Application of interleaving models for the description of intrusive layering at the fronts of deep polar water in the Eurasian Basin (Arctic)

Abstract

Interleaving models of pure thermohaline and baroclinic frontal zones are applied to describe intrusions at the fronts found in the upper part of the Deep Polar Water (DPW) when the stratification was absolutely stable. It is assumed that differential mixing is the main mechanism of the intrusion formation. Important parameters of the interleaving such as the growth rate, vertical scale, and slope of the most unstable modes relative to the horizontal plane are calculated. It was found that the interleaving model for a pure ther mohaline front satisfactory describes the important intrusion parameters observed at the frontal zone. In the case of a baroclinic front, satisfactory agreement over all the interleaving parameters is observed between the model calculations and observations provided that the vertical momentum diffusivity significantly exceeds the corresponding coefficient of mass diffusivity. Under specific (reasonable) constraints of the vertical momentum diffusivity, the most unstable mode has a vertical scale approximately two-three times smaller than the vertical scale of the observed intrusions. A thorough discussion of the results is presented.

Generation of large-scale intrusions at baroclinic fronts: an analytical consideration with a reference to the Arctic Ocean

“…Findings by Merryfield (2002) were confirmed by Kuzmina et al (2014). However, the 2-D model of interleaving driven by differential mixing at the baroclinic front failed to simultaneously fit three modeled parameters, namely, the vertical scale, the growth time, and the slope of the fastest growing mode, with observations of intrusions in a frontal zone with a substantial baroclinicity in the upper PDW layer (Kuzmina et al, 2014). In particular, it was found that the vertical scale of the most unstable mode was about 2 to 3 times smaller than the vertical scale of intrusions observed in the baroclinic front.…”

“…Merryfield (2002) was the first to show satisfactory agreement between calculations of unstable modes from a three-dimensional (3-D) interleaving model that accounted for the differential mixing at a non-baroclinic front and observations of intrusive layering at a pure thermohaline front in the PDW. Findings by Merryfield (2002) were confirmed by Kuzmina et al (2014). However, the 2-D model of interleaving driven by differential mixing at the baroclinic front failed to simultaneously fit three modeled parameters, namely, the vertical scale, the growth time, and the slope of the fastest growing mode, with observations of intrusions in a frontal zone with a substantial baroclinicity in the upper PDW layer (Kuzmina et al, 2014).…”

“…We suggest a weak turbulence regime in the layer under consideration: Pr > 1, Pr ·Bu 1. The typical vertical scale of intrusive layering in the fronts of PDW is approximately 30-40 m (Merryfield, 2002;Kuzmina et al, 2014). Let us evaluate the time of formation of intrusions with the vertical scale of ∼ 40 m. Using formula k 0 c = 10·K/H 2 0 (see Sect.…”

Assessment of variability of the thermohaline structure and transport of Atlantic water in the Arctic Ocean based on NABOS CTD data

“…5, bottom panel): the temperature decreases and salinity increases with depth. This structural feature of the mean thermohaline stratification is also common to the UPDW (Rudels et al, 1999;Kuzmina et al, 2011Kuzmina et al, , 2014.…”

“…The absence of the main part of BSBW (with temperature less than -0.5°C) at longitudes to the east of 126°E may be due to various reasons, including mixing with the FSBW caused by thermohaline intrusive layering at stable-stable stratification (Merryfield, 2002;Kuzmina et al, 2013;Kuzmina et al, 2014;Kuzmina, 2016, Zhurbas N., 2018Kuzmina et al, 2018Kuzmina et al, , 2019. Indeed, according to numerous studies, the intrusive layering in the ocean determines the processes of exchange and mixing of various water masses (see, e.g., Stern, 1967;Fedorov, 1976;Joyce, 1980;Zhurbas et al, 1993;Rudels et al, 1999;Kuzmina, 2000;Walsh and Carmack, 2003).…”