Differential retention of dissolved barium and silicon in the Atlantic, Indian and Australian sectors of the Southern Ocean

• Main Authors: Dehairs, F., Jacquet, S., Fripiat, F., Cardinal, D., Hoppema, M., Jeandel, C., Monnin, C., Navez, J., Cavagna, A.-J., Speich, S., Boyé, M., Fahrbach, E., Blain, S., Rutgers van der Loeff, M., De Baar, H., Rintoul, S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2011
• Subjects: Antarctic; Southern Ocean; The Antarctic; Drake Passage; Prydz Bay; Pacific; Indian; Weddell; Sarmiento; Antarc*
• Online Access: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=217411

Since the GEOSECS cruises in the 1970s it is well known that dissolved barium and silicon in the water column correlate tightly, but also that slight differences exist between ocean basins, reflecting differences in the biogeochemical cycling of these elements. The cycles of these two elements differ because different players are controlling their water column distributions - biogenic Ba-barite being associated with undefined plankton detritus while the silicon distribution is mainly determined by diatoms. In the Southern Ocean the combination of an intermediate and a deep water re-circulation cell (Toggweiler et al., 2006) favors diatom predominance and an efficient retention of Si (Sarmiento et al., 2007). It is not known to what extent these conditions also control the distribution of Ba in the Southern Ocean. Here we investigate the variability of Si and Ba between the major Southern Ocean basins and along water circulation pathways. For this purpose, we compiled dissolved barium and silicon data from 10 Southern Ocean cruises that took place between 1987 and 2008 in the Atlantic, Indian and Australian sectors, the Weddell Gyre, Prydz Bay and Drake Passage. The comparison of spatially weighted average concentrations between major systems revealed characteristic Si and Ba signatures as well as a clear gradient of Si enrichment vs. Ba from the Weddell Gyre eastward along the path of the Antarctic Circumpolar Current (ACC), reflecting a less efficient retention of Ba in the Southern Ocean domain relative to Si. This synoptic picture of Si/Ba behaviour is still incomplete since Ba data for the ACC in the Pacific sector are very scarce. The few Drake Passage data, however, reveal some enrichment again of Ba and Si (but slightly more so for Si) compared to the Australian sector, stressing the need for Ba data in the pacific ACC. The GEOTRACES programme would represent a nice opportunity to fill this gap.