Transport of antarctic waters in the deep channels of the Atlantic Ocean

Abstract

Starting from 2002, the Shirshov Institute of Oceanology has been conducting investigations of Antarctic water transport in deep channels of the Atlantic Ocean, namely, the Vema Channel (31 ° S), Romanche Fracture Zone (0 ° N), and Vema Fracture Zone (11 ° N). The flow of bottom water in the Vema Channel is estimated as 4 Sv (1 Sv = 10 6 m 3 /s). Velocities in the channel reach 60 cm/s. A strong flow with velocities up to 30 cm/s was recorded in the Vema Fracture Zone. This flow includes the upper part of bottom waters of Antarctic origin and the lower part of North Atlantic Deep waters. The easterly transport of Antarctic waters is 0.1–0.7 Sv. In the Romanche Fracture Zone, maximum velocities reach 10 cm/s, while the entire easterly water transport is estimated as 0.1–0.8 Sv. The dominating propagation of Antarctic waters into the deep basins of the Northeast Atlantic occurs through the Vema Fracture Zone but not through the Romanche Fracture Zone due to strong mixing of deep waters in the latter channel caused by internal tidal waves. Bottom waters are formed at polar latitudes of the World Ocean. In the classic work by Wust [15], all waters of Antarctic origin are called Antarctic Bottom Waters (AABW). They propagate near the bottom in the Atlantic, being formed mainly in the Weddell Sea near the Antarctic slope as a result of mixing of cold and heavy Antarctic Shelf Water with lighter and warmer more saline Circumpolar Deep Waters. The pathways of Antarctic water propagation between the basins of the Atlantic are confined to depressions in the bottom topography. Antarctic Bottom Water from the Weddell Sea propagates through four passages in the South Scotia Ridge and through the South Sandwich Trench. The further propagation of AABW to the north into the Argentine Basin occurs through the Falkland Gap in the Falkland Ridge [14]. Part of this flow propagates along the southern and western margins of the Argentine Basin. The other part is trapped by the Subantarctic Front and flows to the east in the field of the Antarctic Circumpolar Current [14]. The waters of Antarctic origin are later transported to the Brazil Basin along three pathways: in the Vema Channel, in the Hunter Channel, and over the Santos Transport of Antarctic Waters in the Deep Channels of the Atlantic Ocean