Using Coral Radiocarbon as a Tracer of Atlantic Circulation During the Last 400 Years

Delia Oppo, Geology & Geophysics
Ann McNichol, Geology & Geophysics
Mark Roberts, Geology & Geophysics


OCCI Funded Project: 2010


Ocean circulation influences spatial patterns of sea surface temperature (SST).  Even small changes in SST gradients can influence climate at low latitudes (e.g Vellinga and Wu, 2004).  In the Atlantic Ocean, SST gradients vary on decadal and multi-decadal time scales, in association with the so-called North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO).  Proxy data indicate that Atlantic SST also varies on centennial time scales, with coldest temperatures of the last millennium during centennial scale cold events of the Little Ice Age (LIA ~1400-1900 AD).  The mechanisms causing SST oscillations on these time scales are uncertain, but variations in the Atlantic Meridional Overturning Circulation (AMOC) are prominent candidates for the multidecadal (e.g Vellinga and Wu, 2004) and longer time scales.  Here, we propose to evaluate the link between ocean circulation and SST in the low-latitude western Atlantic using high precision radiocarbon measurements in annually banded corals from the Bahamas, Yucatan, and US Virgin Islands.  More generally, we will evaluate the utility of high precision radiocarbon to provide insight into variations in processes such as advection of low 14C waters by currents, expansion and contraction of the subtropical gyre, and stratification in the low-latitude western Atlantic during the last ~400+ years. For example, what role did changes in local and regional oceanography play in the low-latitude cooling of the Little Ice Age?  Do variations in stratification or in the advection of low 14C water, originating in the equatorial region influence Caribbean and subtropical SST on decadal-centennial time scales?