One of scientific grand challenges to global climate for the balance of the 21st century are the projected changes to the feedbacks between carbon and climate and the Southern Ocean is one of the key systems in addressing this challenge. The Southern Ocean is emerging as the climate and ocean ecosystems “fly-wheel” of the planet .

The SOCCO research strategy focuses on the hypothesis that fine scale ocean dynamics are key to understanding the role of the Southern Ocean in global century-scale trends of atmospheric CO2 and regional climate change. We use this scale sensitivity approach towards:

  • Understanding the contemporary variability and the century-scale evolution of carbon fluxes and ocean productivity
  • Modelling and observing the dynamics from the interaction of seasonal and synoptic  time scales with meso and submesoscale spatial scales
  • Increasing the reliability of past and future projections of the changing role of the Southern Ocean global carbon – climate feedbacks

Biases in climate and earth systems models are emerging as observations start to provide improved constraints to the way models reflect the most important modes of variability such as the Seasonal Cycle. These biases provide a strong basis to focus the research that is needed to understand the the mechanisms in ocean geophysics and biogeochemistry that may then lead to significantly improved 21st century climate projections.

The 5-year strategy 2017 – 2021 has four main Themes

Theme 1: Understanding the scale sensitivities of the processes and feedbacks that explain how the carbon cycle of the Southern Ocean will evolve in 21st Century

Societal Impact: Delivering an advanced HCD platform and improving climate models projections in the 21st Century through problem-led large-scale basic science with a Southern Ocean focus.

Theme 2: Long term observations and the assessment of contemporary seasonal – decadal trends of CO2 and Primary Production in the Southern Ocean

Societal Impact: National and global climate mitigation policy support by delivering continuous state-of-the-system information on CO2 and the biological carbon pump in the Southern Ocean, These will be technology demonstrators that can become the nucleus of future climate and carbon economics linked services industries.

Theme 3: Address the Southern Ocean CO2 and Primary Production biases in the NEMO-PISCES ocean model and the CSIR Variable Resolution Earth Systems Model (VRESM)

Societal Impact: Deliver on the societal need for reliable decadal regional and global climate prediction of evolving climate risk in support of food security, urban economy, and human health.

Theme 4: Sustainability and Innovation in World Class Science and Technology Facilities for Ocean Research and Services Innovation

Societal Impact: Delivering on science-led impact on HCD, ocean-climate science and ocean technological innovation in support of new manufacturing and services industrial opportunities through well considered infrastructure investments.

 

Fig.1: Depicts the SOCCO scale-centred approach which hypothesises that in order to understand and predict the century scale evolution CO2 and its radiative and ocean acidification forcing it is necessary to understand and correctly parametrize the processes inside the seasonal – sub-seasonal and meso and sub-mesoscale “window”. This scale sensitivity links to the CO2 through the feedback of the upwelling of CO2 rich water, the biological pump and the solubility pump.

Fig.1: Depicts the SOCCO scale-centred approach which hypotheses that in order to understand and predict the century scale evolution CO2 and its radiative and ocean acidification forcing it is necessary to understand and correctly parameterize the processes inside the seasonal – sub-seasonal and meso and sub-mesoscale “window”. This scale sensitivity links to the CO2 through the feedback of the upwelling of CO2 rich water, the biological pump and the solubility pump.

 

SOCCO takes an interdisciplinary approach to understanding and projecting the Carbon – Climate links in the Southern Ocean. It comprises research groups with focus on dynamics of upper ocean physics, ocean CO2 and oxygen, ocean productivity and carbon export, Iron and nutrient biogeochemistry. Our approach involves a combination of long term observations linked to regular voyages of the SA Agulhas II to the Southern Ocean, Seasonal Cycle Experiments (SOSCEx) and high resolution modelling. More recently we are also introducing the use of robotics into both the long term observations and the experimental approaches.

The physical characteristics and dynamics of the ocean and atmosphere are central  to understanding the scale sensitivity of the seasonal cycle variability and trends of the carbon cycle in the Southern Ocean and how it influences global Carbon – Climate feedbacks. SOCCO researchers pursue research focused predominantly on how synoptic forcing of the upper ocean interacts with submesoscale (<10km) to mesoscale (10-200km) oceanographic processes that influence upper ocean mixing and stratification dynamics. Our science  makes use of regional and global models to extend these local dynamics to the Southern Ocean as a whole including both subduction and sea ice processes. These approaches make South Africa a leading contributor to Southern Hemisphere ocean and climate science.

