Intrusive layering of the Antarctic slope front

Abstract

Cascading of cold Antarctic shelf water (ASW) initiates compensatory isopycnic upwelling of the warm Circumpolar Deep Water (CDW). The baroclinic/thermoclinic Antarctic slope front (ASF) is formed, and a mesoscale intrusive structure develops on the shelf edge and slope. Mesoscale processes when the ASF peaks are periodically accompanied by local baroclinic instability, which forms a smaller-scale intrusive structure. Therefore, the ASF is naturally subdivided into two layers according to the intrusion scales (vertical δН and horizontal L) and the horizontal parameters of the front (thermoclinity (T L)ρ and baroclinity γρ). Analysis of ASF intrusive layering due to the baroclinic factor supports the following conclusion: the higher the (T L)ρ of the ASF, the greater the intrusion intensity |δθ| (temperature anomaly amplitude), while an increase in γρ of the ASF leads to a decrease in intrusion scales δН and L. Frontal intrusions can be distinguished by a development degree. Regardless of the degree of development, all warm intrusions are characterized by vertical density stratification, while cold intrusions are characterized by density quasihomogeneity. According to field data, the ASF instability process is subdivided into four stages. When theASF is baroclinically unstable, the local baroclinic deformation radius Rd L of the front is close in magnitude to the horizontal scale L of the intrusions that form, and their characteristic vertical scale δH is close to the typical vertical scale of front instability.