TY - JOUR
T1 - What makes an elongated lake ‘large’? Scales from wind-driven steady circulation on a rotating Earth
AU - Amadori, Marina
AU - Piccolroaz, Sebastiano
AU - Dijkstra, Henk A.
AU - Toffolon, Marco
PY - 2020/8
Y1 - 2020/8
N2 - 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.
AB - 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.
KW - Analytical solutions
KW - Coriolis acceleration
KW - Ekman theory
KW - Narrow lakes
KW - Numerical modeling
UR - http://www.scopus.com/inward/record.url?scp=85076834582&partnerID=8YFLogxK
U2 - 10.1016/j.jglr.2019.10.013
DO - 10.1016/j.jglr.2019.10.013
M3 - Article
AN - SCOPUS:85076834582
SN - 0380-1330
VL - 46
SP - 703
EP - 717
JO - Journal of Great Lakes Research
JF - Journal of Great Lakes Research
IS - 4
ER -