ENSO modulations by Freshwater Forcing and Ocean Biology-induced Heating in the Tropical Pacific Rong-Hua Zhang1, Chuan Gao1, Xianbiao Kang1 and Hai Zhi2 1 Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, PR China. E-mail: email@example.com 2 College of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing, PR China Recent studies have identified clear climate feedbacks associated with interannual variations in freshwater forcing (FWF) and ocean biology-induced heating (OBH) in the tropical Pacific. The interrelationships among the related anomaly fields are analyzed using hybrid coupled model (HCM) simulations to illustrate their combined roles in modulating the ENSO. The HCM-based supporting experiments are performed to isolate the related feedbacks, with interannually varying FWF and OBH being represented individually or collectively, which allows their effects to be examined in a clear way. It is demonstrated that the interannual freshwater forcing enhances ENSO variability and slightly prolongs the simulated ENSO period, while the interannual OBH reduces ENSO variability and slightly shortens the ENSO period, with their feedback effects tending to counteract each other.