Impacts of fire and flood on land-surface–atmosphere energetics in a sub-tropical barrier island freshwater swamp

Climate change is predicted to lead to a drier and warmer climate in sub-tropical eastern Australia. Drier landscapes are more susceptible to fire, however, increases in daily precipitation extremes, and possible expansion of tropical weather systems into higher latitudes, implies that flooding may also become more common. We use the eddy-covariance technique to evaluate turbulent heat fluxes, and a net radiometer to measure surface albedo, over a groundwater dependent barrier island swamp. Measurements are made for dry and vegetated surface conditions, and following the natural occurrences of a wildfire and flooding. Results show that the wetland Bowen ratio has a value near 1 for typical dry and vegetated conditions, and is dominated by the latent heat flux when inundated by water. The largest changes in the partitioning of available energy into turbulent heat fluxes occur in the days immediately after the wildfire when the surface is dry, with the midday sensible heat flux nearly eight times greater than the latent heat flux. The key influences on energy partitioning are the atmospheric conditions for a dry and vegetated surface, and the surface conditions for either a burnt or a flooded surface.