Preprints
https://doi.org/10.5194/tc-2023-74
https://doi.org/10.5194/tc-2023-74
14 Jun 2023
 | 14 Jun 2023
Status: this preprint is currently under review for the journal TC.

Sea ice cover in the Copernicus Arctic Regional Reanalysis

Yurii Batrak, Bin Cheng, and Viivi Kallio-Myers

Abstract. The Copernicus Arctic Regional Reanalysis (CARRA) is a novel regional high-resolution atmospheric reanalysis product that covers a considerable part of the European Arctic including substantial amounts of ice-covered areas. Sea ice in CARRA is modelled by means of a one-dimensional thermodynamic sea ice parameterisation scheme, which also explicitly resolves the evolution of the snow layer over sea ice. In the present study we assess the representation of sea ice cover in the CARRA product and validate it against a wide set of satellite products and observations from ice mass balance buoys. We show that sea ice cover in CARRA adequately represents general interannual trends towards thinner and warmer ice in the Arctic. Compared to ERA5, sea ice in CARRA shows a reduced warm bias in the ice surface temperature. The strongest improvement was observed for winter months over the Central Arctic, and the Greenland and Barents seas where a 4.91 °C median ice surface temperature error of ERA5 is reduced to 1.88 °C in CARRA on average. Over the Baffin Bay, intercomparisons suggest the presence of a cold winter-time ice surface temperature bias in CARRA. No improvement over ERA5 was found in the ice surface albedo with spring-time errors in CARRA being up to 8 % higher on average than those in ERA5 when computed against the CLARA-A2 satellite retrieval product. Summer-time ice surface albedos are comparable in CARRA and ERA5. Sea ice thickness and snow depth in CARRA adequately resolve the annual cycle of sea ice cover in the Arctic and bring added value compared to ERA5. However, limitations of CARRA indicate potential benefits of utilising more advanced approaches for representing sea ice cover in next generation reanalyses.

Yurii Batrak et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2023-74', Anonymous Referee #1, 01 Aug 2023
  • RC2: 'Comment on tc-2023-74', Anonymous Referee #2, 07 Sep 2023

Yurii Batrak et al.

Yurii Batrak et al.

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Short summary
Atmospheric reanalysis products provide consistent series of atmospheric and surface parameters in a convenient gridded form. In this paper we study the quality of sea ice in a recently released regional reanalysis and assess its benefits compared to a global reanalysis. We found that a more detailed representation of sea ice in the regional reanalysis leads to its better performance, however there are limitations indicating potential value of using more advanced approaches in the future.