At a period of about 5 days, the ocean shows a remarkable wave-like oscillation in response to planetary-scale atmospheric pressure variations. Past studies of this ocean dynamic response have used computer models and in situ data, but a global characterization of the subject signal has been lacking. A recent article by Verisk Atmospheric and Environmental Research Principal Scientist Rui Ponte and Prof. Michael Schindelegger from the University of Bonn closes this knowledge gap by examining the 5-day oscillation in global fields of ocean bottom pressure, derived with the help of Gravity Recovery and Climate Experiment (GRACE) satellite observations. The GRACE data confirm the spatially homogeneous behavior of the oscillation in the Atlantic, the seesaw of ocean mass between the Atlantic and Pacific basins, and the westward propagation of the wave in the western Pacific. Previously unknown features include relatively large variability in the Southern Ocean and also some shallow coastal regions (e.g., North Sea, East Siberian shelf, and Patagonian shelf). Surface atmospheric pressure is the main forcing for the observed large-scale anomalies in ocean bottom pressure, while wind-driven signals are more spatially confined. Once excited, the oscillation loses its energy within a few days to friction, as the currents impinge on mountains on the seafloor, mainly in the Southern Ocean. Results illustrate the potential of GRACE measurements for examining large-scale oceanic variability at subweekly periods.
Citation & Web Link: Global ocean response to the 5-day Rossby-Haurwitz atmospheric mode seen by GRACE
R.M. Ponte, M. Schindelegger,
Journal of Geophysical Research: Oceans, 127, e2021JC018302, 2022