The ocean is the heartbeat of the planet, moving heat and energy around, creating, and responding to, unique climate regimes in different parts of the world. To understand the climate is to understand the ocean, and vice versa. CIRES researchers probe critical questions related to the role of the oceans in pacing the climate, including the interplay between phenomena such as EL Nino-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). The dynamics of both the tropical and high latitude oceans, coupled with the atmosphere, are particular strengths within CIRES. Scientists also focus on how the ocean-climate system has changed in the past, and work to project how it may change in the future.