arXiv subjects

Giulio Passerotti

Publications and source records attributed to Giulio Passerotti.

3 recordsLinked to original sources

arXiv2025

Fine-Scale Heterogeneity of Snow Cover in the Antarctic Marginal Ice Zone

Snow cover on Antarctic sea ice is highly heterogeneous, yet climate models have historically simplified it to a uniform layer in winter and bare ice in summer, introducing uncertainty in simulated surface energy fluxes. Here, using shipborne, high-resolution, close-range imagery of the sea ice surface, visual observations, and concurrent atmospheric data from five expeditions across the Antarctic marginal ice zone (2019-2024), we show that fine-scale (sub-grid) snow cover heterogeneity persists across all seasons, is largely independent of ice concentration, and is governed by ice morphology and regional accumulation history. When the heterogeneity is incorporated into flux calculations, it introduces systematic biases in surface energy fluxes relative to uniform-surface assumptions. These findings, based on observations from two Southern Ocean sectors, suggest that the inclusion of sub-grid snow distribution should be considered for simulating Antarctic sea ice evolution and its broader polar climate feedback.

physics.ao-ph↗

arXiv2024

Sea ice floe segmentation in close-range optical imagery using active contour and foundation models

The size of sea ice floes in the marginal ice zone (MIZ) is a key factor influencing ice coverage, albedo, wave propagation, and ocean--atmosphere energy exchanges. Floe size can be observed by processing visual-range imagery from ships, aircraft, or satellites. However, autonomously capturing floe boundaries remains challenging, particularly due to sea ice heterogeneity, which impairs boundary definition and reduces image clarity. This study evaluates the accuracy of sea ice floe segmentation using the gradient vector flow (GVF) active contour method, the deep learning-based Segment Anything Model (SAM), and a hybrid approach combining GVF and SAM. Methods are evaluated on a representative subset of a large dataset of close-range, high-resolution imagery collected from cameras aboard an icebreaker during an Antarctic winter expedition. Spanning a wide range of ice conditions and image clarity in the MIZ, the subset provides a rigorous segmentation test bed. Performance is assessed in terms of floe detection accuracy, size distribution, and ice concentration, with results compared against a manually segmented benchmark. Results indicate SAM, in prompt-driven mode, offers the best balance between accuracy and computational efficiency. Its strong performance in estimating sea ice concentration and detecting floes, while maintaining close agreement with benchmark floe size distributions, makes it suitable for real-time applications and scalable analyses of large imagery datasets. Compared with SAM, the combined SAM-GVF method provides more accurate floe boundary delineation, although at much higher computational cost, and is therefore better suited for analyses requiring precise floe shapes.

physics.ao-ph↗

arXiv2022

Interactions between irregular wave fields and sea ice: A physical model for wave attenuation and ice breakup in an ice tank

Irregular, unidirectional surface water waves incident on model ice in an ice tank are used as a physical model of ocean surface wave interactions with sea ice. Results are given for an experiment consisting of three tests, starting with a continuous ice cover and in which the incident wave steepness increases between tests. The incident waves range from causing no breakup of the ice cover to breakup of the full length of ice cover. Temporal evolution of the ice edge, breaking front and mean floe sizes are reported. Floe size distributions in the different tests are analysed. The evolution of the wave spectrum with distance into the ice-covered water is analysed in terms of changes of energy content, mean wave period and spectral bandwidth relative to their incident counterparts, and pronounced differences are found between the tests. Further, an empirical attenuation coefficient is derived from the measurements and shown to have a power-law dependence on frequency comparable to that found in field measurements. Links between wave properties and ice breakup are discussed.

physics.ao-ph↗