Antarctic ice cores can extend existing climate records and provide catchment-specific climate information for water resource managers.
Since the mid-1800s climate records of rainfall and temperature have been collected across Australia. The patterns and statistics obtained from this data have since been used to design water and catchment management systems (such as drought and flood mitigation strategies) and water resources infrastructure.
But is 100 years of climate data long enough to show the full range of rainfall possible in Australia and can we adequately manage water resources in our catchments based on this data?
To answer these questions scientists at the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC) and Australian Antarctic Division are extending existing instrumental climate records for Australian catchments, using thousands of years of sea-salt data obtained from ice cores collected at Law Dome in East Antarctica.
Ice-core sea-salt levels reflect winds over the Southern Ocean, which are connected to large-scale weather patterns that affect Australia. Previous studies have demonstrated how sea-salt variability recorded at Law Dome is related to eastern Australian rainfall, with higher sea-salt levels being associated with higher rainfall and vice versa.
This relationship has recently been exploited to develop a catchment-scale, 1000 year annual rainfall reconstruction for the Williams River catchment; an economically important catchment in the Newcastle region of New South Wales that provides water for urban, agricultural and industrial activities.
The reconstruction shows that significantly longer and more frequent wet and dry periods were experienced in the past 1000 years compared to the past 100 years (see graphic). Although the last 100 years has been drier on average, it is not unprecedented in the context of the last 1000 years, with a particularly dry period evident in the 1100s and 1200s. In addition, there are longer wetter periods in the 1000 year record than have been seen in the recent period. These findings allow us to better characterise flood and drought risk in the Williams River catchment and have implications for managing water resources and infrastructure in the catchment.
This is the first time the link between Antarctic ice cores and Australian rainfall has been exploited to provide catchment-specific climate information for use by water resource managers. The catchment-scale rainfall reconstruction will be utilised to produce a streamflow reconstruction, which can then be incorporated into water resources modelling and management. This will ultimately increase water security and improve the environmental health and sustainability of critical water supply catchments. The method can be expanded to other catchments in Australia that reveal a similar relationship to East Antarctica.
Carly Tozer and Tessa Vance
Read more in: Tozer C. R., Vance T. R., Roberts, J. L., Kiem, A. S., Curran, M. A. J., and Moy, A. D. An ice core derived 1013-year catchment scale annual rainfall reconstruction in subtropical eastern Australia. Hydrol. Earth Syst. Sci.