Radiocarbon Reservoir Age of High Latitude North Atlantic Surface Water During the Last Glacial

The radiocarbon reservoir age of high latitude North Atlantic Ocean surface water is essential for linking the continental and marine climate records, and is expected to vary according to changes in North Atlantic Deep Water (NADW) production. Measurements from this region also provide important input and/or tests of oceanic radiocarbon using 3-D global ocean circulation models. Here, we present a surface water radiocarbon reservoir age record of the high latitude western North Atlantic for the deglacial period via the use of fossil cold-water corals growing in waters that are rapidly exchanged with nearby surface waters. The reservoir age of high latitude North Atlantic surface waters was computed from the radiocarbon age difference between our radiocarbon calibration record (http://radiocarbon.LDEO.columbia.edu) and our marine radiocarbon data. Th/U/U dates provide the absolute coral ages. Our high latitude North Atlantic Ocean reservoir age data combined with recalculated reservoir ages based on published coexisting terrestrial and marine material or Vedde ash radiocarbon dates from central and eastern North Atlantic shows modern values (380 ± 140 year, n = 14) during the Bolling and Allerod warm period and a 200 year increase in reservoir age (590 ± 130 year, n = 10) during the entire Younger Dryas (YD) cold episode. The reservoir age then decreased to 270 ± 20 year (n = 2) at the Preboreal/YD transition, although the dates are too sparse to be confident in this estimate. We are not able to resolve the timing of the transition to increased reservoir ages from the mid-Allerod to the YD due to the relatively small change and correspondingly large uncertainty in the estimates. The atmospheric ∆C record derived from our atmospheric radiocarbon record displays a 40 per mil increase from 12900 to 12650 cal year BP, coincident with the shift to high reservoir ages