The Density Ratio of Frontal Intrusions in the North Rockall Trough

Abstract

The density stratification of interleaving frontal intrusions is investigated with a statistical method. For this purpose a descriptive model of temperature inversions is formulated in which the thickness of the inversion is proportional to the temperature increase in the inversion. With this model an unbiased estimate can be made of the density deficit or density excess in intrusions with respect to an undisturbed background density stratification. Analysis of temperature inversion data from the North Rockall Trough obtained during the JASIN experiment gave the following results: The thickness of the temperature inversions was proportional to the inverse of the background Brunt-Väisälä frequency N?1. This result disagrees with excisting theoretical models and laboratory measurements but agrees with earlier results indicating that the thickness of intrusions in the North Rockall Trough was proportional to N?1. The salty intrusions had a density deficit, whereas cold, fresh intrusions had a density excess. This result is supported by models in which the dynamics of the intrusions are governed by horizontal density gradients caused by the vertical mass flux at the salt-finger interface of the intrusions. Therefore the cross-frontal interleaving in the Rockall Trough arms to be driven by salt-finger convection.