Dynamical downscaling of unforced interannual sea-level variability in the North-West European shelf seas
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Dynamical downscaling of unforced interannual sea‑level variability in the North‑West European shelf seas Jonathan Tinker1 · Matthew D. Palmer1 · Dan Copsey1 · Tom Howard1 · Jason A. Lowe1,4 · Tim H. J. Hermans2,3 Received: 16 October 2019 / Accepted: 13 July 2020 © The Author(s) 2020
Abstract Variability of Sea-Surface Height (SSH) from ocean dynamic processes is an important component of sea-level change. In this study we dynamically downscale a present-day control simulation of a climate model to replicate sea-level variability in the Northwest European shelf seas. The simulation can reproduce many characteristics of sea-level variability exhibited in tide gauge and satellite altimeter observations. We examine the roles of lateral ocean boundary conditions and surface atmospheric forcings in determining the sea-level variability in the model interior using sensitivity experiments. Variability in the oceanic boundary conditions leads to uniform sea-level variations across the shelf. Atmospheric variability leads to spatial SSH variability with a greater mean amplitude. We separate the SSH variability into a uniform loading term (change in shelf volume with no change in distribution), and a spatial redistribution term (with no volume change). The shelf loading variance accounted for 80% of the shelf mean total variance, but this drops to ~ 60% around Scotland and in the southeast North Sea. We analyse our modelled variability to provide a useful context to coastal planners and managers. Our 200-year simulation allows the distribution of the unforced trends (over 4–21 year) of sea-level changes to be quantified. We found that the 95th percentile change over a 4-year period can lead to coastal sea-level changes of ~ 58 mm, which must be considered when using smooth sea level projections. We also found that simulated coastal SSH variations have long correlation length-scales, suggesting that observations of interannual sea-level variability from tide gauges are typically representative of > 200 km of the adjacent coast. This helps guide the use of tide gauge variability estimates. Keywords Regional sea-level variability · Northwest European shelf seas · Dynamic downscaling · Unforced climate variability · Present-day control simulation
1 Introduction
This paper is dedicated to Dylan Alexander Taharua Tinker Vega, who was born during the final stages of the writing of this paper. Dylan is “born of the sea” in Welsh, and Taharua is “to be of two cultures” in Māori, reflecting his Spanish and New Zealand heritage. In remembrance of Doug Nicoll (1/6/1979– 17/5/2020). Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00382-020-05378-0) contains supplementary material, which is available to authorized users. * Jonathan Tinker [email protected] Extended author information available on the last page of the article
Relative sea-level change is one of the most important aspects of a changing climate. In addition to an anthropogenic driven trend in
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