In early 2016 a spate of sperm whale strandings in the North Sea perplexed scientists. Many theories were proposed for why 29 of the huge marine mammals – all males, most relatively young – died on European beaches in the course of January and the first few days of February, ranging from poisoning by pollutants to climate-change-induced dislocation.
Instead, the authors propose that solar storms threw off the navigation systems of the whales and led them to become lost and stranded. Solar storms, caused by ejections of charged particles from the Sun, disrupt the Earth’s magnetic field, especially near the poles, where they are also responsible for producing auroras.
Lead author Klaus Heinrich Vanselow of Christian-Albrechts-Universität in Kiel, Germany, had earlier found correlations between solar activity and recorded numbers of North Sea sperm whale strandings over several centuries of historical records. The new study is the first to connect specific strandings to specific solar activity, however.
After the early 2016 strandings, the researchers used magnetometer readings in Norway to identify large magnetic disturbances in the area from two solar storms in late December. They believe that these disturbances may have confused the whales, who may normally rely on a “mountain chain” of strong permanent geomagnetism that runs across the northern end of the North Sea to steer them safely away.
Whales heading south through the Norwegian Sea may have accidentally hung a left at the Shetland Islands and find themselves in the shallow waters of the North Sea instead of the open ocean to the west of the UK and Ireland.
The stranded whales were all male, because females stay in warmer waters near the equator while males head for the poles to feed. Vanselow and colleagues believe the reason that most of the stranded whales were younger is that young males, having grown up in the more open waters near the equator where magnetic fields are not disturbed by solar storms, have less experience in navigating in such conditions.
The research is speculative, to a certain extent, as the mechanisms of whale navigation are not well understood and attributing events like whale strandings to a single cause will always be difficult.
The theory is plausible, though: a NASA-funded effort is also under way to sift through massive piles of space weather data and look for correlations with whale strandings around the world.
Michael Lucy is features editor of Cosmos.
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