Direct Measurements of the Malvinas Current Velocity Structure

• Published in: Journal of geophysical research. Oceans Vol. 126; no. 4
• Main Authors: Frey, D. I., Piola, A. R., Krechik, V. A., Fofanov, D. V., Morozov, E. G., Silvestrova, K. P., Tarakanov, R. Yu, Gladyshev, S. V.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-04-2021
• Subjects: Antarctic Circumpolar Current; Antarctic front; Boundary currents; Climate change; Continental slope; Current velocity; currents; Fronts; Geophysics; Global climate; Isobaths; Malvinas Current; ocean circulation; Ocean currents; Ocean dynamics; Ocean models; Oceans; Offshore; Polar fronts; SADCP measurements; Satellite imagery; Slopes; Spaceborne remote sensing; Temperature distribution; Velocity; Velocity distribution; velocity structure
• DOI: 10.1029/2020JC016727
• EISSN: 2169-9291
• ISSN: 2169-9275

Direct velocity measurements of the Malvinas Current (MC) were carried out on multiple occupations of five transects across the flow using a Shipborne Acoustic Current Profiler (SADCP) on the R/V Akademik Sergey Vavilov and Akademik Mstislav Keldysh. These data are used to determine local features of the three‐dimensional velocity field of the current. The occupations covered the northern branch of the Antarctic Circumpolar Current (ACC) and the southern part of the MC. Five transects across the flow were located at 350–550 km from each other from the Drake Passage to the western Argentine Basin at 46°S. The new observations reveal that the current is organized in two branches, namely, an inshore branch extending to a depth of 200–300 m and a main offshore branch, which flows approximately over the 1,400 m isobath. This two‐branch structure is observed on each of the cross‐flow transects. The observed velocities of the inshore branch exceed 40 cm/s on each studied crossing of the current. The MC is a cold western boundary current that follows the Subantarctic Front. This flow originates as an offshoot of the northern branch of the ACC and continues over the Falkland/Malvinas Plateau and along the western slope of the Argentine Basin. Volume transports of the upper 700 m of the MC calculated for each crossing range between 1.4 and 4.4 Sv for the inshore branch and between 21.2 and 25.5 Sv for the offshore (main) branch.
Plain Language Summary
The Malvinas Current (MC) is one of the dominant circulation features in the Southwest Atlantic. It originates as the northern branch of the Antarctic Circumpolar Current (ACC) which is the largest ocean current in the global ocean. The ACC plays a significant role in the circulation in the Southern Ocean and our knowledge of its structure is important for understanding ocean dynamics and global climate changes. The ACC consists of three main circumpolar fronts from north to south: The Subantarctic Front (SAF), the Polar Front, and the southern ACC Front. The MC is associated with the SAF over the Falkland/Malvinas Plateau and the continental slope of South America. Its spatial structure has been repeatedly studied based on ocean modeling, reanalysis data, satellite images, and measured distribution of temperature and salinity, but direct velocity measurements of the MC remain quite rare. In this work, we report unprecedented velocity measurements carried out across the current along five transects spanning most of the current. These new data reveal that the current is organized in two branches in its southern part and allow us to calculate their volume transports and maximum speeds.
Key Points
Direct current observations across five Malvinas Current transects are presented
The new observations confirm a two‐jet structure along the current path from northern Drake Passage to 46°S
In the upper 700 m the inshore and main current branches transport 2.4–6.3 Sv and 21.3–25.4 Sv, respectively