Dr. Thato Mtshali (Chief scientists) during SOSCEx III summer cruise.

Dr. Thato Mtshali (Chief scientists) during SOSCEx III summer cruise.

The Southern Ocean has a powerful influence on Earth’s climate, as it stores more anthropogenic CO2 and heat than any other latitude band on Earth. This massive body of water also plays a pivotal ecosystem role in regulating the supply of nutrients to lower latitudes which supports about 80% of ocean production. Its ability to continue to provide ‘services’ that slow the rate of climate change is unknown. Equally uncertain are the potential climate effects if the rates of carbon and heat absorption in the Southern Ocean begin to slow.

Changes to the Southern Ocean carbon cycle and its impact on 21st century atmospheric CO2 depend critically on the climate sensitivity of these large and small-scale characteristics. Using a variety of observational tools, modelling and ocean robotics (gliders), the SOSCEx III project aimed to explore the nature of this scale sensitivity with a particular focus on the seasonal cycle mode as a test for the climate sensitivity of earth systems models in respect of the evolution of both atmospheric CO2 and ocean ecosystems.

The second leg of the third SOSCEx III project, a CSIR-SOCCO-led programme, which started last year in winter (22nd July – 15th August 2015) was successfully completed during our annual summer relief voyage SANAE 55 (5th December 2015 to 11th February 2016) on-board RV SA Agulhas II. During this cruise, 7 SANAP funded projects from different institutions across South Africa were hosted on-board (CSIR-SOSCEx III, DEA-CPR, UCT-SAMOC-SA, SUN-S&V, UP-MRI, UCT-Sea-Bird-life SA and SAWS).

Within the CSIR-SOSCEx III project, 5 on-board experimental observations were conducted, i) Trace metal Iron and other bioactive trace elements measurements, ii) Bio-optics Ocean Colour, iii) Primary Productivity and the Biological Carbon Pump, iv) Ocean Robotics using gliders for ocean physics characterization and v) Ocean pCO2 measurements.

SANAE 55 ship based scientists from different institutions posing in front of a wave glider.

SANAE 55 ship based scientists from different institutions posing in front of a wave glider.

The specific aims of the SOSCEx III summer cruise were:

  1. to retrieve, exchange and re-deploy the ocean robotics (wave and buoyancy gliders) at two “process stations ” to complete the high-resolution sampling of a full seasonal cycle in the Sub-Antarctic Zone (SAZ)
  2. to provide dissolved iron (dFe) profiles in the upper mixed layer and conduct on-board Photosynthesis vs Irradiance and Fe/light bioassay incubation experiments. The winter versus summer dFe profiles will aid us in understanding how winter dFe entrainment is used to initiate the spring bloom and sustain summer growth.
  3. to collect high resolution underway bio-optics measurements that characterise the phytoplankton community and contribute towards improved ocean colour algorithm development specific to the Southern Ocean,
  4. to characterise CO2 flux in austral spring that will contribute to our long-term CO2 observations along the Bonus Good Hope line.

 

 

This high seasonal sampling resolution at these stations will aid us in understanding the seasonal variability in ocean physics, Mixed Layer and Ferricline Depths (a region of high Fe concentration in the water column) and how the residence phytoplankton species adapt and response to Fe and light deprivation.

Wave glider deployment during SOSCEx III summer cruise

Wave glider deployment during SOSCEx III summer cruise

This was the first time that we South African scientists sampled the south Atlantic basin of the Southern Ocean during for  spanning winter through to the end of summer and the dataset obtained during these cruises will deliver knowledge of chemical, biological and physical changes needed to assess the consequences of Southern Ocean changes on the carbon cycle and climate and also contribute in refining Biogeochemical Model parameters.

gliders

A wave glider stays on the surface and is powered by solar panels. It measures CO2 flux, conductivity, temperature, depth and weather, while the buoyancy glider profiles the water column and dives up to 1000m depth four times a day. It measures temperature, salinity, dissolved oxygen level and phytoplankton abundance. These gliders relay real-time data via satellite to scientists based in Cape Town CSIR-SAMERC

.

