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This dataset contains relative abundance (%) of diatom species, and includes the Eucampia antarctica terminal/intercalary valve ratio (Eucampia index), biogenic silica and Si/Al values from core TAN1302-44, which was collected from the WEGA channel on the continental slope, offshore Adélie Land, East Antarctica. Diatoms were analysed at 10 cm, resolution within interval 350-5 cm-depth, while biogenic silica was analysed every 20 cm, and Si/Al (X-ray Flourescence scanning, XRF) comprises a 3-point average, from every 0.2 cm, of entire core. The data also includes four radiocarbon dates, calculated from 0 cm, 25 cm, 35 cm and 45 cm- depths; Shannon-Wiener biodiversity index based on all species identified, and principal component analysis based on species identified at >1.8% relative abundance (in at least two samples). The main purpose of this dataset compilation was to understand the distribution of species, and species assemblages. The interpretation of the data sets suggests changes in Antarctic sea ice and ocean circulation occured near the ice sheet, over the last glacial cycle. These changes are especially evident in the last glacial, and during the last deglacial (warming).

This data set contains the age model and air-sea CO2 exchange tracer ([CO32-]as) of deep water core NEAP 4K and Intermediate water core GGC90. Seawater [CO32-]as is calculated following the approach in Yu et al. (2019). The Seawater [CO32-]as reconstructions at GGC90 are obtained based on [CO32-] and [PO43-] from Lacerra et al. (2019) and Umling et al. (2019), but these data have not yet been used to infer air-sea CO2 exchange histories. Importantly, building upon previous work (Lund et al., 2015), 23 new radiocarbon dates substantially improve the GGC90 age model. We present new deep-water [CO32-] and [PO43-] reconstructions at NEAP 4K using benthic foraminiferal B/Ca and Cd/Ca, respectively. The age model for NEAP 4K is based on 4 new and 13 published radiocarbon dates (Hall et al., 2004) and new Neogloboquadrina pachyderma (sinistral) coiling ratios. Based on the novel approach to reconstruct upper Atlantic air-sea CO2 exchange signatures, we provide evidence for a net release of CO2 via the Atlantic sector of the Southern Ocean, which contributes to the millennial atmospheric CO2 rise during Heinrich Stadial 1.

This dataset includes orbital-resolution benthic foraminiferal (Cibicidoides wuellerstorfi) δ18O and δ13C measurements, a new orbitally tuned age model, millennial-resolution XRF scanning elemental data, and a discrete XRF calibration sample set measured by ICP-MS - all from IODP Site U1443 (Expedition 353) in the equatorial Indian ocean spanning the late Miocene interval 9-5 Ma.

Longitudinal monthly surveys were performed on eleven occasions from July 2017 to June 2018. A total of 66 samples were collected over a total period of 12 months. Water parameters, nutrient, and gas samples were taken approximately every month (excluding September 2017) from the upper water column at 6 sites along the creek salinity gradient at low tide, from the estuary's mouth, and to the upper freshwater creek. A calibrated YSI EC300A was used to measure salinity (±0.02), whilst a calibrated Hach HQ40D measured DO (±0.2 mg/L) and water temperature (±0.10°C). Nutrient samples (including duplicates), filtered and unfiltered, were collected with a sample-rinsed 60 mL polyethylene syringe. Samples for dissolved organic carbon (DOC) analysis were filtered using pre-combusted 0.7 µm GF/F filters (Whatman), into 40 mL borosilicate vials (USP Type I). Samples for nitrogen were immediately filtered using Satourious ™ 0.45μm cellulose acetate syringe filters into 10 mL polyethylene sample tubes. All samples were kept in a cold icebox, away from light, for less than 5 hours and then frozen until laboratory analysis. Nutrient analysis of DOC was performed with the 40 mL borosilicate vials (USP Type I) first treated with 30 µL of H3PO4 before analysis using an Aurora 1030W TOC Analyser (Thermo Fisher Scientific, ConFLo IV). Nutrient analysis of ammonium (NH4+), NOx (nitrate plus nitrite), and total dissolved nitrogen (TDN) was performed on the 10 mL polyethylene sample tubes colourimetrically using a Lachat Flow Injection Analyser. N2O samples were obtained directly from the creek with two replicate 250 mL borosilicate bottles, filled from 20 cm below the surface, ensuring zero headspace, and then immediately treated with 200 µL of HgCl2 solution and capped. The borosilicate bottles were taken to the laboratory for gas extraction where the bottle was inverted to add 60 mL of zero-air (of known N2O concentration) headspace using a needlepoint syringe while simultaneously extracting 60 mL of sample, before being shaken for 4 minutes. Next, 60 mL of gas was extracted from the bottle, while 60 mL of sample was replaced. The subsequently extracted gas was transferred to a gasbag and diluted with 200 mL of known N2O concentration zero-air ready for analysis. The gasbags were analysed using cavity ringdown spectroscopy on a calibrated Picarro G2308. The same measurements of water parameters of temperature, dissolved oxygen and salinity and nutrient samples of dissolved organic carbon, filtered and unfiltered nitrogen and nitrous oxide were collected through time series apparatus, hourly and 3 hourly, over 185 hours and exclusively at one site in the lower estuary (Site 1). A calibrated Hydrolab MS5 sonde measured and logged water temperature (±0.02°C), DO (±0.2 mg/L), and salinity (±0.02) at 30 m intervals and a depth logger (CTD diver) measured water depth in 15-minute intervals. Nutrient samples were collected and analysed as in the longitudinal monthly surveys. N2O samples were collected from a time series gas equilibration device via a one-way valve into 150 mL syringes then transferred from the syringes into a Supelco company 1 L gasbag. A total of 800 mL of gas was taken per sample. The gasbags were analysed for N2O using cavity ringdown spectroscopy on a calibrated Picarro G2308. Total dissolved nitrogen and dissolved inorganic nitrogen were calculated from the nitrogen samples.

