Professor Cecelia Bitz, University of Washington

This was a lecture by visiting Professor Cecelia Bitz.  I saw it listed in the open lectures on Thursday’s newspaper which was fortuitous as the lecture was on that evening, and gave me the first open lecture report of 2014.  Cecelia Bitz had been part of the University of Otago’s team to Scott Base in Antarctica.  For the first lecture of the year, just before the beginning of the university year, this was well attended by several hundred people.  I suspect a lot of the relevant sciences and students made sure to hear her, as well as interested members of the public.

Sea ice is different from icebergs.  Icebergs calve off from glaciers as huge masses of thick ice.  Sea ice is frozen sea water.  It loses its salt content over time.  In the Arctic sea ice is about one to three metres in depth.  Historically it has been thinner in Antarctic seas, between one to two metres in depth, a person’s height.

The Arctic is warming faster than the global mean, mostly during the polar night.  The Antarctic is warming less quickly than the Arctic.  It is warming fastest in the Antarctic peninsula.  In 2009 the first two cargo ships crossed the Arctic Sea, north of Russia, between Europe and Asia.  They  were accompanied by ice-breakers.  It is possible that the Arctic Sea could become ice-free in the future and cargo ships would be free to supply the North-West Passage.  The Arctic Sea could be ice-free in September within a lifetime, by mid-century.

This threatens the survival of top predators in the Arctic Sea, the Polar Bear and the Ringed Seal.  Both in different ways depend on sea ice to survive and flourish.  It is possible that human intervention in stalling climate change could allow the polar ice-cap to re-grow in scale.  It has not reached a tipping point yet.  This might not save the top predator species.

The Antarctic is less certain.  It is a different model.  Scientists need to catch up with its different circumstances.  The Arctic Ocean is nearly completely contained, except where it is fed by warmer water from the Atlantic Ocean, from the Gulf Stream.  Cold fresh water flowing into the Arctic Ocean from Eurasian and North American rivers form a layer on top of warm Atlantic Sea water.  The cold water cycles back into the Atlantic Ocean.  The largest ice-capped land-mass in the Arctic Ocean, Greenland is already subject to ice-melt.

Antarctica is a larger land-mass than Greenland.  Its ice-cap will decrease at a slower rate.  It may be more than a century away.  Increasing fresh water in the surrounding oceans will affect it.  Reduction of emissions will slow the rate of loss.  As always to do this there needs to be the will to act.

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