Preprints
https://doi.org/10.5194/egusphere-2024-413
https://doi.org/10.5194/egusphere-2024-413
22 Feb 2024
 | 22 Feb 2024

GREP reanalysis captures the evolution of the Arctic Marginal Ice Zone across timescales

Francesco Cocetta, Lorenzo Zampieri, Julia Selivanova, and Doroteaciro Iovino

Abstract. The recent development of data-assimilative reanalyses of the global ocean and sea ice enables a better understanding of the polar region dynamics and provides gridded descriptions of sea ice variables without temporal and spatial gaps. Here, we study the spatiotemporal variability of the Arctic sea ice area and thickness using the Global ocean Reanalysis Ensemble Product (GREP) produced and disseminated by the Copernicus Marine Service (CMS). GREP is compared and validated against the state-of-the-art regional reanalyses PIOMAS and TOPAZ, and observational datasets of sea ice concentration and thickness for the period 1993–2020. Our analysis presents pan-Arctic metrics but also emphasizes the different responses of ice classes, marginal ice zone (MIZ) and pack ice, to climate changes. This aspect is of primary importance since the MIZ has been widening and making up an increasing percentage of the summer sea ice as a consequence of the Arctic warming and sea ice extent retreat. Our results show that the GREP ensemble provides reliable estimates of present-day and recent past Arctic sea ice states and that the seasonal to interannual variability and linear trends in the MIZ area are properly reproduced, with ensemble spread often being as broad as the uncertainty of the observational dataset. The analysis is complemented by an assessment of the average MIZ latitude and its northward migration in recent years, a further indicator of the Arctic sea ice decline. There is substantial agreement between GREP and reference datasets in the summer. Overall, the GREP ensemble mean is an adequate tool for gaining an improved understanding of the Arctic sea ice, also in light of the expected warming and the Arctic transitions to ice-free summers.

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Francesco Cocetta, Lorenzo Zampieri, Julia Selivanova, and Doroteaciro Iovino

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-413', Anonymous Referee #1, 09 Apr 2024
    • AC2: 'Reply on RC1', Francesco Cocetta, 03 Jul 2024
  • RC2: 'Comment on egusphere-2024-413', Anonymous Referee #2, 11 May 2024
    • AC1: 'Reply on RC2', Francesco Cocetta, 03 Jul 2024
Francesco Cocetta, Lorenzo Zampieri, Julia Selivanova, and Doroteaciro Iovino

Model code and software

Scripts for "GREP reanalysis captures the evolution of the Arctic Marginal Ice Zone across timescales" F. Cocetta https://doi.org/10.5281/zenodo.10651276

Francesco Cocetta, Lorenzo Zampieri, Julia Selivanova, and Doroteaciro Iovino

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Short summary
Arctic sea ice thinning and retreating because of global warming. Thus, the region is transitioning to a new state featuring an expansion of the marginal ice zone, a region where mobile ice interacts with waves from the open ocean. By analyzing 30 years of sea ice reconstructions that combine numerical models and observations, this paper proves that an ensemble of global ocean and sea ice reanalyses is an adequate tool for investigating the changing Arctic sea ice cover.