| Summary: | This study assessed a suite of geochemical proxies in the coastal Antarctic sea ice environment over two growing seasons (2004-2006). Time series measurements or productivity and export production were carried out over two contrasting growing seasons in Ryder Bay, a coastal embayment on the Western Antarctic Peninsular with a heavy sea ice influence. Concurrent measurements of elemental (C, N and Ba) and isotopic (<sup>13</sup>C and <sup>15</sup>N) tracers were carried out on nutrients, suspended particulate matter and sinking particulate matter. The results of these measurements identified the following mechanisms that affect the use of these proxies as palaeoceanographic tracers. Variability of δ<sup>13</sup>C<sub>PCC</sub> at this site is not caused by changes in [CO<sub>2(aq)</sub>] or δ<sup>13</sup>C-CO<sub>2</sub>, but appears to be affected by changes in diatom assemblages with different surface area to volume ratios and biochemical pathways for C fixation. Although the δ<sup>13</sup>C<sub>POC</sub> signal in surface waters is transferred to depth, these findings preclude the use of δ<sup>13</sup>C as a tracer of paleo-<i>p</i>CO<sub>2</sub> concentration. δ<sup>15</sup>N, the proxy for nitrate utilisation in the Southern Ocean shows a predicted response to nutrient utilisation and the physical properties of the water column in each season, with each season displaying a different evolution of δ<sup>15</sup>N over the course of spring and summer. However, this proxy for utilisation of nitrate does not reflect the absolute changes in C flux. It is therefore necessary to consider this scenario when making connections between nitrate utilisation and changes in atmospheric CO<sub>2</sub> in sediment cores. This study also better constrained the biogeochemical cycling of Ba in the coastal Antarctic sea ice environment.
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