A mechanism of formation of multiple zonal jets in the oceans

Abstract

Multiple alternating zonal jets observed in the ocean are studied with an idealized quasigeostrophic model of flow in a zonal channel. The jets are maintained by the eddies generated by the imposed, supercritical background flow. The formation, nonlinear dynamics and equilibration of the jets are explained in terms of linear stability arguments and nonlinear self-interactions of the linear eigenmodes. In the proposed mechanism, energy of the background flow is released to the primary instability mode with long meridional and short zonal length scales. This mode undergoes secondary, transverse instability that sets the meridional scale of the emerging multiple zonal jets. This instability channels energy into several weakly damped zonal eigenmodes that amplify the jets. The emerging jets feed back on the instabilities through the partial meridional localization of the most unstable eigenmodes.

Zonal jets in equilibrating baroclinic instability on the polar beta‐plane: Experiments with altimetry

“…These observations are in accord with the theoretical/ numerical results where primary baroclinic instability is in the form of so-called noodles [Berloff et al, 2009b].…”

“…Observations show that multiple zonal jets are indeed created in these regions and are quite prominent there [Maximenko et al, 2005[Maximenko et al, , 2008Sokolov and Rintoul, 2007;Thompson, 2008]. Berloff et al [2009aBerloff et al [ , 2009b suggested yet another way which leads to creation of zonal jets. The authors studied a quasigeostrophic model of flow in a zonal channel.…”

“…The question then is whether the Rhines mechanism works in the equilibrated flow or the presence of underlying baroclinic instability makes the dynamics significantly different. The measurements of the meridional jet scaling by Berloff et al [2009aBerloff et al [ , 2009b showed that the Rhines scaling did not work universally but only within a certain range of parameters. Note that an earlier numerical study by Panetta [1993] did confirm the Rhines scaling within a similar parameter range.…”

Energy pathways and structures of oceanic eddies from the ECCO2 state estimate and simplified models

“…We term this hypothesis the "vortex-propagation mechanism". Other formation mechanisms include, but are not limited to, stationary Rossby waves (Maximenko et al, 2008), beta plumes (Afanasyev et al, 2011), radiating instabilities of the eastern boundary current (Hristova et al, 2008;Wang et al, 2012), and the nonlinear self-interactions of the linear eigenmodes (Berloff, 2005;Berloff et al, 2009). …”

On quartet interactions in the California Current system

“…Alternative hypotheses based on three-dimensional models have been proposed to explain mechanisms of QZJ generation; see Hristova et al (2008), Berloff et al (2009Berloff et al ( , 2011, Tanaka and Akitomo (2010), Wang et al (2012) and Qiu at al. (2013), among others.…”