Do Clouds Save the Great Barrier Reef? Satellite Imagery Elucidates the Cloud-SST Relationship at the Local Scale

Evidence of global climate change and rising sea surface temperatures (SSTs) is now well documented in the scientific literature. With corals already living close to their thermal maxima, increases in SSTs are of great concern for the survival of coral reefs. Cloud feedback processes may have the potential to constrain SSTs, serving to enforce an “ocean thermostat” and promoting the survival of coral reefs. In this study, it was hypothesized that cloud cover can affect summer SSTs in the tropics. Detailed direct and lagged relationships between cloud cover and SST across the central Great Barrier Reef (GBR) shelf were investigated using data from satellite imagery and in situ temperature and light loggers during two relatively hot summers (2005 and 2006) and two relatively cool summers (2007 and 2008). Across all study summers and shelf positions, SSTs exhibited distinct drops during periods of high cloud cover, and conversely, SST increases during periods of low cloud cover, with a three-day temporal lag between a change in cloud cover and a subsequent change in SST. Cloud cover alone was responsible for up to 32.1% of the variation in SSTs three days later. The relationship was strongest in both El Niño (2005) and La Niña (2008) study summers and at the inner-shelf position in those summers. SST effects on subsequent cloud cover were weaker and more variable among study summers, with rising SSTs explaining up to 21.6% of the increase in cloud cover three days later. This work quantifies the often observed cloud cooling effect on coral reefs. It highlights the importance of incorporating local-scale processes into bleaching forecasting models, and encourages the use of remote sensing imagery to value-add to coral bleaching field studies and to more accurately predict risks to coral reefs.

[1]  M. Schleyer,et al.  Coral bleaching on high-latitude marginal reefs at Sodwana Bay, South Africa. , 2002, Marine pollution bulletin.

[2]  R. Barry,et al.  Atmosphere, Weather and Climate , 1968 .

[3]  Kenneth R. N. Anthony,et al.  ReefTemp: An interactive monitoring system for coral bleaching using high‐resolution SST and improved stress predictors , 2008 .

[4]  S. Warren,et al.  Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate , 1987, Nature.

[5]  T. McClanahan,et al.  Predictability of coral bleaching from synoptic satellite and in situ temperature observations , 2007, Coral Reefs.

[6]  K. Mann,et al.  Dynamics of Marine Ecosystems: Mann/Dynamics of Marine Ecosystems , 2005 .

[7]  J. Lough.  Sea surface temperatures on the Great Barrier Reef : a contribution to the study of coral bleaching , 1998 .

[8]  L. Morawska,et al.  New particle formation and growth at a remote, sub-tropical coastal location , 2009 .

[9]  Janice M. Lough,et al.  Climate change and the Great Barrier Reef: A vulnerability assessment , 2007 .

[10]  V. Ramanathan,et al.  Thermodynamic regulation of ocean warming by cirrus clouds deduced from observations of the 1987 El Niño , 1991, Nature.

[11]  C. Wilkinson,et al.  Patterns in the distribution of sponge populations across the central Great Barrier Reef , 2004, Coral Reefs.

[12]  C. Steinberg.  Chapter 3 Impacts of climate change on the physical oceanography of the Great Barrier Reef , 2007 .

[13]  Gokhan Danabasoglu,et al.  Potential role of the ocean thermostat in determining regional differences in coral reef bleaching events , 2008 .

[14]  R. Simó,et al.  Re-visiting the CLAW hypothesis , 2007 .

[15]  Z. Dinesen.  Patterns in the distribution of soft corals across the central Great Barrier Reef , 2004, Coral Reefs.

[16]  G. Jones,et al.  Atmospheric dimethysulphide production from corals in the Great Barrier Reef and links to solar radiation, climate and coral bleaching , 2012, Biogeochemistry.

[17]  Chapter 2: Climate and climate change on the Great Barrier Reef , 2007 .

