Arctic spring melt offers insight into fall’s sea-ice extent

Researchers in the UK have discovered a link between spring meltwater and the late summer sea-ice coverage in the Arctic. (FILE PHOTO)

Ponds created by melting ice in the Arctic spring may be the best predictor of sea ice extent later on in the year, a new study suggests.

Scientists from the University of Reading in the UK say they can now forecast how much sea ice will cover the Arctic at the end of the summer by measuring the areas covered by ponds of water earlier in the spring.

The new study, published this month in the journal Nature Climate Change, shows that while the Arctic sea ice has been shrinking in summer months, the size of melt-water ponds has been growing.

And they discovered a clear link between the melt-water and the late summer sea-ice coverage.

Researchers say the melt-water ponds actually contribute to the melting of the ice, as they cause the surface of the ice to absorb 20 per cent more sunlight.

The water pooled atop the ice actually warms the surrounding ice cover, causing it to melt even faster.

In September 1996, when ice was at its highest level since satellites started recording sea ice extent in 1979, ponds had covered just one-tenth of the ice surface.

In 2012, the melt-water ponds covered three times the area.

In less than a decade, the area of the Arctic covered by sea ice by summer’s end has shrunk from around seven million square kilometres in the 1990s, to less than five million.

In September 2012, it reached a record low of less than four million square kilometres.

To forecast the evolution of meltponds, Dr. David Schröder and his colleagues created a computer model based on a 35-year-long simulation.

They discovered that ponds start to form in May, peak by mid-July and then have mostly disappeared by mid-August.

Researchers acknowledge that it’s not possible to forecast September ice extent exclusively from spring melt-pond measurements, because summer temperatures and Arctic Ocean currents are also factors.

But when they used their model to estimate the September 2013 sea-ice extent, their figure of 5.55 million sq. kms was close to the 5.10 million sq. kms measured by the Colorado-based National Snow and Ice Data Center.

University of Reading researchers are now using their climate models to measure melt-pond date from May 2014 to estimate September 2014 sea ice extent.