Seasonal Hydrographical Variations in a Sub-arctic Fjord System, Porsangerfjord

During the past 30 years, significant biological and physical changes have been observed in a sub-arctic fjord system (Porsangerfjord) in northern Norway. In order to assess this change and to get a clear understanding of the seasonal variation of the physical parameters in this fjord system, a candidate year, 2006, was chosen. This was done due to the extensive temporal and spatial data coverage of this year. Temperature and salinity profiles were sampled at ten different CTD stations in this fjord system by a routine environmental survey program (Havmiljødata). In addition, temperature and the river's discharge were investigated. In May, development of a surface layer was strongly correlated by the fresh water discharge from three major river systems in this fjord; an increase of irradiance. In July, southerly winds induced the advection of denser fjord water in an offshore direction and this water was replaced by lighter Norwegian coastal water. However, northerly winds led to the intrusion of denser Atlantic water in November. This study shows the importance of the concerted dynamics of estuarine circulation (density driven circulation) and wind-driven circulation in fjord systems. The spatial gradient of the observed physical parameters between the inner and outer fjord basin could potentially lead to faunistic gradients, change in community structure and could be linked to the ongoing observed biological changes.