Asymmetry variabilities of mesoscale eddy activity alongside the Kuroshio Extension

Friday, December 14, 2018 - 08:00
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Mesoscale eddies in the world ocean play an important role in many oceanic processes, such as nutrients mixing and energy exchange. Rich eddy activities are prominent in western boundary current systems, such as the Kuroshio Extension. Here, we study the statistical characteristics and variabilities of mesoscale eddy activity alongside the Kuroshio Extension during 1993-2016 using the global mesoscale eddy trajectory atlas products distributed by Archiving Validation and Interpretation of Satellite Data in Oceanography (AVISO). To gain insights on how mesoscale eddies with lifetime longer than 4-weeks will affect the distribution of the eddy kinetic energy, the eddies are classified by their polarity – cyclonic or anticyclonic. Different eddy characteristics and variations are found in north vs. south of the Kuroshio Extension. For example, mesoscale eddy kinetic energy south of Kuroshio Extension contributes 11% more to the total eddy kinetic energy than that north of Kuroshio Extension. Furthermore, there is a polarity preference of the cyclonic/anticyclonic eddy activity at north or south of the Kuroshio Extension, such as the kinetic energy for cyclonic eddies is twice as much as that for anticyclonic eddies south of Kuroshio Extension (776.2 cm2/s2 vs. 321.8 cm2/s2), but a comparable strength in eddy kinetic energy north of Kuroshio Extension for cyclonic and anticyclonic eddies (525.9 cm2/s2 vs. 639.3 cm2/s2, respectively). And the eddy characteristics in the southern region of Kuroshio Extension show much more distinct decadal variabilities. Such contrast is also found in other eddy characteristics, such as occurrence number, amplitude and lifetime. This spatial disparity of the eddy activities alongside the Kuroshio Extension appears to be related to the large-scale North Pacific climate mode, specifically Pacific Decadal Oscillation.

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