The role of the oceans in shaping the tropospheric response to the 11 year solar cycle

Abstract

Observational data indicate a weakening and poleward shift of the subtropical tropospheric jets in the maximum phase of the 11 year solar cycle, commonly explained in terms of a direct "top-down" propagation of solar signals from the stratosphere to the troposphere. We here demonstrate possible linkages to oceanic variability, instead. The observed response of the jets is qualitatively and quantitatively reproduced in an ensemble of simulations with a global model forced only at the lower boundary by the observed sea surface temperatures and sea ice concentrations, while keeping solar cycle forcing constant. The twentieth century reanalysis, in which only surface observations are assimilated, is characterized by a similar shift of the jets. These findings suggest that changes at the ocean surface could contribute considerably to the poleward shift of the subtropical tropospheric jets, although a top-down influence on the oceans and hence indirectly on the jets cannot be excluded. ©2013. American Geophysical Union. All Rights Reserved.