Click on the images in the carousel below to learn more about increasing levels of dissolved carbon dioxide in the ocean

This interactive map below shows the values for the 'partial pressure of carbon dioxide' pCO₂ (units = μatm). Put simply, this is a measure of the amount of carbon dioxide dissolved in seawater. It is expressed in micro atmosphere (μatm or muatm), which is a unit of pressure. The measurements were recorded during The Ocean Race Europe and for Amberail-2, during the Prologue and delivery from Lithuania through to France. Use the tools in the upper right to zoom in on the map. Ocean pCO₂ concentration can be compared to atmospheric CO₂ (measured as parts per million, ppm) to estimate air-sea flux of CO₂ and this is used to assess whether the ocean is acting as a sink or source of CO₂ to the atmosphere. The air-sea carbon dioxide exchange is a critical process in the study of climate change.

Sea surface temperature (SST) is an essential component of the climate system as it influences the exchanges of energy and gases between the ocean and atmosphere. Sea surface temperature (SST) measured during The Ocean Race Europe reflect the expected pattern: coldest SST in Baltic Sea waters with an increase as the boats moved south into the Atlantic Ocean, and warmest SST in the Mediterranean Sea.

Looking in more detail into existing science it has been recorded that in the Mediterranean Sea Surface Temperature [SST] has increased by an average of 1.27 deg C over a 35 year study period [1982 - 2016] ⁹. This warming has been linked to intensified heavy precipitation events both regionally and also in Central Europe ¹⁰ and the Sahel ¹¹. Rising Mediterranean SST has is also known to play a role in the intensification and persistence of European heatwaves ⁹.

In the longer term, as the ocean warms, a negative feedback loop develops: less carbon dioxide can be absorbed by the warmer sea waters, and global warming is exacerbated. Predictions show that quick and intense warming will have an impact on the cycles of carbon exchange between surface and deep waters, and on marine life. ¹²

SST information is typically derived from satellite measurements and numerical modelling simulations, so direct measurements like those provided from The Ocean Race boats offer essential ground-truthing data for to validate and improve models.

⁹ Pastor, F., Valiente, J.A., & Palau, J.L. (2017). Sea Surface Temperature in the Mediterranean: Trends and Spatial Patterns (1982–2016). Pure and Applied Geophysics, 175, 4017-4029.

¹⁰ Volosciuk, C., et al. (2016). Rising Mediterranean sea surface temperatures amplify extreme summer precipitation in Central Europe. Scientific Reports. https://doi.org/10.1038/srep32450.

¹¹ Rowell, D. P. (2003). The impact of Mediterranean SSTs on the Sahelian rainfall season. Journal of Climate, 16, 849–862. https://doi.org/10.1175/1520-0442.

¹² Margirier, F., Testor, P., Heslop, E., Mallil, K., Bosse, A., Houpert, L., Mortier, L., Bouin, M., Coppola, L., D’Ortenzio, F., Durrieu de Madron, X., Mourre, B., Prieur, L.M., Raimbault, P., & Taillandier, V. (2020). Abrupt warming and salinification of intermediate waters interplays with decline of deep convection in the Northwestern Mediterranean Sea. Scientific Reports, 10. (https://www.nature.com/articles/s41598-020-77859-5)

Sea surface salinity (SSS) measurements are important to monitor the water cycle (e.g. evaporation,precipitation). Together with sea surface temperature SST, SSS is also an important indicator and driver of ocean circulation and mixing.

The Mediterranean Sea is one of the saltiest parts of the world’s ocean, up to 38-39 PSU* as shown in this map, while average ocean salinity is 34-36 PSU* (* PSU : Practical Salinity Units). Some causes are very intense evaporation and limited freshwater input from rain and rivers.

The high salinity in the Mediterranean Sea is one of the factors that stimulates mixing with deep water to drive the region’s role as an important carbon sink. Changes in salinity will have an impact on the cycles of carbon exchange between surface and deep waters, and on marine life. ¹²

Chlorophyll-a is green pigment that is found in living organisms, such as plants, phytoplankton, or algae, at the first level of the food chain. Measurements of Chlorophyll-a levels are used as a proxy to monitor the primary production i.e. the level of photosynthesis occurring due to phytoplankton. The photosynthesis uses sunlight and carbon dioxide from the water to produces oxygen. More generally, chlorophyll-a levels are useful to evaluate a water body’s health, composition, and ecological status.

Chlorophyll-a levels naturally fluctuate over time in response to water temperature, lights levels, rainfall and nutrients loads (e.g. from fertilizers, wastewater, aquaculture). In our data, we see elevated Chlorophyll-a levels when boats sailed around Brittany to get to Lorient which is likely associated with a phytoplankton "bloom" (i.e. large increase in phytoplankton concentration), often experienced at this time of the year due to warmer water temperatures and increased sunlight. Another area of high Chlorophyll-a levels is visible off Sagres near the southwestern tip of Portugal. In contrast, Chlorophyll-a levels measured in the Mediterranean Sea are lower than elsewhere. The low levels are explained by the fact that the Mediterranean Sea has very low concentrations of nutrients (notably phosphates), which results in low pythoplankton biomass, low primary production and low chlorophyll-a levels¹ . For these reasons, the Mediterranean Sea is defined as being oligotrophic which essentially means it is a Low Nutrient - Low-Chlorophyll system. Note chlorophyll-a measurements are also interesting to have when sampling microplastics as some studies² suggest possible interaction between phytoplankton and microplastic particles in which phytoplankton can stick to plastic fragments and sink to the seabed.

¹ Powley, H.R., Cappellen, P.V., & Krom, M.D. (2017). Nutrient Cycling in the Mediterranean Sea: The Key to Understanding How the Unique Marine Ecosystem Functions and Responds to Anthropogenic Pressures.

² Long, M., Moriceau, B., Gallinari, M., Lambert, C., Huvet, A., Raffray, J. & Soudant, P. (2015) Interactions between microplastics and phytoplankton aggregates: Impact on their respective fates. Marine Chemistry. 175: 39–46. DOI:10.1016/j.marchem.2 015.04.003