This study explores the ecology of the benthic foraminifera fauna and reconstructs bottom water oxygenation, organic matter fluxes, and Mediterranean Outflow Water (MOW) dynamics in the Gulf of Cadiz during the Early to Middle Pleistocene Transition (EMPT) interval of Marine Isotope Stage (MIS) 28 to MIS 19 (1014-761 ka) using high-resolution multiproxy data from IODP Site U1387. Along with benthic foraminifera assemblages, we integrate stable isotopes (delta 18O and delta 13C), organic carbon, alkenone concentrations, and geochemical and sedimentological proxies (Zr/Al ratio, grain size) to identify environmental drivers across glacial-interglacial cycles and millennial-scale events. Furthermore, the absolute abundance of Planulina ariminensis is applied as a proxy for bottom current strength. Principal component analysis confirms assemblage responses to variations in organic matter quality and oxygenation. Periods of intensified MOW during stadial climate stages correspond to enhanced bottom water ventilation, reflected in higher abundances of epifaunal and porcelaneous taxa, higher diversity, and increased dissolved oxygen, with the exception of the late MIS 22. Intervals of reduced ventilation (e.g. interglacial MIS 27, MIS 25e, MIS 21g, MIS 19c) coincide with higher total alkenone concentrations, potentially contributing to low oxygen conditions and increased proportions of infaunal taxa. Our results reveal that bottom water dynamics at Site U1387 were controlled by local oceanographic processes (e.g. coastal upwelling, river discharge, water column stratification) rather than by global ice volume changes only. These findings highlight the importance of understanding regional oceanographic variations during the EMPT and emphasize the value of combining food supply, oxygenation, and bottom current proxies to interpret benthic foraminifera ecological changes.

The Mediterranean Outflow Water (MOW), modified by paleoceanographic conditions and tectonic processes, played a significant role in the formation of sediments drifts along the Iberian Margin. Using sediment samples from IODP Hole U1387C, we explore the Early Pleistocene history of the upper MOW core above the central Faro Drift in the Gulf of Cadiz. The time series of benthic foraminifer stable isotope and grain size related data have a rigorous stratigraphic framework consisting of nannofossil biostratigraphy and paleomagnetic and delta 18O stratigraphy. The paleoenvironmental records are supplemented by natural gamma ray downhole logging data. Above the hiatus associated with the youngest dolostone, sandy to muddy contourite sedimentation started at 1.946 Ma, i.e., within Marine Isotope Stage (MIS) 74, at IODP Site U1387, slightly younger than at IODP Site U1389. Formation of contourite layers, reflected in the sortable silt and sand percentage records, strongly reacted to precession forcing, including semi- and quarter-precession cycles. The majority of the contourite beds developed during stadial (colder) climate periods, like previous observations from the Early to Late Pleistocene. Formation of contourite layers within MIS 53, MIS 55 and MIS 65, however, appear to be linked to the prevailing atmospheric conditions over North Africa. Periods of poor ventilation in the upper MOW were linked to insolation maxima and reduced ventilation in the Mediterranean Sea. Here, MIS 51 presents a peculiar case as poor ventilation reached from the surface to the lower North Atlantic Deep Water range, reflecting unique interglacial conditions that merit future exploration.

In the South Pacific Convergence Zone (SPCZ), interannual to interdecadal oceanic and atmospheric variability is especially pronounced. The El Niño Southern Oscillation and the Interdecadal Pacific Oscillation significantly influence the SPCZ diagonal axis and salinity front. Regional coral‐based paleo‐environmental reconstructions extend the relatively short and discontinuous instrumental sea surface temperature (SST) and sea surface salinity (SSS) record to elucidate past variability. We present monthly resolved, composite indices of coral skeletal δ 18 O, Sr/Ca, and calculated δ 18 O sw utilizing coral geochemical time‐series from Rotuma, Fiji, Tonga, and Rarotonga, dubbed the SPCZ coral (SPCZ c ) indices. The new indices build upon previous efforts to describe variability and trends in the SPCZ region with expanded coverage due to a new northwestern coral addition from the SPCZ fresh pool. The increased spatial and temporal resolution of the new indices allows for higher‐fidelity sub‐annual reconstructions of SST and SSS in the region dating back to 1848. The results confirm the secular warming trend of 1°C in the SPCZ region and show a 0.4 S p freshening starting in the 1880s. The SPCZ c δ 18 O sw is the first regional reconstruction of δ 18 O sw and provides valuable insights into past SSS variability, including elucidating responses to El Niño and La Niña events, as well as identifying past SPCZ zonal events. The SPCZ c δ 18 O sw reconstruction extends the instrumental records by ∼100 years. The SPCZ c indices prove the utility of the compositing approach in describing regional oceanographic variability with the increased signal‐to‐noise ratio of the obtained coral climatic data.

