Wind-induced seasonal angular momentum exchange at Titan's surface and its influence on Titan's length-of-day

Abstract

Titan's substantial obliquity and the global extent of the Hadley circulation give rise to seasonal variation in the mean zonal wind speed and direction in the geostrophic lower troposphere, causing an exchange of a substantial amount of angular momentum between the surface and atmosphere. The wind-induced seasonal length-of-day variation calculated using the global wind profile predicted by a Titan general circulation model (GCM) amounts to 30 s in the absence of a deep subsurface ocean decoupling the outer ice shell from the ice mantle and ∼400 s in the presence of a deep subsurface ocean. This effect should give rise to longitudinal offsets of surface landmarks by ∼10 km and ∼100 km, respectively, in comparison to predicted positions based on a constant rotation rate, and may be detectable by Cassini imaging. Copyright 2005 by the American Geophysical Union.