CLIMATE VARIATION AND EL-NINO SOUTHERN OSCILLATION EVENTS ON THE GREAT-BARRIER-REEF - 1958 TO 1987

Seasonal and inter-annual variation of several surface climate variabl es near the Great Barrier Reef (GBR) are described for the 30-year per iod, 1958-1987. Large inter-annual variability of rainfall and river f low in coastal Queensland is linked to the aperiodic influences of El Nino-Southern Oscillation events. These events also affect sea surface temperature and wind fields, though the inter-annual variability of t hese variables is not as large as rainfall and river flow. The major i mpacts on waters of the GBR appear to be greatly increased freshwater inputs, reduced surface radiation (and thus light levels) and enhanced tropical cyclone activity during anti-El Nino events. El Nino events have less effect on climate of the GBR because they tend to maintain w inter-like conditions. The effects of this background of high variabil ity in the physical environment on reef processes must be considered w hen examining changes in such processes, changes in climate (e.g. due to global warming) or increases in anthropogenic impacts.