Fram Strait, between NE Greenland and Svalbard, is the main passage for freshwater export from the Arctic Ocean (AO). Here we report results from the first high-resolution multiproxy study of a sediment record from 81 degrees N in this Arctic Gateway to reconstruct the freshwater and environmental variability since similar to 200 ka. Based on highly resolved stable isotope records from benthic and planktic foraminifers we link prominent isotopic events in marine isotope stages (MIS) 6-3 to times of strong freshwater input to the AO from the disintegration of circum-Arctic ice sheets and from the discharge of previously ice-dammed lakes in northern Eurasia. Additional short-term events point at the injection of low-salinity waters at intermediate depth along the NE Greenland continental margin, possibly caused by the release of sediment-laden, freshwater-enriched hyperpycnal flows on the shelf and upper continental margin. Changes in the deposition of foraminifers and coarse ice-rafted terrestrial debris at site PS93/016 document highly variable conditions in the NW Fram Strait with sedimentation from icebergs during times of large-scale glaciation around the Arctic and with other intervals dominated by sea ice. Foraminifer-rich sediments even suggest the development of seasonally open waters (polynyas) during certain periods. Four time intervals with a particularly strong and long-lasting freshwater export from the Arctic Ocean can be traced to the western Nordic Seas where modern deepwater formation occurs. The good temporal correlation of these intervals with weakenings of the deepwater circulation in the North Atlantic makes a strong case for a decisive role of Arctic freshwater export in the history of the global climate system of the last 200 ka, in particular as a trigger for instabilities of the Atlantic meridional overturning circulation.

Magma emplacement in the top unconsolidated sediments of rift basins is poorly understood. We compare two shallow sills from the Guaymas Basin (Gulf of California) using core data and analyses from IODP Expedition 385, and high‐resolution 2D seismic data. We show that magma stalling in the top uncemented sediment layer is controlled by the transition from siliceous claystone to uncemented silica‐rich sediment, favoring flat sill formation. Space is created through a combination of viscous indentation, magma‐sediment mingling and fluidization processes. We show that sills emplace above the opal‐A/CT diagenetic barrier. Our model suggests that in low magma input regions sills emplace at constant depth from the seafloor, while high magma input leads to upward stacking of sills, culminating in a funnel‐shaped intrusions. Our petrophysical, petrographic, and textural analyses show that magma‐sediment mingling creates significant porosity (up to 20%) through thermal cracking of the assimilated sediment. Stable isotope data suggest carbonate formation at 70–90°C, consistent with background geothermal gradient at 250–325 m depth. The unconsolidated, water‐rich host sediments produce little thermogenic gas through contact metamorphism, but deep diagenetically formed gas bypasses the low‐permeability top sediments via hydrothermal fluids flowing through the magma plumbing system. This hydrothermal system provides a steady supply of hydrocarbons at temperatures amendable for microbial life, serving as an incubator that may be abundant in magma‐rich young rift basins and play a key role in sustaining subseafloor ecosystems.

