For more than 20 years, NOAA Coral Reef Watch (CRW) has been the world’s leader in observing, predicting, and communicating changes in the coral reef environment to a diverse, global user community. In mid-December 2021, CRW’s daily global 5km-resolution satellite coral bleaching heat stress products detected a significant build-up of oceanic heat stress on the Great Barrier Reef (GBR), Australia. This signified the GBR was starting its 2021-2022 summer season with a much earlier onset of accumulated heat stress than ever recorded before. At the same time, CRW’s modeled Four-Month Coral Bleaching Heat Stress Outlook indicated the significant heat stress would continue, leading to a potential mass coral bleaching event on the GBR (following on the heels of confirmed mass bleaching events in 2016, 2017, and 2020).
Understanding the potential significance of the developing bleaching-level heat stress, CRW conducted an historical analysis of thermal conditions on the GBR, from 1985 to the present. Even with the La Niña (which usually provides reefs in the region with relief from heat stress), CRW identified unprecedented elevation in background temperatures. For 87% of the 5km coral reef pixels on the GBR, the minimum sea surface temperature (SST), between November 16 and December 14, 2021, was greater than the maximum SST ever experienced at those locations within that same 29-day period from 1985-2020. CRW quickly communicated this critical information to its partners and users in Australia, and published its findings on February 1, 2022 in the F1000Research paper, “Unprecedented early-summer heat stress and forecast of coral bleaching on the Great Barrier Reef, 2021-2022”, led by ESSIC/CISESS subawardee, Dr. Blake Spady.
The Great Barrier Reef Marine Park Authority (GBRMPA), in coordination with the Australian Institute of Marine Science (AIMS) and others, was closely monitoring CRW’s satellite- and model-based products for changes in reef environmental conditions. Following CRW’s alerts of widespread, significant bleaching-level heat stress, after an unprecedented month-long cooling period (due to regional cyclonic activity), GBRMPA completed intensive aerial surveys across the reef tract last week. On March 25, 2022, GBRMPA officially confirmed a mass coral bleaching event was underway (Figure 1). It is the sixth mass bleaching event on record, the fourth, confirmed mass bleaching event since 2016, and the first ever mass bleaching during a La Niña on the GBR.
Figure 1. The Great Barrier Reef Marine Park Authority (GBRMPA) confirms a reef-wide mass bleaching event on the GBR during its weekly Reef Health update of 25 March 2022, hosted by GBRMPA’s Chief Scientist, Dr. David Wachenfeld, and Coral Biologist, Dr. Neal Cantin, from the Australian Institute of Marine Science (AIMS).
The NOAA CRW program is an initiative supported by the Earth System Science Interdisciplinary Center (ESSIC)-administered Cooperative Institute for Satellite Earth System Studies (CISESS). ESSIC/CISESS Scientists include Associate Research Scientist Dr. Gang Liu; Senior Faculty Specialist Jacqueline De La Cour; and Faculty Specialist Erick Geiger. The team also includes ESSIC/CISESS subawardees, Drs. William Skirving and Blake Spady, at ReefSense in Townsville, Australia.
Click here to follow CRW’s modeled Four-Month Coral Bleaching Outlook, and here to access the daily global 5km satellite products, to monitor the developing heat stress on the GBR and elsewhere around the world.