[18]  Olof Lindén,et al.  Ecological and socioeconomic impacts of 1998 coral mortality in the Indian Ocean: an ENSO impact and a warning of future change? , 1999 .

[19]  Sergio M. Vallina,et al.  Strong Relationship Between DMS and the Solar Radiation Dose over the Global Surface Ocean , 2007, Science.

[20]  Mark E. Warner,et al.  Coral bleaching: interpretation of thermal tolerance limits and thermal thresholds in tropical corals , 2001, Coral Reefs.

[21]  G. Jones,et al.  DMSP in Corals and Benthic Algae from the Great Barrier Reef , 2002 .

[22]  J. Lough.  Sea surface temperatures along the Great Barrier Reef: a contribution to the study of coral bleaching. Great Barrier Reef Marine Park Authority Research Report no. 57 , 1999 .

[23]  A. J. Underwood,et al.  Environmental decision-making and the precautionary principle: what does this principle mean in environmental sampling practice? , 1997 .

[24]  R. Berkelmans,et al.  Coral Bleaching in Space and Time , 2009 .

[25]  G. Stephens.  Cloud Feedbacks in the Climate System: A Critical Review , 2005 .

[26]  S. Bony,et al.  Sea Surface Temperature and Large-Scale Circulation Influences on Tropical Greenhouse Effect and Cloud Radiative Forcing , 1997 .

[27]  E. Deschaseaux,et al.  Dimethylsulfide, climate and coral reef ecosystems , 2012 .

[28]  M. Lesser,et al.  UV‐absorbing compounds in the coral Pocillopora damicornis: Interactive effects of UV radiation, photosynthetically active radiation, and water flow , 1997 .

[29]  Serge Andréfouët,et al.  Cloudy weather may have saved Society Island reef corals during the 1998 ENSO event , 2001 .

[30]  Andrew S. Brierley,et al.  Impacts of Climate Change on Marine Organisms and Ecosystems , 2009, Current Biology.

[31]  O. Lindén,et al.  The reefs of Mauritius , 2000 .

[32]  P. W. Glynn,et al.  Coral reef bleaching: ecological perspectives , 1993, Coral Reefs.

[33]  W. Skirving,et al.  The Sea Surface Temperature Story on the Great Barrier Reef during the Coral Bleaching Event of 1998 , 2001 .

[34]  T. Lenton,et al.  The coral reef crisis: the critical importance of<350 ppm CO2. , 2009, Marine pollution bulletin.

[35]  J. Lough,et al.  Coral bleaching: patterns, processes, causes and consequences , 2009 .

[36]  William J. Skirving,et al.  A comparison of the 1998 and 2002 coral bleaching events on the Great Barrier Reef: spatial correlation, patterns, and predictions , 2004, Coral Reefs.

[37]  Scarla J. Weeks,et al.  Climate variability of the Great Barrier Reef in relation to the tropical Pacific and El Niño-Southern Oscillation , 2012 .

[38]  Robert Frouin,et al.  Estimating Photosynthetically Active Radiation (PAR) at the earth's surface from satellite observations , 1995 .

[39]  Z. Ristovski,et al.  Can corals form aerosol particles through volatile sulphur compound emissions , 2012 .

[40]  David Obura,et al.  Resilience and climate change: lessons from coral reefs and bleaching in the Western Indian Ocean , 2005 .

[41]  Richard H. Grant,et al.  Photosynthetically-active radiation: sky radiance distributions under clear and overcast conditions , 1996 .

[42]  T. J. Barton,et al.  THE AUSTRALIAN CLIMATOLOGY OF BIOLOGICALLY EFFECTIVE ULTRAVIOLET RADIATION , 1979, The Australasian journal of dermatology.

[43]  B. Willis,et al.  Seasonal and local spatial patterns in the upper thermal limits of corals on the inshore Central Great Barrier Reef , 1999, Coral Reefs.

