Flux of CO2 Between Ocean and Atmosphere

Understanding air-sea gas exchange is important for improving storm forecasting and climate-change models, as well as for estimating the exchange of carbon between the upper and deep ocean. The datasets highlighted here showcase three different regimes of air-sea flux of CO2. The Endurance Array represents a coastal upwelling zone where during times of upwelling, CO2-rich deep water reaches the surface where it is outgassed into the atmosphere. The outgassing of upwelled water is then followed by a period of net intake of CO2 due to increased primary production from the nutrients upwelled with the CO2. The Pioneer Array, off the coast of New England, in contrast, is not an upwelling zone, but is an area of high productivity. As phytoplankton blooms occur, particularly in the winter/spring time period, there is a net flux of CO2 into the ocean. During the summer months as the surface water warms, the water can no longer hold as much CO2 and there is a small (relative to the upwelling) net outgassing. The cold, productive waters of the Argentine basin are a net sink for CO2 year round.

pCO2 Air-Sea instruments are located on surface buoys with one probe in the air and one probe in the water to measure the partial pressure of CO2 in both the atmosphere and the ocean. From these measurements, CO2 flux from the ocean to the atmosphere can be calculated to determine which locations and time periods the ocean is a source vs a sink of CO2.

Calculating air-sea gas exchange depends on the saturation of the gas in the water and wind speed. For example, the more saturated the water is with CO2 and the faster the wind is blowing across the water, the higher the flux of CO2 out of the water. Solubility of a gas in seawater is determined by the temperature and salinity of that water. Wind speed data used in this calculation are from meteorological sensors located on the tower of the surface buoy. For more information on how to calculate CO2 flux, check out the Data Product Specification document. Positive values indicate flux from the ocean into the atmosphere.

Data included in the below graphs and csv files represent CO2 flux data calculated through these measures. Data provided in the csv file only includes the CO2 data and does not include the meteorological data used in the calculations. However, the CO2 flux calculation instructions in the Python code does include instructions for pulling the necessary meteorological data to make the calculations. Additionally, corresponding meteorological data can accessed on OOINet (Endurance, Pioneer, Argentine) and Data Review Pages (Endurance, Pioneer, Argentine).

Seasonal cycles of CO2 air-sea gas exchange during 2017 at two coastal locations – the Endurance Array in the NE Pacific (black dots), and the Pioneer Array in the NW Atlantic (white dots). Positive data indicate a net flux of CO2 from the ocean into the atmosphere, negative data indicate a net flux of CO2 from the atmosphere into the ocean.

Access the Data

Disclaimer: data used in this example and provided in the .csv file were downloaded from the OOI on May 26, 2020. The file format and/or contents could have changed if downloaded directly from OOI Net after this date.

Access Data on OOI Net:
CE02SHSM-SBD12-04-PCO2AA000
CP03ISSM-SBD12-04-PCO2AA000

Click here for Python Code. Code demonstrates how to download pCO2 Air-Sea data from the Endurance and Pioneer arrays using the Machine-to-Machine (M2M) interface, calculate hourly averages and CO2 flux, and export the data as a .csv file.

Data Review Pages:
Endurance Array pCO2 Sensor
Pioneer Array pCO2 Sensor

Access the Data

Disclaimer: data used in this example and provided in the .csv file were downloaded from the OOI on May 26, 2020. The file format and/or contents could have changed if downloaded directly from OOI Net after this date.

Access Data on OOI Net:
GA01SUMO-SBD12-04-PCO2AA000

Click here for Python Code. Code demonstrates how to download pCO2 Air-Sea data from the Global Argentine Basin Surface Mooring using the Machine-to-Machine (M2M) interface, calculate hourly averages and CO2 flux, and export the data as a .csv file.

Data Review Page:
Argentine Basin pCO2 Sensor

Seasonal cycles of CO2 air-sea gas exchange during 2016 at Global Argentine Basin Array in the SW Atlantic. Positive data indicate a net flux of CO2 from the ocean into the atmosphere, negative data indicate a net flux of CO2 from the atmosphere into the ocean.

