Marine scientists are decoding the mechanism for long-term climate fluctuations in the Atlantic

Jul 25, 2013
Deciphering the air-sea communication
This shows time series of the sea surface temperature (blue) and the heat flux (red) in the North Atlantic from 1880 to 2010. Credit: C. Kersten, GEOMAR.

Why does hurricane activity vary from decade to decade? Or rainfall in the Sahel region? And why are the trans-Atlantic changes frequently in sync? A German-Russian research team has investigated the role of heat exchange between ocean and atmosphere in long-term climate variability in the Atlantic. The scientists analyzed meteorological measurements and sea surface temperatures over the past 130 years. It was found that the ocean significantly affects long term climate fluctuations, while the seemingly chaotic atmosphere is mainly responsible for the shorter-term, year-to-year changes. The study appears in the current issue of the prestigious journal Nature, and provides important information on the predictability of long-term climate fluctuations.

How do the ocean and atmosphere communicate? What information do they exchange, and what are the results? These are questions that must ask, especially if they want to understand the cause of fluctuations of varying duration. These fluctuations superimpose the general global warming trend since the beginning of industrialization and thus complicate the accurate determination of on the climate. The causes and mechanisms of natural , however, are poorly understood. A study led by scientists at the GEOMAR Helmholtz Centre for Ocean Research Kiel shows that the influence the heat exchange between ocean and atmosphere and thus can explain climate variability on decadal time scales. The study, which appears in the current issue of the renowned journal Nature, also references the potential for predicting such phenomena.

The presumption of such predictability potential has been around for more than half a century. In 1964, the Norwegian climate researcher Jacob Bjerknes postulated different causes of climate variability on different time scales. While the atmosphere is mainly causing climate variations on shorter time scales, from months to years, the longer-term fluctuations, such as those on decadal time scales, are primarily determined by the ocean. The first part of this hypothesis has been well studied by now, but the second part still required some verification. "In the current study, we can utilize a new analysis of shipboard measurements, taken since the end of the 19th century, to verify the second part of the Bjerknes hypothesis," says Prof. Mojib Latif of GEOMAR, co-author of the study. "In particular, for the long-term climate variability in the Atlantic sector, the Gulf Stream circulation is of vital importance," said Latif.

Deciphering the air-sea communication
This shows the North Atlantic region, dark blue area was used for temperature data, red area for the heat flux. Credit: C. Kersten, GEOMAR.

Ocean currents affect the surface temperature of the oceans and thus the heat exchange with the atmosphere - eventually causing climate variations on the adjacent continents. The most evident is an oscillation with a period of 60 years. "Such decadal climate fluctuations are superimposed on the general warming trend, so that at times it seems as if the warming trend slowed or even stopped. After a few decades, it accelerates once again," explains Prof. Latif. "It is important for us to understand these natural cycles, so that we can finally provide better climate predictions as well." One of the major problems, as Latif explained, is that there are just very few long-term oceanic measurements, thereby complicating the analysis and interpretation of climate change signals. Therefore, scientists are using increasingly refined statistical methods to extract more and more information from the available data sets.

"We need both, realistic model simulations and long-term data records, and really sophisticated analysis methods to produce reliable climate predictions. Our work is an additional piece in the giant puzzle of global climate variability, but I am confident that we will be able to extract the secrets underlying the natural fluctuations," says Prof. Latif.

Explore further: Shifting patterns of temperature volatility in the climate system

More information: Nature, 499, 464-467. doi: 10.1038/nature12268

Related Stories

Recommended for you

Six Nepalese dead, six missing in Everest avalanche

1 hour ago

At least six Nepalese climbing guides have been killed and six others are missing after an avalanche struck Mount Everest early Friday in one of the deadliest accidents on the world's highest peak, officials ...

Clean air: Fewer sources for self-cleaning

15 hours ago

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...

There's something ancient in the icebox

15 hours ago

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised ...

Image: Grand Canyon geology lessons on view

21 hours ago

The Grand Canyon in northern Arizona is a favorite for astronauts shooting photos from the International Space Station, as well as one of the best-known tourist attractions in the world. The steep walls of ...

First radar vision for Copernicus

22 hours ago

Launched on 3 April, ESA's Sentinel-1A satellite has already delivered its first radar images of Earth. They offer a tantalising glimpse of the kind of operational imagery that this new mission will provide ...

User comments : 4

Adjust slider to filter visible comments by rank

Display comments: newest first

NikFromNYC
1.3 / 5 (14) Jul 25, 2013
"The most evident is an oscillation with a period of 60 years."

I plotted a standard version of this cycle at the bottom of the global average temperature for comparison:

http://oi56.tinyp...h021.jpg
Neinsense99
3.8 / 5 (10) Jul 26, 2013
A Republican Secretary of State Urges Action on Climate Change
http://www.scient...d-energy
deepsand
3.4 / 5 (10) Jul 27, 2013
"The most evident is an oscillation with a period of 60 years."

I plotted a standard version of this cycle at the bottom of the global average temperature for comparison:

http://oi56.tinyp...h021.jpg

Spam.
Howhot
4 / 5 (1) Jul 29, 2013
Great article. The more scientist dig, the more we understand how much influence atmospheric CO2 concentrations have on global warming. It's just like Al-Gore said;
"I have faith in the United States and our ability to make good decisions based on the facts."

Keep up the faith.

More news stories

Six Nepalese dead, six missing in Everest avalanche

At least six Nepalese climbing guides have been killed and six others are missing after an avalanche struck Mount Everest early Friday in one of the deadliest accidents on the world's highest peak, officials ...

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

There's something ancient in the icebox

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised ...

Clean air: Fewer sources for self-cleaning

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

Leeches help save woman's ear after pit bull mauling

(HealthDay)—A pit bull attack in July 2013 left a 19-year-old woman with her left ear ripped from her head, leaving an open wound. After preserving the ear, the surgical team started with a reconnection ...