Arctic whales are making a contribution to climate science: Scientists used narwhals to help them measure winter temperatures in the waters off western Greenland.
The data recorded by the creatures on their mile-deep dives in 2006 and 2007 showed a continuing temperature increase, the National Oceanic and Atmospheric Administration and the American Geophysical Union reported today (Oct. 27).
A group of researchers attached sensors to 14 narwhals, which are easily identified by their unicorn-like tooth. The whales were tagged as they made their fall migration from northwest Greenland to their wintering grounds in Baffin Bay.
For seven months the sensors on each animal recorded ocean depths and temperatures during feeding dives from the surface pack ice to the seafloor , as far as 1.1 miles below (1.8 kilometers). The narwhal-obtained data will help scientists better understand the impacts of global warming in the Arctic region.
Scientists themselves have had limited opportunities to measure the temperatures of Baffin Bay during winter because of dense ice, harsh conditions and the cost of mounting such missions. Instead researchers over the past decade have been using climatology data (long-term historical average observations) rather than direct ocean measurements.
Narwhals proved they could help researchers to obtain accurate measurements.
During a study into the feasibility of using these whales as lab helpers, researchers found that temperatures were nearly 1.8 degrees Fahrenheit (1 degree Celsius) warmer on average than what climatology data said. Whale-collected temperatures also demonstrated that the winter-surface isothermal layer (a layer of constant temperature) was thinner by 160 to 260 feet (50 to 80 meters) than in the climatology data.
The data obtained from the diving whales was transmitted to satellite once they surfaced.
"Narwhals proved to be highly efficient and cost-effective 'biological oceanographers,' providing wintertime data to fill gaps in our understanding of this important ocean area," said study team leader Kristin Laidre from the University of Washington's Applied Physics Laboratory. "Their natural behavior makes them ideal for obtaining ocean temperatures during repetitive deep vertical dives."
"This mission was a 'proof of concept' that narwhal-obtained data can be used to make large-scale hydrographic surveys in Baffin Bay and to extend the coverage of a historical database into the poorly sampled winter season," Laidre added.
Greenland's western coast is a gateway for fresh water from melting polar ice to flow south to the Labrador Shelf, ultimately affecting the North Atlantic Current. That impact, in turn, is critical for understanding how a changing Arctic affects the transfer of heat globally from the equator to higher latitudes.
"Continued warming will likely have pronounced affects on the species and ecosystem in Baffin Bay and may eventually affect sea ice coverage in the region which in recent years has already retreated significantly," Laidre said. "The timing of the breakup of spring sea ice is ecologically important for many marine species and is linked to primary production which forms the base of the food chain."
The study was published this week in the Journal of Geophysical Research Oceans.
In addition, the narwhal missions are recorded at http://oceanexplorer.noaa.gov/explorations/06arctic/welcome.html.