Radiocarbon Profiles and Rapid Climate Change in the Deep North Atlantic: Deep Sea Corals from the Glacial to the Holocene

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Abstract: Under this award the PI proposes to use coupled U-series and 14C dates from deep-sea corals to directly measure the 14C/12C ratio (14C) of the past deep ocean. This should give an indication of the history of the strength of Atlantic overturning circulation which is a critical element in understanding climate change. The PI has collected a suite of coral samples from the New England Seamounts over a depth range of ~1,100-2,500 meters. In the collection there are over 3,700 individual samples of our main species, D. cristagalli, and over 60 kg of another species, Solenosmilia sp. From the first 100 U-series dates it is clear that about 30% of the collection covers the radiocarbon age window. With many samples from a key depth interval, and spanning the LGM to the early Holocene, the proposal outcome will be multiple profiles of 14C from the past North Atlantic. In addition, high-resolution 14C age sampling within single coral skeletons can constrain the rates and timing of deep-water mass transitions. Independent U-series age control allows these well-dated water mass reorganizations to be compared to any other well dated climate archives. Two types of data sets will be produced; profiles from many corals with the same age but different depths, and time-series from several corals of overlapping age at the same depth. These two types of .14C reconstructions will be compared to ice core records of rapid climate change and records of atmospheric .14C that contain both deep circulation rate and carbon cycle change information. From the ice core (and stalagmite) comparisons the PI will determine the phasing of the deep ocean and the atmosphere during rapid climate.