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On the Modulation of the Periodicity of the Faroe Bank Channel Overflow Instabilities : Volume 12, Issue 3 (21/05/2015)

By Darelius, E.

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Book Id: WPLBN0004020901
Format Type: PDF Article :
File Size: Pages 39
Reproduction Date: 2015

Title: On the Modulation of the Periodicity of the Faroe Bank Channel Overflow Instabilities : Volume 12, Issue 3 (21/05/2015)  
Author: Darelius, E.
Volume: Vol. 12, Issue 3
Language: English
Subject: Science, Ocean, Science
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications


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Fer, I., Guo, C., H. Larse, K. M., Rasmussen, T., & Darelius, E. (2015). On the Modulation of the Periodicity of the Faroe Bank Channel Overflow Instabilities : Volume 12, Issue 3 (21/05/2015). Retrieved from

Description: Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway. The Faroe Bank Channel (FBC) is one of the major pathways where dense, cold water formed in the Nordic Seas flows southward towards the north Atlantic. The plume region downstream of the FBC sill is characterized by high mesoscale variability, quasi-regular oscillations and intense mixing. Here, one year-long time series of velocity and temperature from eight moorings deployed in May 2012 in the plume region is analyzed to describe variability in the strength and period of the oscillations. The eddy kinetic energy (EKE) associated with the oscillations is modulated with a factor of ten during the year and the dominant period of the oscillations changes between three to four and six days, where the shorter period oscillations are more energetic. The dense water is observed on a wider portion of the slope (both deeper and shallower) during periods with energetic, short period oscillations. The observations are complemented by results from a regional, high resolution model that shows a similar variability in EKE and a gradual change in oscillation period between three and four days. The observed variability in oscillation period is directly linked to changes in the volume transport across the sill: the oscillation period decreases with about six days Sv−1 both in the observations and in the model. This is in agreement with results from linear instability analysis which suggests that the period and growth rate decrease for decreased plume thickness. The changes in oscillation period can partly be explained by variability in the upper layer, background flow and advection of the oscillations past the stationary moorings, but the changes in the fraction of the EKE that is derived from the cross isobath motion suggests that the intrinsic period of the instability is modulated. It is further shown that about 50% of the transport variability across the sill is explained by changes in the local barotropic forcing, which is obtained from satellite altimetry.

On the modulation of the periodicity of the Faroe Bank Channel overflow instabilities

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