‘There is more to rainfall isotopic variability than rainfall amount’

 Costijn Zwart

The stable isotope composition of rainfall that is captured by natural archives (for example, coral and sediment deposits, molluscan shells, tree rings, ice cores etc) are widely used to reconstruct past monsoon variability.

This talk will show some of the latest findings on the interpretation of the paleo climatic stable isotope record in north Australia.

Until now, this interpretation mainly relied on statistical relationships between rainfall amount and isotopic values on monthly timescales. New data shows that the five weather types (monsoon regimes) that constitute the Australian wet season each have a characteristic isotopic signature. The data suggests that this is not only due to changes in regional rainfall amount during these regimes but, more importantly, is due to different rain- and cloud-types that are associated with the large scale circulation regimes. This connection between variability of rainfall isotope anomalies and the intrinsic properties of convection and its large-scale environment has important implications for all fields of research that use rainfall stable isotopes.