Drivers of Interannual Sea Level Variability on the Northwestern European Shelf

Tim H J Hermans,Jonathan Tinker,Dewi Le Bars,Theo Gerkema,Carolina M L Camargo,Aimée B A Slangen,Francisco M Calafat,Caroline A Katsman

doi:10.1029/2020jc016325

Abstract

AbstractSea level on the northwestern European shelf (NWES) varies substantially from year to year. Removing explained parts of interannual sea level variability from observations helps to improve estimates of long‐term sea level trends. To this end, the contributions of different drivers to interannual sea level variability need to be understood and quantified. We quantified these contributions for the entire NWES by performing sensitivity experiments with a high‐resolution configuration of the Regional Ocean Modeling System (ROMS). The lateral and atmospheric boundary conditions were derived from reanalyses. We compared our model results with satellite altimetry data and used our sensitivity experiments to show that nonlinear feedbacks cause only minor interannual sea level variability on the shelf. This indicates that our experiments can be used to separate the effects of different drivers. We find that wind dominates the variability of annual mean sea level in the southern and eastern North Sea (up to 4.7‐cm standard deviation), whereas the inverse barometer effect dominates elsewhere on the NWES (up to 1.7‐cm standard deviation). In contrast, forcing at the lateral ocean boundaries results in small and coherent variability on the shelf (0.5‐cm standard deviation). Variability driven by buoyancy fluxes ranges from 0.5‐ to 1.3‐cm standard deviation. The results of our sensitivity experiments explain the (anti)correlation between interannual sea level variability at different locations on the NWES and can be used to estimate sea level rise from observations in this region with higher accuracy.

Highlights

Sea level on the northwestern European shelf (NWES) has been rising since the nineteenth century (Wahl et al, 2013), and this rise is projected to accelerate in the coming centuries (e.g., Church et al, 2013; Oppenheimer et al, 2019)
We find that wind dominates the variability of annual mean sea level in the southern and eastern North Sea, whereas the inverse barometer effect dominates elsewhere on the NWES
In Regional Ocean Modeling System (ROMS) and GLORYS12v1, the 0‐cm mean dynamic topography (MDT) contour realistically follows the northern coast of Scotland and approximately traces the 80‐m isobath into the North Sea

Summary

Introduction

Sea level on the northwestern European shelf (NWES) has been rising since the nineteenth century (Wahl et al, 2013), and this rise is projected to accelerate in the coming centuries (e.g., Church et al, 2013; Oppenheimer et al, 2019). Removing explained parts of variability from sea level records can lead to more accurate estimates of trends and accelerations Drivers of sea level variability on the NWES have mainly been studied using the long tide gauge (TG) records that are available in the region. A link has been found between the North Atlantic Oscillation (NAO) and sea level on the NWES (Chen et al, 2014; Tsimplis & Shaw, 2008; Tsimplis et al, 2005; Wakelin et al, 2003; Woolf et al, 2003)

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Discussion

Conclusion