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

Posted: December 29, 2017 by oldbrew in atmosphere, climate, Cycles, Natural Variation, Ocean dynamics, research

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.

  1. Paul Vaughan says:

    “[…] can these cycles be predicted […]?”

    Water circulates and changes phases. The uniformity assumption is extremely devilish.
    Discussion will remain sabotaged until misguided premise is corrected, but a decade has passed and it’s clear the major western fault wants the question misframed permanently. Of course that’s fatal and the focus switches to management of a personnel problem since discussion absolutely cannot and will not advance with current staff (notably on the US blogs).

  2. oldbrew says:

    There’s theoretical prediction, then there’s waiting for certain signals before predicting.

  3. Seems like a similar effect between the SOI and PDO. I think it is a +ive (La Nina) and +ive which results in flooding in Eastern Australia and -ive (El Nino) and -ive which results in droughts. There has been a paper on that. -Prof Stewart Franks Uni of Newcastle NSW “multi-decal climate variablilty : Flood and drought -New South Wales”

  4. Sorry, reading the article indicates I had it a bit wrong. It is the IPO (Inter-decal Pacific Oscillation) but that trends similar to PDO (which is more northern hemisphere). Also, I had the sign wrong – floods tend to be bad when SOI is positive (above +10 for some months indicating a La Nina period) and the IPO is negative (less than 0.5 for some period- this occurred in the early 1970’s and there were bad floods in Brisbane in 1974 and 2011 also 1893
    PS in 1970 I saw the Niagara falls completely frozen with no water movement. I saw a news item today that the Niagara Falls were half frozen which is early in the season -maybe they will freeze completely in January. In the 1970’s there were so-called climate scientists predicting a coming ice-age.With the low sun spot cycle similar to cycle 5 in the little ice age maybe those predictions were one ENSO cycle out.