Sea surface in a particular area of the Arctic Ocean has increased by as much as 15 centimeters (6 inches) over the past 15 years, leading to the formation of a large bulge of freshwater. It is estimated that this region of the ocean contains as much as 8,000 cubic kilometers (1,919 cubic miles) of water.
According to the results of a new study, which appears in the latest online issue of the top journal Nature Geoscience, it would appear that the bulge is being caused by an acceleration of the Beaufort Gyre, an oceanic circulation pattern driven by Arctic winds.
What this implies is that a change in this wind could allow this dome to fall apart, and all the freshwater it contains to spill in the northern sectors of the Atlantic Ocean. This is where the North Atlantic Drift – one of the five major oceanic currents – releases heat from the water.
Arctic Radar collage made from Envisat, blue indicates the area permanently covered with ice.That heat is then moved eastwards by prevailing winds, heating up the majority of the European continent. Last time the current was blocked – back when the sea that contained all the Great Lakes poured into the Arctic Ocean – glaciers moved as far south as the shores of the Mediterranean Sea.
ESA satellites show that a large dome of fresh water has been building up in the Arctic Ocean over the last 15 years. A change in wind direction could cause the water to spill into the north Atlantic, cooling Europe.
The results are remarkable: since 2002, the sea surface in the studied area has risen by about 15 cm, and the volume of fresh water has increased by some 8000 cubic km – around 10% of all the fresh water in the Arctic Ocean.
Researchers from the Centre for Polar Observation and Modelling (CPOM) at University College London and the UK’s National Oceanography Centre used data from ESA’s ERS-2 and Envisat satellites to measure sea-surface height over the western Arctic from 1995 to 2010.
The results were published yesterday in the online version of the scientific journal, Nature Geoscience.
The scientists conclude that the dome could be a result of strong Arctic winds accelerating a large ocean circulation known as the Beaufort Gyre, causing the sea surface to bulge.
A change in the direction of the wind would cause the fresh water to spill into the rest of the Arctic Ocean and even reach the north Atlantic.
This could slow a key ocean current, stemming from the Gulf Stream, and subsequently cool Europe.
This current keeps the continent relatively mild compared to other areas at similar latitudes.
Mean sea surface“When we looked at our data on a year-to-year basis, we noticed that the changes in the sea surface height did not always follow what the wind was doing, so we thought about reasons why this might happen,” said Katharine Giles, CPOM research fellow and lead author of the study.
“One idea is that sea ice forms a barrier between the atmosphere and the ocean. So as the sea ice cover changes, the effect of the wind on the ocean might also change.
“Our next step is to look into how changes in the sea ice cover might affect the coupling between the atmosphere and the ocean in more detail to see if we can confirm this idea.”
Sea ice can be measured by different types of satellite data. Radar altimeters on satellites such as the two used in the study, Envisat and ERS-2, can be particularly useful when observing inaccessible areas like the Arctic.
Envisat, the largest Earth observation satellite ever built, will mark 10 years in orbit in March.
ERS-2 was retired in July 2011, but 20 years of data from it and predecessor ERS-1 on oceans, land, ice and atmosphere will continue to be used by scientists for years to come.
“We were able to produce the Beaufort Gyre results thanks to the overlap of the ERS-2 and Envisat missions and long-term satellite data availability,” said Seymour Laxon, director of CPOM and co-author of the paper.
ERS2-Envisat-Tandem-in-flightESA will continue to monitor the Arctic with the upcoming Sentinel series of Earth-observing satellites for Europe’s Global Monitoring for Environment and Security (GMES) programme.
Later this year, the first results of seasonal changes in sea-ice thickness from data acquired by ESA’s CryoSat-2 satellite will be presented.
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