NZ Volcanic Ash Could Unlock Secrets of Ice Age

NZ volcanic ash could unlock secrets of last Ice Age

Ash from the eruption of North Island volcanoes tens of thousands of years ago has attracted an American-led scientific expedition to New Zealand waters.

A US vessel, Roger Revelle, operated by Scripps Institution of Oceanography (San Diego), leaves Wellington early on Friday morning (26 February). Onboard will be a team of American and New Zealand scientists, including staff from the National Institute of Water & Atmospheric Research (NIWA) and the University of Auckland. They will collect cores of sediment from the seabed east of New Zealand to construct an accurate picture of what the deep water was like at the time of the last Ice Age, 20 thousand years ago.

The voyage leader, Liz Sikes from Rutgers University, says New Zealand is unique because the ash from North Island volcanic eruptions was laid down over wide swathes of the seabed. These layers show up as stripes in the cores of sediment and so act as time markers. “Using the ash layers, we can nail the age of the sediment more precisely than anywhere else in the world,” she says.

The sediment cores contain micro-fossils, called forams, which look like tiny pieces of popcorn. Dr Sikes says it’s a case of ‘you are what you eat’: their shells reflect the chemistry of the water in which they lived. The fossil chemistry and the ash time markers combine to enable scientists to describe what the deep ocean water was like in the past.

“In the last Ice Age, the circulation of water around the world’s oceans changed. This change took as much carbon dioxide (CO2) out of the atmosphere as humans have put in since we started burning fossil fuels. The change in the amount of CO2 dramatically changed the climate, but we don’t understand the details. We’re trying to find out how quickly the change occurred, how much CO2 was there; things that could help us better understand the current global warming,” Liz Sikes says.

The expedition is being funded by the US National Science Foundation.

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