Sea‐Level Trend Uncertainty With Pacific Climatic Variability and Temporally‐Correlated Noise

Abstract

AbstractRecent studies have identified climatic drivers of the east‐west see‐saw of Pacific Ocean satellite altimetry era sea level trends and a number of sea‐level trend and acceleration assessments attempt to account for this. We investigate the effect of Pacific climate variability, together with temporally‐correlated noise, on linear trend error estimates and determine new time‐of‐emergence (ToE) estimates across the Indian and Pacific Oceans. Sea‐level trend studies often advocate the use of auto‐regressive (AR) noise models to adequately assess formal uncertainties, yet sea level often exhibits colored but non‐AR(1) noise. Standard error estimates are over‐ or under‐estimated by an AR(1) model for much of the Indo‐Pacific sea level. Allowing for PDO and ENSO variability in the trend estimate only reduces standard errors across the tropics and we find noise characteristics are largely unaffected. Of importance for trend and acceleration detection studies, formal error estimates remain on average up to 1.6 times those from an AR(1) model for long‐duration tide gauge data. There is an even chance that the observed trend from the satellite altimetry era exceeds the noise in patches of the tropical Pacific and Indian Oceans and the south‐west and north‐east Pacific gyres. By including climate indices in the trend analysis, the time it takes for the observed linear sea‐level trend to emerge from the noise reduces by up to 2 decades.