Description: Twenty-first century atmospheric pCO2 concentrations will rise to levels that the Earth has not experienced for more than 30 Myr (〉500 ppm). Geological records from the Paleogene (66 to 23 million years ago, Ma) provide the means to decipher the operation of the Earth System under high pCO2 conditions, but tackling this scientifically and societally important problem requires precise integration of climate datasets across latitudes and ocean basins. Currently we lack the continuous high- resolution archives from the southern high latitudes that we need to provide comprehensive information on (sub)polar climate evolution and test competing hypothesized mechanisms of Paleogene climate change, such as the influence of atmospheric pCO2 change versus the opening of Southern Ocean tectonic gateways to deep-water circulation. Here we present the new International Ocean Discovery Program (IODP) pre-proposal 862-Pre (SW Atlantic Paleogene Climate) designed to drill a depth transect of Paleogene sites in the subantarctic South Atlantic Ocean on the easternmost tip of the Falkland Plateau (Maurice Ewing Bank and Georgia Basin). In the modern ocean, this is a critical area for deep-water mixing and communication between the Pacific and Atlantic oceans across the Drake Passage, with local bathymetry controlling the dispersal and propagation of deep- and bottom-waters throughout the Atlantic. The plan is to recover a composite of Paleogene sections spanning an extensive range of paleo-water depths (~500-4500 m) to determine the timing and variability of shallow- and deep-water connectivity across the Drake Passage and to test whether the onset of a proto-Antarctic Circumpolar Current (ACC) circulation had a direct impact on high-latitude and global climate evolution. These drillcores will thus provide crucial insight on the long-standing question of the relative influence of atmospheric pCO2 drawdown vs. Southern Ocean gateways in driving Paleogene climate evolution. The target sites are also ideally positioned to assess the relationships between local tectonic subsidence of deep-water barriers, high-latitude climate change, and the onset of bottom-water production in the Weddell Sea and northward propagation into to the deep western Atlantic - a process that, along with ACC circulation, fundamentally altered Cenozoic circulation in the Atlantic. Multi-proxy datasets from expanded hemipelagic sections will shed new light on climate change, biotic shifts, and deep-sea chemistry during the Paleogene, allowing evaluation of: (i) the magnitude of temperature change and response of high-latitude plankton groups across transient 'greenhouse' events, (ii) the initiation of southern high latitude cooling and onset of Antarctic Peninsula glaciation during the middle Eocene - early Oligocene 'greenhouse' to 'icehouse' transition, and (iii) variation in the Calcite Compensation Depth in the South Atlantic and its relation to changes in global carbon cycling. Following the positive recommendation by the Science Evaluation Panel (SEP) for IODP 862-Pre two companion seismic reflection survey and piston coring operations in the eastern Falkland Plateau region of the subantarctic southwest Atlantic Ocean have been developed. One Site Survey Investigation (SSI) cruise led by Uenzelmann-Neben (AWI, Bremerhaven) and Westerhold (MARUM, Bremen) is proposed to survey the Maurice Ewing Bank extending southward across the Falkland Trough. The complementary SSI led by Bohaty (Univ. Southampton, UK) is proposed to survey the eastern half of the region across the Georgia Basin and Northeast Georgia Rise. The collaboration between German and UK groups will feasibly provide the extensive data coverage needed to survey the entire east–west transect of drillsites to meet the scientific objectives of 862-Pre. This transect is a fundamental requirement to allow reconstruction of deep-water properties across a range of palaeo-water depths and surface- water conditions across several modern frontal boundaries.

