Scientists explained how the accelerating melting of ice in the Arctic ocean affect the atmospheric circulation in the Pacific ocean, resulting in an increase in the frequency of extreme climatic phenomena, including El niño. The results of a study published in the journal Proceedings of the National Academy of Sciences.
Global warming is one of the most important factors of global climate change, and it occurs irregularly. For example, because of a system of positive feedback of temperature in the Arctic is growing much faster than in other regions of the world. The increase in the concentration of carbon dioxide leads to the greenhouse effect and rising temperatures. This, in turn, accelerates the melting of the ice cover of the Arctic ocean, and the resulting albedo (reflectivity) of the surface. While white ice reflects 50 to 80 per cent of short-wave solar radiation, open water absorbs 93 percent, is heated and itself heats the lower layers of the Arctic air. The same effect is the melting of the snow cover. “Arctic amplification” of global warming amounted to about a quarter of the total increase in global temperature in the period 1979-2011 years.
Heated air masses low Equatorial latitudes rise in the upper troposphere and flow to the cold poles, representing one of the basic mechanisms of global circulation of the atmosphere. The difference in the rate of the current warming leads to a decrease in the total temperature gradient between the equator and the pole and slows down the flow of air from low to high latitudes. The speed reduction of the flow causes the increase of sinuosity of the polar fronts. On them there are large and stable meanders, deeply penetrating into the temperate latitudes. Climate scientists Charles kennel (Charles F. Kennel) and Elena yulaeva (Elena Yulaeva) from the University of California in San Diego believe that this process is associated with extremely cold winter of 2009-2010 in North America, heat wave in Moscow and floods in Pakistan in summer 2010.
They argue that a “decade of extreme weather events” in the beginning of the XXI century, confirms the new trend in decadal climate cycles, and the launch of these changes have occurred in the last years of the last century and concerns not only of the Arctic and adjacent temperate and climatic phenomena in the low latitudes of the planet. In particular, changing the mechanism of the trade winds — winds compass points East, steadily blowing from the tropics towards the equator, and the regularity of the manifestations of El niño.
The nature of El niño is that in the Pacific ocean builds up a kind of imbalance in the water level — Equatorial currents are driven surface layer to the West coast. The water level off the coast of Indonesia may on tens of centimetres to exceed the Eastern part of the ocean. Simultaneously, the observed temperature difference: in the West, water is warmed in the East strongly influenced by the cold Peruvian current. During El niño warm tropical waters from the West spread to large areas, causing the increase in temperatures and widespread negative effects on the tropical coast of South America.
A new study dedicated to finding and explaining connections between the changing ice conditions in the Arctic ocean, the strength and direction of the trade winds, the behavior of El niño in the tropical zone, and changes of atmospheric circulation in the North Pacific ocean.
Climate scientists have used advanced climate models CMIP5 (5th Coupled model Intercomparison Project), which laid the increase in the intensity of the trade winds, enhancing the seasonal loss of sea ice and a temporary slowdown of global temperatures in the second decade of the XXI century. Base for the study consists of monthly data on the state of the atmosphere and surface waters National center for environmental prediction (NCEP) and National center for atmospheric research (towards) and daily data of the European Centre for medium-range weather forecasts (ECMWF). For the study, the authors chose two time periods: 1980-1998 and 1999-2015. In 1997-1998 was the biggest tool in the history of the phenomenon El niño and the 1998 adopted by the authors for the transition year when there was a qualitative shift in the climate of the Equatorial Pacific ocean.
In the study managed to establish the following sequence of the influence of Arctic amplification on the climate of the Pacific ocean:
- The maximum area of open water in the Arctic ocean observed in September, at the end of the season of melting ice. During a one-month period in early autumn, is developing vertical convection.
- Episode large-scale vertical convection gives rise to planetary wave and high frequency wave-Zug in the upper troposphere. From adjacent to the Pacific Arctic sector, the wave packet spreads to the South, and reduced the temperature gradient between the equator and the pole contributes to this. In December he meets with the zone of convergence of air masses located between the tropics.
- The result of this interaction creates favorable conditions for the occurrence of El niño. A trigger is a temporary shift of the trade winds in the Central and Eastern Pacific ocean. Under the influence of waves from the Arctic winds change direction from East to West Rumba, and in the Equatorial region is formed by a kind of Equatorial dipole.
- In the process of interaction of the waves and the Arctic zone of convergence occurs the reflected wave, which rolled back to February and reaches the zone of low pressure in the North Pacific (Aleutian depression). This area is responsible for the formation of the climate of the North Pacific ocean. It is here that originate the cyclones and the jet stream, which largely determines the weather of North America.
- The situation in the Aleutian depression changes, cyclonic activity weakens.
The steps are successively repeated each year, but their intensity and spatial structure vary greatly depending on factors such as overcast, stormy atmosphere, the water vapor content in the atmosphere etc. the Authors also point to certain limitations in the use of research results. The first relates to the fragmentation of insights for shorter periods with the loss of statistical precision. The second is described as the need to take all the assumptions of the model. The reliability of the results of each step of the concept depends on the quality of the data on all other stages. The currently available level of accuracy of the climate simulation shows a direct or indirect connection between ice conditions in the Arctic and the circulation of the atmosphere and surface waters of the Pacific ocean indicates an increase in the frequency of El niño. Perhaps these results will help to understand not only the current climate change and explain global climate changes after the melting of ice sheets in the Northern hemisphere at the end of the last ice age.
To learn more about climate change from our material on the myths surrounding global warming “Sacred stick” and parsing the news about the consequences of a warming Arctic “In the Arctic ocean found a “heat bomb”.