Trends in UK mean sea level revisited

Abstract

SUMMARY This paper presents estimates of rates of mean sea level (MSL) change around the UK, based on a larger tide gauge data set and more accurate analysis methods than have been employed so far. The spatial variation of the trend in MSL is found to be similar to that inferred from geological information and from advanced geodetic techniques, which is a similar conclusion to that arrived at in the previous studies. The tide gauge MSL trends for 1901 onwards are estimated to be 1.4 ± 0.2 mm yr−1 larger than those inferred from geology or geodetic methods, suggesting a regional sea level rise of climate change origin several one‐tenths of mm per year lower than global estimates for the 20th century. However, UK MSL change cannot be described in terms of a simple linear increase alone but includes variations on interannual and decadal timescales. The possible sources of variation in a ‘UK sea level index’ are explored. Air pressure is clearly one such possible source but its direct local forcing through the ‘inverse barometer’ accounts for only one‐third of the observed variability. A number of larger scale atmospheric and ocean processes must also play important roles, but modelling them satisfactorily and separating the individual contributions present a major challenge. As regards future regional UK sea level changes, we conclude that there is no basis for major modification to existing projections for the 2080s included in the 2002 UK Climate Impacts Programme studies.

Evidence for the accelerations of sea level on multi‐decade and century timescales

“…It has been discussed in various forms through the years as the tide gauge records have lengthened. For example, Woodworth (1987Woodworth ( , 1990) remarked on the relative lowering of UK and European sea level during the 1970s and 1980s, while Tsimplis and Baker (2000), Tsimplis and Josey (2001) and Tsimplis et al (2005) attempted to explain the even stronger change in Mediterranean sea-level trends after 1960 in terms of regional hydrography and meteorological forcing related to the NAO. From Figure 3, it can be seen that much of the continuing sea-level rise had the post-1960s flattening-off not occurred, was restored and exceeded by the higher rates of the 1990s and possibly before (cf Church et al, 2004;Church and White 2006;Holgate and Woodworth, 2004;Rahmstorf et al, 2007).…”

New Estimates of Present-Day Crustal/Land Motions in the British Isles Based on the BIGF Network

“…Furthermore, most of these stations have only been in-stalled since about 2004 and others have been frequently moved or shutdown. In view of this, only about 30 stations were considered suitable for geophysical applications in recent publications which considered data up to 31 December 2005 (Bradley et al, 2009;Teferle et al, 2009;Woodworth et al, 2009). Furthermore, these 30 stations provided a fairly inhomogeneous station distribution, with a lack of stations in the geophysically interesting areas of Scotland and Northern Ireland.…”

Observed mean sea level changes around the North Sea coastline from 1800 to present

“…In the most recent assessment, Woodworth et al (2009a) estimated that geocentric (or 'absolute') mean sea level (AMSL) around the UK rose by 1.4 ± 0.2 mm/yr over the 20 th century. Wahl et al (2011) considered this to be the best estimate for 20 th century sea level changes in the North Sea area, as there was evidence for significant correlation between an updated UK sea level index and long MSL records from other European coastlines (Woodworth et al, 2009a).…”

“…Major reviews of changes in UK MSL have been conducted on about a decadal basis over the last 30 years (i.e. Woodworth, 1987;Woodworth et al, 1999Woodworth et al, , 2009a.…”