Deep-sea sediment cores from the Arctic Ocean are excellent archives suitable for the reconstruction of deglacial events on circum-Arctic continents and the associated enhanced export of freshwater to the North Atlantic. Here we present new records from a long large-volume sediment core obtained on the NE Greenland continental margin at 81.2°N where the shelf is particularly narrow. The site is perfectly located to monitor the export of freshwater and ice from the Arctic Ocean to the Greenland Sea using data on ice-rafted debris (IRD) and the stable isotope composition of planktic and benthic foraminifers in the sediments. The records from our new core hold evidence of a number of strong freshwater export events in the last 200 ka. Several events correlate in time with extreme discharges from large lakes which had developed south of the ice sheets on northern Eurasian shelves in MIS 6, 5b and 4. Using published data from the Greenland Sea and the North Atlantic, we can show that freshening events in the Arctic and the Nordic Seas correlate with weakenings of the Atlantic meridional overturning circulation (AMOC). We propose that enhanced Arctic Ocean freshwater export triggered (or contributed to) decreased deepwater renewal in the Greenland Sea and had severe consequences for the strength of the global ocean circulation. In addition to the Arctic Ocean freshwater events our new records reveal a number of probably minor events of iceberg melting and intermediate water freshening which we associate with the history of continental ice on North Greenland and in particular in the Wandel Sea. We propose that the repeated ice expansion and retreat in this area released dense plumes of fine-grained sediment and low d18O-water which spread along the continental slope. This may have happened in MIS 6, 5d, and 4. For the last 50 ka, our records suggest an ice retreat on North Greenland at 50-40 ka and a stepwise readvance of the ice front at 35-25 ka.

Besides the shift in dominant orbital cyclicity depicted in paleoclimate proxy records, the Mid-Pleistocene Transition or Early–Middle Pleistocene Transition (EMPT) was linked to a change in the deep thermohaline circulation. Those changes contributed to more intense and longer-lasting glacial periods and cooler sea surface temperatures (SSTs) during glacials. Within the Atlantic Ocean, the Iberian Margin is considered a key location to study climatic variations influenced by both high- and low-latitude processes. In this study we focus on IODP Site U1387 on the southern Portuguese margin to reconstruct surface water circulation changes and related plankton foraminifera ecosystems during the interval of Marine Isotope Stage (MIS) 28 to MIS 18 (1006–750 ka). Our planktonic foraminifera assemblages and SST reconstructions (foraminifera assemblages and U37K′ alkenone index) demonstrate warm, relative stable SST conditions during much of the interval due to persistent influence of subtropical gyre waters as indicated by the tropical–subtropical and Azores Current-related foraminifera species and the periods with dominant sinistral coiling direction of the species Globorotalia truncatulinoides. Maximum interglacial SSTs were up to 2 °C warmer than at present in both summer and winter, with the exception of interglacial MIS 23 with SSTs ∼ 1.5 °C colder than in the other interglacials. Subsequent to the respective glacial inception, the relatively warm conditions were periodically interrupted by millennial-scale extreme cold events when polar species Neogloboquadrina pachyderma became abundant (> 30 %), and the SSTs, reconstructed from the foraminifera assemblage data, dropped below 10 °C in summer and 5 °C in winter, although some of those values might be overestimated. The most pronounced event, considering the amplitude of cooling and duration, occurred between 870 and 864 ka, marking the terminal stadial event of the MIS 22–MIS 21 transition (Termination X). Extreme cold events, always associated with the incursion of subpolar waters into the Gulf of Cadiz, mark all the terminal stadial events from Terminations XII to IX and the millennial-scale variability during the transitions to full glacial conditions, although the duration of the cooling varied greatly. The extreme cooling was only possible through migration of the subarctic front into the lower mid-latitudes as a consequence of cooling and freshening in the higher latitudes and the associated extreme reduction in the Atlantic Meridional Overturning Circulation. The amplitude of cooling, duration, and frequency of subpolar water incursions during MIS 24 to MIS 22 stands out, providing further evidence for the “900 ka event” being a key feature of the EMPT.

