Reconstructing Western Boundary Current Stability in the North Atlantic Ocean for the Past 700 Kyr From Globorotalia truncatulinoides Coiling Ratios. Issue 12 (21st December 2020)

• Record Type: Journal Article
• Authors: Billups, Katharina; Vizcaíno, Maoli; Chiarello, Josephine; Kaiser, Emily A.
• Is Part Of: Paleoceanography and paleoclimatology. Volume 35:Issue 12(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-12-21
• Subjects: Pleistocene -- Globorotalia truncatulinoides -- subtropical gyre -- water column structure -- North Atlantic Ocean; Paleoceanography -- Periodicals; Paleoclimatology -- Periodicals; 551.46
• DOI: 10.1029/2020PA003958
• Languages: English
• ISSNs: 2572-4517

Abstract

Abstract: Down‐core changes in the coiling direction of Globorotalia truncatulinoides in the northwestern subtropical Atlantic (KNR140‐37PC and Ocean Drilling Program Sites 1063, 1059, 1056, 1058) provide a tracer for the hydrographic conditions in the western boundary current over the past 700 kyr (Marine Isotope Stage, MIS, 1–17). A consistent association between percent G. truncatulinoides (sinistral) abundances, total test counts, and bulk sediment CaCO3 content is established by MIS 11 suggesting a response to ocean‐atmosphere interactions during the mid Brunhes event. Commencing with MIS 11, interglacial maxima are associated with high total test counts and either distinct sinistral test minima (MIS 9e, 11c) or maxima (MIS 1, 5e, 7a). High sinistral test abundances with relatively high test counts is similar to the late Holocene relationship at the study sites. Low sinistral test abundances despite high test counts means that coiling ratios are dominated by dextral forms. We interpret this pattern to indicate more intense flow in the subtropical gyre either via the western boundary current drawing toward the gyre center, or a more northern influence of the North Equatorial and Antilles Currents. This suggests that the western boundary current may have been more intense during MIS 11c and MIS 9e then during MIS 7a, MIS 5e, and MIS 1 consistent with climate warm anomalies in northern Europe at these times. Regardless of the mechanism, the observation that minima and maxima in sinistral test abundances are prolonged at these times indicates that the western gyre boundary remained stable during relative warm intervals. Key Points: Consistent coupling between G. truncatulinoides coiling ratios, total test counts, and bulk sediment CaCO3 content begins with MIS 11 Sinistral maxima during MIS 7a, 5c–5e, 1, and minima during MIS 11c, 9c–9e, occur with high test counts reflecting intensified circulation Sinistral maxima (MIS 5c–5e, 1) and minima (MIS 11c, 9c–9e) are prolonged indicating stability of the boundary current during warm intervals