Environment and Ecology Research Vol. 8(1), pp. 1 - 28
DOI: 10.13189/eer.2020.080101
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Driving Forces and Flow Mechanisms of the Atlantic Ocean Currents


Kari Hänninen *
Department of Biological and Environmental Sciences, University of Jyväskylä, Finland

ABSTRACT

The aim of the study is to clarify the driving forces and flow mechanisms of ocean currents. The primary driving forces of the surface currents are the thrust by the trade winds and westerlies. For the undercurrents, the driving force is the thrust of descending salty water (DSW) formed in the Arctic and Southern Oceans by brine ejection from ice. The annual production of DSW in the Arctic Ocean is 21.7 Sv and in the Southern Ocean 26 Sv. The annual average downward thrust created for the outflowing undercurrents in both oceans is 44,000 N/m2. Most of the DSW outflow from the Arctic Ocean occurs via the Labrador Sea towards the coast of northwest Africa as the North Atlantic Undercurrent (NAUC). The direction of the flow is towards the suction at the starting point of the North Equatorial Current. The flow and the fluid dynamics of the NAUC follow Pascal's law and Bernoulli's equation. Upwelling provides an unobstructed passage for the continuous flow of an undercurrent. The water molecules moving along streamlines trade speed for height or for pressure. Due to this exchange, the flow of the NAUC slows and the flow bed widens. Subsequently, it upwells along the 3,500 km of coastal area from A Coruña (NW Spain) to Dakar (NW Africa). In the abyssal oceans, the mixing of water is relatively weak and intermittent, driven by double diffusive convection (DDC). The phenomenon known as salt fingering is typical for the DDC. However, the DDC is vigorous where the temperature difference between warm water and the cold water below is great, like in the confluence of the Brazil vs. Malvinas currents. Then salt fingers which are several hundred meters deep and several hundred kilometres wide are formed. In these salt fingers, the water of the warm current downwells and the water of the cold current upwells. This slows down the horizontal movement of the water molecules in both currents.

KEYWORDS
Brine Ejection from Ice, Downward Thrust of Descending Salty Water, Suction of the Gulf Stream, North Atlantic Undercurrent, Double Diffusive Convection, Salt Fingering, Confluence of Brazil and Malvinas Currents

Cite This Paper in IEEE or APA Citation Styles
(a). IEEE Format:
[1] Kari Hänninen , "Driving Forces and Flow Mechanisms of the Atlantic Ocean Currents," Environment and Ecology Research, Vol. 8, No. 1, pp. 1 - 28, 2020. DOI: 10.13189/eer.2020.080101.

(b). APA Format:
Kari Hänninen (2020). Driving Forces and Flow Mechanisms of the Atlantic Ocean Currents. Environment and Ecology Research, 8(1), 1 - 28. DOI: 10.13189/eer.2020.080101.