Oceans are heating up at the double
The British survey ship HMS Challenger blazed an oceanic trail a century and a half ago.
Image: William Frederick Mitchell via Wikimedia Commons
LONDON, 6 February, 2016 – Ocean temperatures first collected during one of the great 19th-century voyages of exploration confirm one of the consequences of climate change: humans have managed to warm even the deepest parts of the ocean.
A new study in Nature Climate Change calculates that the amount of heat absorbed by the ocean has doubled in the last 18 years. A third of this heat has collected in the depths at least 700 metres below the waves − and the same region is rapidly getting hotter.
Peter Gleckler, a research scientists at the Lawrence Livermore Laboratory in California, and colleagues started with data collected by the world’s first modern oceanographers aboard the British survey ship HMS Challenger in 1872-76.
Deep-sea soundings
Challenger circumnavigated the globe, sailed 70,000 nautical miles (130,000 kilometres), collected 4,700 new species, and made 492 deep-sea soundings and 283 sets of measurements of water temperatures.
With such systematic findings, the American research team could begin to make estimates of how ocean temperatures have changed between 1865 and 2015.
They calculate that, since 1970, around 90% of the Earth’s uptake of heat associated with man-made global warming, as a consequence of greenhouse gas emissions from fossil fuel combustion, has been absorbed by the oceans.
In effect, they have used the evidence collected from the depths by 19th-century scientists aboard a three-masted, square-rigged wooden ship to settle a 21st-century puzzle: where has the heat from global warming actually gone?
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