The song of the bearded seal and other marvels

In his satirical Devil’s Dictionary, Ambrose Bierce defined the ocean as ‘a body of water occupying about two thirds of a world made for man – who has no gills’. Bierce may have been right to poke fun at human arrogance, but he underestimated the importance of the seas. Averaging almost 3,700 metres (12,000ft) deep, the ocean constitutes around nine tenths of the habitable space on our planet. It plays a commensurate role in the Earth system, not least as an engine – a ‘blue machine’ in the phrase that also titles an excellent book by the physicist and science presenter Helen Czerski – that moves heat around the planet.

The ocean has also been humanity’s get out of jail free card, absorbing more than 90 per cent of the additional heat trapped in the atmosphere by our greenhouse gas emissions. This grace period is, however, probably coming to an end.