A Normal Mode Perspective of Intrinsic Ocean-Climate Variability

Abstract

Observations of the sea surface temperature field over more than a century indicate that there is pronounced variability in the climate system. Understanding the mechanisms of this variability is crucial to determine the role of variations in ocean heat content in past and future climate changes. When a steady background state in an ocean-climate model is slightly perturbed, the long-time response is determined by the spatial patterns of the normal modes. Here, the type and patterns of normal modes for a range of different equilibrium states in a hierarchy of ocean-climate models are reviewed. The rather elegant organization of these normal modes is demonstrated, and prototype physical mechanisms explaining patterns of sea surface temperature variability based on these normal modes are provided.