SOCCO’s ocean physics-related research takes an integrated approach to observations and modelling, combining the use of numerical modelling simulations, ship-based observations and high-resolution observations from autonomous ocean gliders and floats. Emphasis has been placed on resolving the seasonal cycle of upper ocean physical processes in the Southern Ocean and relating these to biogeochemical responses. This was undertaken through the Southern Ocean Seasonal Cycle Experiment (SOSCEx) deployment of coupled surface and ocean interior robotic instruments i that continuously observe the ocean and air-sea exchange processes for extended periods of time (6 months) and resolving the temporal and spatial scales of variability at unprecedented high resolution.

Our research contributes to South Africa’s developmental needs by using novel approaches in advanced observations, numerical modelling and analysis to train undergraduate and post-graduate students.

 

  • A CTD station being completed at the Antarctic ice shelf to investigate the diurnal and event scale variability of upper ocean physics and biogeochemistry in the ice impacted polar seas.
  • SOCCO and South Africa’s geographical coverage of the Southern Hemisphere oceans and access to the Antarctic region. The coloured lines represent the domains covered by annual South African research and logistical voyages (carried out on the SA Agulhas II): Marion Island, Gough and Tristan du Cunha Islands, SANAE base, South Georgia Island and South Sandwich Islands. The blue lines represent the northern and southern extent of the Antarctic Circumpolar Current, while the magenta line represents the position of the Agulhas Current and Retroflection. The maximum winter sea-ice extent is indicated. The background shading represents the ocean depth.
  • High-resolution time series of (a) temperature, (b) stratification and (c) chlorophyll-a collected by an ocean glider in the Subantarctic region. These observations provide a first look at the seasonal evolution of upper ocean physics and biogeochemistry in the Southern Ocean.
  • Profiling gliders are deployed in the coastal regions of South Africa and the Southern Ocean to observe key physical and biogeochemical properties of the water column.Compared to ships and moorings, these innovative and high-tech robots provide a cost-effective means to monitor the environment over extended paeriods of time.
  • Deployment of a underway UCTD from the research ship, the SA Agulhas II. The underway mode profiling instrument collects temperature, salinity and pressure measurements up to 500m depth.UCTD deployments means we are able to collect sub surface water column measurements in underway mode without stopping the ship.
  • The Southern Ocean Seasonal Cycle Experiment (SOSCEx): Tow glider tracks overlaid onto the spring-summer surface chlorophyll-a concentrations, as measured from satellite.
  • A Wave Glider is retrieved with a combined ship and small boat approach after spending numerous months sampling the Southerrn Ocean air-sea interface. These rare and valuable data are crucial to understanding the variability of the upper ocean currents and CO2 fluxes. Note the severe barnacle growth on thee underside of the glider’s surface float.
Related News and Publications

The physical characteristics and dynamics of the ocean and atmosphere are central  to understanding the scale sensitivity of the seasonal cycle variability and trends of the carbon cycle in the Southern Ocean and how it influences global Carbon – Climate feedbacks. SOCCO researchers pursue research focused predominantly on how synoptic forcing of the upper ocean interacts with submesoscale (<10km) to mesoscale (10-200km) oceanographic processes that influence upper ocean mixing and stratification dynamics. Our science  makes use of regional and global models to extend these local dynamics to the Southern Ocean as a whole including both subduction and sea ice processes. These approaches make South Africa a leading contributor to Southern Hemisphere ocean and climate science.

SOCCO’s ocean physics-related research takes an integrated approach to observations and modelling, combining the use of numerical modelling simulations, ship-based observations and high-resolution observations from autonomous ocean gliders and floats. Emphasis has been placed on resolving the seasonal cycle of upper ocean physical processes in the Southern Ocean and relating these to biogeochemical responses. This was undertaken through the Southern Ocean Seasonal Cycle Experiment (SOSCEx) deployment of coupled surface and ocean interior robotic instruments i that continuously observe the ocean and air-sea exchange processes for extended periods of time (6 months) and resolving the temporal and spatial scales of variability at unprecedented high resolution.

Our research contributes to South Africa’s developmental needs by using novel approaches in advanced observations, numerical modelling and analysis to train undergraduate and post-graduate students.

