In:
Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 104, No. C9 ( 1999-09-15), p. 21033-21049
Abstract:
This systematic study of the subtropical mode waters in the South Atlantic is based on hydrological data (the basin‐wide South Atlantic Ventilation Experiment, Oceanus, and Ajax sections, and the World Ocean Circulation Experiment (WOCE) sections in the Brazil‐Malvinas Confluence region), the WOCE expendable bathythermograph data set, and the atmospheric forcing produced by the National Centers for Environmental Prediction reanalysis. The main ventilation window of the subtropical gyre lies in the southwest and corresponds to the southern part of the recirculation region and to the overshoot of the Brazil Current (BC). Some ventilation occurs along the southern branch of the gyre through deep mixed layers in harsh winters and in the east through the rings shed by the Agulhas Current. However, the ventilation from the eastern border concerns a small volume of water with highly variable characteristics. Three main types of subtropical mode water are observed: the lightest around the 26.2 density surface and the second and third around the 26.5 and 26.7 density surfaces, respectively. The 26.2 subtropical mode water (STMW1) corresponds to potential temperatures between 16° and 18°C and salinities between 35.9 and 36.2. The STMW1 thickness does not exceed 150 m. The volume of the 26.5 mode water (STMW2) is larger. It is produced through the formation of deep mixed layers (reaching 300 m or more) in the active ventilation window over the BC overshoot. Its potential temperature ranges between 14° and 16°C, and its salinity ranges between 35.5 and 35.9. Its thickness can be above 300 m. The last component observed around the 26.7 density surface (STMW3) has a potential temperature between 12° and 14°C and a salinity of about 35.2 to 35.5. It is formed on the eastern flank of the BC overshoot and, during harsh winters, in the center of the southern branch of the gyre. Within the main ventilation window the STMWs exhibit quite a significant variability in characteristics and volume. There is a large interannual variability in the atmospheric forcing over the BC recirculation and BC extension, and the observed variations of the subtropical mode waters are qualitatively correlated to the atmospheric forcing variations.
Type of Medium:
Online Resource
ISSN:
0148-0227
DOI:
10.1029/1999JC900049
Language:
English
Publisher:
American Geophysical Union (AGU)
Publication Date:
1999
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