Featured Research

from universities, journals, and other organizations

Corals provide evidence of changes to oceanic currents

Date:
January 5, 2011
Source:
Universität Basel
Summary:
Examination of deep sea corals reveals that there have been drastic changes to oceanic currents in the western North Atlantic since the 1970s. The influence of the cold water Labrador Current, which is in periodic interchange with the warm Gulf Stream, has been decreasing continually since the 1970s. Occurring at the same time as Global Warming this phenomenon is unique in the past 2000 years.

Annual growth rings of deep sea corals in UV-light.
Credit: A. Sherwood

Examination of deep sea corals reveals that there have been drastic changes to oceanic currents in the western North Atlantic since the 1970s. The influence of the cold water Labrador Current, which is in periodic interchange with the warm Gulf Stream, has been decreasing continually since the 1970s. Occurring at the same time as Global Warming this phenomenon is unique in the past 2000 years.

These results are reported by researchers from the University of Basel and Eawag in the current edition of the Proceedings of the National Academy of Sciences.

One of the oldest known weather systems in the world is the North Atlantic Oscillation (NAO), the periodic variation of atmospheric pressure difference between the Azores and Iceland. It dictates not only whether the winters in Europe will be cold and dry or wet and warm, but also influences the oceanic currents in the North Atlantic. On the continental shelf off Nova Scotia, the NAO seems to control the interaction between different water masses. During positive phases,the oceanography of the north-west American continental shelf is dictated by a relatively warm water mass at 10 degrees Celsius which is salt and nutrient rich, originating from the Gulf Stream. If the NAO is in a negative phase, the Labrador Current is dominant, a relatively cold water mass at 6 degrees Celsius, which is nutrient scarce and originates from sub-polar regions.

Using new geochemical methods, an international team of researchers including the biogeochemists Prof. Moritz Lehmann (University of Basel) and Dr. Carsten Schubert (Eawag -- Swiss Federal Institute of Aquatic Science and Technology) were able to prove that a drastic change to a "warm water mode" occurred in the western North Atlantic in the early 1970s. This change, the timing of which coincides with and may be directly related to Global Warming, is unique in the last 2000 years.

Corals record climate data

The researchers made use of the fact that water masses carry different nitrogen isotopic signatures (different ratios of the stable nitrogen isotopes 15N und 14N) depending on their origins. These signals are then recorded in the biomass of deep sea corals hundreds of metres below the surface that feed on sinking organic particles from above. The deep sea corals thus allow a reconstruction of the oceanic current ratios over the last few decades. An exact dating of the individual samples is possible due to the corals' production of easily identifiable annual growth rings. The researchers were able to show a clear reduction in the 15N/14N ratio since 1970 which indicates that the role of the cold Labrador Current, with a higher 15N/14N ratio is becoming less important.

Possible alternative bio-ecological or geochemical causes for such a change in the stable isotope ratio were able to be excluded by the researchers using component-specific nitrogen analyses of the corals. Depending on the food chain structure, changes occur in the 15N/14N ratio of specific amino acids in the corals' individual annual growth rings. The nitrogen isotope signatures of the amino acids show that the food chain effect did not play a significant role at least since the 1970s.

Global warming with consequences

Isotopic analysis of fossil deep sea corals from the same region confirms that the nitrogen isotope ratios and thus the oceanic current situation have remained practically unchanged over the past 2000 years. This indicates that the oceanographic change in oceanic currents of this scale, which has been occurring since the 1970s, is a unique occurrence within the past 2000 years.

The researchers suspect there is a direct connection between the changes in the oceanic currents in the North Atlantic and Global Warming primarily caused by human activities.


Story Source:

The above story is based on materials provided by Universität Basel. Note: Materials may be edited for content and length.


Journal Reference:

  1. O. A. Sherwood, M. F. Lehmann, C. J. Schubert, D. B. Scott, M. D. McCarthy. Nutrient regime shift in the western North Atlantic indicated by compound-specific δ15N of deep-sea gorgonian corals. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1004904108

Cite This Page:

Universität Basel. "Corals provide evidence of changes to oceanic currents." ScienceDaily. ScienceDaily, 5 January 2011. <www.sciencedaily.com/releases/2011/01/110104064603.htm>.
Universität Basel. (2011, January 5). Corals provide evidence of changes to oceanic currents. ScienceDaily. Retrieved September 2, 2014 from www.sciencedaily.com/releases/2011/01/110104064603.htm
Universität Basel. "Corals provide evidence of changes to oceanic currents." ScienceDaily. www.sciencedaily.com/releases/2011/01/110104064603.htm (accessed September 2, 2014).

Share This




More Earth & Climate News

Tuesday, September 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Sharks Off the Menu and on the Tourist Trail in Palau

Sharks Off the Menu and on the Tourist Trail in Palau

AFP (Sep. 2, 2014) — Tourists in Palau clamour to dive with sharks thanks to a pioneering conservation initiative -- as the island nation plans to completely ban commercial fishing in its vast ocean territory. 01:15 Video provided by AFP
Powered by NewsLook.com
Iceland Lowers Aviation Alert on Volcano

Iceland Lowers Aviation Alert on Volcano

AFP (Sep. 1, 2014) — Iceland has lowered its aviation alert on its largest volcano after a fresh eruption on a nearby lava field prompted authorities to enforce a flight ban for several hours. Duration: 01:07 Video provided by AFP
Powered by NewsLook.com
Lightning Hurts 3 on NYC Beach

Lightning Hurts 3 on NYC Beach

AP (Sep. 1, 2014) — A lightning strike injured three people on a New York City beach on Sunday. The storms also delayed flights and interrupted play at the US Open tennis tournament. (Sept. 1) Video provided by AP
Powered by NewsLook.com
Thailand Totters Towards Waste Crisis

Thailand Totters Towards Waste Crisis

AFP (Sep. 1, 2014) — Fears are mounting in Bangkok that poor planning and lax law enforcement are tipping Thailand towards a waste crisis. Duration: 01:21 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins