Planktonic Foraminifera are widely used for environmental reconstructions through measurements of their shell's geochemical characteristics, including its stable oxygen and carbon isotope composition. Using these parameters as unbiased proxies requires a firm knowledge of all potential confounding factors influencing foraminiferal shell geochemistry. One such parameter is the shell calcification intensity

Results are presented and compared for the Community Earth System Model version 2 (CESM2) simulations of the middle Holocene (MH, 6 ka) and Last Interglacial (LIG, 127 ka). These simulations are designated as Tier 1 experiments (midHolocene and lig127k) for the Coupled Model Intercomparison Project phase 6 (CMIP6) and the Paleoclimate Modeling Intercomparison Project phase 4 (PMIP4). They use the low‐top

The Piacenzian (3.60 – 2.58 Ma) covers the last stage of the Neogene just before the Earth’s climate turned from relatively stable warm conditions to the cooler climate with high amplitude glacial‐interglacial oscillations of the Pleistocene. Even during this period early fluctuations towards cooler conditions occurred and sea surface temperature (SST) reconstructions show stepwise increasing gradients

Dry biomes occupy ~35% of the landscape in the Neotropics but these are heavily human‐disturbed. In spite of their importance, we still do not fully understand their origins and how they are sustained. The Guajira Peninsula in northern Colombia is dominated by dry biomes and has a rich Neogene fossil record. Here, we have analyzed its changes in vegetation and precipitation during the Neogene using

During the past four decades significant decrease in Arctic sea ice and a dramatic ice mass loss of the Greenland Ice Sheet (GIS) has been coincident with global warming and an increase in atmospheric CO2. In Northeast Greenland significant mass loss from the outlet glaciers Nioghalvfjerdsbræ (79NG) and Zachariæ Isstrøm (ZI) and intensive seasonal breakup of the local Norske Øer Ice Barrier (NØIB)

No abstract is available for this article.

The isotopic composition of Si in biogenic silica (BSi), such as opal buried in the oceans' sediments, has changed over time. Paleorecords suggest that the isotopic composition, described in terms of δ30Si, was generally much lower during glacial times than today. There is consensus that this variability is attributable to differing environmental conditions at the respective time of BSi production

Eight ferromanganese crust samples spanning the complete depth range of Tropic Seamount in the northeast Atlantic were analyzed for Pb and Nd isotopes to reconstruct water mass origin and mixing over the last 75 Ma. Pb isotopes were determined by laser ablation multicollector inductively coupled plasma mass spectrometer (LA‐MC‐ICP‐MS), which enables the rapid production of large, high spatial resolution

The Miocene epoch witnessed major changes in climate. The marine oxygen isotope record, our best single continuous representation of the time interval, contains large shifts indicating substantial changes in the glaciation of Antarctica and/or deep ocean temperatures, with the interval of the most depleted isotopic composition occurring between ~18 and 13.9 Ma (mid‐Miocene Climatic Optimum [MCO]).

Super greenhouse temperatures at the onset of the Cenomanian‐Turonian oceanic anoxic event (OAE 2) have been widely linked with large igneous province (LIP) volcanic activity. However, the extent to which volcanism influenced subsequent climate changes throughout OAE 2, such as global cooling during the Plenus Cold Event (PCE) early in the OAE, and the subsequent return to very warm conditions through

Several studies indicate that North Atlantic Deep Water (NADW) formation might have initiated during the globally warm Eocene (56–34 Ma). However, constraints on Eocene surface ocean conditions in source regions presently conducive to deep water formation are sparse. Here we test whether ocean conditions of the middle Eocene Labrador Sea might have allowed for deep water formation by applying (organic)

In Antarctic and Subantarctic environments, 14C‐based age determination is often challenging due to unknown reservoir effects, low organic carbon contents of sediments, and high contributions of petrogenic (14C‐free) carbon in ice marginal settings. In this study, we evaluate possible benefits and challenges of compound‐specific radiocarbon analysis (CSRA) as a tool for age determination of marine

Carbon‐rich layers exist at both sides of the Mediterranean Sea sedimentary record and are called sapropels and organic rich layers (ORLs), respectively, in the eastern and western basins. They have different levels of organic carbon accumulation and seafloor oxygen deprivation. The most recent sapropel and ORL depositions have a different timing, approximately 10.8–6.1 and 14.5–9.0 ka, respectively

Lipid biomarkers archived in marine sediments include widely applied proxies to reconstruct sea surface temperature (SST). Two prominent groups of SST sensitive biomarkers are long‐chain alkenones from haptophyte algae and glycerol dibiphytanyl glycerol tetraethers (GDGTs) from planktonic Thaumarchaeota. The corresponding proxies, and TEX86, respectively, are strongly correlated with mean annual SST

The West Pacific Warm Pool (WPWP)'s response to increased pCO2 during the Pliocene is a key model validation target. Different temperature proxies show different trends: The foraminiferal Mg/Ca sea surface temperature (SST) record shows Pliocene WPWP temperatures ~1.2°C cooler than today (Wara et al., 2005, https://doi.org/10.1126/science.1112596), whereas a TEX86 study finds a cooling trend and claims

Ocean gateways facilitate circulation between ocean basins, thereby impacting global climate. The Indonesian Gateway transports water from the Pacific to the Indian Ocean via the Indonesian Throughflow (ITF) and drives the strength and intensity of the modern Leeuwin Current, which carries warm equatorial waters along the western coast of Australia to higher latitudes. Therefore, ITF dynamics are a

We present the δ11B of well‐preserved brachiopod fossils coupled with geochemical modeling to examine how seawater boron responded to abrupt and dynamic climate changes in the Late Paleozoic. The Late Carboniferous, a time of major coal formation and glacioeustatic sea level changes, is characterized by relatively stable brachiopod δ11B of 15–17‰, similar to values seen in modern brachiopods. Brachiopod

Mediterranean Outflow Water (MOW) adds salt and density to open ocean intermediate waters and is therefore an important motor of Atlantic meridional overturning circulation (AMOC) and climate variability. However, the variability in strength and depth of MOW on geological timescales is poorly documented. Here we present new detailed records, with excellent age control, of MOW variability from 416 ka

We reconstructed the variability of the Earth's strongest hydrological system, the Indian monsoon, over the interval 6.24 to 4.91 Ma at International Ocean Discovery Program (IODP) Expedition 353 Site U1448 in the Andaman Sea. We integrated high‐resolution benthic and planktic foraminiferal carbon and oxygen isotopes with Mg/Ca measurements of the mixed layer foraminifer Trilobatus sacculifer to reconstruct

The middle Miocene is an important analogue for potential future warm climates. However, few independent deep ocean temperature records exist, though these are important for climate model validation and estimates of changes in ice volume. Existing records, all based on the foraminiferal Mg/Ca proxy, suggest that bottom water temperatures were 5 – 8°C warmer than present. In order to improve confidence

The past provides evidence of abrupt climate shifts and changes in the frequency of climate and weather extremes. We explore the nonlinear response to orbital forcing and then consider climate millennial variability down to daily weather events. Orbital changes are translated into regional responses in temperature, where the precessional response is related to nonlinearities and seasonal biases in

Neogloboquadrina pachyderma is the dominant species of planktonic foraminifera found in polar waters and is therefore invaluable for paleoceanographic studies of the high latitudes. However, the geochemistry of this species is complicated due to the development of a thick calcite crust in its final growth stage and at greater depths within the water column. We analyzed the in situ Mg/Ca and δ18O in

No abstract is available for this article.

