Russian scientists modeled mechanisms of sharp changes of the climate in the course of studies, carried out in the Atlantic Ocean. Natalya Bykova, a journalist, told about these works on the pages of an electronic version of Science and Technologies of Russia--STRF.ru.

Staff members of the RAS Institute of Oceanology named after P. Shirshov studied the so-called intermediate waters in order to understand how the World Ocean is changing in the course of time and how these transformations can tell on the global climate. They are regarded as an indicator of the intensity of an inter-ocean global conveyor--a flow, forming due to diversity of properties and levels of the Pacific and Atlantic oceans. This flow is slowly running on the water surface from the north of the Pacific Ocean to the north of the Atlantic, where it becomes cool, goes down to the depth and starts moving in the opposite direction. This process depends on what is taking place in intermediate depths.

"In general it is impossible to measure,--explains the supervisor of studies, head of the laboratory of interaction between the ocean and atmosphere and monitoring of climatic changes, RAS Corresponding Member Sergei Gulyov--I cannot say that I measured the speed of an inter-ocean conveyor and that it runs at a speed of 2 cm per second. It is impossible to find a place in the ocean, where such measurements can be conducted. In reality, a lot of factors club together, which as a result bring about an inter-ocean global circulation. However, its intensity is rather well characterized by the speed of formation of intermediate waters in the north of the Atlantic, which can be registered."

From 1997, the Institute of Oceanology annually organizes oceanic expeditions for detailed measurements of water parameters in the area of 60 °N between Greenland and British Isles. Though it is well-known to science that the main control lever of the inter-ocean conveyor is in the northern part of the subpolar Atlantic--it is here that all waters flow together, then go down to enormous depths,-- some details of the process itself remain unclear. On the one side, it is clear that this flow can "go down" only due to thickening, which takes place, if water becomes cool or "too salty". On the other hand--intensity of interaction of the ocean and atmosphere, on which depends the speed of this cooling and growth of salinity, in a greater extent is determined by atmospheric processes, much faster as compared with those taking place in the ocean.

From board the research vessel Academician Ioffe, staff members of Sergei Gulyov's laboratory every year in the course of the whole month are measuring temperature and salinity of intermediate waters as well as intensity of warmth flows on the border of the ocean-atmosphere.

Schematic image of an inter-ocean global conveyor--a flow, forming due to the diversity of properties and levels of the Pacific and Atlantic oceans.

Then by means of physico-mathematical models they estimate how transport of water and warmth between the Atlantic Ocean and the Arctic--a region, from where, if we believe in one of the versions of possible climatic changes, as a result of melting of glaciers the planet will face warming, the consequences of which are difficult to forecast. The process can take tens of years or a century, though for human civilization this means rapid changes.

Specialists have established: in the course of past two decades there took place intensive warming and greater salinity of surface waters. Besides, warming, resulting in a decrease of thickness of waters, was not compensated by greater salinity--it, on the contrary, causes their "becoming heavier". That's why there happened significant deceleration of the inter-ocean conveyor. Warm water began getting into the Arctic basin in greater quantities, leading along with other factors to melting of polar ice, whose area decreased almost by 30 percent during this time.

Besides, researchers found a new source of deep convection, determining movement to the depth of surface waters, formation of intermediate waters and return flow. If before it was believed that such main source was Sea of Labrador, now it has become clear: similar processes are taking place to the east of Greenland--in the Sea of Irminger. However, in order to forecast a deep convention, both sources should be taken into consideration and, first of all, interaction between them.

By the way, in order to describe in detail all these phenomena, it is not sufficient to know what is "happening" in the ocean. No less important is an accurate assessment of energy flows on the border of the ocean and atmosphere. Staff members of the Institute of Oceanology worked out new methods of computation of such flows and for the first time made a model of their intensity. It has turned out that those of them that are directed to the atmosphere cool down the ocean, leading to convective processes, only in relatively short periods of time--several years, while in long periods (more than 10-15 years) temperatures determine long-term flow changes. Thus, the ocean's role in climate changes in double: it acts as a passive factor in short periods of time, but becomes active in long periods.

In order to understand these mechanisms, scientists made a model of oceanic circulation with spatial resolution in several tens of kilometers. It allows to imagine a vibratory process, in the course of which the ocean conveyor now is weakening, now is strengthening. Now these notions must be united with existing climate models, which will help to take into consideration the processes, observed by specialists, in the description of expected changes.

At present, on the basis of the obtained data, we can say that the ocean conveyor has affected the climate, as a result of which trajectories of cyclones over the European continent have shifted and there has essentially changed the structure of precipitation. Though the number of days with precipitation has remained as before, there occurs their regrouping in a series of rather long humid and dry periods. As a result, more intensive become extremely long precipitation, resulting in floods, and droughts, connected with long thermal waves, causing forest fires.

N. Bykova, Russian Scientists Found New Interrelations of the Ocean and Climate.--Electronic magazine "Science and Technologies of Russia -- STRF.ru", July 17, 2012

Illustrations from the site of the Institute of Oceanology named after P. Shirshov

Prepared by Sergei MAKAROV