Of orbits and ice ages: Researcher confirms that axis shifts help to propel temperature changes

Jan 11, 2012 By Peter Reuell
Peter Huybers, professor of earth and planetary sciences, confirmed that slow changes in both the tilt and orientation of Earth’s spin axis combined to help determine when the major deglaciations of the past million years occurred. Credit: Rose Lincoln/Harvard Staff Photographer

Though it was first suggested well over a century ago, the hypothesis that changes in Earth’s orientation relative to its orbit influence the growth and decline of ice sheets was only recently tested.

As described in a paper recently published in the journal Nature, Harvard Professor of and Planetary Sciences Peter Huybers confirmed that slow changes in both the tilt and orientation of Earth’s spin axis combined to help determine when the major deglaciations of the past million years occurred.

“These periods of deglaciation saw massive climate changes,” Huybers said. “Sea level increased by 130 meters, temperatures rose by about 5 degrees C, and atmospheric CO2 went from 180 to 280 parts per million. We ought to understand what caused these massive changes in past climate if we are to predict long-term changes in future climate with any confidence. And at least now we know with greater than 99 percent confidence that the interaction between obliquity and precession are among the factors that contribute to deglaciation.”

In this context, obliquity refers to the tilt of the spin axis relative to the plane of Earth’s orbit, and precession refers to changes in the direction that the spin axis points, relative to Earth’s elongated, or eccentric, orbit.

While Huybers’ research is the first to prove a connection between obliquity, precession, and deglaciations, suggestions that the Earth’s orbit plays a role in the formation or loss of glaciers are nothing new.

By the early 1840s, just a few years after the notion of the was first articulated by geologist and later Harvard Professor Louis Agassiz, scientists began proposing that orbital changes were behind periods of glaciation. In the intervening 170 years, Huybers said, dozens of additional hypotheses have been presented, but it has been difficult to distinguish between these many competing models.

“We don’t understand why glacial cycles have occurred, not for lack of ideas, but rather because we lack means to rule the wrong ideas out,” Huybers said.  “A lot of people have tried to tie when ice ages started or ended to variations in the orbital cycle, but this is difficult because we don’t know exactly when ice ages occurred in the past.

“Our uncertainty in when deglaciations occurred averages plus or minus 10,000 years during the last million years, and this uncertainty encompasses an entire cycle of precession. Not knowing what the orbital configuration was makes it difficult to test whether any particular orbital configuration influences deglaciation.”

Though it has previously been shown that obliquity — with its longer, roughly 40,000-year cycle — is related to deglaciations, Huybers said, the innovation here was to test for whether obliquity and precession are together related to worldwide glacier loss.

To deal with the uncertainty in the geological records, Huybers developed a methodology through tinkering with “synthetic” records. Essentially, he constructed random realization of glacial cycles to which he added distortions — such as errors in timing and noise in observations — similar to those found in geologic data. Using this synthetic data, he experimented with many techniques until hitting upon one that worked, which he then applied to the actual data, showing the relationship between orbital cycles and deglaciations.

“The pattern that emerges is the following: At the same time we’re seeing high obliquity, we also tend to get an alignment with precession whenever deglaciation occurs,” Huybers said. “When you get that alignment, the radiation that the Northern Hemisphere receives during summer increases by tens of watts per meter squared, and if large Northern ice sheets are present, they tend to disintegrate. These statistical findings agree exactly with what Milutin Milankovitch, a Serbian geophysicist, proposed in the first half of the 20th century.”

Though his work suggests that orbital configuration contributes to the loss of glacial ice, Huybers was quick to emphasize that it is only one factor among many.

“It could also be that orbital forcing causes a rise is atmospheric CO2, and that it’s the increased CO2 that drives the loss of ice sheets,” he said. “In all likelihood, both CO2 and increased summer radiation contribute to deglaciation. They’re both expected to push the climate system toward less ice.

“Another important aspect to consider is that the orbital configuration we now have is almost exactly where it was 20,000 years ago, during the Last Glacial Maximum, but this time we’re near a glacial minimum,” he said. “If you think about what the difference is between then and now, it’s not the orbital configuration, it’s the CO2. I think that’s important to keep in mind, because it shows that glacial changes are not a simple function of the orbital configuration.”

