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Effects of balanced motions and unbalanced internal waves on steric height in the mid-latitude ocean
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  • Xiujie Zhang,
  • Xiaolong Yu,
  • Aurelien L.S. Ponte,
  • Wenping Gong
Xiujie Zhang
Sun Yat-sen University
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Xiaolong Yu
Sun Yat-sen University

Corresponding Author:[email protected]

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Aurelien L.S. Ponte
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Wenping Gong
School of Marine Sciences, Sun Yat-sen University
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The baroclinic component of the sea surface height, referred to as steric height, is governed by geostrophically balanced motions and unbalanced internal waves, and thus is an essential indicator of ocean interior dynamics. Using yearlong measurements from a mooring array, we assess the distribution of upper-ocean steric height across frequencies and spatial scales of O(1-20 km) in the northeast Atlantic. Temporal decomposition indicates that the two largest contributors to steric height variance are large-scale atmospheric forcing (32.8%) and mesoscale eddies (34.1%), followed by submesoscale motions (15.2%), semidiurnal internal tides (8%), super-tidal variability (6.1%) and near-inertial motions (3.8%). Structure function diagnostics further reveal the seasonality and scale dependence of steric height variance. In winter, steric height is dominated by balanced motions across all resolved scales, whereas in summer, unbalanced internal waves become the leading-order contributor to steric height at scales of a few kilometers.
26 Sep 2023Submitted to ESS Open Archive
30 Sep 2023Published in ESS Open Archive