Role of mixed layer depth in surface frontogenesis: The Agulhas Return Current front

Abstract

Air-sea interaction processes that modify the sea surface temperature (SST) front in the Agulhas Return Current region (between 40°E and 55°E) during austral summer and winter are examined using observational data and output from a high-resolution ocean general circulation model. While the air-sea heat flux frontal variations tend to relax the SST front, the frontolysis is amplified (damped) in summer (winter) when frontal variations in the mixed layer depth (MLD) are incorporated. The stronger (weaker) frontolysis associated with the MLD variations is due to the fact that the warming (cooling) by the surface heat flux is amplified south of the front where the MLD is shallower and is reduced north of the front where the MLD is deeper. This study is the first to show that the MLD variations play an important role in affecting the strength of the SST front.

Oceanic fronts and jets around Japan: a review

“…The AC and ARC accompany the SST (SSS) gradient of 1.8 °C (100 km) −1 [0.1 (100 km) −1 ] and 4.1 °C (100 km) −1 [0.4 (100 km) −1 ], respectively, which are as strong as their counterpart in the KE region. The strong SST gradient is due to large transport by these two currents (Tozuka and Cronin 2014); the mean volume transport of the AC and ARC is estimated to be 70 Sv (Bryden et al 2005) and 54 Sv (Lutjeharms and Ansorge 2001), respectively. Compared to the K-SOJ, the volume transport of the AC is about 30 Sv stronger.…”

“…The AC (Gordon 1985) and ARC (Lutjeharms and Ansorge 2001;Nonaka et al 2009;Tozuka and Cronin 2014) are the counterparts of Kuroshio and KE in the South Indian Ocean subtropical gyre (Beal et al 2011) (Fig. 1; Table 2).…”

“…Compared to the K-SOJ, the volume transport of the AC is about 30 Sv stronger. An active ocean-atmosphere interaction occurs over the ARC region Nonaka et al 2009;Tozuka and Cronin 2014), and the associated storm track plays a role in the poleward extension of the summertime subtropical high .…”

Upper ocean response and feedback to spring weather over the Kuroshio in the East China Sea: A coupled atmosphere‐ocean model study

“…Strong winds can result in a shift of the Gulf Stream via the Ekman transport of upper waters [Xue et al, 1995;Li et al, 2002]. The ocean mixed layer depth (MLD) variability can modulate the efficiency of surface heat fluxes in regulating the upper ocean thermal structure, thereby preconditioning subsequent upper ocean variation [Kako and Kubota, 2007;Cronin et al, 2013;Tozuka and Cronin, 2014]. The upper ocean dynamics is essential to the development of atmospheric cyclones [Yu and McPhaden, 2011;Seo and Xie, 2013;Jullien et al, 2014].…”

Forecasting the mixed-layer depth in the Northeast Atlantic: an ensemble approach, with uncertainties based on data from operational ocean forecasting systems

“…(i) The mixed layer integrates a lot of physical ocean processes such as the horizontal and vertical advection and diffusion. Measuring the accuracy of the mixed-layer depth is an essential diagnostic for quantifying limitations in the model schemes or parameterizations (Giordani et al, 2005;Keerthi et al, 2013;Tozuka and Cronin, 2014). (ii) The mixed layer is the ocean layer which is directly in interaction with the atmosphere and the study of the mixed layer can reveal biases or unappropriated formulation of the atmospheric forcing of the ocean model (Béranger et al, 2010;Giordani, 2011).…”