| Session Details | |
| Section | OS - Ocean Sciences |
| Session Title | Trace Elements and Isotopes in Oceans |
| Main Convener | Dr. Sunil Kumar Singh (Physical Research Laboratory, India) |
| Co-convener(s) | Dr. Deli Wang (Xiamen University, China) |
| Session Description | Trace elements and isotopes (TEIs) play important roles in the ocean as nutrients and as tracers of the contemporary and the past processes. Recently, some of these TEIs are also introduced into the oceans via anthropogenic processes and their distributions also provide information as environmental contamination. Trace elements regulate ocean processes, such as marine ecosystem dynamics and carbon cycling hence influence the entire Earth system by responding to and controlling global change. For example, Iron is a key micronutrient, the scarcity of which limits photosynthesis and nitrogen fixation. Several other trace elements also play vital roles in cell physiology and in biochemical reactions. An international programme, GEOTRACES has been initiated to understand the role of these trace elements in controlling the structure and the productivity of marine ecosystems and to assess the sensitivity of the marine biogeochemical cycles of TEIs to global change and the impact of any resulting changes in elemental cycling on marine ecosystems and the ocean carbon cycle. This programme plans to enhance our knowledge of diverse sources and sinks of TEIs, their internal cycling as well as transport and chemical form in the ocean to understand the biogeochemical cycling of these micronutrients. Many of the stable, radiogenic and radioactive isotopes in oceans serve as tracers to tag and time various oceanic processes and reconstruct paleo- climate/oceanographic records stored in sediments. Sedimentary records reveal prominent correlations between distributions of trace elements in sediments and independent indicators of climate variability; however the ability to use trace elements and their isotopes as reliable paleo-oceanographic/climate proxies is limited by incomplete characterisation of their current biogeochemistry. This, in turn, limits the ability to test ocean models against past conditions, and therefore limits the ability to forecast future changes. For this session, we invite contributions addressing 1)sources and sinks of TEIs in the oceans, 2) water column cycling of TEIs, 3) the development and validation of geochemical proxies dealing with paleo-oceanography and paleoclimate, 4) the reconstruction of past ocean circulation and climate over both longer (Ma) and shorter (ka) time scales and 5) application of radionuclides such as the short-lived daughter isotopes of the natural U-Th decay series as proxies for carbon, silicon, nitrogen, sulfur and phosphorus fluxes. CONVENERS: Sunil Kumar Singh1 & Deli Wang2 1 – Geosciences Division, Physical Research Laboratory, Navrangpura, Ahmedabad 2 – State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China sunil@prl.res.in & deliwang@xmu.edu.cn |