Just going about their business, but that suits researchers just fine (Image: Flip Nicklin/Getty)

Narwhals diving nearly 2 kilometres below polar ice have revealed that climatology models used for the Baffin bay region – which links the Atlantic and Arctic oceans – underestimate winter ocean temperatures there by as much as 1 °C.

The new data gathered from narwhals tagged with a temperature-depth gauge and satellite transmitter – a package around the size of a deck of cards – show that earlier warming between Greenland and the Baffin Islands of Canada has continued over the last decade.

They provide the best winter temperature measurements yet for this biologically important part of the Arctic Ocean, and add to a body of data showing that ocean temperatures around the world are warming.


The Arctic mammals, known as “sea unicorns” thanks to their single long tusks, also transmitted measurements for the winter layer of surface water that shields sea ice from the warmer waters below. On average The thickness of this layer of water, or isotherm, varies throughout the region, but the narwhal data show it to be 50 to 80 metres thinner than the climatology models, according to Kristin Laidre of the Polar Science Center at Washington University in Seattle, and her colleagues, who carried out the study.

A thinner isotherm allows faster turnover of warmer waters from below, which speeds ice-melt. The process is self-perpetuating: as ice melts, the ocean absorbs more heat and melts more ice, and so on.

Ice-free summers

“Their findings indicate that the transfer of atmospheric heat into the oceans may be higher than we thought,” says climatologist Walt Meier of the National Snow and Ice Data Center at the University of Colorado at Boulder, who was not involved in the study.

Baffin bay is an unusually abundant zone of the Arctic Ocean, rich in fish and aquatic mammal species that are considered vulnerable to climate change, but the waters there remain poorly sampled with almost no measurements during winter when it is difficult and expensive to navigate. As a result, climatology models for the region have been based on summer data and are unreliable.

Now, data from three winters of narwhal-gathered measurements in December to March of 2005, 2006 and 2007 finds that the models are out by a whole degree on average. However, the narwhal measurements do correlate well with one-shot samples taken by winter helicopter surveys. The warmest temperatures recorded by the whale oceanographers was 4.6 °C at depths of 380 to 580 metres.

“One degree Celsius above the climate model is significantly warmer and shows that the models may not be sensitive enough to be useful,” Meier says.

Ideal researchers

Laidre’s team began taking measurements in 2005, by capturing 14 narwhals (Monodon monoceros) in nets and attaching the electronic gear to the animals’ dorsal fins.

Narwhals frequently dive to deep waters – the deepest recorded in this study was 1773 metres. They return regularly to the surface (when the data is sent via polar-orbiting satellites) and are untroubled by surface ice.

The animals are “highly efficient and cost-effective”, Laidre says, and they always return to the same wintering ground, so there is a geographical consistency in the data they record. And they don’t require feeding or payment. In short, they are perfect accomplices.

Journal reference: Journal of Geophysical Research, DOI: 10.1029/2009JC005820

Update: Since we originally published this article, it has been updated to provide more detail about sampling and climatology models