Droughts and ecosystems are determined by the interaction of two climate phenomena

Iberian Peninsula [image credit: NASA]

Study of long-term oceanic influences on a regional climate has turned up some interesting results, as Phys.org explains.

What is causing the droughts that the Iberian Peninsula regularly endures? Why are the winters sometimes mild and rainy and other times cold and dry or cold and damp? Is climate change of anthropogenic origin exerting an influence on these processes? How are these cycles affecting the productivity of terrestrial ecosystems?

And finally, can these cycles be predicted and the economy thus adjusted to them?

The work, published this week in Nature Communications, was led by the University of Alcal de Henares. It was conducted in collaboration with the UPV/EHU, the University of Geneva and the University of Castilla-La Mancha and offers important keys for answering some of these questions.

The North Atlantic Oscillation (NAO) is a large-scale fluctuation in the atmospheric mass located between the area of subtropical high pressures and the low polar pressure in the North Atlantic basin, and is largely responsible for the periods of drought on the European continent.

Previous studies show that the NAO has a great potential effect on various aspects, from carbon fixing and tree growth to fruit production and forestry pest cycles. However, the connection between long-term forestry productivity and the NAO presented some inconsistencies, such as periods in which climate cycles did not correspond to what was expected in terms of the NAO value.

In their work the researchers in fact show that these inconsistencies may be originated by periodical anomalies in the surface temperatures of the Atlantic Ocean, known as the Atlantic Multi-decadal Oscillation (AMO).

They are ocean phenomena that appear in the North Atlantic and by which ocean temperatures follow a cycle that takes about 70 years in total. These temperature changes in the ocean affect the atmosphere not immediately but with some delay.

Continued here.

The researchers conclude:
So the results of the work show that the AMO+ NAO+ and AMO- NAO- phases exert a high degree of control on forestry productivity owing to the reduction in rainfall and wintertime temperatures. The NAO is like a key that opens up and closes off the entry of areas of low pressure. What is needed, however, is the control of the AMO (linked to the temperature of the Atlantic at extratropical latitudes and the formation of areas of low pressure), which eventually determines the temperature and humidity of the air that reaches the Peninsula.

via Tallbloke’s Talkshop

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December 29, 2017 at 05:15AM

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