An international team of researchers has found the evidence of link between the large-scale volcanic event and the large and abrupt cooling of the Earth's temperature during the Jurassic Period, the University of Exeter reported on December 11, 2015.
The Jurassic Period extended across the period of about 201 to 145 million years ago, has been considered as a greenhouse period for a long time. In the era of more recent research, cool and even 'icehouse' episodes have been postulated. The mechanisms of the transition between the so-called Warm Modes and Cool Modes are, however, not well understood yet.
The large volcanic event, so-called the North Sea Dome has restricted the flow of ocean water and the associated heat, carried from equator towards the North Pole region.
The North Sea Dome prevented the ocean flow which has led to an extended Ice age in a period more synonymous with very warm conditions.
"We tend to think of the Jurassic as a warm ‘greenhouse’ world where high temperatures were governed by high atmospheric carbon dioxide contents. This new study suggests that re-organization of oceanic current patterns may also have triggered large scale climate changes," said Professor Stephen Hesselbo from the Camborne School of Mines.
In the Jurassic Period, only one single supercontinent, Pangaea existed, which later split into the seven continents known today. Pangaea had a broad seaway, the Laurasian Seaway, stretching across it, which connected a north Boreal sea to Tethys, a warm equatorial ocean.
The new research utilized a new, large, high quality oxygen-isotope dataset to show the occurrence of an especially abrupt Middle Jurassic mid-latitude cooling of seawater, by as much as 10 °C in the Laurasian Seaway.
The scientists have put 10 years of effort into constructing a record of seawater temperature change, using fossil mollusc shells. Their research showed that during the same period the North Sea Dome occurred and the Earth experienced a significant and fast cooling. The volcanic event might have restricted the poleward flow of ocean water and the transfer of its heat content which in turn changed the climate of the northern hemisphere from very warm to cold. Research results suggest the cold period lasted for millions of years, until the effects of the North Sea Dome subsided.
"Although we have known about the occurrence of cold periods during greenhouse times for a while, their origins have remained mysterious. This work suggests a mechanism at play that may also have been important for driving other climate change events in the Jurassic and at other times in Earth history," Professor Hesselbo concluded.
- "Jurassic climate mode governed by ocean gateway" Christoph Korte, Stephen P. Hesselbo, Clemens V. Ullmann, Gerd Dietl, Micha Ruhl, Günter Schweigert & Nicolas Thibault – Nature Communications (2015) – doi:10.1038/ncomms10015
Featured image credit: Andrés Nieto Porras (Flickr-CC)
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