The temperature conditions in the waters of Stavanger

Summary

In the period November 27th, 2015 to December 2nd, 2016 a rig with eight temperature sensors mounted at different depths throughout the water column, was deployed near the island Lindøy outside Stavanger in Rogaland. On May 2, the measurement rig was recovered for downloading data and to change the batteries. The rig was re-deployed at the same position. On October 24, the rig must have been dragged by a passing vessel as it was found 550-600 m further east when the rig was finally recovered December 2nd. At this position the water depth was only 25-30 m. Measurements from November 2015 to October 2016 suggest that the temperature at 100 m depth in the area outside Stavanger is constantly below 8.7 ° C. At 83-84 m depth, there was a seasonal variation in temperature with the highest temperatures of around 9.0 ° C observed in January 2016. On three different occasions, vertical profiles of temperature and salinity measurements were conducted in the area outside of Stavanger. No horizontal differences in temperature was found at 100 m depth when comparing a station near themeasuring buoywith stations closer to Lervika. These results suggest that that measurements from the rig at Lindøy are representative for the area just outside of Lervika. A single measurement from station VT8 in the Hidlefjord shows that the upper temperature at is roughly 10 °C at 100 m depth in an area which is not far from the measurement rig. This high temperature at depth can be explained by advection of warmer water from the open sea outside Boknafjorden, where temperatures of up to 10 ° C occurs in the period from September to January. The waters just outside Stavanger is much more protected from these seasonal variations, but temperatures up to 10 ° C, can for short periods occur if the right meteorological conditions occur and coastal water is advected into the area outside of Stavanger. The measurements suggest that such events are rare, and that if they occur will typically occur during the period from September to February.