North Atlantic Upper Ocean Hydrography During Pleistocene Interglacials Using <i>Globorotalia truncatulinoides</i> Coiling Ratios

Abstract We use Globorotalia truncatulinoides coiling ratios (expressed as a percentage of the proportion of sinistral tests with respect to total G . truncatulinoides ) as a proxy for North Atlantic poleward warm water advection during Marine Isotope Stages (MIS), 1, 5, 7, 9, and 11. The south to north transect is comprised of sites spanning previously published Gulf Stream sites (Billups et al., 2020, https://doi.org/10.1029/2020pa003958 ), the northern gyre boundary (IODP Site U1313), the North Atlantic Current (IODP Site U1308) and the subpolar Atlantic (ODP Site 980 and IODP Site U1314). We augment these results with previously published Gulf Stream sites (Billups et al., 2020, https://doi.org/10.1029/2020pa003958 ). Percent G. truncatulinoides (sinistral) in the core tops decrease toward the north in line with the subtropical species preferred habitat. Pronounced maxima (&gt;50% sinistral tests) occur at all sites during MIS 1, 5c–e, 7d, 11a, and 11e, indicating enhanced poleward flow that is not distinctly related to insolation. Percent G. truncatulinoides (sinistral) maxima that occurred during MIS 1, MIS 5e and MIS 11e lag the respective glacial terminations suggesting that warm water advection was not part of the initial driver of high‐latitude warmth. A comparison between the subtropical gyre boundary record (U1313), which spans the past 440 kyr continuously, with the Gulf Stream sites show concurrent sinistral maxima during glacial intervals occur during times of minor precession maxima and CO 2 peaks. This observation suggests the gyre was sensitive to smaller‐scale climate forcing factors despite the overall effects of a large northern hemisphere ice sheet on atmospheric and oceanic circulation.