NOAA Coral Reef Watch Daily 5km Satellite Coral Bleaching Heat Stress Bleaching Alert Area Product (Version 3.1)
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Daily Global 5km Satellite Coral Bleaching Heat Stress Alert Area
(Version 3.1, released August 1, 2018)
Current Daily Variables:
Alert Area (7-day max)
DHW
HotSpot
SST
Anomaly
SST Trend
Regional Images:
Tropics
Global
East
West
Pacific
Indian
S. Atlantic
Coral Triangle
Caribbean
Florida
Hawaii
GBR
Animations (30d):
Tropics
Global
East
West
Pacific
Indian
S. Atlantic
Coral Triangle
Caribbean
Florida
Hawaii
GBR
Animations (90d):
Tropics
Global
East
West
Pacific
Indian
S. Atlantic
Coral Triangle
Caribbean
Florida
Hawaii
GBR
Year-to-date Maximum:
Alert Area
DHW
HotSpot
SST
Anomaly
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Year-to-date Minimum:
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SST
Anomaly
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Year-to-date Mean:
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SST
Anomaly
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Click on map above to zoom to small 60 x 40-degree tiles; use drop-down menu below to view larger 60 x 40-degree tiles.
Right-click outside clickable map area to save the image.
60 x 40-degree tiles (by east/west hemispheres and low/high latitudes, updated daily)
The NOAA Coral Reef Watch (CRW) daily global 5km satellite Bleaching Alert Area
(7-day maximum) product presented here outlines the areas where coral bleaching
heat stress currently reaches various levels, based on our satellite sea surface
temperature (SST) monitoring.
SST variability is often considerably higher at the much finer 5km spatial and
daily temporal resolutions, when compared with CRW's heritage
twice-weekly 50km (0.5-degree) coral bleaching heat stress monitoring products
Due to resulting day-to-day fluctuations between stress levels in highly-variable
locations, the single-day 5km Bleaching Alert Area product does not consistently
and adequately identify potentially harmful heat stress levels, especially with
regard to accumulated heat stress impacts. Rather than requiring users to examine
the single-day 5km Bleaching Alert Area product over several days, a 7-day maximum
Bleaching Alert Area composite product, updated daily, was introduced in the Version
2 product suite and is maintained here in Version 3.1. (Evolution of CRW's daily
global 5km product suites can be found
here
.)
This 7-day composite product shows the maximum stress level that a satellite pixel
has experienced during the most recent seven (7) consecutive days. Data and images
are dated on the last day of the 7-day period. Notably, it is compatible with CRW's
heritage twice-weekly global 50km Bleaching Alert Area product, as the 50km Bleaching
Alert Area is based on a half-week (3 or 4 days) composite of 50km SSTs (but with
much less SST variability due to its much coarser spatial resolution).
Even though the daily global 5km Bleaching Alert Area
(7-day maximum) composite
product is presented here, the coral bleaching heat stress levels defined in the table
below are for the daily global
single-day
5km Bleaching Alert Area product.
The heat stress level at a 5km satellite data grid, on any day, is based on CRW's
daily global 5km
Coral Bleaching HotSpot
and
Degree Heating Week (DHW)
products for that day. The
daily global 5km Bleaching Alert Area (7-day maximum) composite product therefore is
the maximum value of the seven, consecutive, daily global single-day 5km Bleaching
Alert Area values in the data grid that end on the date shown in the image.
***
UPDATE
: On December 15, 2023, NOAA Coral Reef Watch implemented a revised coral bleaching
heat stress category system for its Bleaching Alert Area product. Extreme
accumulations of coral bleaching heat stress in 2023, in multiple regions of the
world, especially in the eastern tropical Pacific Ocean and Greater Caribbean,
which were confirmed by in-water observations, necessitated the introduction of
additional Bleaching Alert Levels. This development is a refinement of the
original system that only used Bleaching Alert Levels 1 and 2. The new Alert
Levels 3-5 provide important, added detail, for when the magnitude of extreme
heat stress exceeds the threshold of Alert Level 2 conditions.
