The subantarctic and polar fronts in relation to deep water masses through the southwestern Atlantic

• Published in: Journal of Geophysical Research
• Main Authors: Peterson, R., Whitworth, T.
• Format: Book
• Language: English
• Published: 1989
• Subjects: Antarctic; Argentine; Drake Passage; Ewing; Falkland Plateau; Falkland Ridge; Georgia Basin; Islas Orcadas Rise; Orcadas; Orcadas Rise; Pacific; Scotia Sea; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/1834/17231; https://doi.org/10.1029/JC094iC08p10817

The two principal fronts within the Antarctic Circumpolar Current (ACC), the Subantarctic Front (SAF) and the Polar Front (PF), are investigated with respect to their spatial patterns and relations to deep water masses from the northern Drake Passage to the western and southern Argentine Basin. Observations from four recent cruises in adjoining and overlapping regions are supplemented with satellite infrared imagery and trajectories from surface drifters. East of Drake Passage, the width of the Polar Frontal Zone (PFZ) increases rapidly when the SAF turns sharply northward as a part of the Falkland (Malvinas) Current, while the PF remains oriented mainly toward the northeast. Found within this region of the PFZ are mesoscale eddies, the upper layers of which consist of Subantarctic Mode Water from the Pacific. The contrasts in upper layer water properties that identify the SAF can be traced the entire length of the Falkland Current to the Brazil‐Falkland confluence zone and then southward to the southern Argentine Basin. There the SAF turns eastward and later, but perhaps not always, merges with the PF north of Ewing Bank to form a single, intense current core strongly influenced by bottom topography. At times this eastward current loops southward through a gap in the Falkland Ridge into the Georgia Basin, thereby supplying relatively warm and salty Subantarctic water to the Antarctic Zone. East of the gap, the two fronts become separated and are once again distinct features in the vicinity of the Islas Orcadas Rise. At depth, within Drake Passage and the western Scotia Sea, the SAF and PF are not lateral boundaries between distinct water masses, but are instead identified by enhanced vertical displacements of property isopleths. With the northward turn of the SAF east of Drake Passage, a thick layer of Circumpolar Deep Water (CDW) is advected over the Falkland Plateau into the Argentine Basin. There it is joined by waters entering the Argentine Basin via a deep spreading route through the Georgia Basin: denser ...