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<p align="left">With the ongoing climate change, the Arctic region is experiencing rapid warming. This has a profound effect on the sea-ice cover and, as a result, on the surface albedo. Surface albedo has a large impact on the energy balance of the region: a decrease in surface albedo leads to increased absorption of solar radiation and thus higher temperatures, ultimately leading to the albedo decreasing further. Information on the surface albedo is therefore necessary for various applications and climate studies. Atmospheric reanalysis products answer this need, providing consistent multiyear datasets with good spatial coverage.</p> <p align="left">We have studied the Arctic sea-ice albedo in two reanalyses. First is ERA5, a global atmospheric reanalysis by the ECMWF (European Centre for Medium range Weather Forecasts). ERA5 has a horizontal resolution of 31 km, and sea-ice is modelled with a one-dimensional sea-ice parameterisation scheme.</p> <p align="left">The second reanalysis is CARRA (Copernicus Arctic Regional ReAnalysis), a regional atmospheric reanalysis covering a part of the Arctic with two overlapping domains: the western domain centred around Greenland and the eastern over the European Arctic. The horizontal resolution is 2.5 km, and similarly to ERA5, sea-ice is modelled with a one-dimensional thermodynamic sea-ice scheme.</p> <p align="left">We compare the surface albedo of these two reanalyses to the satellite-based black-sky surface albedo product of the CLARA-A2.1 dataset (CM SAF cLoud, Albedo and surface RAdiation dataset from AVHRR data). Comparisons are made for April to September, 2000-2015, for the sea areas of the CARRA domains. In addition to a general assessment, four different regions within the domains are studied separately.</p>

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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.