Abstract
The increasing frequency of coral bleaching events, fueled by ocean warming, is driving development of management strategies aimed at minimizing impact and maximizing reef recovery. Accurate early bleaching forecasts could provide the lead time critical for effective planning and intervention, yet existing predictors rely on near-term thermal stress detection with limited accuracy. Here we show that 10 of the 11 bleaching events recorded on the southern Caribbean island of Curaçao since 1990 occurred in years when three large-scale Pacific and Atlantic climate modes aligned, compounding the long-term warming trend to drive reef temperatures above bleaching thresholds. Using climate mode indices available months prior to peak bleaching, we develop the Bleaching Event Early Predictor, a mode-based risk assessment tool that provides 5–6 months of lead time for management action. Although developed for Curaçao, this framework is likely adaptable across reef systems, offering a pathway towards seasonal prediction of bleaching risk.
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Data availability
All coral core stress band data generated in this study are presented in the Supplementary Materials and can be accessed on Zenodo96. Initial viewing of coral core CT scans was performed using Horos, a free and open-source code medical image viewing software program distributed under the LGPL license by the Horos Project and can be accessed at https://horosproject.org/. The NOAA CoralTemp 5 km product15 can be downloaded from NESDIS (https://www.star.nesdis.noaa.gov/pub/socd/mecb/crw/data/5km/v3.1_op/nc/v1.0/daily/sst/, accessed on 5/20/2024) and ERA5 wind data97 can be downloaded from the Copernicus Climate Data Store (https://doi.org/10.24381/cds.adbb2d47, accessed on 12/31/2022). The NAO and ONI indices can be downloaded from NOAA’s National Centers for Environmental Prediction (https://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php and https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table, both accessed on 9/25/2024). HadISST sea surface temperature data98 used to compute AMV and AMVnd can be downloaded from the UK Met Office Hadley Centre (https://www.metoffice.gov.uk/hadobs/hadisst/data/download.html, accessed 9/25/2024).
Code availability
Analysis of CT scan density anomalies was performed using CoralCTv2mini (https://doi.org/10.5281/zenodo.18929236). The ‘amo’ function for computing AMV can be found within the Climate Data Toolbox (https://www.chadagreene.com/CDT/CDT_Contents.html)94. All maps were created using the M_Map mapping package (http://www.eoas.ubc.ca/~rich/map.html).
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Acknowledgements
We thank Gonzalo Perez-Rosales, Evii Tong, Mark Vermeij of CARMABI and Kevin Philbert and Roland De Cuba of the Curaçao Marine Park for their assistance in the 2023 fieldwork operations and permitting process. We thank Mitchell Starr and Grace Nielsen for assistance in CT scanning as well as Nathaniel Mollica for help with writing the CT analysis code and for discussion. This work was supported by a National Science Foundation Graduate Research Fellowship and Woods Hole Oceanographic Institution Ocean Ventures Fund awarded to M.G., National Science Foundation awards #2049567, 2230734, and 2137882 awarded to A.L.C., funding from Alta Futures, Grossman Family Foundation, and Arthur Vining Davis Foundation awarded to A.L.C., the James E. and Barbara V. Moltz Fellowship for Climate-Related Research at WHOI awarded to C.C.U., and the Woods Hole Oceanographic Institution Investment in Science Program awarded to A.L.C., D.W.O., and C.C.U.
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M.G. and A.L.C. conceived this study. M.G. developed the methodology, completed all analyses, created all figures, and wrote the original draft. All authors contributed to the interpretation of the results and editing of the manuscript (M.G., A.L.C., D.W.O., and C.C.U.).
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Galochkina, M., Cohen, A.L., Oppo, D.W. et al. Climate modes can be leveraged to forecast coral bleaching months in advance. Commun Earth Environ (2026). https://doi.org/10.1038/s43247-026-03438-7
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DOI: https://doi.org/10.1038/s43247-026-03438-7
