In March 1959, the USS Skate popped up at the North Pole. What used to be a very long trek by foot had become a simple cruise for a nuclear-powered submarine. Back then, head-butting through Arctic ice was a tough proposition, even for a thickly-armoured submarine. These days it would be far easier. New research shows that not only is climate warming melting the ice but Arctic waters are becoming more turbulent which also reduces the depth of the ice coverage. The UK’s National Oceanography Centre (NOC) is watching the change and, using data gathered from Arctic-bound Royal Navy submarines, is helping scientists at NOC better understand the changes.
‘By investigating the nature of turbulence under sea ice, we can begin to understand how the circulation of the Arctic Ocean is likely to change as it becomes more ice-free during the summer,’ says Dr Charlotte Marcinko, lead author on the research. Ice melt is expected to accelerate as a cold, fresh layer of water beneath the ice mixes with a salty level below. As turbulent motions increase, so does the mixing. The result is a positive feedback loop that removes even more ice.
Turbulence links currents across ocean circulation, from those as small as a few millimetres to those as wide as ocean basins. But Arctic sea-ice can shield an ocean from it, making it more difficult to study the currents beneath. The NOC has used data from the submarines, including temperature and salt content measurements, to find out what’s happening beneath the ice.
The sensitive nature of the data required approval from the Ministry of Defence before it could be used. However, thanks to the Navy’s secret sub-Arctic ramblings, the NOC has discovered that turbulence is similar in Arctic regions with high and low amounts of sea ice. This means ocean turbulence is altered through the structure of the water column, and not through ice acting as a lid to protect the ocean from the wind.
This article was published in the April 2015 edition of Geographical Magazine