ALBERT

Description: We generated benthic isotope records from Ocean Drilling Program (ODP) site 981 on the Feni drift (2173 m water depth) and from ODP site 983 on the Gardar drift (1983 m water depth) to examine the interaction between North Atlantic Deep Water (NADW) and Glacial North Atlantic Intermediate Water (GNAIW) formation from 2.0 to 1.4 Ma. We find NADW at both sites during interglacial periods, and a mix of NADW and Southern Ocean water at the Feini drift during most glacial periods. Prior to 1.7 Ma we find no evidence ofr GNAIW at the Gardar drift site. Instead, glacial Gardar drift delta13C values are as low or lower than values for all other sites in the North Atlantic and reflect continued glacial overflow from the Nordic seas. After 1.7 Ma Gardar drift delta13C values increase and suggest that there was GNAIW at the Gardar drift site during some glacial intervals. Overall, we find that NADW and GNAIW production changed around 1.7 Ma in concert with changes in sea surface temperature and salinity and in the Earth's obliquity cycle.

Description: In order to examine whether the paleoceanographic nutrient proxies, d13C and cadmium/calcium in foraminiferal calcite, are well coupled to nutrients in the region of North Atlantic Deep Water formation, we present da ta from two transects of the Greenland-Iceland-Norwegian Seas. Along Transect A (74.3°N, 18.3°E to 75.0°N, 12.5°W, 15 stations), we measured phosphate and Cd concentrations of modern surface sea water. Along Transect B (64.5°N, 0.7°W to 70.4°N, 18.2°W, 14 stations) we measured Cd/Ca ratios and d13C of the planktonic foraminifera Neogloboquadrina pachyderma sinistral in core top sediments. Our results indicate that Cd and phosphate both vary with surface water mass and are well correlated along Transect A. Our planktonic foraminiferal d13C data indicate similar nutrient variation with water mass along Transect B. Our Cd/Ca data hint at the same type of nutrient variability, but interpretations are hampered by low values close to the detection limit of this technique and therefore relatively large error bars. We also measured Cd and phosphate concentrations in water depth profiles at three sites along Transect A and the d13C of the benthic foraminifera Cibicidoides wuellerstorfi along Transect B. Modern sea water depth profiles along Transect A have nutrient depletions at the surface and then constant values at depths greater than 100 meters. The d13C of planktonic and benthic foraminifera from Transect B plotted versus depth also reflect surface nutrient depletion and deep nutrient enrichment as seen at Transect A, with a small difference between intermediate and deep waters. Overall we see no evidence for decoupling of Cd/Ca ratio and d13C in foraminiferal calcite from water column nutrient concentrations along these transects in a region of North Atlantic Deep Water formation.

Description: The Mid-Brunhes Transition (MBT) began ∼430ka with an increase in the amplitude of the 100-kyr climate cycles of the past 800,000 years. The MBT has been identified in ice-core records, which indicate interglaciations became warmer with higher atmospheric CO2 levels after the MBT, and benthic oxygen isotope (δ18O) records, which suggest that post-MBT interglaciations had higher sea levels than pre-MBT interglaciations. It remains unclear, however, whether the MBT was a globally synchronous phenomenon that included other components of the climate system. Here we further characterize changes in the climate system across the MBT through statistical analyses of ice-core and δ18O records as well as sea-surface temperature, benthic carbon isotope, and dust accumulation records. Our results demonstrate that the MBT was a global event with a significant increase in climate variance in most components of the climate system assessed here. However, our results indicate that the onset of high-amplitude variability in temperature, atmospheric CO2, and sea level at ∼430ka was preceded by changes in the carbon cycle, ice sheets, and monsoon strength during MIS 14 and 13.

Description: We present a 5.3-Myr stack (the ''LR04'' stack) of benthic d18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm. This is the first benthic delta18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene. We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the delta18O stack to a simple ice model based on 21 June insolation at 65 N. Stacked sedimentation rates provide additional age model constraints to prevent overtuning. Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 5.3 Myr and in the precession band for more than half of the record. The LR04 stack contains significantly more variance in benthic delta18O than previously published stacks of the late Pleistocene as the result of higher resolution records, a better alignment technique, and a greater percentage of records from the Atlantic. Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of delta18O from 2.7-1.6 Ma is primarily a deep-water temperature signal and that the phase of d18O precession response changed suddenly at 1.6 Ma.