The Southwest Pacific region is of great importance to global climate variability, but instrumental climate observations before the 1980s lack in numbers and quality. Despite efforts in complementing instrumental records with proxy sea surface temperature (SST) and sea surface salinity (SSS) reconstructions based on coral Sr/Ca and delta 18Osw records, few of them are longer than a century. This study introduces a northwestern extension to the existing records of South Pacific coral study sites with monthly-resolved Sr/Ca, delta 18O, and delta 18Osw reconstructions from Rotuma dating back to 1821. Additionally, we present new monthly-resolved Sr/Ca and reconstructed delta 18Osw from a coral from Tonga dating back to 1848. Results reveal 1.5 degrees C warming in the Western Pacific Warm Pool, while the adjacent coral from Tonga shows 1 degrees C warming over the twentieth century. The Rotuma Sr/Ca record reveals thermal stress events impacting the Sr/Ca-SST relationship in the following months. Coral delta 18Osw results reveal significant freshening of 0.45 Sp (practical salinity unit) in Tonga since the early twentieth century, suggesting the southeastward expansion of the South Pacific Convergence Zone salinity front. The delta 18Osw inferred SSS provides a valuable extension into the past considering the short and inconsistent instrumental records available. This study demonstrates the utility of coral-based reconstructions in capturing long-term and regional climate variations in the Southwest Pacific and the necessity of expanding replicated studies to other underrepresented areas to enhance our understanding of regional climate dynamics.

Abstract. Besides the shift in dominant orbital cyclicity, the mid-Pleistocene Transition or Early-Middle Pleistocene Transition (EMPT) was characterized by a change in the deep thermohaline circulation. Those changes contributed to more intense and longer-lasting glacial periods and cooler sea surface temperatures (SSTs). Within the Atlantic Ocean, the Iberian margin is considered a key location to study climatic variations influenced by both high- and low-latitude processes. In this study we focus on IODP Site U1387 on the southern Portuguese margin to reconstruct surface water circulation and related plankton foraminifera ecosystem changes during the interval of Marine Isotope Stage (MIS) 28 to MIS 18 (1006–750 ka). Our planktonic foraminifera assemblages and SST reconstructions (foraminifera assemblages and UK'37 alkenone index) demonstrate warm, stable SST conditions during much of the interval due to persistent influence of subtropical gyre waters as indicated by the tropical-subtropical and Azores Current related foraminifera species and the periods with dominant sinistral coiling direction of the species Globorotalia truncatulinoides. Maximum interglacial SSTs were up to 2 °C warmer than at present in both summer and winter, with the exception of interglacial MIS 23 with SSTs ~1.5 °C colder than in the other interglacials. Subsequent the respective glacial inception, the relative warm conditions were periodically interrupted by millennial-scale extreme cold events when polar species Neogloboquadrina pachyderma became abundant (>30 %) and the SSTs, reconstructed from the foraminifera assemblage data, dropped below 10 °C in summer and 5 °C in winter. The most pronounced event, considering the amplitude of cooling and duration, occurred between 870 to 864 ka, marking the terminal stadial event of the MIS 22/MIS 21 transition (Termination X). Extreme cold events, always associated with the incursion of subpolar waters into the Gulf of Cadiz, mark all the terminal stadial events from Terminations XII to IX and the millennial-scale variability during the transitions to full glacial conditions, although the duration of the cooling varied greatly. The extreme cooling was only possible through migration of the subarctic front into the lower mid-latitudes as a consequence of an extreme reduction in the Atlantic meridional overturning circulation. The amplitude of cooling, duration, and frequency of subpolar water incursions during MIS 24 to MIS 22 stands out, providing further evidence for the "900 ka event" being a key feature of the EMPT.

High-resolution and long-term paleorecords from the central Indo-Pacific Warm Pool (IPWP) will help us understand tropical climates. Here, we present a high-resolution record (alkenone SST, alkenone mass accumulation rate and opal content %) of piston core MD01-2380 retrieved from the Banda Sea, eastern Indonesia, to track changes in sea surface temperature, paleo-productivity, and upwelling activities in the Banda Sea. Combined with published paleo-time series from the same region, we have reconstructed the zonal (east-west) and meridional (equator to mid-latitudes) gradients in sea surface temperature of the warm pool over the past eight glacial cycles. These gradients control zonal and meridional atmospheric circulations and reflect the dynamics of expansion and contraction of the warm pool. The pronounced zonal gradients in sea surface temperature show different patterns before and after the Middle Brunhes Event (MBE), as well as enhanced upwelling in the Banda Sea after the MBE. We suggest that shoaling of the western equatorial Pacific thermocline has induced more CO2 release into the atmosphere from the deep sea.

