Regional Multi-Fluid-Based Geophysical Excitation of Polar Motion

By analyzing geophysical fluids’ geographic distribution, we can isolate the regional provenance for some of the important signals in polar motion. An understanding of such will enable us to determine whether certain climate signals can have an impact on polar motion. Here we have compared regional patterns of three surficial fluids: the atmosphere, ocean and land-based hydrosphere. The oceanic excitation function of polar motion was estimated with the ECCO/JPL data-assimilating model, and the atmospheric excitation function was determined from NCEP/NCAR reanalyses. The excitation function due to land hydrology was estimated from the Gravity Recovery and Climate Experiment (GRACE) data by an indirect approach that determines water thickness. Our attention focuses on the regional distribution of atmospheric and oceanic excitation of the annual and Chandler wobbles during 1993–2010, and on hydrologic excitation of these wobbles during 2002.9–2011.5. It is found that the regions of maximum fractional covariance (those exceeding a value of 3 ⋅ 10⁻³) for the annual band are over south Asia, southeast Asia and south central Indian ocean, for hydrology, atmosphere and ocean respectively; and for the Chandler period, areas over North America, Asia, and southern South America; and scattered across the southern oceans for the atmosphere and oceans respectively.