Southern Ocean Seasonal Cycle Experiment 2012: Seasonal scale climate and carbon cycle links

Swart, Sebastiaan; Chang, Nicolette; Fauchereau, Nicolas; Joubert, Warren; Lucas, Mike; Mtshali, Thato N.; Roychoudhury, Alakendra N.; Tagliabue, Alessandro; Thomalla, Sandy J.; Waldron, H. N.; Monteiro, Pedro M. S.

doi:10.4102/sajs.v108i3/4.1089

Cited by 31 publications

(31 citation statements)

References 8 publications

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“…The data used for this research were collected in the framework of the Southern Ocean Carbon and Climate Observatory (SOCCO; http://www.socco.org.za) during the Southern Ocean Seasonal Cycle Experiment (SOSCEx; Swart et al, 2012). Seaglider SG573 was deployed south of Gough Island in the South-East Atlantic Ocean at 43.0 • S, 11 • W (Figure 1).…”

Section: Glider Datamentioning

confidence: 99%

Using Optical Sensors on Gliders to Estimate Phytoplankton Carbon Concentrations and Chlorophyll-to-Carbon Ratios in the Southern Ocean

et al. 2017

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One approach to deriving phytoplankton carbon biomass estimates (C phyto ) at appropriate scales is through optical products. This study uses a high-resolution glider data set in the Sub-Antarctic Zone (SAZ) of the Southern Ocean to compare four different methods of deriving C phyto from particulate backscattering and fluorescence-derived chlorophyll (chl-a). A comparison of the methods showed that at low (<0.5 mg m −3 ) chlorophyll concentrations (e.g., early spring and at depth), all four methods produced similar estimates of C phyto , whereas when chlorophyll concentrations were elevated one method derived higher concentrations of C phyto than the others. The use of methods derived from particulate backscattering rather than fluorescence can account for cellular adjustments in chl-a:C phyto that are not driven by biomass alone. A comparison of the glider chl-a:C phyto ratios from the different optical methods with ratios from laboratory cultures and cruise data found that some optical methods of deriving C phyto performed better in the SAZ than others and that regionally derived methods may be unsuitable for application to the Southern Ocean. A comparison of the glider chl-a:C phyto ratios with output from a complex biogeochemical model shows that although a ratio of 0.02 mg chl-a mg C −1 is an acceptable mean for SAZ phytoplankton (in spring-summer), the model misrepresents the seasonal cycle (with decreasing ratios from spring to summer and low sub-seasonal variability). As such, it is recommended that models expand their allowance for variable chl-a:C phyto ratios that not only account for phytoplankton acclimation to low light conditions in spring but also to higher optimal chl-a:C phyto ratios with increasing growth rates in summer.

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Section: Glider Datamentioning

confidence: 99%

Using Optical Sensors on Gliders to Estimate Phytoplankton Carbon Concentrations and Chlorophyll-to-Carbon Ratios in the Southern Ocean

et al. 2017

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“…The Southern Ocean is quantitatively the most important region for worldwide carbon dynamics (today: Mikaloff Fletcher et al, 2006;glacial/interglacial: Watson and Naveira Garabato, 2006;future: Tjiputra et al, 2010;Roy et al, 2011), but it is also one of the least well year-round observed regions Swart et al, 2012;Pfeil et al, 2013;Sabine et al, 2013) due to its remoteness and high seasonality. Research priorities include the improvement of data coverage for carbon variables, dissolved oxygen and related tracers.…”

