Melting Antarctic icebergs could trigger a chain reaction to the new Ice Age

According to the study, Antarctic icebergs gradually melting further and further away from the frozen continent could be the trigger that is plunging Earth into a new ice age.

Researchers at Cardiff University have reconstructed past climatic conditions and identified tiny fragments of Antarctic rock dumped in the open sea as part of a study to understand how ice ages begin.

The cycles of the Ice Age over the 1.6 million years were punctuated by periodic changes in the Earth’s orbit of the Sun – altering the amount of solar radiation reaching the surface.

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

They found that melting icebergs gradually shifted fresh water from the south to the Atlantic Ocean, melting farther from Antarctica – causing ocean circulation to shift and plunging the planet into a cold spell – triggering an Ice Age. .

The impact of man-made CO2 emissions could make the Southern Ocean too hot for Antarctic icebergs to reach, ending the 1.6 million year cycle glacials beginning with melting icebergs, the study’s authors warned.

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

This results in the movement of huge volumes of fresh water from the Southern Ocean to the Atlantic Ocean.

As the Southern Ocean becomes saltier and the North Atlantic cools off, large-scale ocean circulation patterns begin to change dramatically, removing CO2 from the atmosphere and reducing the so-called greenhouse effect.

This in turn pushes Earth into Ice Age conditions, according to the team, which reconstructed past climatic conditions, including finding tiny fragments of Antarctic rock dropped into the open sea by 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 Debris, appeared to systematically drive changes in deep ocean circulation, reconstructed from the chemistry of tiny deep-sea fossils called foraminifera.

The team also used new climate model simulations to test their hypothesis, finding that huge volumes of fresh water could be displaced by icebergs.

Lead author of the study Aidan Starr, said they were amazed that the link between melting icebergs and ocean circulation was present at the start of every ice age over the 1.6 million years. .

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

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

Over the past three million years, Earth has steadily plunged into Ice Age conditions, but currently sits in an interglacial period where temperatures are warmer.

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

The researchers suggest that the natural rhythm of Ice Age cycles could be disrupted as the Southern Ocean will likely become too warm for Antarctic icebergs to travel far enough to trigger the changes in ocean circulation needed at the onset of an ice age.

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

“As we are seeing an increase in mass loss from the Antarctic continent and iceberg activity in the Southern Ocean, resulting from the warming associated with current greenhouse gas emissions,” Hall said.

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

Professor Grant Bigg, from the Department of Geography at the University of Sheffield, who contributed to the iceberg model simulations, said it was revolutionary modeling in climate models.

The addition was crucial to “identify and support the ice debris hypothesis on the impacts of meltwater from Antarctic icebergs that lead to the onset of the glacial cycle.”

The results were published in the journal Nature.