HR: 1400h
AN: PP43C-11    [Abstracts]
TI: Biogeochemical Controls on Paleoproductivity Proxies: The Antarctic Sea Ice Environment
AU: * Carson, D S
EM: d.s.carson@sms.ed.ac.uk
AF: The University of Edinburgh, School of Geosciences West Mains Road, Edinburgh, EH9 3JW, United Kingdom
AU: Ganeshram, R S
EM: raja.ganeshram@glg.ed.ac.uk
AF: The University of Edinburgh, School of Geosciences West Mains Road, Edinburgh, EH9 3JW, United Kingdom
AB: The Southern Ocean features prominently in many hypotheses developed to explain the drop in atmospheric CO₂ during Quaternary glaciations. Critical to the testing of these hypotheses is our ability to reconstruct past conditions of Southern Ocean primary productivity, nutrient availability and utilisation; based on isotopic and trace element proxies. One aspect of these proxy records not fully investigated is the extent to which they are influenced by materials formed within sea ice, an environment vastly different from that of the open water column. Most proxies are calibrated for open ocean settings, so material produced within sea ice could potentially confound proxy-based reconstructions of water column conditions. Detailed studies on sea ice material are lacking for most isotopic and trace element proxies used in the Southern Ocean. We report initial results from time-series studies of sea ice and surface water suspended particulate matter in Ryder Bay (67°S, 68°W). Preliminary results show differences in productivity (chl-a, POC/PON) and the isotopic (δ¹³C, δ¹⁵N) and trace element (Ba) composition of nutrients and organic matter formed in sea ice brine and surface waters. Our sampling spans the winter sea ice cover, transition to open water and the spring bloom over two field seasons (2004/5 and 2005/6). Additionally, through similar analysis of materials collected in sediment traps deployed at this site, the extent to which geochemical signals produced in the sea ice environment influence the sedimentary record was investigated. This proxy data was compared to measured environmental parameters including; temperature, the dissolved CO₂ system, nutrient utilisation and dissolved oxygen to allow quantitative analysis of proxy signatures relative to observed surface water conditions. This information was then used to apply sea ice related proxy signals to sediment records from the Antarctic sea ice environment.
UR: http:www.dsc-ed.org.uk
DE: 4207 Arctic and Antarctic oceanography (9310, 9315)
DE: 4845 Nutrients and nutrient cycling (0470, 1050)
DE: 4870 Stable isotopes (0454, 1041)
DE: 4875 Trace elements (0489)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Joint Assembly