Preprints
https://doi.org/10.5194/cp-2020-133
https://doi.org/10.5194/cp-2020-133

  20 Oct 2020

20 Oct 2020

Review status: a revised version of this preprint was accepted for the journal CP.

Quantifying paleo-reconstruction skill of the Southern Annular Mode in a model framework

Willem Huiskamp1,2 and Shayne McGregor3 Willem Huiskamp and Shayne McGregor
  • 1RD1 – Earth System Analysis, Potsdam-Institute for Climate Impact Research (PIK), Member of the Leibniz Association, Potsdam, Brandenburg, Germany
  • 2Climate Change Research Centre, UNSW Sydney, Sydney, NSW, Australia
  • 3School of Earth Atmosphere and Environment, Monash University, Melbourne, Victoria, Australia

Abstract. Past attempts to reconstruct the Southern Annular Mode (SAM) using paleo archives have resulted in records which can differ significantly from one another prior to the window over which the proxies are calibrated. This study attempts to quantify not only the skill with which we may expect to reconstruct the SAM, but also assess the contribution of regional bias in proxy selection and the impact of non-stationary proxy-SAM teleconnections on a resulting reconstruction. This is achieved using a pseudo-proxy framework with output from the CM2.1 global climate model. Reconstructions derived from precipitation fields perform better, with 89 % of reconstructions calibrated over a 61 year window able to reproduce at least 50 % of inter-annual variance in the SAM, as opposed to just 25 % for surface temperature (SAT) derived reconstructions. Non-stationarity of proxy-SAM teleconnections, as defined here, plays a negligible role in reconstructions, however the range in reconstruction skill is not negligible. Reconstructions were most likely to be skilful when proxies are sourced from a geographically broad region, with a network size of 70 proxies.

Willem Huiskamp and Shayne McGregor

 
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Status: final response (author comments only)
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Willem Huiskamp and Shayne McGregor

Model code and software

Scripts for Analysis and plotting Willem Huiskamp Ryan Batehup https://doi.org/10.5281/zenodo.4106517

Willem Huiskamp and Shayne McGregor

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Short summary
This study investigates the reliability of paleo-reconstructions of the Southern Annular Mode (SAM) using climate model data. We find that reconstructions are able to, at best, capture ~ 60 % of SAM variability, with poorer reconstructions managing only 35 %. Reconstructions perform best when they use a larger number of proxies, sourced from the entire Southern Hemisphere land mass. Future reconstructions should endeavour to address both sampling and proxy-SAM correlation stability uncertainties.