Dr. Thato Mtshali (Chief scientists) during SOSCEx III summer cruise.

Dr. Thato Mtshali (Chief scientists) during SOSCEx III summer cruise.

The Southern Ocean has a powerful influence on Earth’s climate, as it stores more anthropogenic CO2 and heat than any other latitude band on Earth. This massive body of water also plays a pivotal ecosystem role in regulating the supply of nutrients to lower latitudes which supports about 80% of ocean production. Its ability to continue to provide ‘services’ that slow the rate of climate change is unknown. Equally uncertain are the potential climate effects if the rates of carbon and heat absorption in the Southern Ocean begin to slow.

Changes to the Southern Ocean carbon cycle and its impact on 21st century atmospheric CO2 depend critically on the climate sensitivity of these large and small-scale characteristics. Using a variety of observational tools, modelling and ocean robotics (gliders), the SOSCEx III project aimed to explore the nature of this scale sensitivity with a particular focus on the seasonal cycle mode as a test for the climate sensitivity of earth systems models in respect of the evolution of both atmospheric CO2 and ocean ecosystems.

The second leg of the third SOSCEx III project, a CSIR-SOCCO-led programme, which started last year in winter (22nd July – 15th August 2015) was successfully completed during our annual summer relief voyage SANAE 55 (5th December 2015 to 11th February 2016) on-board RV SA Agulhas II. During this cruise, 7 SANAP funded projects from different institutions across South Africa were hosted on-board (CSIR-SOSCEx III, DEA-CPR, UCT-SAMOC-SA, SUN-S&V, UP-MRI, UCT-Sea-Bird-life SA and SAWS).

Within the CSIR-SOSCEx III project, 5 on-board experimental observations were conducted, i) Trace metal Iron and other bioactive trace elements measurements, ii) Bio-optics Ocean Colour, iii) Primary Productivity and the Biological Carbon Pump, iv) Ocean Robotics using gliders for ocean physics characterization and v) Ocean pCO2 measurements.

SANAE 55 ship based scientists from different institutions posing in front of a wave glider.

SANAE 55 ship based scientists from different institutions posing in front of a wave glider.

The specific aims of the SOSCEx III summer cruise were:

  1. to retrieve, exchange and re-deploy the ocean robotics (wave and buoyancy gliders) at two “process stations ” to complete the high-resolution sampling of a full seasonal cycle in the Sub-Antarctic Zone (SAZ)
  2. to provide dissolved iron (dFe) profiles in the upper mixed layer and conduct on-board Photosynthesis vs Irradiance and Fe/light bioassay incubation experiments. The winter versus summer dFe profiles will aid us in understanding how winter dFe entrainment is used to initiate the spring bloom and sustain summer growth.
  3. to collect high resolution underway bio-optics measurements that characterise the phytoplankton community and contribute towards improved ocean colour algorithm development specific to the Southern Ocean,
  4. to characterise CO2 flux in austral spring that will contribute to our long-term CO2 observations along the Bonus Good Hope line.

 

 

This high seasonal sampling resolution at these stations will aid us in understanding the seasonal variability in ocean physics, Mixed Layer and Ferricline Depths (a region of high Fe concentration in the water column) and how the residence phytoplankton species adapt and response to Fe and light deprivation.

Wave glider deployment during SOSCEx III summer cruise

Wave glider deployment during SOSCEx III summer cruise

This was the first time that we South African scientists sampled the south Atlantic basin of the Southern Ocean during for  spanning winter through to the end of summer and the dataset obtained during these cruises will deliver knowledge of chemical, biological and physical changes needed to assess the consequences of Southern Ocean changes on the carbon cycle and climate and also contribute in refining Biogeochemical Model parameters.

gliders

A wave glider stays on the surface and is powered by solar panels. It measures CO2 flux, conductivity, temperature, depth and weather, while the buoyancy glider profiles the water column and dives up to 1000m depth four times a day. It measures temperature, salinity, dissolved oxygen level and phytoplankton abundance. These gliders relay real-time data via satellite to scientists based in Cape Town CSIR-SAMERC

.

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