To investigate past changes in the Mediterranean Overflow Water (MOW) to the Atlantic, we analyzed the strength of the MOW and benthic δ13C along the last 250 kyr at Integrated Ocean Drilling Program (IODP) Site U1389 in the Gulf of Cadiz, near the Strait of Gibraltar. Both the strength of the MOW and the benthic δ13C were mainly driven by precession‐controlled fluctuations in the Mediterranean hydrologic

Fossil‐rich sediments of the Santa Cruz Formation, Patagonia, Argentina, span the initiation of the Miocene Climatic Optimum (MCO), the most recent period of warm and wet conditions in the Cenozoic. These conditions drove the expansion of tropical and subtropical ecosystems to much higher latitudes, with the fossiliferous Santa Cruz Formation recording one of the southernmost examples. We collected

Pre‐Quaternary paleoclimate studies in Australia mainly focus on terrestrial records from the southeastern part of the continent. IODP Expedition 356 drilled on the northwestern Australian shelf, yielding Miocene‐Pleistocene paleoclimate records in an area where climate archives are scarce. Postexpedition research revealed a dry‐to‐humid transition across the latest Miocene and early Pliocene (start

Thermocline‐dwelling foraminifera calcify over a depth range of several hundred meters; analysis of individual shells therefore allows insight to the hydrography of the upper water column. We analyzed δ18O, δ13C, and Mg/Ca of individual tests of the planktonic foraminifera Globorotalia inflata from a sediment core (GeoB7926‐2) obtained from 20°N in the eastern tropical Atlantic. To facilitate sample

In the modern Southern Ocean and during the last interglacial period, Marine Isotope Stage 5e, there are observations that point to reduced Antarctic Bottom Water (AABW) formation. These reductions are believed to be driven by an increase in the strength of the Southern Ocean density stratification due to Antarctic ice melt‐induced surface water freshening. Any reduction in AABW formation has important

Accurate estimation of central tropical Pacific (CTP) climate variability on interannual to centennial time scales is required for robust projections of future global climate trends. Here we outline an approach that blends instrumental and coral proxy observations to yield a continuous, monthly resolved record of climate evolution in the CTP spanning the past 160 years. We concatenate coral oxygen

A detailed biostratigraphic, chemostratigraphic, and chronostratigraphic study was carried out in the South‐Western margin of the Neo‐Tethys ocean (Tunisia) covering the Eocene‐Oligocene interval to report potential paleoenvironmental and paleoclimatic changes associated with the growth of the Antarctic ice sheet (AIS). The studied section consists of marls and limestones extending from the Helicosphaera

The abundance and composition of modern phytoplankton are primarily related to equator‐to‐pole temperature gradients and global ocean circulation, which in turn determine the availability of nutrients in the photic zone. The nutricline is found at greater depths in warm, tropical waters, whereas more vigorous surface mixing in higher latitudes (seasonally) enhances nutrient availability and primary

Understanding hemisphere‐wide millennial‐scale temperature variability during past glacials in response to ice sheet dynamics and orbital forcing is one of the key targets for Quaternary climate research. While an inland propagation of abrupt temperature changes into Eurasia from the North Atlantic realm during the last glacial (Weichselian) receives increasingly broad support, much less is known regarding

The mechanisms controlling changes in atmospheric circulation and rainfall over the Indo‐Pacific Warm Pool (IPWP) on glacial‐interglacial timescales remain a subject of considerable debate. Continental shelf exposure, through sea‐level drawdown during glacial periods, has been proposed as an important and possibly dominant control on rainfall intensity over the IPWP and Indian Ocean. However, longer

The opening of the Drake Passage (DP) during the Cenozoic is a tectonic event of paramount importance for the development of modern ocean characteristics. Notably, it has been suggested that it exerts a primary role in the onset of the Antarctic Circumpolar Current (ACC) formation, in the cooling of high‐latitude South Atlantic waters and in the initiation of North Atlantic Deep Water (NADW) formation

Recent reconstructions of bottom water δ13C during the last interglacial (LIG) suggest short‐lived variability in the Atlantic meridional overturning circulation (AMOC). Spontaneous (multi) centennial‐scale variability of the AMOC simulated in the Earth system model of intermediate complexity iLOVECLIM are investigated for that period. The model simulates abrupt AMOC transitions occurring at 300 years

