Carbon dynamics of the Weddell Gyre, Southern Ocean

The accumulation of carbon within the Weddell Gyre and its exchanges across the gyre boundaries are investigated with three recent full-depth oceanographic sections enclosing this climatically important region. The combination of carbonmeasurements with ocean circulation transport estimates from a box inverse analysis reveals that deepwater transports associated with Warm Deep Water (WDW) and Weddell Sea Deep Water dominate the gyre’s carbon budget, while a dual-cell vertical overturning circulation leads to both upwelling and the delivery of large quantities of carbon to the deep ocean. Historical sea surface pCO2 observations, interpolated using a neural network technique, confirm the net summertime sink of 0.044 to 0.058 ± 0.010 Pg C / yr derived from the inversion. However, a wintertime outgassing signal similar in size results in a statistically insignificant annual air-to-sea CO2 flux of 0.002± 0.007 Pg C / yr (mean 1998–2011) to 0.012 ± 0.024 Pg C/ yr (mean 2008–2010) to be diagnosed for the Weddell Gyre. A surface layer carbon balance, independently derived fromin situ biogeochemical measurements, reveals that freshwater inputs and biological drawdown decrease surface ocean inorganic carbon levels more than they are increased by WDW entrainment, resulting in an estimated annual carbon sink of 0.033 ± 0.021 Pg C / yr. Although relatively less efficient for carbon uptake than the global oceans, the summertime Weddell Gyre suppresses the winter outgassing signal, while its biological pump and deepwater formation act as key conduits for transporting natural and anthropogenic carbon to the deep ocean where they can reside for long time scales

Nutrient measurements from POLARSTERN cruise PS114 (LTER HAUSGARTEN)

Dissolved inorganic nutrients measured during the Polarstern Expedition PS11410, which took place from July to 3 August 2018. Further information concerning the analysis is presented in the accompanying report

Nutrient measurements from POLARSTERN cruise PS99.2 to Fram Strait (LTER HAUSGARTEN)

This is a quality controlled revision of nutrient (nitrate plus nitrite, nitrite, phosphate, silicate and ammonium) measurements carried out during expedition PS99.2 aboard RV Polarstern (24 June 2016 - 16 July 2016) as part of the LTER HAUSGARTEN. It had not been previously been submitted to PANGAEA because at the time of analyses, problems were encountered with the instrumentation used. After an exhaustive quality controlled assessment of the data, here we are now providing a revised version, where data has been quality flagged

Revision of nutrient data from Polarstern expedition PS101 (ARK-XXX/3)

This is a revision (quality assessment) of nutrient data measured onboard the RV Polarstern during expedition PS101 (9 September - 23 October 2016). A brief report is attached, which provides a summary of what the revision entailed

Dissolved oxygen of seawater samples during RV POLARSTERN expedition PS122 – MOSAiC

Discrete seawater samples for total dissolved oxygen were collected from the Polarstern (vessel:polarstern:ctd_sbe9plus_321) and Ocean City (vessel:polarstern:ctd_sbe9plus_935) CTD/Rosette systems during the Multidisciplinary drifting observatory for the study of Arctic Climate (MOSAiC) expedition, 20 September 2019 – 14 October 2020. Dissolved oxygen was analyzed on board RV Polarstern during legs 3, 4, and 5 between 6 March 2020 and 17 September 2020. Seawater was drawn from Niskin bottles into Winkler flasks using silicon tubing, filling from the bottom and allowing seawater to overflow by at least two flask volumes (approximately 120 mL). The samples were directly pickled by the addition of 1 mL each of concentrated manganese chloride (3 M) and alkaline (NaOH 8 M) sodium iodide (4 M) solutions to form manganese oxyhydrodoxide precipitate. Samples were stored in the dark and underwater at room temperature until analysis. Dissolved oxygen was determined using an automatic Winkler titration setup with potentiometric detection (Titrino plus 848, Metrohm, Switzerland). Reagents were prepared according to Langdon (2010). Blanks were determined before each run by addition of reagents to MilliQ water. The titrations were performed directly in the flasks used for sampling after the manganese oxyhydroxide precipitate was dissolved by addition of sulphuric acid (5 M). Sodium thiosulphate (~0.2 N) solutions were prepared onboard for the titration and the concentration was determined before each run using an iodate standard (0.01 N, OSIL, United Kingdom). The analytical precision based on duplicate samples analysis was 0.4 ± 2.6 µmol kg-1 (n = 60)

Amino acid and carbohydrate patterns across Fram Strait during POLARSTERN cruise PS107

Amino acids (AA) and carbohydrates (CHO) are produced by phytoplankton as part of the particulate organic carbon (POC) fraction, and can subsequently be released into the dissolved organic carbon (DOC) pool serving as food for heterotrophs. We investigated changes in quantity and quality of POC and DOC, individual AA and individual CHO across Fram Strait in summer 2017. We evaluate the organic matter processing and show that AA and CHO composition substantially differs between the particulate and dissolved fractions. The particulate fraction was enriched in essential AA and the CHO galactose, xylose/mannose, and muramic acid. In the dissolved fraction non-essential AA, several neutral CHO, and acidic and amino CHO were enriched. Our results are important for the future when changing conditions in the Central Arctic Ocean (Atlantification, warming, decreasing ice concentrations) may increase primary production and consequently degradation. The AA and CHO signatures left behind could be used as tracers after the fact to infer changes in microbial loop processes and food web interactions

Compilation of downward flux observations from sediment trap deployments in the Atlantic Ocean - Contribution to EURO-BASIN's Data integration

We provide a compilation of downward fluxes (total mass, POC, PON, BSiO2, CaCO3, PIC and lithogenic/terrigenous fluxes) from over 6000 sediment trap measurements distributed in the Atlantic Ocean, from 30 degree North to 49 degree South, and covering the period 1982-2011. Data from the Mediterranean Sea are also included. Data were compiled from different sources: data repositories (BCO-DMO, PANGAEA), time series sites (BATS, CARIACO), published scientific papers and/or personal communications from PI's. All sources are specifed in the data set. Data from the World Ocean Atlas 2009 were extracted to provide each flux observation with contextual environmental data, such as temperature, salinity, oxygen (concentration, AOU and percentage saturation), nitrate, phosphate and silicate

R/V Sikuliaq 19S Expedition to the Arctic Ocean: Nutrient Data

Here we present dissolved nutrient data collected during Expedition 19S to the Arctic Ocean during September 2018 on board the R/V Sikuliaq, a research vessel operated by the University of Alaska. Data were generated within the framework of the NERC-BMBF Changing Arctic Ocean programme; project Primary productivity driven by escalating Arctic nutrient fluxes? (PEANUTS) in collaboration with the US Office of Naval Research Stratified Ocean Dynamics of the Arctic programme (SODA). A report is included, which provides further details about the data, funding agencies and research for which these data has been used