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Methane shock tilted the Ocean - Nature article of a marine scientist from Bremen

October 19, 1999

Up until now, scientists had to rely upon assumptions: at some point in time, on the boarder between the Paleocene and the Eocene 55 million years ago, the ocean lost its balalance. All of a sudden about 70% of all the foraminifera living on the seafloor became extinct. Just as suddenly, new, up until then unknown species of these calcareous-shelled micro-organisms moved around in the water column, whilst large areas of the deep sea were transformed into unsuitable living zones. At the same time, the continents experienced a biological revolution: Primates and other mammals emigrated from the tropical-subtropical latitudes to North America, and crocodiles lived in the Arctic.

All these upheavals on land and in the ocean possibly happened together with enormous slides of the undersea shelves, maybe because the methane ice in the seafloor became unstable. Within just a few thousands of years between 1,200 and 2,000 billion tons of the greenhouse gas methane was released into the ocean and atmosphere. The subsequence was a temperature shock. The deep water in the middle depths of the ocean, which was relatively warm anyway, was warmed to a temperature of 15° Celsius (today: a cool 2 - 4°Celsius).

In an investigation which will be published in the next issue of „Nature„ on October 21, the geoscientist Dr. Ursula Röhl from Bremen University and Dr. Richard D. Norris from the Woods Hole Oceanographic Centre will prove for the first time, that this natural catastrophe paved its way within only a few thousand years, perhaps even less, and reached ist height after 30,000 years. It took 120,000 years until the climate had recovered from the methane shock and got back into a new state of balance. The investigations also make it possible for the first time to classify the actual date of the methane shock: It began 54,950 million years ago.

Says Dr. Ursula Röhl from the Department of Geosciences: „We owe our new knowledge to a drilling core from the western Atlantic.„ It was drilled using the equipment on the research vessel „JOIDES RESOLUTION„ around 500 kilometers west of Florida in a water depth of 1,980 m. The core is today stored at the Core Depository of the international Ocean Drilling Program in Bremen. „The sediments from the sea floor make us witnesses of a dramatic, but natural climate experiment. Now it is up to us to incorporate this knowledge in the new research programme on gas hydrates in the geosystem, which the German Research Ministry is just imposing„.

Mr Albert Gerdes
MARUM - Centre for Marine Environmental Research at the University of Bremen
agerdes@marum.de
0049 - 421 - 218-7761
Nature
Vol. 401, October 21st, 1999



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