The Seasonal and Interannual Ocean Mixed Layer Heat Budget in the Galápagos Upwelling Region Using a High‐Resolution Coupled Model

Abstract The eastern equatorial Pacific Ocean (EEP) plays a critical role in the global climate system through widespread CO 2 outgassing and cool sea surface temperatures (SST) that occur due to persistent Ekman suction (upwelling). The Galápagos Islands—situated on the equator in the EEP—disrupt the Equatorial Undercurrent (EUC), causing strong upwelling on its western boundary and an SST minimum referred to as the Galápagos Cold Pool (GCP). This study analyzes the ocean mixed layer heat budget of the GCP relative to an open‐ocean region in the EEP using a 140‐year present day simulation of a high‐resolution (0.1° ocean) version of the Community Earth System Model (CESM), version 1.2.2. We diagnose the contributions of each heat budget term with emphasis on vertical advection and eddy diffusion—hypothesized to be important near the Galápagos. Our results distinguish the seasonal heat balance in the GCP from the open ocean in the EEP. The net surface heat flux in the cold tongue is balanced primarily by vertical mixing, vertical advection dominates in the GCP. A variety of processes that vary throughout El Niño‐Southern Oscillation (ENSO) phases are also important within the GCP, including changes to vertical and horizontal advection and vertical mixing, leading to associated SST anomalies. A thorough understanding of these processes and their contribution to the surface heat balance is essential in understanding the formation of the GCP, its interaction with the atmosphere, and its potential response to climate change with implications for this climatically and ecologically vital region.