Evaluation of Four Satellite-Derived High-Resolution Operational Sea Ice Concentration Products for Determination of Marginal Ice Zones Around Svalbard

Marginal ice zone (MIZ) is a transitional region between dense pack ice and open water. It is a highly dynamic zone under strong interactions between the atmosphere, ocean, sea ice and waves, playing a crucial role in the polar climate and ecosystem. Accurate determination of MIZ is therefore essential for advancing our understanding, modeling and prediction of the polar climate system. In this paper, we introduce and apply a suite of MIZ-related metrics to evaluate the performance of four satellite-derived high-resolution operational sea ice concentration (SIC) products in determination of the MIZs around Svalbard, using the Norwegian ice chart as reference. The metrics used for evaluation include sea ice extent (SIE), MIZ extent (MIZE), length of ice edge (LIE), integrated ice edge error (IIEE), integrated MIZ error (IME), ice edge distance error (IEDE), and MIZ width error (MWE). The evaluation is based on three years of daily SIC data (2023-2025) from four products, including the Bremen AMSR2 SIC data from the University of Bremen (Bremen SIC), the Resolution-enhanced AMSR2 SIC (RE SIC) and Multisensor SIC products (Multisensor SIC) from the Norwegian Meteorological Institute, and the Automated Sea Ice Product (ASIP) from the Copernicus Marine Environment and Monitoring Service (CMEMS) (ASIP SIC). To be consistent with the Norwegian ice chart, the MIZ is defined as MIZ70 and MIZ90, corresponding to SIC thresholds of up to 0.7 and 0.9, respectively. IEDE and MWE are calculated using two types of LIE, the reference LIE (LIEr) from the Norwegian ice chart and the average LIE (LIEa) by averaging the ice chart LIE and the concerned LIE from the four satellite products. The results demonstrate that all four satellite SIC products generally capture the evolution of the sea ice conditions around Svalbard well, but differ in their accuracy when determining the ice edge and MIZs. The Bremen SIC product tends to overlook areas with low SIC, leading to a significant underestimation of SIE and a large IIEE. However, it provides an overall close agreement with the ice chart for the MIZ90 metrics (MIZE, IME and MWE). The RE and ASIP SIC products exhibit strong performance in capturing the ice edge and total SIE, with the ASIP product particularly excelling in accurately representing the ice edge and MIZ70. The Multisensor provides the closest agreement with the ice chart for the IME90, MWE90 and MWEa70, and ranks as the second-best product for the IIEE, IME70 and MWEr70. These results suggest that SAR and Low-frequency AMSR2 channels are especially effective for capturing the lower bounds of the MIZ, while high-frequency channels are more suitable for defining the upper bounds. Despite these strengths, the complex summer surface conditions pose significant challenges for satellite sensors in determining the ice edge and the MIZ, resulting in higher IEDE and MWE values during this period. These results highlight both the capabilities and limitations of satellite-based data in determining the MIZ, particularly under challenging summer conditions. Accurate determination of MIZs may require significant advancements in satellite observation technologies, retrieval algorithms, and more robust methods for integrating multiple sources.