Thierry Penduff

Intrinsic processes such as mesoscale turbulence have recently been proved as important as atmospheric variability in causing variations in ocean bottom pressure ( p b ). Intrinsic processes are also known to generate random variability on scales larger than the mesoscale through inverse energy cascades or large-scale baroclinic instability. Here, model analyses reveal a truly global-scale, intrinsic p b mode of variability at monthly time scales that relies on a different mechanism. The intrinsic mode has largest amplitudes around Drake Passage and opposite polarity between the Southern Ocean and Atlantic/Arctic oceans. Its signature is consistent with localized eddy-driven p b anomalies of opposite sign near Drake Passage that then adjust freely in the rest of the ocean via barotropic wave processes. This intrinsic mode seems consistent with observed p b variability.