The possibility of a collapse (or marked weakening) of the Atlantic Meridional Overturning Circulation (AMOC) within a few centuries boosted the interest of the scientific community on the responses of different compartments of the climate system to past AMOC collapses (or marked weakening). The most recent examples of such periods are Heinrich Stadial 1 (HS1,18-15 ka BP; near-collapsed AMOC) and the Younger Dryas (YD, 12.9-11.7 ka BP; markedly weakened AMOC). Here, we present data from elemental ratios, spectral reflectance, organic biomarkers, sea surface temperatures and planktonic foraminiferal assemblage from two marine sediment cores recovered from the western tropical South Atlantic Ocean spanning the last ca. 20 kyr. The recovered sediments record the responses of eastern tropical South American hydroclimate, western tropical South Atlantic productivity and sea surface temperatures to changes in AMOC strength associated with HS1 and the YD. Our data show that both periods were characterized by wetter conditions over eastern tropical South America associated with increased continental runoff compared to the Last Glacial Maximum. High sea surface temperatures during HS1 and the YD are in line with marked AMOC decreases that led to heat accumulation in the surface layer of the western South Atlantic Ocean, facilitating increased precipitation over eastern tropical South America. Our data demonstrate for the first time that intense runoff during HS1, and hence nutrient transfer to the ocean, affected the pelagic ecosystem, likely increasing primary productivity in the otherwise oligotrophic western tropical South Atlantic Ocean. Our study demonstrates a tight coupling between marine and terrestrial processes in the eastern South American realm during periods of strong climate instability.

Carbonate shells and encrustations from lacustrine organisms provide proxy records of past environmental and climatic changes. The oxygen isotopic composition (δ18O) of such carbonates depends on water temperature during carbonate precipitation, and on the δ18O of the lake water. Lake water δ18O, in turn, is controlled by the δ18O of precipitation in the catchment, water residence time and mixing, and by evaporation. A paleoclimate interpretation of carbonate δ18O records requires a site-specific calibration based on an understanding of the local conditions. For this study, carbonates and water were sampled in the littoral zone of lake Locknesjön, central Sweden (62.99°N, 14.85°E, 328 m a.s.l.) along a water depth gradient from 1 to 8 m. We took samples from living organisms and sub-recent samples in surface sediments of the calcifying algae Chara hispida, the mollusk Pisidium, and adult and juvenile instars of two ostracod species, Candona candida and Candona neglecta. We show that neither the δ18O of carbonates nor the δ18O of water vary significantly with water depth, indicating a well-mixed epilimnion. The largest differences in the mean carbonate δ18O between species are caused by vital offsets, i.e. the species-specific deviation from the δ18O of inorganic carbonate which would have been precipitated in isotopic equilibrium with the water. After subtraction of these constant vital offsets, remaining differences in the mean carbonate δ18O between species can mainly be attributed to seasonal water temperature changes. The lowest δ18O values are observed in Chara encrustations, which form during the summer months when photosynthesis is most intense. Adult ostracods, which calcify their valves during the cold season, display the highest δ18O values. This is because an increase in temperature leads to a decrease in fractionation between carbonate and water, and therefore to a decrease in carbonate δ18O. An increase in temperature also leads to an increase in the δ18O of lake water through its effect on precipitation δ18O and on evaporation, and consequently to an increase in carbonate δ18O, opposite to the temperature effect on fractionation. However, the seasonal and inter-annual variability in lake water δ18O is small (0.5‰) due to the long water residence time. Seasonal changes in the temperature-dependent fractionation are therefore the dominant cause of carbonate δ18O differences between species. Temperature reconstructions based on “paleo-temperature” equations for equilibrium carbonate precipitation using the mean δ18O of each species and the mean δ18O of lake water are well in agreement with the observed seasonal water temperature range. The high carbonate δ18O variability of samples within a species, on the other hand, leads to a large scatter in the reconstructed temperatures based on individual samples. This implies that care must be taken to obtain a representative sample size for paleo-temperature reconstructions.

