Variability of the Mindanao Dome upwelling system during ENSO event from 2010 to 2015

Abstract

The Mindanao Dome (MD) upwelling system has important implications for the local and even the global air-sea interaction, but its changing process in hydroecological conditions and response mechanism influenced by ENSO cycle are still unclear. The evolution of MD upwelling process and the changes in hydro-climatic environments in MD region in three typical El Niño, La Niña, and normal years during ENSO event from 2010 to 2015 are analyzed. Results reveal that migration of surface water is the main factor controlling the changes in the intensity of the MD upwelling during this ENSO cycle but not the variations in wind stress curl. Massive westward accumulation (eastward movement) of surface warm water and strengthened (weakened) upwelling Rossby waves together induce the enhancement (weakness) of the MD upwelling during mature phase of 2015/2016 El Niño (2010/2011 La Niña) year. In addition, NECC and MD upwelling together control the biological activities in surface waters in MD region during this ENSO cycle. The meandering NECC and MD upwelling both strengthen (weaken) when 2015/2016 El Niño (2010/2011 La Niña) occur, which transport more (less) nutrients to surface sea from horizontal and vertical levels, respectively, leading to an increase (decrease) in surface Chl-a. Two synopsis mechanisms are proposed to illustrate the response mechanism of the MD upwelling evolution and eco-hydro-climatic variations in the MD region to 2015/2016 El Niño (2010/2011 La Niña) event, respectively. This paper highlights the prospect for the role played by ENSO cycle in local ecological effects and hydro-climatic evolution, which further has profound implications for understanding the influence of the global climate change on the ocean carbon cycle.