Anthropogenic carbon distribution in the Ross Sea, Antarctica

Abstract

The Ross Sea is an area of dense water formation within the Southern Ocean, hence it potentially plays an important role for anthropogenic CO 2 sequestration : In order to estimate the penetration of anthropogenic carbon in the Ross Sea from total inorganic carbon (TCO 2 ) measurements carried out in 2002 -03 Antarctic Italian Expedition, we applied two independent models. Anthropogenic carbon was present throughout the water column. The highest concentrations were associated with the recently ventilated shelf waters, namely High Salinity Shelf Water (HSSW) and Ice Shelf Water (ISW), due to their recent contact with the atmosphere. The lowest concentrations were observed for Circumpolar Deep Water (CDW), due to its relatively older ventilation age. This water mass intrudes onto the shelf in some parts of the Ross Sea and hence is observed in the sampled section, where it is recognizable for its low O 2 and high TCO 2 concentrations. The overflow of the dense High Salinity Shelf Water out of the continental slope was observed in the area off Cape Adare. Since this recently formed shelf water contributes to the formation of the Antarctic Bottom Water (AABW), this process represents a pathway for anthropogenic carbon export down to the deep ocean.

Distribution of total alkalinity and pH in the Ross Sea (Antarctica) waters during austral summer 2008

“…500 m) at stations D, P, G, H3 and B. The C T standard deviation in the AASW was higher than that (Sweeney 2003;Sandrini et al 2007). …”

“…CDW or MCDW is thought to be important to many processes, such as the formation of AABW (Orsi et al 1999;Gordon, Orsi et al 2009;Orsi & Wiederwohl 2009), the dynamics of the RSp (Reddy et al 2007), and supplying much of the heat involved in the basal melting of the Ross Ice Shelf (Smethie & Jacobs 2005). CDW contains low levels of O 2 and high levels of nutrients (nitrate, NO 3 , phosphate PO 4 and silicate Si(OH) 4 ) and of C T , as it has an older ventilation age compared to the recently formed SW (Rivaro et al 2004;Sandrini et al 2007;.…”

“…The export of new deep and bottom waters produced over the continental margins of the Ross Sea, by the mixing of shelf waters (SWs) and the CDW, contributes significantly to the total ventilation of the deep Southern Ocean (Orsi & Wiederwohl 2009); it may play an important role in the sequestration of anthropogenic CO 2 transferring dissolved CO 2 into the deep ocean (Caldeira & Duffy 2000;Sabine et al 2004;Sandrini et al 2007). The oceanography of the Ross Sea is largely affected by the presence of polynyas (areas where the sea surface is kept free from sea ice even during the winter).…”

Estimating the storage of anthropogenic carbon in the subtropical Indian Ocean: a comparison of five different approaches

“…However, these findings are contradicted by the detection and accumulation of CFCs in Antarctic deep and bottom waters (e.g., Meredith et al, 2001;Orsi et al, 2002) and the C ANT accumulation detected south of Australia (McNeil et al, 2001) and in the South Atlantic Ocean (Murata et al, 2008), or using the TTD technique for the whole Southern Ocean (Waugh et al, 2006). Recent carbon-based studies also detect significant C ANT accumulation in deep and bottom waters of the Southern Ocean (Lo Monaco et al, 2005a, b;Sandrini et al, 2007).…”

Challenges for present and future estimates of anthropogenic carbon in the Indian Ocean

“…However recent studies indicate both a CFC accumulation in Antarctic deep and bottom waters [e.g., Meredith et al, 2001;Orsi et al, 2002] and a C ANT accumulation south of Australia [McNeil et al, 2007], as well as in deep and bottom waters of the Southern Ocean [Lo Monaco et al, 2005a;Sandrini et al, 2007].…”