Tania Kovats biography

Time and Tide Bell

A Continuing Arts Programme facing Lincolnshire's Coast


The tide is a wave that connects us

COTIDAL is an ambitious new creative artwork by the UK born artist Tania Kovats, commissioned by the Time and Tide Bell Organisation.

Kovats will soon begin the making of a digital film that is 24 hours and 50 minutes long, the length of a lunar day. The film will track the movement of high tide around the UK featuring the Time and Tide bell locations. The content of the film will be made up of community contributions, films and sound recordings, edited with Kovats’ own filmed material, and woven together to make a cinematic almanac of the tides for our small island.

More information here

The first chapter of this film will be located in the South West of England, starting with Appledore, North Devon, where the first Time and Tide Bell was placed. It is being funded by a grant from the Arts Council.

Everybody can contribute, from anywhere (there's only one sea) by making a short video on your phone that answers in your own way this question:

What do you see when you see the sea?

To see how to upload your video, click here.

William Whewell's 1838 chart of cotidal isoclines.

COTIDAL will be a film that is 24 hours and 50 minutes long, the length of a lunar day. The film will track the movement of high tide around the UK with material from the Time and Tide bell locations as the content for the filmThis will be made up of community contributions, films, sound recordings, images, that are harvested and edited together with material shot on camera under the direction of Tania Kovats. Cotidal would have an immersive accompanying soundscape. The film will be screened over a 24 hour and 50 minutes time period as a celebratory community event, happening at all the Time and Tide Bell locations and will then be screened online. There are remarkably few very long films. Cotidal will make it into the top ten of Wikipedia’s List of Longest Films. It will probably be the most interesting of the top ten to watch!

To use the work of William Whewell as a starting point is profound. This polymath is not as well known as he should be; his contribution to the philosophy of science underpins the work of all climate scientists today. His work on tides speaks directly to our project. He instituted the first large scale citizen science project, organising the simultaneous recording of tides around the coast, and then, so importantly, collating the accumulated data into a visual form in his chart of tidal isoclines. His innovation, converting a numerical data-set to visual representation, is today taken for granted. It provides a step towards the bridge between science and art. Whewell's Essay towards a First Approximation to a Map of Cotidal Lines, Philosophical Transactions of the Royal Society of London Vol. 123 (1833), pp. 147-236 can be found here

He wrote:
It will easily be understood that we may draw a line through all the adjacent parts of the ocean which have high water at the same time; for instance, at 1 o’clock on a given day. We might draw another line through all the places which have high water at 2 o’clock on the same day, and so on. Such lines may be called cotidal lines; and they will be the principal subject of the present essay.

William Whewell (1794 - 1866)
Eden Upton Eddis, Lithograph 1835

Sometimes adding colour to a map makes some features of the data being conveyed easier to appreciate. Sometimes it just makes it look prettier. Here's Whewell's 1836 chart again with each of the 12 hourly cotidal zones a different colour.

Biff Vernon ~ Reprint of Whewell's 1836 cotidal chart, pastel. 48 x 50 cm

Sea level rise as ice melts

As global heating proceeds, thermal expansion of the oceans’ waters raises sea level, but a much greater contribution to the rise over coming decades and centuries will be the melting of glaciers and ice sheets. While water seeks its own level the rise in sea level will not be the same around the world, some coasts will experience greater a rise than other places. The dynamic, changing, pattern of winds and ocean currents, push water up on some coasts but away from other places. The gravitational pull of large ice masses, the Greenland and Antarctic ice sheets, increase the hight of the ocean’s surface near the poles but as the ice melts this effect lessons and the water slopes away. The effect results in sea level actually falling in the North Atlantic while rising excessively in equatorial regions. In the southern hemisphere, melting of the West Antarctic Ice Sheet produces a similar effect.

Just as William Whewell depicted the sea surface height with cotidal lines on his tide chart, we can draw analogous isoclines showing how the sea surface height varies with ice mass loss from the big ice sheets. These two charts show, separately, the effects of melt in Greenland (b) and West Antarctica (c). They show the resulting difference in sea surface height from the global mean sea level.

Maps from Mapping Sea-Level Change in Time, Space, and Probability. Benjamin P. Horton et al. Annual Review of Environment and Resources Vol. 43:481-521 2018.

Here's the YouTube version of the paper, updated to November 2020, in which Professor Ben Horton explains all.

While the inexorable rise in mean sea level, greater or lesser in various parts of the world, will have existential impacts on coastal communities, it is not mean sea level that causes the destruction but the high tides augmented by storm surges. The astronomically predicted tides are made dangerous by the weather. The first published weather map that used isobaric lines to show the air pressure, as Whewell had done with his cotidal lines, was created by Sir Francis Galton four decades later. Isobars are now a familiar feature of synoptic charts but the three dashed lines labled with mercury barometer readings in inches on Galton's map were a first for readers of The Times in April 1975. The rapid collection of the data was made possible by the introduction of the telegraph system but it was the conversion of numerical data to a visual image that allowed human understanding.

Sir Francis Galton prepared the first weather map, published in The Times on April 1 1875, but it was not a forecast; it showed the weather from the previous day, March 31.

Flooding from storm surges are the critical threat to lives and property and their prediction is vital. The National Tidal and Sea Level Facility (NTSLF) is the UK centre of excellence for sea level monitoring, coastal flood forecasting and the analysis of sea level extremes. It is the focus for sea level research in the UK and for its interpretation into advice for policy makers, planners and coastal engineers. Their storm-surge model runs in real-time forecasting sea level a few hours ahead, at locations around Britain. Access it from here.

This map was a prediction of the sea level during a storm surge in 1999, the isoclines given visual prominance by colours not available to Whewell or Galton.
An animation of a storm surge is available here showing how the surge flows around Britain in a similar way to that in which the tides moves.