Detection of the Earth rotation response to a rapid fluctuation of Southern Ocean circulation in November 2009

• Published in: Geophysical Research Letters
• Main Authors: Marcus, S. L., Dickey, J. O., Fukumori, I., de Viron, O.
• Other Authors: Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: [SDU]Sciences of the Universe [physics]; Antarctic; Southern Ocean; The Antarctic; Drake Passage; Pacific; Merra; Antarc*
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-03583374; https://hal-insu.archives-ouvertes.fr/insu-03583374/document; https://hal-insu.archives-ouvertes.fr/insu-03583374/file/Geophysical%20Research%20Letters%20-%202012%20-%20Marcus%20-%20Detection%20of%20the%20Earth%20rotation%20response%20to%20a%20rapid%20fluctuation%20of%20Southern.pdf; https://doi.org/10.1029/2011GL050671

International audience At seasonal and shorter periods the solid Earth and its overlying geophysical fluids form a closed dynamical system, which (except for tidal forcing) conserves its total angular momentum. While atmospheric effects dominate changes in the Earth's rate of rotation and hence length-of-day (LOD) on these time scales, the addition of oceanic angular momentum (OAM) estimates has been shown to improve closure of the LOD budget in a statistical sense. Here we demonstrate, for the first time, the signature of a specific, sub-monthly ocean current fluctuation on the Earth's rotation rate, coinciding with recently-reported anomalies which developed in southeast Pacific surface temperature and bottom pressure fields during late 2009. Our results show that concurrent variations in the Antarctic Circumpolar Current (ACC), which saw a sharp drop and recovery in zonal transport during a two-week period in November, were strong enough to cause a detectable change in LOD following the removal of atmospheric angular momentum (AAM) computed from the Modern Era Retrospective Analysis for Research and Applications (MERRA) database. The strong OAM variations driving the LOD-AAM changes were diagnosed from ocean state estimates of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO) and involved roughly equal contributions from the current and pressure terms, with in situ confirmation for the latter provided by tide-corrected bottom pressure recorder data from the South Drake Passage site of the Antarctic Circumpolar Current Levels by Altimetry and Island Measurements (ACCLAIM) network.