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The color of sea level: importance of spatial variations in spectral shape for assessing the significance of trends

By C. W. Hughes and S. D. P. Williams

Abstract

We investigate spatial variations in the shape of the spectrum of sea level variability, based on a homogeneously-sampled 12-year gridded altimeter dataset. We present a method of plotting spectral information as color, focusing on periods between 2 and 24 weeks, which shows that significant spatial variations in the spectral shape exist,\ud and contain useful dynamical information. Using the Bayesian Information Criterion, we determine that, typically, a 5th order autoregressive model is needed to capture the structure in the spectrum. Using this model, we show that statistical errors in fitted local trends range between less than 1 and more than 5 times what would be calculated assuming “white” noise, and the time needed to detect a 1 mm/yr trend ranges between about 5 years and many decades. For global-mean sea level, the statistical error reduces to 0.1 mm/yr over 12 years, with only 2 years needed to detect a 1 mm/yr trend. We find significant regional differences in trend from the global mean. The\ud patterns of these regional differences are indicative of a sea level trend dominated by dynamical ocean processes, over this perio

Topics: Marine Sciences
Publisher: AGU
Year: 2010
DOI identifier: 10.1029/2010JC006102
OAI identifier: oai:nora.nerc.ac.uk:10399

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