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Ocean storms can influence sea ice break-up, warns study



Ocean waves larger than 3 metres in height can travel hundreds of kilometres below the ice before dispersing, scientists have shown.

These higher waves have been gradually breaking up the surface of sea ice, highlighting the importance of monitoring sea storms.

A New Zealand-led team has been running experiments off the coast of Antarctica, placing sensors along inward routes following the dispersal of the waves.

“At the ice edge, it’s quite noisy”, Alison Kohout, leader of the team based out of New Zealand’s National Institute of Water and Atmospheric Research in Christchurch, told the BBC.

“You have lots of waves coming from all directions with a full spectrum of frequencies. But as the waves move into the ice, this all gets cleaned up to produce one beautiful, smooth wave of constant frequency.”

She added, “The ice floes bend the waves, and over time you can imagine that this creates fatigue and eventually the ice will fracture. Interestingly, the fractures tend to be perpendicular to the direction of the waves, and to be of even widths.”

The study comes at a time when Antarctic ice loss has doubled in less than a decade, with a recent study showing that 160 billion tonnes of ice has been melting into the sea each year.

The collapse of the West Antarctic ice sheet has also been deemed “unstoppable”, with an expected rise of 4 metres (13ft), according to two scientific studies.

Computer simulations have failed to predict the continued break-up of ice, based on the recent discovery, but the team are hopeful their investigation will bring about more clues into the very rapid decline in summer ice cover and the small growth in the winter ice cover.

Kohout said, “[Another recent paper has already suggested] that wave heights are going to change with increasing distance from the ice edge to the land, and that could have more of an impact on ice break-up.”

Photo: NASA Goddard Space Centre via flickr

Further reading:

West Antarctic ice sheet collapse is now unstoppable

East Antarctic more vulnerable to devastating melt than first feared

Worries over melting of preciously stable Greenland ice sheet

Melting of Antarctica’s Pine Island glacier may continue for centuries

The Guide to Climate Change 2013


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