Scientists have discovered more than 700 traces on the seabed off the east coast of the United States, left by icebergs that scraped the bottom thousands of years ago.
When you think of Florida, you undoubtedly think of the beaches along the azure sea, palm trees and the sun shining in abundance. It’s hard to imagine that huge icebergs could be enjoyed on the same beaches in the Sunshine State 31,000 years ago. However, it’s true, say the journal’s researchers Natural connections. “The idea that icebergs can reach Florida is incredible,” said researcher Alan Condron.
Condron and his colleagues mapped the seabed off the east coast of the United States. This results in the discovery of massive plow paths from Cape Hatteras, North Carolina, to the Florida Keys. They were left behind by huge icebergs (over 300 meters thick) which, while scraping the bottom, moved south along the east coast of the United States.
“The discovery of plow tracks on such a low line is very unexpected,” Condon said. “Not only because of the unusually high rate of snowmelt in this region, but also because the runways are under the Gulf Stream moving north.” This means that the icebergs have moved against the tide. And not just a short distance, but over 5,000 kilometers!
The researchers sampled the sediments that filled the plow paths left by the icebergs over time. By dating him, they were able to determine when the icebergs were dragged along the bottom. It turns out that this happened about 31,000 years ago, during the so-called Heinrich event. This is a natural phenomenon where a large number of icebergs are released from glaciers and end up in the North Atlantic Ocean.
Using the models, the researchers studied how the icebergs moved further south. The model reveals that icebergs can only go as far as when huge amounts of meltwater are dumped into Hudson Bay when a glacial lake enters its shores. “Such a tidal wave creates a cool, rapid southerly current that carries icebergs to Florida,” Condron said. And when the researchers simulated such an island wave with their model, the model predicted the formation of plow paths where they actually were. “What our model suggests is that these icebergs are carried by currents – created by glacial meltwater – and actually surf along the coast. When a large glacial lake crosses its shores and releases massive amounts of meltwater into the ocean, there is enough water to create such a current. strong along the coast that moves icebergs against the Gulf Stream. So icebergs can reach Florida. In fact, the model suggests that icebergs could travel further south and hit the Bahamas.
The research is important because it could provide more information on how meltwater affects ocean currents. It is feared that climate change – and the resulting melting of the ice caps – will weaken these currents (see box).
The Atlantic Meridian Inversion (AMOC) occurrence is located in the Atlantic Ocean. It’s probably best to compare the AMOC to a supermarket treadmill. At the surface, hot water is brought north of the equator. The water cools down all the way. In addition, more water evaporates along the way than fresh water is added to it, which increases the salt concentration. The further north you go, the colder and more salty the water will be. It also makes the water heavier. The result? It sinks in the north, after which it is pumped – in depth – towards the equator. There, it heats up again and the story begins again. However, climate change threatens to disrupt this flow, due to the rapid warming of the Arctic, especially Greenland. Greenland has a huge ice cap that is melting due to global warming and bringing large amounts of (fresh) meltwater into the ocean. This mixes with salt water, making it less salty and therefore less heavy. This water sinks easily into the depth, and therefore your mother becomes weaker. The weakening of AMOC could also have serious consequences for surrounding regions, such as Western Europe. AMOC releases some of the heat it carries north into the atmosphere, causing temperatures in Western Europe to be warmer than they would have been in the absence of AMOC.
What the new research has shown is that meltwater may have traveled south for thousands of years. Although it was eventually transported north again by the Gulf Stream, once it got north it would have been much saltier due to the mixing along the way. However, it is likely that the meltwater would have a much smaller impact on AMOC than if it had already found its way into the current in the Far North. According to the researchers, this shows that the effect of meltwater on flow – and therefore also on the climate of surrounding areas – may be more complex than previously thought.
So the traces left by icebergs on the seabed thousands of years ago have implications for today. “Now that we can create more detailed computer models, we can also determine more precisely how the ocean turns,” said researcher Gina Hill. This, in turn, determines how fresh meltwater is transported and can affect AMOC – and climate.