Scientists find new mechanism that contributes to Arctic warming

New research says the Arctic Ocean traps more energy from far infrared radiation than previously estimated

By Rajit Sengupta
Published: Friday 07 November 2014

Arctic sea ice hit its annual minimum on Sept. 17, 2014. The red line in this image shows the 1981-2010 average minimum extent (Image Credit: NASA/Goddard Scientific Visualization Studio)

Scientists claim to have found a mechanism that could be contributing more to Arctic warming than other factors.

Far infrared, a long-wavelength region of the electromagnetic spectrum, could well be the main reason behind Arctic warming and melting sea ice, claims the group of scientists from the Lawrence Berkeley National Laboratory of the US department of energy.

The invisible wave accounts for about half of the energy emitted by the Earth’s surface. It was overlooked for a long time and not well represented in climate models because “it was difficult to measure”. As a result, existing climate change models assume that all surfaces are 100 per cent efficient in emitting far-infrared energy.

But the new research claims open oceans are much less efficient than sea ice when it comes to emitting in the far-infrared region of the spectrum. “This means that the Arctic Ocean traps much of the energy in far-infrared radiation, a previously unknown phenomenon that is likely contributing to the warming of the polar climate,” says the research, which will soon be published in the online edition of the Proceedings of the National Academy of Sciences.

“Far-infrared surface emissivity is an unexplored topic, but it deserves more attention. Our research found that non-frozen surfaces are poor emitters compared to frozen surfaces. And this discrepancy has a much bigger impact on the polar climate than today’s models indicate,” says Daniel Feldman, a scientist in Berkeley Lab’s Earth Sciences Division and lead author of the paper.

Many of today’s spectrometers cannot detect far-infrared wavelengths, which explains the dearth of field measurements. For this reason, scientists have extrapolated the effects of far-infrared surface emissions based on what’s known at the wavelengths measured by today’s spectrometers.

This simulation, from the Community Earth System Model, shows decadally averaged radiative surface temperature changes during the 2030s after far-infrared surface emissivity properties are taken into account. The right color bar depicts temperature change in Kelvin. (Credit: Berkeley Lab)

In the Arctic, the research simulations found that open oceans hold more far-infrared energy than sea ice, resulting in warmer oceans, melting sea ice, and a 2°C increase in the polar climate after only a 25-year run. “The Earth continues to emit energy in the far infrared during the polar winter,” Feldman says, “and because ocean surfaces trap this energy, the system is warmer throughout the year as opposed to only when the sun is out.”

The simulations revealed a similar warming effect on the Tibetan plateau, where there was five per cent less snowpack after a 25-year run. This means more non-frozen surface area to trap far-infrared energy, which further contributes to warming in the region.

The research was supported by NASA and the Department of Energy’s Office of Science.

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