Paul A., Afroosa M., Rohith B., Schindelegger M., Durand Fabien, Bourdalle-Badie R., Shenoi S. S. C. (2024). The anomalous 2012-13 boreal winter oceanic excitation of earth's polar motion. Pure and Applied Geophysics, [Early access], p. [17 p.]. ISSN 0033-4553.
Titre du document
The anomalous 2012-13 boreal winter oceanic excitation of earth's polar motion
Paul A., Afroosa M., Rohith B., Schindelegger M., Durand Fabien, Bourdalle-Badie R., Shenoi S. S. C.
Source
Pure and Applied Geophysics, 2024,
[Early access], p. [17 p.] ISSN 0033-4553
Recent work has shown that the Madden-Julian Oscillation (MJO) winds around the Maritime Continent can drive a see-saw in oceanic mass between the Indian and Pacific oceans on intraseasonal time scales. During the boreal winter of 2012-13, this see-saw accounted for about two thirds of an unusually large (similar to 30 mas, milliarcseconds) fluctuation in the oceanic excitation of Earth's polar motion about the 90 degrees E meridian. Interestingly, the magnitude of the oceanic influence was nearly at par, but out-of-phase with that of the atmosphere and a factor of similar to 10 larger than effects associated with the hydrological cycle. Here we show that oceanic mass changes and transport anomalies during the 2012-13 boreal winter were indeed most pronounced in the Indo-Pacific basin, and that they possessed a favorable geometry to excite polar motion variations about the 90 degrees E meridian. Phase alignment of the excitation signals from different regions, as well as between mass and motion terms, was a key characteristic of the 2012-13 event, but was far less distinct in other strong see-saw years. Basin-wise, the Indian Ocean acted as a dominant contributor to the 2012-13 polar motion excitation at MJO periods, followed by the Pacific basin. Overall, ocean dynamics in the 10 degrees-65 degrees S latitudinal belt over the Indo-Pacific basin accounted for similar to 93% of the global oceanic excitation function during the 2012-13 winter. The processes figuring most prominently in modulating intraseasonal polar motion were mass rearrangements in the southern Indian Ocean and the south-east Pacific Ocean, the east Australian current, and the Antarctic circumpolar current around the Antarctic landmass. Wind-driven dynamics in the Southern Ocean thus appear to be the main cause for the 2012-13 oceanic excitation signal not attributable to the see-saw.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020]
;
Limnologie physique / Océanographie physique [032]
