Arctic Lake Ice Shrinking With Rising Temperatures, Scientists Claim [VIDEO]

The continued Arctic warming has resulted in a decline in the icy season of the Arctic lakes, claim University of Waterloo scientists who studied more than 400 lakes in Alaska's Arctic coastal plain.

Since the 1980's the rate of Arctic warming has increased, giving rise to a series of complex physical alterations in the region. Based on 20 years of satellite radar imagery, researchers at the University of Waterloo discovered that the acceleration in the Arctic warming is drastically affecting the thickness of the ice of the Arctic lakes.

Due to the extreme alterations in the air temperature and winter precipitation over the last five decades, the thickness, duration and timing of the ice cover on the lakes in the Arctic is changing. The researchers noticed that the lakes freeze up later in the year and melt earlier due to which the winter ice season is 24 days shorter than it was during the 1950's. In the year 2011, the Arctic lake ice was nearly 38 cms thinner than in 1950.

"We've found that the thickness of the ice has decreased tremendously in response to climate warming in the region," said lead author Cristina Surdu, a PhD student of Professor Claude Duguay in Waterloo's Department of Geography and Environmental Management. "When we saw the actual numbers we were shocked at how dramatic the change has been. It's basically more than a foot of ice by the end of winter."

The study was conducted on more than 400 lakes on the Northern Slope of Alaska and this is the first time that the researchers have successfully recorded the magnitude of the rapid changes in the lake ice.

Based on the records of the last five decades from the Barrow meteorological station, the researchers initially expected to trace a drop in the thickness of the ice as well as the grounded ice. But the scientists were surprises at the major decline seen in the last two decades.

Using radar images from the European Space Agency's (ESA) ERS1 and ERS 2 satellites, the researchers studied the ice regimes of the shallow lakes. They noticed that 62 percent of the lakes in the region froze to the bottom in 1992 and in 2011 nearly 26 percent of the lakes froze to bed or the bottom of the lake. There was a 22 percent drop in the ground ice (ice frozen through the lakebed) from 1991 to 2011. This is equal to an overall thinning of the ice by almost 21-38 cm.

Scientists say a rapid decline was seen in the final six years of the analysis, from 2005 to 2011,  according to the ESA website.

The radar signals behave differently depending on the presence and absence of water below the ice. Therefore, they could differentiate completely between a fully frozen lake and one with water. In the presence of water under the ice, the radar signals bounce back but when the lake is frozen the signals get absorbed into the sediments. Frozen lakes appear on the satellite images as dark and those with water appear bright.

For the years when satellite images were not available, the researchers used the Canadian Lake Ice Model (CLIMo) to measure the ice cover and lake ice thickness for years before 1991.

It was seen that the lakes in the region froze over six days later and broke up 18 days earlier during the 2011 winters compared to the winters of 1950. Due to the drop in the ice-cover season, there was a change in the lake algal productivity as well as the melting of the permafrost below the lake beds.

"The changes in ice and the shortened winter affect Northern communities that depend on ice roads to transport goods," said Surdu. "The dramatic changes in lake ice may also contribute to further warming of the entire region because open water on lakes contributes to warmer air temperatures, albeit to a lesser extent than open sea water."

The finding was documented in The Cryosphere.