Role of the deep ocean in forming of the global warming slowdown

Abstract

A slowdown of the increase of the surface air temperature (SAT) at the beginning of the 21 century has provoked the discussion for the phenomenon nature and responsible physical mechanisms. One of the most accepted hypothesis connects the slowdown of SAT rise to anomalously intensive uptake of heat energy by the deep ocean layers. We suppose that verification of the theory can be achieved via the study of the interrelationship of the surface and the deep ocean layers temperatures. Establishing the time shifts and especially the sign of the cross-correlation function of the two temperatures can shed light on the solidity of the theory background. For the aims of the study, we have used a stochastically forced two-box climate model. Analytical estimation of correlation functions and spectral characteristics of the model demonstrates that deep ocean heat uptake cannot serve as a driver of the SAT slowdown (at least in the framework of the model). The cross-correlation function of upper layer and deep ocean temperatures stays nonnegative for any time lag. It means that heat redistribution between layers cannot lead to hiatus forming. Moreover, a comparison of the two-box model and Hasselmann model spectral characteristics evidences that the deep ocean serves as a pacemaker of climate variability in the broad range of frequencies.