Description: International Ocean Discovery Program (IODP) Expedition 378 was designed to recover the first comprehensive set of Paleogene sedimentary sections from a transect of sites strategically positioned in the South Pacific to reconstruct key changes in oceanic and atmospheric circulation. These sites would have provided an unparalleled opportunity to add crucial new data and geographic coverage to existing reconstructions of Paleogene climate. In addition to the ~15 month postponement of Expedition 378 and subsequent port changes resulting in a reduction of the number of primary sites, testing and evaluation of the R/V JOIDES Resolution derrick in the weeks preceding the expedition determined that it would not support deployment of drill strings in excess of 2 km. Because of this determination, only 1 of the originally approved 7 primary sites was drilled. Expedition 378 recovered the first continuously cored, multiple-hole Paleogene sedimentary section from the southern Campbell Plateau at Site U1553. This high–southern latitude site builds on the legacy of Deep Sea Drilling Project (DSDP) Site 277, a single, partially spot cored hole, providing a unique opportunity to refine and augment existing reconstructions of the past ~66 My of climate history. This also includes the discovery of a new siliciclastic unit that had never been drilled before. As the world’s largest ocean, the Pacific Ocean is intricately linked to major changes in the global climate system. Previous drilling in the low-latitude Pacific Ocean during Ocean Drilling Program (ODP) Legs 138 and 199 and Integrated Ocean Drilling Program Expeditions 320 and 321 provided new insights into climate and carbon system dynamics, productivity changes across the zone of divergence, time-dependent calcium carbonate dissolution, bio- and magnetostratigraphy, the location of the Intertropical Convergence Zone, and evolutionary patterns for times of climatic change and upheaval. Expedition 378 in the South Pacific Ocean uniquely complements this work with a high-latitude perspective, especially because appropriate high-latitude records are unobtainable in the Northern Hemisphere of the Pacific Ocean. Site U1553 and the entire corpus of shore-based investigations will significantly contribute to the challenges of the “Climate and Ocean Change: Reading the Past, Informing the Future” theme of the IODP Science Plan (How does Earth’s climate system respond to elevated levels of atmospheric CO2? How resilient is the ocean to chemical perturbations?). Furthermore, Expedition 378 will provide material from the South Pacific Ocean in an area critical for high-latitude climate reconstructions spanning the Paleocene to late Oligocene.

Description: A systematic investigation of the spatial and temporal variability in coccolithophore abundance and distribution through the water column of the NW Iberian coastal upwelling system was performed. From July 2011 to June 2012, monthly sampling at various water depths was conducted at two parallel stations located at 42∘ N. Total coccosphere abundance was higher at the outer-shelf station, where warmer, nutrient-depleted waters favoured coccolithophore rather than phytoplanktonic diatom blooms, which are known to dominate the inner-shelf location. In seasonal terms, higher coccosphere and coccolith abundances were registered at both stations during upwelling seasons, coinciding with high irradiance levels. This was typically in conjunction with stratified, nutrient-poor conditions (i.e. relaxing upwelling conditions). However, it also occurred during some upwelling events of colder, nutrient-rich subsurface waters onto the continental shelf. Minimum abundances were generally found during downwelling periods, with unexpectedly high coccolith abundance registered in subsurface waters at the inner-shelf station. This finding can only be explained if strong storms during these downwelling periods favoured resuspension processes, thus remobilizing deposited coccoliths from surface sediments, and hence hampering the identification of autochthonous coccolithophore community structure. At both locations, the major coccolithophore assemblages were dominated by Emiliania huxleyi, small Gephyrocapsa group, Gephyrocapsa oceanica, Florisphaera profunda, Syracosphaera spp., Coronosphaera mediterranea, and Calcidiscus leptoporus. Ecological preferences of the different taxa were assessed by exploring the relationships between environmental conditions and temporal and vertical variability in coccosphere abundance. These findings provide relevant information for the use of fossil coccolith assemblages in marine sediment records, in order to infer past environmental conditions, of particular importance for Paleoceanography. Both E. huxleyi and the small Gephyrocapsa group are proposed as proxies for the upwelling regime with a distinct affinity for different stages of the upwelling event: E. huxleyi was associated with warmer, nutrient-poor and more stable water column (i.e. upwelling relaxation stage) while the small Gephyrocapsa group was linked to colder waters and higher nutrient availability (i.e. early stages of the upwelling event), similarly to G. oceanica. Conversely, F. profunda is suggested as a proxy for the downwelling regime and low-productivity conditions. The assemblage composed by Syracosphaera pulchra, Coronosphaera mediterranea, and Rhabdosphaera clavigera may be a useful indicator of the presence of subtropical waters conveyed northward by the Iberian Poleward Current. Finally, C. leptoporus is proposed as an indicator of warmer, saltier, and oligotrophic waters during the downwelling/winter regime.

Description: Oxygen and Carbon isotope data from Globigerinoides ruber from sediment core SHAK06-5K. Between 6 and 12 specimens of G. ruber were measured with a Gas Bench II connected to a Delta V Plus isotope ratio mass spectrometer at the Stable Isotope Laboratory of Climate Geology, ETH Zurich. Calibration to the Vienna Pee Dee Belemnite (VPDB) scale was accomplished using two in‐house standards previously calibrated against the NBS‐18 and NBS‐19 international standards. The associated long‐term standard deviation is 〈0.07‰. This isotopic record was concluded to be affected by the coupled effect of bioturbation with changes in the abundance of G. ruber. We refer potential users to the published article.

Description: Oxygen and Carbon isotope data from Globigerina bulloides from sediment core SHAK06-5K. Between 6 and 12 specimens of each species were measured with a Gas Bench II connected to a Delta V Plus isotope ratio mass spectrometer at the Stable Isotope Laboratory of Climate Geology, ETH Zurich. Calibration to the Vienna Pee Dee Belemnite (VPDB) scale was accomplished using two in‐house standards previously calibrated against the NBS‐18 and NBS‐19 international standards. The associated long‐term standard deviation is 〈0.07‰.

Description: Here, we present a new record of SST for the time interval 30 to 17 Ma derived from the long‐chain alkenone unsaturation ratio uk'37 and TEX 86 at Integrated Ocean Drilling Program Site 1406A in the midlatitude North Atlantic. Results confirm that warm temperatures from 24°C to over 30°C prevailed in midlatitudes in this time and suggest a transition from colder early‐middle Oligocene to warmer average conditions after 24.5 Ma. Complex and temporally varying relationships are observed between North Atlantic SST and benthic δ18O in paired samples. Significant covariation is only observed around the Oligocene‐Miocene transition, coincident with a lower average marine ice extent. These North Atlantic temperature records provide a new context in which to examine the stability of climate and the Antarctic ice sheet during the Oligocene and early Miocene.