Equator-to-pole energy transport by the ocean and atmosphere is a fundamental constraint on the Earth's climate. In his 1964 seminal paper, Jacob Bjerknes suggested that if the top-of-the-atmosphere fluxes and the ocean heat storage do not vary substantially, which is a reasonable assumption on long time scales, the total energy transport by the climate system would not vary much either. This implies that any large anomalies of oceanic and atmospheric energy transports should be equal and opposite. Despite its fundamental importance in understanding the climate system, this hypothesis, the so-called Bjerknes compensation, has been tested by only a limited number of studies.

We propose to investigate the degree of compensation in poleward energy transports by the atmosphere and ocean and its dependence on the time scale, latitude and background climate based on a large suite of the Community Earth System Model version 1 (CESM1) simulations to test the Bjerknes compensation hypothesis. Our particular emphases are to understand: (1) robustness of the degree of the compensation across the various simulations with differing parameterizations and initial conditions, (2) the competing role of atmosphere-ocean couplings through the momentum flux and buoyancy flux in enabling or deterring the compensation, and (3) the role of compensation in the leading modes of variability in the atmosphere and ocean.

Being a fundamental integral measure and driver of our climate system, and its variability and change, the partition and compensation of the poleward energy transports by the ocean and atmosphere are ideal but rarely used metrics for model-to-model and model-to-observation comparisons. Through the proposed effort, we would strive to develop objective, energy compensation-based metrics for the leading modes of climate variability, climate change, and their predictability and uncertainty.