Millennial‐scale sea surface temperature variability in the western tropical North Atlantic from planktonic foraminiferal census counts

Abstract

Abstract. Planktonic foraminiferal census counts are used to construct high-resolution sea surface temperature (SST) and subsurface (thermocline) temperature records at a core site in the Tobago Basin, Lesser Antilles. The record is used to document climatic variability at this tropical site in comparison to middle-and high-latitude sites and to test current concepts of cross-equatorial heat transports as a major player in interhemispheric climate variability. Temperatures are estimated using transfer function and modern analog techniques. Glacial -maximum cooling of 2.5ø-3øC is indicated; maximum cooling by 4øC is inferred for isotope stage 3. The SST record displays millennial-scale variability with temperature jumps of up to 3øC and closely tracks the structure of ice-core Dansgaard/Oeschger cycles. SST variations in part of the record run opposite to the SST evolution at high northern latitude sites, pointing to thermohaline circulation and marine heat transport as an important factor driving SST in the tropical and high-latitude Atlantic, both on orbital and suborbital timescales.

Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures

“…3A), consistent with previous temperature reconstructions from the western TNA (11)(12)(13)28) (Figs. 3E and 4A).…”

“…However, the validity of the modeling results during past abrupt climate events, when AMOC was significantly weakened, has not been fully tested because of a lack of high-resolution paleoproxy subsurface records. Most proxy reconstructions in the TNA are for sea surface temperature (SST), and these records tell an inconsistent story: Some indicate a surface cooling during the Younger Dryas (YD) cold period (9, 10) whereas others suggest SSTs increased (11)(12)(13). The only existing deglacial proxy records of intermediate-water change in the western TNA are a benthic foraminiferal δ 18 O record from the Tobago Basin at approximately 1.3 km depth (14) and a benthic foraminiferal Mg/Ca record from the Florida Straits at approximately 750 m depth (15).…”

Coupling of millennial‐scale changes in sea surface temperature and precipitation off northeastern Brazil with high‐latitude climate shifts during the last glacial period

“…For the tropical Atlantic Ocean, there is equivocality about the evolution of surface temperatures associated with rapid and large millennial-scale reorganizations of the thermohaline circulation during the last glacial period. Sea surface temperature (SST) records from the north Brazilian continental margin [Arz et al, 1999;Weldeab et al, 2006], the Tobago Basin [Rühlemann et al, 1999;Hüls and Zahn, 2000], the western Caribbean Sea [Schmidt et al, 2004], and the Gulf of Mexico [Flower et al, 2004] suggest warming of the western tropical Atlantic and the Caribbean Sea during Heinrich event H1 and the Younger Dryas although significant differences exist with respect to timing and magnitude of the SST changes. In contrast, SST reconstructions from the Cariaco Basin indicate deglacial temperature variability in synchrony with the northern high latitudes [Lea et al, 2003].…”

“…On one hand, for a Ceará Rise sediment core, Curry and Oppo [1997] inferred cooling of the western tropical Atlantic during periods of reduced overturning circulation from analysis of stable oxygen and carbon isotopes, determined on co-occurring planktic and benthic foraminifera. On the other hand, Hüls and Zahn [2000] derived SSTs from planktic foraminiferal transfer functions and suggested warm anomalies during several Heinrich events for a high-resolution sediment core from the Tobago Basin.…”

Eastern tropical Pacific hydrologic changes during the past 27,000 years from D/H ratios in alkenones

“…[47] Times of high-northern latitude cooling during H events are associated with enhanced northeasterly trade winds [Andreasen and Ravelo, 1997;Dahl et al, 2005;Hughen et al, 1996] (Figure 9 and Appendix A) and tropical to southern-subtropical Atlantic warming (including the Cariaco Basin, the Caribbean and the Gulf of Mexico [Flower et al, 2004;Hüls and Zahn, 2000;Rühlemann et al, 1999;Schmidt et al, 2004;Weldeab et al, 2006]). These conditions are favorable for a strengthening of lowlevel winds crossing Central America from the Atlantic to the Pacific (Figure 9 and Appendix A) [Xie et al, 2007;Xu et al, 2005].…”