Sidedness of Divergence as a Key to Understanding Southern Ocean Upwelling in the Overturning Circulation of the Oceans

Volume 2 - Issue 4

L Bruce Railsback*

Received: February 01, 2019;   Published: February 11, 2019

DOI: 10.32474/MAOPS.2019.02.000143

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Abstract

Sidedness of divergence helps resolve a present discordance in our understanding of upwelling in the Southern Ocean, and thus it contributes to the evolving recognition of the oceans’ overturning circulation. Divergence can be two-sided (one water mass rises and moves apart in two flows, as is commonly envisioned) or one-sided (one water mass rises and moves away from another that does not move in the opposite direction). Upwelling in the Southern Ocean can be envisioned as a one-sided divergence north of a two-sided divergence. In the more northern one-sided divergence, deep to intermediate waters above or from North Atlantic Deep Water (NADW) upwell into the Antarctica Circumpolar Current (ACC) and move north. In the more southern and two-sided divergence, North Atlantic Deep Water (NADW) upwells and diverges southward into the Antarctic Coastal Current (ACoC) or Polar Current (PC) and northward into the ACC, mixing with the waters upwelled in the northern divergence. Understanding the northern upwelling as one-sided and the southern as two-sided thus eliminates an either/or conundrum that has evolved in the literature. It also allows the two modes of Southern Ocean upwelling (northern in the ACC and southern in the Antarctic Divergence) to be seen in the same comparative light as the two modes of upwelling postulated at global scale (upwelling in the Southern Ocean and upwelling or vertical mixing in the Indo-Pacific): in each comparison, the former involves the greater flux of water, whereas the latter involves water richer in geochemical tracers indicative of greater time and/or distance traveled at depth.

Keywords:Convergence; Divergence; Upwelling; Southern Ocean; Antarctica Circumpolar Current; Antarctic Coastal Current; Polar Current; Antarctic Divergence, North Atlantic Deep Water; Circumpolar Deep Water, Overturning circulation; Atlantic meridional overturning circulation; Sidedness, Great Ocean Conveyor, Plate tectonics, Troposphere

Abbreviations:AABW: Antarctic Bottom Water, ACC: Antarctic Circumpolar Current, ACoC: Antarctic Coastal Current, CDW: Circumpolar Deep Water, DIC: Dissolved inorganic carbon, NADW: North Atlantic Deep Water, PC: Polar Current

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