Description: The presence-absence data for macrobenthic fauna that has been collected in Mingulay Reef Complex (Scotland, UK) across 79 stations over the years 2003, 2005, 2009, 2010 and 2011. The collection of the benthic samples has been carried out using a Van-Veen grab, mainly from hard habitats (e.g. live and dead coral framework). About 60% of the macrofaunal specimens have been identified at species level using high quality taxonomic keys and advice from taxonomy experts. Most common taxonomic groups analysed here are molluscs, polychaetes, arthropods, bryozoans, anthozoans, tunicates and brachiopods. The collection of the specimens is now deposited at the National Museums of Scotland (see the attached excel file for details). The enviromental data contains information about coordinates and environmental settings at stations where macrobenthic samples mentioned above, were collected. The environmental settings that are included in the file refer to the years 2003, 2005, 2009, 2010, 2011. For more information on the environmental variables have a look in Henry et al. 2010 (doi:10.1007/s00338-009-0577-6) and Henry et al. 2013 (doi:10.5194/bg-10-2737-2013). The environmental variables included in the excel file are: type of macrohabitat (i.e. muddy sand, rubble, rock, live coral, dead framework, live & dead framework), depth (m), slope, ruggedness, broad-scale bathymetric position index, fine-scale bathymetric position index, average current speed (m/s), maximum current speed (m/s), northness, eastness, winter North Atlantic Oscillation Index (same year), winter North Atlantic Oscillation Index (previous year), annual average bottom temperature (same year), annual average bottom salinity (same year). Extraction of bathymetric (depth) and topographic data [slope, aspect, northness, eastness, ruggedness, standardised broad-scale bathymetric position index (BPI; with an inner radius of 1 cell and an outer radius of 5 cells), fine-scale BPI (with an inner radius of 1 cell and an outer radius of 3 cells)] was based on multibeam echosounder data, using the Spatial Analyst and Benthic Terrain Modeler toolboxes in ArcGIS v.10.6.1 Average and maximum current speed values (m/s) were extracted by the ArcGIS v. 10.6.1 Spatial Analyst toolbox using data generated by a high-resolution 3D ocean model created for the MRC by Moreno-Navas et al. (2014). Data for the winter NAOI (DJFM) (Hurrell et al., 2003) were downloaded from the National Center for Atmospheric Research/University Corporation for Atmospheric Research website (climatedataguide.ucar.edu; data accessed on 28/02/2019).

Description: The Antarctic Circumpolar Current is the world's largest current system connecting all major ocean basins of the global ocean. Its flow, driven by strong westerly winds, is constricted to its narrowest extent in the Drake Passage, located between South America and the Antarctic Peninsula. Due to the remoteness of the area, harsh weather conditions and strong bottom currents, sediment recovery is difficult and data coverage is still inadequate. Here, we report on the composition of 51 surface sediments collected during the R/V Polarstern PS97 expedition (February-April 2016) across the western and central Drake Passage, from the Chilean/Argentinian continental margin to the South Shetland Islands and the Bransfield Strait (water depth: ∼100-4000 m). We studied microfossils (diatoms), bulk sediment composition and geochemical proxies (biogenic opal, organic carbon, calcium carbonate, carbon and nitrogen stable isotopes, sterols and photosynthetic pigments), and evaluated how they respond to, and reflect oceanic domains and polar to subpolar frontal systems in this region. Our multi-proxy approach shows a strong relationship between the composition of surface sediments and ocean productivity, terrigenous input, intensity of ocean currents, and ice proximity, clearly differentiating among 4 biogeographical zones. The Subantarctic Zone was characterized by warmer-water diatoms, high carbonate (〉45%) and low organic carbon contents (avg. 0.26%), as well as low concentrations of pigments (avg. 1.75 μg/g) and sterols (avg. 0.90 μg/g). A general N-S transition from carbonate-rich to opal-rich sediment was observed at Drake Passage sites of the Polar Front and Permanently Open Ocean Zone. These sites were characterized by low organic carbon content (0.22%), high relative abundances of heavily silicified diatoms (≥60% Fragilariopsis kerguelensis), and abundant foraminifera at shallower stations. Approaching the Antarctic Peninsula in the Transitional Zone, an increase in the concentrations of pigments and sterols (avg. 2.57 μg/g and 1.44 μg/g, respectively) and a strong decrease in carbonate content was observed. The seasonal Sea-Ice Zone in the southern section of the study area, had the highest contents of biogenic opal (avg. 14.6%) and organic carbon (avg. 0.7%), low carbonate contents (avg. 2.4%), with the occurrence of sea-ice-related diatoms and sterols. In all zones, terrigenous input was detected, although carbon/nitrogen ratios and δ13Corg suggest a predominance of marine-derived organic matter; lower values of δ13Corg occurred south of the Polar Front. The new results presented here constitute a highly valuable reference dataset for the calibration of microfossil and geochemical proxies against observational data and provide a useful regional baseline for future paleo-research.

