Sea-Level Rise for the Coasts of California, Oregon, and Washington Past, Present, and Future (2012) / Chapter Skim
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2 Measured Global Sea-Level Rise
2 Measured Global Sea-Level Rise
Pages 23-32
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From page 23... ...
This chapter describes TIDE GAGES how sea level is measured and summarizes rates of sealevel rise estimated since the IPCC Fourth Assessment Tide gages measure the water level at the location Report was published. of the gage (Box 2.2)
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. Sampling bias due to the small number of tide gages, By averaging the water levels measured at the gage particularly before 1950, and their concentration in the over a long period of time (daily, monthly)
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Today, electronic sensors or bubbler gages have replaced tide gage floats. Two organizations collect and preserve tide gage records from around the world: the Global Sea Level Observing System, which has established a network of 290 tide gages worldwide; and the Permanent Service for Mean Sea Level, which stores and disseminates the tidal records from more than 2,000 stations around the world.
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From page 26... ...
Their results are shown in Figure 2.1, compared to other independent estimates of global sea-level rise from tide gages. The time dependency of global sea level can be seen in the analysis of Church and White (2011)
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From page 27... ...
similar to IPCC (2007) rates estimated from satel- argued that this result reflects the choice of start date lite altimetry and confirmed by tide gages (see results (1930)
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From page 28... ...
and, to a smaller extent, to mean sea level is calculated by averaging measurements sampling biases. Satellite altimetry records are shorter of sea-surface height made by the various altimeters, than tide gage records but cover more of the global three of which are currently operating, which revisit a ocean (81.5°N81.5°S in Figure 2.5)
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From page 29... ...
The sea surface is estimated by averaging measurements taken over a 10-, 17-, or 35-day satellite track repeat cycle. The accuracy of the sea surface height measurements for TOPEX-class altimetry systems, considered to be the most accurate among the radar altimetry missions due to their optimal orbital sampling and high instrument precision, is a few cm (1 )
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TOPEX 60 GEOSAT/GM GEOSAT/ERM Jason-1/TM 40 ENVISAT Jason-1 20 ERS-2 ERS-1 0 -20 1985 1990 1995 2000 2005 2010 Year FIGURE 2.3 Global sea-level rise trends from different satellite altimeters for 19852010. The measured trend is 2.6 ± 0.4 mm yr-1, and the trend corrected for glacial isostatic adjustment and atmospheric effects is 2.9 ± 0.4 mm yr-1.
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From page 31... ...
The thick blue line represents yearly sea-level changes from a moving average of tide gage observations, and the shaded area represents the sea-level uncertainty, which reflects the number of gage sites used in the global averages, the number of data points, and the standard deviations of the fit of seasonal signals and the trend of the original gage time series. The thick red line is the yearly averaged altimetry sea-level data.
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From page 32... ...
Such satellite altimetry and tide gages. The higher rates of an acceleration has not yet been detected.
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