Carbon cycling dynamics in the seasonal sea-ice zone of East Antarctica

Roden, Nicholas; Tilbrook, Bronte; Trull, Thomas W.; Virtue, Patti; Williams, Guy D.

doi:10.1002/2016jc012008

Cited by 24 publications

(45 citation statements)

References 119 publications

(129 reference statements)

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“…Similarly, surface TA values ranged between 2,303 and 2,314 μmol/kg in the central DP, with a similar feature of minimum values of ~2,276 μmol/kg found in the northern DP. Subsurface parameters converge at a depth of approximately 150 m to an average TCO 2 concentration of 2,214 ± 3 μmol/kg and TA concentration of 2,315 ± 2 μmol/kg in WW (Figures a and b), similar to other observations made in shelf waters in the East Antarctic (Table ; Shadwick et al, ; Roden et al, ).…”

Section: Resultssupporting

confidence: 85%

“…The mean concentration of dissolved oxygen (~341 μmol/kg) in AASW was greater than values found elsewhere in East Antarctica (Roden et al, 2016;Shadwick et al, 2014), with concentrations more comparable to saturated conditions (~350-360 μmol/kg) though similar surface temperature and salinity was observed ( Table 2). The percent saturation of dissolved oxygen at the sea surface was greatest (>99%) in the central, open waters of the Dalton Polynya (Figure 3d) and decreased toward and along the outer edges of the polynya and near the TIS (Figure 4d).…”

Section: 1029/2018jc014882mentioning

confidence: 62%

“…Wintertime TCO 2 concentration in surface waters is often estimated using the value at the temperature minimum (e.g., Bates et al, ; Roden et al, ). However, on the Antarctic shelf, the temperature minimum is not well defined, for example in the areas in front of the MUIS where ISW is present (Silvano et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…In these regions, strong ocean currents and/or katabatic winds push newly formed sea ice away to sustain areas of open water or thin ice for much of the year (Massom et al, ; Morales Maqueda et al, ). There is a growing understanding of the interactive physical and biological processes impacting CO 2 system dynamics in seasonally sea ice‐covered regions such as the East Antarctic (Roden et al, ; Shadwick et al, ), the West Antarctic Peninsula (Jones et al, ; Legge et al, ), and the Amundsen (Mu et al, ; Yager et al, ) and Ross Seas (DeJong et al, ; DeJong & Dunbar, ). In the spring and summer, coastal polynyas often support intense biological activity relative to their small surface areas as reduced sea ice coverage exposes surface waters to incoming solar radiation (Arrigo & van Dijken, ), driving a dramatic undersaturation in CO 2 at the ocean surface.…”

Section: Introductionmentioning

confidence: 99%

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Summer Carbonate Chemistry in the Dalton Polynya, East Antarctica

Arroyo¹,

Shadwick

Tilbrook

2019

JGR Oceans

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The carbonate chemistry in the Dalton Polynya in East Antarctica (115°–123°E) was investigated in summer 2014/2015 using high‐frequency underway measurements of CO2 fugacity (fCO2) and discrete water column measurements of total dissolved inorganic carbon (TCO2) and total alkalinity. Air‐sea CO2 fluxes indicate this region was a weak net source of CO2 to the atmosphere (0.7 ± 0.9 mmol C m−2 day−1) during the period of observation, with the largest degree of surface water supersaturation (ΔfCO2 = +45 μatm) in ice‐covered waters near the Totten Ice Shelf (TIS) as compared to the ice‐free surface waters in the Dalton Polynya. The seasonal depletion of mixed‐layer TCO2 (6 to 51 μmol/kg) in ice‐free regions was primarily driven by sea ice melt and biological CO2 uptake. Estimates of net community production (NCP) reveal net autotrophy in the ice‐free Dalton Polynya (NCP = 5–20 mmol C m−2 day−1) and weakly heterotrophic waters near the ice‐covered TIS (NCP = −4–0 mmol C m−2 day−1). Satellite‐derived estimates of chlorophyll a (Chl a) and sea ice coverage suggest that the early summer season in 2014/2015 was anomalous relative to the long‐term (1997–2017) record, with lower surface Chl a concentrations and a greater degree of sea ice cover during the period of observation; the implications for seasonal primary production and air‐sea CO2 exchange are discussed. This study highlights the importance of both physical and biological processes in controlling air‐sea CO2 fluxes and the significant interannual variability of the CO2 system in Antarctic coastal regions.

