Freak waves the best icebreaker
Freak waves observed by early Antarctic explorers break up sea ice hundreds of kilometres from the open water, New Zealand researchers have found.
Scientists from the National Institute of Water and Atmospheric Research (Niwa) found that waves bigger than three metres break ice much further away from the seaice edge than previously thought.
Niwa oceanographer Dr Mike Williams said the study, published in Nature today, provided vital information that had been missing from models of sea ice and its effect on climate.
‘‘When these experiments were last carried out in the 1970s and 80s, people needed to be sitting on the sea ice to take measurements and that meant they couldn’t be out there when the big waves came through,’’ Williams said.
The Niwa team developed wave buoys, which could collect data during big storms, he said.
Niwa hydrodynamics scientist Dr Alison Kohout deployed the buoys from the Aurora Australis, the Australian icebreaker used to free a Russian ship trapped in Antarctic ice for 10 days over summer.
The Niwa scientists also compared data from 1997 to 2009 to examine the link between wave heights in the Southern Ocean and sea ice extent.
‘‘What we’ve
found
is
that where waves have got bigger, the sea ice has retreated, and where waves have got smaller, the sea ice has expanded,’’ Williams said.
The research helped to explain why Antarctic sea ice had been increasing in some areas where climate models predicted it would decrease.
The effect of waves on sea ice has been known since the early days of Antarctic exploration. Ernest Shackleton was famous for having had his ship trapped in ice.
After the men abandoned ship in the Weddell Sea, waves broke up the ice they were on.
Williams said the data could benefit ships that get stuck in sea ice, and climate modelling.