Why and How to Incorporate Ocean Studies in Climate Change Education?
World Ocean Day offers a prime opportunity to showcase the significance of the ocean theme within climate change education. The ocean and climate are intricately linked: the ocean acts as a climate regulator and carbon sink, playing a pivotal role in the climate system. However, it suffers greatly for providing these services, experiencing increased temperatures, sea levels, and acidity. These changes adversely affect biodiversity, the economy, and the climate itself. Moreover, the ocean is deeply embedded in our culture, diet, economy, and hobbies. Studying the ocean thus provides a chance to address these topics in the classroom, a theme that becomes even more critical if you teach in a coastal municipality or are among those who have the opportunity to take their students on sea-oriented field trips.
The OCE team offers insights into the "Ocean and Climate" subject, along with several educational resources and activity ideas for your class.
1. The Ocean as a Climate Regulator
Oceanic Circulation
The ocean absorbs most of the solar radiation that reaches Earth. This heat, received more intensively at the equator, is redistributed globally through oceanic circulation, driven by winds that generate surface currents, and by variations in water density, which give rise to thermohaline circulation. Indeed, the denser the sea water—either colder or saltier—the deeper it sinks. This process mainly occurs in high latitudes, where heat loss to the atmosphere and sea ice formation lead to significant changes in temperature and salinity. This circulation forms a loop: in the Atlantic, where it is most intense, warm surface waters move northward across the equator, before cooling and sinking to the ocean floor at high latitudes. These deep waters then travel southward, crossing the equator again to join the Southern Ocean around Antarctica, before rising to the surface centuries later, and rejoining the Atlantic surface currents. This is known as the meridional overturning circulation. Its strength plays a crucial role in regulating the global climate. With climate change, surface waters become warmer and less dense; moreover, the melting of polar ice caps introduces fresh water into the surface waters at high latitudes, thereby weakening this circulation.
Stratification and Deoxygenation in the Ocean
In the ocean, water masses are arranged in layers according to their density, which varies based on salinity and temperature. This layering is known as ocean stratification. With climate change, surface waters are becoming warmer and less dense compared to deep waters. This increase in density and temperature contrasts between surface and deep waters alters the mixing between layers, disrupting the exchange of oxygen and nutrients.
By 2090, in all scenarios analysed by the IPCC, projections indicate a decline in the levels of oxygenation and nutrients in the ocean, which will significantly impact marine life.
Pedagogical Resources
- The Regulatory Role of the Ocean on Climate - Sébastien Carassou
- The Oceanic Machine - Sébastien Carassou
- Thermohaline Circulation Explained by Oceanographer Jean-Baptiste Sallée | CLIM
Class Activities
- Ocean's thermal inertia and climate regulation (advanced students)
- Marine Currents and Climate Regulation (Advanced Students)
El Niño and the Meridional Overturning Circulation
Some years, abnormal warming occurs in the central and eastern Pacific Ocean. This phenomenon, known as El Niño, results from an atypical exchange of energy between the ocean and the atmosphere and occurs regularly, every few years. It causes significant variations in wind and rainfall patterns, with major consequences for humans and the environment globally. Along the coasts of Peru and Chile, the normally abundant fishing halts during El Niño as the nutrients carried by the cold deep waters fail to reach the surface to feed the fish. In the Western Pacific, the typically heavy rains shift further east, causing devastating droughts in Indonesia, the Philippines, and Australia. The summer monsoons, which half the world's population relies on, are disrupted, particularly in China, India, Australia, the Sahel, and Brazil.
Scientists estimate that extreme El Niño events may occur more frequently during the 21st century due to ocean warming.
Pedagogical Resources
- What is the Phenomenon of El Niño and How to Teach it?
- El Niño Explained by Oceanographer Eric Guilyardi | CLIM
2. The Ocean as a Heat Sink
The ocean serves as a significant heat sink, absorbing over 90% of the excess heat from global warming. Without this capacity, which is due to the thermal inertia of water, we would have already significantly surpassed the 1.5°C warming limit targeted by the Paris Agreement.
Thermal Inertia
Water, with its high resistance to thermal changes, can absorb a substantial amount of energy before it heats up and can release a large amount of energy before cooling down. This property helps mitigate local climate variations and explains the considerable difference between oceanic and continental climates. However, it does not prevent the gradual warming of the oceans. Scientists currently estimate that ocean warming, and thus the heat absorbed, has more than doubled since 1993, affecting both surface and deep waters.
Class Activities
Ocean Warming
The occurrence of extreme heat events on the ocean's surface, known as marine heatwaves, has doubled in frequency over the past 40 years and has become longer, more intense, and more widespread. By the end of the 21st century, marine heatwaves are expected to occur 20 to 50 times more frequently depending on the scenarios.
Furthermore, the ocean's high thermal inertia and its vast volume mean that even if human emissions of greenhouse gases were to cease tomorrow and the ocean absorbed less heat, it would take millennia for the ocean to cool down and return to its pre-industrial temperature.
