A model study of factors influencing projected changes in regional sea level over the twenty-first century (original) (raw)

Abstract

In addition to projected increases in global mean sea level over the 21st century, model simulations suggest there will also be changes in the regional distribution of sea level relative to the global mean. There is a considerable spread in the projected patterns of these changes by current models, as shown by the recent Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment (AR4). This spread has not reduced from that given by the Third Assessment models. Comparison with projections by ensembles of models based on a single structure supports an earlier suggestion that models of similar formulation give more similar patterns of sea level change. Analysing an AR4 ensemble of model projections under a business-as-usual scenario shows that steric changes (associated with subsurface ocean density changes) largely dominate the sea level pattern changes. The relative importance of subsurface temperature or salinity changes in contributing to this differs from region to region and, to an extent, from model-to-model. In general, thermosteric changes give the spatial variations in the Southern Ocean, halosteric changes dominate in the Arctic and strong compensation between thermosteric and halosteric changes characterises the Atlantic. The magnitude of sea level and component changes in the Atlantic appear to be linked to the amount of Atlantic meridional overturning circulation (MOC) weakening. When the MOC weakening is substantial, the Atlantic thermosteric patterns of change arise from a dominant role of ocean advective heat flux changes.

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Notes

  1. In the course of answering reviewer comments we found that for one model (GISS-ER) the difference between the global thermal expansion provided by the modelling groups, and alternatively calculated using subsurface model temperature data provided in the CMIP3 database, was sufficiently large as to give some concern about the accuracy of the steric component patterns for this model. Excluding this model from our analysis of steric components would not affect the conclusions in this paper.
  2. If the GISS-ER model is excluded, the ensemble mean correlation between the sea level and steric component changes increases to 0.74 and the minimum correlation for the ensemble increases to 0.39.
  3. The iap model is excluded as it has a near collapsed MOC in the latter part of its twentieth century simulation (Meehl et al. 2007 their Fig. 10.15).

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Acknowledgments

This work was supported by the Joint DECC and Defra Integrated Climate Programme—DECC/Defra (GA01101). The multi-model dataset used for the AR4 analysis was archived by the World Climate Research Programme’s (WCRP’s) Coupled Model Intercomparison Project phase 3 (CMIP3). We acknowledge the international modelling groups for providing their data for analysis. We thank Mat Collins and the Met Office QUMP team for providing the two QUMP ensembles analysed in this study. We thank Michael Vellinga and Chris Brierley for access to the non-fluxadjusted QUMP coupled model ensembles referred to. We also thank the reviewers for their useful comments and suggestions.

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Authors and Affiliations

  1. Met Office, Hadley Centre, FitzRoy Road, Exeter, Devon, EX1 3PB, UK
    Anne K. Pardaens, J. M. Gregory & J. A. Lowe
  2. Department of Meteorology, Walker Institute for Climate System Research, University of Reading, Earley Gate, PO Box 243, Reading, RG6 6BB, UK
    J. M. Gregory

Authors

  1. Anne K. Pardaens
  2. J. M. Gregory
  3. J. A. Lowe

Corresponding author

Correspondence toAnne K. Pardaens.

Additional information

An erratum to this article can be found at http://dx.doi.org/10.1007/s00382-010-0817-z

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Pardaens, A.K., Gregory, J.M. & Lowe, J.A. A model study of factors influencing projected changes in regional sea level over the twenty-first century.Clim Dyn 36, 2015–2033 (2011). https://doi.org/10.1007/s00382-009-0738-x

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