A new matrix‐matched reference material has been developed – NFHS‐2‐NP (NIOZ Foraminifera House Standard‐2‐Nano‐Pellet) – with element mass fractions, and isotope ratios resembling that of natural foraminiferal calcium carbonate. A 180–355 µm size fraction of planktic foraminifera was milled to nano‐particles and pressed to pellets. We report reference and information values for mass fractions of forty‐six elements measured by six laboratories as well as for 87Sr/86Sr (three laboratories), δ13C, δ18O (five laboratories) and 206,207,208Pb/204Pb isotope ratios (one laboratory) determined by ICP‐MS, ICP‐OES, MC‐ICP‐MS, isotope ratio mass spectrometry, WD‐XRF and TIMS. Inter‐ and intra‐pellet elemental homogeneity was tested using multiple LA‐ICP‐MS analyses in two laboratories applying spot sizes of 60 and 70 µm. The LA‐ICP‐MS results for most of the elements relevant as proxies for palaeoclimate research show RSD values < 3%, demonstrating a satisfactory homogeneous composition. Homogeneity of 87Sr/86Sr ratios of the pellet was verified by repeated LA‐MC‐ICP‐MS by two laboratories. Information values are reported for Pb isotope ratios and δ13C, δ18O values. The homogeneity for these isotope systems remains to be tested by LA‐MC‐ICP‐MS and secondary‐ion mass spectrometry. Overall, our results confirm the suitability of NFHS‐2‐NP for calibration or monitoring the quality of in situ geochemical techniques.

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 isotope values of various planktic and benthic species of Foraminifera from 1265 sediment cores. Age constraints are provided by 6153 uncalibrated radiocarbon ages from 598 (47 %) of the cores. Each stable isotope and radiocarbon series is provided in a separate netCDF file containing fundamental metadata as attributes. The data set can be managed and explored with the free software tool PaleoDataView. The atlas will provide important data for paleoceanographic analyses and compilations, site surveys, or for teaching marine stratigraphy. The database can be updated with new records as they are generated, providing a live ongoing resource into the future.

The early Pliocene, with atmospheric CO2 concentrations at levels similar to today, is seen as a case study for Earth’s future climate evolution. During this period the progressive closing of the Central American Seaway led to increased poleward heat and salt transport within the Atlantic with North Atlantic Deep Water (NADW) becoming warmer and saltier and resulting in an enhanced Atlantic Meridional Overturning Circulation (AMOC). To evaluate the stability of the Pliocene AMOC, we are producing centennial-scale surface and deep-water records for IODP Site U1313 (41°N, 33°W, 3412m) for the interval from 3.3 to 4.4 Ma. This site is ideally located to monitor past AMOC changes with North Atlantic Drift waters at the surface and NADW, exported by the deep western boundary current, in the deep. Surface water variations are reconstructed based on the stable isotope data of the planktonic foraminifer genus Globigerinoides sp. and on Mg/Ca derived temperatures during the late Pliocene, whereas deep-water changes are revealed by the stable isotope records of the benthic foraminifer genus Cibicidoides. Besides the interglacial/glacial cycles, higher frequency oscillations are recorded in the foraminiferal records. Varying surface water conditions, especially during Late Pliocene interglacial periods, are observed and we will use the pending Mg/Ca temperature data to assess if they are linked to salinity changes. The high-frequency oscillations are related to precession forcing, especially its harmonics in the 5.5 kyr and 11 kyr ranges. The benthic δ13C values indicate nearly continuous NADW presence and confirm a strong AMOC throughout the studied interval, also during most of the glacial periods. During the early Pliocene, glacial stage Gi 6 had a stronger impact on the AMOC than Gi 2 and Gi 4. Overall, the AMOC was strong throughout, but experienced high frequency oscillations at a level similar to the middle Pleistocene interglacial periods.