The mean annual global anthropogenic carbon budget and ocean uptake (1.8 – 2.2PgCy-1) are now well established, with the Southern Ocean accounting for about 40 – 50% of the total ocean uptake. The ocean mediation of atmospheric CO2 has two components: the uptake of anthropogenic CO2 and variability in the exchange of natural CO2. While the magnitude of the steady state ocean CO2 uptake, linked to the increasing CO2 emissions, is now robustly constrained the major challenge to the ocean carbon community is to understand the drivers, magnitudes and trends of the non-steady state driven changes in the ocean carbon fluxes. Moreover, biases in climate and earth systems models are emerging as observations start to provide improved constraints to the way models reflect the most important modes of variability such as the Seasonal Cycle.

We hypothesize that an important part of the climate sensitivity of these processes which regulate the carbon, heat and productivity fluxes are linked to fine-scale ocean dynamics associated with the impact of storms in upper ocean physics. These are not adequately understood and reflected in coupled climate and earth systems models. This proposal aims to explore the nature of this scale sensitivity of CO2 fluxes with a particular focus on how storm characteristics influence the evolution of the the seasonal cycle mode. This will ultimately be a test for the climate sensitivity of earth systems models in respect of the evolution of both atmospheric CO2 and ocean ecosystems and winter rainfall in Southern Africa in the 21st Century.

Century-scale trends in atmospheric and ocean CO2 face a dual problem which impacts on global and regional scale mitigation of CO2 emissions to limit climate change risk: not only will the uptake rate of anthropogenic CO2 decrease because of changing CO2 chemistry (Buffering & Ocean Acidification) and warming but as importantly, climate forcing may begin to alter the ocean physics that controls the mobilization of the much larger natural CO2 flux in the Southern Ocean.

Carbon research in SOCCO approaches these questions along three lines:

  • Understanding the climate sensitivity through fine scale mechanisms: As part of its scientific focus on fine scale ocean dynamics SOCCO CO2 research makes a strong contribution to dedicated experiments (SOSCEx), which aim to understand the sensitivity of the carbon cycle and CO2 fluxes to the seasonal and intraseasonal dynamics of upper ocean physics (meso and sub-mesoscale).  In this domain we are exploring the use of robotics (surface wave gliders and ocean interior buoyancy gliders) to make observations within these spatial and temporal scale constraints. The Southern Ocean Seasonal Cycle Experiment (SOSCEx) is our platform for these experiments, which target the core hypothesis of the programme: fine scale (carbon) – large scale (climate) links (Monteiro et al., 2015).
  • Improving the observational constraints to CO2 variability and trends: It has established a long-term ship –based CO2 observations system making underway observations in the southeast Atlantic Ocean and the southwest Indian Ocean (Fig. 1).  This includes the first sustained winter observations in the SE Atlantic sector of the Southern Ocean. These data are made available to the national (SADCO) and global (CDIAC) databases from where they are then integrated after 2nd level QC into the SOCAT and later ocean acidification databases.  Through this SOCCO builds up a data set, which includes a wide range of ancillary physics and biogeochemical variables, to support its own research as well as global community initiatives.  These data together with high resolution remote sensing observations are used as the “learning” and evaluation for high resolution machine learning techniques that generate data products used to derive trends and assess models (Gregor et al., 2017; 2018).   These address the need for high precision (< 0.1PgCy-1) CO2 air – sea exchange fluxes in a data sparse system.  This part of a global effort to reduce the global uncertainty of CO2 fluxes to ~10% of the mean annual flux necessary to resolve inter-annual variability and long-term trends.

Identifying and addressing  model biases: in SOCCO we approach the models along two different approaches: We use a hierarchy of global and regional medium (200km), fine (10km) and very high resolution (2km) model runs to test both scale sensitivity research questions for CO2 and the carbon cycle as well as explore the understanding and use of the seasonal cycle as a mode that provides a rigorous test to model outputs (Mongwe et al., 2016).  We also investigate biases in the Southern Ocean carbon fluxes in global Earth Systems Models (Mongwe et al., 2018) as well as contribute to the development of the South African contribution to the 6th Assessment round of the IPCC (AR6) the CSIR-Variable Resolution Earth Systems Model (VrESM).

