The influence of large-scale atmospheric circulation on the variability of salinity at Helgoland Roads station

M Ionita,G Lohmann,N Rimbu,K Wiltshire

doi:10.1111/j.1600-0870.2008.00352.x

Abstract

The variability of April salinity at Helgoland Roads station (54.12◦N, 7.9◦E, Germany) is analysed in relationship with Elbe river discharge and the observed variability in large-scale atmospheric circulation for the period 1962–2000. It is shown that the main driver of salinity anomalies is the river discharge anomalies from the previous month. These discharge anomalies are strongly related with precipitation anomalies from the Elbe catchment area. Changes in the salinity, discharge and precipitation anomalies are accompanied by a wave train atmospheric circulation pattern that connects the tropical Atlantic Ocean with northern part of Europe, as well as with changes in large-scale water vapour transport over the whole German Bight. Positive sea-surface temperature anomalies, centred in the Caribbean region and the North Sea, are associated with positive salinity anomalies and negative anomalies of discharge and precipitation.

Highlights

The eastern German Bight is a zone of intensive mixing of two water bodies, theNorth Sea water and the coastal water which is of lower salinity and density
Greenland correspond with the so-called “Russell cycle” (Russell et al, 1971; Russell, 1973). According to his hypothesis the breakdown of this high pressure system at the end of 1960s iew led to changes in the wind stress and induced the Great Salinity Anomaly (GSA) (Dickson et al, 1988)
The dominant pattern of variability in the salinity, Elbe discharge and precipitation time series is calculated through Empirical Orthogonal Function (EOF) analysis

Summary

Introduction

The eastern German Bight is a zone of intensive mixing of two water bodies, theNorth Sea water and the coastal water which is of lower salinity and density. During the last decade interest in the variability of hydrological (i.e. river run-off) and ecological parameters (salinity, nutrients) in connection with large-scale atmospheric circulation has markedly increased (Aebischer et al., 1990, Dippner, 1997a, b; Becker and Pauly, 1996). Cushing and Dickson (1976) speculated that atmospheric circulation is responsible for a series of events that were observed in the North Sea in the last few decades. He showed that the beginning and end of an anomalously strong and long-lasting high pressure system over. The cool, low-stratified water columns of the GSA delayed the primary production (phytoplankton) and led to changes in the food web

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Conclusion