ALBERT

Description: High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually-dated ice core record from the eastern Ross Sea. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979-2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with perhaps increased snow accumulation and decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea, but increasing in the western Ross Sea. Analysis of decadal to centennial-scale climate variability superimposed on the longer term trend reveal that periods characterised by opposing temperature trends between the Eastern and Western Ross Sea have occurred since the 3rd Century but are masked by longer-term trends. This pattern here is referred to as the Ross Sea Dipole, caused by a sensitive response of the region to dynamic interactions of the Southern Annual Mode and tropical forcings.

Description: The site for CRP-3, 12 km east of Cape Roberts (77.006°S; 103.719°E)was selecte to overlap the lower Oligocene strata cored in nearby CRP-2/2A, and to sample the oldest strata in the Victoria Land Basin (VLB) for Paleogene climatic and tectonic history. As it transpired there was underlap of the order of 10s of metres. CRP-3 was cored from 3 to 939 mbsf (metres below the sea floor), with a core recovery of 97%. Coring took place from October 9 to November 19, 1999, on 2.0 to 2.2 m of sea ice and through 295 in of water. The Cenozoic strata cored were mostly g1acially influenced marine sediments of early Oligocene age, though they may be earliest Eocene near the base, where at 823 mbsf Devonian Beacon sandstone was encountered. Following CRP-1 and CRP-2/2A, CRP-3 completes the coring of 1500 m of strata on the western margin of the VLB. Core fractures and other physical properties, such as sonic velocity, density and magnetic susceptibility, were measured throughout the core. Down-hole logs for these and other properties were taken from 20 down to 900-919 mbsf. Also, vertical seismic profile data were gathered from shots offset both along strike and up dip from the hole. Sonic velocities in CRP-3 are close to 2.0 km/s in the upper 80 m, but become significantly faster below 95 mbsf, averaging 3.2+0.6 km/s to the bottom of the hole. An exception to this is an interval of dolerite conglomerate from 790 to c. 820 mbsf with a velocity of c. 4.5 km/s. Dip of the strata also increases down-hole from 10° in the upper 100 m to around 22° at the bottom. Over 3000 fractures were logged through the hole, and borehole televiewer imagery was obtained for most of the hole for orienting core and future stress field analysis. Two high-angle crush zones, interpreted as faults, were encountered at c. 260 and c. 540 mbsf, but no stratigraphic displacement could be recognised. A third fault zone is inferred from a low angle shear zone in the upper part of a coarse dolerite conglomerate from 790 to 805 mbsf. Temperature gradient was found to be 28.5°.km-1. Basement strata cored from 823 mbsf to the bottom of the hole are largely light-reddish brown medium-grained sandstone (quartz-cemented quartzarenite) with abundant well-defined parallel lamination. These features are comparable with the middle Devonian part of the Beacon Supergroup, possibly the Arena Sandstone. This interval also includes a body of intrusive rock from 901 to 920 mbsf. It has brecciated contacts and is highly altered but some tholeiitic affinity can be recognised in the trace element chemistry. Its age is unknown. Post-Beacon sedimentation began on deeply eroded quartzarenite with the deposition of a thin sandstone breccia and conglomerate, probably as terrestrial talus, followed by dolerite conglomerate and minor sandstone of probable fluvial origin to 790 mbsf. Sedimentation continued in a marine setting, initially sandstone and conglomerate, but above c. 330 mbsf the strata include mudstone and diamictite also. The older sandstone and conglomerate beds are seen as the products of rapid episodic sedimentation. They are interpreted by some as the product of glaciofluvial discharge into shallow coastal waters, and others as a result of sediment gravity flows, perhaps glacially sourced, into deeper water. The core above c. 330 mbsf has facies that allow the recognition of cyclic sequences similar to those in CRP-2A. Fourteen unconformity-bounded sequences have been recognised from 330 mbsf to the sea floor, and are interpreted in terms of glacial advance and retreat, and sea level fall and rise. Detailed lithological descriptions on a scale of 1 :20 are presented for the full length of the core, along with core box images, as a 300 page supplement to this issue. The strata cored by CRP-3 are for the most part poorly fossiliferous, perhaps as a consequence of high sedimentation rates. Nevertheless the upper 200 m includes several siliceous microfossil- and calcareous nannoplankton-bearing intervals. Siliceous microfossils, including diatoms, ebrideans, chrysophycean cysts and silicoflagellates are abundant and well-preserved in the upper 67 m - below this level samples are barren or poorly preserved, but contain residual floras that indicate assemblages were once rich. No siliceous microfossils were found below 193 mbsf. Calcareous nannofossil have a similar distribution but are generally well preserved. Foraminifera, marine and terrestrial palynomorphs, and marine macrofossils were found consistentlsy down to c. 330 mbsf and sporadically to 525 mbsf. The taxa suggest marine