Age Screening of Deep-Sea Corals and the Record of Deep North Atlantic Circulation Change at 15.4ka

Abstract

Uranium rich, density banded deep-sea corals are a new archive of deep ocean behavior on decadal time scales. Large numbers of samples can be rapidly and inexpensively screened for their-ages using an Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) technique. With this new method, 300 samples have been sorted into 5,000 year age bins and several dozen of these are useful for coupled precise uranium series and radiocarbon dating. Together with Cd/Ca data from a single coral's skeleton, these coupled ages show that there was a rapid and large shift in the deep circulation of the western north Atlantic at 15.4ka and 1,800m depth. This deep-sea coral signal, also found in sediment records from around the Atlantic, leads the Bolling/Allerod warming in the Greenland ice cores by 840 ± 340 years. Coupled ages from the two dating methods in the corals also constrain the southern source deep waters to be about 600 years older than their initial value just prior to 15.4ka. This result is in contrast to the modern Atlantic where western basin deep waters are on average 100 years old or less.