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Section: Resultssupporting

confidence: 85%

Section: 1029/2018jc014882mentioning

confidence: 62%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Summer Carbonate Chemistry in the Dalton Polynya, East Antarctica

Arroyo¹,

Shadwick

Tilbrook

2019

JGR Oceans

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“…Comparison to certified reference materials suggests an accuracy and precision for both DIC and alkalinity of better than ±2 µmol kg −1 . Full details have recently been published (Roden et al, 2016). Calculations of pH (free scale) and calcite saturation were based on the Seacarb version 3.1.2 software (https://CRAN.R-project.…”

Section: Analysis Of Nutrients Dissolved Inorganic Carbon Alkalinitmentioning

confidence: 99%

Distribution of planktonic biogenic carbonate organisms in the Southern Ocean south of Australia: a baseline for ocean acidification impact assessment

et al. 2018

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Abstract. The Southern Ocean provides a vital service by absorbing about one-sixth of humankind's annual emissions of CO 2 . This comes with a cost -an increase in ocean acidity that is expected to have negative impacts on ocean ecosystems. The reduced ability of phytoplankton and zooplankton to precipitate carbonate shells is a clearly identified risk. The impact depends on the significance of these organisms in Southern Ocean ecosystems, but there is very little information on their abundance or distribution. To quantify their presence, we used coulometric measurement of particulate inorganic carbonate (PIC) on particles filtered from surface seawater into two size fractions: 50-1000 µm to capture foraminifera (the most important biogenic carbonate-forming zooplankton) and 1-50 µm to capture coccolithophores (the most important biogenic carbonate-forming phytoplankton). Ancillary measurements of biogenic silica (BSi) and particulate organic carbon (POC) provided context, as estimates of the biomass of diatoms (the highest biomass phytoplankton in polar waters) and total microbial biomass, respectively. Results for nine transects from Australia to Antarctica in 2008-2015 showed low levels of PIC compared to Northern Hemisphere polar waters. Coccolithophores slightly exceeded the biomass of diatoms in subantarctic waters, but their abundance decreased more than 30-fold poleward, while diatom abundances increased, so that on a molar basis PIC was only 1 % of BSi in Antarctic waters. This limited importance of coccolithophores in the Southern Ocean is further emphasized in terms of their associated POC, representing less than 1 % of total POC in Antarctic waters and less than 10 % in subantarctic waters. NASA satellite ocean-colour-based PIC estimates were in reasonable agreement with the shipboard results in subantarctic waters but greatly overestimated PIC in Antarctic waters. Contrastingly, the NASA Ocean Biogeochemical Model (NOBM) shows coccolithophores as overly restricted to subtropical and northern subantarctic waters. The cause of the strong southward decrease in PIC abundance in the Southern Ocean is not yet clear. The poleward decrease in pH is small, and while calcite saturation decreases strongly southward, it remains well above saturation (> 2). Nitrate and phosphate variations would predict a poleward increase. Temperature and competition with diatoms for limiting iron appear likely to be important. While the future trajectory of coccolithophore distributions remains uncertain, their current low abundances suggest small impacts on overall Southern Ocean pelagic ecology.

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Eddy‐induced carbon transport across the Antarctic Circumpolar Current

Moreau

Penna

Llort

et al. 2017

Global Biogeochemical Cycles

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The implications of a mesoscale eddy for relevant properties of the Southern Ocean carbon cycle are examined with in situ observations. We explored carbon properties inside a large (~190 km diameter) cyclonic eddy that detached from the Subantarctic Front (SAF) south of Tasmania in March 2016. Based on remote sensing, the eddy was present for ~2 months in the Subantarctic Zone (SAZ), an important region of oceanic carbon dioxide (CO2) uptake throughout the annual cycle and carbon subduction (i.e., where mode and intermediate waters form), before it was reabsorbed into the SAF. The eddy was sampled during the middle of its life, 1 month after it spawned. Comparatively, the eddy was ~3°C colder, 0.5 practical salinity unit fresher, and less biologically productive than surrounding SAZ waters. The eddy was also richer in dissolved inorganic carbon (DIC) and had lower saturation states of aragonite and calcite than the surrounding SAZ waters. As a consequence, it was a strong source of CO2 to the atmosphere (with fluxes up to +25 mmol C m−2 d−1). Compared to the SAF waters, from which it originated, DIC concentration in the eddy was ~20 μmol kg−1 lower, indicating lateral mixing, small‐scale recirculation, or eddy stirring with lower‐DIC SAZ waters by the time the eddy was observed. As they are commonly spawned from the Antarctic Circumpolar Current, and as 50% of them decay in the SAZ (the rest being reabsorbed by the SAF‐N), these types of eddies may represent a significant south‐north transport pathway for carbon across the ACC and may alter the carbon properties of SAZ waters.

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Carbon cycling dynamics in the seasonal sea-ice zone of East Antarctica

Cited by 24 publications

References 119 publications

Summer Carbonate Chemistry in the Dalton Polynya, East Antarctica

Summer Carbonate Chemistry in the Dalton Polynya, East Antarctica

Distribution of planktonic biogenic carbonate organisms in the Southern Ocean south of Australia: a baseline for ocean acidification impact assessment

Eddy‐induced carbon transport across the Antarctic Circumpolar Current

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