Huge pool of Arctic fresh water could cool Europe

23 January 2012

British scientists have discovered an enormous dome of fresh water in the western Arctic Ocean.

They think it may result from strong Arctic winds accelerating a great clockwise ocean circulation called the Beaufort Gyre, causing the sea surface to bulge upwards.

Researchers from the Centre for Polar Observation & Modelling (CPOM) at University College London, and the National Oceanography Centre (NOC), made their discovery using European Space Agency (ESA) satellites ERS-2 and Envisat. They measured sea-surface height over the western Arctic over a 15-year period, from 1995 to 2010.

Using these measurements, they calculate that since 2002 the sea surface in the western Arctic has risen by around 15cm, and the volume of fresh water has swollen by roughly 8,000 cubic kilometres. This is around ten per cent of all the fresh water in the Arctic Ocean.

If the wind changes direction, as happened between the mid-1980s and mid-1990s, the water could spill out into the rest of the Arctic and then perhaps even the north Atlantic. This could cool Europe by slowing down a key ocean current derived from the Gulf Stream, which keeps the continent relatively mild compared with countries at similar latitudes.

The Gulf Stream forms part of a larger movement of water called the ocean conveyor belt, which is itself one component of the global system of ocean currents.

"Satellite data has shown us that a dome of fresh water has been building up in the western Arctic over the past 15 years, due to the wind. Our findings suggest that a reversal of the wind could result in the release of this fresh water to the rest of the Arctic Ocean and even beyond," said Dr Katharine Giles from CPOM, lead author of the study, published in Nature Geoscience.

Earlier studies from ships, submarines and instruments on moored buoys had pointed to increasing volumes of fresh water in the Arctic over the last few decades, especially in the western Arctic. Not only that, but other studies had found that less fresh water reached the Atlantic than expected over the same period of time. These findings suggest the water is concentrated in the Beaufort Gyre, and can't spill out into the Atlantic.

But all of these studies relied on limited observations, so scientists weren't sure exactly what was driving the changes.

Climate models had suggested that the action of the wind on the sea surface could cause a raised dome to form in the middle of the Beaufort Gyre. But until now, there had been no continuous observations of sea-surface height to demonstrate this categorically.

Now, using satellite data from 1995 to 2010, Giles and her colleagues have found that the height of the sea surface in the middle of the Beaufort Gyre has increased substantially since 2002.

"We were surprised to find that our results also suggested that something else was going on," said Giles. "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. 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," she added.

"Satellites have been measuring how the ice is changing for many years but we now have the tools to monitor how the ocean underneath the ice is changing. These techniques can also be used with the recently launched CryoSat-2 satellite to measure changes over the whole basin," said Dr Seymour Laxon, director of CPOM and co-author of the study.

Further information

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Scientists' contact details:

Dr Katharine Giles
University College London
Tel: 020 7679 4450
Mob: 07765 252960

Dr Seymour Laxon
University College London
Tel: 020 7679 3932
Mob: 07952 820420

Notes

1. More information, graphics and animations showing the rise in sea surface height in the western Arctic are available on a secure area of the CPOM website.
(username: guest | password: *seaice1)

2. This press release is based on the paper 'Western Arctic Ocean freshwater storage increased by wind-driven spin-up of the Beaufort Gyre' - Katharine A Giles, Seymour W Laxon, Andy L Ridout, Duncan J Wingham and Sheldon Bacon (2012), Nature Geoscience, doi: 10.1038 / NGEO1379, published online on 22 January 2012.

3. The work was carried out at the Centre for Polar Observation & Modelling at University College London and was funded by a Natural Environment Research Council (NERC) fellowship and the National Centre for Earth Observation (NCEO). Radar altimetry data was provided by the European Space Agency (ESA).

4. CPOM is part of the National Centre for Earth Observation. The centre studies the ice sheets, sea ice, ocean circulation and sea level by combining satellite and field measurements with models. CPOM also provides the scientific leadership for the European Space Agency's CryoSat-2 mission.

5. Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender, and the first to provide systematic teaching of law, architecture and medicine. They are among the world's top universities, as reflected by performance in a range of international rankings and tables. UCL currently has 24,000 students from almost 140 countries, and more than 9,500 employees. Their annual income is over £800m.

6. NCEO, created on 1 April 2008, uses data from Earth observation satellites to monitor global and regional changes in the environment to develop a detailed understanding of the natural world, so that they might predict future environmental conditions. The NCEO, under the directorship of Professor Alan O'Neill (University of Reading), is a partnership involving 26 universities and research centres and more than 100 scientists and is carrying out research in a wide range of areas including climate change, glaciology, tectonics and the carbon cycle. The NCEO also includes technology development, mission support and advises NERC on its national and international investments in Earth observation.

7. NERC funds world-class science, in universities and its own research centres, that increases knowledge and understanding of the natural world. It is tackling major environmental issues such as climate change, biodiversity and natural hazards. NERC receives around £400m a year from the government's science budget, which is used to provide independent research and training in the environmental sciences.

Press release: 01/12

Huge pool of Arctic fresh water could cool Europe

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