CO2 as a driving factor of Carbon isotopic signature in the Southern Ocean

Abstract

The carbon cycle in the Southern Ocean changed dramatically over the past few years (Arrigoet al., 1999., as a result of the rising atmospheric CO2. The high rising partial pressure of CO2 in the atmosphere results in an increase in dissolved CO2 concentrations, which almost immediately effects marine plankton (Arrigoet al., 1999; Bousquetet al., 2000.. Reconstructions of CO2 changes in the past help understanding the extent and impact of current changes. However, since pCO2 can’t be measured directly in historic archives, such as oceanic sediment cores, a proxy needs to be established to assess those pCO2 changes of the past. Atmospheric CO2 is made up by the two stable isotopes of carbon, 1.1% of the non-radioactive isotope Carbon 13 and 98.9% of carbon 12 (O'Leary, 1988.. It is possible to measure the isotopic signature of particulate organic carbon (?13CPOC., and it has been used widely in paleo-reconstruction studies as a proxy for pCO2, but it is important to study the relationship between pCO2 and ?13CPOC. If there is a proportional ratio between the isotope and carbon dioxide, ?13CPOCcan be used to measure the pCO2in core sediments. We hypothesise that other factors might bias such proportional ratio in the Southern Ocean. In this study data on POC, ?13CPOC, and phytoplankton abundance (chl-a., community composition, macronutrients such as nitrate, ammonium, phosphate and silicate, micronutrients such as iron, as well as data on temperature and salinity will be analysed. The relationship of all those parameters with changes in ?13CPOC will be tested to determine their potential influence on the phytoplankton ?13CPOC.In addition, available pCO2 data will be used to determine the effect of pCO2 on the ?13CPOC in the upper layer of the Southern Ocean. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.