Why Drill Tahiti Coral Reefs?

image of Tahiti leaflet Coral reefs are sensitive recorders of past sea level and environmental changes. Their accurate dating by mass spectrometry is of prime importance for the determination of the timing of deglaciation events and thus for the understanding of the mechanisms driving glacial-interglacial cycles.

The IODP Expedition 310 Tahiti Sea Level sought to establish the course and effects of the last deglaciation on the subsiding volcanic island of Tahiti (subsidence rates : 0.25mm.yr-1), at a considerable distance from former ice sheets.

The scientific objectives of the expedition were :

1.  To reconstruct the general pattern of sea-level rise during the last deglaciation events in order :

1) to establish the amplitude of the maximum lowstand during the Last Glacial Maximum ; 2) to assess the validity, the timing and amplitude of meltwater pulses (so-called MWP-1A and MWP-1B events; c. 13,800 and 11,300 cal. yr BP) which are thought to have induced reef-drowning events and to have disturbed the general thermohaline oceanic circulation and, hence, global climate ; 3) to test predictions based on different ice and rheological models.

2.  To identify and to establish patterns of short-term paleoclimatic changes

that are thought to have punctuated the transitional period between present-day climatic conditions following the Last Glacial Maximum in order to get a better knowledge of : 1) the regional variation of sea surface temperatures in the south Pacific; 2) the climatic variability and the identification of specific phenomena such as El Nino-Southern Oscillation (ENSO); 3) the global variation and relative timing of post glacial climate change in the southern and northern hemisphere.

3.  To analyse the impact of sea-level changes on reef growth, geometry and biological makeup,

emphasizing : 1) the impact of glacial meltwater phases (identification of reef drowning events); 2) the morphological and sedimentological evolution of the foreslopes (highstand vs lowstand processes); 3) the modeling of reef building; 4) environmental changes during reef development.

Gilbert Camoin, Co-chief Scientist