Something (or someone) seems to be stirring in the usually sleepy village of Little Haven where the county council is proposing to reinforce the sea defences to prevent future flooding.
A petition with 125 signatures has been got up by disgruntled locals who are objecting to the defacement of their popular beach with rock armour and other civil engineering works.
It seems that any unusually high tide backed up by a storm surge is enough to send water cascading over the existing wall and through the gap provided by the slipway. And, we are told, with sea levels due to rise because of global warming matters can only get worse.
Having spent a good part of my young life at my grandparents’ place in Allonby, a little village on the Solway Firth, sea level rise is a subject in which I have longtime interest.
Allonby lies roughly halfway between Maryport and Silloth and the coastline between these two is essentially ten miles of Newgale beach.
Fortunately, sheltered from the wide Atlantic by Ireland and that bit of Scotland which sticks down on the western side of the Solway Firth, Allonby doesn’t suffer exposure to the huge Atlantic swells that cause havoc at Newgale, but I remember my grandmother telling me of the occasions when the sea overtopped the shingle bank and flooded the village.
It is a hazard coastal communities have long learned to live with.
However, we have a new threat – global warming – which we are told will cause sea levels to rise at an accelerating rate because of thermal expansion of the oceans and melting of land based ice sheets and glaciers.
Indeed, sea level has been rising, probably since the end of the Little Ice Age and certainly from before global warming became a factor.
The Department of Energy and Climate Change website carries records from the five oldest UK tide gauges from which it can be seen that for Aberdeen, at least, sea level has actually been falling in most recent years.
It might be thought a simple matter to measure sea level, but it isn’t.
The first problem is that the sea is neither flat, static nor level. And nor is the underlying earth.
And we mustn’t forget atmospheric pressure which can make a substantial difference to the height of tides.
So not only is the water level affected by tides, winds and waves but the earth’s crust is also on the move, most significantly by way of isostatic rebound as the earth regains its shape after being deformed by the weight of ice across the Northern Hemisphere during the last glaciation which was a mere 10,000 years ago.
As a result, areas of uplift such as Sweden, Canada and Russia give the impression of falling sea levels while more southerly parts are sinking, making sea level rises look worse than they really are.
All these variables make precise measurement difficult and the fact that over the past century global sea level has been rising at a rate of a mere 1.7 mm per year – the thickness of about ten sheets of paper – only makes things more complicated.
However, while given the potential errors 1.7 mm per year may be hardly noticeable, eight inches per century is fairly easy to detect.
Fortunately, we now have satellite altimetry which enables thousands of measurements to be taken which helps to iron out the variations caused by tides and waves.
A couple of months ago I attended a presentation by the county council’s flood defence department.
We were presented with a graph showing the eight inches of sea level rise, which, it is generally agreed, represents the history of the past century.
Then we were shown a photograph of Lower Town Fishguard (one of the five or six locations in Pembrokeshire that might be affected by sea level rises) on which was superimposed two lines – one representing a one metre rise and the other a two metre increase.
Now, a one metre rise in sea level would be serious, two metres fairly catastrophic, though it should also be remembered that for 90% of the time the tide is out and for another 95% high water is well below its maximum.
However, the sea level rise projected by the International Panel on Climate Change (IPCC) is well short of one metre (two metres is strictly for the fairies) so why we were presented with this photograph if not to put the wind up us.
In fact, in its Fifth Assessment Report (FAR) based on various computer simulations the IPCC projects sea level rise by the end of the century of about two feet.
And these sea level scenarios are based on the General Circulation Models (CGMs) which are used to provide projections of future temperature rises.
As these CGMs have failed completely to predict the 18 years, and counting, pause in the global temperatures it is perhaps unwise to set too much store by models that depend on their output.
However, global warming may not be all bad news because, according to the Daily Mail, researchers in Japan have discovered that increased temperatures result in the birth of more girls than boys.
It is not quite clear how this surprising result is arrived at – are there more girls in Africa, fewer in Finland? – but it sounds like good news for red-blooded males of the species.
Unfortunately this has all come rather late in the day for those of us who find ourselves on an ebbing tide, but we mustn’t be selfish.
The poet Philip Larkin had the same problem with the sexual revolution in the 1960s about which he wrote:
“Sexual intercourse began
In nineteen sixty-three
(which was rather late for me)
Between the end of the “Chatterley” ban
And the Beatles’ first LP”
And in another marine-centred development Pembrokeshire County Council’s environmental scrutiny committee is considering the introduction of a smoking ban on the county’s beaches.
According to Cllr Rev Huw George, the Cabinet member in charge of our moral welfare, the justification for this measure is that 4,000 people die in Wales each year from smoking related diseases and the ban will protect children because “Seeing adults smoking in areas where sports are taking place and children are playing helps to normalise smoking making it seem harmless.”
By happy coincidence research published this week appears to show that there are more cancer deaths attributable to obesity than to smoking.
So can we look forward to people with a body mass index greater than 25 being barred from stripping off when they visit the seaside in case children get the impression that vast areas of sagging flesh is the norm.
The Rev George might be well advised to keep his sermonising for Sunday mornings in the chapel.
Ironically, the chairman of this committee which seeks to set us on this journey of improvement is none other than our old friend Cllr Brian Hall.
Still, once they’ve covered Little Haven beach with boulders, there won’t be any place for people to sit – smokers and fatties alike.