Vindta maintenance

Vindta maintenance

Related News and Publications

The mean annual global anthropogenic carbon budget and ocean uptake (1.8 – 2.2PgCy-1) are now well established, with the Southern Ocean accounting for about 40 – 50% of the total ocean uptake. The ocean mediation of atmospheric CO2 has two components: the uptake of anthropogenic CO2 and variability in the exchange of natural CO2. While the magnitude of the steady state ocean CO2 uptake, linked to the increasing CO2 emissions, is now robustly constrained the major challenge to the ocean carbon community is to understand the drivers, magnitudes and trends of the non-steady state driven changes in the ocean carbon fluxes. Moreover, biases in climate and earth systems models are emerging as observations start to provide improved constraints to the way models reflect the most important modes of variability such as the Seasonal Cycle.

We hypothesize that an important part of the climate sensitivity of these processes which regulate the carbon, heat and productivity fluxes are linked to fine-scale ocean dynamics associated with the impact of storms in upper ocean physics. These are not adequately understood and reflected in coupled climate and earth systems models. This proposal aims to explore the nature of this scale sensitivity of CO2 fluxes with a particular focus on how storm characteristics influence the evolution of the the seasonal cycle mode. This will ultimately be a test for the climate sensitivity of earth systems models in respect of the evolution of both atmospheric CO2 and ocean ecosystems and winter rainfall in Southern Africa in the 21st Century.

Century-scale trends in atmospheric and ocean CO2 face a dual problem which impacts on global and regional scale mitigation of CO2 emissions to limit climate change risk: not only will the uptake rate of anthropogenic CO2 decrease because of changing CO2 chemistry (Buffering & Ocean Acidification) and warming but as importantly, climate forcing may begin to alter the ocean physics that controls the mobilization of the much larger natural CO2 flux in the Southern Ocean.

Carbon research in SOCCO approaches these questions along three lines:

  • Understanding the climate sensitivity through fine scale mechanisms: As part of its scientific focus on fine scale ocean dynamics SOCCO CO2 research makes a strong contribution to dedicated experiments (SOSCEx), which aim to understand the sensitivity of the carbon cycle and CO2 fluxes to the seasonal and intraseasonal dynamics of upper ocean physics (meso and sub-mesoscale).  In this domain we are exploring the use of robotics (surface wave gliders and ocean interior buoyancy gliders) to make observations within these spatial and temporal scale constraints. The Southern Ocean Seasonal Cycle Experiment (SOSCEx) is our platform for these experiments, which target the core hypothesis of the programme: fine scale (carbon) – large scale (climate) links (Monteiro et al., 2015).
  • Improving the observational constraints to CO2 variability and trends: It has established a long-term ship –based CO2 observations system making underway observations in the southeast Atlantic Ocean and the southwest Indian Ocean (Fig. 1).  This includes the first sustained winter observations in the SE Atlantic sector of the Southern Ocean. These data are made available to the national (SADCO) and global (CDIAC) databases from where they are then integrated after 2nd level QC into the SOCAT and later ocean acidification databases.  Through this SOCCO builds up a data set, which includes a wide range of ancillary physics and biogeochemical variables, to support its own research as well as global community initiatives.  These data together with high resolution remote sensing observations are used as the “learning” and evaluation for high resolution machine learning techniques that generate data products used to derive trends and assess models (Gregor et al., 2017; 2018).   These address the need for high precision (< 0.1PgCy-1) CO2 air – sea exchange fluxes in a data sparse system.  This part of a global effort to reduce the global uncertainty of CO2 fluxes to ~10% of the mean annual flux necessary to resolve inter-annual variability and long-term trends.

Identifying and addressing  model biases: in SOCCO we approach the models along two different approaches: We use a hierarchy of global and regional medium (200km), fine (10km) and very high resolution (2km) model runs to test both scale sensitivity research questions for CO2 and the carbon cycle as well as explore the understanding and use of the seasonal cycle as a mode that provides a rigorous test to model outputs (Mongwe et al., 2016).  We also investigate biases in the Southern Ocean carbon fluxes in global Earth Systems Models (Mongwe et al., 2018) as well as contribute to the development of the South African contribution to the 6th Assessment round of the IPCC (AR6) the CSIR-Variable Resolution Earth Systems Model (VrESM).

