Washington, Sept 27 : Global warming is affecting North America’s northernmost lake, a new study by an international research team of climatologists led by the Université Laval’s Center for Northern Studies, has revealed.

The team led by Warwick Vincent and Reinhard Pienitz reported in their study in the Sept. 28 issue of Geophysical Research Letters that aquatic life in Ward Hunt Lake has undergone major transformations within the last two centuries.

Ward Hunt Lake is a small water body located on a small island north of Ellesmere Island in the Canadian Arctic. Located on the 83rd parallel in the Quttinirpaaq (meaning “top of the world” in Inuktitut) National Park, Ward Hunt Island is completely surrounded by ice. A four-metre layer of ice permanently covers the lake, except for a small peripheral zone that thaws out during a few weeks every summer.

The scientists said the speed and range of these transformations –unprecedented in the lake’s last 8,000 years – suggest that climate change related to human activity could be at the source of this phenomenon.

The researchers say their conclusions are based on the analysis of an 18 centimetres long sediment core extracted in the centre of Ward Hunt Lake in August 2003.

The core contains algae pigments and diatom remnants, which the scientists used as a biological archive for determining the diversity and abundance of aquatic life-forms in the lake over the last 8,450 years.

They said while analysis of the deepest layers of sediment revealed a very small number of algae as well as only minor variations in concentration, the top two centimetres of the core, which correspond to the last 200 years, showed abrupt changes in the lake’s algae population.

During that period, chlorophyll a concentration, a pigment found in every species in the lake, increased by a factor of 500. A type of diatom typical of very cold environments also made its first appearance during the same period, the scientists said.

“The absence of diatoms and the low pigment concentration below the top 2.5 centimetres of the core suggest that the lake was permanently frozen in the past,” said lead author and Center for Northern Studies researcher Dermot Antoniades. (With inputs from ANI)