Melting Antarctic icebergs can cause a chain reaction to the new ice age

Icebergs in Antarctica gradually melting further and further away from the frozen continent could be the trigger that plunges Earth into a new Ice Age, study finds.

Researchers at Cardiff University reconstructed past climate conditions and identified tiny fragments of Antarctic rock that had fallen into the open ocean as part of a study designed to understand how ice ages begin.

Ice Age cycles over the past 1.6 million years have been triggered by periodic changes in Earth’s orbit around the sun, causing the amount of solar radiation to reach the surface.

Before this study, however, little was known about how changes in solar energy due to small changes in orbit could so dramatically change the Earth’s climate.

They found that melting icebergs gradually move fresh water from the South to the Atlantic Ocean by melting farther from Antarctica – changing ocean circulation and moving the planet into a cold spell – triggering an Ice Age.

The impact of human-caused CO2 emissions could make the Southern Ocean too warm for Antarctic icebergs to reach, ending this 1.6 million-year cycle of ice ages that begins with icebergs melting, the authors of the report warned. research.

In their study, the team proposes that when Earth’s orbit around the sun is just right, Antarctic icebergs begin to melt further and further away from Antarctica.

This results in massive amounts of fresh water being moved from the Southern Ocean to the Atlantic Ocean.

As the Southern Ocean becomes saltier and the North Atlantic Ocean cooler, large-scale ocean circulation patterns are beginning to change drastically, removing CO2 from the atmosphere and reducing what’s known as global warming.

This, in turn, is pushing Earth into Ice Age conditions, according to the team, which reconstructed past climate conditions, including finding tiny fragments of Antarctic rock that fell into the open ocean from melting icebergs.

The rock fragments were obtained from sediments recovered by the International Ocean Discovery Program (IODP) which represents 1.6 million years of history.

The study found that these deposits, known as Ice-Rafted Debris, appeared to consistently lead to changes in the deep ocean circulation reconstructed from the chemistry of small deep-sea fossils called foraminifera.

The team also used new climate model simulations to test their hypothesis and found that massive amounts of fresh water could be moved through the icebergs.

Lead author of the study Aidan Starr said they were surprised to find that the link between iceberg melting and ocean circulation was present at the beginning of every ice age for the past 1.6 million years.

“Such a leading role for the Southern Ocean and Antarctica in the global climate has been speculated, but it was very exciting to see it so clearly in geological evidence,” he said.

Professor Ian Hall, co-author of the study and co-chief scientist of the IODP Expedition, from Cardiff, said the results represent a “missing link” in the history of the Ice Age.

Over the past three million years, the Earth has been regularly immersed in ice ages, but is currently in an interglacial period when temperatures are warmer.

However, it may not happen in the same way again, due to the impact of human-made CO2 emissions warming the world.

Researchers suggest that the natural rhythm of Ice Age cycles may be disrupted, as the Southern Ocean is likely to become too warm for Antarctic icebergs to travel far enough to bring about the changes in ocean circulation needed to create an Ice Age. let it begin.

Professor Hall believes the results can be used to understand how our climate may respond to anthropogenic climate change in the future.

“Likewise if we see an increase in the Antarctic continent’s mass loss and Southern Ocean iceberg activity, due to warming related to current human greenhouse gas emissions,” Hall said.

“Our study emphasizes the importance of understanding iceberg trajectories and melting patterns in developing the most robust predictions of their future impact on ocean circulation and climate,” he said.

Professor Grant Bigg, from the University of Sheffield’s Department of Geography, who contributed to the simulations of iceberg models, said this was groundbreaking modeling within the climate models.

Its addition was critical in “identifying and supporting the hypothesis of ice raft debris of the effects of meltwater on the Antarctic iceberg, triggering the onset of the glacial cycle.”

The findings are published in the journal Nature.