The Southern Ocean (SO) is one of the largest High-Nutrient, Low-Chlorophyll (HNLC) regions in the global ocean, where primary productivity (PP) is significantly impacted by the bioavailability of Iron (so-called “dissolved Iron (DFe)). This is due to its low concentrations (<1.0nM), driven in part by low solubility in oxygenated seawater and seasonally variable supply. Spatio-temporal observations of the Fe-pool (i.e. DFe, particulate Fe (PFe), Fe-binding ligands (Fe-L)) in the SO are restricted compared to other ocean regions, primarily due to accessibility in winter, limiting our understanding and parameterization of the full seasonal cycle. Seasonality plays an important role in determining the variability of the internal and external sources, and recycling of Fe in the SO, which ultimately constrains PP and the local strength and efficiency of the biological carbon pump.

The complex interplay of Fe sources and cycling within the SO controls phytoplankton growth, however key areas remain underdeveloped in our understanding of how phytoplankton respond to the Fe biogeochemical cycle, in particular the plasticity of phytoplankton to changes in Fe bioavailability. The relative importance of these adaptive mechanisms is important to understand how phytoplankton will respond to climate mediated changes in the Fe cycle under future climate change scenarios, long-term evolutionary adaptation to a changing Fe cycle has however not been fully resolved as yet. Characterizing these key variables of the Fe cycle with a multidisciplinary approach will improve our understanding of the Fe biogeochemical cycle and its role in the SO.

To better characterize the SO seasonal cycle, further investigation into the dynamics and variability of the Fe-biogeochemical cycle is required. The Iron research project within SOCCO aims to achieve this through 3 approaches, i) in-situ trace metal observations, ii) laboratory Fe-particles and Fe-binding ligands dissolution experiments and iii) laboratory intracellular culture experiments, with the following three aims to:

  1. i) increasing the number of in-situ observations of the entire Fe-pool (Dissolved Fe (dFe), particulate Fe (PFe), soluble Fe (SFe) and organically bound Fe (FeL)) and other bioactive trace metals across the seasonal cycle in the SO, thereby determining the spatial and vertical distribution of the Fe-pool during winter and spring to summer, and to evaluate the sources and cycling which will in turn characterize the physical, chemical and biological processes regulating these distributions
  2. ii) investigating the interactions between Fe and Fe-binding ligands through in-situ observations and laboratory studies, to better characterize the effects of these interactions on the physical speciation of Fe and how this translates to Fe bioavailability

iii) quantifying the ecophysiological response of SO phytoplankton species under variable environmental conditions (i.e. Fe concentrations, light availability, temperature) by investigating the interplay of mechanisms possessed by these phytoplankton species to adapt to changes in their environment through laboratory culture studies

  • FRRF system
  • FIA analysis for Fe concentration
  • FI-Auto-analyser
  • Bioassay sample filtration
Related News and Publications

The Southern Ocean (SO) is one of the largest High-Nutrient, Low-Chlorophyll (HNLC) regions in the global ocean, where primary productivity (PP) is significantly impacted by the bioavailability of Iron (so-called “dissolved Iron (DFe)). This is due to its low concentrations (<1.0nM), driven in part by low solubility in oxygenated seawater and seasonally variable supply. Spatio-temporal observations of the Fe-pool (i.e. DFe, particulate Fe (PFe), Fe-binding ligands (Fe-L)) in the SO are restricted compared to other ocean regions, primarily due to accessibility in winter, limiting our understanding and parameterization of the full seasonal cycle. Seasonality plays an important role in determining the variability of the internal and external sources, and recycling of Fe in the SO, which ultimately constrains PP and the local strength and efficiency of the biological carbon pump.

The complex interplay of Fe sources and cycling within the SO controls phytoplankton growth, however key areas remain underdeveloped in our understanding of how phytoplankton respond to the Fe biogeochemical cycle, in particular the plasticity of phytoplankton to changes in Fe bioavailability. The relative importance of these adaptive mechanisms is important to understand how phytoplankton will respond to climate mediated changes in the Fe cycle under future climate change scenarios, long-term evolutionary adaptation to a changing Fe cycle has however not been fully resolved as yet. Characterizing these key variables of the Fe cycle with a multidisciplinary approach will improve our understanding of the Fe biogeochemical cycle and its role in the SO.

