Diatom Transfer Functions for Sea Surface Temperature and Primary Productivity in Upwelling Areas: the Cupex Project

Marine productivity plays an important role in natural carbon dioxide (CO2) variations through the "biological pump". This biological pump (mainly driven by diatom activity) is focused in specific regions, like the upwelling areas (less that 1% of the world's oceans total area), which support high export production. In these areas, atmospheric CO2 can be transported into the ocean. Therefore, to understand natural variations in atmospheric CO2 and other oceanic properties, we must understand the long-term history of these regional upwelling systems. Because of the interrelation between wind-driven coastal upwelling and diatom domination in phytoplankton blooms, diatom time-series from such areas can provide important information on climate change related variability in upwelling and nutrient supply. Therefore, upwelling areas represent key regions for oceanic properties reconstructions, which can be approached by the use of diatom Transfer Functions (TFs). Since the early 80's, TFs development became a major issue due to the extreme importance of understanding past ocean properties. However, the major focus has been on open ocean and calcareous microorganisms. Besides, the existing data for sea surface properties was a problem (data was cease and irregular), as such, some properties were more investigated than others. Today, with satellite data and better instrumental technologies, more and uniformly distributed information is available. Furthermore, the modern computer technology and power enable us to apply stronger and faster statistical tools and models. The development of TFs for coastal upwelling areas is one of the main goals of the CUPEX project: Coastal Upwelling Natural Variability: the last two Climate Extremes (21,000 ± 2,000 Cal-yr BP and 8,000 ± 1,500 Cal- yr BP), so that quantitative reconstructions of the environmental conditions of the last two past climate extremes: the Last Glacial Maximum and the Holocene Optimum are possible. Our environmental reconstructions comprise past nutrients content, sea surface temperature (SST) and primary productivity (PP), and the first results refer to the American coastal upwelling systems (the California and the Humboldt systems) and the Arabian Sea monsoon related upwelling system.