Glacial–interglacial variability in Atlantic meridional overturning circulation and thermocline adjustments in the tropical North Atlantic

• Published in: Earth and planetary science letters 2010-12, Vol.300 (3), p.407-414
• Main Authors: Lopes dos Santos, Raquel A., Prange, Matthias, Castañeda, Isla S., Schefuß, Enno, Mulitza, Stefan, Schulz, Michael, Niedermeyer, Eva M., Sinninghe Damsté, Jaap S., Schouten, Stefan
• Format: Article
• Language: English
• Subjects: Adjustment; Atlantic meridional overturning circulation; Circulation; Geochemistry; Marine; Modelling; Reconstruction; Strength; TEX 86; thermocline; Thermoclines; U K'37; Water temperature
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2010.10.030

Changes in the strength of Atlantic meridional overturning circulation (AMOC) are known to have profound impacts on global climate. Coupled modelling studies have suggested that, on annual to multi-decadal time scales, a slowdown of AMOC causes a deepening of the thermocline in the tropical Atlantic. However, this process has been poorly constrained by sedimentary geochemical records. Here, we reconstruct surface (U K' 37 Index) and thermocline (TEX H 86) water temperatures from the Guinea Plateau Margin (Eastern tropical Atlantic) over the last two glacial –interglacial cycles (~ 192 kyr). These paleotemperature records show that periods of reduced AMOC, as indicated by the δ 13 C benthic foraminiferal record from the same core, coincide with a reduction in the near-surface vertical temperature gradient, demonstrating for the first time that AMOC-induced tropical Atlantic thermocline adjustment exists on longer, millennial time scales. Modelling results support the interpretation of the geochemical records and show that thermocline adjustment is particularly pronounced in the eastern tropical Atlantic. Thus, variations in AMOC strength appear to be an important driver of the thermocline structure in the tropical Atlantic from annual to multi-millennial time scales. ► Offshore NW Africa, the TEX H 86 temperature proxy reflects thermocline temperatures. ► U k' 37 SST and TEX H 86 are used to examine ΔT, the SST-thermocline difference. ► ΔT, supported by a modelling experiment, reflects AMOC strength. ► Reconstructing ΔT allows reconstruction of past AMOC variations.