One study finds that Antarctic icebergs that are gradually melting more and more from the icy continent may be the trigger that plunges the Earth into a new ice age.
Researchers at Cardiff University reconstructed past weather conditions and identified small fragments of Antarctic rock that fell into the open ocean as part of a study designed to understand how glacial ages begin.
The cycles of the ice age of the last 1.6 million years have been marked by periodic changes in the orbit of the Earth’s Sun, which change the amount of solar radiation that reaches the surface.
However, little was known before this study about how changes in solar energy from small changes in orbit could change the Earth’s climate so dramatically.
They discovered that melting icebergs progressively move fresh water from the south to the Atlantic Ocean, melting further from Antarctica, causing a change in ocean circulation and submerging the planet in a cold period, causing an ice age. .
The impact of human-created CO2 emissions could make the South Ocean too hot for Antarctic icebergs to arrive, ending this 1.6 million-year-old ice age cycle that begins with the melting of icebergs, the study authors warned.
The study finds that Antarctic icebergs that are gradually melting more and more from the icy continent could be the trigger that plunges the Earth into a new ice age. Stock image
The team found that Antarctic icebergs gradually remain unmelted to the north during certain changes in the Earth’s Earth orbit, reducing solar energy coming to the surface.
In their study, the team proposes that when the Earth’s orbit around the Sun is correct, Antarctic icebergs begin to melt further and further away from Antarctica.
This translates into a huge shift of freshwater from the southern ocean and into the Atlantic Ocean.
As the southern ocean rises and the North Atlantic cools, large-scale ocean circulation patterns begin to change drastically, removing CO2 from the atmosphere and reducing the so-called greenhouse effect.
In turn, this pushes the Earth to ice age conditions, according to the team, which reconstructed past climatic conditions, including finding small fragments of Antarctic rock fallen into the open ocean 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 remnants of ice gusts, appeared to constantly lead to changes in deep ocean circulation, reconstructed from the chemistry of tiny deep-sea fossils called foraminifera.
The team identified small fragments of Antarctic rock that had been deposited in the open ocean by melting icebergs to track changes in salt and fresh water over time.
The team also used new simulations of climate models to test their hypothesis, finding that icebergs could move huge volumes of fresh water.
The study’s lead author, Aidan Starr, said they were surprised to find that the link between iceberg melting and ocean circulation was present during the onset of each ice age for the past 1.6 million. of years.
“It has been speculated that such an important role for the South Ocean and Antarctica in the global climate, but seeing it so clearly in geological tests was very exciting,” he said.
Professor Ian Hall, co-author of the study and co-scientist of the IODP expedition in Cardiff, said the results provide a “lost nexus” in the history of the ice age.
Antarctic icebergs travel to the southern ocean without melting and move fresh water from that ocean to the Atlantic, causing changes in ocean circulation and cooler periods.
For the past three million years, the Earth has been regularly submerged in ice age conditions, but is currently within an interglacial period where temperatures are warmer.
However, it may not happen the same way again, due to the impact of human-created CO2 emissions that are warming the world.
Researchers suggest that the natural rhythm of ice age cycles may be altered, as the southern ocean will probably become too warm for Antarctic icebergs to travel far enough to cause the necessary changes in ocean circulation. for an ice age to begin.
Professor Hall believes the results can be used to understand how our climate may respond to anthropogenic climate change in the future.
“In the same way that we are seeing an increase in the massive loss of the Antarctic continent and the activity of icebergs in the southern ocean, as a result of the warming associated with current human greenhouse gas emissions,” said Hall.
“Our study emphasizes the importance of understanding iceberg trajectories and melting patterns to develop more robust predictions of their future impact on ocean circulation and climate,” he said.
Professor Grant Bigg, of the Department of Geography at the University of Sheffield, who contributed to the iceberg model simulations, said it was an innovative modeling within climate models.
Adding it was crucial to “identify and support the hypothesis of ice pond debris from the impacts of melting water from Antarctic icebergs that are causing the onset of the glacial cycle.”
The findings have been published in the journal Nature.
ATLANTIC OCEAN CIRCULATION PLAYS A KEY ROLE IN GLOBAL CLIMATE REGULATION
When regulating the global climate, the circulation of the Atlantic Ocean plays a key role.
This is due to a constantly moving deep-water circulation system often referred to as the global ocean conveyor belt, which sends hot, salt water from the Gulf Stream to the North Atlantic, where it releases heat into the atmosphere. and warms Western Europe.
The colder water sinks to great depths and travels to Antarctica and eventually flows back into the Gulf Stream.
When regulating the global climate, the circulation of the Atlantic Ocean plays a key role
This movement is fed by thermohaline currents, a combination of temperature and salt.
Water takes 1,000 years to complete a continuous journey around the world.
Researchers believe that as the North Atlantic began to warm on the brink of the Little Ice Age, freshwater disrupted the system, called the Southern Overturning Circulation (AMOC).
Arctic sea ice, ice sheets, and glaciers surrounding the Arctic began to melt, forming a huge natural freshwater tap that gushed into the North Atlantic.
This huge influx of fresh water diluted the surface seawater, making it lighter and less capable of sinking deep, slowing down the AMOC system.
The researchers found that AMOC has weakened more rapidly since 1950 in response to recent global warming.