Continental shelf pump

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Continental shelf pump

In oceanic

Ocean

An ocean is a major body of Seawater, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a World Ocean that is customarily divided into several principal oceans and smaller seas....
biogeochemistry

Biogeochemistry

The field of biogeochemistry involves science of the chemistry, physics, geology, and biology processes and reactions that govern the composition of the natural environment , and the cycles of matter and energy that transport the Earth's chemical components in time and space....
, the continental shelf pump is proposed to operate in the shallow waters of the continental shelves

Continental shelf

The continental shelf is the extended perimeter of each continent and associated coastal plain, and was part of the continent during the glacial periods, but is undersea during Ice age such as the current epoch by relatively shallow seas and Bay....
, acting as a mechanism to transport carbon

Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
(as either dissolved or particulate material) from surface waters to the interior of the adjacent deep ocean.

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

Solubility pump

In oceanic biogeochemistry, the solubility pump is a physico-chemical process that transports carbon from the ocean's surface to its interior....
and biological

Biological pump

In oceanic biogeochemistry, the biological pump is the sum of a suite of biologically-mediated processes that transport carbon from the surface euphotic zone to the ocean's interior....
pumps interact with a local hydrography

Hydrography

Hydrography focuses on the measurement of physical characteristics of waters and marginal land. In the generalized usage, "hydrography" pertains to measurement and description of any waters....
that feeds dense water from the shelf floor into sub-surface (at least subthermocline

Thermocline

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In oceanic

Ocean

Biogeochemistry

Continental shelf

Carbon

Overview

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

Solubility pump

In oceanic biogeochemistry, the solubility pump is a physico-chemical process that transports carbon from the ocean's surface to its interior....
and biological

Biological pump

Hydrography

Thermocline

The thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below....
) waters in the neighbouring deep ocean. Tsunogai et al.s (1999) original work focused on the East China Sea
East China Sea

The East China Sea is a marginal sea east of China. It is a part of the Pacific Ocean and covers an area of 1,249,000 km?. In China, the sea is called the East Sea....
, and the observation that, averaged over the year, its surface waters represented a sink for carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
. This observation was combined with others of the distribution of dissolved carbonate
Carbonate

In chemistry, a carbonate is a salt or ester of carbonic acid....
and alkalinity
Alkalinity

Alkalinity or AT is a measure of the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate....
and explained as follows :

the shallowness of the continental shelf restricts convection
Convection

Convection in the most general terms refers to the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer....
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
Solubility pump

In oceanic biogeochemistry, the solubility pump is a physico-chemical process that transports carbon from the ocean's surface to its interior....
and lead to an increased storage of dissolved inorganic carbon
this extra carbon storage is augmented by the increased biological production characteristic of shelves
the dense, carbon-rich shelf waters sink to the shelf floor and enter the sub-surface layer of the open ocean via isopycnal
Isopycnal

An isopycnal is a surface of constant potential density of water. In the ocean, as the depth increases, so too does the density. Varying degrees of salinity and temperature act to modify the density of water, and the denser water always lies below the less dense water....
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
Carbon cycle

The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere of the Earth....
.

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

Sea ice is formed from ocean water that freezes. Because the oceans consist of saltwater, this occurs at about -1.8 ?Celsius .Sea ice may be contrasted with icebergs, which are chunks of ice shelf or glaciers that calve into the ocean....
results in the extrusion
Extrusion

Extrusion is a process used to create objects of a fixed cross section profile. A material is pushed or drawn through a Die of the desired cross-section....
of salt that may increase seawater density. Similarly, in tropical regions, evaporation
Evaporation

Evaporation is the slow vaporization of a liquid and the reverse of condensation. A type of phase transition, it is the process by which molecules in a liquid State of matter spontaneously become gaseous ....
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).

Continental shelf pump

Overview

Significance

See also