An additional deep-water mass in Drake Passage as revealed by 3He data

• Main Authors: Wolfgang Roethera, David P. Stevensb
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2003
• Subjects: Antarctic; Drake Passage; Greenwich; Pacific; The Antarctic; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.546.1888; http://www.uea.ac.uk/~dps/publications/WRS03.pdf

We present 3He data from a repeat section across Drake Passage, from three sections off the South American continent in the Pacific, at 28S, 35S, and 43S, and from three sections in the Atlantic, eastward of the Malvinas, close to 35W, and near the Greenwich Meridian. In Drake Passage, a distinct high-3He signal is observed that is centered just above the boundary of the Lower and the Upper Circumpolar Deep Water (LCDW, UCDW), and is concentrated towards the northern continental slope. 3He concentrations in the Antarctic Circumpolar Current (ACC) upstream of Drake Passage (World Ocean Circulation Experiment section P19 at 88W) are markedly lower than those found in Drake Passage, and a regional source of primordial helium in the path of the ACC that might cause the high-3He feature can be ruled out. We explain the feature by addition of high-3He waters present at the 43S Pacific section. This supports a previous, similar interpretation of a low-salinity anomaly in Drake Passage (Naveira Garabato et al., Deep-Sea Research I 49 (2002) 681), that is strongly related to the high-3He feature. Employing multiparameter water mass analysis (including 3He as a parameter), we find that deep waters as met at the 43S Pacific section, flowing south along the South American continental slope, contribute substantially to the ACC waters in Drake Passage (fractions exceed 50 % locally). Lesser, but laterally more extended contributions are found east of the Malvinas, and still smaller ones are present at 35W and at the Greenwich Meridian. Using velocity measurements from one of the two Drake Passage