Observations show ocean temperatures are rising due to climate change, resulting in a fivefold increase in the incidence of regional-scale coral bleaching events since the 1980s; analyses based on global climate models forecast bleaching will become an annual event for most of the world's coral reefs within 30-50 yr. Internal waves at tidal frequencies can regularly flush reefs with cooler waters, buffering the thermal stress from rising sea-surface temperatures. Here we present the first global maps of the effects these processes have on bleaching projections for three IPCC-AR5 emissions scenarios. Incorporating semidiurnal temperature fluctuations into the projected water temperatures at depth creates a delay in the timing of annual severe bleaching ≥ 10 yr (≥ 20 yr) for 38% (9%), 15% (1%), and 1% (0%) of coral reef sites for the low, moderate, and high emission scenarios, respectively; regional averages can reach twice as high. These cooling effects are greatest later in twenty-first century for the moderate emission scenarios, and around the middle twenty-first century for the highest emission scenario. Our results demonstrate how these effects could delay bleaching for corals, providing thermal refugia. Identification of such areas could be a factor for the selection of coral reef marine protected areas.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was funded by the U.S. Geological Survey’s (USGS) Coastal and Marine Hazards and Resources Program and NOAA’s Coral Reef Conservation Program in support of the goals of the U.S. Coral Reef Task Force to protect and preserve coral reefs. We are grateful to Pat Colin for the Coral Reef Research Foundation datasets. The data used to generate the results can be found at: https://doi.org/10.5066/P9PFGYMX. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.