Climate cycles and dissolved oxygen variability off eastern Luzon, Philippines
Abstract
We assess the effect of El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) on the variability of dissolved oxygen off eastern Luzon, Philippines. In this area, bifurcation of the North Equatorial Current (NEC) into the Kuroshio and Mindanao Currents occurs. Hydrographic parameters and sediment cores obtained during the oceanographic cruises in 2011 and 2012, and data from the World Ocean Atlas 2009 (WOA09) were used in the study. Variability in dissolved oxygen (DO) concentration was observed from surface to the thermocline between the neutral (2011) and La Niña (2012) phase. Based on optimum multiparameter analysis, there was a change in the fraction of water masses in the area. Under neutral conditions, waters off eastern Luzon consist mainly of water (NPSW) from the Kuroshio recirculation gyre that contain higher DO. In contrast, during La Niña conditions the North Equatorial Current becomes stronger bringing in water (NPTW) with lower DO. Thus, variability in DO off eastern Luzon is influenced by the change in the source of the water mass arising from the shift in bifurcation latitude that is linked to ENSO. Longer-term variability in DO was examined using a 2.15m sediment core taken in the shelf off eastern Luzon. The sediment record was used to reconstruct the depositional redox environment in the last 1000 years. The elements V, Ni, Cr, Mn and Fe were normalized to Ti and used as chemical proxies to track DO variability. Results show that DO fluctuations have occurred in the past, and these changes are in agreement with DO variability driven by the Pacific Decadal Oscillation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMOS43B1897E
- Keywords:
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- 4215 OCEANOGRAPHY: GENERAL Climate and interannual variability;
- 4522 OCEANOGRAPHY: PHYSICAL ENSO;
- 4576 OCEANOGRAPHY: PHYSICAL Western boundary currents;
- 4513 OCEANOGRAPHY: PHYSICAL Decadal ocean variability