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Paper Clip: No contradiction, denser Antarctic sea ice indicates a warming Earth

Chunks of inland ice entering the sea leads to ocean stratification, with a colder surface layer forming over a warmer layer beneath the surface.

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Updated: August 3, 2015 1:15:22 am
Antarctic sea ice, Earth,  Antarctica, sea ice, paper clip, indian express news, J Hansen On September 19, 2014, the five-day average of Antarctic sea ice extent exceeded 20 mn sq km for the first time since 1979, according to the National Snow and Ice Data Center. The red line shows the average maximum extent from 1979-2014. (Source: NASA photo)

Climate change: Signs from Antarctica

Atmospheric Chemistry and Physics, 2015

Authors: J Hansen and Others

Sea ice around Antarctica has been growing, having last year reached the largest volumes ever recorded. This appears anomalous — and has given ballast to the arguments of climate change sceptics.

The new research has combined evidence from palaeoclimate data, climate modelling, and modern observations to argue that the increasing sea ice around Antarctica is the result of the continent itself losing massive chunks from its mass of ice, and is consistent with models of climate change.

Palaeoclimate data reveal that subsurface ocean warming causes ice shelf melt and ice sheet discharge. Chunks of inland ice entering the sea leads to ocean stratification, with a colder surface layer forming over a warmer layer beneath the surface. While the layer on top leads to increasingly denser sea ice formation, the warmer layer continues to melt the ice shelves beneath the surface.

The researchers posit that ice sheet mass loss can be approximated by a doubling time up to sea level rise of at least several metres. Doubling times of 10, 20 or 40 years yield sea level rise of several metres in 50, 100 or 200 years. According to the research, there is evidence of ice melt and a rise in sea levels of between 5 m and 9 m in the prior interglacial period that was less than 1 degree Celsius warmer than today. Recent ice sheet melt rates have a doubling time near the lower end of the 10-40 year range. The study concludes that 2 degrees Celsius global warming above the preindustrial level is highly dangerous.

(ADAPTED FROM STUDY ABSTRACT)

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