Rainy day ice age in the global south
Stalactites reveal weather secrets from the ice ages
An international study of the mineral deposits in stalactites in South Australia鈥檚 Naracoorte Caves, has shed new light on climate conditions in the Southern Hemisphere during ice ages.
Research led by Melbourne University and including Naracoorte Caves and fossil forensics expert, Dr Liz Reed from the 成人大片, has turned the established theory about conditions during glacial periods on its head.
鈥淲hat we have found is, that at least in the sub-tropical regions of the Southern Hemisphere, parts of the ice ages were even wetter than what we experience today,鈥 Dr Reed says.
鈥淲here other research has suggested the ice ages were uniformly dry, dusty and inhospitable, in our samples collected from speleothems in two Australian cave regions, the聽聽and the聽, we discovered evidence that we did not expect.
鈥淯sing a 聽based on the decay of naturally occurring聽uranium, we determined the age of more than 300 individual speleothem fragments from the caves and then produced a precipitation record spanning the past 350,000 years.鈥
One way to understand how wet it was in the past is to look at mineral deposits called聽, found in underground caves. These deposits, which include stalagmites and stalactites, build up over time as rainwater filters down through soil and limestone into the cave.
The extent of speleothem growth over time reflects changes in water availability. More speleothem growth broadly indicates wetter conditions, while less growth suggests a drier environment.
鈥淚t is broad, but the pattern we found was clear - wetter times occurred within the cooler, glacial periods, while interglacials (warmer periods) were consistently dry,鈥 Dr Reed says.
鈥淭here was also fossil pollen trapped within the same speleothems which allowed us to compare glacial and interglacial periods.鈥
The team found that despite low levels of atmospheric carbon dioxide in glacial periods, the research showed moisture-demanding herbs and shrubs thrived.
The research team benchmarked their results against other public records for sub-tropical areas in South Africa and South America and found consistent evidence that parts of glacial periods had higher rainfall.
鈥淭his has been a really exciting project because it challenged the things we thought we knew about climate conditions during the glacial periods and that challenge leads us to rethink how we interpret the movement and expansion of plants, animals and even humans in the past,鈥 Dr Reed says.