Biophysical Feedbacks in the Tropical Pacific

Abstract

This study explores the influence of phytoplankton on the tropical Pacific heat budget. A hybrid coupled model for the tropical Pacific that is based on a primitive equation reduced-gravity multilayer ocean model, a dynamic ocean mixed layer, an atmospheric mixed layer, and a statistical atmosphere is used. The statistical atmosphere relates deviations of the sea surface temperature from its mean to wind stress anomalies and allows for the rectification of the annual cycle and the El Niño-Southern Oscillation (ENSO) phenomenon through the positive Bjerknes feedback. Furthermore, a nine-component ecosystem model is coupled to the physical variables of the ocean. The simulated chlorophyll concentrations can feed back onto the ocean heat budget by their optical properties, which modify solar light absorption in the surface layers. It is shown that both the surface layer concentration as well as the vertical profile of chlorophyll have a significant effect on the simulated mean state, the tropical annual cycle, and ENSO. This study supports a previously suggested hypothesis (Timmermann and Jin) that predicts an influence of phytoplankton concentration of the tropical Pacific climate mean state and its variability. The bioclimate feedback diagnosed here works as follows: Maxima in the subsurface chlorophyll concentrations lead to an enhanced subsurface warming due to the absorption of photosynthetically available shortwave radiation. This warming triggers a deepening of the mixed layer in the eastern equatorial Pacific and eventually a reduction of the surface ocean currents (Murtugudde et al.). The weakened south-equatorial current generates an eastern Pacific surface warming, which is strongly enhanced by the Bjerknes feedback. Because of the deepening of the mixed layer, the strength of the simulated annual cycle is also diminished. This in turn leads to an increase in ENSO variability.

Impact of bio-physical feedbacks on the tropical climate in coupled and uncoupled GCMs

“…The atmosphere-ocean coupled global circulation models (CGCMs) incorporating marine biology have also shown that biological feedback can significantly change the modeled climatology and variability (Marzeion et al 2005;Wetzel et al 2006;Anderson et al 2007;Ballabrera-Poy et al 2007;Lengaigne et al 2007;Jochum et al 2010;Lin et al 2011;Patara et al 2012). For example, Marzeion et al (2005) showed that the presence of chlorophyll leads to a deepening of the mixed layer in the eastern equatorial Pacific due to the biologically enhanced subsurface warming.…”

“…For example, Marzeion et al (2005) showed that the presence of chlorophyll leads to a deepening of the mixed layer in the eastern equatorial Pacific due to the biologically enhanced subsurface warming. Further, they showed that the biological feedback onto the mean state can change significantly when atmosphere-ocean coupling is taken into account.…”

“…For example, some studies reported that the presence of chlorophyll derives an increased mean SST in the eastern equatorial Pacific due to enhanced absorption of shortwave radiation and/or deepening of the mixed layer that leads to reduced upwelling (Murtugudde et al 2002;Marzeion et al 2005;Wetzel et al 2006). On the other hand, surface cooling caused by an indirect dynamical response to the biologically enhanced heating has been also reported (Nakamoto et al 2001;Manizza et al 2005;Loptien et al 2009;Jochum et al 2010).…”

A Conceptual Model Analysis of SST Influence on Marine Biota in the South Java Sea

“…The study has been done by ref. Marzeion (2005) in the study of biophysical feedback in the Tropical Pacific. The equation (1) is called the delayed oscillator model that usually describes ENSO variation.…”

“…The study was done by (Marzeion et al, 2005) where they used a hybrid coupled model for the tropical Pacific i.e. a primitive equation reduced-gravity multilayer ocean model, a dynamic ocean mixed layer, an atmospheric mixed layer, and a statistical atmosphere.…”