A case of killing two birds with one stone, or several large stones to be precise.
For those interested in this sort of thing (sea level, not sex, or obesity) below is the IPCC’s explanation of the difficulties in making precise measurements of global average sea level.
FAQ 13.1: Why Does Local Sea Level Change Differ from the Global Average?
Shifting surface winds, the expansion of warming ocean water, and the addition of melting ice can alter ocean currents which, in turn, lead to changes in sea level that vary from place to place. Past and present variations in the distribution of land ice affect the shape and gravitational field of the Earth, which also cause regional fluctuations in sea level. Additional variations in sea level are caused by the influence of more localised processes such as sediment compaction and tectonics.
Along any coast, vertical motion of either the sea or land surface can cause changes in sea level relative to the land (known as relative sea level). For example, a local rise can be caused by an increase in sea surface height, or by a decrease in land height. Over relatively short time spans (hours to years), the influence of tides, storms and climatic variability – such as El Niño – dominates sea level variations. Earthquakes and landslides can also have an effect by causing changes in land height and, sometimes, tsunamis.
Over longer time spans (decades to centuries), the influence of climate change – with consequent changes in volume of ocean water and land ice – is the main contributor to sea level change in most regions. Over these longer time scales, various processes cause vertical motion of the land surface, which can also result in substantial changes in relative sea level.
Since the 1970s, satellites have measured the height of the ocean surface relative to the center of the Earth (known as geocentric sea level). These measurements show differing rates of geocentric sea level rise around the world during the past two decades (see FAQ 13.1, Figure 1).
For example, in the western Pacific Ocean, rates were about three times greater than the global mean value of about three millimeters a year. In contrast, those in the eastern Pacific Ocean are lower than the global mean value, with much of the west coast of the Americas experiencing a fall in sea surface height from 1993 to 2012.
Much of the spatial variation shown in FAQ 13.1, Figure 1 is a result of natural climate variability – such as El Niño and the Pacific Decadal Oscillation – over time scales from about a year to several decades. These climate variations alter surface winds, ocean currents, temperature and salinity, and hence affect sea level. The influence of these processes will continue during the 21st century, and will be superimposed on the spatial pattern of sea level change associated with longer term climate change, which also arises through changes in surface winds, ocean currents, temperature and salinity, as well as ocean volume.
However, in contrast to the natural variability, the longer term trends accumulate over time and so are expected to dominate over the 21st century. The resulting rates of geocentric sea level change over this longer period may therefore exhibit a very different pattern to that shown in FAQ 13.1, Figure 1. Tide gauges measure relative sea level, and so they include changes resulting from vertical motion of both the land and the sea surface.
Over many coastal regions, vertical land motion is small, and so the long-term rate of sea level change recorded by coastal and island tide gauges is similar to the global mean value (see records at San Francisco and Pago Pago in FAQ 13.1, Figure 1). In some regions, vertical land motion has had an important influence.
For example, the steady fall in sea level recorded at Stockholm (FAQ 13.1, Figure 1) is caused by uplift of this region after the melting of a large (>km thick) continental ice sheet at the end of the last Ice Age, between ~20,000 and ~9,000 years ago. Such on-going land deformation as a response to the melting of ancient ice sheets is a significant contributor to regional sea level changes in North America and northwest Eurasia, which were covered by large continental ice sheets during the peak of the last Ice Age.
In other regions, this process can also lead to land subsidence, which elevates relative sea levels, as it has at Charlottetown, where a relatively large increase has been observed, compared to the global mean rate (FAQ 13.1, Figure 1). Vertical land motion due to movement of the Earth’s tectonic plates can also cause departures from the global mean sea level trend in some areas – most significantly, those located near active subduction zones, where one tectonic plate slips beneath another.
For the case of Antofagasta (FAQ 13.1, Figure 1) this appears to result in steady land uplift and therefore relative sea level fall. In addition to regional influences of vertical land motion on relative sea level change, some processes lead to land motion that is rapid, but highly localised. For example, the greater rate of rise relative to the global mean at Manila (FAQ 13.1, Figure 1) is dominated by land subsidence caused by intensive ground water pumping. Land subsidence due to natural and anthropogenic processes, such as the extraction of ground water or hydrocarbons, is common in many coastal regions, in particular in large river deltas.
It is commonly assumed that melting ice from glaciers, or the Greenland and Antarctic ice sheets, would cause globally uniform sea level rise, much like filling a bath tub with water. In fact, such melting results in regional variations in sea level due to a variety of processes, including changes in ocean currents, winds, the Earth’s gravity field, and land height.
For example, computer models that simulate these latter two processes predict a regional fall in relative sea level around the melting ice sheets, because the gravitational attraction between ice and ocean water is reduced, and the land tends to rise as the ice melts (FAQ 13.1, Figure 2). However, further away from the ice sheet melting, sea level rise is enhanced, compared to the global average value.
In summary, a variety of processes drive height changes of the ocean surface and ocean floor, resulting in distinct spatial patterns of sea level change at local to regional scales. The combination of these processes produces a complex pattern of total sea level change, which varies through time as the relative contribution of each process changes.
The global average change is a useful single value which reflects the contribution of climatic processes – land-ice melting and ocean warming, and represents a good estimate of sea level change at many coastal locations. At the same time, however, where the various regional processes result in a strong signal, there can be large departures from the global average value.