Tracking the sea‐level signature of the 8.2 ka cooling event: New constraints from the Mississippi Delta

Abstract

[1] The ever increasing need for accurate predictions of global environmental change under greenhouse conditions has sparked immense interest in an abrupt, century-scale cooling around 8200 years ago, with a focal point in the North Atlantic and with hemispheric teleconnections. Despite considerable progress in the unraveling of this striking feature, including a conceivable driving mechanism (rapid drainage of proglacial Lake Agassiz/Ojibway and a resulting reduced strength of North Atlantic thermohaline circulation), several key questions remain unanswered. One salient aspect concerns the total amount of freshwater released during this catastrophic event, likely echoed by a near-instantaneous eustatic sea-level rise. So far, no attempts have been made to perform high-resolution sealevel studies that explicitly focus on this critical time interval. Here, we present new data from the Mississippi Delta suggestive of abrupt sea-level rise associated with the 8.2 ka event. However, the amount of sea-level rise was likely less than $1.2 m, corresponding to a meltwater volume of less than $4.3 10 14 m 3 ; values lower than estimates used by several recent studies.

The 8200yr BP cold event in stable isotope records from the North Atlantic region

“…An initial first drainage~8450 ± 44 yr BP, followed by refilling of Lake Agassiz over a~200 yr interval, has been suggested on the basis of evidence from highly resolved records of relative sea level change from peats in the Rhine-Meuse delta, near Rotterdam, The Netherlands (Hijma and Cohen, 2010). The relative sea level rise (2.11 ± 0.89 m) recorded in these sediments and associated with the drainage of Lake Agassiz was double the size of previous estimates (0.4-1.4 m) (Tornqvist et al, 2004;Kendall et al, 2008). A pulsed drainage and refilling, in line with the interval between two distinct episodes of surface water freshening in the North Atlantic southwest of Iceland (Ellison et al, 2006) was considered the most likely explanation (Hijma and Cohen, 2010).…”

The sea-level fingerprint of the 8.2 ka climate event

“…Törnqvist et al (2004a) recently obtained a sea-level record associated with the 8.2 ka event from two cores within the Mississippi Delta. Both cores contained basal salt marsh peat that accumulated immediately on the consolidated Pleistocene basement.…”

Influence of inherited topography on the Holocene sedimentary evolution of coastal systems: An example from Arno coastal plain (Tuscany, Italy)

“…Unlike other coastal settings, such as the Mississippi delta and the Rhine-Meuse delta (Törnqvist et al, 2004;Hijma and Cohen, 2010), Table 2). Radiocarbon age from Benvenuti et al (2006) projected on the section line B-B′ and the interpolated age of core S1 from Amorosi et al (2009) are shown with an asterisk.…”