On the Relationship Between Atmospheric Events of the Von Kármán Streets in the Robinson Crusoe Island and South Pacific Climate Variability

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ABSTRACT The Juan Fernández Archipelago (JFA), located approximately 700 km off the Chilean coast, is of great scientific importance for its unique ecosystem and numerous endemic species. Designated a World Biosphere Reserve by UNESCO in 1977, it comprises three islands: Alejandro Selkirk (AS), Robinson Crusoe (RC) and Santa Clara (SC). Using satellite images of clouds, we identified and examined Von Kármán atmospheric vortex streets (VKSs) forming dipolar structures near the islands, a phenomenon rarely studied due to observational limitations. Based on visual inspection of satellite imagery, an average of three atmospheric VKSs events are recorded per year in the RC‐SC region over the period 2000–2020. Our study aims to characterise VKSs events in RC island through satellite observations and atmospheric reanalysis, while assessing their potential impact on the surrounding ocean dynamics using sea surface temperature (SST) data. We find that low‐level wind patterns, particularly prevalent in spring and summer, play a crucial role in the formation of VKSs, along with wind speeds that do not exceed 15 m/s. These conditions can occur during specific phases of regionally significant climate modes, such as the Interdecadal Pacific Oscillation (IPO), El Niño‐Southern Oscillation (ENSO), and variability in the subtropical South Pacific anticyclone. The activity of these modes is quantified by indices such as the Pacific Interdecadal Oscillation Tripole Index (TPI), Southern Oscillation Index (SOI), and South Pacific Subtropical Anticyclone Index (iASPS), highlighting a connection between VKS occurrence and large‐scale climate variability. We also observed elevated SST in the leeward RC during spring VKS events, potentially independent of the island mass effect. Our findings provide insights into the atmospheric and oceanic interactions shaping this unique island ecosystem.

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