In order to understand interglacial climate variability we also need to study interglacial periods prior to the Mid-Pleistocene Transition, i.e. within the 41 kyr world. Early Pleistocene interglacial periods, in particular from the interval directly preceding the onset of the Mid-Pleistocene Transition, provide ideal study cases since interglacial atmospheric carbon dioxide levels during that period appear to have been similar to or only slightly higher than during the warmest interglacials of the last 800 ka. Here we present the first results from a high-resolution, multi-proxy study of interglacial Marine Isotope Stage (MIS) 47 (1424-1452 ka) at IODP Site U1387 (36°48´N 7°43´W), drilled into the Faro Drift on the southern Portuguese margin at 559 m water depth. Nowadays, surface waters near Site U1387 originate from the subtropical gyre, whereas the intermediate-depth Mediterranean Outflow Water (MOW) is encountered at the seafloor. For our study, we use the stable isotope data of planktonic foraminifera species G. bulloides and G. ruber white and benthic foraminifera species P. ariminensis and C. pachyderma, biomarker-derived sea-surface temperatures (SST), the weight percentage of the sand fraction, and microfossil evidence. Following a rapid transition, interglacial conditions were quickly established in the surface waters with SST at levels near or above 24°C, sometimes even exceeding 25°C, throughout much of MIS 47. Those are the warmest SST so far observed for the Pleistocene at that location, being more than three degrees warmer than modern SST. The common occurrence of tropical species in the planktonic foraminifera fauna hints to a persistent contribution of tropical waters to the surface waters and thus probably the northward expansion and/or intensification of the North Atlantic's subtropical gyre. The MOW, on the other hand, experienced an extended period of poor ventilation, most likely associated with low oxygen levels, as indicated by the extremely low benthic carbon isotope values and the occurrence of gypsum crystals in the sediments that formed when the pyrite in the sediments was oxidized after the cores were opened. Following evidence from younger interglacials, this MOW signal should be linked to reduced ventilation and overturning in the Mediterranean Sea as consequence of increased freshwater input caused by an intensified North African monsoon. The benthic δ18O record of MIS 47 indicates a three phased interglacial period with a minimum separating two maxima. On a subtle level, this phasing might also exist in the surface water records. This and potential causes need to be explored further in the future, when all high-resolution data is available. Overall, the Site U1387 records confirm MIS 47 as a "super"-interglacial, much more so than MIS 31, on the southern Portuguese margin. Insights from this warm interglacial and associated oceanographic conditions and changes in the planktonic and benthic microfossil floras and faunas might provide hints on how future warming in those waters could impact the regional ecosystems.

The western South Atlantic along the Brazilian margin is an important region for the Atlantic Meridional Overturning Circulation (AMOC) because surface currents in this area transfer warm and salty waters from the Southern Hemisphere to the North Atlantic. Although the number of sea surface temperature (SST) reconstructions has grown in this region, it has been challenging to explain changes in different and sometimes proximal cores. To understand the SST evolution of the Brazilian margin from the Last Glacial Maximum (LGM) to the late Holocene, we present the first SST stack (BRSST stack) for this region. We compare the BRSST stack with the outputs of the transient climate model simulation TraCE-21ka. The BRSST stack shows an LGM cooling of 1.43 degrees C (from-1.31 to-1.55 degrees C, 2s) relative to the late Holocene, followed by deglacial warming starting at similar to 18.8 ka. TraCE-21ka simulates this early onset of the last deglaciation. Sensitivity experiments suggest that the input of meltwater from retreating ice sheets in the Northern Hemisphere triggered the post-LGM warming, which was subsequently sustained by increasing atmospheric CO2. Deglacial millennial-scale events of AMOC slowdown produced large-scale warming of the Brazilian margin not clearly distinguished by some previous studies. Analyzing our stack in its segregated components, i.e., the North Brazil Current (NBCSST stack) and Brazil Current (BCSST stack) e we noted in-phase warming at the onset of the last deglaciation, which is not found in TraCE-21ka simulations. We attributed this to underestimating the meltwater influence over the tropical Brazilian margin by the model. BRSST stack also presents episodes of abrupt cooling near periods of fast sea-level rise during the last deglaciation, which may be due to rapid AMOC reinvigoration or freshening of the Southern Ocean. Holocene climate resembles that recorded by other compilations, with no clear Holocene thermal maximum but presenting a cooling trend during the late Holocene possibly related to intensified volcanic activity. Our study indicates that the future human-induced SST change expected for the end of the 21st-century will overcome the background of natural climate variability of the last 22,000 years for the Brazilian margin. (C) 2022 Elsevier Ltd. All rights reserved.

