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Potential time bomb on NZ shores

Source:  Copyright 2007, New Zealand Press Association
Date:  January 10, 2007
Byline:  Kent Atkinson
Original URL: Status DEAD


A team of international scientists set to sail from Wellington is to investigate big deposits of methane which some overseas researchers view as a potential slow-action time bomb in climate change.

The scientists, on board the German research vessel Sonne, will be working within sight of beach-goers on the North Island's east coast while they probe deposits of frozen methane seen both as a huge new source of natural gas fuel and as a major concern in terms of global warming.

The co-leader of the research voyage, Jens Greinert, a GNS Science geochemist, said scientists worldwide were keen to know the conditions under which methane from the seafloor enters the atmosphere, and the speed of chemical reactions involved in the breakdown of gas hydrates.

Methane hydrates are a solid ice-like form of water that contains methane gas molecules "caged" in tiny cavities. They are usually stable at the sea floor at water deeper than about 500m, and are usually embedded in the first 500m of sediment.

Dr Greinert said yesterday many questions pivoted on whether warming of the oceans could lead to the hydrates breaking down and releasing large amounts of greenhouse gases.

"They definitely have the potential to have a significant influence.. there is a time bomb."

The three-month research voyage was just the start of an extensive investigation of New Zealand gas hydrates which are accessible, occur at a range of depths, actively seep methane into the ocean, and switch from being stable to unstable throughout the year, depending on the temperature of ocean currents.

"The amount here is so high. . . you could say the entire east coast region beween Cook Strait and East Cape is one pavement of gas hydrates along the Hikurangi margins," he said.

The research will take place from the 98m-long Sonne using a variety of video-guided sediment sampling devices and deep sea robots to study the ocean floor.

The voyage, funded mainly by Germany's Research Centre for Marine Geosciences (GEOMAR), involves 27 scientists from 11 research organisations.

Five NZ research institutes will be among the groups probing the physical extent of gas hydrates under the seafloor, the processes that cause their decomposition, and how much methane enters the atmosphere when gas hydrates decompose.

Dr Greinert said it was important to find out how much methane was absorbed into the ocean and how much was consumed by seafloor micro-organisms.

Scientists will use a range of experiments and analysis of the seafloor sediment to answer this question.

Germany alone was investing 55 million euros ($NZ105.3 million) in investigating the likelihood of a major releases of methane from the seabed, and the implications for global warming.

Methane was a powerful greenhouse gas which was – volume-for-volume – 21 times more effective at trapping solar heat than plain carbon dioxide.

Dr Greinert said there was scientific acceptance that gas hydrates released huge amounts to the atmosphere and triggered a major warming of the Earth 55 million years ago.

The warming of 5degC over 10,000 years had impacts that lasted 170,000 years, including mass extinction in the oceans as the water was made more acidic.

"We have to know how far will it go, and how rapidly changes will take place," he said.

"The big questions are scale and speed of greenhouse gas releases to the atmosphere".

"There will be areas where decomposition of gas will be massive, but we don't know if it will be a catastrophic burst," he said.

If changes in temperature and pressure on the sea floor caused large deposits of hydrates to break down, not only was the methane more likely to reach the atmosphere as gas, but the sea floor sediment could slump and possibly trigger tsunamis.

Much of the research voyage would be off the coast of Hawke's Bay. The research could eventually lead to a decision to deploy tsunami warning buoys, not for waves triggered by earthquakes, but massive releases of gas from hydrate deposits.

The voyage until March 24 is just the start of an extensive programme in New Zealand to find out more about gas hydrates, Dr Greinert said.

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