What makes an elongated lake ‘large’? Scales from wind-driven steady circulation on a rotating Earth

Marina Amadori*, Sebastiano Piccolroaz, Henk A. Dijkstra, Marco Toffolon

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

When investigating wind-induced steady circulation, the effect of the acceleration due to Earth's rotation is often neglected in narrow lakes, but the argument behind this assumption is blurred. Commonly, when the horizontal dimension is smaller than the Rossby radius, the Coriolis force is considered unimportant, but this is correct only for inertial currents and barotropic and baroclinic waves. In this work, we revisit the classical Ekman transport solution for wind stress acting along the main axis of an elongated lake in steady-state conditions. We demonstrate that a secondary circulation develops and that the resulting crosswise volume transport, constrained in the closed domain, produces downwelling and upwelling that cannot be predicted by the standard Ekman formulas. We claim that the Rossby radius does not play any role in this process, which on the contrary is governed by the ratio between the actual depth and the thickness of the Ekman layer. The theoretical analysis is supported by numerical experiments to show the dependence on latitude, width, depth and turbulence closure.

Original languageEnglish
Pages (from-to)703-717
Number of pages15
JournalJournal of Great Lakes Research
Volume46
Issue number4
DOIs
Publication statusPublished - Aug 2020

Keywords

  • Analytical solutions
  • Coriolis acceleration
  • Ekman theory
  • Narrow lakes
  • Numerical modeling

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