deposition in water depth of c. 50 to 120 m. Below 525 mbsf no microfossils were found, apart from mudstone with similar marine and terrestrial palynomorphs at 781 mbsf, and rare miospores in the conglomerate below 790 mbsf. The terrestrial miospore record, which include several species of Nothofagus and podocarpaceous conifers, suggest low diversity woody vegetation, implying a cold temperate to periglacial climate for the hinterland throughout the period recorded by CRP-3. Important components of the warmer Eocene flora, known from erratics in southern McMurdo Sound, are missing, through the dominance of smectite in clay from strata below 650 mbsf suggests that the landscape prior to the timne of deposition had experienced a more temperate weathering regime. Biostratigraphy for ihe upper part of CRP-3 is provided by diatoms and calcareous nannofossils. The first appearance of Cavitatus jouseanus at 48 mbsf suggests an age of arround 31 Ma for this horizon. The last appearance of Transverspontis pulcheroides at 114 mbsf in an interval of relatively high abundance indicates a reasonably sound age for this horizon at 32.5 ± 0.5 Ma. The absence of particular resistant diatoms that are older than 33 Ma supports an age that is younger than this for the upper 200 m of CRP-3. Marine palynomorphs, which occur sporadically down to 525 mbsf and in a single occurrence at 781 inbsf, have biostratigraphical potential once the many new species in this and other CRP cores are described, and F0 and LO datums established. The mudstone at 781 mbsf has a new clinocyst species, rare Lejeunecysta cysts and a variety of acritarchs and prasinophytes, a varied marine assemblage that is quite different from and presumably younger than the well known Transantarctic Flora of mid to late Eocene age. On this basis and for the moment we conclude that the oldest strata in CRP-3 are earliest Oligocene (or possibly latest Eocene) in age - c. 34 Ma. Over 1l00 samples were taken for magnetic studies. Four magnetozones were recognisd on the basis of NRM intensity and magnetic susceptibility, reflecting the change in sediment composition between quartz sand-dominated and dolerite-dominated. For this report there was time only to produce a magnetostratigraphy for the upper 350 m. This interval is largely of reversed polarity (5 normal intervals total 50 of the 350 m), in contrast to the dominantly normal polarities of CRP-2/2A, and is inferred to be Chron C12R. This extends from 30.9 to 33 Ma. consistent with the biostratigraphic datums from the upper part of CRP-3. The lower limit of reversed polarity has yet to be established. The short period normal events are of interest as they may represent cryptochrons or even polarity changes not recognised in the Geomagnetic Polarity Time Scale. Erosion of the adjacent Transantarctic Mountains through the Kirkpatrick Basalt (Jurassic tholeiitic flows) and dolerite-intruded Beacon Supergroup (Devonian-Triassic sandstone) into granitic basement beneath is recorded by petrographical studies of clast and sand grain assemblages from CRP-3. The clasts in the lower 30 m of the Cenozoic section are almost entirely dolerite apart from a few blocks from the Beacon Supergroup beneath. Above this, however, both dolerite and granitoids are ubiquitous, the latter indicating that erosion had reached down to granitic basement even as the first sediment was accumulating in the VLB. No clasts or sand grains of the McMurdo Volcanic Group were found, but rare silt-size brown volcanic glass occurs in smear slides through most of CRP-3, and is interpreted as distal air fall from alkaline volcanism in northern Victoria Land. Jurassic basalt occurs as clasts sporadically throughout the sequence: in the sand fraction they decline upwards in abundance. The influence of the Devonian Beacon Supergroup is most striking for the interval from 600 to 200 mbsf, where quartz grains, from 10 to 50% of them rounded, dominate the sand fraction. Laminae of coal granules from the overlying Permian coal measures in all but the upper 150 in of the CRP-3 sequence show that these also were being eroded actively at this time. CRP-3 core completed the stratigraphical sampling of the western margin of the VLB by not only coring the oldest strata (Seismic Unit V5) but also the basin floor beneath. This has several important tectonic implications: - most of the Kirkpatrick Basalt and the Beacon Supergroup with the sills of Ferrar Dolerite have been eroded by the time down-faulting displaced the Beacon to form the basin floor. - matching the Beacon strata at the bottom of CRP-3 with the equivalent strata in the adjacent mountains suggests c. 3000 m of down-to-the-east displacement across the Transantarctic Mountain Front as a consequence of rifting and subsequent tectonic activity. - the age of the oldest Cenozoic strata in CRP-3 (c. 34 Ma), which are also the oldest strata in this section of the VLB, most likely represents the initiation of the rift subsidence of this part of the West Antarctic Rift System. This age for the oldest VLB fill is much younger than previously supposed by several tens of millions of years, but is consistent with newly documented sea floor spreading data immediately north of the northern Victoria Land continental margin. These new data sets will drive a re-evaluation of the relationship between initiation of uplift of the Transantarctic Mountains (currently c.55 Ma) and VLB subsidence.