To better characterize the SO seasonal cycle, further investigation into the dynamics and variability of the Fe-biogeochemical cycle is required. The Iron research project within SOCCO aims to achieve this through 3 approaches, i) in-situ trace metal observations, ii) laboratory Fe-particles and Fe-binding ligands dissolution experiments and iii) laboratory intracellular culture experiments, with the following three aims to:

  1. i) increasing the number of in-situ observations of the entire Fe-pool (Dissolved Fe (dFe), particulate Fe (PFe), soluble Fe (SFe) and organically bound Fe (FeL)) and other bioactive trace metals across the seasonal cycle in the SO, thereby determining the spatial and vertical distribution of the Fe-pool during winter and spring to summer, and to evaluate the sources and cycling which will in turn characterize the physical, chemical and biological processes regulating these distributions
  2. ii) investigating the interactions between Fe and Fe-binding ligands through in-situ observations and laboratory studies, to better characterize the effects of these interactions on the physical speciation of Fe and how this translates to Fe bioavailability

iii) quantifying the ecophysiological response of SO phytoplankton species under variable environmental conditions (i.e. Fe concentrations, light availability, temperature) by investigating the interplay of mechanisms possessed by these phytoplankton species to adapt to changes in their environment through laboratory culture studies

Biological production and carbon export to the deep ocean, “the biological pump” (BCP) is considered a major contributor to the Southern Ocean sink of natural CO2 removing an estimated 3 Pg of carbon from surface waters south of 30°S each year (33% of the global organic carbon flux) (Schlitzer et al., 2002). The BCP plays a critical role in maintaining the vertical DIC gradient between the surface and ocean interior.  The Southern Ocean’s BCP also plays an important role in regulating the supply of nutrients to thermocline waters (Subantarctic Mode Water and Intermediate Water) of the entire Southern Hemisphere and North Atlantic (Sarmiento et al., 2004), which in turn drives about 75% of low latitude ocean productivity (Sigman and Boyle, 2000). Remineralization of particulate organic carbon (POC) to CO2 by bacteria and zooplankton means that only a small fraction of the exported carbon flux reaches the interior with the depth distribution of remineralization controlling atmospheric CO2 levels (Kwon et al., 2009). Factors that regulate phytoplankton growth (light, nutrients), particle formation, rates of sinking (aggregation, ballasting, senescence, grazing) and re-mineralisation (bacterial activity, chemical dissolution) all modify the extent to which fixed carbon is effectively exported and hence the efficiency of the BCP. Despite their importance in the Southern Ocean, relatively little is known about the climate sensitivity and distribution and seasonal variability of these processes, which are essential to predicting the biogenic flux of CO2 (Arrigo et al., 1998). Changes to the BCP relative to the pre-industrial period would mean that it would start to impact on the net ocean fluxes of anthropogenic CO2. Quantifying the strength and efficiency of the BCP and its sensitivity to predicted changes in the Earth’s climate is fundamental to our ability to predict long term changes in the global carbon cycle.

  • Filter stand used to filter seawater samples during nutrient cycling experiments.
  • For the measurements of primary productivity and nutrient cycling rates, samples can be incubated in-situ instead of using incubators.
  • Incubators are used to replicate light levels from various depths and maintain a controlled temperature in order to estimate primary productivity and nitrogen cycling rates.
  • Incubators which have been set up on the SA Agulhas II during a research cruise in the Southern Ocean.
  • caption
  • Collection of samples for a nitrogen cycling study in St Helena Bay.
Related News and Publications

Biological production and carbon export to the deep ocean, “the biological pump” (BCP) is considered a major contributor to the Southern Ocean sink of natural CO2 removing an estimated 3 Pg of carbon from surface waters south of 30°S each year (33% of the global organic carbon flux) (Schlitzer et al., 2002). The BCP plays a critical role in maintaining the vertical DIC gradient between the surface and ocean interior.  The Southern Ocean’s BCP also plays an important role in regulating the supply of nutrients to thermocline waters (Subantarctic Mode Water and Intermediate Water) of the entire Southern Hemisphere and North Atlantic (Sarmiento et al., 2004), which in turn drives about 75% of low latitude ocean productivity (Sigman and Boyle, 2000). Remineralization of particulate organic carbon (POC) to CO2 by bacteria and zooplankton means that only a small fraction of the exported carbon flux reaches the interior with the depth distribution of remineralization controlling atmospheric CO2 levels (Kwon et al., 2009). Factors that regulate phytoplankton growth (light, nutrients), particle formation, rates of sinking (aggregation, ballasting, senescence, grazing) and re-mineralisation (bacterial activity, chemical dissolution) all modify the extent to which fixed carbon is effectively exported and hence the efficiency of the BCP. Despite their importance in the Southern Ocean, relatively little is known about the climate sensitivity and distribution and seasonal variability of these processes, which are essential to predicting the biogenic flux of CO2 (Arrigo et al., 1998). Changes to the BCP relative to the pre-industrial period would mean that it would start to impact on the net ocean fluxes of anthropogenic CO2. Quantifying the strength and efficiency of the BCP and its sensitivity to predicted changes in the Earth’s climate is fundamental to our ability to predict long term changes in the global carbon cycle.

