"Paul Holland, a climate modeler with the British Antarctic Survey, has spent the last ten years studying Antarctica’s sea ice and the Southern Ocean.
... Holland thinks these seasons may be a key to a conundrum: If Earth’s temperatures are getting warmer and sea ice in the Arctic has been shrinking fast, why then is sea ice in the Antarctic slowly increasing?
Sea ice is simply frozen seawater.
Although found only in the Arctic and the Antarctic, it influences Earth’s climate in big ways.
Its bright surface reflects sunlight back into space.
Icy areas absorb less solar energy and remain relatively cool.
... Scientists have been watching this feedback loop of warming and melting in the Arctic.
To them, Arctic sea ice is a reliable indicator of a changing global climate.
... Antarctic sea ice, on the other hand, has not been considered a climate change indicator.
Whereas Arctic sea ice mostly sits in the middle of land-locked ocean—which is more sensitive to sunlight and warming air—Antarctic sea ice surrounds land and is constantly exposed to high winds and waves.
According to climate models, rising global temperatures should cause sea ice in both regions to shrink.
But observations show that ice extent in the Arctic has shrunk faster than models predicted, and in the Antarctic it has been growing slightly.
To Holland, the discrepancy calls parts of the climate models into question.
Modeling groups from around the world collaborate on the Coupled Model Intercomparison Project Phase 5 (CMIP5), which simulates Earth’s climate and predicts how it will change in the near future.
... “Almost all of the CMIP5 models produce a decrease in Antarctic sea ice,” Holland said.
“There is a problem in the bit that reproduces the last 30 years of sea ice variability.”
Most studies on Antarctic sea ice trends focus on changes in ice extent.
For Holland, it was more important to look at how fast the ice was growing or shrinking from season to season.
Holland used data from NASA's National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC) to calculate the ice concentration rate of growth for each single day, which he called intensification ...
... Holland found that winds were spreading sea ice out in some regions and compressing or keeping it intact in others and that these effects began in the spring.
It contradicted a previous study in which, using ice drift data, Holland and Ron Kwok from the NASA's Jet Propulsion Laboratory (JPL) found that increasing northward winds during the autumn caused the variations.
... “Partial explanations have been offered, but we don’t have the complete picture,” said Ted Scambos, a scientist at NSIDC DAAC.
