Abysmal sea temps in region rising 10 times faster than global average
By Summit Voice
FRISCO — Changing ocean dynamics have resulted in a distinct warming of deep waters in the Greenland Sea.
Since the 1980s, the water temperature between 2000 meters depth and the sea floor has risen by 0.3 degrees Celsius — enough heat energy to raise surface temperatures over Europe significantly. The rate of warming is about 10 times higher than the global average.
“This sounds like a small number, but we need to see this in relation to the large mass of water that has been warmed,” said Dr. Raquel Somavilla Cabrillo, who led the study for the Alfred Wegener Institute for Polar and Marine Research.
“‘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 centigrade. The Greenland Sea is just a small part of the global ocean. However, the observed increase of 0.3 degrees in the deep Greenland Sea is ten times higher than the temperature increase in the global ocean on average,” Somavilla said.
The cause of the warming is a change in the subtle interplay of two processes in the Greenland Sea: The cooling by deep convection of very cold surface waters in winter and the warming by the import of relatively warm deep waters from the interior Arctic Ocean.
“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 the sea floor” Somavilla explained. “This transfer of cold water from the top to the bottom has not occurred in the last 30 years. However, relatively warm water continues to flow from the deep Arctic Ocean into the Greenland Sea. Cooling from above and warming through inflow are no longer balanced, and thus the Greenland Sea is progressively becoming warmer and warmer.”
The study, published recently in the journal Geophysical Research Letters, is based on an analysis of temperature data from 1950 to 2010 in the abyssal Greenland Sea, which is an ocean area located just to the south of the Arctic Ocean.
“We use these changes as a natural experiment. The warming allows us to calculate how much water flows from the deep central Arctic into the Greenland Sea,” said Prof. Dr. Ursula Schauer, head of the Observational Oceanography Department at the Alfred Wegener Institute. “We observe here a distinct restructuring of the Arctic Ocean. This is a very slow process, and its documentation requires long term observations.”
To fully understand, how the world’s oceans react to climate change, scientists need to investigate the Arctic Ocean in more detail.
“Due to its large volume and its thermal inertia the deep ocean is a powerful heat buffer for climate warming. Especially, the polar oceans are scarcely studied. If we want to understand the role of the deep ocean in the climate system, we need to expand the measurements to remote regions like the Arctic,” Schauer said.