SAR-based monitoring of shipping reorganization under a maritime chokepoint disruption: Evidence from the Strait of Hormuz crisis

As one of the most crucial energy transportation routes globally, the Strait of Hormuz accounts for a significant portion of the global seaborne oil trade. Its operational status has a decisive impact on the stability of the global shipping network. Any disruption to its passage would trigger a reconfiguration of the shipping network. Since late February 2026, conflicts have led to a sharp decrease in the daily number of ships passing through the strait, from approximately 130 to fewer than 10, forcing a significant number of ships to reroute around the Cape of Good Hope, posing significant challenges to coastal and ocean management. In this study, we utilized Sentinel-1 Synthetic Aperture Radar (SAR) data to conduct time-series monitoring of ships in three strategic maritime areas: the Persian Gulf, the Red Sea-Gulf of Aden, and the Cape of Good Hope, as well as the Strait of Hormuz, which served as the event center region. We extracted ship targets based on backscatter characteristics and conducted a comparative analysis between the pre-event period (February 22nd to 28th) and the post-event period (February 28th to March 27th). The results indicate that during the closure, ship density near Port of Jebel Ali increased continuously, peaking at over 330 ships on 9 March. In contrast, waters near Port of Bandar Abbas exhibited sustained congestion of approximately 270 ships until 9 March, followed by a reduction of about 40 ships by 14 March. In the Red Sea, overall ship numbers slightly decreased, whereas traffic near Port of Assab increased, reaching a peak of over 70 ships on 19 March. Around 14 March, most ships chose to bypass the Cape of Good Hope area, resulting in an approximate 30% increase in regional traffic, with ship numbers near Port of Cape Town nearly doubling relative to pre-rerouting conditions. These findings demonstrate that SAR enables independent and robust monitoring of maritime dynamics without reliance on cooperative ship signals. From a coastal management perspective, the study highlights critical challenges associated with abrupt shipping pattern shifts, including emergency port scheduling, inter-regional traffic coordination, and ecological pressures, thereby providing remote sensing–based support for decision-making under sudden maritime disruptions.