Whales probe Arctic fjord's secrets

Scientists have found a novel way to unravel the mysteries of a fjord in the high Arctic.

They mounted sensors on white whales to measure the salinity and temperature patterns of the fjord during its initial winter freezing.

The measurements revealed a previously unreported inflow of warm water under the ice from the north Atlantic.

The scientists say their experiment in the Svalbard archipelago could work just as well elsewhere.

The scientists, from Norway and the UK, report their innovative data-gathering method in Geophysical Research Letters, published by the American Geophysical Union.

It involved installing satellite-linked conductivity-temperature-depth (CTD) loggers on three white whales (Delphinapterus leucas).

The whales, known also as belugas, dived regularly to the bottom of Storfjorden, off the east coast of the main island of Spitsbergen, reaching areas it would have been difficult to monitor from a ship.

All three animals' instruments collected data, but the transmissions from two were garbled, so the report details the results obtained from the third.

Climate change insights

The CTD profiles it successfully transmitted over 63 days showed that the fjord has a substantial inflow of warm north Atlantic water.

The researchers say this runs contrary to the conventional wisdom that it contains only cold Arctic water.

They say model results suggest the observed Arctic Ocean warming is being caused by an increased flow of north Atlantic water through both the Barents Sea and the Fram Strait.

But it is not clear whether natural variability or long-term climate change is causing the warming.

They say: "CTD measurements from areas such as Storfjorden are crucial for tracking and understanding ocean systems, but these measurements are expensive to obtain and depend on ships.

"However, deployment of satellite-linked CTD loggers on ice-adapted marine mammals may be an effective means to obtain large amounts of data from areas where oceanographic sampling is logistically difficult, in a cost-effective manner."

The data showed the warmest water was in the deepest parts of the fjord, above a layer of cold, more saline water which the authors thought was probably a remnant from dense water formed the previous winter.

Compact instrument carriers

They say this northward flow of warm water "has the potential to have a large influence on the heat content of the water column and therefore also impact ice formation."

They say the whales themselves are "good candidates for carrying CTD loggers".

"They are small enough to capture and handle, while they are large enough to carry early-generation CTD tags without undue stress."

They write: "Observation programmes can utilise suitable 'support staff' to carry satellite-linked CTD equipment (e.g. ringed seals, bearded seals, hooded seals, white whales etc. could sample different Arctic environments).

No reaction

"The information gleaned will also provide very direct habitat information that is hitherto largely unknown for these animals."

One of the scientists involved in the experiment is Ole Anders Nost, of the Norwegian Polar Institute, Tromso.

He told BBC News Online: "The belugas swim very close to the shore, and we simply caught them in nets.

"I was amazed that it was possible to do it at all. They're about 2-4m long, and need several people to hold them in the water.

"We embedded the loggers just beneath the skin in their blubber. We didn't anaesthetise them, but they showed no reaction, and I don't think they felt anything."

Beluga images courtesy of US National Oceanic and Atmospheric Administration