Friday, November 07, 2014
New Mechanism Behind Arctic Warming Revealed
We all know that greenhouse gases contribute to global warming, but new research identifies a new mechanism that could turn out to be a major contributor to melting sea ice, specifically in the Arctic region.
Scientists from the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have studied a long-wavelength region of the electromagnetic spectrum called far infrared. Far infrared is a region in the infrared spectrum of electromagnetic radiation. While it is invisible to our eyes, it accounts for about half the energy emitted by the Earth’s surface.
Despite its importance in the planet’s energy budget, it’s difficult to measure a surface’s effectiveness in emitting far-infrared energy. In addition, its influence on the planet’s climate is not well represented in climate models.
Current models assume that all surfaces are 100 percent efficient in emitting far-infrared energy. However, scientists found that 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.
“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.
Simulations conducted by the researchers revealed that far-infrared surface emissions have the biggest impact on the climates of arid high-latitude and high-altitude regions.
In the Arctic, the simulations found that open oceans hold more far-infrared energy than sea ice, resulting in warmer oceans, melting sea ice, and a 2-degree Celsius increase in the polar climate after only a 25-year run.
This could help explain why polar warming is most pronounced during the three-month winter when there is no sun.
“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.”
Their research appears this week in the online early edition of the Proceedings of the National Academy of Sciences.