Analysis of ancient core samples from the bottom of a lagoon in the Northern Territory suggests future monsoons across northern Australia will be more intense as the global climate warms further.
Analysis of ancient core samples from the bottom of a lagoon in the Northern Territory suggests future monsoons across northern Australia will be more intense as the global climate warms further.
The research links changes in the monsoon season to rapid ice melt in the Northern Hemisphere.
Michael Bird, Distinguished Professor in the College of Science and Engineering at James Cook University, led the study. He said scientists drilled more than 19 metres into the bed of Girraween Lagoon near Darwin and extracted 160 core samples.
"We ended up with the longest pollen record from a lake core in northern Australia, allowing us to examine the patterns of wetting and drying over the past 150,000 years," said Dr. Cassandra Rowe, who identified the pollen in the core.
Professor Bird said the team made a remarkable discovery.
"We showed that the periods of higher rainfall in the past coincide with 'Heinrich events' — large pulses of freshwater into the North Atlantic from rapidly melting ice.
"As current global warming progresses, this means that the Indo-Australian monsoon will become more intense, making northern Australia (and other regions) wetter. Meanwhile, the Northern Hemisphere monsoons will weaken and Southeast Asia will become drier, affecting billions of people," said Professor Bird.
Dr Rowe said the record shows some radical shifts in tree cover over intervals as short as 2000 years.
"Over one 3000-year period, tree proportions increased from 5% to 95%, demonstrating how quickly a changing monsoon can alter ecosystems," said Dr. Rowe.
Professor Bird said a trend of increasing monsoon rainfall in north-western Australia has been underway for the past century, accelerating since the 1950s.
"The data from our study suggests that further slowing of the flow of warm and cold water circulating in the Atlantic – a phenomenon which recent work suggests is on track to pass a tipping point - will reinforce this trend."
Link to paper here.