Mechanisms controlling the long‐ and short‐term variability of the Indian Summer Monsoon (ISM) and high‐elevation environmental change have largely been examined using low‐elevation or marine records with less emphasis on high‐elevation non‐marine records. We address this using a high‐resolution, long‐term record from upper Miocene–lower Pleistocene (~9.0–2.2 Ma) fluvio‐lacustrine strata in the Zhada

Planktonic Foraminifera are widely used in paleoceanographic reconstructions, although studies of their trophic interactions are still rare, especially those focusing on predation. Drilling holes are the most frequent traces of bioerosion in foraminifer tests, but environmental factors that control bioerosion are not yet understood. To determine if paleoceanographic variables are associated with bioerosion

No abstract is available for this article.

The arid southwestern United States is susceptible to sustained droughts that impact water resources and economic activity for millions of residents. Previous work has not systematically investigated the structure, timing, and possible forcings of Holocene Great Basin sub‐orbital hydroclimate changes, impeding our ability to understand the potential future controls on Southwestern aridity. The objective

Changes in ocean gateway configuration can induce basin‐scale rearrangements in ocean current characteristics. However, there is large uncertainty in the relative timing of the Oligocene/Miocene subsidence histories of the Greenland‐Scotland Ridge (GSR) and the Fram Strait (FS). By using a climate model, we investigate the temperature and salinity changes in response to the subsidence of these two

Coral records of surface‐ocean conditions extend our knowledge of interannual El Niño–Southern Oscillation (ENSO) variability into the preinstrumental period. That said, the wide range of natural variability within the climate system as well as multiple sources of uncertainties inherent to the coral archive produce challenges for the paleoclimate community to detect forced changes in ENSO using coral

Climate conditions and instantaneous depositional events can influence the relative contribution of sediments from terrestrial and marine environments and ultimately the quantity and composition of carbon buried in the sediment record. Here, we analyze the elemental, isotopic, and organic geochemical composition of marine sediments to identify terrestrial and marine sources in sediment horizons associated

A 150‐ to 220‐year lag between abrupt Greenland warming and maximum Antarctic warming characterizes past glacial Dansgaard‐Oeschger events. In a modeling study, we investigate how the cross‐equatorial oceanic heat transport (COHT) might drive this phasing during an abrupt Northern Hemisphere (NH) warming. We use the MITgcm in an idealized continental configuration with two ocean basins, one wider,

Modern observations indicate that variations in marine phytoplankton stoichiometry correlate with the boundaries of major surface waters. For example, phytoplankton in the oligotrophic subtropical gyres typically have much higher C:N:P ratios (i.e., higher C:P and higher N:P ratios) than those in eutrophic upwelling regions and polar regions. Such a spatial pattern points to nutrient availability as

Combining magnetostratigraphic and carbon isotopic data for the late Miocene can provide a temporal framework for an isotopic shift first documented in soil carbonate nodules of northern Pakistan. The shift has been interpreted as a change in vegetation from trees and shrubs (using the C3 photosynthetic pathway) to grassland (using the C4 pathway). The cause of the event has been hotly debated and

The Pliocene (5.3–2.6 Ma), an epoch with periods of climatic warmth and possible analogue for the future, has been well‐characterized globally by marine geochemical proxies. However, far less is known about Pliocene warmth at continental high latitudes, where the greatest impacts of warming are expected. This study seeks to better characterize the Pliocene climate of central Alaska and Yukon based

Modern biogeochemical conditions of the Eastern Equatorial Pacific (EEP) region are characterized by high macronutrient concentrations but low phytoplankton abundance due to both iron and silicic acid limitation. Since primary producers significantly impact the global carbon cycle, paleoproductivity in relation to climate change and nutrient availability in this region has been a topic of a number

