Arctic “unicorns” – year-round residents of western Fram Strait


In brief:

Narwhals live in ice-filled waters of the North Atlantic throughout their lives, similar to their more widely dispersed, circumpolar relative the white whale (or beluga whale). Most research on this remarkable High Arctic animal has taken place in the eastern Canadian/West Greenland area.

Four narwhals (lower right) moving along the edge of the drifting pack-ice east of Greenland.
Photo: Kit Kovacs, Christian Lydersen / Norwegian Polar Institute

By: Heidi Ahonen, Christian Lydersen, Laura de Steur and Kit M Kovacs // Norwegian Polar Institute. Kathleen M Stafford // University of Washington, USA

Satellite-tracking studies have shown that narwhals occupy deep offshore areas in the winter and migrate into coastal areas over the continental shelves in summer. However, in the Barents Sea region, we see them only rarely in coastal areas around Svalbard, regardless of the time of year. They are capable of diving for an hour or more to great depths in search of giant squid and bottom-dwelling fish. They are quite shy and can hear ships at great distances, so they can easily escape detection by leaving the surface for long periods when they choose to “disappear”.

Acoustic spying

To learn more about the Red Listed population of narwhal in the Barents Region, we have been “listening” for them using Passive Acoustic Monitoring (PAM) devices. Recent analyses of several years of PAM records from the western Fram Strait have provided quite amazing results. Narwhal signals were detected year-round (year after year) at a mooring site that sits at the edge of the continental slope east of Greenland (west of Svalbard at about 79°N). Perhaps even more surprising was the fact that the narwhal sounds occurred more frequently when warm Atlantic Water influxes occurred in the area.

Narwhal acoustic signals (hours per day, bottom) in Fram Strait compared to ice cover and distance to the ice edge (top) and % Atlantic Water in the upper 500 m of the water column (middle).

We certainly do not have all the answers (yet) to explain these results, but the presence of narwhal throughout the year in western Fram Strait is likely facilitated by the almost constant flow of drifting fields of Arctic ice, carried southward by the East Greenland Current, creating ideal habitat all months of the year. The increase in acoustic signalling when warm water influxes take place might be associated with the formation of frontal areas, which are created when warm currents meet cold currents. Such fronts likely concentrate narwhal prey.

Spectrogram showing echo clicks and pulsed signals of narwhal, recorded in Fram Strait

 

Authors

Heidi Ahonen, Christian Lydersen, Laura de Steur and Kit M Kovacs // Norwegian Polar Institute

Kathleen M Stafford // University of Washington, USA

Further reading

Ahonen H, Stafford KM, Lydersen C, de Steur L, Kovacs KM (2019) A multi-year study of narwhal occurrence in the western Fram Strait – detected via passive acoustic monitoring. Polar Research (forthcoming)