Mechanisms of aerosol-forced AMOC variability in a state of the art climate model

Matthew B. Menary*, Christopher D. Roberts, Matthew D. Palmer, Paul R. Halloran, Laura Jackson, Richard A. Wood, Wolfgang A. Müller, Daniela Matei, Sang Ki Lee

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

41 Citations (Scopus)

Abstract

Mechanisms of sustained multidecadal changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) are investigated in a set of simulations with a new state-of-the-art Earth system model. Anthropogenic aerosols have previously been highlighted as a potential mitigator of AMOC weakening. In this study, we explain the oceanic mechanisms behind how anthropogenic aerosols force a strengthening of the AMOC by up to 20% in our state-of-the-art Earth system model. This strengthening is driven via atmospheric circulation changes which subsequently modulate the salinity budget of the North Atlantic subpolar gyre. Gradual salinification occurs via increased evaporation and decreased fluxes of ice through the Fram Straits. A component of the salinification is a positive feedback from the AMOC bringing more saline water northwards from the subtropical Atlantic. Salinification of the subpolar gyre results in increased deep convection and a strengthening of the AMOC. Following a reduction in aerosol concentrations, the AMOC rapidly weakens, approximately 3 times faster than in the case where anthropogenic aerosol concentrations had never been increased. Similarities and differences with available observational records and long term reanalysis products are also discussed. Key Points Aerosols force a long term AMOC strengthening in HadGEM2-ES of ~3Sv This occurs via atmospheric circulation modulating the NA freshwater budget Independent ocean models and atmospheric analyses provide qualitative support

Original languageEnglish
Pages (from-to)2087-2096
Number of pages10
JournalJournal of Geophysical Research: Oceans
Volume118
Issue number4
DOIs
Publication statusPublished - Apr 2013

Keywords

  • aerosols
  • amoc
  • atlantic
  • circulation
  • cmip5
  • overturning

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