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JOIDES Resolution probes sea level change

An international expedition of 33 scientists was at sea from 17 November 2009 to 4 January 2010 exploring and drilling into the seabed off the Canterbury coast to study the link between climate and sea level changes over the last 35 million years

The research ship JOIDES Resolution sailed off the coast of Canterbury in water depths of 80–400 metres to collect sediment cores beneath the sea floor at 4 sites across the continental shelf. These cores show sediment layers that preserve a record of ancient climate. These sediments tell the scientists that the Earth’s climate always changes, and the reason for these changes is a subject of ongoing research.

The Integrated Ocean Drilling Program

The ship’s name JOIDES stands for Joint Oceanographic Institutions for Deep Earth Sampling. This expedition is part of the Integrated Ocean Drilling Program (IODP), an international consortium of scientific organisations from 24 countries that operates 2 drilling ships to probe beneath the seafloor for answers to questions on global change.

Two of the drill sites on this expedition broke records for the drilling programme, one being the deepest hole drilled on the shallow shelf (1,024m) and another being the deepest hole drilled on a single IODP expedition (1,928m). The expedition has achieved its aims of recovering a 10-million-year record of sea level cycles across the shelf-slope transect, with 1 drill hole extending back to 35 million years.

In particular, the scientists will use the sediment cores to investigate the relative impact of global climate change and local tectonic forces (earthquakes and plate movement) on the laying down of sediment on the seafloor and changing sea level.

Cores show pattern of ancient climate change

One of the senior geologists on board is Professor Bob Carter, a research professor at Queensland's James Cook University (where he was Professor and Head of School of Earth Sciences between 1981 and 1999) and the University of Adelaide. Professor Carter has recently made headlines around the world for declaring that the United Nation's International Panel on Climate Change (IPCC) should be disbanded and that the December 2009 Copenhagen COP-15 meeting on Climate Change would be a good place to make this start happening.

Scientists, especially from different disciplines, will sometimes not agree on the causes of various phenomena. Climate change is a good example. Professor Carter has been studying climate change (both recent and pre-human) for decades and does not agree with the hypothesis for man-made climate change. Professor Carter says he believes that natural forces are the dominant influence on climate.

In an article to Australia’s Daily Telegraph, Professor Carter wrote:

   

As the core samples from deep underground pass through the logging sensor before me [onboard the JOIDES Resolution], the rhythmic pattern of ancient climate change is clearly displayed. Friendly brown sands for the warm interglacial periods and hostile, sterile, grey clays for the cold glaciations. And for more than 90% of recent geological time, the Earth has been colder than today.

We modern humans are lucky to live towards the end of the most recent of the intermittent but welcome warm interludes. It is a 10,000-year-long period called the Holocene, during which our civilisations have evolved and flourished.

The cores tell the story that this period is only a short interlude during a long-term decline in global temperature – they also warn of the imminence of the next glacial episode in a series stretching back more than 2 million years.

Some core alterations are ruled by changes in the Earth's orbit at periods of 20,000, 40,000, and 100,000 years, others by fluctuations in solar output and others display oceanographic and climate shifts caused by… we know not what.

Climate, it seems, changes ceaselessly: sometimes cooling, sometimes warming, oft-times for reasons we do not fully understand.

Similar cores through polar ice reveal, contrary to received wisdom, that past temperature changes were followed – not preceded, but followed – by changes in the atmospheric content of carbon dioxide.

The role of New Zealand geoscientists

Also onboard the JOIDES Resolution were 3 New Zealand geoscientists – 2 from GNS Science and 1 from the University of Canterbury. Dr Greg Browne from GNS Science helped plan the expedition and worked within a team of 8 sedimentologists. They have the job of translating subtle changes in the amount of sand, mud and limestone into a record of sea level change. Dr Martin Crundwell, also from GNS Science, joined a team of 7 micropalaeontologists who are working to identify the microscopic fossils recovered in the sediment cores. Remains of these tiny marine organisms are used to determine the age of the sediments and the environmental conditions that existed when the organisms were alive.

Dr Kirsty Tinto from the University of Otago is 1 of 2 palaeomagnetists who will analyse the magnetic properties of the sediment cores to identify boundaries across which the magnetic polarity is reversed. These reversals reflect moments in Earth’s past when its magnetic field ‘flipped’. Measurements on the core produce a magnetic ‘barcode’ that is used to match the core with the well dated record of past changes in the Earth’s magnetic polarity.

The research ship refuelled in Wellington in November and docked again in Wellington for several days in early January to collect provisions and a new team of scientists. The ship then sailed to Antarctica to collect sediment cores from the edge of the icy continent. This study will investigate the link between past climate change and the behaviour of the Antarctic ice sheets and the impact this might have had on ancient sea-level changes identified in the cores collected from offshore Canterbury.

Activity idea

See the Science Learning Hub’s earlier news story on the international scientific drilling programme
NZ joins world’s largest geoscience programme

Useful links

Find out more about the JOIDES Resolution.
http://joidesresolution.orgexternal link

Read more about Professor Bob Carter’s work.
http://members.iinet.net.au/~glrmcexternal link

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