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) Traditional nutrient fluxes for Lombok Strait. (2) Effective nutrient fluxes for Lombok Strait. (3) Traditional nutrient fluxes for Ombai Strait. (4) Effective nutrient fluxes for Ombai Strait. (5) Traditional nutrient fluxes for Timor Passage. (6) Effective nutrient fluxes for Timor Passage.

  • 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.

  • 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).

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

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    This repository contains data files (netCDF format) related to the model configuration developed and used by Joan Llort between 2011 and 2019. The model is a 1D configuration based on PISCES v1 and the specific routines and namelist are here: The data in this repository is organised in two groups: - The first group contains the forcing files used to create and idealised representation of Southern Ocean water columns. Forcing files were automatically modified to force PISCES models with different mixed layer depth and iron environments. The files presented here are for a single water column but they can be modified using the python routines in the GitHub link above. - The second group contains the outputs for one of the experiments. We studied the impact of changes in ferricilne, winter mixed layer and summer mixed layer depths over Southern Ocean primary production.

  • 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.

  • 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).

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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).

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    These data are from a piggy back voyage to IN2018_V05, October-November 2018. The Chief Scientists were Helen Phillips and Nathan Bindoff. Nic Pittman and Clara Vives collected biogeochemical data on the voyage, and Xiang Yang used these data in his Hons thesis 2020-2021. The purpose of the study was to investigate biogeochemical variability in the region of the Polar Front meander south of Tasmania. Data include CTD nutrients, chlorophyll and oxygen as well as underway phytoplankton physiology and pCO2. Some data are duplicated but not in exactly the same format on the CSIRO Data Trawler.