Dynamics of seasonal and interannual variability of the Peru‐Chile Undercurrent

Abstract

Coastal sea level, current, satellite altimeter data and an equatorial Kelvin wave model are used to study the dynamics of seasonal and interannual fluctuations of the Peru‐Chile Undercurrent. Satellite altimetry shows that low frequency, sea level anomalies near 30°S propagate offshore as expected from Rossby wave theory. Those anomalies are related to disturbances of equatorial origin observed near the coast of South America. With a wind‐forced equatorial Kelvin wave model and simple Rossby wave dynamics we show that much of the sea level anomalies, and more than 50% of the observed undercurrent variability near 30°S, at seasonal and interannual periods can be explained by long Rossby waves forced by the equatorial Kelvin waves. The amplitude of the equatorial Kelvin wave can be used to estimate the amplitude of the Rossby wave near the South American coast, and thus, to monitor low frequency changes in the Peru‐Chile Undercurrent.

Following the N<sub>2</sub>O consumption in the oxygen minimum zone of the eastern South Pacific

“…The water samples collected in this study were assumed to be the same age as the calculated water mass age from WOCE. As WOCE transects were located only in one part of our study region, in order to estimate the age of water masses south of 17 • S, we assumed a water mass velocity of 10 cm s −1 (Pizarro et al, 2002). With the ages of the water mass, we obtained the atmospheric N 2 O concentrations from historical data (Holland et al, 2005).…”

Natural and human-induced hypoxia and consequences for coastal areas: synthesis and future development

“…Thus, in all these and other similar systems, physical processes play a key role in controlling the vertical structure of hydrographic parameters and the supply of water masses with low DO (Grantham et al, 2004;Monteiro et al, 2006Monteiro et al, , 2008Bograd et al, 2008). The uniqueness of the eastern boundary upwelling system is their connection with equatorial variability (Pizarro et al, 2002;Rouault et al, 2007), which allows for a remote control of hypoxia events through the pole-ward propagation of equatorial Kelvin waves that may act on the oxycline along the coast (Monteiro et al, 2006a(Monteiro et al, , 2008Guttierez et al, 2008). In the Humboldt system, along-shore wind variability associated with the South Pacific Anticyclone activity also induced Ekman pumping and transport off central Peru and central Chile (Renault et al, 2009) that may favor the occurrence of hypoxia events.…”

“…Delaware, Long Island Sound and Chesapeake Bay) in the first twenty years of the 20th century; the reported negative effects on marine ecosystems included fish kills and mortality of benthic species (cf. Petersen, 1915;Sale and Skinner, 1917;Brongersma-Sanders, 1957;Andrews and Rickard, 1980;Mirza and Gray, 1981;Justic et al, 1987;Rosenberg et al, 1987;Patrick, 1988;Gerlach, 1990;Rosenberg, 1990;Parker and O'Reilly, 1991;D'Andrea et al, 1996;Arau'jo et al, 1999;Bricker et al, 1999;Fonselius and Valderrama, 2003). Since then there have been increasing reports of hypoxia from coastal regions world-wide, e.g.…”

Seasonal variability of the oxygen minimum zone off Peru in a high-resolution regional coupled model

“…Assuming a steady state, lateral oxygen fluxes from subtropical water masses and diapycnal mixing are expected to balance the oxygen consumption . However, the diversity of environmental forcings in the SEP and the variety of timescales at which they operate (Pizarro et al, 2002;Dewitte et al, 2011Dewitte et al, , 2012 have eluded a proper understanding of the processes controlling the OMZ structure and variability. On the one hand, the scarcity of data and rare surveys have only permitted the documentation of the DO temporal variability at a few locations (e.g., Morales et al, 1999;Cornejo et al, 2006;Gutiérrez et al, 2008;Llanillo et al, 2013).…”