Preprints
https://doi.org/10.5194/cp-2021-69
https://doi.org/10.5194/cp-2021-69
22 Jun 2021
 | 22 Jun 2021
Status: this discussion paper is a preprint. It has been under review for the journal Climate of the Past (CP). The manuscript was not accepted for further review after discussion.

Synchronous Northern and Southern Hemisphere response of the westerly wind belt to solar forcing

Nathalie Van der Putten, Florian Adolphi, Anette Mellström, Jesper Sjolte, Cyriel Verbruggen, Jan-Berend Stuut, Tobias Erhardt, Yves Frenot, and Raimund Muscheler

Abstract. It has been suggested from observations that the 11-year solar cycle influences regional tropospheric temperature and circulation relatively symmetrically around the equator. During periods of low (high) solar activity, the mid-latitude storm tracks are weakened (strengthened) and shifted towards the equator (poles). The mechanisms behind solar influence on climate are still debated and evidence from paleoclimate records often lacks precise dating required for assessing the global context. Well-dated proxy-based evidence for solar activity and natural climate change exist for the Northern Hemisphere, suggesting pattern similar to today for periods of grand solar minima. However, well-dated and high-resolution terrestrial climate reconstructions are lacking for the Southern Hemisphere. Here we present a unique precisely dated record for past changes in humidity and windiness from the Crozet archipelago at 46° S in the Southern Indian Ocean, a site strongly influenced by the westerly wind belt. We find an increased influence of the westerly winds shortly after 2800 cal year BP synchronous with a major decline in solar activity and significant changes in Northern Hemisphere mid-latitude wind and humidity records. Supported by a general circulation model run encompassing a grand solar minimum, we infer that periods of low solar activity are connected to an equator-ward shift of the mid-latitude westerly wind belts in both hemispheres comparable to the climate reaction to 11-year solar cycle variability inferred from reanalysis data. We conclude that solar forcing is connected to the bipolar climate response about 2800 years ago through synchronous changes in atmospheric circulation of similar sign in both hemispheres.

Nathalie Van der Putten et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-69', Anonymous Referee #1, 23 Aug 2021
  • RC2: 'Comment on cp-2021-69', Anonymous Referee #2, 22 Sep 2021
  • RC3: 'Comment on cp-2021-69', Anonymous Referee #3, 01 Oct 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-69', Anonymous Referee #1, 23 Aug 2021
  • RC2: 'Comment on cp-2021-69', Anonymous Referee #2, 22 Sep 2021
  • RC3: 'Comment on cp-2021-69', Anonymous Referee #3, 01 Oct 2021

Nathalie Van der Putten et al.

Nathalie Van der Putten et al.

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Short summary
In recent decades, Southern Hemisphere westerlies (SHW) moved equator-ward during periods of low solar activity leading to increased winds/precipitation at 46° S, Indian Ocean. We present a terrestrial SHW proxy-record and find stronger SHW influence at Crozet, shortly after 2.8 ka BP, synchronous with a climate shift in the Northern Hemisphere, attributed to a major decline in solar activity. The bipolar response to solar forcing is supported by a climate model forced by solar irradiance only.