Stress Frequency metrics: Coral reef sites that have experienced fewer heat stress events may have natural protection (e.g., strong mixing, upwelling) from exposure to conditions conducive to coral bleaching. However, corals at those sites may have an enhanced sensitivity to heat stress, resulting in higher impacts during a stress event. Alternatively, at sites regularly exposed to heat stress, surviving corals can have a reduced sensitivity to heat stress, and thus be less impacted (potentially) by subsequent stress events. Stress events are defined for 1985-2023 by applying Coral Reef Watch's Degree Heating Week (DHW) methodology at coral reef-containing and adjacent satellite pixel locations worldwide, using the Version 3.1 daily global 5km CoralTemp satellite sea surface temperature (SST) data product. The three thresholds for heat stress events displayed here correspond to occurrence (DHW>0); reef-wide coral bleaching (DHW≥4); and severe, reef-wide coral bleaching with coral mortality (DHW≥8).

Number of Heat Stress Events [range: 2-57 events for DHW>0] and Average Time between Heat Stress Events [0.7-22.9 years for DHW>0]: These metrics present the number of heat stress events (at the corresponding DHW thresholds of DHW>0, DHW≥4, and DHW≥8) that occurred during 1985-2023, and the average time period between those events, respectively. NOTE: the ranges of values provided in the brackets above are for the event threshold of DHW>0 only, to encompass all events globally, where accumulated heat stress could have led to a bleaching event. Calculation of the average time between events, at each data pixel, requires at least one event, with at least one definable time period. If a pixel has only one event, it spans from the date of that event to the end date of the dataset. The "n/a" color for the average time between events represents locations with zero events and, therefore, no definable period between.