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 World’s oldest known oxygen oasis discovered
18.01.2018 | Eberhard Karls Universität Tübingen

nachricht A close-up look at an uncommon underwater eruption
11.01.2018 | Woods Hole Oceanographic Institution

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Polymers Based on Boron?

18.01.2018 | Life Sciences

Bioengineered soft microfibers improve T-cell production

18.01.2018 | Life Sciences

World’s oldest known oxygen oasis discovered

18.01.2018 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>