Climate model projections of acidification and thermal
bleaching in the world’s coral reef areas
Ruben van Hooidonk1 and Jeffrey Maynard2-4
1 – NOAA AOML, 2 – Marine Applied Research Ctr, 3 – Cornell University; 4 – CRIOBE/EPHE/CNRS
Zooxanthellae
Coral bleaching
Ocean Acidification
Graphic: www.earthonlinemedia.com
“ By
approximately 2050
sea temperatures in
tropical
oceans will
experience
anomalies every year
that will be
several times those
seen in 1998.”
-O. Hoegh-Guldberg.
Hoegh-Guldberg (1999)
Problem and opportunity:
What does our current understanding of regional and global climate
and projected climate change suggest the future holds
for coral reefs in my jurisdiction?
The objective of our collaborative work with PICCC:
To produce ensemble-based projections for all four RCP scenarios for
both thermal coral bleaching and ocean acidification and to make
projections available as maps within a publicly accessible interactive
Google Earth-based tool.
??
DHWs – the accumulation of temperature stress
NOAA Coral Reef Watch graphic
“Based on the observations used, the
associated global average and median
optimal DHW threshold are 6.1 DHWs.”
(van Hooidonk and Huber 2009)
Temporary refugia for coral reefs in a warming world
- There are few refugia from these conditions but they are
temporary
- Annual exceedance of 6 Degree Heating Weeks (DHWs) by
2050
Nature Climate Change (2013)
Effect of reducing/stabilising emissions
van Hooidonk, Maynard, and Planes (2013)
van Hooidonk, Maynard, and Planes (2013)
Opposite latitudinal gradients in projected ocean
acidification and bleaching impacts on coral reefs
Switch to higher bleaching threshold of 8 DHWs
These conditions exceed current tolerance limits of most
coral species.
Global Change Biology (2013)
(a) Timing of onset
of >8DHWs
occurring annually
(b) Ωarag at time of
(a)
(c) Abs value
reductions in Ωarag
between 2006 and
(a)
(d) Map in in (c)
expressed as a
percentage
van Hooidonk et
al. (2013)
Acidification and calcification
7
15
23
Opposite latitudinal gradients in projected ocean
acidification and bleaching impacts on coral reefs
Aragonite saturation state
Degree Heating Weeks
High Latitude Reefs
5
%
5
%
2020
2040
2060
Low Latitude Reefs
2080
2100
Latitude
increasing
Introduction page
NOAA Coral Reef Watch site visitation;
PICCC site on page for projections
visited by people from 80+ countries
http://coralreefwatch.noaa.gov/climate/projections/piccc_oa_and_bleaching/index.php
Downscaling climate model projections of coral bleaching
van Hooidonk, Maynard et al. (in revision)
Downscaling climate model projections of coral bleaching
van Hooidonk, Maynard et al. (in revision)
Downscaling climate model projections of coral bleaching
van Hooidonk, Maynard et al. (in revision)
The future for coral reefs…
??
Image: http://saveourcoralreefs.org
Thank you!
Jeffrey Maynard
E: maynardmarine@gmail.com
Ruben van Hooidonk
E: ruben.van.hooidonk@noaa.gov
Acknowledgments: Producing these projections was made possible by a research grant awarded
to our team by the Pacific Islands Climate Change Cooperative. This files contents are solely the
opinions of the authors and do not constitute statements of policy, decision or position on behalf
of NOAA or the U.S. Government.
References:
Chan, Neil, and Sean R. Connolly. "Sensitivity of coral calcification to ocean acidification: a meta‐analysis." Global change biology 19.1 (2013):
282-290.
Hoegh-Guldberg, Ove. "Climate change, coral bleaching and the future of the world's coral reefs." Marine and freshwater research 50.8 (1999):
839-866.
van Hooidonk, Ruben, et al. "Opposite latitudinal gradients in projected ocean acidification and bleaching impacts on coral reefs." Global change
biology 20.1 (2014): 103-112.
van Hooidonk, R., J. A. Maynard, and S. Planes. "Temporary refugia for coral reefs in a warming world." Nature Climate Change 3.5 (2013): 508511.