Sea Level Rise
Like all liquids, water expands when heated. Therefore, the warming of the ocean leads to the thermal expansion of water, which occupies a larger volume. Combined with the melting of ice caps and glaciers, this thermal expansion results in a global average sea level rise. It is estimated that the sea level has already risen by 16 cm over the last century and continues to rise at an accelerating rate. The rate of increase between 2006 and 2015 was 3.6 mm per year, which is 2.5 times higher than the rate from 1901 to 1990. While a few millimetres of rise per year might seem minor, they accumulate over time and lead to more frequent extreme flooding in coastal regions. They also exacerbate the impacts of storms and coastal erosion.
Due to the thermal inertia of the ocean, sea levels will continue to rise even after global temperatures have stabilised. This trend could be further amplified by the melting of the Antarctic ice cap.
Pedagogical Resources
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Multimedia Activity "Sea Level Rise”
- Video: Sea Level Rise explained by the Oceanographer Angélique Melet
Class Activities
3. The Ocean as a Carbon Sink
Carbon Sequestration
The ocean functions as what is known as a carbon sink, capable of capturing atmospheric CO2 through the synergy of two processes, one physical and the other biological. Firstly, atmospheric CO2 naturally dissolves in the ocean, a process enhanced by low temperatures. Since cold water is denser, it sinks, carrying the dissolved CO2 with it—this is known as the physical carbon pump. Secondly, phytoplankton absorb CO2 through photosynthesis, constituting the biological pump. Thanks to these two mechanisms, the ocean sequesters about 30% of the CO2 emitted by humans, approximately 38 million tons of CO2 per day. This is 16 times more than all of the earth's soil and terrestrial plants combined, and nearly 60 times more than the atmosphere.
Ocean Acidification
The downside of CO2 absorption by seawater is an increase in ocean acidity, a phenomenon known as acidification. When CO2 dissolves in seawater, it forms carbonic acid which, through chemical reactions, releases various ions. These reactions lead to an increase in hydrogen ion concentration, causing acidification, and a decrease in carbonate ion concentration. These carbonate ions are crucial for the formation of mollusk shells and coral skeletons, which are composed of calcium carbonate. In a more acidic environment, corals, shellfish, and mollusks face developmental challenges. Globally, the average pH of the ocean has decreased by about 0.1 units since the industrial revolution, now standing at approximately 8.05. It's important to note that while a pH of 7 is considered neutral, the ocean's baseline is naturally higher. Any reduction in pH can impact the calcification processes of some marine organisms during their development. Therefore, even a pH drop that remains above 7 can have significant repercussions.
Pedagogical Resources
Class Activity
4. Ocean and Biodiversity
The ocean harbours a rich biodiversity concentrated in "niches" such as coral ecosystems. Microscopic, photosynthetic unicellular organisms known as phytoplankton form the base of most marine food chains and are consumed by often microscopic animals called zooplankton. At the top of these food chains are sharks and marine mammals like seals and whales. Any alteration within this chain has repercussions throughout the entire food web. Ocean acidification, deoxygenation, marine heatwaves, and pollution thus pose direct or indirect threats to the entirety of marine biodiversity, especially since the rapid pace of these phenomena does not allow different species sufficient time to adapt.
According to the IUCN Red List update, climate change is impacting at least 41% of the assessed marine species that are threatened with extinction, highlighting a critical situation for global marine biodiversity
Class activity
5. Ocean and Humans
A Society Largely Oriented Towards the Sea
It is estimated that about 600 million livelihoods depend at least partially on fisheries and aquaculture.
- In many regions, tourism is by far the primary employment sector within the maritime economy. Fishing, aquaculture, and related industries also represent significant employment areas. Shipbuilding and boat repair are other notable sectors, as is maritime transport of passengers and goods.
Other economic aspects to consider include:
- Fishing as a vital food resource;
- The ocean also provides us with energy, including wave and tidal energy, which are renewable sources, as well as oil, gas, and minerals found in the rocks of the ocean floor;
- 37% of the world's population lives within 100 km of the coast.
Moreover, the ocean is prominently featured in our literature and in a number of local traditions and cultures (sea festivals, sea shanties, tales, etc.) or major recurring events (sailing races, festivals, etc.).
Consequences of Climate Change
The effects of climate change on the ocean will have significant impacts on coastal populations and the economies of these areas:
- Sea level extremes (such as century floods), caused by rising sea levels and typically occurring during storms (which themselves are becoming more intense), will become increasingly frequent. Approximately 10% of the global population resides in low-lying coastal areas, placing them at heightened risk from these rising sea levels.
- The dwindling or disappearance of certain species, particularly due to ocean acidification and the increase in marine heatwaves, will have repercussions on fishing.
A slowdown in sea level rise, or any other consequence of climate change, would provide greater opportunities for adaptation, hence the necessity to also reduce greenhouse gas emissions.
Pedagogical Resources
Class activity
- Consequences of Climate Change on Ecosystem Services
- Ocean and Cryosphere Cultural Services
- Increasing Beach Resilience to Climate Change
In conclusion, the theme of the ocean can be explored beyond just the natural sciences such as biology and environmental science. It encompasses literature, economics, history, and geography, allowing for a systemic approach to the topic of climate change. The ocean, deeply embedded in our collective unconscious, is particularly well-suited for awareness or adaptation projects, as well as for projects that promote scientific inquiry through observation, measurement, and analysis.