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Chemical Oceanography

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  • This dataset contains the traditional and effective nitrate, phosphate, and silicate fluxes in Lombok, Ombai, and Timor passages, Indian Ocean. Fluxes are depth-resolved and cross-strait integrated, for the 2004-2006 time period of the INSTANT field program. In some cases depths extend below the functional sill depths, due to the moorings being in deeper water. Negative fluxes are westward, towards the Indian Ocean. Files are in self-describing netCDF format, as follows: (1) lombok_trad.nc. Traditional nutrient fluxes for Lombok Strait. (2) lombok_eff.nc. Effective nutrient fluxes for Lombok Strait. (3) ombai_trad.nc. Traditional nutrient fluxes for Ombai Strait. (4) ombai_eff.nc. Effective nutrient fluxes for Ombai Strait. (5) timor_trad.nc. Traditional nutrient fluxes for Timor Passage. (6) timor_eff.nc. Effective nutrient fluxes for Timor Passage.

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    Secchi disk data collected by students on the RV Investigator training voyage (Transit IN2018_T01).

  • We compare the formulation and emergent dynamics of 11 CMIP6 IPCC marine biogeochemical models. We find that the largest source of uncertainty across model simulations of marine carbon cycling is grazing pressure (i.e. the phytoplankton specific loss rate to grazing). Variability in grazing pressure is driven by large differences in zooplankton specific grazing rates, which are not sufficiently compensated for by offsetting differences in zooplankton specific mortality rates. Models instead must tune the turnover rate of the phytoplankton population to balance large differences in top-down grazing pressure and constrain net primary production. We then run a controlled sensitivity experiment in a global, coupled ocean-biogeochemistry model to test the sensitivity of marine carbon cycling to this uncertainty and find that even when tuned to identical net primary production, export and secondary production remain extremely sensitive to grazing, likely biasing predictions of future climate states and food security.

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    Trace element data collected from 18 stations near the Mertz Glacier on the 2019 ENRICH voyage. Sea water was collected using a 12-bottle trace metal rosette (TMR) and acidified for analysis back in Hobart. Samples were measured using an offline seaFAST pre-concentration system and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) at the University of Tasmania. This data contributed to Smith et al., Circumpolar Deep Water and shelf sediments support late summer microbial iron remineralisation in Global Biogeochemical Cycles (2021).

  • An increasing number of studies are considering Fe and ligand concentrations, providing data of trace element availability across the remote Southern Ocean region (Ardiningsih et al., 2021, Gerringa et al., 2020, Hassler et al., 2017, Thuroczy et al., 2012, Thuroczy et al., 2011, Caprara et al., 2016 and references therein). However, studies seldom focus on polar coastal environments which are especially sensitive to climate-induced changes. To anticipate how these changes may impact Fe availability, we must first understand the drivers of ligand supply to the Antarctic coast and offshore. The newly compiled Southern Ocean Ligand (SOLt) Collection includes all publicly available Fe complexation datasets for the Southern Ocean including dissolved Fe concentrations, Fe-binding ligand concentrations, and complexation capacities for 25 studies between 1995 - 2019.

  • Biological ocean data collected from ships find reuse in aggregations of historical data. These data are heavily relied upon to document long term change, validate satellite algorithms for ocean biology and are useful in assessing the performance of autonomous platforms and biogeochemical models. There is a need to combine subsurface biological and physical data into one aggregate data product to support reproducible research. Existing aggregate products are dissimilar in source data, have largely been isolated to the surface ocean and most omit physical data. These products cannot easily be used to explore subsurface bio-physical relationships. We present the first version of a biological ocean data reformatting effort (BIO-MATE, https://gitlab.com/KBaldry/BIO-MATE). BIO-MATE uses R software that reformats openly sourced published datasets from oceanographic voyages. These reformatted biological and physical data from underway sensors, profiling sensors and pigments analysis are stored in an interoperable and reproducible BIO-MATE data product for easy access and use.

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    Here, we hypothesize that Fe uptake rates by sea-ice algae and under-ice phytoplankton are higher than the rates reported for open ocean phytoplankton in the SO. We performed 55Fe and carbon (14C) short-term uptake field measurements in, on and under Antarctic sea ice. We collected under ice seawater, melted snow and sea-ice cores. We then spiked them with 14C or 55Fe radiotracers to measure Fe and C uptake rates by sea-ice algae. Samples were then filtered, and residual radioactivity on the filters measured liquid scintillation counter (Packard).

  • Data collected from Southern Ocean phytoplankton laboratory culture experiments to examine the effect of iron limitation on the Chlorophyll fluorescence (F) to chlorophyll (Chl) ratio. Irradiance levels at which cultures were grown are indicated by the photon flux density (PFD). Growth rates of Fe limited cultures (-Fe) relative to Fe replete cultures (+Fe) are referred to as μ / μmax (unitless).

  • The effect of ocean alkalinity enhancement on a coastal phytoplankton community was assessed via a microcosm experiment. The effect of alkalinity enhancement in two scenarios (i) when enclosed seawater was in equilibrium with atmospheric CO2 and (ii) when enclosed seawater was not in equilibrium with atmospheric CO2 were explored. Alkalinity was increased by ~497 umol/kg in these two treatments and plankton communities, carbonate chemistry, dissolved inorganic nutrients, particulate matter and chlorophyll a dynamics monitored over a 22 day period where a spring bloom occurred.

  • During the RV Investigator Eddy voyage (IN2016_V02), we sampled a mesoscale cyclonic and anticyclonic eddy in the Southern Ocean south to Tasmania. We have collected water samples to analyse concentration of phytoplankton biomass and nutrients.