In order to better understand interglacial climate variability within the 41 kyr world, we produced high-resolution climate records for interglacial Marine Isotope Stage (MIS) 47 (1424–1452 ka) at IODP Site U1387 (36°48′ N, 7°43′ W) on the southern Portuguese margin. Using benthic and planktonic foraminifera stable isotope records, Uk’37 sea-surface temperature (SST), and plankton assemblage data we investigated Mediterranean Outflow Water (MOW) and surface water conditions. The MOW-level records indicate a poorly ventilated and sluggish bottom current during the MIS 48/MIS 47 transition in association with the insolation maximum, whereas a well-ventilated MOW formed a contourite layer during the second insolation maximum. The benthic δ18O record shows a fairly abrupt change during the deglaciation of MIS 48, while the surface waters experienced a terminal stadial event that was associated with initial cooling and freshening followed by stepwise warming until interglacial SST was reached at 1450 ka. Interglacial conditions with SST of 24 °C or higher persisted until 1427 ka, although warm SST prevailed into MIS 46. The persistent and prolonged warmth is attributed to a northward expansion of the subtropical gyre during MIS 47 as reflected by the dominance of subtropical-tropical planktonic foraminifera species and the presence of warm water coccolithophores taxa.

In order to understand interglacial climate variability we also need to study interglacial periods prior to the Mid-Pleistocene Transition, i.e. within the 41 kyr world. Early Pleistocene interglacial periods, in particular from the interval directly preceding the onset of the Mid-Pleistocene Transition, provide ideal study cases since interglacial atmospheric carbon dioxide levels during that period appear to have been similar to or only slightly higher than during the warmest interglacials of the last 800 ka. Here we present the first results from a high-resolution, multi-proxy study of interglacial Marine Isotope Stage (MIS) 47 (1424-1452 ka) at IODP Site U1387 (36°48´N 7°43´W), drilled into the Faro Drift on the southern Portuguese margin at 559 m water depth. Nowadays, surface waters near Site U1387 originate from the subtropical gyre, whereas the intermediate-depth Mediterranean Outflow Water (MOW) is encountered at the seafloor. For our study, we use the stable isotope data of planktonic foraminifera species G. bulloides and G. ruber white and benthic foraminifera species P. ariminensis and C. pachyderma, biomarker-derived sea-surface temperatures (SST), the weight percentage of the sand fraction, and microfossil evidence. Following a rapid transition, interglacial conditions were quickly established in the surface waters with SST at levels near or above 24°C, sometimes even exceeding 25°C, throughout much of MIS 47. Those are the warmest SST so far observed for the Pleistocene at that location, being more than three degrees warmer than modern SST. The common occurrence of tropical species in the planktonic foraminifera fauna hints to a persistent contribution of tropical waters to the surface waters and thus probably the northward expansion and/or intensification of the North Atlantic's subtropical gyre. The MOW, on the other hand, experienced an extended period of poor ventilation, most likely associated with low oxygen levels, as indicated by the extremely low benthic carbon isotope values and the occurrence of gypsum crystals in the sediments that formed when the pyrite in the sediments was oxidized after the cores were opened. Following evidence from younger interglacials, this MOW signal should be linked to reduced ventilation and overturning in the Mediterranean Sea as consequence of increased freshwater input caused by an intensified North African monsoon. The benthic δ18O record of MIS 47 indicates a three phased interglacial period with a minimum separating two maxima. On a subtle level, this phasing might also exist in the surface water records. This and potential causes need to be explored further in the future, when all high-resolution data is available. Overall, the Site U1387 records confirm MIS 47 as a "super"-interglacial, much more so than MIS 31, on the southern Portuguese margin. Insights from this warm interglacial and associated oceanographic conditions and changes in the planktonic and benthic microfossil floras and faunas might provide hints on how future warming in those waters could impact the regional ecosystems.