An 8‐century tropical Atlantic SST record from the Cariaco Basin: Baseline variability, twentieth‐century warming, and Atlantic hurricane frequency

Abstract

[1] We present the first direct comparison and calibration of a downcore foraminiferal Mg/Ca record to historical instrumental sea surface temperature (SST). Mg/Ca measured on the planktic foraminifer Globigerina bulloides from a Cariaco Basin sediment core strongly correlate with spring (March-May) instrumental SSTs between A.D. 1870 and 1990. A Mg/Ca SST equation is derived and a paleo-SST record is presented spanning the last 8 centuries, an interval that includes the end of the Medieval Warm Period and the Little Ice Age. The long-term record displays a surprising amount of variability. The temperature swings are not necessarily related to local upwelling variability but instead represent wider conditions in the Caribbean and western tropical Atlantic. The Mg/Ca SST record also captures the decadal and multidecadal variability observed in records of global land and sea surface temperature anomalies and Atlantic tropical storm and hurricane frequency over the late nineteenth and twentieth centuries. A divergence between the SST proxy record and Atlantic storm frequency around 1970 appears to reflect a fundamental change in Atlantic hurricane behavior noted in historical data. On average, twentieth-century temperatures are not the warmest in the entire record, but they do show the largest increase in magnitude and fastest rate of SST change over the last 800 a.

Shipwreck rates reveal Caribbean tropical cyclone response to past radiative forcing

“…A combination of proxy records suggests that the states of these climate factors converged during the Little Ice Age, and the MM in particular, to create a drastically unfavorable environment for CTC development. The distinct reduction in CTC activity during the MM can be attributed to cool absolute SSTs in the Caribbean (34,35) and in the main development region (36): warmer ocean waters provide more thermal and kinetic energy and thus increase the potential for a greater number of severe storms (31) (Fig. 3E).…”

Historical records of coastal eutrophication-induced hypoxia

“…Because of high sedimentation rates, coastal records can often be examined at subdecadal or even shorter (annual or seasonal) time scales Rabalais et al, 1996). For example, Black et al (2007) presented an eight-century record of water temperature (based on Mg/Ca ratios and oxygen isotopes) for the Cariaco Basin with a resolution of 1 to 1.5 years. However, because of sample size limitations, there are few proxy studies at these very fine resolutions.…”

Solar Arctic-Mediated Climate Variation on Multidecadal to Centennial Timescales: Empirical Evidence, Mechanistic Explanation, and Testable Consequences

“…The proposed Cause C mechanism must necessarily include coupling with the multidecadal-to centennial-scale variations of the Atlantic Intertropical Convergence Zone, as noted in several proxy archives Poore et al, 2004;Peterson and Haug, 2006;Black et al, 2007) and in climate modeling experiments (Vellinga and Wu, 2004;Chiang and Bitz, 2005;Zhang and Delworth, 2005). In general, these studies have highlighted a robust shift of the ITCZ southward during North Atlantic cooling and slower MOC/THC and a northward ITCZ shift during the opposite phase of stronger MOC/THC and warmer North AtlanticArctic conditions.…”

“…The theory of Nilsson, Walin and colleagues viewed the slow upwelling of dense water overall in the low latitudes and the Southern Ocean (see also Visbeck, 2007;Toggweiler and Russell, 2008), rather than high-latitude production and sinking of dense water as the rate-limiting branch of THC. 9 The Nilsson et al theory showed, with a reasonable model of interval wave mixing, that the vertical diffusivity would increase with decreasing surface equator-to-pole density contrast, and that would deepen the thermocline and, in turn, lead to a stronger THC.The proposed Cause C mechanism must necessarily include coupling with the multidecadal-to centennial-scale variations of the Atlantic Intertropical Convergence Zone, as noted in several proxy archives Poore et al, 2004;Peterson and Haug, 2006;Black et al, 2007) and in climate modeling experiments (Vellinga and Wu, 2004;Chiang and Bitz, 2005;Zhang and Delworth, 2005). In general, these studies have highlighted a robust shift of the ITCZ southward during North Atlantic cooling and slower MOC/THC and a northward ITCZ shift during the opposite phase of stronger MOC/THC and warmer North AtlanticArctic conditions.…”