look to the rest of the Arctic, because it may be similar, and then we will have to recalculate the contribution of the whole area.”

Dr Somavilla says warmer water has been flowing from the Arctic Ocean into the Greenland Sea and the new research will focus on this area.

Degree of warming a cause for concern

Dr Somavilla says the Arctic region is a leading indicator of climate change.

“It has one of the highest sensitivities to climate warming, that is clear,” she said.

“It is suffering sea ice retreat, sea surface temperature is warming faster than in other areas, so the sensitivity is higher than in other places.”

She says a deep water temperature increase of 0.3 degrees Celsius may sound like a small number, but it needs to be seen in relation to the large mass of water that has been warmed.

“The amount of heat accumulated within the lowest 1.5 kilometres in the abyssal Greenland Sea would warm the atmosphere above Europe by 4 degrees Celsius,” she said.

“The Greenland Sea is just a small part of the global ocean. However, the observed increase is 10 times higher than the temperature increase in the global ocean on average.”

Dr Somavilla says deep oceans are heat buffers for climate warming and have the capacity to regulate temperature increases experienced on land.

“The warming that we can expect as a result of the increase in greenhouse gas concentration in the atmosphere can be accumulated in the atmosphere, in the upper layers of the ocean or in the deep ocean,” she said.

“We have to keep in mind, that 90 per cent of all this warming that we are generating is accumulated in the ocean.”

Temperature increases related to convection and inflowÂ

Dr Somavilla says the rise in temperature is caused by the inflow of warmer water from the Arctic Ocean as well as the cessation of deep convection in the Greenland Sea.

“Until the early 1980s, the central Greenland Sea has been mixed from the top to the bottom by winter cooling at the surface making waters dense enough to reach to sea floor,” she said.

“This transfer of cold water from the top to the bottom has not occurred in the last 30 years.

“After the ’80s it seems that winter heat losses – how much heat is lost from the ocean to the atmosphere – has decreased.

“The waters at the surface are lighter during the wintertime than before. They don’t reach the necessary density to reach the bottom of the Greenland Sea.”

Dr Somavilla says observations made during the last 100 years reveal rates of deep convection in the Greenland Sea are cyclical.Â

“There were previous cycles when deep convection was more intense or less intense. But it seems that this cycle is the longest of all of them and the temperature increase has also been the highest of all them,” she said.

She says if current trends continue the density, temperature and salinity levels of deep water in the Greenland Sea will reach the same levels of those in the Arctic Ocean.

“The Greenland Sea is getting lighter … It will reach the same density of the waters that are coming in,” she said.

“When they reach the same density we don’t know what will happen. [Temperature and salinity] are the same. They will keep increasing until they reach the same level … [then] they will probably continue rising, but at other rates,” she said. Â

The AWI study was published in the journal Geophysical Research Letters.

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