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A record of 300 years of sea-surface temperatures from the Tasman Sea

Past oceanic temperatures in the Australian region

Patrick De Deckker and Jochen Brocks1, Marita Smith [Honours student]1, Sabine Schmidt2 and Stefan Schouten and Raquel Lopez dos Santos3

1 Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
2 Département de géologie et océanographie, Université de Bordeaux I, Talence 33405, France
3 Royal Netherlands Institute for Sea Research [NIOZ], Landsdiep 4 1797 SZ ’t Horntje, The Netherlands

Our project aims at generating high-resolution records of sea-surface  temperature [SST] changes that occurred the oceans surrounding Australia over the last few centuries. We had 2 voyages in 2011 on the Australian Marine National Facility RV Southern Surveyor , with the first one in May in the Tasman Sea [cruise SS2011-T01, from Hobart to Brisbane], whereas voyage 2 did cover the ocean south of Australia [going from Fremantle to Hobart [SS2011-T04 in November 2011].  A variety of innovative proxies are being employed on the samples we collected and will be used for comparison with lake records on mainland Australia. Our objectives are to obtain short cores along the Australian coastline, at approximately 1,000 m water depth, across a broad temperature gradient. The innovation is to use 3 different organic biomarkers [Uk37, TEX86 and DIX] that can be used to reconsruct past SST, backed up with a sound chronology done by  Dr Sabihe Schmidt in Bordeaux.

Preliminary results from the Tasman Sea cruise show that, for the last 300 years, SSTs did not increase uniformly as predicted by the Hockey Stick curve of Mann et al., (2008) but that there are areas of unchanged SST offshore southern Queensland whereas, further south, the last 50 years saw a variety of SST changes, some going up, others going down.

Figure 3. Photograph showing the multicorer being fixed to the rear deck after returning with sediment in the tubes. The sediment-water interface is clearly visible in several of the tubes. The sediments were sliced in half centimeter intervals for a variety of analyses.