Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Intensification and poleward shift of oceanic boundary currents

28.06.2016

Change means greater heat and more winter storms for Asia; Gulf Stream is the exception

Global warming results in fundamental changes to important ocean currents. As scientists from the Alfred-Wegener-Institute show in a new study, wind-driven subtropical boundary currents in the northern and southern hemisphere are not only going to increase in strength by the end of this century.


The oceans get heat from the tropical regions and release them to the mid-latitudes, especially over the routes of the subtropical western boundary currents.

Photo: F. Rödel / Alfred-Wegener-Institut

The Kuroshio Current, the Agulhas Current and other oceanic currents are shifting their paths towards the pole and thus carry higher temperatures and thus the risk of storms to temperate latitudes. For this study, researchers evaluated a wealth of independent observational data and climate simulations.

They showed the same pattern for all boundary currents, with the Gulf Stream as the only exception. According to the data, the latter will weaken over the next decades. The study has been published today in the Journal of Geophysical Research professional journal.

Along the eastern coasts of South Africa, Asia, Australasia, and South America, weather and climate will get significantly warmer over the next 100 years and thus presumably also significantly stormier on global average. The reason for this are changes to the western boundary currents that are already beginning to have a significant impact on weather events in these coastal regions.

These surface currents are driven by the wind; with flow speeds of up to nine kilometres per hour, they are amongst the fastest ocean currents in the world. They reach down to a depth of 1000 metres and move warm bodies of water from the tropics to the coastal regions of the temperate latitudes.

The best-known western boundary current in Europe is the Gulf Stream. Across the world, however, these also include the Kuroshio Current off the coast of Japan, the Brazil Current off the eastern coast of South America, the Eastern Australia Current as well as the Agulhas Current off the coast of South Africa.

Scientists from the Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research (AWI) have discovered these changes in a major comparative analysis of eleven independent climate data bases. On the one hand, the scientist evaluated oceanographic observational data as well as satellite data on the currents’ heat loss between 1958 and 2001.

On the other, they considered simulations for past and future climates as well as indicators for the flow speed of the currents, for water temperature and air pressure at the sea surface.

“Our analysis shows that the surface temperature of the boundary currents has increased two to three times faster than in other oceanic regions. In addition, the currents release 20 percent more heat than they did half a century ago, which leads to the conclusion that the temperature of the water has risen, its flow speed has increased and the currents thus transfer more water and also more heat from the tropics towards the pole. The cause of these changes were increasing winds in both hemispheres,” explains Hu Yang, AWI climate researcher and author of the study.

The greater the heat transfer from the sea, the higher possibly the probability of storms. “Over the next decades, Japan, China and Korea will need to expect higher air temperatures particularly in winter, because the Kuroshio Current will transport more heat and shift northward with the wind. This heat will change the atmospheric condition in such as way as to make storms more likely in this region. For the Eastern Australian Current, the Brazil Current and the Agulhas Current on the southern hemisphere, our analyses predict a southward shift, because there, too, the winds shift poleward,” explains Prof. Gerrit Lohman, climate modeller at the Alfred-Wegener-Institute and co-author of the study.

The Gulf Stream will become weaker

Warmer, stronger, poleward - according to the results, this pattern applies to all western subtropical boundary currents. The only exception is the Gulf Stream. “All of our results predict its long-term weakening. The reason for this is that the Gulf Stream is not only driven by the wind, but is also coupled with the thermohaline circulation. This is also often referred to as a global conveyor belt.

Our results indicate that the power of this conveyor belt will weaken in the long term - and in an order of magnitude that more than compensate for the plus of increasing winds. Without the influence of this circulation, the Gulf Stream would follow the same patterns as the other boundary currents,” outlines Gerrit Lohmann.

The climate scientists also fear far-reaching consequences for the fauna and flora of the coastal regions. “As these currents bring higher temperatures to these temperate latitudes, while advancing further north or south, many species will be forced to move to colder regions. But some of them won’t be able to face this challenge,” explains Gerrit Lohmann one of the possible consequences of the observed changes.


Notes for Editors:
The study has been published with the following title in the Journal of Geophysical Research:
Hu Yang, Gerrit Lohmann, Wei Wei, Mihai Dima, Monica Ionita, Jiping Liu: Intensification and Poleward Shift of Subtropical Western Boundary Currents in a warming climate, Journal of Geophysical Research, DOI: 10.1002/2015JC011513 , http://onlinelibrary.wiley.com/doi/10.1002/2015JC011513/abstract

Printable photographs can be found in the online version of this press release at: http://www.awi.de/nc/en/about-us/service/press.html

Your scientific contacts at the Alfred Wegener Institute:
• Hu Yang – for interviews in English and Mandarin (tel: +49(471)4831-1051; e-mail: hu.yang(at)awi.de)
• Prof. Dr. Gerrit Lohmann (tel.: +49(471)4831-1758; e-mail: Gerrit.Lohmann(at)awi.de)

Your contact in the Communications and Media Department is Sina Löschke (Tel.: +49 (0)471 4831 - 2008; e-mail: medien(at)awi.de).

The Alfred Wegener Institute conducts research in the Arctic, the Antarctic and in mid- to high-latitude oceans. It coordinates polar research in Germany and provides important infrastructure such as the research icebreaker “Polarstern” and stations in the Arctic and Antarctic for the international science community. The Alfred Wegener Institute is one of the 18 research centres belonging to the Helmholtz Association, Germany's largest scientific organisation.

Ralf Röchert | idw - Informationsdienst Wissenschaft
Further information:
http://www.awi.de/

More articles from Earth Sciences:

nachricht Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

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

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>