Hydrophysical characteristics of the northern Norwegian coast and fjords

Abstract

It is evident that, both due to the large water volumes they hold and that they stretches from coast to inland, it is to be expected that the northern Norwegian fjords plays an important role in a climatic scientific context. Also generally northern regions are considered as a choke point in the regional as well as the global climate. In my opinion it is therefore surprising to find thorough physical oceanographical examinations of these areas are scarce or missing. Since large data sets are compiled in the present thesis, it is my hope that it will contribute and trigger further investigations and interpretations. Due to the large spread of data in time and space, it is clear that my physical oceanographical interpretations are far from comprehensive.

The periodic collection of hydrophysical data along the northern Norwegian coast (from Malangen to Porsangerfjord) started in the beginning of the 20th century and some of the oldest stations are still in operation by the “Havmiljødata” sampling programme orga nized by BFE/UIT. One of the the main aims of the current PhD project was to organize and systematize the datasets and analyze for long term trends and also aspects of shorter period variations. The complete database from 1920–2012 has been digitalized and pre sented to the general public and scholars on the website http://purl.org/hmd.

The results of the research demonstrates some significant differences in the hydrophysical characteristics between the investigated fjords. There are also hydrographic variations between Inner fjords and Outer fjords. The hydrographic features of the fjords of northern Norway notably differ from the Arctic and Southern ones in many ways. The peak surface temperatures in the northern Norwegian fjords were recorded in July–August whereas the highest bottom temperatures were measured in November–December. In terms of temperature and salinity variations, Balsfjord demonstrates the highest range of temperature and salinity among the fjords, followed by Altafjord. Malangen shows a narrower distribution in both parameters whilst Porsangefjord is considerably colder (has the lowest temperatures) and also operates at the narrowest salinity range. According to the computations Altafjord has the least water exchange, followed by Malan gen and Balsfjord, whereas Porsangerfjord has the most heat and water advected into the fjord. The outer and coastal stations are affected by Atlantic Water (AW), however the in ner stations in Porsangerfjord and Altafjord and other locations are not. The overall heat content and the temperature anomalies for 5m at stations Outer Malangen (open fjord), Inner Balsfjord (closed fjord), Refsbotn (coastal station) and Outer Porsangefjord (north ern open fjord) have been calculated. They demonstrate no significant heating or cooling trends during the period of 1920–2012. Main warm periods during the winter season were 1929–1930, 1990–1992 and 2000 in all the stations ( Malangen, Balsfjorden, Refsbotn Skipsholmen and Outer Porsangerfjor den ). Also Outer Malangen and Inner Balsfjorden were warmer in 1938. Malangen and Balsfjorden experienced another warm period during 2005 followed by a constant cooling trend until 2012 whereas in Altafjorden and Porsangerfjorden the warm period was in 2007 before it started cooling. The correlation between interannual variability of temperature in Inner Balsfjorden and NAO index has been discovered. The changes of the NAO index parameters cause the subsequent temperature shift in the fjord that may occur after a considerable time.