The extracellular concentration of H2O2 in surface aquatic environments is controlled by a balance between photochemical production and the microbial synthesis of catalase and peroxidase enzymes to remove H2O2 from solution. In any kind of incubation experiment, the formation rates and equilibrium concentrations of reactive oxygen species (ROSs) such as H2O2 may be sensitive to both the experiment design, particularly to the regulation of incident light, and the abundance of different microbial groups, as both cellular H2O2 production and catalase–peroxidase enzyme production rates differ between species. Whilst there are extensive measurements of photochemical H2O2 formation rates and the distribution of H2O2 in the marine environment, it is poorly constrained how different microbial groups affect extracellular H2O2 concentrations, how comparable extracellular H2O2 concentrations within large-scale incubation experiments are to those observed in the surface-mixed layer, and to what extent a mismatch with environmentally relevant concentrations of ROS in incubations could influence biological processes differently to what would be observed in nature. Here we show that both experiment design and bacterial abundance consistently exert control on extracellular H2O2 concentrations across a range of incubation experiments in diverse marine environments. During four large-scale (>1000 L) mesocosm experiments (in Gran Canaria, the Mediterranean, Patagonia and Svalbard) most experimental factors appeared to exert only minor, or no, direct effect on H2O2 concentrations. For example, in three of four experiments where pH was manipulated to 0.4–0.5 below ambient pH, no significant change was evident in extracellular H2O2 concentrations relative to controls. An influence was sometimes inferred from zooplankton density, but not consistently between different incubation experiments, and no change in H2O2 was evident in controlled experiments using different densities of the copepod Calanus finmarchicus grazing on the diatom Skeletonema costatum (<1 % change in [H2O2] comparing copepod densities from 1 to 10 L−1). Instead, the changes in H2O2 concentration contrasting high- and low-zooplankton incubations appeared to arise from the resulting changes in bacterial activity. The correlation between bacterial abundance and extracellular H2O2 was stronger in some incubations than others (R2 range 0.09 to 0.55), yet high bacterial densities were consistently associated with low H2O2. Nonetheless, the main control on H2O2 concentrations during incubation experiments relative to those in ambient, unenclosed waters was the regulation of incident light. In an open (lidless) mesocosm experiment in Gran Canaria, H2O2 was persistently elevated (2–6-fold) above ambient concentrations; whereas using closed high-density polyethylene mesocosms in Crete, Svalbard and Patagonia H2O2 within incubations was always reduced (median 10 %–90 %) relative to ambient waters.

