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General questions & answers
Question answered

Below is a selection of questions that have been asked by members of the public. The normal NERC disclaimers apply to any advice given.

  1. Where can I find the predicted times and heights of the tide at UK locations?
  2. Where can I obtain UK sea level data?
  3. What is meant by terms such as 'a large high tide'?
  4. Is the tide the same everywhere in the British Isles?
  5. Where can I find data on long term sea level changes measured at UK sites?
  6. Are long term changes in sea level the same everywhere around the UK?
  7. How much has global sea level risen in the past 100 years, how much will it rise in the next 100 and why is it rising anyway?
  8. How will a rise of 50 cm affect the UK?
  9. I am retiring soon and I want to buy a house by the sea. I have heard about climate change and I want to ask, is this a sensible thing to do?
  10. Where can I find out more about tides, storm surges, sea level changes and climate change, and the effects of the latter on the UK?
  11. How often do tsunamis (tidal waves) affect the UK?


1. Where can I find the predicted times and heights of the tide at UK locations?

Tidal predictions for today and for the next few days is provided freely by POL for a selection of UK ports.

Internet address: http://www.pol.ac.uk/home/tides/ (for standard browsers e.g. IE4+, Netscape)

WAP address http://www.pol.ac.uk/wap/ (for wap devices e.g. wap phones, wap emulators)
Notes for wap devices
Use the link hilighted in red and input it into your WAP browser. Do not forget to include the last forward slash (WML language is not as forgiving as html)


2. Where can I obtain UK sea level data?

(e.g. 15 minute or hourly values of sea level measured by the UK National Tide Gauge Network; recorded values of high and low waters; annual maximum and minimum levels etc.) Sea level data recorded at UK tide gauge stations are data banked and can be obtained from by National Tidal & Sea Level Facility.


3. What is meant by terms such as 'a large high tide'?

Oceanographers refer to the observed level of the sea at any moment as 'sea level' or 'still water level' (i.e. the level not including high frequency changes due to waves). This level includes components due to the 'astronomical tide' (due to the Moon and the Sun, see ), to the action of winds and air pressures especially at times of major storms (known as 'storm surges') and to changes in the mean level (due to climate change or to vertical land movements - see below). Terms such as 'tide level' and 'sea level' are often confused. For example, an especially 'high tide' in winter would be most likely a result of a large value of the astronomical tide superimposed upon which is a storm surge.


4. Is the tide the same everywhere in the British Isles?

No. Tidal ranges (the difference in height between high and low tide) are largest in the Bristol Channel and other parts of the eastern Irish Sea and in the Channel Islands than, for example, along the East Anglian coastline and in the western Irish Sea.
An important safety point is that, because tides are not the same everywhere, one must not assume that tidal information from London, for example (often included in diaries) applies elsewhere. Coastal users should always obtain copies of local tide tables.


5. Where can I find data on long term sea level changes measured at UK sites?



Monthly and annual mean values of sea level measured at UK sites since the 19th century are contributed to the international Permanent Service for Mean Sea Level (PSMSL).

Annual mean values of sea level from Aberdeen, North Shields, Sheerness, Newlyn and Liverpool, which are the five longest sea level records in the UK, are shown in the figure to the right.

Time series from over 40 other UK locations can be obtained from the
National Tidal & Sea Level Facility web pages. All NTSLF data are provided freely.


6. Are long term changes in sea level the same everywhere around the UK?

No. Long term changes in sea level measured at the coast (e.g. by tide gauges) are a consequence of 'real' changes in the level of the ocean (e.g. due to climate change), to which must be added changes in the level of the land.


Estimated rates (mm/yr) of crustal movement. Positive values indicate emergence (land rising relative to MSL).
Most knowledge of the pattern of vertical land movements in the UK comes from geological data. The map to the right was constructed by scientists at Durham University showing uplift in Scotland versus submergence in SE England. This 'tilting' of the UK is largely a consequence of a geological process caled Glacial Isostatic Adjustment (GIA).

It results in sea level rising less rapidly in Scotland than in southern England (compare Aberdeen and Sheerness in the above figure). Land level changes are now being investigated by POL and Nottingham University using the Global Position System and Absolute Gravity techniques.


7. How much has global sea level risen in the past 100 years, how much will it rise in the next 100 and why is it rising anyway?

Global-average sea level is believed to have risen by between 10-20 cm during the past century (e.g. see the change at Newlyn in above figure which is typical of many records worldwide) and best estimates are that it will rise by approximately 50 cm in the next 100 years (i.e. an acceleration of a factor of 3 in the rate). Rising sea levels are largely a consequence of the thermal expansion of the ocean, melting of low latitude glaciers (Alps, Rockies etc.) and many other factors, each of which are reviewed every few years by the Intergovernmental Panel on Climate Change (IPCC) .


8. How will a rise of 50 cm affect the UK?

As an example, a rise of 15 cm in sea level on the east coast of England, where there are extensive areas of low-lying land, roughly doubles the probability of over-topping a coastal structure (such as a sea wall) due to tide and storm surge. Consequently, a rise of 50 cm (i.e. approximately 3*15 cm) would result in an order of magnitude (i.e. 8-fold) increased probability. Population centres and valuable infrastructure will require enhanced protection.





The so-called '1000 year return period' level, shown in the opposite map, is the level (of order 10 m or so above mean sea level) which should be exceeded only every 1000 years given the present-day statisics of tide and storm surge. By definition almost, these will also be the areas which will be most affected by a rise of mean sea level.



Map of coastal areas of England and Wales with elevation below the 1000-year return period levels computed at POL.


9. I am retiring soon and I want to buy a house by the sea. I have heard about climate change and I want to ask, is this a sensible thing to do?

It is probably as sensible as it would be without climate change, given the ferocity of winter storms even in 'normal' times. The rise of 50 cm projected for the next 100 years is expected to occur mostly in the second half of the next century. Consequently, rises of level for the next 20-30 years (your remaining lifetime) can be expected to be similar to those for the past 30 years (of order 10 cm). You should enquire from your local authorities what their policy is for coastal protection in your area, taking into consideration the potential sea level changes in the future. If coastal protection is not adequate already, climate change will make the problem worse.


10. Where can I find out more about tides, storm surges, sea level changes and climate change, and the effects of the latter on the UK?

Pugh, D.T., 1987. Tides, Surges and Mean Sea-Level, A Handbook for Engineers and Scientists. Chichester: John Wiley & Sons, 472pp. [ISBN 0 471 91505 X]

PSMSL training/reports/manuals web pages


11. How often do tsunamis (tidal waves) affect the UK?

Not very often, as the Atlantic has fewer tsunamis in general than the Pacific or Indian Oceans, and it is difficult to identify small tsunamis without the otherwise energetic tide gauge records. However, two famous examples in the historical record may be quoted..

Storegga landslip
Along the coasts of the northern North Sea, Norwegian sea and north eastern Atlantic ocean a very prominent sand layer was originally thought to have been deposited by a storm surge. More recently, it has been attributed to a large tsunami circa 7,100 years ago. This event was generated in the Norwegian sea as a result of the Second Storegga submarine slide, one of the world's largest underwater slides.

Lisbon earthquake (1755)
Probably the most destructive tsunami in Europe during historical times occured on 1st November 1755. An earthquake (now know as the Lisbon Earthquake) took place 200 km offshore from Portugal. The subsequent tsunami destroyed a large part of Lisbon and raised sea levels at Newlyn (Cornwall, UK) by up to 3 metres in ten minutes.
Further information on tsunamis and tsunami risks


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