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Tahiti Sea-Level Expedition 2005

Description

Deep HunterThe Scientifc Goals are

- to reconstruct the sea-level rise following the Last Glacial Maximum, 21 000 years ago, when half of North America and most of Northern Europe were covered by thick ice sheets and sea-level was about 120 metres lower than today:

Instrumental data of climate is available only for the past few decades. Before we can begin to understand the impact that human activity might be having on the present day environment, such as increasing temperatures and rising sea-levels, we must have a clear understanding of the natural variability of climate and sealevel over the last few thousand years.  Since the onset of major glaciations in the Northern Hemisphere about three million years ago, Earth`s climate has, on average, slowly cooled, though the process was neither steady nor gradual. There is evidence of relatively rapid fluctuations from cold (glacial) to warm (interglacial) intervals during which the ice sheets grew and melted. By looking at the changes in sea-level for this interval, scientists can accurately estimate the amount of fresh water in form of ice that was transferred between the continents and oceans during these cycles.

- to reconstruct associated changes in sea-surface temperatures:

The composition of calcium carbonate in coral skeletons can provide information on sea-surface temperatures and sea-surface salinities of the waters the corals lived in. Oxygen (= O) commonly occurs in two stable isotopes, 16-O and 18-O, of which 16-O is much more abundant. There is a correlation between the 18-O/16-O ratio of the carbonate in the coral and past environments, as relatively less 18-O is incorporated into the skeleton at higher temperatures and lower salinities. In addition, minor amounts of metallic elements are contained in corals replacing calcium; less magnesium and more strontium are incorporated into the skeletal carbonate at lower temperatures. By integrating these records of past salinities and temperatures from coral skeletons from various ages and locations, scientists can reconstruct the palaeoceanographic evolution of the tropics.

- to analyze the effects of climatic and sea-level changes on reef building:

Coral reefs are extremely sensitive to environmental changes. As they grow through time they accurately record details of sea-level and climatic changes, no only natural but also human-induced. High-resolution records of past global changes are stored in the geochemical and physical parameters of coral skeletons and reef sequences. These form archives that may be used to understand the long-term behaviour of the tropical ocean-atmosphere system. Corals have strict ecological requirements. They only live in a narrow water- depth range so they can be used as indicators of past sea-levels. Radiometric dating methods also allow them to be used as chronometers so that we gain information on past sea-levels and how fast the sea-level has been changing. Coral records represent an outstanding opportunity to extend sea-surface records beyond historical data and to define natural environmental and climatic variability on times scales ranging from individual seasons to thousands of years. Such records include tropical monsoons and the South Pacific El Nino event, which causes extreme weather around the globe.

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(Photo and text ©:ECORD)

Location

  • Southern Pacific, French Polynesia, Tahiti Islands, 17° 32' S, 149° 36' W

Project Start and End

  • Begin of expedition October 6, 2005
  • End of expedition November 17, 2005

Programs and Funding

  • European Consortium for Ocean Research Drilling
  • Integrated Ocean Drilling Program

Principal Investigators

  • Gilbert Camoin, CEREGE, France
  • Yasufumi Iryu, Tohoku University, Japan

Partners

  • CEREGE, France
  • Université de Montpellier 2, France
  • Tohoku University, Japan
  • University of the Ryukyus, Japan
  • Fukuoka University, Japan
  • University of Tokyo, Japan
  • Institute for Research on Earth Evolution, Japan
  • Britsh Geological Survey, ECORD Science Operator, United Kingdom
  • The Open University, United Kingdom
  • University of Bremen, Germany
  • University of California (SCRIPPS Institution of Oceanography), USA
  • University of Arizona, USA
  • Columbia University (Lamont-Doherty Earth Observatory), USA
  • University of South Florida, USA
  • University of South California, USA
  • Woods Hole Oceanographic Institution, USA
  • Institut de Recherche pour le Développement (IRD), New Caledonia
  • James Cook University, Australia
  • Vrije Universiteit, The Netherlands
  • Seacore Ltd, United Kingdom

Keywords

  • Coral Reefs, Climate Change, Global Environment

Current State

  • drilling operations, science and sampling party have been finalized, scientific evaluations are ongoing