Coral Bleaching Heat Stress Analysis and
Seasonal Guidance through June 2021
(Released March 3, 2021)
NOAA Coral Reef Watch's (CRW) near real-time satellite monitoring shows the sea surface temperature (SST) as being predominantly below-average along the equator in the eastern and central equatorial Pacific Ocean; below-average in the southeast Pacific and northeast Pacific between 0 °N and 20 °N latitude; and above-average throughout the remainder of the ocean basin (Figure 1). SST anomalies remained 1-2 °C above normal for most of December 2020 around Hawaii, Fiji, American Samoa, and Guam. In January and February 2021, temperatures were average to slightly below-average for Fiji and American Samoa, but remained above average around Hawaii and Guam. The El Niño-Southern Oscillation (ENSO) Alert System status (as of February 11, 2021) remains at La Niña Advisory. A majority of the models predict a transition to ENSO-neutral conditions during Northern Hemisphere spring 2021 (about 60% chance).
Figure 1. NOAA Coral Reef Watch's Satellite Sea Surface Temperature (SST) Anomaly product for the Pacific region.
Coral Bleaching HotSpots reached about 1 °C around Fiji in January but remained below 1 °C in all other locations east of Vanuatu (Figure 2). From January to February 2021, heat stress around Fiji decreased from Bleaching Warning to Bleaching Watch; it remains at Bleaching Watch. Since December 2020, American Samoa has been at Bleaching Watch, with minimal chance of coral bleaching. Hawaii and Guam are at no threat of coral bleaching at this time (Figure 3). The highest bleaching alerts are concentrated from east of the Great Barrier Reef, Australia to Vanuatu, between 5 °S and 25 °S latitude.
Figure 2. NOAA Coral Reef Watch's Satellite Coral Bleaching HotSpot product for the Pacific region.
Figure 3. NOAA Coral Reef Watch's Satellite Bleaching Alert Area (7-day maximum) product for the Pacific region.
CRW's most recent Four-Month Coral Bleaching Outlook (Figure 4) projects heat stress will elevate to Bleaching Alert Level 1 around American Samoa in May 2021 and around the Gilbert Islands and Phoenix Islands, Kiribati in June 2021.
Figure 4. NOAA Coral Reef Watch's Four-Month Coral Bleaching Outlook of March 2, 2021, for the period March-June 2021 for the Pacific region.
***NOTE: This report incorporates NOAA Coral Reef Watch's Version 3.1 (or v3.1) daily global 5km satellite-based coral bleaching heat stress products and v5 Four-Month Coral Bleaching Heat Stress Outlook.***
To monitor the intensity and location of bleaching heat stress in your coral reef region of interest, please follow NOAA Coral Reef Watch's satellite monitoring and outlooks closely in the coming weeks: https://coralreefwatch.noaa.gov/product/5km/index.php and https://coralreefwatch.noaa.gov/satellite/bleachingoutlook_cfs/outlook_cfs.php.
CRW's current satellite and modeled products can be found at:
CRW's Four-Month Coral Bleaching Heat Stress Outlooks can be found at:
CRW's 5km satellite Regional Virtual Stations can be found at:
Sign up for automated bleaching alert emails for CRW's 5km Regional Virtual Stations at:
Please report bleaching events (or non-events) at:
The content posted on this web page solely represents the opinions of the authors and does not constitute a statement of policy, decision, or position on behalf of NOAA or the US Government.
The appearance of external links on this World Wide Web site does not constitute endorsement by the Department of Commerce/National Oceanic and Atmospheric Administration of external Web sites or the information, products or services contained therein. For other than authorized activities, the Department of Commerce/NOAA does not exercise any editorial control over the information you may find at these locations. These links are provided consistent with the stated purpose of this Department of Commerce/NOAA Web site.