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