Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Modeling Ocean Behavior: The Key to Understanding Our Future Climate

10.09.2004


Scientists have long recognized the importance of oceans in our climate. In fact, the unique physical characteristics of our oceans are largely responsible for making the Earth a livable environment. Oceans are major “climate-controllers” because of their large heat capacity. For instance, it requires four times the amount of energy to raise the temperature of water by one degree than it does soil. As a result, over a long period, oceans can store and transport heat from one location to another. Furthermore, water reacts slowly to the surrounding atmosphere. While this means our oceans may exert relatively little influence in short-term weather, they have a large effect on long-term climate.



Of particular interest is the ocean’s Conveyor Belt or thermohaline circulation, since both temperature and salinity are at the root of its existence. People in the U.S. know it as part of the “Gulf Stream” that carries warm waters north along the U.S. eastern seaboard and across the north Atlantic Ocean.

It then flows south from the European side of the Atlantic, crosses the equator, joins another ocean circulation, and eventually reaches the Pacific, a trip that lasts 1000 years! At high latitudes, cold, dry air from land lowers the average temperature of the warm waters coming from the equator. Evaporation then removes water free of salt and ice formation leaves behind the salty ocean waters. These processes go to increase the ocean’s water density, forcing it to sink, leading to the formation of what is known as the North Atlantic Deep Water (NADW)..


A major player in the thermohaline circulation is a process known as “deep convection,” or DC, that mixes very efficiently warm and cold waters, affects sea ice melting and how much solar radiation is absorbed. DC forms in the Labrador Sea during winter when polar air blows from Canada, removes heat and salt from the waters, and causes it to sink and mix. It is a key feature since it represents the initial stages of the global-scale ventilation loops of the world’s oceans.Outside of the Labrador Sea, DC is confined to small portions of the Weddell and Western Mediterranean Seas.

Computer models are the tools employed by scientists to simulate present oceanic-atmospheric behavior as well as future and past climates. But, due to the limitations of today’s computers, it is not possible to explicitly represent all the important physical processes that govern the climate. Deep convection is one such process that must therefore be modeled in ocean general circulation models (OGCM).

While lab and numerical simulations have brought to light several key features of DC, the translation of this information into a reliable model usable in OGCMs has not yet been achieved, with the result that Deep Convection is still poorly understood.

Dr. Vittorio M. Canuto, a senior scientist at NASA’s Goddard Institute for Space Studies (GISS) and Columbia University’s department of applied physics in New York, has recently focused on how well DC is represented, or modeled, in OGCMs. In a research paper, “Modeling Ocean Deep Convection,” published in the April 2004 issue of Ocean Modelling, Canuto and several colleagues assessed the accuracy of several well-known mixing models widely used by the scientific community to represent DC in the Labrador Sea. They compared the model predictions with data on Labrador DC that has recently become available.

Canuto and colleagues examined three specific mixing models. They foundthat while their NASA-GISS mixing model simulated the observed DC data more faithfully than the other models, it still suffered from problems. For example, it overestimated the depth of DC. Canuto and collaborators are presently trying to determine how the inclusion of rotation may improve the model’s performance.

This study is particularly timely since in recent years, considerable concern has been expressed about the fragility of the thermohaline circulation to climate change. Increased greenhouse gases would add fresh water to our oceans by melting glaciers. Increased rainfall at high latitudes, as predicted by OGCMs, would further lower ocean’s salinity, inhibiting water from sinking. The net result would be a slow-down of the NADW, depriving much of Europe and eastern North America of warmth. The Younger Dryas, a period of ice-age-like conditions characterized by a partial collapse of the Conveyor Belt around 11,000 years ago, is believed to have been initiated in this manner.

Whether or not human-induced greenhouse gases will affect the thermohalinecirculation is strongly dependent on the future temperature distributionand fresh water supply over the North Atlantic. Most models predictan increase in precipitation in high latitudes and some warming over the North Atlantic within the next 70 years, assuming a doubling of carbon dioxide. However, the extent of projected weakening of the thermohaline circulation varies considerably among the models, with some even indicating little to no change. The details and long-term effect - more than 100 years - of such changes to the ocean circulation have only been explored by a few studies.

"While it is unlikely that climate change will lead to a collapse of thethermohaline circulation, it is possible that DC in the Labrador Sea mightbe severely affected," said Canuto. "Such an event would have a significantimpact on the climate in Europe," he added.

One thing is for certain: the climate system is extremely complex, and many questions remain. Current computer climate models offer a "best guess" as to how scientists believe different climate processes interact. Since scientists do not know exactly how human industry, including transportation and agriculture, will change over the next 100 years, the uncertainty associated with computer climate models will not be much reduced even if today’s climate models were perfect.

Other changes to our oceans, spawned by climate change, may also have a considerable impact on human populations. "If we recall that nearly 100 million people live within one meter of the mean sea level, we can easily understand the societal and economic impacts of a rising sea," said Canuto. "One of the most immediate consequences will be a huge migration of people in the tens of millions, a phenomenon that will seriously burden the host nations."

Inevitably, the discussion turns back to the influence of human behavior. A few scientists believe that the changes we are seeing, such as those in theArctic, are consistent with large, slow natural cycles in the oceans. But many scientists believe there is a greater human component that is also impacting climate. The one overwhelming question is how significant greenhouse gases are against the backdrop of larger climate changes, and how ’self-correcting’ the Earth system will be to these changes. Scientists hope that improved climate and ocean models will provide clearer answers to such questions in the near future.

Rob Gutro | EurekAlert!
Further information:
http://www.gsfc.nasa.gov
http://www.gsfc.nasa.gov/topstory/2004/0625oceanbehavior.html

More articles from Earth Sciences:

nachricht NASA examines newly formed Tropical Depression 3W in 3-D
26.04.2017 | NASA/Goddard Space Flight Center

nachricht Early organic carbon got deep burial in mantle
25.04.2017 | Rice University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Link Discovered between Immune System, Brain Structure and Memory

26.04.2017 | Life Sciences

New survey hints at exotic origin for the Cold Spot

26.04.2017 | Physics and Astronomy

NASA examines newly formed Tropical Depression 3W in 3-D

26.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>