Coral bleaching
Thermal stress indices
Coral Reefs - sites: 1871 to date
During 1997-1998 mass coral bleaching was observed on many of
the world’s coral reefs (See also "Status of the World’s Coral
Reefs:" 1998, 2000 & 2002).
There has also been increased number of reports of mass coral
bleaching events since the mid-1970s (e.g. Glynn, 1996)
coinciding with an increased rate of warming of global
temperatures (e.g. IPCC 2001) and growing concern about the
potential impacts of global warming due to the enhanced
Greenhouse effect on the frequency of such events (e.g. HoeghGuldberg, 1999). These large-scale coral bleaching events
appear primarily due to unusually warm sea surface
temperatures (SSTs) during the warm water season at affected
coral reef sites. Lough (2000) published indices, for the period
1903-1999, of thermal stress at 47 global coral reef sites that
had bleached during 1997-98.
These indices showed that the frequency of warm season
extremes had increased since the 1970s and that the degree of
thermal stress during 1997-98 was the highest on record.
These thermal stress indices have recently been extended back
to 1871 using the UK Hadley Centre global monthly SST
compilation up to 1999 and updated to the present using NOAA
NCEP EMC CMB Global Reyn-Smith OIv2 blended satellite and
observations data set.
UK Hadley Centre
OIv2 blended satellite and observations data set
The "thermal stress" or omonth indices presented here are
determined for each year and site and combine both the
magnitude and duration of warm season SST anomalies. The
base period for calculating SST anomalies was 1982-1999,
common to the two data sets.
Thermal stress indices
The thermal stress indices cover the period 1871 through to
current date and will be up-dated at regular intervals.
Figure 1
Figure 2
Figure 3
Figure 4
Average annual maximum SSTs were extracted and
anomalies above this mean summed for the months
each year this average was exceeded at each of 50
sites.
Annual thermal stress indices averaged over all 50
sites.
Annual thermal stress indices averaged from 18 sites
in the Indian Ocean and Middle East.
Annual thermal stress indices averaged from 9 sites
in southeast Asia.
Annual thermal stress indices averaged from 11 sites
in the Pacific Ocean.
Annual thermal stress indices averaged from 12 sites
in the Caribbean and Atlantic Ocean.
Figure 5
Figure 6
References




Glynn, PW (1996) Coral reef bleaching: facts,
hypotheses and implications. Global Change Biology 2:
495-509.
Hoegh-Guldberg, O (1999) Climate change, coral
bleaching and the future of the world’s coral reefs.
Marine and Freshwater Research 50: 839-866
IPCC (2001) Climate Change 2001: The Scientific Basis,
Cambridge University Press, 944pp (see also
http://www.ipcc.ch/)
Lough, JM (2000) 1997-98: Unprecedented thermal
stress to coral reefs? Geophysical Research Letters 27:
3901-3904
Contact
Dr. Janice Lough
Email: j.lough@aims.gov.au
See also:
Coral bleaching index - current and archival information covering the past several
years
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Australian Institute of
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