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Global trends in eddy kinetic energy from satellite altimetry

The temporal changes in the oceanic eddy kinetic energy (EKE) including trends and variability are presented and the dynamical mechanisms are investigated. The domain is near-global with a focus on the North Atlantic, North Pacific and Southern Oceans. Altimeter-derived geostrophic surface velocities are used to compute an 18 year time series of EKE on a 1/3� grid. Linear trends are best-fit to the 18-year time series and their statistical significance assessed using bootstrap techniques. Near-global mean EKE trends are non-statistically significant. However, on a regional scale, statistically significant trends are found in all of the major ocean basins. Widespread negative trends occur primarily in the northern and southern subtropical Pacific as well as the central North Atlantic, while positive trends occur primarily in the North Atlantic subtropical gyre, much of the northeast North Atlantic, the southeast Indian Ocean and in several regions in the Southern Ocean. Buoyancy forcing and non-local wind forcing related to the PDO are significant in the North Pacific. In the North Atlantic, changes in wind stress curl as well as changes in local wind speed are implicated, where a di-polar pattern of correlations with the NAO is observed. In the Southern Ocean, changes in local and/or remote winds appear as the dominant mechanism south of 30�S. On a global scale, EKE trends are slightly positive (0.15% of the mean per decade) but non-statistically significant. EKE has decreased in the northern hemisphere and increased in the southern hemisphere despite an increase in hemispheric mean wind speed in both northern and southern hemispheres. Changing wind speeds are influential across all the ocean basins but other mechanisms are significant including shifting wind stress curl fields, buoyancy forcing, indirect (non-local) winds and intrinsic variability. Statistically significant correlations between annual mean EKE and major modes of climate variability are evident in all the ocean basins.
Date January 2015
CreatorsO'Donnell, Christopher John
PublisherUniversity of East Anglia
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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