Physical‐biological synchrony in the global ocean associated with recent variability in the central and western equatorial Pacific

Abstract

[1] Synchrony in the second modes of an empirical orthogonal function (EOF) analysis of global physical and biological properties is described for the 1993-2010 time period. High correlations are found between the El Niño Modoki index and principal component time series of sea surface temperature, sea surface salinity, photosynthetically active radiation, precipitation, surface currents, surface chlorophyll concentration, and equatorial temperature profiles. Spatial patterns indicate that the second mode is also associated with the North Pacific Gyre Oscillation (NPGO). Biological changes during traditional El Niños (first EOF mode) have been explained on the basis of strong and coherent variations in thermocline depth, wind-driven upwelling and light, but changes associated with the second mode are more subtle and complex. Equatorial temperature profiles indicate that the warming is confined to the mixed layer and that changes in thermocline depth are small. The biological changes associated with the second mode may be driven by a combination of weak perturbations to vertical nutrient supply and the strength of subtropical gyres. In the western tropical Pacific, the site of some of the strongest perturbations, the biological changes can be associated with the occurrence and thickness of barrier layers and to island effects downstream of the Kiribati Islands. Globally integrated impacts of the second mode are much weaker than those associated with the traditional ENSO. During the positive phase, chlorophyll is strongly enhanced in the tropics and weakly enhanced at the global scale in sharp contrast to traditional El Niño effects. The analysis improves our understanding of global-scale physical and biological coupling associated with the so-called El Niño Modoki and the NPGO.Citation: Messie, M., and F. P. Chavez (2013), Physical-biological synchrony in the global ocean associated with recent variability in the central and western equatorial Pacific,

Impact of El Niño Variability on Oceanic Phytoplankton

“…Even though, the percent of total affected areas are relatively similar between CP and EP El niño events, the regional differentiation is marked, and may be of opposing sign (e.g., along the coast of Peru and Chile, the Benguela upwelling, the Great Barrier Reef), or affected during an EP event but not during a CP event (e.g., in the tropical eastern and western Pacific). Several process-orientated studies have further highlighted the important role played by horizontal processes (together with vertical processes) in the supply of nutrients in the surface layer, and specifically demonstrated significant impacts in Winter new primary production in the North Pacific transition zone (Ayers and Lozier, 2010), interannual variations of chlorophyll concentration in the Equatorial Pacific (Gierach et al, 2012;Messié and Chavez, 2013;Dave and Lozier, 2015) and the Red Sea , and decadal variations in phytoplankton abundance in the North Atlantic Subpolar Gyre (Martinez et al, 2015). Thus, both the development of statistical methods to study climate impact, and the assessment of the future evolution of regional physical forcing processes may help us to understand phytoplankton responses to climate change and improve confidence in our projection of future ecosystem state Boyd et al, 2014).…”

Seasonal to Interannual Variability of Satellite-Based Precipitation Estimates in the Pacific Ocean Associated with ENSO from 1998 to 2014

“…The EOF is a statistical method used to decompose the variability of a field into sums of modes, each of which is described as a spatial pattern and a time series [41]. To derive the variability of precipitation on an interannual timescale, 13-month running means were used to filter out annual variation and seasonal variability.…”

Using Remote Sensing Products to Identify Marine Association Patterns in Factors Relating to ENSO in the Pacific Ocean

“…With the warmer water expanding eastward from the western PO, the warmer water from the eastern PO also extends westward, which results in downwelling in the middle of the equatorial PO. The downwelling and the abnormal decrease in rainfall in the same region limit the surface supply of nutrients and weaken phytoplankton growth [47]. Then, CHLA in the middle of the equatorial PO decreases abnormally by less than one standard deviation.…”