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Abstract The delivery of nutrients from intermediate waters that form in the Southern Ocean is thought to be a key control on tropical ocean surface productivity. In this paper, we present geochemical evidence that an increase in low‐latitude productivity during the Last Interglacial (LIG) was driven by an increase in the preformed nutrient content of Subantarctic Mode Water (SAMW). We generated records of benthic foraminiferal δ¹³C, δ¹⁸O, Cd/Ca and Mg/Li which are used to reconstruct seawater cadmium, dissolved oxygen, and temperature from a core site in the Florida Straits. The Florida Straits is a location of mixing between SAMW and Northern Component Water, the ratio of which is dependent on the strength of the Atlantic Meridional Overturning Circulation. We find that Late LIG seawater cadmium—which in today's ocean is correlated to phosphate—was substantially higher than the Late Holocene (LH) average at this location, while apparent oxygen utilization was similar during these two periods. Thus, we invoke higher preformed phosphate in the Florida Straits during the Late LIG relative to the LH. Increased SAMW preformed phosphate could be the result of reduced Antarctic Zone winter mixed layer residence time and greater Southern Ocean surface nutrient supply during the Late LIG compared to the LH, as supported by published reconstructions of Southern Ocean biogeochemistry and dynamics. We therefore hypothesize that higher SAMW preformed phosphate would cause an increase in the transport of nutrients into the low latitudes, thereby increasing productivity there. 

Two collocal cores were recovered at approx. 542 meters depth in the Bahamas side of the Florida Straits. Benthic foraminifera species Planulina ariminensis and Hoeglundina elegans, as well as Globobulimina spp., were picked from the greater-than 250-micron size fraction. Mass spectrometry methods were used to analyze P. ariminensis and Globobulimina spp. tests for carbon and oxygen isotopic ratios while H. elegans tests were analyzed for the cadmium/calcium, magnesium/calcium, and lithium/calcium ratios. The records extend from the Late Holocene to the Penultimate Glacial Maximum (Marine Isotope Stage [MIS] 6), with high sedimentation rates during peak interglacial periods (MIS 1 and 5e). Elemental ratios were measured by reductively and oxidatively cleaning the samples following Boyle and Rosenthal (1996), and then using a Thermo Finnigan Element2 Magnetic Sector Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) at the Institute of Alpine and Arctic Research, University of Colorado, Boulder (INSTAAR) according to the methods of Marchitto (2006).Stable oxygen and carbon isotopic ratio data (δ18O and δ13C, respectively) for all samples of P. ariminensis and 51 out of 70 total samples of Globobulimina spp. were acquired using a Thermo MAT 253 with Kiel carbonate preparation device at the Georgia Institute of Technology (GT). 19 replicate samples of Globobulimina were analyzed at the University of Arizona with the same methods.The temperature reconstruction uses the Mg/Li-based calibration proposed by Marchitto et al. (2018)The oxygen content reconstruction uses the benthic foraminiferal epifaunal-infaunal δ13C gradient proxy, specifically the recently updated calibration described in Hoogakker et al. (2025). 

Abundant proxy records suggest a profound reorganization of the Atlantic Meridional Overturning Circulation (AMOC) during the Last Glacial Maximum (LGM, ~21,000 y ago), with the North Atlantic Deep Water (NADW) shoaling significantly relative to the present-day (PD) and forming Glacial North Atlantic Intermediate Water (GNAIW). However, almost all previous observational and modeling studies have focused on the zonal mean two-dimensional AMOC feature, while recent progress in the understanding of modern AMOC reveals a more complicated three-dimensional structure, with NADW penetrating from the subpolar North Atlantic to lower latitude through different pathways. Here, combining²³¹Pa/²³⁰Th reconstructions and model simulations, we uncover a significant change in the three-dimensional structure of the glacial AMOC. Specifically, the mid-latitude eastern pathway (EP), located east of the Mid-Atlantic Ridge and transporting about half of the PD NADW from the subpolar gyre to the subtropical gyre, experienced substantial intensification during the LGM. A greater portion of the GNAIW was transported in the eastern basin during the LGM compared to NADW at the PD, resulting in opposite²³¹Pa/²³⁰Th changes between eastern and western basins during the LGM. Furthermore, in contrast to the wind-steering mechanism of EP at PD, the intensified LGM EP was caused primarily by the rim current forced by the basin-scale open-ocean convection over the subpolar North Atlantic. Our results underscore the importance of accounting for three-dimensional oceanographic changes to achieve more accurate reconstructions of past AMOC. 

The high rate of biological productivity in the North Atlantic is stimulated by the advective supply of nutrients into the region via the Gulf Stream (nutrient stream). It has been proposed that the projected future decline in the Atlantic Meridional Overturning Circulation (AMOC) will cause a reduction in nutrient supply and resulting productivity. In this work, we examine how the nutrient stream changed over the Younger Dryas climate reversal that marked the transition out of the last ice age. Gulf Stream nutrient content decreased, and oxygen content increased at the Florida Straits during this time of weakened AMOC. The decreased nutrient stream was accompanied by a reduction in biological productivity at higher latitudes in the North Atlantic, which supports the link postulated in theoretical and modeling studies. 

Abstract The tropical Pacific climate has an outsized impact on global climate, yet future projections are poorly constrained. Data‐model comparisons from the mid‐Pliocene warm period (3.3 million years ago) can help investigate warm climate dynamics and evaluate model behavior. Here we compare proxy records to PlioMIP2 models and a model with modified cloud albedo. Relative to modern, the mid‐Pliocene warm period records show subsurface warming across the tropical Pacific, strong eastern Pacific surface warming and weak western Pacific surface warming. Using clustering analyses to group model behavior relative to the proxy data, we find the model cluster with the best fit with the proxy data has enhanced warming in mid‐latitude thermocline source water regions which connect to the equator through the ventilated thermocline. Our study shows tropical ocean heat content during the mid‐Pliocene warm period was higher than today and has broad implications for the ocean's ability to absorb anthropogenic heat. 

Abstract. We present a global atlas of downcore foraminiferal oxygen and carbon isotope ratios available at https://doi.org/10.1594/PANGAEA.936747(Mulitza et al., 2021a). The database contains 2106 published and previously unpublished stable isotope downcore records with 361 949 stable isotopevalues of various planktic and benthic species of Foraminifera from 1265 sediment cores. Age constraints are provided by 6153 uncalibratedradiocarbon ages from 598 (47 %) of the cores. Each stable isotope and radiocarbon series is provided in a separate netCDF file containingfundamental metadata as attributes. The data set can be managed and explored with the free software tool PaleoDataView. The atlas will provideimportant data for paleoceanographic analyses and compilations, site surveys, or for teaching marine stratigraphy. The database can be updated withnew records as they are generated, providing a live ongoing resource into the future. 

The atlas contains a collection of 2,106 published and previously unpublished downcore stable isotope records of various planktonic and benthic species of foraminifera from 1,265 globally distributed sediment cores. Uncalibrated radiocarbon dates are provided for 598 cores in the collection. Each stable isotope and radiocarbon series is stored in a separate netCDF file containing fundamental meta data as attributes. The data set can be further explored and analyzed with the free software tool PaleoDataView (Langner, M. and Mulitza, S.: Clim. Past, 15, 2067–2072, https://doi.org/10.5194/cp-15-2067-2019). WA_Foraminiferal_Isotopes_2022.zip contains 2006 stable isotope records (in netCDF format) and 598 radiocarbon records (in netCDF format). The folder structure in the file should be preserved and is required to use the collection with the software PaleoDataView.