Measuring the Pulse of the Great Barrier Reef and the Coral Reef-Climate Feedback
Abstract:
Measurements of the seasonal variation of dimethylsulfide (DMS) have been made in seawater and the atmosphere at several coral reefs in the central and southern Great Barrier Reef (GBR). Concentrations of both substances increase substantially during the hot summer monsoonal months as seawater temperatures increase, showing close synchrony between seawater and the atmosphere over the GBR. Studies at several reefs have shown that pulses of seawater and atmospheric DMS are regulated by very low tides, followed by rising tides. We present the hypothesis that conditions required to observe aerosol particle, CCN and low cloud formation over coral reefs in the GBR appear to be high solar radiation, low tide, low relative humidity and low wind. It is hypothesised that these pulses of atmospheric DMS and the aerosol precursor substances generated from coral reefs in the GBR take part in low level cloud formation over coral reefs which lowers SST by ~ 0.04-0.29oC normally keeping SSTs in summer <30oC. Disturbingly, in recent years mass coral bleaching episodes have occurred when SSTs have been >30oC, shutting down this coral reef feedback, suggesting that the GBR has now reached a tipping point where mass coral bleaching of reefs may occur every year.