Preprints
https://doi.org/10.5194/acp-2021-688
https://doi.org/10.5194/acp-2021-688

  13 Sep 2021

13 Sep 2021

Review status: this preprint is currently under review for the journal ACP.

Interactions between the stratospheric polar vortex and Atlantic circulation on seasonal to multi-decadal timescales

Oscar Dimdore-Miles1, Lesley Gray1,2, Scott Osprey1,2, Jon Robson2,3, Rowan Sutton2,3, and Bablu Sinha4 Oscar Dimdore-Miles et al.
  • 1Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, OX1 3PU, UK
  • 2National Centre for Atmospheric Science
  • 3Department of Meteorology, University of Reading, Reading, RG6 6ET
  • 4National Oceanography European Way, Southampton SO14 3ZH

Abstract. Variations in the strength of the Northern Hemisphere winter polar stratospheric vortex can influence surface variability in the Atlantic sector. Disruptions of the vortex, known as sudden stratospheric warmings (SSW), are associated with an equatorward shift and deceleration of the North Atlantic jet stream, negative phases of the North Atlantic Oscillation as well as cold snaps over Eurasia and North America. Despite clear influences at the surface on sub-seasonal timescales, how stratospheric vortex variability interacts with ocean circulation on decadal to multi-decadal timescales is less well understood. In this study, we use a 1000-year pre-industrial control simulation of the UK Earth System Model to study such interactions using a wavelet analysis technique to examine non-stationary periodic signals in the vortex and ocean. We find that intervals which exhibit persistent anomalous vortex behaviour lead to oscillatory responses in the Atlantic Meridional Overturning Circulation (AMOC). The origin of these responses appears to be highly non-stationary with spectral power in vortex variability and the AMOC at periods of 30 and 50 years. In contrast, AMOC variations on longer timescales (near 90-year periods) are found to lead to a vortex response, through a pathway involving the equatorial Pacific and Quasi-biennial Oscillation. Using the relationship between persistent vortex behaviour and the AMOC response established in the model, we use a regression analysis to estimate the potential contribution of the 8 year SSW hiatus interval in the 1990s to the recent negative trend in AMOC observations. The result suggests that approximately 30 % of the trend may have been caused by the SSW hiatus.

Oscar Dimdore-Miles et al.

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Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-688', Anonymous Referee #1, 03 Oct 2021

Oscar Dimdore-Miles et al.

Oscar Dimdore-Miles et al.

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Short summary
This study examines interactions between variations in the strength of polar stratospheric winds and circulation in the north Atlantic in a climate model simulation. It finds that the Atlantic Meridional Overturning Circulation (AMOC) responds with oscillations to sets of consecutive northern hemisphere winters which show all strong or all weak polar vortex conditions. The study also shows that a set of strong vortex winters in the 1990s contributed to the recent slowdown in the observed AMOC.
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