A centennial-scale variability of tropical North Atlantic surface hydrography during the late Holocene

Abstract

Sea-surface temperature (SST) and sea-surface salinity (SSS) fluctuations in the northeastern Caribbean have been reconstructed through the last 2000 yr using an artificial neural network and δ18O analyses of planktonic foraminifera. A warmer period prevailed in the NE Caribbean from AD ∼700–950, which may reflect the occurrence of stronger and/or more frequent El Niño events. A ∼2°C cooling of winter SSTs, from AD ∼1400 to 1550, coincides with the occurrence of reduced solar output, the Spörer event. Episodes of lower SSSs with marked minima at the onsets of the Dark Ages in Europe (AD ∼500–600) and Little Ice Age (AD ∼1400) are cyclically recurrent at intervals of 200–400 yr, and coincide with drier periods in Mexico. This may indicate that the tropical Atlantic evaporation–precipitation budget and SSSs are affected by a centennial-scale modulation involving the freshwater export (import) from (into) the Atlantic Ocean. Coeval changes recorded in the deep North Atlantic circulation indicate that low-latitude SSS anomalies may be advected polewards by the North Atlantic current system, thus affecting deep-ocean convection and strength of the thermohaline circulation.