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Extreme South Pacific Phytoplankton Blooms Induced by Tropical Cyclones
  • Peter Russell,
  • Christopher Horvat
Peter Russell
University of Otago
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Christopher Horvat
Brown University

Corresponding Author:christopher_horvat@brown.edu

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Wind-driven mixing and Ekman pumping from slow-moving tropical cyclones (TCs) can bring nutrients to the euphotic zone, promoting phytoplankton blooms (TC-PBs) observable by satellite remote sensing. We examine an exceptional (z-score = 18-48) TC-PB induced by category-1 Cyclone Oma near the South Pacific island of Vanuatu in February 2019, the most extreme event in the observed satellite record of South Pacific surface Chlorophyll-a (Chl-a). Examining 15 South Pacific TC-PBs since 1997, we identify a “hover” parameter derivable from storm track data correlated with post-TC surface Chl-a (r=0.83). Using a dataset of synthetic storm tracks, we show revisit times for South Pacific TC-PBs are O(250) years, and O(1,500) years for Oma-scale TC-PBs. The episodic, extreme, but consistent nature of such events means they may imprint on sediment records. If so, we show their signature could be used to reconstruct past TC variability.