Ice ages were not as dry as we thought, according to surprising new Australian cave study
Retrieved on:
Wednesday, February 7, 2024
During ice ages, dry, frozen terrain extended over much of northern Europe, Asia and North America.
Key Points:
- During ice ages, dry, frozen terrain extended over much of northern Europe, Asia and North America.
- For a long time scientists have thought that dry conditions prevailed across the globe during ice ages, and that the warm periods between ice ages were much wetter.
Ice ages and hemispheres
- Over the past million years or so, Earth’s climate has oscillated between cold ice ages (or “glacial” periods) and warmer “interglacial” periods.
- During glacial periods, temperatures were lower, there was less carbon dioxide in the atmosphere, and ice sheets covered more of the globe.
- Evidence from the northern hemisphere shows huge ice sheets spread across the northern parts of Europe, northern Asia and North America during glacial periods, and large areas south of the ice were covered with tundra.
Developing a 350,000 year climate record
- These deposits, which include stalagmites and stalactites, build up over time as rainwater filters down through soil and limestone into the cave.
- We can use the extent of speleothem growth over time to understand changes in water availability.
- Our understanding of past changes in the climate and environment of the southern hemisphere has been limited by a lack of well-dated and long-term records.
- As a result, we produced a precipitation record spanning the last 350,000 years.
Wetter and colder, warmer and drier
- Over the past 350,000 years, wetter times always occurred within the cooler, glacial periods, while interglacials were consistently dry.
- We found wet glacials and dry interglacials were not confined to southern Australia, but in fact, formed a hemisphere-wide pattern.
Stable environments with abundant water
- However, our research suggests that – at least in the subtropical southern hemisphere – glacial periods were often times of relatively stable environments with abundant water, even if low levels of carbon dioxide meant plants were slow-growing and relatively unproductive.
- Our research calls for a big paradigm shift in how we view past ice-age environments across the Earth.
Rieneke Weij receives funding from the University of Cape Town and the Oppenheimer Memorial Trust. Jon Woodhead receives funding from the Australian Research Council Josephine Brown receives funding from the National Environmental Science Program and the Australian Research Council. Kale Sniderman receives funding from the Australian Research Council Liz Reed receives funding from Australian Research Council.