Preprints
https://doi.org/10.5194/egusphere-2022-354
https://doi.org/10.5194/egusphere-2022-354
23 May 2022
 | 23 May 2022

Interannual to decadal sea level variability in the subpolar North Atlantic: The role of propagating signals

Denis L. Volkov, Claudia Schmid, Leah Chomiak, Cyril Germineaud, Shenfu Dong, and Marlos Goes

Abstract. The gyre-scale, dynamic sea surface height (SSH) variability signifies the spatial redistribution of heat and freshwater in the ocean, influencing the ocean circulation, weather, climate, sea level, and ecosystems. It is known that the first empirical orthogonal function (EOF) mode of the interannual SSH variability in the North Atlantic exhibits a tripole gyre pattern, with the subtropical gyre varying out-of-phase with both the subpolar gyre and the tropics, influenced by the low-frequency North Atlantic Oscillation. Here, we show that the first EOF mode explains the majority (60–90 %) of the interannual SSH variance in the Labrador and Irminger Seas, whereas the second EOF mode is more influential in the northeastern part of the subpolar North Atlantic (SPNA), explaining up to 60–80 % of the regional interannual SSH variability. We find that the two leading modes do not represent physically independent phenomena. On the contrary, they evolve as a quadrature pair associated with a propagation of SSH anomalies from the eastern to the western SPNA. This is confirmed by the complex EOF analysis, which can detect propagating (as opposed to stationary) signals. The analysis shows that it takes about 2 years for sea level signals to propagate from the Iceland Basin to the Labrador Sea, and it takes 7–10 years for the entire cycle of the North Atlantic SSH tripole to complete. The observed westward propagation of SSH anomalies is linked to shifting wind stress curl patterns and to the cyclonic pattern of the mean ocean circulation in the SPNA. The analysis of regional surface buoyancy fluxes in combination with the upper-ocean temperature and salinity changes suggests a time-dependent dominance of either air-sea heat fluxes or advection in driving the observed SSH tendencies, while the contribution of surface freshwater fluxes (precipitation and evaporation) is negligible. We demonstrate that the most recent cooling and freshening observed in the SPNA since about 2010 was mostly driven by advection associated with the North Atlantic Current. The results of this study indicate that signal propagation is an important component of the North Atlantic SSH tripole, as it applies to the SPNA.

Journal article(s) based on this preprint

15 Dec 2022
Interannual to decadal sea level variability in the subpolar North Atlantic: the role of propagating signals
Denis L. Volkov, Claudia Schmid, Leah Chomiak, Cyril Germineaud, Shenfu Dong, and Marlos Goes
Ocean Sci., 18, 1741–1762, https://doi.org/10.5194/os-18-1741-2022,https://doi.org/10.5194/os-18-1741-2022, 2022
Short summary

Denis L. Volkov et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-354', Alan Fox, 11 Jul 2022
    • AC1: 'Reply on RC1', Denis Volkov, 15 Sep 2022
  • RC2: 'Comment on egusphere-2022-354', Anonymous Referee #2, 06 Aug 2022
    • AC2: 'Reply on RC2', Denis Volkov, 15 Sep 2022
  • EC1: 'Comment on egusphere-2022-354', Karen J. Heywood, 15 Sep 2022

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-354', Alan Fox, 11 Jul 2022
    • AC1: 'Reply on RC1', Denis Volkov, 15 Sep 2022
  • RC2: 'Comment on egusphere-2022-354', Anonymous Referee #2, 06 Aug 2022
    • AC2: 'Reply on RC2', Denis Volkov, 15 Sep 2022
  • EC1: 'Comment on egusphere-2022-354', Karen J. Heywood, 15 Sep 2022

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Denis Volkov on behalf of the Authors (18 Sep 2022)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (30 Sep 2022) by Karen J. Heywood
RR by Anonymous Referee #2 (31 Oct 2022)
ED: Publish subject to minor revisions (review by editor) (31 Oct 2022) by Karen J. Heywood
AR by Denis Volkov on behalf of the Authors (09 Nov 2022)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (10 Nov 2022) by Karen J. Heywood
AR by Denis Volkov on behalf of the Authors (12 Nov 2022)

Journal article(s) based on this preprint

15 Dec 2022
Interannual to decadal sea level variability in the subpolar North Atlantic: the role of propagating signals
Denis L. Volkov, Claudia Schmid, Leah Chomiak, Cyril Germineaud, Shenfu Dong, and Marlos Goes
Ocean Sci., 18, 1741–1762, https://doi.org/10.5194/os-18-1741-2022,https://doi.org/10.5194/os-18-1741-2022, 2022
Short summary

Denis L. Volkov et al.

Denis L. Volkov et al.

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Short summary
Ocean and atmosphere dynamics redistribute heat and freshwater, which drives regional sea level changes. This study reports on the east-to-west propagation of sea level anomalies in the subpolar North Atlantic, mainly associated with advection by the mean flow – an important component of the leading mode of interannual sea level variability in the region. This variability mainly results from oceanic advection and air-sea heat fluxes, whose relative contributions are space- and time-dependent.