One week in the Kiel Fjord - Minute-by-minute temperature and pressure measurements in a southwestern Baltic Sea inlet

Abstract:

To what extent does the water temperature vary in the Kiel Fjord (Germany) during a week and what influence does weather and have on the water column? These were the questions we asked ourselves, when we first planned, constructed and deployed a mooring in the Kiel Fjord. The Kiel Fjord is a 17 km long fjord, located at the German coast in the southwestern Baltic sea. During the one-week-long deployment period, we recorded temperature and pressure every minute at five depths from the surface to the bottom at 6m. Before we could evaluate our data with a program written in Python, we had to calibrate the instruments against a reference. The time series of temperature and pressure showed fluctuations on different time scales from a few minutes to several hours at all depths. At this location, there is no significant tidal signal, so to understand which other factors influence these fluctuations, we compared our data with meteorological data like air temperature, sun radiation, wind speed and direction and the sea level. Preliminary results show that we can explain some fluctuations with these meteorological data. Wind from a southern direction pushes water out of the fjord and leads to a lower sea level. On the contrary, wind from a northern direction pushes more water into the fjord. This way colder or warmer water could have been transported to our mooring. The surface sensor showed a day-night cycle, that is caused by the air temperature and the incoming sun radiation. The deeper instruments did not show fluctuations influenced by the air temperature.