National Weather Service Alaska Sea Ice Program: Gridded ice concentration maps for the Alaskan Arctic

Abstract. There are many challenges associated with obtaining high-fidelity sea ice concentration (SIC) information, and products that rely solely on passive microwave measurements often struggle to represent conditions at low concentration, especially within the Marginal Ice Zone and during periods of active melt. Here, we present a new SIC product for the Alaskan Arctic generated by the National Weather Service Alaska Sea Ice Program (hereafter referred to as ASIP) that synthesizes a variety of satellite SIC and in-situ observations from 2007–present. These SIC fields have been primarily used for operational purposes and have not yet been gridded or independently validated. In this study, we first grid the ASIP product into 0.05° resolution in both latitude and longitude. We then perform extensive intercomparison with an international database of ship-based in-situ SIC observations, supplemented with observations from Saildrones. Additionally, an intercomparison between three ice products is performed: (i) ASIP, (ii) a high-resolution passive microwave product (AMSR2), and (iii) an operational product available from the National Snow and Ice Data Center that originates at the National Ice Center (MASIE). This intercomparison demonstrates that all products perform similarly when compared to in-situ observations generally, but ASIP outperforms the other products during periods of active melt and in low SIC regions. Furthermore, we show that the similarity in performance among products is due to the in-situ asset distribution, as most in-situ observations are far from the ice edge in locations where all products agree. We find that the ASIP ice edge is generally farther south than both the AMSR2 and MASIE ice edges, by an average of approximately 55 km in the winter and 175 km in summer for ASIP vs. AMSR2, and 60 km in the winter and 130 km in the summer for ASIP vs. MASIE.