Experimental SST Anomaly Forecasts
The following plots show the LATEST experimental
sea surface temperature anomaly (SSTA) forecasts for the coming months in the Great Barrier Reef (GBR), Australia.
The top left and right plots show the SSTA forecasts using an ensemble of daily
forecasts from the past 30 days and past 10 days, respectively.
The bottom left plot indicates probabilities of forecast SSTA (30 day ensemble) exceeding 0.6C
in that month. On the bottom right, the plot indicates corresponding model skill for each lead time.

SSTA forecast: 30 member ensemble
SSTA forecast: 10 member ensemble
Probabilistic forecast: SSTA >= 0.6 C
Skill of SSTA forecast
Forecasts are generated from POAMA V1.5 at lead times of 0-5 months for the region. SST anomalies are calculated as the difference between SST values and the climatology, the monthly long term mean SST. Plots are updated daily and are based on the ensemble mean of the last 30 daily forecasts. Information from these 30 forecasts can also be used to determine the likelihood or probability of an event occurring, e.g. SSTA exceeding a particular threshold, which is useful for management applications. Plots based on the ensemble mean of the last 10 forecasts are also presented to highlight any events in the system (e.g. monsoon onset, tropical cyclones) that may have occurred in the past week or so.
To evaluate the accuracy of model forecasts and provide a measure of the skill of the model, hindcasts of SSTA are compared to observed SSTA for the same period. Skill is calculated by correlating model anomalies with observed anomalies in both space and time. Information on spatial and regional average skill is provided on the following page:
Skill of GBR SST forecasts. For further details see Spillman and Alves (2009).
A summary of POAMA SST predictions and model performance for Summer 2008/2009 is also available.
GBR Index Ensemble Distribution
The following plot shows the distribution by quartiles of the ensemble composed of the last 30 forecasts for SST anomalies averaged over the Great Barrier Reef region. The ensemble distribution gives a sense of the certainty of the forecast, and of the relative probabilities of various outcomes. The shading indicates upper and lower climatological terciles from the POAMA 1.5 hindcasts.

Coral Bleaching in the Great Barrier Reef
Sea surface temperature (SST) is now recognised as the primary cause of mass coral bleaching events (Hoegh-Guldberg 1999).
Bleaching results from the loss of symbiotic algae (zooxantheallae) from coral tissues during times of stress, often due to water temperatures higher than the coral colony's tolerance level (Liu et al. 2003). Bleaching has been observed on the Great Barrier Reef since 1982, with severe bleaching events occurring in the summers of 1998, 2002 and 2006. Major bleaching events in Southern Hemisphere reefs (Pacific and Indian Oceans) tend to occur in February-April (Hoegh-Guldberg 1999), with a lag of up to a month in the bleaching response of corals following thermal stress (Berkelmans and Willis 1999). Mortality appears to increase with the intensity of the bleaching event, which is determined by how much and for how long temperatures remain above the maximum mean summer temperatures (Hoegh-Guldberg 1999). For more information on coral bleaching and climate change impacts on reefs refer to the Great Barrier Reef Marine Park Authority.
Seasonal forecasts from coupled dynamical models such as POAMA and remote sensing data products, e.g. ReefTemp (Maynard et al. 2009), can be used to detect anomalous SSTs. These products have revolutionised the way in which coral bleaching events are monitored and assessed in the Great Barrier Reef and Coral Sea (Spillman and Alves 2009).
References
- Berkelmans R. and Willis B., 1999. Seasonal and local spatial patterns in the upper thermal limits of corals on the inshore Central Great Barrier Reef. Coral Reefs 18:219-228.
- Hoegh-Guldberg O., 1999. Coral bleaching, climate change and the future of the world's coral reefs. Review, Marine and Freshwater Research, 50: 839-866.
- Liu G., Strong A.E. and Skirving W., 2003. Remote sensing of sea surface temperatures during 2002 Barrier Reef coral bleaching. EOS 18(15): 137-144.
- Maynard J.A., Johnson J.E., Marshall P.A., Goby G., Schuttenberg H. and Spillman C.M., 2009. A strategic framework for responding to coral bleaching events in a changing climate. Journal of Environmental Management, 44:1-11.
- Spillman C.M. and Alves O., 2009. Dynamical seasonal prediction of summer sea surface temperatures in the Great Barrier Reef. Coral Reefs, 28:197-206.
- Spillman C.M., Alves O., Hudson D.A. and Charles A.N., 2009. POAMA SST predictions for the Great Barrier Reef: Summer 2008/2009. CAWCR Research Letters, 2:30-34.
- Spillman C.M., Alves O., Hudson D.A. and Charles A.N., 2009. New Operational Seasonal SST Products for Prediction of Coral Bleaching in the
Great Barrier Reef. Bulletin of the Australian Meteorological and Oceanographic Society, 22:112-114
- Spillman C.M., Alves O., Hudson D.A. and Charles A.N., 2009. Dynamical Predictions of Summer 2008/2009 SST
for the Great Barrier Reef: A Case Study. Marine and Freshwater Research, submitted.
More POAMA Forecasts
Page last updated: 7 October 2009