Spatial and temporal scales of variability in the coastal upwelling and coastal transition zones off central-southern Chile (35-40°S)

摘要

Eastern boundary current systems (EBCs) in the oceans are well known as regions where wind-driven upwelling provides higher nutrient concentrations which stimulates higher levels of biological production along the coastal band (Mackas et al., 2006; Freon et al., 2009). In turn, the enhancement in the ecosystem productivity is strongly linked to location of the main world fisheries (Cury and Roy, 1989; Checkley et al., 2009). Air-sea exchanges of greenhouse gases and heat is also intense in EBCs due to the upwelling of subsurface water masses and, thereby, these regions can have an important impact on the planet's climate (Bakun and Weeks, 2004; Naqvi et al., 2009). In addition, EBCs have been recognized as regions of relatively high levels of eddy kinetic energy and intense mesoscale activity which contribute to enhanced coastal-ocean exchanges of seawater properties and organic and inorganic matter within the so-called Coastal Transition Zone (Brink and Cowles, 1991; Barton and Aristegui, 2004). Productivity in this zone can be stimulated by the upwelling of water and nutrients within eddies (by eddy pumping or other processes) and/or by their advection from the coastal zone through filaments and eddies (Chaigneau et al., 2009; Keister et al., 2009).