PLUTOTRACE

Plutonium bio-signature as tracer of climate changes in ocean transport

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 Obiettivo del progetto (Objective)

'Climate change has significant consequences for the marine environment, for example, increasing transport of warm water from the tropical Pacific to the temperate seas of NW Pacific. The plutonium isotopic signature recorded in corals and bivalve shells will be utilised to trace temporal alteration in the ocean mixing over the past 50 years in the NW Pacific. The sampling and analytical techniques for mass spectrometric measurements of Pu in coral and bivalve shell samples will be optimised for high temporal resolution. In addition, the relationship between surface seawater Pu and the mixed layer depth will evaluated and the findings will be applied to determine the past variation of the mixed layer depth and sea surface temperature in the NW Pacific from the coral layers. The historical Pu isotopic signature in the outflow from the Irish Sea, including Sellafield releases and the now dominant contribution from the contaminated seabed, into the NE Atlantic will be determined by analysing bivalve shells from the Irish Sea and the North Channel. This proposal includes fieldwork at the proposed sites and subsequent analyses using mass spectrometric techniques and radiometric methods. Data analyses and evaluation of results will be jointly carried out physical oceanographers and marine scientists. In addition, the researcher will receive practical training in sampling techniques, mass spectrometric methods and ocean modelling as well as basic marine ecology. The combination of oceanographic observations and tracer measurements will provide insights into the response of the ocean circulation to climate change. The proposal involves an outgoing phase of two years at the Korea Ocean Research and Development Institute and a returning phase of one year at the University of Plymouth.'

Introduzione (Teaser)

Climate change can have serious consequences for marine environments by increasing the movement of warm water from the tropics to cooler regions. An EU-funded project has investigated traces of plutonium in corals and seashells to determine changes in the movement of currents in the Pacific Ocean over the last 50 years.

Descrizione progetto (Article)

Scientists from the 'Plutonium bio-signature as tracer of climate changes in ocean transport' (Plutotrace) initiative have tested the hypothesis that concentrations of plutonium (Pu) in the surface water are related to the depth of the mixed layer. This layer is where turbulence is generated as a result of wind, cooling and other processes.

Project partners have used a technique based on mass spectrometry (MS) to determine isotope ratios in corals and shells. Samples of coral were obtained with the aid of Japanese and Korean partners from three sites in the north-west Pacific.

Sampling sites were situated along the path of the North Equatorial Current (NEC) and the Kuroshio Current (KC). Seasonal growth layers of coral were analysed using MS to reveal changes in the Pu isotope ratio over space and time.

Coral analysis has enabled scientists to reconstruct past surface mixed layers in areas subject to the NEC and KC and compare the results with past sea surface temperatures. The findings have been used to build a model showing changes in water mass transport from the tropical Pacific to the north-west Pacific.

The work of the Plutotrace project has enabled scientists to study ocean current changes resulting from climate change. The techniques developed can be used by researchers studying the oceans in other parts of the world to help obtain a clearer picture of the marine effects of the changing climate.