Section: Specific Regional Foci For Ocean Carbon Cycle Studiesmentioning

confidence: 99%

The ocean carbon sink – impacts, vulnerabilities and challenges

et al. 2015

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Abstract. Carbon dioxide (CO 2 ) is, next to water vapour, considered to be the most important natural greenhouse gas on Earth. Rapidly rising atmospheric CO 2 concentrations caused by human actions such as fossil fuel burning, land-use change or cement production over the past 250 years have given cause for concern that changes in Earth's climate system may progress at a much faster pace and larger extent than during the past 20 000 years. Investigating global carbon cycle pathways and finding suitable adaptation and mitigation strategies has, therefore, become of major concern in many research fields. The oceans have a key role in regulating atmospheric CO 2 concentrations and currently take up about 25 % of annual anthropogenic carbon emissions to the atmosphere. Questions that yet need to be answered are what the carbon uptake kinetics of the oceans will be in the future and how the increase in oceanic carbon inventory will affect its ecosystems and their services. This requires comprehensive investigations, including high-quality ocean carbon measurements on different spatial and temporal scales, the management of data in sophisticated databases, the application of Earth system models to provide future projections for given emission scenarios as well as a global synthesis and outreach to policy makers. In this paper, the current understanding of the ocean as an important carbon sink is reviewed with respect to these topics. Emphasis is placed on the complex interplay of different physical, chemical and biological processes that yield both positive and negative air-sea flux values for natural and anthropogenic CO 2 as well as on increased CO 2 (uptake) as the regulating force of the radiative warming of the atmosphere and the gradual acidification of the oceans. Major future ocean carbon challenges in the fields of ocean observations, modelling and process research as well as the relevance of other biogeochemical cycles and greenhouse gases are discussed.Published by Copernicus Publications on behalf of the European Geosciences Union.

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“…The samples and data presented here were obtained during the 55th South African National Antarctic Expedition (3 December 2015 to 11 February 2016) on board the S.A. Agulhas II to the Atlantic sector of the Southern Ocean as part of SOSCEx III (Swart et al, 2012). During the cruise, six nutrient addition PE long-term experiments were performed within the Atlantic sector of the Southern Ocean (Fig.…”

Section: Oceanographic Samplingmentioning

confidence: 99%

Modelled estimates of spatial variability of iron stress in the Atlantic sector of the Southern Ocean

Ryan‐Keogh

Thomalla²,

Mtshali³

et al. 2017

Biogeosciences

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Abstract. The Atlantic sector of the Southern Ocean is characterized by markedly different frontal zones with specific seasonal and sub-seasonal dynamics. Demonstrated here is the effect of iron on the potential maximum productivity rates of the phytoplankton community. A series of iron addition productivity versus irradiance (PE) experiments utilizing a unique experimental design that allowed for 24 h incubations were performed within the austral summer of 2015/16 to determine the photosynthetic parameters α B , P B max and E k . Mean values for each photosynthetic parameter under iron-replete conditions were 1.46 ± 0.55 (µg (µg Chl a) −1 h −1 (µM photons m −2 s −1 ) −1 ) for α B , 72.55 ± 27.97 (µg (µg Chl a) −1 h −1 ) for P B max and 50.84 ± 11.89 (µM photons m −2 s −1 ) for E k , whereas mean values under the control conditions were 1.25 ± 0.92 (µg (µg Chl a) −1 h −1 (µM photons m −2 s −1 ) −1 ) for α B , 62.44 ± 36.96 (µg (µg Chl a) −1 h −1 ) for P B max and 55.81 ± 19.60 (µM photons m −2 s −1 ) for E k . There were no clear spatial patterns in either the absolute values or the absolute differences between the treatments at the experimental locations. When these parameters are integrated into a standard depth-integrated primary production model across a latitudinal transect, the effect of iron addition shows higher levels of primary production south of 50 • S, with very little difference observed in the subantarctic and polar frontal zone. These results emphasize the need for better parameterization of photosynthetic parameters in biogeochemical models around sensitivities in their response to iron supply. Future biogeochemical models will need to consider the combined and individual effects of iron and light to better resolve the natural background in primary production and predict its response under a changing climate.

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Southern Ocean Seasonal Cycle Experiment 2012: Seasonal scale climate and carbon cycle links

Cited by 31 publications

References 8 publications

Using Optical Sensors on Gliders to Estimate Phytoplankton Carbon Concentrations and Chlorophyll-to-Carbon Ratios in the Southern Ocean

Using Optical Sensors on Gliders to Estimate Phytoplankton Carbon Concentrations and Chlorophyll-to-Carbon Ratios in the Southern Ocean

The ocean carbon sink – impacts, vulnerabilities and challenges

Modelled estimates of spatial variability of iron stress in the Atlantic sector of the Southern Ocean

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