Past ocean temperatures and coupled U/Th and (super 14) C measurements from deep-sea corals

TitlePast ocean temperatures and coupled U/Th and (super 14) C measurements from deep-sea corals
Publication TypeJournal Article
Year of Publication2011
AuthorsThiagarajan, N, Adkins, J, Eiler, J
JournalMineralogical Magazine
ISSN0026-461X, 0026-461X

Deep-sea corals are a unique archive in paleoceanography. They have large banded skeletons that allow for high resolution records and have a high uranium content allowing for accurate calendar ages independent of radiocarbon age measurements. One problem with using deep-sea corals for long records is that it is difficult to date a large numbers of corals accurately and precisely. Unlike sediment cores, fossil fields of corals have no inherent stratigraphy and each individual coral must be separately dated. Here we present the results of 'reconnaissance radiocarbon age analyses' made at NOSAMS on 519 Desmophyllum dianthus (D. dianthus) collected from the New England Seamounts and South of Tasmania. We will also present the results of 80 more deep-sea corals measured on the Gas-Source AMS also at NOSAMS in WHOI. We find that the coral populations respond to rapid climate change events and are sensitive to climatically driven changes in thermohaline circulation, productivity, [O (sub 2) ] and [CO (sub 3) (super 2-) ]. Once dated however, their use as a paleoceanographic archive is complicated by the isotope and trace-metal disequilibria in their skeletons relative to co-existing seawater. However two tracers that overcome these vital effects are paired U-series and radiocarbon dates and clumped isotope measurements. Here we will present preliminary data of YD and H1 corals from the New England Seamounts collected from 1000-2600m of water depth in the North Atlantic where all three tracers are measured in the same corals. We find that the temperature profile of the ocean during both the YD and H1 coral population is constant with depth. The average potential temperature of the Younger Dryas profile is 1.6 + or - 0.5 degrees C while the average potential temperature of the Heinrich 1 profile is 3.1+ or -0.9 degrees C. If one outlier in the H1 profile is removed the average temperature becomes 2.3+ or -0.5 degrees C. We will discuss implications for salinity gradients in the water column during these time periods as well changes in the circulation of the ocean.