von Albedyll, Luisa (2024): Sea ice lead fractions from SAR-derived sea ice divergence in the Transpolar Drift during MOSAiC 2019/2020 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.963671

Leads and fractures in sea ice play a crucial role in the heat and gas exchange between the ocean and the atmosphere, impacting atmospheric, ecological, and oceanic processes. The precise knowledge of the aerial coverage, location, and formation history of leads is thus of great importance for polar research. Leads result from sea ice deformation processes. The breaking of the sea ice, followed by divergent ice motion, forms leads. Since the magnitude of divergence is directly proportional to the lead width, divergence is a powerful indicator of the location and width of leads. Divergence derived from satellite synthetic-aperture radar (SAR) data provides this information independent of the presence of clouds. We present here lead fractions from daily divergence fields in the Transpolar Drift along the drift of the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in 2019/2020. The lead fractions have a spatial resolution of 700 m and are based on divergence from Sentinel-1 imagery with an original spatial resolution of 50 m ( doi:10.1594/PANGAEA.958449). Typically, the time between two scenes was one day, with a few exceptions of 2-3 days, and the size of the scenes was on average 200 x 200 km. Lead fractions are available from 7 October 2019 to 14 January 2020 and from 15 March 2020 to 1 June 2020. Lead fractions are regularly gridded in Polar Stereographic North projection (latitude of true scale: 70°N, center longitude: 45°W) within a bounding box corresponding to 180°/60°N: -3314693.24, -3314693.24, 3314693.24, 3314693.24. Divergence alone only detects leads when they form or continue to open. To determine if a lead is closed, opened further, or stayed open, we use the divergence and convergence fields of subsequent dates and accumulate them after adjusting lead fractions from different dates to a common location using sea ice drift data. With this dataset, the data user can study (accumulated) lead fractions (adjusted to a common location) for the last 10 time instances. The data user can choose the age of the leads (typically 1-11 days) they wish to include in their analysis. In addition, the user can understand when and where a lead has formed or closed. We evaluate the accumulated divergence-derived lead fractions against existing lead products along the MOSAiC drift track (von Albedyll, et al, in review).