Antarctic volcanic eruptions linked to abrupt climate changes

New York, Sep 5 (IANS) A series of volcanic eruptions in the Antarctica coincided with increased deglaciation and rise in global greenhouse gas concentrations about 17,700 years ago, says a study.

"Detailed chemical measurements in Antarctic ice cores show that massive, halogen-rich eruptions from the West Antarctic Mt. Takahe volcano coincided exactly with the onset of the most rapid, widespread climate change in the Southern Hemisphere during the end of the last ice age," said Joseph McConnell, Professor at the Desert Research Institute (DRI) in Nevada, US.

Climate changes that began approximately 17,700 years ago included a sudden poleward shift in the westerly winds encircling Antarctica with corresponding changes in sea ice extent, ocean circulation and ventilation of the deep ocean.

Evidence of these changes is found in many parts of the Southern Hemisphere and in different paleoclimate archives, but what prompted these changes has remained largely unexplained.

"We postulate that these halogen-rich eruptions created a stratospheric ozone hole over Antarctica that, analogous to the modern ozone hole, led to large-scale changes in atmospheric circulation and hydroclimate throughout the Southern Hemisphere," McConnell said.

Furthermore, the fallout from these eruptions - containing elevated levels of hydrofluoric acid and toxic heavy metals - extended at least 2,800 kilometres from Mt. Takahe and likely reached southern South America.

For the study, McConnell's ice core laboratory enabled high-resolution measurements of ice cores extracted from remote regions of the Earth, such as Greenland and Antarctica.

One such ice core, known as the West Antarctic Ice Sheet Divide (WAIS Divide) core was drilled to a depth of more than 3,405 metres, and much of it was analysed in the Desert Research Institute Ultra-Trace Laboratory for more than 30 different elements and chemical species.

Additional analyses and modelling studies critical to support the authors' findings were made by collaborating institutions around the US and world.

"These precise, high-resolution records illustrate that the chemical anomaly observed in the WAIS Divide ice core was the result of a series of eruptions of Mt. Takahe located 350 kilometres to the north," Monica Arienzo, Assistant Research Professor at DRI, said.