Nav: Home

A new record of deglaciations in last million years shows persistent role of obliquity pacing

March 12, 2020

Over the last million years, small variations in Earth's orbit continued to trigger and terminate global glaciations, throughout and after the Mid-Pleistocene Transition, according to a new study, which presents a novel high-resolution record of the last 11 deglaciations. Beyond what was possible using existing less well-dated environmental records, the new precisely dated chronology reveals the persistent influence of obliquity and insolation in pacing Earth's glacial-interglacial cycle. The Quaternary - the current period of Earth's history that began a little more than 2.5 million years ago (Ma) - is often characterized by a series of glacial and interglacial periods, which repeatedly set continent-sized ice sheets to ebb and flow like a frozen tide across much of the Northern Hemisphere. Before the Mid-Pleistocene Transition (MPT, 1.25 to 0.7 Ma), Quaternary global glacial cycles repeated roughly every 40 thousand years (ka). However, during the MPT, the pattern of Quaternary glaciation fundamentally shifted and expanded to approximately 100 ka intervals. While it is widely agreed that the 40 ka pre-MPT cycles were driven by the cyclical variation in Earth's orbital tilt or obliquity, orbital forcing theories fail to explain the longer post-MPT glacial-interglacial periods adequately. A central challenge in evaluating orbital theories of Earth's ice age cycles is the inherent chronological uncertainty of the deep-ocean sediment records often used to identify them. Recent studies using precisely dated speleothem records to anchor the ages of glacial terminations recorded in marine sediments as far back about 640 ka, however, suggest that post-MPT intervals are instead collections of shorter, orbitally driven cycles. Using a uranium-lead radiometrically dated Italian speleothem from Italy to constrain the chronology of new high-resolution marine sediment records, Petra Bajo and colleagues expand this record to cover the eleven glaciation-deglaciation events of the last million years. The authors show that the first two post-MPT deglaciation events are separated by two obliquity cycles and conclude that Earth's obliquity remained the main driver of glacial-interglacial cycles throughout the Quaternary - across the MPT and beyond.
-end-


American Association for the Advancement of Science

Related Deglaciations Articles:

A new record of deglaciations in last million years shows persistent role of obliquity pacing
Over the last million years, small variations in Earth's orbit continued to trigger and terminate global glaciations, throughout and after the Mid-Pleistocene Transition, according to a new study, which presents a novel high-resolution record of the last 11 deglaciations.
Out of Africa: Did humans migrate quickly and all-at-once or in phases based on weather?
Considerable debate surrounds the migration of human populations out of Africa.
Ghost glaciers and cosmic trips: New GSA Bulletin postings for July 2013
July 2013 GSA Bulletin postings cover the solid Earth's influence on the sea; the diverging geologic histories of the North America Cordillera;
New dating of sea-level records reveals rapid response between ice volume and polar temperature
A new study has revealed a rapid response between global temperature and ice volume/sea-level, which could lead to sea-levels rising by over one meter.
Confirming carbon's climate effects
Harvard scientists are helping to paint the fullest picture yet of how a handful of factors, particularly world-wide increases in atmospheric carbon dioxide, combined to end the last ice age approximately 20,000 to 10,000 years ago.
AGU journal highlights -- March 17, 2011
Huge ocean
Geology highlights: New science posted online March 8, 2011
Highlights of articles scheduled for Geology (posted online March 8, 2011) are provided below.
January 2010 Geology and GSA Today media highlights
Geology includes studies of Mars' Hesperian period and associated thermokarst-style landscapes; plant-leaf compounds and soil microbes in ancient Sierra Nevada river sediments; drowned carbonate reefs in Australia; fossil evidence for the floating fern Azolla in the Eocene Arctic Ocean; the spread of mineral dust from Earth's largest natural source, the Sahara; 44-million-year-old microfossils near Salzburg; sub-seafloor microbes; and the history of the Jurassic Sundance Sea.
May 2008 GEOLOGY media highlights
Topics include high-resolution lunar images related to the Orientale impact; possible methane release event at the icehouse-greenhouse transition 635 million years ago; evidence of oil smoke in sediment from the K-P boundary dinosaur extinction; Greenland Ice Sheet's sensitivity to global warming; what the San Andreas fault-area landscape reveals about earthquakes; a new record of greenhouse warming from central Utah; evidence of a possible glacial land system on Mars; and a sea-level climate change fingerprint.
Changes in Earth's tilt control when glacial cycles end
Scientists have long debated what causes glacial/interglacial cycles, which have occurred most recently at intervals of about 100,000 years.
More Deglaciations News and Deglaciations Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.