“Missing Link” Found in Process That Leads to an Ice Age on Earth
New study unravels long-standing climate mystery and provides insight into how our planet may change in the future.
Scientists claim to have found the “missing link” in the process that leads to an ice age on Earth.
Melting icebergs in the Antarctic are the key, say the team from Cardiff University, triggering a series of chain reactions that plunges Earth into a prolonged period of cold temperatures.
The findings have been published in Nature from an international consortium of scientists from universities around the world.
It has long been known that ice age cycles are paced by periodic changes to Earth’s orbit of the sun, which subsequently changes the amount of solar radiation that reaches the Earth’s surface.
However, up until now it has been a mystery as to how small variations in solar energy can trigger such dramatic shifts in the climate on Earth.
In their study, the team propose that when the orbit of Earth around the sun is just right, Antarctic icebergs begin to melt further and further away from Antarctica, shifting huge volumes of freshwater away from the Southern Ocean and into the Atlantic Ocean.
As the Southern Ocean gets saltier and the North Atlantic gets fresher, large-scale ocean circulation patterns begin to dramatically change, pulling CO2 out of the atmosphere and reducing the so-called greenhouse effect.
This in turn pushes the Earth into ice age conditions.
As part of their study the scientists used multiple techniques to reconstruct past climate conditions, which included identifying tiny fragments of Antarctic rock dropped in the open ocean by melting icebergs.
The rock fragments were obtained from sediments recovered by the International Ocean Discovery Program (IODP) Expedition 361, representing over 1.6 million years of history and one of the longest detailed archives of Antarctic icebergs.
The study found that these deposits, known as Ice-Rafted Debris, appeared to consistently lead to 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 freshwater could be moved by the icebergs.
Lead author of the study Aidan Starr, from Cardiff University’s School of Earth and Environmental Sciences, said: “We were astonished to find that this lead-lag relationship was present during the onset of every ice age for the last 1.6 million years. Such a leading role for the Southern Ocean and Antarctica in global climate has been speculated but seeing it so clearly in geological evidence was very exciting”.
Professor Ian Hall, co-author of the study and co-chief scientist of the IODP Expedition, also from the School of Earth and Environmental Sciences, said: “Our results provide the missing link into how Antarctica and the Southern Ocean responded to the natural rhythms of the climate system associated with our orbit around the sun.”
Over the past 3 million years the Earth has regularly plunged into ice age conditions, but at present is currently situated within an interglacial period where temperatures are warmer.