Energy Transfers between Multidecadal and Turbulent Variability

Abstract One of the proposed mechanisms to explain multidecadal variability observed in sea surface temperature North Atlantic Ocean consists a large-scale low-frequency internal mode spontaneously developing because baroclinic instability time-mean circulation. Even though this has been extensively studied terms buoyancy variance budget, its energetic properties remain poorly known. Here we perform full mechanical energy budget including available potential (APE) and kinetic (KE) decompose into three frequency bands: mean, low (LF) associated with mode, high (HF) mesoscale eddy turbulence. This decomposition allows us diagnose fluxes between different reservoirs understand sources sinks. Because large scale most is contained APE. In our configuration, only source LF APE transfer from mean that attributed instability. return sinks are parameterized diffusion, flux toward HF APE, and, much lesser extent, KE. The presence an additional wind stress component weakens oscillations modifies reservoirs. KE appears have minor influence on relative other involving all experiments. These results highlight utility APE–KE budget.