Description: Physical, chemical and biogeochemical measurements derived from CTD-rosette deployments during three visits to site P3 (November to December, 2017) in the South Atlantic. Measurements were made during COMICS cruise DY086 on the RRS Discovery using a trace metal free Titanium Rosette (events 4, 7, 15, 19, 24, 26, 29) and a Stainless Steel Rosette (all other events). Physical parameters include temperature, salinity, density, photosynthetically active radiation and turbulence; chemical parameters include dissolved oxygen, dissolved oxygen saturation, nitrate, phosphate and silicate; biogeochemical parameters include turbidity, beam transmittance, beam attenuation, fluorescence, particulate organic carbon (POC), dissolved organic carbon (DOC), chlorophyll-a, net primary productivity (NPP), ambient leucine assimilation and bacterial cell count. To determine turbulence, a downward facing lowered acoustic doppler current profiler (LADCP, Teledyne Workhorse Monitor 300 kHz ADCP) was attached to the CTD frame. Shear and strain, which are obtained from velocity and density measurements, were used to estimate the dissipation rate of turbulent kinetic energy and the diapycnal eddy diffusivity from a fine-scale parameterisation. Estimates are calculated by parameterising internal wave-wave interactions and assuming that wave breaking modulates turbulent mixing. A detailed description of the method for calculating diffusivity from LADCP and CTD can be found in Kunze et al. (2006). Two datasets with different vertical resolutions were produced: one in which the shear is integrated from 150 to 300 m and the strain over 20-150 m, and one in which the shear is integrated from 70 to 200 m and the strain over 30-200 m. Nutrients (nitrate, phosphate, silicate) were determined via colourimetric analysis (see cruise report, Giering and Sanders, 2019), POC was determined as described in Giering et al. (2023), DOC and DOC flux were determined as described in Lovecchio et al. (2023), NPP was determined as described in Poulton et al. (2019), and ambient leucine assimilation and bacterial cell count were determined as described in Rayne et al. (2024). Bacterial abundance and leucine assimilation were made from bottle samples of six CTD casts of the stainless-steel rosette. Water was collected at six depths (6 m, deep-chlorophyll maximum, mixed layer depth + 10, 100, 250 and 500 m). Acid-cleaned HDPE carboys and tubing were used for sampling. Samples were then stored in the dark and at in-situ temperature prior to on-board laboratory sample preparation or analysis. Flow cytometry was used to measure bacterial abundance. Room temperature paraformaldehyde was used to fix 1.6 ml samples for 30 minutes. Then, using liquid nitrogen, the samples were flash frozen and stored at -80°C. Samples were then defrosted before being stained using SYBR Green I and run through the flow cytometer (BD FACSort™). The method of Hill et al. (2013) was applied to determine prokaryotic leucine assimilation using L-[4,5-³H] leucine which has a specific activity of 89.3 Ci/mmol­. In the mixed and upper layers of the water column, the protocol in Zubkov et al. (2007) was followed. Below the mixed layer, adaptions to the method included reducing the concentration of ³H-Leucine to 0.005, 0.01, 0.025, 0.04 and 0.05 nM; increasing experimental volumes to 30 ml; enhancing incubation times to 30, 60, 90 and 120 min. These adaptions were made to improve accuracy where lower rates of leucine assimilation were expected. Data were provided by the British Oceanographic Data Centre and funded by the National Environment Research Council.

