Global warming 55 million years ago shifted ocean currents

0 Comments – January 4, 2007

This article details a study regarding global warming that occurred 55 million years ago and the very dramatic and long-term changes that appeared to be caused.  It is a very interesting study that should be understood to be “theory” and not fact.  It is great reading if you want to understand what could occur if the earth’s temperature increased dramatically.

An extraordinary burst of global warming that occurred around 55 million years ago dramatically reversed Earth’s pattern of ocean currents, a finding that strengthens modern-day concern about climate change, a study says.  The big event, the Palaeocene/Eocene Thermal Maximum (PETM), saw the planet’s surface temperature rise by between five and eight degrees C (nine and 16.2 F) in a very short time, unleashing climate shifts that endured tens of thousands of years.

With a painstaking reconstruction, Nunes and Norris found that the world’s ocean current system did a U-turn during the PETM — and then, ultimately, reversed itself.  Before the PETM, deep water upwelled in the southern hemisphere; over about 40,000 years, the source of this upwelling shifted to the northern hemisphere; it took another 100,000 years before recovering completely.

What unleashed the PETM is unclear. Most fingers of blame point to volcanic eruptions that disgorged gigatonnes of carbon dioxide, or coastal reservoirs of methane gas, sealed by icy soil, that were breached by warmer temperatures or receding seas.

The suspected reason for this is an inrush of freshwater into the northern Atlantic, caused by melting glaciers in Greenland and melting sea ice, and higher flow into the Arctic from Siberian rivers caused by greater rainfall.

The influx brakes the conveyor belt in which warm surface water is taken up to the northeastern Atlantic from the tropics before returning down to the southern hemisphere as cool, deep-sea water.

The higher the level, the greater the risk that a vicious circle of global warming could be unleashed, inflicting potentially irreversible damage to Earth’s climate system, scientists say.

Read the article here.

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