Time-space variability of chlorophyll-a and associated physical variables within the region off central-southern Chile

Abstract

Time-space fluctuations of chlorophyll-a (Chl-a) within the region off central-southern Chile (33-42°S), and their association with meteorological-oceanographic conditions, were analyzed using satellite time series data (2002-2012). The mean distribution of moderate values of Chl-a (~0.5 mg·m-3) in the northern section (33-38°S) extended out to ~200 km of the coast whereas they were restricted to a narrower band in the southern section (38-42°S). Mean wind stress and wind stress curl were upwelling favorable for most part of the year in the northern section whereas upwelling-downwelling periods were distinct in the southern section. The dominant frequency of Chl-a variability in the coastal zone and the coastal transition zone was annual, as it was for the rest of the variables, except in a transitional band between these zones and where a semi-permanent jet is located. At the annual frequency, the alongshore distribution of coastal Chl-a presented strong discontinuities, with minimum values around upwelling centers (~37 and 40°S) and higher values (> 2 mg·m-3) in between. Also at the annual frequency, correlation analyses suggest that Ekman transport and Ekman pumping might act synchronously to extend the offshore distribution of the highest Chl-a values during the spring-summer period whereas mesoscale activity appears to contribute to Chl-a increases in the coastal transition zone. Sea surface temperature does not appear to be associated with the annual cycle of Chl-a in the coastal zone and in the coastal transition zone it might be linked to Chl-a variability through the effects of internal waves. © 2013 by the authors.