The archived data presented here are derived from analytical measurements performed on ocean sediments from cores drilled off the Iberian Margin and speleothems collected from Corchia Cave (Italy). The time span is 970 to 810 ka. A full description of the sample preparation procedures and analytical methods is contained in the Supplementary Material of the article. The ocean coring sites are IODP Site U1385 and Site U1387. From Site U1385 for this study, we measured: the oxygen isotope ratios on planktic (Globigerina bulloides) and benthic (Cibicidoides weullerstorfi) foraminfera at 2 cm resolution. The alkenone C37:4 biomarker data from the same site were taken from Rodrigues et al. (2017). From Site U1387 for this study, we measured: the oxygen isotope ratios on planktic foraminifera (Globigerina bulloides) and alkenone biomarkers for calculating the index Uk'37 , a proxy for sea-surface temperatures. Data from U1387 were placed onto the U1385 depth scale by synchronising the planktic oxygen isotope series. All measurements were made using standard analytical methods following the preparation procedures outlined in the Supplementary Materials of Bajo et al. (2020). The data for Corchia Cave were from four stalagmites and one subaqueous speleothem. Stable oxygen and carbon isotopes were measured on all speleothems. For the four stalagmites, sampling was conducted at 1 mm resolution. For stalagmite CC8, which covers the longest time interval, the sampling resolution was increased to 250 μm through termination X and XII. For the subaqueous speleothem (CD3), oxygen and carbon isotopes were measured on samples milled at 200 μm increments. The speleothem chronology was based on U-Pb radiometric ages from the four stalagmites. The individual time series were stacked into a single time series utilising all of the U-Pb ages. Analytical methods are described in detail in the Supplementary Materials of Bajo et al. (2020). The ocean and speleothem data were combined in order to place the ocean proxy series onto a radiometric time scale. This was achieved by synchronising the planktic G. bulloides oxygen isotope series to the speleothem oxygen isotope series. The principal purpose was to determine the timing of terminations X and XII and compare these ages with the astronomical template.

Although it has been demonstrated that the speed and magnitude of the recent Arctic sea ice decline is unprecedented for the past 1450 years, few records are available to provide a paleoclimate context for Arctic sea ice extent. Bromine enrichment in ice cores has been suggested to indicate the extent of newly formed sea ice areas. Despite the similarities among sea ice indicators and ice core bromine enrichment records, uncertainties still exist regarding the quantitative linkages between bromine reactive chemistry and the first-year sea ice surfaces. Here we present a 120 000-year record of bromine enrichment from the RECAP (REnland ice CAP) ice core, coastal east Greenland, and interpret it as a record of first-year sea ice. We compare it to existing sea ice records from marine cores and tentatively reconstruct past sea ice conditions in the North Atlantic as far north as the Fram Strait (50–85∘ N). Our interpretation implies that during the last deglaciation, the transition from multi-year to first-year sea ice started at ∼17.5 ka, synchronously with sea ice reductions observed in the eastern Nordic Seas and with the increase in North Atlantic ocean temperature. First-year sea ice reached its maximum at 12.4–11.8 ka during the Younger Dryas, after which open-water conditions started to dominate, consistent with sea ice records from the eastern Nordic Seas and the North Icelandic shelf. Our results show that over the last 120 000 years, multi-year sea ice extent was greatest during Marine Isotope Stage (MIS) 2 and possibly during MIS 4, with more extended first-year sea ice during MIS 3 and MIS 5. Sea ice extent during the Holocene (MIS 1) has been less than at any time in the last 120 000 years.

