Carbon Sequestration in the Oceans

by Jack Jurke

What are the oceans roles in carbon sequestration? How does climate change limit the ocean’s capacity to?


Lina's response:
Oceans are a major component in maintaining the delicate balance of the carbon cycle. The Earth's Oceans and current circulation (ocean conveyor belt), land mass (forests, deserts,etc), ice mass (polar ice caps), and the atmosphere (all layers), all interact dynamically to maintain the balance of sources and sinks for carbon. With more industrial activity, more carbon is released into the atmosphere (source) than can be absorbed (sink).

Looking at carbon sequestration, where carbon is effectively held in storage, the oceans sequester carbon in various ways. One method includes transporting carbon absorbed from the atmosphere from shallow to intermediate to deep water through the ocean conveyor belt, one of the most important controllers of the earth’s thermostat. This conveyor belt is driven by differences in temperature, density, and salinity.

To put it very simplistically, shallow waters are chilled in the cold North Atlantic Ocean and sink downward. They are then driven through current circulation layers around the globe in a complex path that can take about a thousand years to complete (the time it takes for surface water to sink down, circulate, and re-emerge to the surface). Colder, denser or more salty waters sink, carrying with them the surface layers that are carbon rich, and expose “newer” waters that resurface.

The carbon-rich water supports marine ecology, especially plants (food chain) and coral (another crucial carbon sink). The health of coral is vitally dependent on appropriate levels of carbon.

Ok, keeping with the simplistic view, if there are more carbon sources than sinks, then the resulting greenhouse effect would create a temperature rise. Even a few degrees would have significant results on the Earth’s dynamic systems. For one, the warming would cause polar ice caps to thaw (as is evident in the past few decades), adding freshwater in the polar regions. Diluting the saltiness of the waters, along with the continued warming of the waters will wreak havoc with the conveyor belt which is driven mainly by differences temperature, density, and salinity. This means that carbon cannot sink properly. In addition, warmer waters cannot absorb gasses as effectively. Enough dilution and warming can possibly halt the conveyor belt.

The warming effect is also unhealthy for marine - and land - ecology. Marine life in different regions depends on specific environments to maintain existence. Warmer waters lead to disruption in the food chain, and destroy valuable coral. Also, water temperatures affect wind and weather patterns, which in turn, affect the forests and deserts, and so on. As you can see, all the components (land, water, ice, atmosphere) respond to each other in a “feedback loop”, where a change in one area can affect several others in a ripple effect. It is difficult to predict how everything will eventually settle, or reach a new dynamic equilibrium. What is becoming obvious is the recent erratic behavior of weather and its consequences around the world.

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