7000 years of drought and rainfall found in preserved leaves
A study by 成人大片 researchers and Queensland Government scientists has revealed what south-east Queensland鈥檚 rainfall was like over the last 7000 years 鈥 including several severe droughts worse and longer lasting than the 12-year Millennium Drought.
The study 鈥 published in听听- used preserved paper-bark tea tree leaves from North Stradbroke Island鈥檚 Swallow Lagoon that have been collecting in the sediment for the past 7700 years.
The leaves 鈥 analysed for chemical variation - provided a wealth of information on the El Ni帽o-Southern Oscillation (ENSO) and how it was impacted by major climate changes over the millennia, including the Little Ice Age from about 1450 to 1850.
Researchers found a generally wet period about 5000 to 6000 years ago 鈥 indicating a more consistent La Ni帽a-like climate.
鈥淭his changed to a more variable and increasingly drier climate about 3000 years ago 鈥 highlighting a strengthened El Ni帽o phase,鈥欌 says from the 成人大片鈥檚 Geography Department.
鈥淭here were substantial droughts during this phase, drier than the Millennium Drought which south-east Australia experienced from 1997-2009. In fact, from what we can ascertain, the probability of a drought worse than the Millennium Drought is much higher than the current prediction of one in 10,000 years.
鈥淥ur rainfall reconstruction suggests that it may be as much as 10 times more likely.鈥
Associate Professor Tibby said the Little Ice Age, which ended about the time south-east Queensland was settled, was unusually wet.
The study was possible because Swallow Lagoon contains a continuous sequence of leaves from a single species of tree. Variations in the chemistry of these leaves allowed scientists to reconstruct past rainfall.
鈥淔inding leaves preserved in lake sediments of this age is rare, and they can tell us a lot about the environment. For instance, the carbon isotope composition 鈥 or chemistry 鈥 of the leaves can tell us about the degree of moisture stress experienced by the plants when the leaves were growing,鈥欌 says from the 成人大片.
鈥淪o, in effect, we can use leaf carbon isotope composition to infer rainfall through time. Since North Stradbroke Island is in a part of Australia that is very sensitive to ENSO, our study is able to document ENSO history.鈥
Original story in the news.
The study 鈥 published in听听- used preserved paper-bark tea tree leaves from North Stradbroke Island鈥檚 Swallow Lagoon that have been collecting in the sediment for the past 7700 years.
The leaves 鈥 analysed for chemical variation - provided a wealth of information on the El Ni帽o-Southern Oscillation (ENSO) and how it was impacted by major climate changes over the millennia, including the Little Ice Age from about 1450 to 1850.
Researchers found a generally wet period about 5000 to 6000 years ago 鈥 indicating a more consistent La Ni帽a-like climate.
鈥淭his changed to a more variable and increasingly drier climate about 3000 years ago 鈥 highlighting a strengthened El Ni帽o phase,鈥欌 says from the 成人大片鈥檚 Geography Department.
鈥淭here were substantial droughts during this phase, drier than the Millennium Drought which south-east Australia experienced from 1997-2009. In fact, from what we can ascertain, the probability of a drought worse than the Millennium Drought is much higher than the current prediction of one in 10,000 years.
鈥淥ur rainfall reconstruction suggests that it may be as much as 10 times more likely.鈥
Associate Professor Tibby said the Little Ice Age, which ended about the time south-east Queensland was settled, was unusually wet.
The study was possible because Swallow Lagoon contains a continuous sequence of leaves from a single species of tree. Variations in the chemistry of these leaves allowed scientists to reconstruct past rainfall.
鈥淔inding leaves preserved in lake sediments of this age is rare, and they can tell us a lot about the environment. For instance, the carbon isotope composition 鈥 or chemistry 鈥 of the leaves can tell us about the degree of moisture stress experienced by the plants when the leaves were growing,鈥欌 says from the 成人大片.
鈥淪o, in effect, we can use leaf carbon isotope composition to infer rainfall through time. Since North Stradbroke Island is in a part of Australia that is very sensitive to ENSO, our study is able to document ENSO history.鈥
Original story in the news.
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