Ocean colour remote sensing can provide routine, synoptic and highly cost-effective observations of biological and biogeochemical response to physical drivers across oceanic ecosystems, over decadal time scales and at high frequency. In many cases, remotely sensed data are the only systematic observations available for chronically under-sampled marine systems (e.g. the polar oceans), and there is thus a need to maximise the value of these observations by developing ecosystem-appropriate, well characterised products.

A primary focus of SOCCO’s bio-optical research is on gathering the necessary bio-optical and physiological data to develop and validate appropriate regional ocean colour algorithms for the Southern Ocean. This includes bio-optical data in the form of Inherent Optical Properties (IOP’s) (scattering, beam attenuation and absorption) and Apparent Optical Properties (AOP) (radiance, irradiance, reflectance, diffuse attenuation coefficient) and biogeochemical data that characterises the phytoplankton community (e.g. carbon content, size structure and dominant functional type). This information in conjunction with radiative transfer models and reflectance inversion algorithms will allow us to use satellite derived ocean colour data to investigate biological responses (through changes in biomass, community structure and physiology) to event, seasonal and inter-annual variability in ecosystem physical drivers at the required spatial and temporal scales. Given the important relationship between community size and carbon export these approaches will allow us to assess the potential for carbon cycling and carbon sequestration at the regional scale.

  • Scientists on the SA Agulhas collecting biogeochemical data to characterise the phytoplankton community structure.
  • Spatial distribution of mean chlorophyll concentrations for the Southern Ocean south of 30oS for Summer (January) taken from SeaWiFS ocean colour data. Frontal positions calculated from MADT contours are shown for the STF (red), the SAF (black), the PF (orange) and the SACCF (blue).
  • An example of absorption spectra for different monospecific phytoplankton cultures. Note the difference between diatoms grown at different light levels. Figure reproduced from Roesler (2013).
  • A variety of phytoplankton seen from a microscope
  • Filtration rig used to collect biogeochemical data that characterises the phytoplankton community structure.
  • The underway Inherent Optical Property system onboard the SA Agulhas
  • Regression of POC and cp (650 nm) for the Weddel Gyre (red line) compared with a global dataset from six different surveys (black dotted line). Taken from Ceinwen Smith MSc Thesis.
  • Scientists at work in the bio-optics and bio-geochemistry wet lab on the SA Agulhas II.
  • A section of chlorophyll and particulate organic carbon across the Weddell Gyre in the Southern Ocean calculated from the optical properties of fluorescence and beam attenuation respectively. Taken from Ceinwen Smith MSc Thesis.
Related News and Publications

Ocean colour remote sensing can provide routine, synoptic and highly cost-effective observations of biological and biogeochemical response to physical drivers across oceanic ecosystems, over decadal time scales and at high frequency. In many cases, remotely sensed data are the only systematic observations available for chronically under-sampled marine systems (e.g. the polar oceans), and there is thus a need to maximise the value of these observations by developing ecosystem-appropriate, well characterised products.

A primary focus of SOCCO’s bio-optical research is on gathering the necessary bio-optical and physiological data to develop and validate appropriate regional ocean colour algorithms for the Southern Ocean. This includes bio-optical data in the form of Inherent Optical Properties (IOP’s) (scattering, beam attenuation and absorption) and Apparent Optical Properties (AOP) (radiance, irradiance, reflectance, diffuse attenuation coefficient) and biogeochemical data that characterises the phytoplankton community (e.g. carbon content, size structure and dominant functional type). This information in conjunction with radiative transfer models and reflectance inversion algorithms will allow us to use satellite derived ocean colour data to investigate biological responses (through changes in biomass, community structure and physiology) to event, seasonal and inter-annual variability in ecosystem physical drivers at the required spatial and temporal scales. Given the important relationship between community size and carbon export these approaches will allow us to assess the potential for carbon cycling and carbon sequestration at the regional scale.

'