Abstract
Before the satellite era, global sea-level reconstructions depend on tide-gauge records and in-situ hydrographic observations. However, the available global mean sea-level (GMSL) reconstructions, using different methods, indicate a spread in sea-level trend over 1900-2008 (1.3∼2.0 mm yr−1). With better understanding of the causes of sea-level change, here we implement an improved sea-level reconstruction, building upon Church and White (2011), and including three additional factors: the sea-level fingerprints, the sterodynamic sea level (SDSL) climate change patterns and more complete local vertical land motion (VLM) estimates. The trend of new GMSL reconstruction is 1.6 ± 0.2 mm yr−1 (90% confidence level) over 1900-2019, consistent with the sum of observation-based sea-level contributions of 1.5 ± 0.2 mm yr−1. The lower trend from the new reconstruction compared with the earlier Church and White (2011) result is mainly due to the updated VLM correction. The inclusion of sea-level fingerprints and SDSL climate change patterns are the dominant contributors for the improved skill of regional reconstruction. Despite GMSL budget closure in terms of long-term trend since 1900, our study shows discrepancies between the trends from available GMSL reconstructions and the sum of independent observation-based contributions over different periods in the 20th century, e.g., the discrepancy at the beginning of the 20th century, which could be related to possible bias in the land ice component estimate. The reconstruction methodology developed here, as tested with synthetic sea-level fields, could provide a promising way to identify potential biases in the individual sea-level components constrained by available global tide-gauge observations.
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