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Research Area

Monitoring & Modeling

Ocean acidification monitoring and modeling allow us to assess ocean conditions and link it to impacts to marine life and the people who depend on healthy ecosystems.

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Monitoring "The Big Four"

Learn about what we measure and why.


When the ocean absorbs carbon dioxide, chemical reactions create hydrogen ions that act like free agents, able to react with other compounds. Two ways we track ocean acidification are through pH and total alkalinity (TA). pH is a measure of how many free hydrogen ions are in the seawater. The more carbon dioxide in the ocean, the more these free agents are created, causing lower pH (more acidic).


The partial pressure of CO2 (pCO2) tells us how much carbon dioxide is in seawater. This information helps us understand ocean carbonate chemistry and biological productivity in the region. pCO2 increases when the ocean absorbs more CO2 from the atmosphere with elevated emissions.


Alkalinity is the ocean’s buffering system against increasing acidity. Total alkalinity is a measure of the concentration of buffering molecules like carbonate and bicarbonate in the seawater that can neutralize acid.


Dissolved inorganic carbon (DIC) tells us how much non-biological carbon is in seawater. Inorganic carbon comes in three main forms that we measure for DIC: carbon dioxide (CO2), bicarbonate (HCO3-), and carbonate (CO32-). Understanding DIC can help us determine the balance of carbonate forms in the ocean and the likelihood of ocean acidification.

Buoys & Moorings

We currently have 19 OAP-supported buoys in coastal, open-ocean, and coral reef waters. 

There are currently 19 OAP-supported buoys in coastal, open-ocean and coral reef waters that contribute to NOAA's Ocean Acidification Monitoring Program.

Ship Surveys

Ocean acidification rsearch cruises are a way to collect information about a certain ecosystem or area of interest.

Anchors aweigh on ocean acidification research cruises

For decades, scientists have learned about physical, chemical and biological properties of the ocean and coasts by observations made at sea. Measurements taken during research cruises can be used to validate data taken by autonomous instruments. These research cruises serve as anchors to bring together researchers from the region and to serve as high-quality data benchmarks for other ocean monitoring in the area. 

One instrument that is paramount on research cruises is a conductivity, temperature, and depth sensor (CTD). CTDs measure fundamental water properties that are essential in water analysis, namely temperature, salinity, and depth. The sensor often goes in the water on a rosette, which also carries Niskin bottles used to collect water samples from various depths in the water column.
What we can learn from the CTD...
Numerous chemical and biological properties can be measured from water collected in the Niskin bottles. These properties include different parameters of the carbonate system used to assess ocean acidification, but also oxygen, nutrients, phytoplankton and more. This approach has the potential to co-locate several types of chemical, physical and biological information that can be used to elucidate processes and ocean acidification effects.
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Ships of Opportunity

Partnering with the Private Sector

Ships of Opportunity (SOPs) or Volunteer Observing Ships (VOSs) are vessels at sea for reasons other than ocean acidification , such as commercial cargo ships or ferries.

The owners of these vessels allow scientific instrumentation that measures ocean acidification parameters to be installed and collect data while the ship is underway. This allows data on ocean chemistry to be collected in many remote areas of the world’s ocean, such as high latitude waters, long distances from land (e.g. mid-basin waters), and places not easily accessible by research cruises. These partnerships have greatly increased the spatial coverage of ocean acidification monitoring world-wide. To learn more, check out the Ships of Opportunity programs established by the NOAA Pacific Marine Environmental Laboratory (PMEL) and the NOAA Atlantic Oceanographic Marine Laboratory (AOML).

See our funded projects in monitoring.

Calm sea with mountains on horizon and expansive sky in Ketchikan, Alaska. Credit: Phil Price, Flickr

Why we care:Alaskan Native communities rely on healthy marine ecosystems for work, sustenance and their way of life. Ocean acidification has documented impacts to marine life and these communities. An..

Spruce Island in the Kodiak region of Alaska. Bull kelp at water's surface with island in the background. Ocean acidification monitoring in this region helps prepare Kodiak Tribes for the impacts of ocean change. Credit: NOAA

Why we care:Alaskan Native communities rely on healthy marine ecosystems for work, sustenance and their way of life. Ocean acidification has documented impacts to marine life and these communities. Community..

Designing a framework for an ocean acidification vulnerability assessment in Puerto Rico through stakeholder interviews, science synthesis, and a regional workshop Why we careLocal and federal efforts (e.g., 4th National..

Wave Gliders

The Carbon Wave Glider

Scientists at the NOAA Pacific Marine Environmental Laboratory (PMEL) work with engineers at Liquid Robotics, Inc. to optimize a Carbon Wave Glider.

This wave glider can navigate via satellite from land. Carbon Wave Gliders can be outfitted with pCO2, pH, oxygen, temperature and salinity sensors. Gliders takes measurements as it moves through the water, expanding the spatial sampling of the area. The glider’s motion is driven by wave energy, and its sensors are powered through solar cells and batteries, when needed.

Coral Reef Monitoring

NOAA’s Coral Reef Conservation Program (CRCP) in partnership with OAP engages in a coordinated
and targeted series of field observations, moorings and ecological monitoring efforts in coral reef ecosystems.

The Coral Reef Conservation Program (CRCP) documents the dynamics of ocean acidification in coral reef systems and tracks the status and trends in ecosystem response. This effort serves as a subset of a broader CRCP initiative referred to as the National Coral Reef Monitoring Plan, which was established to support conservation of the Nation’s coral reef ecosystems. OAP contributes to this plan through overseeing and coordinating carbonate chemistry monitoring. This monitoring includes a broadly distributed spatial water sampling campaign complemented by a more limited set of moored instruments deployed at a small subset of representative sites in both the Atlantic, Caribbean, and Pacific regions. Coral reef carbonate chemistry monitoring is implemented by researchers at the NOAA Atlantic Oceanographic & Meteorological Laboratory (AOML) and NOAA’s Pacific Islands Fisheries Science Center (PIFSC) Coral Reef Ecosystems Division.
Benthic Surveys

Divers conduct benthic surveys to account for coral diversity and assess fish communities.