For managers: we
understand that coral bleaching response plans, action plans, and restoration
plans around the world rely on NOAA Coral Reef Watch's Bleaching Alert Levels,
to assist with planning and implementation of work by your in-water monitoring
and management networks. Any actions you would have taken at Bleaching Alert
Level 2, previously, still apply. We recognize, however, that discussions may
need to occur now, regarding appropriate actions for your networks, when the
extreme Bleaching Alert Levels 3-5 are predicted.
***
Stress Level
Definition
Potential Bleaching and Mortality
No Stress
HotSpot <= 0
No Bleaching
Bleaching Watch
0 < HotSpot < 1
Bleaching Warning
1 <= HotSpot and 0 < DHW < 4
Risk of Possible Bleaching
Bleaching Alert Level 1
1 <= HotSpot and 4 <= DHW < 8
Risk of Reef-Wide Bleaching
Bleaching Alert Level 2
1 <= HotSpot and 8 <= DHW < 12
Risk of Reef-Wide Bleaching with Mortality of Heat-Sensitive Corals
Bleaching Alert Level 3
1 <= HotSpot and 12 <= DHW < 16
Risk of Multi-Species Mortality
Bleaching Alert Level 4
1 <= HotSpot and 16 <= DHW < 20
Risk of Severe, Multi-Species Mortality (> 50% of corals)
Bleaching Alert Level 5
1 <= HotSpot and 20 <= DHW
Risk of Near Complete Mortality (> 80% of corals)
Note that in the Bleaching Alert Area (7-Day Maximum) composite product, locations
with a status of No Stress or Bleaching Watch, for a 7-day time period, may still
have been exposed to recent heat stress, including in the days immediately preceding
the 7-day period under evaluation. The reason is that the Bleaching Alert Area
(7-Day Maximum) composite product classifies the heat stress condition for a specified
7-day period only -- and that heat stress condition (level) is determined by the
seven, most-recent daily value pairs
of CRW's v3.1 daily global 5km
Coral Bleaching HotSpot
and
DHW
So if, during the specified 7-day period being evaluated, the seven Coral Bleaching
HotSpot values (within the seven daily pairs of Coral Bleaching HotSpot/DHW) were all
zero, this would indicate the absence of active heat stress. For that reason, a No
Stress level would be assigned, and any heat stress experienced during the 11 weeks
preceding the 7-day period would not be examined, as corals should be in a recovery
state. If, during the specified 7-day period being evaluated, any of the seven Coral
Bleaching HotSpot values (within the seven daily Coral Bleaching HotSpot/DHW pairs)
was greater than zero, but below the bleaching threshold for accumulating DHWs, this
would indicate that there is currently insufficient heat stress to actively cause or
worsen visible bleaching. For this reason, none of the seven daily DHW values (within
the seven daily Coral Bleaching HotSpot/DHW pairs) would be examined; a Bleaching Watch
level would be assigned; and any recently-accumulated DHWs greater than zero, that
occurred within the 11 weeks preceding the 7-day period, would not be used to determine
the current heat stress level. With that said, if on any future day, the Coral Bleaching
HotSpots resurrected, and were greater than the threshold for accumulating DHWs, then
recent heat stress exposure during the entire past 12 weeks (84 days) would be evaluated.
This means all daily Coral Bleaching HotSpot values that exceeded the bleaching threshold
during the past 12 weeks would be accumulated to calculate the DHWs and determine the
Bleaching Alert Area (7-Day Maximum) composite product heat stress level. As a result, a
future heat stress level could jump from No Stress or Bleaching Watch to any of the
higher stress levels, as the calculation would again be dependent on recent heat stress
exposure during the entire last 12 weeks. Please refer to CRW's
daily global 5km DHW
product for more information.
This product is updated each afternoon at about 13:30 U.S. Eastern Time.
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