Bottom trawling in the deep sea is one of the main drivers of sediment resuspension, eroding the seafloor and altering the content and composition of sedimentary organic matter (OM). The physical and biogeochemical impacts of bottom trawling were studied on the continental slope of the Gulf of Castellammare, Sicily (southwestern Mediterranean), through the analysis of two triplicate sediment cores collected at trawled and untrawled sites (∼550 m water depth) during the summer of 2016. Geochemical and sedimentological parameters (excess 210Pb, excess 234Th, 137Cs, dry bulk density, and grain size), elemental (organic carbon and nitrogen) and biochemical composition of sedimentary OM (proteins, carbohydrates, lipids), as well as its freshness (phytopigments) and degradation rates were determined in both coring locations. The untrawled site had a sedimentation rate of 0.15 cm yr−1 and presented a 6 cm thick surface mixed layer that contained siltier sediment with low excess 210Pb concentrations, possibly resulting from the resuspension, posterior advection, and eventual deposition of coarser and older sediment from adjacent trawling grounds. In contrast, the trawled site was eroded and presented compacted century-old sediment highly depleted in OM components, which were between 20 % and 60 % lower than those in the untrawled site. However, the upper 2 cm of the trawled site consisted of recently accumulated sediments enriched in excess 234Th, excess 210Pb, and phytopigments, while OM contents were similar to those from the untrawled core. This fresh sediment supported protein turnover rates of 0.025 d−1, which doubled those quantified in surface sediments of the untrawled site. The enhancement of remineralization rates in surface sediment of the trawled site was associated with the arrival of fresh particles on a chronically trawled deep-sea region that is generally deprived of OM. We conclude that the detrimental effects of bottom trawling can be temporarily and partially abated by the arrival of fresh and nutritionally rich OM, which stimulate the response of benthic communities. However, these ephemeral deposits are likely to be swiftly eroded due to the high trawling frequency over fishing grounds, highlighting the importance of establishing science-based management strategies to mitigate the impacts of bottom trawling.

We present a Lagrangian convective transport scheme developed for global chemistry and transport models, which considers the variable residence time that an air parcel spends in convection. This is particularly important for accurately simulating the tropospheric chemistry of short-lived species, e.g., for determining the time available for heterogeneous chemical processes on the surface of cloud droplets. In current Lagrangian convective transport schemes air parcels are stochastically redistributed within a fixed time step according to estimated probabilities for convective entrainment as well as the altitude of detrainment. We introduce a new scheme that extends this approach by modeling the variable time that an air parcel spends in convection by estimating vertical updraft velocities. Vertical updraft velocities are obtained by combining convective mass fluxes from meteorological analysis data with a parameterization of convective area fraction profiles. We implement two different parameterizations: a parameterization using an observed constant convective area fraction profile and a parameterization that uses randomly drawn profiles to allow for variability. Our scheme is driven by convective mass fluxes and detrainment rates that originate from an external convective parameterization, which can be obtained from meteorological analysis data or from general circulation models. We study the effect of allowing for a variable time that an air parcel spends in convection by performing simulations in which our scheme is implemented into the trajectory module of the ATLAS chemistry and transport model and is driven by the ECMWF ERA-Interim reanalysis data. In particular, we show that the redistribution of air parcels in our scheme conserves the vertical mass distribution and that the scheme is able to reproduce the convective mass fluxes and detrainment rates of ERA-Interim. We further show that the estimated vertical updraft velocities of our scheme are able to reproduce wind profiler measurements performed in Darwin, Australia, for velocities larger than 0.6 m s−1. SO2 is used as an example to show that there is a significant effect on species mixing ratios when modeling the time spent in convective updrafts compared to a redistribution of air parcels in a fixed time step. Furthermore, we perform long-time global trajectory simulations of radon-222 and compare with aircraft measurements of radon activity.

The paper investigates the wintertime dynamics of the coastal northeastern Adriatic Sea and is based on numerical modelling and in situ data collected through field campaigns executed during the winter and spring of 2015. The data were collected with a variety of instruments and platforms (acoustic Doppler current profilers, conductivity–temperature–depth probes, glider, profiling float) and are accompanied by the atmosphere–ocean ALADIN/ROMS modelling system. The research focused on the dense-water formation (DWF), thermal changes, circulation, and water exchange between the coastal and open Adriatic. According to both observations and modelling results, dense waters are formed in the northeastern coastal Adriatic during cold bora outbreaks. However, the dense water formed in this coastal region has lower densities than the dense water formed in the open Adriatic due to lower salinities. Since the coastal area is deeper than the open Adriatic, the observations indicate (i) balanced inward–outward exchange at the deep connecting channels of denser waters coming from the open Adriatic DWF site and less-dense waters coming from the coastal region and (ii) outward flow of less-dense waters dominating in the intermediate and surface layers. The latter phenomenon was confirmed by the model, even if it significantly underestimates the currents and transports in the connecting channels. The median residence time of the coastal area is estimated to be approximately 20 days, indicating that the coastal area may be renewed relatively quickly by the open Adriatic waters. The data that were obtained represent a comprehensive marine dataset that can be used to calibrate atmospheric and oceanic numerical models and point to several interesting phenomena to be investigated in the future.