You’ve probably heard that a butterfly flapping its wings in Brazil could affect the trajectory of a tornado in Texas? The more I study the Earth system, the less crazy this idea seems to me.
There’s a word I love that comes up in the Earth science literature – teleconnections. It’s a way of describing how geographically distant phenomena are linked.
While we can keep in touch with our friends via satellites for almost instantaneous telecommunications, our two polar regions are having a slower conversation – and some messages may take millennia to arrive. If we want to predict the future of our planet, we need to tap into these Earth system networks.
I study Earth systems history by looking at sediment cores – archives of past environmental change. Sediments build up over time in lakes, bogs and the ocean. By unearthing these natural records, we open a window into the rhythm of the Earth’s cycles.
For my master’s research I reconstructed past climates from geochemical signatures recorded in sediment cores from a lake on Kangaroo Island. I looked at how past periods of increased rainfall on the island might have been driven by changes in the amount of heat contained in the Leeuwin Current (a conduit for warm tropical waters that hugs the west Australian coastline, passing by Kangaroo Island on its way to Tasmania). Our hypothesis is that during times of higher sea-surface temperatures evaporation of seawater increased, leading to more rain over the island.
Teleconnections are also important for understanding sea level rise – proving it’s a problem that goes beyond geopolitical borders. Changes in the Northern Hemisphere can affect how ice melts as far away as Antarctica.
For example, researchers found that the land ice growth in the Northern Hemisphere in the lead up to the peak of the last glacial period led to a global sea level fall that was linked to further growth of the Antarctic Ice Sheet 2,000 years later. Conversely, the rapid melting of ice sheets in the Northern Hemisphere coming out of the last glacial had the effect of greatly increasing and accelerating ice loss in Antarctica.
If we want to predict the future of our planet, we need to tap into these Earth system networks.
Next June, I will be taking a deep dive into the past evolution of the North Atlantic Current and how this affects ice in the Arctic Ocean. I’ll be sailing along the coast of Svalbard as part of an international team of scientists aboard the last voyage of the JOIDES Resolution – a one-of-a-kind floating laboratory specialising in the retrieval of deep-sea sediments. The JOIDES has just returned from the coast of Greenland, where she has been investigating the vulnerability of the Greenland Ice Sheet, the last ice sheet left in the northern hemisphere. There are some catastrophic forecasts about what it might mean to the Earth’s oceans, raising sea levels anywhere from a metre to 7 metres if it melts completely, a scenario that we would reach if global temperatures rise by 3°C above pre-industrial values for a sustained period.
From what I’ve heard, the crew of the JOIDES run a tight ship – so I think this operation will be a far cry from what I’m accustomed to. In the lake on Kangaroo Island, we unearthed 7 metres of sediment in 90cm of water. This gets you back about 7,000 years in Earth history. A mere duck pond and blink of a geological eye by comparison to what we aim to do in the Arctic.
On my upcoming expedition, we plan to drill down to as deep as 700m below the sea floor – first passing through about 1.5km of water. This should get us back 7 million years – a time no human eyes would have been around to witness. We will be at sea, working 12 hours on, 12 hours off, for 2 months – I can already feel my stomach-churning given my tendency to get seasick even on the 45-minute ferry to Kangaroo Island.
On my upcoming expedition, we plan to drill down to as deep as 700m below the sea floor.
We’ll be attempting to reconstruct the history of the North Atlantic Water – retrieving our sediment cores from the only deepwater passage between the North Atlantic and the Arctic Ocean – where water from warmer climates is funnelled to the deep, frozen north. In doing so, we will also be aiming to reconstruct the now gone Svalbard-Barents Sea Ice Sheet – the best modern analogue to the marine-based West Antarctic Ice Sheet – which is a major uncertainty in predicting future global sea level rise.
My specific job aboard the ship will be to take samples of sediment for ancient DNA analysis. Because this ancient DNA is old and degraded, we’ll have to be very careful not to contaminate the samples with intact modern DNA – dressing up head to toe in PPE – like healthcare workers during COVID-19. Otherwise, we might just find human DNA mysteriously appearing in millions-of-years old marine sediments.
From DNA preserved in the sediment we can identify the organisms that were once living on the seafloor and in the water above. Different ice conditions have different biological signatures which can help distinguish between ice states back through time. We can also tell how the marine food web might have changed in response of rapid ice melt in the past – which even has far-reaching implications for processes like carbon cycling.
So how exactly will your local area respond to climate change? The answer might be waiting on the other side of the world.
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