A lead-width distribution for Antarctic sea ice: a case study for the Weddell Sea with high-resolution Sentinel-2 images

Abstract

Abstract. Using Copernicus Sentinel-2 images we derive a statistical lead-width distribution for the Weddell Sea. While previous work focused on the Arctic, this is the first lead-width distribution for Antarctic sea ice. Previous studies suggest that the lead-width distribution follows a power law with a positive exponent; however their results for the power-law exponents are not all in agreement with each other. To detect leads we create a sea-ice surface-type classification based on 20 carefully selected cloud-free Sentinel-2 Level-1C products, which have a resolution of 10 m. The observed time period is from November 2016 until February 2018, covering only the months from November to April. We apply two different fitting methods to the measured lead widths. The first fitting method is a linear fit, while the second method is based on a maximum likelihood approach. Here, we use both methods for the same lead-width data set to observe differences in the calculated power-law exponent. To further investigate influences on the power-law exponent, we define two different thresholds: one for open-water-covered leads and one for open-water-covered and nilas-covered leads. The influence of the lead threshold on the exponent is larger for the linear fit than for the method based on the maximum likelihood approach. We show that the exponent of the lead-width distribution ranges between 1.110 and 1.413 depending on the applied fitting method and lead threshold. This exponent for the Weddell Sea sea ice is smaller than the previously observed exponents for the Arctic sea ice.

Distribution Characteristics and Influencing Factors of Sea Ice Leads in the Weddell Sea, Antarctica

“…Overall, our algorithm exhibited the capability to accurately identify 87.16% of the lead structures. A previous study showed that band 4 (665 nm) of Sentinel-2 is the best choice for SIL identification [22]; thus, the reflectance of band 4 was chosen for comparison with the identification results for evaluation in this paper. The comparison of SILs detected from Sentinel-2 images and MODIS images is depicted in Figure 3, which is arranged in the order, Sentinel-2 original band 4 image, Sentinel-2 leads map, and MODIS leads map.…”

“…In contrast, research on Antarctica SIL primarily focused on the identification algorithm [21,22], and there is a need for more comprehensive research to explore the distribution characteristics of SILs and their correlation with meteorological and hydrological factors. A notable oceanographic feature in the Southern Ocean is the Weddell Gyre (WG).…”

Lead fractions from SAR-derived sea ice divergence during MOSAiC

“…Satellites have monitored the spatial distribution and temporal evolution of Arctic lead fraction since the 1990s (Key et al, 1993;Lindsay and Rothrock, 1995;Miles and Barry, 1998). Lead detection based on thermal infrared (TIR, Willmes and Heinemann, 2016;Hoffman et al, 2022;Wang et al, 2022;Qiu et al, 2023) and visible images (e.g., Lewis and Hutchings, 2019;Muchow et al, 2021) was complemented by classification of Synthetic Aperture Radar (SAR) backscatter (e.g., Murashkin et al, 2018), radar altimeters (e.g., CryoSat-2 Hendricks et al, 2021a), laser altimeters (e.g, ICESat-2 Duncan and Farrell, 2022), and passive microwave (PMW) data (e.g., Röhrs et al, 2012). The transient nature of leads and their narrow appearance sets limits to the detection of leads from satellites.…”