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COMPLEX CARBON PROCESSES OCEAN - Coggle Diagram
COMPLEX CARBON PROCESSES OCEAN
OCEAN
LARGEST CARBON STORE Oceans are the largest carbon stores ; they are 50 times larger than the atmosphere with 93% of CO2 stored in oceanic algae, plants and coral. Lots of processes occur simultaneously within the ocean to store these large amounts of CO2 . This transfer of CO2 into the sea is called ocean sequestration.
CHANGES
Small changes in oceanic carbon levels can have significant global impacts. The CO2 gas exchange between the atmosphere and ocean operate on different timescales.
LAYERS (TOP)
ocean has different layers, as shown in the diagram below. The majority of the processes which take the CO2 out of the atmosphere and into the ocean occur in the top surface layer which makes up only a small proportion of the water in the world’s ocean. The carbon rich water in the surface layer is then transferred down into the lower layers of the ocean and transported around the world due to thermohaline circulation. It is this circulation which allows such large amounts of carbon to be stored in the sea.
BIOLOGICAL CARBON PUMP
Phytoplankton are microscopic organisms that, like plants, photosynthesise. They take in carbon and turn it into organic matter. As they are the base of the marine food web (half of the planet’s biomass consist of phytoplankton despite their microscopic size) when they get eaten, carbon is passed through the food chain. Remember that CO2 is also released back into the water as these organisms respire. Some organisms like Plankton sequester CO2 , turning the carbon into their hard outer shells and inner skeletons. When these organisms die, some of their shells dissolve into the ocean water meaning the carbon becomes part of deep ocean currents.
dead organisms which sink to the seafloor become buried and compressed, eventually forming limestone sediments (sedimentation). Over a long time period these can turn into fossil fuels. At the same time, some CO2 from the atmosphere will naturally by dissolving into the water. This process occurs on the surface of the oceans where CO2 reacts with water to form carbonic acid. As the concentrations of CO2 in the atmosphere increase, oceans absorb more CO2 causing them to become more acidic. This acidification of the oceans could have long lasting negative effects. This movement of CO2 isn’t one way, some will go from the water back into the atmosphere.
PHYSICAL PUMP There would come a point where the surface layer of the ocean would become so saturated with carbon that this process would slow down or stop occurring. (If you add salt to a cup of water there is a finite amount of salt which can be dissolved into the water). However, oceanic circulation provides a constant source of new water on the surface while transferring surface water into the deep ocean. It is this process which enables the ocean to store so much carbon. Water is not stored evenly within the water; the colder the water, the more CO2 is absorbed so the concentration of CO2 in the ocean is different around the world.
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CO2 concentration is 10% higher in the deep ocean compared to the surface of theOCES
Polar regions hold more carbon than tropical regions.
walm tropical water releases co2 to the atmosphere but cold high latitude oceans absorb CO2 from the atmosphere
THERMOHALINE CIRCULATION Thermohaline circulation is an ocean current that produces both vertical and horizontal circulation of cold and warm water around the world’s oceans. In addition to this, the atmospheric circulation creates large currents in the oceans which transfers water from the warmer tropical areas of the world to the colder polar regions. The rate of circulation is slow; it takes around 1000 years for any cubic metre of water to travel around the entire system. Warm surface waters are depleted of CO2 and nutrients therefore the foundation of the planet’s food chain depends on cool and nutrient rich water which support algae to grow. Water in the North Atlantic is cold and very saline which means it is denser and heavier causing it to sink. When the cold water sinks, warm water is drawn from the ocean surface. Eventually cold water is drawn from the bottom of the ocean and then warmed up.
1.The main current begins in polar oceans where the water is very cold, surrounding seawater sinks due to a higher density
2.The current is recharged as it passes Antarctica by extra cold, salty, dense water.
Division of the main current; northward into the Indian Ocean and into the Western pacific
The two branches warm and rise as they travel northward then loop back southward and wesward
The now warmed surface waters continue circulating around the globe. On their eventual return to the North Atlantic they cool and the cycle begins again.
RATE OF CO2 ABSORBTION The rate of absorption of CO2 into the ocean depends on ocean temperatures. The colder the water, the more CO2 is absorbed. Therefore, as ocean temperatures increase, the oceans will absorb less CO2 (possibly even emitting some of its stored carbon dioxide). This would accelerate Climate Change and lead to further ocean warming (positive feedback mechanism).
ROLE The role of the oceans in regulating climate and greenhouse gas emissions is essential to the erath