HR: 10:35h
AN: PP12B-02    [Abstracts]
TI: Probing the Climate of the Western Pacific Warm Pool During a Perturbed Thermohaline Circulation (10-60 Ka) Using Oxygen Isotopes From Long Lived Fossil Bivalves
AU: * Welsh, K J
EM: kevin.welsh@glg.ed.ac.uk
AF: School of GeoSciences, University of Edinburgh, Grant Institute, Kings Buildings, West Mains Rd., Edinburgh, EH9 3JW United Kingdom
AU: Elliot, M
EM: mary.elliot@glg.ed.ac.uk
AF: School of GeoSciences, University of Edinburgh, Grant Institute, Kings Buildings, West Mains Rd., Edinburgh, EH9 3JW United Kingdom
AU: Chappell, J
EM: john.chappell@anu.edu.au
AF: Research School of Earth Sciences, The Australian National University, Building 61, Mills Road, Canberra, ACT 0200 Australia
AB: The last glacial climate was punctuated by a number of abrupt climatic events: the Heinrich Events. These are associated with reduced North Atlantic Deep Water (NADW) formation, rises in sea level of between 10 and 30m and are known to have had global climatic impacts. These rises in sea level created accommodation space for coral reefs to grow vertically. In Papua New Guinea, rapid uplift along the coast of the Huon Peninsula (up to 4m/ 1000 years) has caused these reefs to be uplifted and sub-aerially exposed. The reefs have been extensively dated and some of the reefs have been shown to be coeval with Heinrich Events. Therefore, these terraces present unprecedented opportunities to investigate the climate of the Western Warm Pool during a reduced NADW formation. The reefs at Huon contain abundant, well preserved Tridacna sp. which can be found in their growth position over grown with coral. Tridacna sp. are long lived (10-60 years) reef dwelling bivalves. They secrete aragonite in annual growth bands which, unlike corals, have been shown to precipitate in isotopic equilibrium with sea water, and in consequence are excellent recorders of average climate in palaeo-reefs. Here we present records of oxygen isotopes obtained from a set of 30 fossil Tridacna sp. found in their growth position in the uplifted fossil terraces at Huon Peninsula. Oxygen isotopes of these fossil bivalves reflect temperature, the evaporation/ precipitation balance of the water in which it is precipitated and is also affected by sea level at the time of deposition. Studies of modern climate show that temperature and precipitation increase and decrease together over the seasonal and inter-annual cycle. The samples were dated using radiocarbon dating. XRD measurements and SEM imagery were used to test for diagenesis. Oxygen isotope ratios were measured from powdered samples milled across the growth banding of the clams, which represent average conditions of temperature and salinity during the life of the clam. By extracting the sea level component we found that the reefs coeval with Heinrich Events were less enriched in ¹⁸O than those that were not. Therefore, our data suggests that the palaeoclimate of the Western Warm Pool was warmer and wetter at Huon Peninsula during these periods of perturbed thermohaline circulation. If interpreted in terms of temperature alone this is the equivalent of approximately 1° C, which is 30% of the LGM/ Holocene temperature change in this area.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4926 Glacial
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005