Explore further: Warm US West, cold East: A 4,000-year pattern

Related Stories

Can big earthquakes disrupt world weather?

Apr 29, 2011

(PhysOrg.com) -- The eruption of the Laki volcano in Iceland in 1783-84 set off a cascade of catastrophe, spewing sulfuric clouds into Europe and eventually around the world. Poisonous mists and a resulting ...

Climate scientist studies ancient shorelines

Sep 21, 2011

The seas are rising, as they have during past periods of warming in earth’s history. Estimates of how high they will go in the next few thousand years range from five meters, putting greater Miami underwater, ...

One year of the moon in 2.5 minutes

Jun 15, 2011

We don’t always have the time or ability to see the Moon every night of the year, but this video, from the Goddard Space Flight Center Scientific Visualization Studio, uses data from the Lunar Reconnaissance Orbiter ...

Is there a hidden bias against creativity?

Nov 18, 2011

CEOs, teachers, and leaders claim they want creative ideas to solve problems. But creative ideas are rejected all the time. A new study, which will be published in an upcoming issue of Psychological Science, a journal of the ...

Recommended for you

Warm US West, cold East: A 4,000-year pattern

2 hours ago

Last winter's curvy jet stream pattern brought mild temperatures to western North America and harsh cold to the East. A University of Utah-led study shows that pattern became more pronounced 4,000 years ago, ...

New study outlines 'water world' theory of life's origins

4 hours ago

(Phys.org) —Life took root more than four billion years ago on our nascent Earth, a wetter and harsher place than now, bathed in sizzling ultraviolet rays. What started out as simple cells ultimately transformed ...

Agriculture's growing effects on rain

Apr 15, 2014

(Phys.org) —Increased agricultural activity is a rain taker, not a rain maker, according to researchers at Pacific Northwest National Laboratory and their collaborators at the University of California Los ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

Canman
5 / 5 (2) Jan 11, 2012
This looks like a landmark paper by Peter Huybers. Take an old problem, apply a fresh approach to it, and add to the scientific body of knowledge. The possibility that we would otherwise be in a glacial maximum right now were it not for the current condition of atmosperic gases is astounding. What does that mean for us?
Vendicar_Decarian
3 / 5 (2) Jan 12, 2012
"The possibility that we would otherwise be in a glacial maximum right now were it not for the current condition of atmosperic gases is astounding." - Canman

Possibility = 0

Possibility greater than 0 will require the passage of several thousand more years.
Manhar
1 / 5 (1) Feb 15, 2012
Earths spin axis changes over 26000years. It is called PRECESSION. The knowledge is 500 BC old and has been documented. Currently earth axis points toward pole star but it was not the case in past. The earth axis was pointing star Thuban in Draco constellation in 300BC and in future will be pointing to star Vega in Lyra constellation.
The example of precession is toy top. Make toy top rotating fast and straight up by means provided with toy. It is rotating with its head straight up. Now touch top part and rotation will slow down at the same time top head will start wobbling but still remains in motion. This is how earth wobbles when going through precession cycle. There is a difference. Bottom sharp part of toy top remains at one place on surface and toy top is wobbling around vertical line. In case of earth, south axis rotates in opposite direction of north axis and earth wobbles around 11 degree tilting line from center of earth.
Written more but space does not permit.

More news stories

Warm US West, cold East: A 4,000-year pattern

Last winter's curvy jet stream pattern brought mild temperatures to western North America and harsh cold to the East. A University of Utah-led study shows that pattern became more pronounced 4,000 years ago, ...

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

ESO image: A study in scarlet

This new image from ESO's La Silla Observatory in Chile reveals a cloud of hydrogen called Gum 41. In the middle of this little-known nebula, brilliant hot young stars are giving off energetic radiation that ...

First direct observations of excitons in motion achieved

A quasiparticle called an exciton—responsible for the transfer of energy within devices such as solar cells, LEDs, and semiconductor circuits—has been understood theoretically for decades. But exciton movement within ...

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. That is the message from US tech giants seeking to spread the online gospel to hard-to-reach regions.