Coastal Endurance Oregon Shelf Surface Mooring (CE02SHSM)

Location: Oregon Continental Shelf, NE Pacific
Lat/Lon: 44.6393°N, 124.304°W
Water Column Depth: 80m
Platform: Surface Buoy
Instruments:
pCO2 Air-Sea (PCO2A-A) – in buoy well 1 probe in air, 1 probe in water
Bulk Meteorology Instrument Package (METBK-A) – on buoy tower, 3m above surface

Coastal Pioneer Inshore Surface Mooring (CP03ISSM)

Location: New England Continental Shelf, NW Atlantic
Lat/Lon: 40.3619°N, 70.8783°W
Water Column Depth: 92m
Platform: Surface Buoy
Instruments:
pCO2 Air-Sea (PCO2A-A) – in buoy well 1 probe in air, 1 probe in water
Bulk Meteorology Instrument Package (METBK-A) – on buoy tower, 3m above surface

Global Argentine Basin Apex Surface Mooring (GA01SUMO)

Location: Argentine Basin in the South Atlantic along the Brazil Current
Lat/Lon: 42.9204°S, 42.4409°W
Water Column Depth: 5,200m
Platform: Surface Buoy
Instruments:
pCO2 Air-Sea (PCO2A-A) – in buoy well 1 probe in air, 1 probe in water
Bulk Meteorology Instrument Package (METBK-A) – on buoy tower, 3m above surface

Essentials of Oceanography Textbook Sections:

7.3 What causes upwelling and downwelling? Coastal upwelling and downwelling
13.1 What is primary productivity?
16.3 What causes the atmosphere’s greenhouse effect? Which gases contribute to the Greenhouse Effect?
16.4 What changes are occurring in the oceans as a result of global warming? Recent increase in ocean acidity

Next Gen Science Standard Connections:

HS-LS2-5. Develop a model to illustrate the role of photosynthesis and cellular respiration in the cycling of carbon among the biosphere, atmosphere, hydrosphere, and geosphere. These data provide one component of this broader model by highlighting the exchange of carbon between the atmosphere and hydrosphere.

HS-ESS2-6. Develop a quantitative model to describe the cycling of carbon among the hydrosphere, atmosphere, geosphere, and biosphere. The cycling of carbon through the ocean varies by location and time of year. These data highlight examples of complexity needed in a model of the global ocean carbon cycle.

HS-ESS3-6. Use a computational representation to illustrate the relationships among Earth systems and how those relationships are being modified due to human activity. As humans have increased the CO2 in the atmosphere it has increased in the ocean through air-sea gas exchange. These data highlight the processes that control that exchange providing examples for and explanations of computational model results.

OOI Science Theme:

Ocean-Atmosphere Exchange

Related Publications:

Chan, F., et al. 2019. The dynamics and impact of ocean acidification and hypoxia: Insights from sustained investigations in the Northern California Current Large Marine Ecosystem. Oceanography 32(3):62–71, https://doi.org/10.5670/oceanog.2019.312.

Henderikx Freitas, F., et al. 2018. Temporal and spatial dynamics of physical and biological properties along the Endurance Array of the California Current ecosystem. Oceanography 31(1):80–89, https://doi.org/10.5670/oceanog.2018.113.

Arruda, R., et al. 2015. Air-sea CO2 fluxes and the controls on ocean surface pCO2 seasonal variability in the coastal and open-ocean southwestern Atlantic Ocean: a modeling study, Biogeosciences, 12, 5793–5809, https://doi.org/10.5194/bg-12-5793-2015.

Zhang, W. G., et al. 2013. Is biological productivity enhanced at the New England shelfbreak front?, Journal of Geophysical Research Oceans, 118:517–535, https://doi.org/10.1002/jgrc.20068.

Additional Resources:

Interactive Data Exploration – CO2 Exchange Between Air and Sea

NOAA PMEL Carbon Program – “How the oceans absorb carbon dioxide is critical for predicting climate change”

NOAA Ocean Acidification Program

Global Ocean Acidification Observing Network