Changes in extreme regional sea surface height due to an abrupt weakening of the Atlantic meridional overturning circulation

S.-E Brunnabend,M Van Meersbergen,F Seinstra,H E Bal,J Maassen,B Van Werkhoven,H A Dijkstra,M A Kliphuis

doi:10.5194/os-10-881-2014

S.-E Brunnabend, M Van Meersbergen + Show 6 more

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https://doi.org/10.5194/os-10-881-2014

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Abstract

Abstract. As an extreme scenario of dynamical sea level changes, regional sea surface height (SSH) changes that occur in the North Atlantic due to an abrupt weakening of the Atlantic meridional overturning circulation (AMOC) are simulated. Two versions of the same ocean-only model are used to study the effect of ocean model resolution on these SSH changes: a high-resolution (HR) strongly eddying version and a low-resolution (LR) version in which the effect of eddies is parameterised. The weakening of the AMOC is induced in both model versions by applying strong freshwater perturbations around Greenland. A rapid decrease of the AMOC in the HR version induces much shorter return times of several specific regional and coastal extremes in North Atlantic SSH than in the LR version. This effect is caused by a change in main eddy pathways associated with a change in separation latitude of the Gulf Stream.

Highlights

The global mean rate of sea level rise over the twentieth century, as deduced from tide gauges, is about 1.7±0.5 mm yr−1 (Bindoff et al, 2007; Church and White, 2011)
The main aim of this study is to investigate the impact of an abrupt Atlantic meridional overturning circulation (AMOC) decline due to Greenland Ice Sheet (GrIS) freshwater input on extremes in regional sea surface height in the North Atlantic
4 Summary, discussion and conclusion and Brunnabend et al (2012), which have shown that an increase in the amount of freshwater perturbation leads to an

Summary

Introduction

The global mean rate of sea level rise over the twentieth century, as deduced from tide gauges, is about 1.7±0.5 mm yr−1 (Bindoff et al, 2007; Church and White, 2011). In a recent study of water levels from tide gauges, Merrifield et al (2013) identified, apart from tidal and seasonal components, non-tidal residual components as an important contribution to annual maximum water levels. Such non-tidal residuals can result from highfrequency storms and processes on sub-annual timescales. Firing and Merrifield (2004) indicated, through an example near Hawaii in September 2003, that mesoscale eddies may have an important influence on extreme sea levels They describe an eddy that gave rise to extreme sea levels as it coincided with high sea levels in both seasonal and longer (decadal) timescale components

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