11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 25: Predicting Reef Futures in the Context of Climate Change
25-1
Is 500 Ppm Co2 And 2°c Of Warming The 'tipping Point' For Coral Reefs? If So,
How Should We Respond?
Ove HOEGH-GULDBERG* 1
1 Centre for Marine Studies, University of Queensland, St Lucia, Australia
The burning of fossil fuels is driving a rapid increase in the concentration of CO2 in the
atmosphere which is expected to exceed 500 ppm in the earth’s atmosphere within 50
years. At this point, tropical sea temperatures will be 2°C warmer than 150 years ago and
tropical carbonate ion concentrations will fall below 200 µmol kg -1 . These conditions
differ markedly from those seen over the past 420,000 years during which time most
extant species and communities evolved. Most importantly, the current rate of change in
sea temperature and atmospheric CO2 is 70 and 1,000 times faster, respectively, than the
highest rates of change seen in the past 420,000 years. This is outstripping biological
responses (adaptation, range migration) and is driving major changes in the distribution
and abundance of tropical marine organisms. This paper will discuss scenarios
associated with the future of coral reefs with the aim of visualizing the challenges that
coral reef managers will face over the next few decades as we approach 500 ppm. The
weight of evidence suggests that corals will be rare on tropical reefs which will enter a
state of net erosion under atmospheric CO2 concentration of 500 ppm or more. As a
result, coral reefs are expected to be less diverse and reef frameworks to start to crumble
and deteriorate. How can managers respond to these changes? Are there responses that
managers should be taking today in preparation for changes projected a few decades from
now? Should we contemplate moving vulnerable species or enriching the genetic
diversity of species growing at a particular location? These issues will be discussed at
the outset of this mini-symposium which anticipates a lively discussion around what is
clearly one of the most important issues facing coral reef scientists and managers.
25-2
Implications For Our Coral Reefs in A Changing Climate Over The Next Few
Decades – Hints From The Past 22 Years
Alan E. STRONG* 1 , Gang LIU 2 , C. Mark EAKIN 1 , Tyler R. L. CHRISTENSEN 2 ,
Dwight K. GLEDHILL 2 , Scott F. HERON 1 , Jessica A. MORGAN 2 , William J.
SKIRVING 1
1 NOAA Coral Reef Watch, Silver Spring, MD, 2 IMSG at NOAA Coral Reef Watch,
Silver Spring, MD
The NOAA/NASA Pathfinder sea surface temperature (SST) data from 1985 to 2006 are
examined for variability and trends on both sides of the recent 1998 Pacific Decadal
Oscillation (PDO) reversal for implications on tropical ecosystems. These twenty-two
years of satellite observations reveal some noteworthy shifts that have quite different
implications for each major ocean basin. In addition, the data reveal expected increasing
SST trends toward higher latitudes, especially in the northern hemisphere, confirming the
Intergovernmental Panel on Climate Change (IPCC) projections. Although several
regions throughout the tropics have experienced decreasing SSTs over the 22-year
timeframe, significantly more regions are showing rising trends. Most notable and
worrisome is an obvious shift after the recent PDO reversal from cooling to warming in
some specific tropical waters. More promising regions, also identified from our results,
are presently experiencing cooling trends and thus decreasing pressure from thermal
stress. What will be instructive for the future of our precious coral reef ecosystems is
whether the dramatic regional shift in trends since the recent 1998 PDO reversal
continues to persist into the second decade of the 21 st Century or evolves into a signal of
a changing climate.
25-3
The Elephant In The Reef: Committed Warming And Coral Bleaching
Simon DONNER* 1
1 Geography, University of British Columbia, Vancouver, BC, Canada
An increase in episodes of mass coral bleaching around the world in recent decades have been
attributed to more frequent periods of anomalously warm ocean temperatures. Over the past
fifteen years, a number of modeling studies have predicted that, left unchecked, human-induced
climate change will further increase the frequency and intensity of these thermal stress events
and threaten the survival of most of the world’s coral reef ecosystems. As now near the end of
the first decade of the 21st century, the questions need to change. Is the future happening now?
How much of this projected climate warming can be avoided?
In this presentation, I use analysis of the 2005 coral bleaching event in the Caribbean to discuss
the role of human-induced climate change in recent mass coral bleaching events and the effect
of “committed” warming on the likelihood of future mass bleaching events. Simulations of
background climate variability with the GFDL global climate models suggest that
anthropogenic warming may have increased the probability of the 2005 coral bleaching events
by an order of magnitude. The thermal stress that cause mass coral bleaching in the eastern
Caribbean is expected to become a biannual event in 20-30 years regardless of the emissions
scenario, due to the inertia in the climate system and the world economy. Thermal adaptation by
corals and their symbionts could delay this forecast until the latter half of the century, possibly
enabling time to reduce greenhouse gas emissions and change the climate forecast. Taken
together, these results suggest that protecting coral reefs from climate change will require
managing local stresses, to increase reef resilience to inevitable future warming, and immediate
action to reduce greenhouse gas emissions.
25-4
Climate-Scale Influences On The Development Of Coral Bleaching Conditions in The
Great Barrier Reef
Scarla WEEKS* 1 , Ana REDONDO-RODRIGUES 1 , Andrew BAKUN 2
1 University of Queensland, Brisbane, Australia, 2 Pew Institute for Ocean Sciences, University
of Miami, Miami, FL
A suite of available time series indicators of climatic and large-scale oceanographic properties
and processes were evaluated with respect to providing (1) an appropriately representative
climatological background for studying the factors leading to coral bleaching events, (2) a timeseries
record long enough to contain multiple independent realisations sufficient for valid
hypothesis tests, and (3) a consistent baseline for normalising higher spatial and temporal
resolution data obtained from more recent satellite sensors. These indicator series included
NOAA OI SST (1° res., 1982-2007), the NCEP series (barometric pressure, wind, water vapor,
air temperature, 1948-2007, 2.5° res.), and the NASA “Photosynthetically Active Radiation”
product (9km res., 1997-2007). The study focused on three recent coral bleaching events in the
GBR, the 1997-1998 “El Niño”-associated event, the 2005-2006 mild “La Niña”-associated
event, and the most severe of the three, the 2001-2002 “ENSO-neutral” event.
Preliminary findings include: La Niñas (2005-06 in particular) are characterized by high
regional-scale SST, while El Niños (1997-98 in particular) are typified by high solar radiation
(PAR) incident on the sea surface. Accordingly, bleaching in the GBR may occur in either
ENSO phase. The intense 2001-2002 event featured unusually high levels of both SST and
PAR. The “linking factor” in all three major bleaching events was anomalously low wind
mixing of the near-surface water column. The actual spatial variability of severe bleaching
tends to be on scales smaller than resolved by the available climatic series, and seems to be
governed by meso-scale and sub-meso-scale ocean flow. Examples are illustrated with 1-km
MODIS satellite imagery.
An emerging consensus among climate models suggests that the Pacific trade wind circulation
may slow and the Pacific system become chronically more El Niño-like. Thus besides direct
greenhouse heating, there are additional El Niño-related possibilities of enhancement of PAR
and reduction of near-surface wind mixing.
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