Decadal-to centennial-scale tropical Atlantic climate variability across a Dansgaard-Oeschger cycle

Abstract

The patterns and forcing mechanisms of climate variability on decadal to centennial time scales represent a major void in our current understanding of Earth's climate system. Furthermore, the response of the low latitudes to abrupt climate change is also not well understood, as most high-resolution paleoclimate studies are from midlatitudes and high latitudes. This study explores the tropical Atlantic response to a Dansgaard-Oeschger cycle (Interstadial 12) using ultra-high resolution (∼2-3 years) foraminiferal census data from Cariaco Basin sediments. The interpretation of the abundance records for the onset of Interstadial 12 is complicated by the competing effects of rising sea level on Ekman-induced upwelling within the Cariaco Basin and migrating Intertropical Convergence Zone-associated variations in trade wind location and fluvial nutrient delivery to the basin. The foraminiferal abundance records for the latter part of the interstadial suggest a southerly shift in the average annual position of the Intertropical Convergence Zone that acted to enhance upwelling and productivity within the Cariaco Basin. Sea level eventually reached a critical point in the transition back to stadial conditions that led to upwelling of nutrient-depleted waters and a decline in productivity within the basin. Spectral analyses of the Globigerina bulloides absolute abundance records reveal significant variability ranging from subdecadal-to centennial-scale. Atlantic multidecadal-scale climate variability is only evident in the warmest interval of Interstadial 12, suggesting that variability on this scale may only operate during warm climate periods, something that has significant implications for modern and near-future climate variability. © 2012. American Geophysical Union. All Rights Reserved.