The Antarctic Circumpolar Current (ACC) is the world's largest current system connecting all three major basins of the global ocean. Our knowledge of glacial‐interglacial changes in ACC dynamics in the southeast Pacific is not well constrained and presently only based on reconstructions covering the last glacial cycle. Here we use a combination of mean sortable silt grain size of the terrigenous sediment

The Mid‐Pliocene Warm Period (MPWP, 2.9 to 3.3 Ma), along with older Pliocene (3.2 to 5.3 Ma) records, offers potential past analogues for our 400‐ppmv world. The coastal geology of western and southern coasts of the Republic of South Africa exposes an abundance of marine deposits of Pliocene and Pleistocene age. In this study, we report differential GPS elevations, detailed stratigraphic descriptions

The Kuroshio Current is a major hydrographical feature of the modern East China Sea, but it has been suggested that its flow was diverted to the east of the Ryukyu Arc at the Last Glacial Maximum. Shoaling of the Yonaguni Depression has also been proposed as a cause of Kuroshio Current diversion which, while unlikely to have been significant at the Last Glacial Maximum, may have been an important consideration

No abstract is available for this article.

Arctic precipitation is predicted to increase this century. Records of past precipitation seasonality provide baselines for a mechanistic understanding of the dynamics controlling Arctic precipitation. We present an approach to reconstruct Arctic precipitation seasonality using stable hydrogen isotopes (δ2H) of aquatic plant waxes in neighboring lakes with contrasting water residence times and present

We investigate the geometry and ventilation of the water masses within bathyal depths (~1,500 to ~2,500 m) of the Southeast Pacific (SEP), inferring the lower depth limit variations of the Antarctic Intermediate Water (AAIW) since ~22 kyr cal. BP. We use three cores collected at the upper limit of the Pacific deep waters, between 41°S and 49°S, and one core at a greater depth within this same water

Key features of late Neogene climate remain uncertain due to conflicting records derived from different sea surface temperature (SST) proxies. To understand scenarios in which proxy‐derived temperature estimates can be used interchangeably or are instead measuring different aspects of the same system, it is necessary to explore both the consistencies and differences between specific paleothermometers

Negative excursions in the stable carbon isotopic composition (δ13C) at Atlantic intermediate to mid‐depths are common features of millennial‐scale events named Heinrich Stadials. The mechanisms behind these excursions are not yet fully understood, but most hypotheses agree on the central role played by the weakening of the Atlantic meridional overturning circulation. Marine records registering millennial‐scale

A controversial aspect of Pliocene (5.3–2.6 Ma) climate is whether El Niño‐like (El Padre) conditions, characterized by a reduced trans‐equatorial sea‐surface temperature (SST) gradient, prevailed across the Pacific. Evidence for El Padre is chiefly based on reconstructions of sea‐surface conditions derived from the oxygen isotope (δ18O) and Mg/Ca compositions of shells belonging to the planktic foraminifer

The Western Pacific Warm Pool (WPWP) constitutes an important component within the global climate system by providing an enormous amount of heat and moisture to the global atmosphere. Nevertheless, past variability of oceanography and climate across the WPWP is still debated. Here, we compile newly generated and published surface and thermocline temperature and seawater stable oxygen isotope (δ18OSW)

No abstract is available for this article.

The Middle Pleistocene Transition (MPT, ~641–920 ka) represents a period of the Quaternary climate when, in the absence of substantial changes in orbital forcing, the climate progressively shifted to the 100 ka asymmetrical glacial–interglacial cyclicity characterizing the current climate. The causes of this change remain still uncertain but several lines of evidence suggested the carbon storage of

Astrochronology depends on the faithful record of insolation forcing in climatic proxies, including the carbon isotope composition measured on bulk carbonates (δ13Ccarb). In marginal basins close to carbonate platforms, the source of carbonate is varied, which can impact the record of the astronomical cycles in the δ13Ccarb signal. We compare here the δ13Ccarb values together with detrital and weathering