ALBERT

Description: Divergent sea ice motion breaks the ice and opens fractures and leads. Depending on the air temperature, those open-water areas can quickly refreeze. The open water or thin ice in leads play a crucial role in the heat and gas exchange between the ocean and the atmosphere, impacting atmospheric, ecological, and oceanic processes. Leads can be detected from space, using different types of instruments, e.g., thermal infrared, passive microwave, active microwave, or optical sensors. The retrieval methods have different sensitivities, especially concerning the minimum lead width and the maximum ice thickness, different spatial resolutions, and different limits. We presented a time series of lead fractions from different lead products (Oct 2019 - May 2020) along the drift of the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in the Transpolar Drift. We compared 7 different lead products based on 1. accumulated divergence derived from SAR images, 2. divergence in linear kinematic features, 3. classified SAR data, 4. thermal infrared data from MODIS, 5. passive microwave data from AMSR-2, 6. radar altimetry from CryoSat-2 (lead fractions and total lead count), and 7. thermal infrared data from helicopter surveys. We extracted daily lead fractions in a circle with a radius of 50 km along the drift of MOSAiC. Data is available from 5 October 2019 to 15 May 2020 with shorter time series for some of the sensors. We found that the mean lead fractions varied by 1 magnitude across different lead products due to different physical lead and sea ice properties observed by the sensors and methodological factors such as spatial resolution. Thus, the choice of lead product should align with the specific application. Each file contains time and lead fraction for a circular area (radius 50 km) around the MOSAiC position of the particular time stamp. The thermal infrared data from helicopter surveys are available from doi:10.1594/PANGAEA.951569.