[44]  P. A. Blight.  The Analysis of Time Series: An Introduction , 1991 .

[45]  Tim R. McClanahan,et al.  Conservation of Coral Reefs after the 1998 Global Bleaching Event , 2000 .

[46]  G. Quinn,et al.  Experimental Design and Data Analysis for Biologists , 2002 .

[47]  P. Ralph,et al.  Variation in bleaching sensitivity of two coral species across a latitudinal gradient on the Great Barrier Reef: the role of zooxanthellae , 2006 .

[48]  C. Wilkinson.  Global and local threats to coral reef functioning and existence: review and predictions , 1999 .

[49]  Stefano Schiavon,et al.  Climate Change 2007: The Physical Science Basis. , 2007 .

[50]  Y. Loya,et al.  Coral Health and Disease , 2004, Springer Berlin Heidelberg.

[51]  K. Lau,et al.  Mechanisms of Short-Term Sea Surface Temperature Regulation: Observations during TOGA COARE. , 1997 .

[52]  B. Brown,et al.  Coral bleaching--capacity for acclimatization and adaptation. , 2003, Advances in marine biology.

[53]  I. Musat,et al.  On the contribution of local feedback mechanisms to the range of climate sensitivity in two GCM ensembles , 2006 .

[54]  G. Russ.  Distribution and abundance of herbivorous grazing fishes in the central Great Barrier Reef. I: Levels of variability across the entire continental shelf , 1984 .

[55]  K. Mann,et al.  Dynamics of Marine Ecosystems , 1991 .

[56]  M. King,et al.  Cloud Retrieval Algorithms for MODIS : Optical Thickness , Effective Particle Radius , and Thermodynamic Phase , 2000 .

[57]  Eric Wolanski,et al.  Physical Oceanographic Processes of the Great Barrier Reef , 1994 .

[58]  T. Done,et al.  Patterns in the distribution of coral communities across the central Great Barrier Reef , 2004, Coral Reefs.

[59]  I. Masiri,et al.  A 10‐year climatology of solar radiation for the Great Barrier Reef: implications for recent mass coral bleaching events , 2008 .

[60]  William Leggat,et al.  The effect of thermal history on the susceptibility of reef-building corals to thermal stress , 2008, Journal of Experimental Biology.

[61]  E. Brown,et al.  Global warming, regional trends and inshore environmental conditions influence coral bleaching in Hawaii , 2004 .

[62]  P. Crutzen,et al.  Atmospheric aerosols: Biogeochemical sources and role in atmospheric chemistry , 1997 .

[63]  B. Santer,et al.  Penetration of Human-Induced Warming into the World's Oceans , 2005, Science.

[64]  Y. Takahashi,et al.  27-day variation in cloud amount in the Western Pacific warm pool region and relationship to the solar cycle , 2010 .

[65]  P. Jokiel.  Temperature Stress and Coral Bleaching , 2004 .

[66]  A. Tompkins.  On the Relationship between Tropical Convection and Sea Surface Temperature , 2001 .

[67]  J. Lough.  Climate variation and El Niño-Southern Oscillation events on the Great Barrier Reef: 1958 to 1987 , 1994, Coral Reefs.

[68]  Roger Jones,et al.  Managing Uncertainty in Climate Change Projections – Issues for Impact Assessment , 2000 .

[69]  O. Hoegh‐Guldberg.  Climate change, coral bleaching and the future of the world's coral reefs , 1999 .

[70]  R. Berkelmans.  Chapter 3 Coral Bleaching in Space and Time , 2009 .

[71]  R. Pierrehumbert,et al.  Global warming, convective threshold and false thermostats , 2009 .

[72]  R. Steneck,et al.  Coral Reefs Under Rapid Climate Change and Ocean Acidification , 2007, Science.

[73]  Corinne Le Quéré,et al.  Climate Change 2013: The Physical Science Basis , 2013 .