Abstract
Abstract. Although the global mean sea-level budget for the 20th century can now be closed, the understanding of sea-level change on a regional scale is still limited. In this study we compare observations from tide gauges to regional patterns from various contributions to sea-level change to see how much of the regional measurements can be explained. Processes that are included are land ice mass changes and terrestrial storage changes with associated gravitational, rotational and deformational effects, steric/dynamic changes, atmospheric pressure loading and glacial isostatic adjustment (GIA). The study focuses on the mean linear trend of regional sea-level rise between 1961 and 2003. It is found that on a regional level the explained variance of the observed trend is 0.87 with a regression coefficient of 1.07. The observations and models overlap within the 1σ uncertainty range in all regions. The main processes explaining the variability in the observations appear to be the steric/dynamic component and the GIA. Local observations prove to be more difficult to explain because they show larger spatial variations, and therefore require more information on small-scale processes.
Highlights
Church et al (2004) used tide gauge measurements in combination with satellite information to estimate past regional distributions of sea-level change, and regional variations observed by satellites could be reproduced with ocean circulation models (e.g. Wunsch et al, 2007; Lombard et al, 2009), but these methods do not allow for the identification of individual processes contributing on regional scales
In order to estimate the magnitude of various contributing processes to regional sea-level change, Plag (2006) scaled fingerprints of secular trends in steric changes, ice sheets, and glacial isostatic adjustment (GIA) to match tide gauge records, which led to an explained variance of 15 %
The central questions of this study are how well can this set of contributing processes explain the tide gauge (TG) observations, and are there processes which are leading the explanation of regional sea-level trends? We show the regional patterns of the various processes (Sect. 3.1), compare both individual TG observations and regional averages (Sects. 3.2, 3.3), and examine the effect of variations in the individual contributions (Sect. 4.1)
Summary
Rising sea levels may have serious impacts on coastal communities in the near future (Nicholls and Cazenave, 2010), and sea-level change is a central topic in climate change. Church et al (2004) used tide gauge measurements in combination with satellite information to estimate past regional distributions of sea-level change, and regional variations observed by satellites could be reproduced with ocean circulation models (e.g. Wunsch et al, 2007; Lombard et al, 2009), but these methods do not allow for the identification of individual processes contributing on regional scales. TGs are devices attached to the earth’s surface which measure local variations in relative sea level They have a sparse spatial coverage but provide long data series compared to satellites. A process that is not included in this study is vertical land movement from subsidence or tectonics These changes can be measured by GPS, which can be compared to the TG time series, but only for short time series and in limited locations
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