Abstract
We analyzed radiocarbon in annual coral bands from the Galápagos Islands in the tropical east Pacific to understand natural variability of past ocean circulation associated with climate change. Variability was observed on El Niño timescales (3–7 years) as well as at decadal and multi‐decadal periods. Low radiocarbon levels persisted for ten years during the early 1600s and for sixteen years during the early 1800s, both coincident with periods of high volcanic aerosol loading in the atmosphere from massive eruptions. Intensification of tropical circulation at this time may be linked to climatically‐controlled changes in the structure of the tropical thermocline that is responsible for delivering cool, upwelled waters to the tropical east Pacific.
Highlights
[2] Radiocarbon (14C) in dissolved inorganic carbon of surface seawater is a tracer of the mixing rate between high 14C surface and lower 14C subsurface waters, and indicates changes in climate
[3] We report a pre-nuclear, annual D14C record from a Galapagos coral (Figure 1) that grew from AD 1587 to 1954
[4] The coral analyzed was age-dated by band counting and verified by U/Th dating at two levels within the 1800s [Dunbar et al, 1994]
Summary
[1] We analyzed radiocarbon in annual coral bands from the Galapagos Islands in the tropical east Pacific to understand natural variability of past ocean circulation associated with climate change. Low radiocarbon levels persisted for ten years during the early 1600s and for sixteen years during the early 1800s, both coincident with periods of high volcanic aerosol loading in the atmosphere from massive eruptions. Intensification of tropical circulation at this time may be linked to climatically-controlled changes in the structure of the tropical thermocline that is responsible for delivering cool, upwelled waters to the tropical east Pacific. B. Dunbar (2007), Oceanic climate and circulation changes during the past four centuries from radiocarbon in corals, Geophys.
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