ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

biogeochemistry Biogeochemistry is the scientific discipline that involves the study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment (including the biosphere, the cryosphere, t ...

, the continental shelf pump is proposed to operate in the shallow waters of the

continental shelves A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

, acting as a mechanism to transport

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

(as either dissolved or particulate material) from surface waters to the interior of the adjacent deep ocean.

Overview

Originally formulated by Tsunogai ''et al.'' (1999), the pump is believed to occur where the

solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...

and

biological Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary in ...

pumps interact with a local

hydrography Hydrography is the branch of applied sciences which deals with the measurement and description of the physical features of oceans, seas, coastal areas, lakes and rivers, as well as with the prediction of their change over time, for the primary p ...

that feeds dense water from the shelf floor into sub-surface (at least subthermocline) waters in the neighbouring deep ocean. Tsunogai ''et al.s (1999) original work focused on the

East China Sea The East China Sea is an arm of the Western Pacific Ocean, located directly offshore from East China. It covers an area of roughly . The sea’s northern extension between mainland China and the Korean Peninsula is the Yellow Sea, separated b ...

, and the observation that, averaged over the year, its surface waters represented a sink for

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

. This observation was combined with others of the distribution of dissolved

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

and

alkalinity Alkalinity (from ar, القلوي, al-qaly, lit=ashes of the saltwort) is the capacity of water to resist acidification. It should not be confused with basicity, which is an absolute measurement on the pH scale. Alkalinity is the strength of ...

and explained as follows : * the shallowness of the continental shelf restricts

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

of cooling water * as a consequence, cooling is greater for continental shelf waters than for neighbouring open ocean waters * this leads to the production of relatively cool and dense water on the shelf * the cooler waters promote the

solubility pump In oceanic biogeochemistry, the solubility pump is a physico-chemical process that transports carbon as dissolved inorganic carbon (DIC) from the ocean's surface to its interior. Overview The solubility pump is driven by the coincidence of tw ...

and lead to an increased storage of dissolved inorganic carbon * this extra carbon storage is augmented by the increased biological production characteristic of shelvesWollast, R. (1998). Evaluation and comparison of the global carbon cycle in the coastal zone and in the open ocean, p. 213-252. In K. H. Brink and A. R. Robinson (eds.), ''The Global Coastal Ocean''. John Wiley & Sons. * the dense, carbon-rich shelf waters sink to the shelf floor and enter the sub-surface layer of the open ocean via

isopycnal Isopycnals are layers within the ocean that are stratified based on their densities and can be shown as a line connecting points of a specific density or potential density on a graph. Isopycnals are often displayed graphically to help visualize " ...

mixing

Significance

Based on their measurements of the CO₂ flux over the East China Sea (35 g C m⁻² y⁻¹), Tsunogai ''et al.'' (1999) estimated that the continental shelf pump could be responsible for an air-to-sea flux of approximately 1 Gt C y⁻¹ over the world's shelf areas. Given that observational and modelling of anthropogenic emissions of CO₂ estimates suggest that the ocean is currently responsible for the uptake of approximately 2 Gt C y⁻¹, and that these estimates are poor for the shelf regions, the continental shelf pump may play an important role in the ocean's

carbon cycle The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere, atmosphere of the Earth. Carbon is the main component of biological compounds as well as ...

. One caveat to this calculation is that the original work was concerned with the hydrography of the East China Sea, where cooling plays the dominant role in the formation of dense shelf water, and that this mechanism may not apply in other regions. However, it has been suggested that other processes may drive the pump under different climatic conditions. For instance, in polar regions, the formation of

sea-ice Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oc ...

results in the

extrusion Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...

of salt that may increase seawater density. Similarly, in tropical regions,

evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...

may increase local salinity and seawater density. The strong sink of CO₂ at temperate latitudes reported by Tsunogai ''et al.'' (1999) was later confirmed in the Gulf of Biscay, the Middle Atlantic Bight and the North Sea. On the other hand, in the sub-tropical South Atlantic Bight reported a source of CO₂ to the atmosphere. Recently, work has compiled and scaled available data on CO₂ fluxes in coastal environments, and shown that globally marginal seas act as a significant CO₂ sink (-1.6 mol C m⁻² y⁻¹; -0.45 Gt C y⁻¹) in agreement with previous estimates. However, the global sink of CO₂ in marginal seas could be almost fully compensated by the emission of CO₂ (+11.1 mol C m⁻² y⁻¹; +0.40 Gt C y⁻¹) from the ensemble of near-shore coastal ecosystems, mostly related to the emission of CO₂ from estuaries (0.34 Gt C y⁻¹). An interesting application of this work has been examining the impact of

sea level rise Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...

over the last de-glacial transition on the global carbon cycle. During the last glacial maximum sea level was some lower than today. As sea level rose the surface area of the shelf seas grew and in consequence the strength of the shelf sea pump should increase.

Overview

Significance

References

See also