Smith, Sharon L.

The Rosenstiel School, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, Tel: 305-361-4819, Fax: 305-361-4765, E-mail: ssmith@rsmas.miami.edu

The Arabian Sea: the carbon cycle's response to strong, predictable physical forcing

At the time the JGOFS expeditions to the Arabian Sea were organized in the early 1990's, first-order issues such as whether or not the Arabian Sea was a sink or a source for atmospheric carbon dioxide were still unclear. Did high rates of primary productivity and large concentrations of sedimentary carbon make it a sink or were these processes overwhelmed by outgassing of carbon dioxide arising from the warming of deeper waters reaching the sea surface via upwelling and mixing? We now have answers to these questions, as well as understanding of many other important processes affecting the carbon cycle in the Arabian Sea. These include seasonality in microbial loop processes, bacteria and total organic carbon; the response of primary productivity to simultaneous atmospheric input of iron and upwelling of nitrogen; the role of physical forcing in the distribution of biological properties and the oxygen minimum zone; potential control of phytoplankton blooms and vertical flux by large-bodied grazers; and strong seasonality in export flux to the seabed. When the Arabian Sea Process Studies ended in 1997, more than 80 research cruises had been carried out, with cruises mounted by Germany, India, Pakistan, UK and USA focused on the northern Arabian Sea while the Netherlands tackled the Somali Current system.