Raghu Murtugudde

University of Maryland, the Earth System Science Interdisciplinary Center

Nature's Laws and Biological loopholes: Revisiting Bio-Climate Feedbacks and ENSO variability

Room 811 AOSS, Monday, March 12, 2007, 3:30 PM

Abstract

The ability of the photosynthesizing algae in the oceans to convert light to heat has been shown to affect the annual cycle because of seasonal variations in the horizontal and vertical distributions of chlorophyll. As can be expected, any process that affects the mixed layer depths in the eastern equatorial Pacific has a potential to influence the Bjerknes feedback and ENSO. A statistical atmosphere in an anomaly coupling mode is used with satellite–derived diffuse attenuation coefficients to study this aspect. A control simulation with global mean e–folding depth is contrasted with sensitivity simulations with annual mean and seasonally varying spatial distributions to demonstrate the impact of radiative attenuation on model simulations of ENSO. While even an annual mean spatial distribution captures the impact of horizontal distribution of chlorophyll to produce improved ENSO events, including the seasonal variability further adds to the realism of the thermocline depth variability which has implications for lower–frequency ENSO variability. The annual phase–locking is demonstrably improved by providing the seasonal variability of attenuation depths. A simple SST–gradient model for wind–anomalies coupled to the OGCM with an ecosystem is employed to quantify the impacts of interactive bio–feedbacks. Sensitivity studies with varying horizontal and vertical distributions of model chlorophyll shows details of the processes leading to differing ENSO variability. Whether biology is really finding the loopholes for homeostasis is not yet clear but it is evident that some chronic biases in coupled climate models may need biological feedbacks at all time–scales. Can satellite data be used to capture the first order effects?