Abstract
Ocean eddies influence regional and global climate through mixing and
transport of heat and properties. One of the most recognizable and
ubiquitous feature of oceanic eddies are coherent vortices with spatial
scales of tens to hundreds of kilometers, frequently referred as
“mesoscale eddies”. Coherent mesoscale eddies are known to transport
properties across the ocean and to locally affect near-surface wind,
cloud properties, and rainfall patterns. Although coherent eddies are
ubiquitous, their climatology, seasonality, and long-term temporal
evolution remains poorly understood. Here, we examine the kinetic energy
contained by coherent eddies and present the seasonal, interannual and
long-term variability using satellite observations between 1993 to 2019.
A total of $\sim$37 million coherent eddies are
detected in this analysis. Around 50% of the kinetic energy contained
by ocean eddies corresponds to coherent eddies. Additionally, a strong
seasonal cycle is observed, with a 3-6 months lag between the wind
forcing and the response of the coherent eddy field. The seasonality of
the number of coherent eddies and their amplitude reveals that the
number of coherent eddies responds faster to the forcing
($\sim$3 months), than the coherent eddy amplitude
(which lags by $\sim$6 months). This seasonal cycle is
spatially variable, so we also analyze their climatology in key oceanic
regions. Our analysis highlights the relative importance of the coherent
eddy field in the ocean kinetic energy budget, implies a strong response
of the eddy number and eddy amplitude to forcing at different
time-scales, and showcases the seasonality, and multidecadal trends of
coherent eddy properties.