Calcification Accretion Units

Calcification Accretion Units (CAUs) assess the effects of changes in seawater carbonate chemistry on calcification (growth) and accretion in coral reefs and fleshy algae.

Monitoring Carbonate Chemistry

Carbonate chemistry monitoring determines the status of ocean acidification and its potential impacts on calcifiers like coral reefs and coralline algae.

Benthic Quadrats

Benthic quadrats are a common field tool when assesing coral cover.

CT Scans

Computerized tomography (CT) scans image the internal structure of corals.

Autonomus Reef Monitors

Deployed instruments monitor ocean conditions on reefs continuously.

Figure from: Harvey et al. 2010

Ecosystem Modeling 

Experiments on species response suggest that ocean acidification will directly affect a wide variety of organisms from calcifying shellfish and coral to fish and phytoplankton. Ecosystem models can capture the complex effects of ocean acidification on entire ecosystems.

How marine organisms respond to ocean acidification will be influenced by their reaction to chemistry change and their interactions with others species, such as their predators and prey. Scientists use ecosystem models to understand how ocean chemistry may affect entire ecosystems because they account for the complex interactions between organisms. Output from such modeling exercises can inform management of fisheries, protected species, and other important natural resources. Because ecosystem feedbacks are complex, understanding the uncertainty associated with these models is critical to effective management.

From Observations to Forecasts

Turning current observations into forecasts is the key mechanism by which adaptation plans are created.

Forecasting provides insight into a vision of the future by using models that visualize how quickly and where ocean chemistry will be changing in tandem with an understanding of how sensitive marine resources and communities are to these changes.

NOAA scientists have played an important role in development of the J-SCOPE forecast system, used to create seasonal forecasts for the North Pacific region. These forecasts will allow fisheries managers to predict seasonal outlooks for management decisions. Click on the image to open a lightbox. 

Related Publications

See publications from our funded projects for ocean acidification monitoring.

Citation: Zelun Wu, Hongjie Wang, Enhui Liao, Chuanmin Hu, Kelsea Edwing, Xiao-Hai Yan, Wei-Jun Cai, Air-sea CO2 flux in the Gulf of Mexico from observations and multiple machine-learning data products, Progress in Oceanography, Volume 223, 2024,103244, ISSN 0079-6611,
Citation: Lotterhos, K.E., Láruson, Á.J. & Jiang, LQ. Novel and disappearing climates in the global surface ocean from 1800 to 2100. Sci Rep 11, 15535 (2021).
Citation: Xue, L., Cai, W.-J., Jiang, L.-Q., & Wei, Q. (2021). Why are surface ocean pH and CaCO3 saturation state often out of phase in spatial patterns and seasonal cycles? Global Biogeochemical Cycles, 35, e2021GB006949.

Get involved with ocean acidification

The NOAA Ocean Acidification Program exists to meet the ocean acidification research and monitoring needs of the U.S. See how you can get involved to serve your community and participate in cutting-edge research and education and outreach. 

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The NOAA Ocean Acidification Program (OAP) works to prepare society to adapt to the consequences of ocean acidification and conserve marine ecosystems as acidification occurs. Learn more about the human connections and adaptation strategies from these efforts.

Adaptation approaches fostered by the OAP include:


Using models and research to understand the sensitivity of organisms and ecosystems to ocean acidification to make predictions about the future, allowing communities and industries to prepare


Using these models and predictions as tools to facilitate management strategies that will protect marine resources and communities from future changes


Developing innovative tools to help monitor ocean acidification and mitigate changing ocean chemistry locally


On the Road

Drive fuel-efficient vehicles or choose public transportation. Choose your bike or walk! Don't sit idle for more than 30 seconds. Keep your tires properly inflated.

With your Food Choices

Eat local- this helps cut down on production and transport! Reduce your meat and dairy. Compost to avoid food waste ending up in the landfill

With your Food Choices

Make energy-efficient choices for your appliances and lighting. Heat and cool efficiently! Change your air filters and program your thermostat, seal and insulate your home, and support clean energy sources

By Reducing Coastal Acidification

Reduce your use of fertilizers, Improve sewage treatment and run off, and Protect and restore coastal habitats

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You've taken the first step to learn more about ocean acidification - why not spread this knowledge to your community?

Every community has their unique culture, economy and ecology and what’s at stake from ocean acidification may be different depending on where you live.  As a community member, you can take a larger role in educating the public about ocean acidification. Creating awareness is the first step to taking action.  As communities gain traction, neighboring regions that share marine resources can build larger coalitions to address ocean acidification.  Here are some ideas to get started:

  1. Work with informal educators, such as aquarium outreach programs and local non-profits, to teach the public about ocean acidification. Visit our Education & Outreach page to find the newest tools!
  2. Participate in habitat restoration efforts to restore habitats that help mitigate the effects of coastal acidification
  3. Facilitate conversations with local businesses that might be affected by ocean acidification, building a plan for the future.
  4. Partner with local community efforts to mitigate the driver behind ocean acidification  – excess CO2 – such as community supported agriculture, bike & car shares and other public transportation options.
  5. Contact your regional Coastal Acidification Network (CAN) to learn how OA is affecting your region and more ideas about how you can get involved in your community
       More for Taking Community Action