Description: The late Miocene-early Pliocene was a time of global cooling and the development of modern meridional thermal gradients. Equatorial Pacific sea surface conditions potentially played an important role in this global climate transition, but their evolution is poorly understood. Here, we present the first continuous late Miocene-early Pliocene (8.0-4.4 Ma) planktic foraminiferal stable isotope records from eastern equatorial Pacific Integrated Ocean Drilling Program Site U1338, with a new astrochronology spanning 8.0-3.5 Ma. Mg/Ca analyses on surface dwelling foraminifera Trilobatus sacculifer from carefully selected samples suggest mean sea-surface-temperatures (SSTs) are ~27.8±1.1°C (1 Sigma) between 6.4-5.5 Ma. The planktic foraminiferal d18O record implies a 2°C cooling between 7.2-6.1 Ma and an up to 3°C warming between 6.1-4.4 Ma, consistent with observed tropical alkenone paleo-SSTs. Diverging fine-fraction-to-foraminiferal d13C gradients likely suggest increased upwelling from 7.1-6.0 and 5.8-4.6 Ma, concurrent with the globally recognized late Miocene Biogenic Bloom. This study shows that both warm and asymmetric mean states occurred in the equatorial Pacific during the late Miocene-early Pliocene. Between 8.0-6.5 and 5.2-4.4 Ma, low east-west d18O and SST gradients and generally warm conditions prevailed. However, an asymmetric mean climate state developed between 6.5-5.7 Ma, with larger east-west d18O and SST gradients and eastern equatorial Pacific cooling. The asymmetric mean state suggests stronger trade winds developed, driven by increased meridional thermal gradients associated with global cooling and declining atmospheric pCO2 concentrations. These oscillations in equatorial Pacific mean state are reinforced by Antarctic cryosphere expansion and related changes in oceanic gateways (e.g., Central American Seaway/Indonesian Throughflow restriction).

Description: To explore cause and consequences of past climate change, very accurate age models such as those provided by the astronomical timescale (ATS) are needed. Beyond 40 million years the accuracy of the ATS critically depends on the correctness of orbital models and radioisotopic dating techniques. Discrepancies in the age dating of sedimentary successions and the lack of suitable records spanning the middle Eocene have prevented development of a continuous astronomically calibrated geological timescale for the entire Cenozoic Era. We now solve this problem by constructing an independent astrochronological stratigraphy based on Earth's stable 405 kyr eccentricity cycle between 41 and 48 million years ago (Ma) with new data from deep-sea sedimentary sequences in the South Atlantic Ocean. This new link completes the Paleogene astronomical timescale and confirms the intercalibration of radioisotopic and astronomical dating methods back through the Paleocene-Eocene Thermal Maximum (PETM, 55.930 Ma) and the Cretaceous-Paleogene boundary (66.022 Ma). Coupling of the Paleogene 405 kyr cyclostratigraphic frameworks across the middle Eocene further paves the way for extending the ATS into the Mesozoic.

Description: The Late Cretaceous-Early Paleogene is the most recent period of Earth history that experienced sustained global greenhouse warmth and was characterised by a dynamic carbon cycle. Yet, knowledge of ambient climate conditions and the evolution of atmospheric pCO2 at this time, along with their relation to forcing mechanisms, are still poorly constrained. Here we present an unprecedented 14.75 million year long high-resolution orbitally-tuned record of paired climate change and carbon-cycling (based on the oxygen and carbon isotope composition of benthic foraminiferal tests) compiled to date for the enigmatic Late Cretaceous to Early Eocene, and compare these records to the most up-to-date compilation of atmospheric pCO2 records for this time. We identify eccentricity as the dominant pacemaker of the observed climate and carbon cycle changes, through the modulation of precession. The carbon cycle (e.g., d13C) lagged changes in climate by ~22,800 years within the long eccentricity (405,000 year) band and ~3,000-4,500 years within the short eccentricity (100,000 year) band, suggesting that light carbon was released as a positive feedback to warming induced by small changes in orbital forcing. The majority of the hyperthermals of this time period occur during maxima in the long eccentricity cycle, with the exception of the Paleocene-Eocene Thermal Maximum and Late Maastrichtian warming event, which are likely to have been triggered by Large Igneous Province volcanism.