Preprints
https://doi.org/10.5194/cp-2021-156
https://doi.org/10.5194/cp-2021-156
 
29 Nov 2021
29 Nov 2021
Status: a revised version of this preprint was accepted for the journal CP and is expected to appear here in due course.

Influence of long-term changes in solar irradiance forcing on the Southern Annular Mode

Nicky M. Wright1,2,a, Claire E. Krause1,3,b, Steven J. Phipps4, Ghyslaine Boschat5, and Nerilie J. Abram1,2 Nicky M. Wright et al.
  • 1Research School of Earth Sciences, Australian National University, Canberra ACT 2601, Australia
  • 2ARC Centre of Excellence for Climate Extremes, Australian National University, Canberra ACT 2601, Australia
  • 3ARC Centre of Excellence for Climate System Science, Australian National University, Canberra ACT 2601, Australia
  • 4Ikigai Research, Sandy Bay, Tasmania 7006, Australia
  • 5Bureau of Meteorology and ARC Centre of Excellence for Climate Extremes, Melbourne, Victoria 3001, Australia
  • acurrent address: School of Geosciences, University of Sydney, NSW 2006, Australia
  • bcurrent address: Geoscience Australia, Canberra ACT, Australia

Abstract. The Southern Annular Mode (SAM) is the leading mode of climate variability in the extratropical Southern Hemisphere, with major regional climate impacts. Observations, reconstructions, and historical climate simulations all show positive trends in the SAM since the 1960s; however, earlier trends in palaeoclimate SAM reconstructions cannot be reconciled with last millennium simulations. Here we investigate the sensitivity of the SAM to solar irradiance variations using simulations with a range of constant solar forcing values, and last millennium transient simulations with varying amplitude solar forcing scenarios. We find the mean SAM state can be significantly altered by solar irradiance changes, and that transient last millennium simulations using a high-amplitude solar scenario have an improved and significant agreement with proxy-based SAM reconstructions. Our findings suggest that the effects of solar forcing on high-latitude climate may not be adequately incorporated in most last millennium simulations, due to solar irradiance changes that are too small and/or the absence of interactive atmospheric chemistry in global climate models.

Nicky M. Wright et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-156', Anonymous Referee #1, 18 Feb 2022
  • RC2: 'Comment on cp-2021-156', Anonymous Referee #2, 22 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-156', Anonymous Referee #1, 18 Feb 2022
  • RC2: 'Comment on cp-2021-156', Anonymous Referee #2, 22 Mar 2022

Nicky M. Wright et al.

Nicky M. Wright et al.

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Short summary
The Southern Annular Mode (SAM) is a major mode of climate variability. Proxy-based SAM reconstructions show large changes that last millennium climate models cannot reproduce. We explore the SAM's sensitivity to solar forcing by using simulations with a range of constant solar values, and transient last millennium simulations with stronger solar variations. We find that changes in solar forcing can influence the SAM, and that our transient simulations better match proxy-based reconstructions.