GLOBAL TRENDS IN EDDY KINETIC ENERGY FROM SATELLITE ALTIMETRY

O’Donnell, Christopher John (2015) GLOBAL TRENDS IN EDDY KINETIC ENERGY FROM SATELLITE ALTIMETRY. Doctoral thesis, University of East Anglia.

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Abstract

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.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Mia Reeves
Date Deposited: 29 Jan 2016 11:22
Last Modified: 29 Jan 2016 11:22
URI: https://ueaeprints.uea.ac.uk/id/eprint/56871
DOI:

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