Date:

What causes an ice age to end?

New University of Melbourne research has revealed that ice ages over the last million years ended when the tilt angle of the Earth’s axis was approaching high values.

During these times, longer and stronger summers melted the large Northern Hemisphere ice sheets, propelling the Earth’s climate into a warm ‘interglacial’ state, like the one we’ve experienced over the last 11,000 years.

The study by PhD candidate, Petra Bajo, and colleagues also showed that summer energy levels at the time these ‘ice-age terminations’ were triggered controlled how long it took for the ice sheets to collapse, with higher energy levels producing fast collapse.

Researchers are still trying to understand how often these periods happen and how soon we can expect another one.

- Advertisement -

Since the mid 1800s, scientists have long suspected that changes in the geometry of Earth’s orbit are responsible for the coming and going of ice ages – the uncertainty has been over which orbital property is most important.

Petra Bajo’s paperPersistent influence of obliquity on ice age terminations since the Middle Pleistocene transition, published today in Science, moves closer to resolving some of the mystery of why ice ages end by establishing when they end.

The team combined data from Italian stalagmites with information from ocean sediments drilled off the coast of Portugal.

“Colleagues from the University of Cambridge and Portugal’s Instituto Português do Mar e da Atmosfera compiled detailed records of the North Atlantic’s response to ice-sheet collapse,” said Associate Professor Russell Drysdale, from the research team.

“We could identify in the stalagmite growth layers the same changes that were being recorded in the ocean sediments. This allowed us to apply the age information from the stalagmite to the ocean sediment record, which cannot be dated for this time period.”

Using the latest techniques in radiometric dating, the international team determined the age of two terminations that occurred about 960,000 and 875,000 years ago.

The ages suggest that the initiation of both terminations is more consistent with increases in Earth’s tilt angle. These increases produce warmer summers over the regions where the Northern Hemisphere ice sheets are situated, causing melting.

“Both terminations then progressed to completion at a time when Northern Hemisphere summer energy over the ice sheets approached peak values,” said Dr Drysdale. “A comparison of these findings with previously published data from younger terminations shows this pattern has been a recurring feature of the last million years.”

The team plan to have a closer look next at the Middle Pleistocene Transition when the average length of ice-age cycles suddenly doubled in length.

UNIVERSITY OF MELBOURNE

Header Image – Galleria delle Stalattiti, Corchia Cave – Credit : Linda Tegg

- Advertisement -
Mark Milligan
Mark Milligan
Mark Milligan is an award winning journalist and the Managing Editor at HeritageDaily. His background is in archaeology and computer science, having written over 7,500 articles across several online publications. Mark is a member of the Association of British Science Writers (ABSW), the World Federation of Science Journalists, and in 2023 was the recipient of the British Citizen Award for Education and the BCA Medal of Honour.

Mobile Application

spot_img

Related Articles

Inca quarries and road network found in Cañete

Archaeologists have discovered Inca quarries and a road network in Cerros de Quilmaná and Cerro Quinta Freno, in the province of Cañete, Peru.

Prison bakery for enslaved people found in Roman Pompeii

Archaeologists have uncovered a Prison bakery during recent excavations in Pompeii.

Baboons in Ancient Egypt were raised in captivity before being mummified

In a new study published in the open-access journal PLOS ONE, researchers examined a collection of baboon mummies from the ancient Egyptian site of Gabbanat el-Qurud, the so-called Valley of the Monkeys on the west bank of Luxor.

Archaeologists find 22 mummified burials in Peru

A Polish-Peruvian team of archaeologists have uncovered 22 mummified burials in Barranca, Peru.

Oldest prehistoric fortress found in remote Siberia

An international team, led by archaeologists from Freie Universität Berlin has uncovered an ancient prehistoric fortress in a remote region of Siberia known as Amnya.

Top 10 archaeological discoveries of 2023

The field of archaeology has been continuously evolving in 2023, making significant strides in uncovering new historical findings, preserving cultural heritage, and employing innovative technologies to study the past.

War in Ukraine sees destruction of cultural heritage not witnessed since WW2

The full-scale Russian invasion of Ukraine on 24 February 2022 has resulted in a significant loss of human lives and the national and international displacement of many Ukrainian people.

Archaeologists find five Bronze Age axes in the forests of Kociewie

According to an announcement by the Pomeranian Provincial Conservator of Monuments, archaeologists have discovered five Bronze Age axes in Starogard Forest District, located in Kociewie, Poland.