Origin of the solar-cycle imprint on global sea level change

Abstract

In order to improve insight into the causes of sea-level variability we investigate poorly understood 11-year solar-cyclic oscillations in the temporal rate of global sea-level change. Our approach is based mainly on a thorough reassessment of relevant historical datasets and on an analysis of precise altimetric sea-height observations. We first demonstrate that the temporal rates of change of water volumes stored on land also fluctuate on comparable 11-year timescales, suggesting that the solar-cyclic sea level oscillations we observe result from adjustments taking place in the water-mass balance between the oceanic and terrestrial realms. We then show that these water-mass transfers result primarily from systematic changes that take place in the El Niño Southern Oscillation during the course of the solar cycle. We interpret these evolutionary changes on the basis of a causal sequence that commences within the Quasi-Biennial-Oscillation, a system of regular upper-atmospheric wind reversals that exhibits a clear solar-cyclic dependence and has a well-defined impact on the development of the Madden Julian Oscillation. The latter can influence the strength and rate of evolution of the El Niño Southern Oscillation which, in turn, determines the level of net terrestrial water storage through its effect on rainfall patterns. Recognition of this underlying solar-cyclic modulation advances our understanding of the factors determining historical and future variability in global mean sea level.