How Tara contributes to our knowledge about the relationship between Ocean and Climate

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Ocean and climate form an inseparable couple. One can not think of one without the other. For decades scientists, citizens and politicians have taken a close interest in the evolution of the global climate and its consequences, but the ocean has long been on the sidelines. Not until the COP21 in 2015 did the ocean truly make its entrance as a last-minute guest on the international climate negotiations scene.

An urgent problem, global issues

The ocean modulates the climate as much as it undergoes the consequences of climate change. First of all, the ocean is one of the main architects of the composition of our atmosphere: it absorbs a quarter of our CO2 emissions and produces 50% of the oxygen we breathe. For this reason, the ocean was given the nickname “blue lung”. Via the mechanism of photosynthesis, marine micro-algae provide as much oxygen to the atmosphere as the immense terrestrial forests.

By absorbing a significant portion of atmospheric CO2, the ocean mitigates global warming, but in return, it becomes acidic, threatening organisms with calcareous structures. Since the beginning of the industrial revolution, the acidity of the ocean has increased by 30%. The global increase of atmospheric temperature directly impacts that of oceanic waters, the two being in direct contact. This change in temperature causes rising water levels, worsens the deoxygenation of certain areas of the ocean, and alters the habitats of many marine species, resulting in their death or migration.

One of the main objectives of the scientific project led by the Tara Expeditions Foundation is to understand how the ocean will evolve as a climate player, particularly through the study of plankton. Will a warmer, more acidic, less oxygenated ocean continue to be productive? Will it continue to be a good carbon sink? Or will its effectiveness diminish, accelerating the phenomenon of global warming?

Kuata bay, Fiji _ Credit Noëlie Pansiot - Tara Expeditions Foundation Tara in Kuata bay, Fiji © Noëlie Pansiot – Tara Expeditions Foundation

Better understand the risks of climate change for the ocean

Unfortunately, our meager knowledge of the oceanic ecosystem does not reflect its vital importance for the climate system. This observation motivated the Tara Foundation to organize the Tara Oceans expedition:  for 4 years, teams of scientists aboard the schooner Tara explored oceans all over the globe. The goal was to develop the most comprehensive vision possible of the complex, continuous and interconnected system that is the global ocean.

The enormous quantity of data collected constitutes, first and foremost, a baseline “state of health” of the ocean. This gives us an essential starting point if we want to know exactly how the ocean’s temperature, pH, and oxygen levels are changing, and at the same time understand the composition and functioning of the planktonic ecosystem. Comparing the data collected during the Tara Oceans expedition with future measurements, we can make informed hypotheses about the evolution of the ocean in relation to climate change.

Since climate change is a global problem, affecting all human populations to different degrees, giving free and open access to the Tara Oceans data is a fundamental condition for the project’s success. To achieve this, the Tara consortium scientists are making readable and exploitable the millions of complex and heterogeneous data. They are developing very easy-to-use tools to empower oceanographers, marine biologists and others to make use of the database.

Margaux Gaubert

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