On Syracuse University Week: Does Earth’s memory hold the key to our future?
Claire Rubbelke, Ph.D. graduate at Syracuse University and Provost’s Postdoctoral Fellow of Engineering at the University of Notre Dame, digs in to find out.
I recently completed my Ph.D. at Syracuse University and started a postdoctoral fellowship at the University of Notre Dame.
My research is centered around the question of whether the short-term extreme weather events we see in the modern will become frequent enough to become part of a region’s mean annual climatology. I use a combination of climate models and biogeochemical proxy data to evaluate the drivers of past climate regime shifts in order to better predict what our future climate may look like.
Does Earth’s Memory Hold The Key To Our Future?
In 2018, after years of intense drought, the city of Cape Town, South Africa was rapidly approaching what the media had dubbed “Day Zero”; the day when Cape Town would run out of water in the municipal water supply.
Luckily, that didn’t happen – strong winter rains rescued Cape Town from this crisis. But both extreme drought and flooding events are becoming more frequent all over the globe, and it is vital to understand how the water cycle will shift in the future in response to global climate change.
The Earth has a long memory, holding on to things like fossils and chemicals in rocks and sediments. Researchers like myself use these fossil memories to explore how climate changed in the past. In particular, I use chemical measurements of ancient leaf waxes in ocean sediments to learn about past rainfall in Southern Africa. My research found that around 1 million years ago, at a time called the Mid-Pleistocene Transition, South Africa’s winter rainfall zone was expanded, but at around 900 thousand years ago, it suddenly shrunk, leading to drier conditions.
To understand how this happened, I examined climate models and I found that these changes in the extent of winter rainfall were due to changes in atmospheric circulation, specifically, changes in the size of the Hadley Cell.
This is the same mechanism that caused the recent Day Zero drought in Cape Town. In the past, Hadley Cell shifts had to persist for many, many years to leave a signature in the sediment record. This raises a very important question: Will the shorter-lived extreme events that we see in the modern become frequent enough that they become part of our average climate state? The answer to that question will be crucial for improving climate resilience and adaptation in communities around the globe.
Read More:
[Nature] – Southern Hemisphere subtropical front impacts on Southern African hydroclimate across the Mid-Pleistocene Transition
