UK Sea Level Trends

By Paul Homewood

 

A lot is said about sea level rise, much of it nonsense. But what really matters is its impact on local areas.

With that in mind, let’s do a round up of the situation around the UK’s coast.

 

We have nine tidal gauges with records over the last 30 years, and we can compare the changes since 1983 with the changes in the last decade. ( Data is only available up to 2013 – it is likely to be July before last year’s numbers are uploaded at the official PSMSL site).

 

 

Figure 1

 

Figure 1 gives the relative sea level rise, expressed as mm/year. In seven out of nine cases, the rate of rise in the last decade has been less than over the full 30 years.

 

Since the end of the ice age, parts of the British landmass have been rising, as the weight of the glaciers was lifted. This is typically the north west of the country. Conversely, the rest of the country has been tilted down, and is consequently sinking.

There is a good article here, describing work by scientists from Durham University, which includes this map.

 

Long term rate of relative land- and sea-level change in the British Isles. Rates in mm, showing land uplift as positive and subsidence as negative.

 

In their reconstruction of global sea levels up to 2009, Church & White produced much more detailed estimates of vertical land movement, based on GPS measurements and other methods (details here). Using these, we can calculate what is known as the absolute sea level rise, as opposed to the relative sea level rise, which is what the tide gauges measure, as in Figure 1.

[All tidal gauge data and GIA numbers are in the Appendix]

 

 

Figure 2

 

The highest rate of ASLR in the last decade is at Devonport, amounting to 2.83mm/year. At the other sites, the rise is much less, and in five cases negative.

The crude average rate of rise is 1.26mm since 1983, and a fall of 0.54mm/year in the last ten years.

 

Two sites, Newlyn and North Shields have records back to 1923 and earlier. The relative sea level rise for the 30-year periods are:-

 

Figure 3

 

Figure 4

 

In both cases, sea level rise in the last 30 years has been well below earlier periods.

The conclusion, as far as the UK is concerned, is clear. Far from accelerating, as we are told global sea level rise is, sea level rise has actually been decelerating in both the last 30 years, and in the last decade.

Certainly around the south and east coasts, it is the effect of the land sinking which is the principal problem. Where the land is actually rising, there is little or no relative sea level rise at all.

Rack my brain as I try, I cannot remember DEFRA, the Met Office or any other official body telling us this.

 

 

NOTES

1) All tidal gauge data is from the Permanent Service for Mean Sea Level, PSMSL. 

http://www.psmsl.org/data/obtaining/

2) No actual data for 1983 was available for North Shields or Stornaway. Estimates have been made from the average of 1982 and 1984.

 

 

APPENDIX 

 

Annual Mean Sea Level Data – mm

	1983	2003	2013
Aberdeen	7024	7076	7026
N Shields	6963	7045	7015
Lowestoft	7045	7108	7104
Portsmouth	7087	7083	7068
Devonport	7023	7061	7092
Newlyn	7091	7139	7140
Ullapool	7133	7146	7151
Stornaway	6990	7068	7065
Holyhead	7013	7028	7043

 

 

 

Global Isostatic Adjustment per Church & White

	GIA falling/(rising)
Aberdeen	-0.26
N Shields	-0.03
Lowestoft	0.22
Portsmouth	0.14
Devonport	0.27
Newlyn	0.4
Ullapool	-0.38
Stornaway	-0.38
Holyhead	-0.11

 

 

 

Annual Mean Sea Level Data – mm

	1923	1953	1983	2013
N Shields	6784	6918	6963	7015
Newlyn	6927	6998	7091	7140