Intrusions in Double-Diffusively Stable Arctic Waters: Evidence for Differential Mixing?

Abstract

Intrusions like those observed in double-diffusively stable regions of the Arctic Ocean can grow from uniform ambient temperature and salinity gradients if diapycnal mixing of these two components differs. Assuming this to be the driving mechanism, the observed 40–60 m intrusion heights constrain the turbulent diffusivity for heat to be less than about 0.01 cm² s⁻¹ and the salt-to-heat turbulent diffusivity ratio to be greater than about 0.6 if the diffusivities are constant. Observations indicate that the intrusions slope across isopycnals in a sense that is consistent with such a scenario, although the along-intrusion density ratio is greater than that predicted by linear theory for the fastest-growing intrusions. Numerical solutions for growing intrusions resemble observed temperature and salinity profiles.