Preprints
https://doi.org/10.5194/tc-2021-216
https://doi.org/10.5194/tc-2021-216

  02 Aug 2021

02 Aug 2021

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

A strong link between variations in sea-ice extent and global atmospheric pressure?

Jean-Louis Le Mouël, Fernando Lopes, and Vincent Courtillot Jean-Louis Le Mouël et al.
  • Institut de Physique du Globe, Paris University, Paris 75005, France

Abstract. Abstract. This paper reports spectral analyses, using Singular Spectral Analysis, of variations of the Arctic and Antarctic sea-ice extents (SI), and of the atmospheric surface pressure (AP) in both hemispheres (NH and SH). The ice-extents are dominated by a quasi-linear trend over the 42 yr period when data are available (1978–2020) and an annual component. Taken together, these two components represent more than 98 % of the signal variance. Both ice-extent series share the same 5 set of harmonics of the annual component (1/2, 1/3, 1/4 and 1/5 yr). The multi-decadal trends of sea-ice extent in the Arctic and Antarctic are of opposite sign. The series of harmonics of 1 year are consequences of the Earth’s revolution about the Sun. The components with period longer than a year form a set of even harmonics of the Schwabe cycle. The pressure series also exhibits the four harmonics of 1 year, that is not found in many series previously analysed in the same way. This could suggest a connection between variations in pressure and sea-ice extent. Geographical pressure structures (SSA trends) are stable on a 10 decadal to centennial time scale and exhibit a three-fold symmetry in the NH. In the SH that order-3 symmetry is altered by the Ross-Weddell “dipole” pressure anomaly. This anomaly is seen in maps of correlations of variations in sea-ice extent with atmospheric pressure, surface temperature and winds. It fits topographic forcing. There is phase opposition between the annual components of SI and AP in the SH, and the same decreasing phase lag from −30 to −60 days over 42 years for the four harmonic components of SHSI and SHAP. The (negative) sign of the trend of pressure and (positive) sign of the trend of temperature 15 beg for an explanation. The relative change in pressure over the past 50 years is two orders of magnitude smaller than that of warming. This relatively strong warming would be expected to have a larger effect on pressure. The ratio of relative changes of sea-ice extent vs pressure is 400 for the NH and 17 for the SH. The SSA components reported in this paper should help in understanding the mechanisms that govern changes in sea-ice extent: these changes reflect forcings related to the Earth’s revolution about the Sun on the shorter period side, and on the longer period side to the Sun and planets (Jupiter). Advanced 20 explanation of the physics underling these observations may need advances in solving the generalized Navier-Stokes equations, which is very difficult in the spherical case.

Jean-Louis Le Mouël et al.

Status: open (until 21 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on tc-2021-216', Paul PUKITE, 12 Aug 2021 reply
    • CC2: 'Reply on CC1', Fernando Lopes, 18 Aug 2021 reply
      • CC3: 'Reply on CC2', Paul PUKITE, 19 Aug 2021 reply
  • RC1: 'Comment on tc-2021-216', Anonymous Referee #1, 13 Aug 2021 reply

Jean-Louis Le Mouël et al.

Jean-Louis Le Mouël et al.

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Short summary
Variations of Arctic and Antarctic sea-ice exhibit a quasi-linear rate and an annual component. Trends in Arctic and Antarctic are of opposite sign. Both series share a set of harmonics of 1 year (1/2, 1/3, 1/4 and 1/5 yr), linked to the Earth’s revolution. The components with longer period form a set of even harmonics of the Schwabe cycle. The pressure series also exhibits the four harmonics of 1 year. These observations suggest a connection between variations in pressure and sea-ice extent.