A series of loggers are currently deployed underwater in in the middle of Rodden Hive measuring temperature, light levels, salinity and water depth. There are also temperature loggers buried in the shingle on the landward side of Chesil Bank. The loggers require periodic maintenance and are downloaded regularly. During the cold snap at the end of February 2018 towards the end of a neap tide period some interesting observations on water temperature fluctuations were made.
The graph shows
- Black line – the general water temperature of the Fleet at the Langton Hive post.
- Blue line – logger buried in about 4cm of mud and rotting vegetation in the intertidal fringe.
- Dotted grey line – pressure which is roughly equivalent to depth at the Langton Hive post.
Our interpretation of the temperature changes for 1st March 2018 recorded by the logger buried in the mud is as follows:
- warming up to 9.5ºC (composting effect) at low tide when the water in the Fleet was below freezing (-1.2ºC) at 05:15 in the morning with a lag of about an hour and a half;
- mud temperature then drops to -0.8ºC, almost the value for the water in the rest of the Fleet about two hours after high tide at Langton Hive when there is more water movement along the Chesil Bank shore;
- as the spring tide cycle developed and the weather became warmer the difference between the mud logger and water logger decreased but the mud remained much warmer by as much as 6ºC at times.
Loggers are maintained by Lin Baldock and Jon Bass with the instrumentation provided by Natural England and Jon Bass. We are grateful to the Chesil Bank and the Fleet Nature Reserve for recently supplying additional loggers and permission to access these loggers on a regular basis with the Warden coordinating the access. Natural England confirmed permission for these studies in the Chesil and the Fleet SSSI.
Post written by Lin Baldock
Research scientist and member of the Fleet Study Group