Fishy Business

Tide gauge

The Proudman Oceanographic Laboratory (POL) maintain a network of sensors around the UK and the South Atlantic to monitor tidal elevation. Rothera's well house (built as the intake for our reverse osmosis plant which provides our drinking water) is an ideal site for a tide sensor as it is directly connected to the sea by an underground pipe, so the level is the well is always the same as the current sea level.

As part of my job, I carry out calibration water level dips for POL so that they can check that their automated equipment is doing what it should be. In summer this involves walking to the well house, jumping up onto the roof (it is about waist-high), lifting the lid and climbing down the ladder inside. After six months of winter it is a slightly different game, as first I have to spend half an hour digging through the snow to find the lid, clearing enough snow to be able to lift the lid and give myself somewhere to stand so that I can open it, and then try to climb into it safely.

Once inside it is not too unpleasant though, as there is a heater which stops the damp affecting the electrics used to run the monitoring equipment, and it is out of the wind and snow.

I use a tape measure on a reel which has a sensor on the end (a 'dipper') to measure from a datum point on the grating inside the well house down to the surface of the water. When the sensor touches the water it beeps, and I read the tape measure. I take one dip every five minutes, for around an hour each side of low and high tide. Audio books and knitting help to fill in the intervening four minutes between dips! We aim to do 30 calibrations per year, at a mix of high and low tides, and try to select tides which have at least 1m (3ft) difference between the high and the low. As Rothera has a strange double-tide, sometimes there is only 30cm (1ft) difference between the highs and lows; this can mean dipping at unsociable hours to get a useful tide! The folks at POL are very appreciative of our work though, as it helps to improve their tide modelling and prediction systems for the whole of the Atlantic. It has also helped other organisations with tsunami modelling, as the 2004 Indian Ocean tsunami was detected by the tide sensor at Rothera, and earlier this year the recent earthquake in Chile caused a 20cm jump in the tide trace, and we could see that it took several days for the tide to settle back to normal. For those interested, Rothera's live tidal information can be seen here.

Mr Fish

As barely a fortnight can pass between birthdays, and on the theme of the sea, I present to you Mr Fish, the latest in a long line of creative birthday cakes. Mr Fish is for one of our GAs who, in the real world, is a keen fly-fisherman. Down here he contents himself with spending his evenings making flies and dreaming of trout-fishing in New Zealand.