Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Significant Role of Oceans in Onset of Ancient Global Cooling

Evidence that early Antarctic Circumpolar Current development affected global climate

Thirty-eight million years ago, tropical jungles thrived in what are now the cornfields of the American Midwest and furry marsupials wandered temperate forests in what is now the frozen Antarctic.

The temperature differences of that era, known as the late Eocene, between the equator and Antarctica were half what they are today.

A debate has been ongoing in the scientific community about what changes in our global climate system led to such a major shift from the more tropical, greenhouse climate of the Eocene to modern and much cooler climates.

New research results published in this week's issue of the journal Science, led by Rensselaer Polytechnic Institute scientist Miriam Katz, are providing some of the strongest evidence to date that the Antarctic Circumpolar Current (ACC) played a key role in the shift.

"What we have found is that the evolution of the Antarctic Circumpolar Current influenced global ocean circulation much earlier than previous studies have shown," said Katz. "This finding is particularly significant because it places the impact of initial shallow ACC circulation in the same interval when the climate began its long-term shift to cooler temperatures."

There has been a debate over the past 40 years on what role the Antarctic Circumpolar Current had in the past cooling trend.

"These climate changes are one of the most significant shifts in Earth's history, from early Cenozoic 'greenhouse' climates to the mid- to late Cenozoic 'icehouse' that saw repeated massive glaciations of the polar regions," said Candace Major, program director in the National Science Foundation's (NSF) Division of Ocean Sciences.

The research was funded by NSF in partnership with the Integrated Ocean Drilling Program, and its predecessor programs, the Ocean Drilling Program and Deep Sea Drilling Project.

"The work by Katz and colleagues is the first to demonstrate that the basic structure of currents associated with modern ocean circulation has existed for the past 33 million years," said Major.

Previous research had placed the development of the deep ACC--greater than 2,000 meters water depth--in the late Oligocene, approximately 23-25 million years ago.

That's well after the global cooling pattern had been established.

Katz and colleagues have placed the global impact of the ACC at approximately 30 million years ago, when it was still just a shallow current.

Oceans and global temperatures are closely linked. Warmer ocean waters result in warmer air temperatures and vice versa.

In the more tropical environs of the Eocene, ocean circulation was weaker and currents more diffuse.

As a result, heat was more evenly distributed around the world. That resulted in fairly mild ocean temperatures worldwide.

Today, ocean temperatures vary considerably and redistribute warm and cold water around the globe.

"As the global ocean currents were formed and strengthened, the redistribution of heat likely played a significant role in the overall cooling of the Earth," Katz said.

No current is more major than the ACC, scientists believe.

Often referred to as the "mixmaster" of the ocean, the ACC thermally isolates Antarctica by preventing the warm surface waters of subtropical gyres from passing through.

The ACC instead redirects some of that warm water back toward the north Atlantic, creating Antarctic Intermediate Water.

This blocking of heat enabled the formation and preservation of the Antarctic ice sheets, according to Katz.

The circumpolar circulation, Katz concludes, was responsible for the development of the modern four-layer ocean current and heat distribution system.

Katz looked at the uptake of several elements' isotopes, or variants, in the fossil skeletons of small planktonic organisms found in ocean sediments.

Using the drillship, the fossil organisms, known as benthic foraminifera, were brought up from beneath the sea-floor in long cores of sediments.

The foraminifera incorporated certain elements and isotopes, reflecting environmental conditions at the time.

By analyzing the ratios of these elements and isotopes, researchers were able to reconstruct past environmental conditions. They looked at isotopes of oxygen and carbon, along with ratios of magnesium versus calcium.

Analysis of these isotopes showed the earliest evidence for Antarctic Intermediate Waters, which circulates as a consequence of the ACC.

This finding is the first evidence of the effects of shallow ACC formation.

The results place the ACC's global impact much closer to the time when Antarctica separated from South America, creating a gateway.

It had previously been thought that currents moving through this gateway could not be strong enough at such shallow depths to affect global ocean circulation.

"By reconstructing the climates of the past, we can explore Earth system responses to current climate change," Katz said.

Katz is joined in the research by Benjamin Cramer of Theiss Research; J.R. Toggweiler of Geophysical Fluid Dynamics Lab/NOAA; Chengjie Liu of Exxon Mobil Exploration Co.; Bridget Wade of University of Leeds; and Gar Esmay, Kenneth Miller, Yair Rosenthal, and James Wright of Rutgers University.

Media Contacts
Cheryl Dybas, NSF (703) 292-7734
Gabrielle DeMarco, RPI (518) 276-6542
Kris Ludwig, Consortium for Ocean Leadership-IODP (202) 448-1254
Related Websites
Integrated Ocean Drilling Program:
Ocean Drilling Program:
Deep Sea Drilling Project:
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2010, its budget is about $6.9 billion. NSF funds reach all 50 states through grants to nearly 2,000 universities and institutions. Each year, NSF receives over 45,000 competitive requests for funding, and makes over 11,500 new funding awards. NSF also awards over $400 million in professional and service contracts yearly.

Cheryl Dybas | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>