Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mysterious climate change

22.06.2020

New research findings underline the crucial role that sea ice throughout the Southern Ocean played for atmospheric CO2 in times of rapid climate change in the past. An international team of scientists with the participation of the University of Bonn has shown that the seasonal growth and destruction of sea ice in a warming world increases the biological productivity of the seas around Antarctica by extracting carbon from the atmosphere and storing it in the deep ocean. This process helps to explain a long-standing question about an apparent 1,900-year pause in CO2 growth during a period known as the Antarctic cold reversal. The results have now been published in "Nature Geoscience".

Surrounding the remote continent of Antarctica, the Southern Ocean is one of the most important yet poorly understood components of the global carbon cycle.


The diagram shows the Patriot Hills (left) and the blue ice field of the Horseshoe Valley (right), where older ice is pushed to the surface.

© Matthew Harris


Surface of the blue ice field in Horseshoe Valley exposed by wind erosion. The erected layers show younger ice on the right and older ice on the left.

© Chris Turney

Having captured half of all human-related carbon that has entered the ocean to date, the Southern Ocean is crucial to regulating human-induced CO2.

Therefore, understanding the processes that determine its effectiveness as a carbon sink through time are essential to reducing uncertainty in climate projections.

After the Last Ice Age, around 18,000 years ago, the world transitioned naturally into the warm interglacial world we live in today. During this period, CO2 rose rapidly from around 190 ppm to 280 ppm over around 7,000 years.

This rise was not steady, and was interrupted by rapid rises and intermittent plateaus, reflecting different processes within the global carbon cycle.

Antarctic Cold Reversal

One period stands out: a 1,900-year plateau of near-constant CO2 levels at 240 ppm starting some 14,600 years ago called the Antarctic Cold Reversal. The cause of this plateau remains unknown, but understanding the processes may be critical for improving projections surrounding climate-carbon feedbacks.

“We found that in sediment cores located in the sea-ice zone of the Southern Ocean biological productivity increased during this critical period, whereas it decreased farther north, outside of the sea-ice zone”, says Michael Weber, co-author of the study from the Institute for Geosciences at the University of Bonn.

“It was now important to find out how climate records on the Antarctic continent depict this critical time period.”

To resolve this question researchers from Keele University, U.K., and the University of New South Wales (UNSW) in Sydney, Australia, travelled to the Patriot Hills Blue Ice Area to obtain new records of marine biomarkers captured in ice cores.

Chris Fogwill, lead author of the study from Keele University, says “the cause of this long plateau in global atmospheric CO2 levels may be fundamental to understanding the potential of the Southern Ocean to moderate atmospheric CO2.

Whilst recent reductions in emissions due to the Covid-19 pandemic have shown that we can reduce CO2, we need to understand the ways in which CO2 levels have been stabilised by natural processes, as they may be key to the responsible development of geoengineering approaches and remain fundamental to achieving our commitment to the Paris Agreement”.

Horizontal ice core analysis

Blue ice areas are created by fierce, high-density katabatic winds that erode the top layer of snow effectively and expose the ice below. As a result, ice flows up to the surface, providing access to ancient ice below.

While most Antarctic researchers drill down into the ice to extract samples with a conventional ice core, this team used a different method: horizontal ice core analysis. Chris Turney (UNSW, Sydney) says “Instead of drilling kilometres into the ice, we can simply walk across a blue ice area to travel back through time.

This provides the opportunity to sample large volumes of ice necessary for studying new organic biomarkers and DNA that were blown from the Southern Ocean onto Antarctica and preserved in the blue ice.”

The results demonstrated a marked increase in the number and diversity of marine organisms across the 1,900 year period of the CO2 plateau, an observation never seen before.

The team also conducted climate modelling revealing that this period coincided with the greatest seasonal changes in sea ice extent from summer to winter.

Together with the marine cores, these findings provide the first evidence of increased biological productivity record and suggest that processes in the Antarctic Zone of Southern Ocean may have caused the CO2 plateau.

The team will use this work to underpin the development of climate models that seek to improve our understanding of future climate change.

The inclusion of sea ice processes that control climate-carbon feedbacks in a new generation of models will be crucial for reducing uncertainties surrounding climate projections and help society adapt to future warming.

Wissenschaftliche Ansprechpartner:

Michael Weber
Institute for Geosciences
University of Bonn
Phone: 0160-96635405
Email: mike.weber@uni-bonn.de

Originalpublikation:

Southern Ocean carbon sink enhanced by sea-ice feedbacks at the Antarctic Cold Reversal, Nature Geosciences, DOI: 10.1038/s41561-020-0587-0

Johannes Seiler | idw - Informationsdienst Wissenschaft
Further information:
http://www.uni-bonn.de/

More articles from Earth Sciences:

nachricht Typhoon changed earthquake patterns
02.07.2020 | GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre

nachricht Groundwater protection on Spiekeroog Island - first installation of a salt water monitoring system
01.07.2020 | Leibniz-Institut für Angewandte Geophysik (LIAG)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: The lightest electromagnetic shielding material in the world

Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.

Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...

Im Focus: Gentle wall contact – the right scenario for a fusion power plant

Quasi-continuous power exhaust developed as a wall-friendly method on ASDEX Upgrade

A promising operating mode for the plasma of a future power plant has been developed at the ASDEX Upgrade fusion device at Max Planck Institute for Plasma...

Im Focus: ILA Goes Digital – Automation & Production Technology for Adaptable Aircraft Production

Live event – July 1, 2020 - 11:00 to 11:45 (CET)
"Automation in Aerospace Industry @ Fraunhofer IFAM"

The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM l Stade is presenting its forward-looking R&D portfolio for the first time at...

Im Focus: AI monitoring of laser welding processes - X-ray vision and eavesdropping ensure quality

With an X-ray experiment at the European Synchrotron ESRF in Grenoble (France), Empa researchers were able to demonstrate how well their real-time acoustic monitoring of laser weld seams works. With almost 90 percent reliability, they detected the formation of unwanted pores that impair the quality of weld seams. Thanks to a special evaluation method based on artificial intelligence (AI), the detection process is completed in just 70 milliseconds.

Laser welding is a process suitable for joining metals and thermoplastics. It has become particularly well established in highly automated production, for...

Im Focus: A structural light switch for magnetism

A research team from the Max Planck Institute for the Structure of Dynamics (MPSD) and the University of Oxford has managed to drive a prototypical antiferromagnet into a new magnetic state using terahertz frequency light. Their groundbreaking method produced an effect orders of magnitude larger than previously achieved, and on ultrafast time scales. The team’s work has just been published in Nature Physics.

Magnetic materials have been a mainstay in computing technology due to their ability to permanently store information in their magnetic state. Current...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International conference QuApps shows status quo of quantum technology

02.07.2020 | Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Aachen Machine Tool Colloquium AWK'21 will take place on June 10 and 11, 2021

07.04.2020 | Event News

 
Latest News

The lightest electromagnetic shielding material in the world

02.07.2020 | Materials Sciences

Spintronics: Faster data processing through ultrashort electric pulses

02.07.2020 | Information Technology

International conference QuApps shows status quo of quantum technology

02.07.2020 | Event News

VideoLinks
Science & Research
Overview of more VideoLinks >>>