Description: Increasing pCO2 (partial pressure of CO2 ) in an "acidified" ocean will affect phytoplankton community structure, but manipulation experiments with assemblages briefly acclimated to simulated future conditions may not accurately predict the long-term evolutionary shifts that could affect inter-specific competitive success. We assessed community structure changes in a natural mixed dinoflagellate bloom incubated at three pCO2 levels (230, 433, and 765 ppm) in a short-term experiment (2 weeks). The four dominant species were then isolated from each treatment into clonal cultures, and maintained at all three pCO2 levels for approximately 1 year. Periodically (4, 8, and 12 months), these pCO2 -conditioned clones were recombined into artificial communities, and allowed to compete at their conditioning pCO2 level or at higher and lower levels. The dominant species in these artificial communities of CO2 -conditioned clones differed from those in the original short-term experiment, but individual species relative abundance trends across pCO2 treatments were often similar. Specific growth rates showed no strong evidence for fitness increases attributable to conditioning pCO2 level. Although pCO2 significantly structured our experimental communities, conditioning time and biotic interactions like mixotrophy also had major roles in determining competitive outcomes. New methods of carrying out extended mixed species experiments are needed to accurately predict future long-term phytoplankton community responses to changing pCO2 .

Description: This dataset includes counts, percentages and concentrations of all dinoflagellate cyst taxa identified in the benthic nephloid layer (BNL), cyst rain and surface sediments collected along a land-sea transect off Figueira da Foz (NW Portugal, Atlantic Iberian margin) during the Hydrographic Institute (IH)-HABWAVE cruise (16th-19th September 2019). Sampling of the dinoflagellate cyst community in the BNL, the water column (sediment trap) and the surface sediments (together with studies of spatio-temporal changes in physical properties) were carried out in order to investigate the dinoflagellate cyst distribution and the factors (physical and biological) affecting it. Water samples for cyst analyses were collected by a rosette firing system associated with the CTD, and the cyst rain using a sediment trap situated above the BNL. They were filtered (40-47 l) on board through a 150µm-nylon mesh sieve onto a 10µm-calibrated stainless steel sieve (Retsch). In the laboratory, cysts were concentrated by centrifugation. Full and empty cysts were counted to investigate whether a reservoir of viable cysts existed in the BNL. Surface sediments were sampled with a Smith McIntyre grab and using Plexiglass tubes (3.6 cm internal diameter) that were inserted in the sediment to recover the top 1-cm layer. Cysts from sediments were concentrated by density separation with sodium polytungstate (2.016 g/ml).

Description: This dataset comprises new data and previously published data on marine lipid biomarkers (brassicasterol, dinosterol, C37 alkenones, and the sum of them [∑PB]) in surface suspended particles at 334 stations from seven cruises between 2010 and 2015, and in surface sediments at 258 stations from eight cruises between 2006 and 2012 in the eastern China marginal seas (ECMS). Of all marine lipid biomarker data, 107 surface suspended particle samples were newly measured, with 227 surface suspended particle samples and 258 sediment samples previously published. We also provide the following oceanographic data, most of which were collected from published results (as described in the publication): sea surface temperature (SST, n = 273, from five cruises in summer of 2010–2015), salinity (n = 273, from five cruises in summer of 2010–2015), nutrient concentrations (dissolved inorganic nitrogen [DIN], dissolved inorganic phosphorus [DIP] and silicate [Si]) (n = 133, from three cruises in summer of 2011 and 2015) and Chl a (chlorophyll a, n = 229, from five cruises in summer of 2010–2014) in the surface water, as well as terrestrial biomarker [∑(C27 + C29 + C31) n-alkanes] contents (n = 226), TOC (total organic carbon content, n = 200), δ13CTOC (stable carbon isotope values for TOC, n=269), and sedimentation rate (n = 220) in surface sediments. Some data were measured using in situ CTD instrument in this study: sea surface temperature and salinity in the East China Sea in June 2010 and July 2013 (n = 54), and Chl a in the Changjiang River Estuary in August 2015 (n = 33). The contents of ∑(C27 + C29 + C31) n-alkanes in the southern Yellow Sea in April 2012 (n = 32) were also newly measured. The surface suspended particle samples were obtained by filtering on Whatman GF/F filters, and the surface sediments were collected by multiple corers or stainless-steel grab samplers. Marine and terrestrial lipid biomarkers were analyzed by gas chromatograph (Agilent 6890N) according to the method in Zhao et al. 2006 (doi: 10.1016/j.orggeochem.2005.08.022) and Wu et al. 2016 (doi: 10.1002/2015JG003167). The study resulting from this analysis has been published in Frontiers in Marine Science (doi:10.3389/fmars.2022.824181).