Carbonate system properties in the Gerlache Strait, Northern Antarctic Peninsula (February 2015): II. Anthropogenic CO2 and seawater acidification

During the NAUTILUS I cruise in February 2015, the carbonate and associated physical properties were measured throughout the water column in the Gerlache Strait-off the southern coast of the Northern Antarctic Peninsula (NAP). Part I of this study (Kerr et al., 2017, this issue) focused on the net sea-air carbon dioxide (CO2) flux, whereas the same dataset was used here to estimate the extent of anthropogenic carbon (Cant) storage in the Gerlache Strait deep basin. In addition, the impact of Cant increases on pH and calcium carbonate saturation states for calcite and aragonite (ΩCa and ΩAr, respectively) were evaluated. The results indicate that, up to the present, 21.2 ± 16.7 μmol kg−1 of Cant have been injected to the deep and bottom layers of the Gerlache Strait. Two mechanisms may have contributed to that fact: (i) the pathway of the Cant follows that of the high salinity shelf waters inflow coming from both the Bransfield Strait and the Northwestern Weddell Sea shelf, and (ii) the Gerlache Strait is absorbing a significant amount of Cant from the atmosphere. Therefore, pH, ΩAr and ΩCa are decreasing in the deep waters of the Gerlache Strait. Since ΩAr is already very close to 1 at depth, any small additional input of Cant will trigger the dissolution of aragonite.