Description: The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.5 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.4 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This living data publication documents changes in the methods and data sets used in this new version of the SOCAT data collection compared with previous publications of this data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014).

Description: The Surface Ocean CO2 Atlas (SOCAT) is a synthesis activity by the international marine carbon research community (〉100 contributors). SOCAT version 4 has 18.5 million quality-controlled, surface ocean fCO2 (fugacity of carbon dioxide) observations with an accuracy of better than 5 µatm from 1957 to 2015 for the global oceans and coastal seas. Automation of data upload and initial data checks speeds up data submission and allows annual releases of SOCAT from version 4 onwards. SOCAT enables quantification of the ocean carbon sink and ocean acidification and evaluation of ocean biogeochemical models. SOCAT represents a milestone in research coordination, data access, biogeochemical and climate research and in informing policy.

Description: The evolution of productivity, redox conditions, temperature, and ventilation during the deposition of an Aegean sapropel (S1) is independently constrained using bulk sediment composition and high-resolution single specimen benthic foraminiferal trace metal and stable isotope data. The occurrence of benthic foraminifer, Hoeglundina elegans (H. elegans), through a shallow water (260 m) sapropel, permits for the first time a comparison between dissolved and particulate concentrations of Ba and Mn and the construction of a Mg/Ca-based temperature record through sapropel S1. The simultaneous increase in sedimentary Ba and incorporated Ba in foraminiferal test carbonate, (Ba/Ca)H. elegans, points to a close coupling between Ba cycling and export productivity. During sapropel deposition, sedimentary Mn content ((Mn/Al)sed) is reduced, corresponding to enhanced Mn2+ mobilization from sedimentary Mn oxides under suboxic conditions. The consequently elevated dissolved Mn2+ concentrations are reflected in enhanced (Mn/Ca)H. elegans levels. The magnitude and duration of the sapropel interruption and other short-term cooling events are constrained using Mg/Ca thermometry. Based on integrating productivity and ventilation records with the temperature record, we propose a two-mode hysteresis model for sapropel formation.

Description: The MAREDAT atlas covers 11 types of plankton, ranging in size from bacteria to jellyfish. Together, these plankton groups determine the health and productivity of the global ocean and play a vital role in the global carbon cycle. Working within a uniform and consistent spatial and depth grid (map) of the global ocean, the researchers compiled thousands and tens of thousands of data points to identify regions of plankton abundance and scarcity as well as areas of data abundance and scarcity. At many of the grid points, the MAREDAT team accomplished the difficult conversion from abundance (numbers of organisms) to biomass (carbon mass of organisms). The MAREDAT atlas provides an unprecedented global data set for ecological and biochemical analysis and modeling as well as a clear mandate for compiling additional existing data and for focusing future data gathering efforts on key groups in key areas of the ocean. This is a gridded data product about diazotrophic organisms . There are 6 variables. Each variable is gridded on a dimension of 360 (longitude) * 180 (latitude) * 33 (depth) * 12 (month). The first group of 3 variables are: (1) number of biomass observations, (2) biomass, and (3) special nifH-gene-based biomass. The second group of 3 variables is same as the first group except that it only grids non-zero data. We have constructed a database on diazotrophic organisms in the global pelagic upper ocean by compiling more than 11,000 direct field measurements including 3 sub-databases: (1) nitrogen fixation rates, (2) cyanobacterial diazotroph abundances from cell counts and (3) cyanobacterial diazotroph abundances from qPCR assays targeting nifH genes. Biomass conversion factors are estimated based on cell sizes to convert abundance data to diazotrophic biomass. Data are assigned to 3 groups including Trichodesmium, unicellular diazotrophic cyanobacteria (group A, B and C when applicable) and heterocystous cyanobacteria (Richelia and Calothrix). Total nitrogen fixation rates and diazotrophic biomass are calculated by summing the values from all the groups. Some of nitrogen fixation rates are whole seawater measurements and are used as total nitrogen fixation rates. Both volumetric and depth-integrated values were reported. Depth-integrated values are also calculated for those vertical profiles with values at 3 or more depths.