The Gallocanta lagoon is a beautiful Aragonese natural area where many migratory birds stop there to rest (more than 260 species of birds have been catalogued). It is the largest natural lagoon in the Iberian Peninsula and the largest saltwater lagoon in Western Europe, stretching between the provinces of Zaragoza and Teruel. Located at just over 1,000 m altitude, it is a rainfed lagoon that depends largely on the autumn and spring rains to sustain itself in the hot summer months.
But we are not going to talk here about its birds or its resources, but about something much more amazing. Because, could anyone imagine that the variations in the water level of the Gallocanta lagoon could be related to the famous El Niño phenomenon ? Let us remember that El Niño begins in the tropical Pacific Ocean , near Australia and Indonesia, when an anomaly appears in the surface temperature of the sea that ends up causing an alteration in atmospheric conditions in very distant areas. It is a cyclical natural phenomenon, although not periodic, which occurs every 3 or 7 years.
As is often the case in science, the ecologists at the University of Barcelona who demonstrated it were not looking for that type of relationship. In fact, they were studying the relationship between changes in the level of the lagoon, the rain that fell in a nearby town called Daroca, and its relationship with the climatology of the area.
Then it occurred to them that perhaps the interannual variations in the level of the lagoon could be related to some non-local phenomenon, which was something more general. Then the Spanish ecologists realized that the year after the very strong Niño of 1982 the lagoon dried up. Coincidence? It’s possible.
However, this happened again some time later. Too many coincidences. The scientists began to look for long series of measurements of the El Niño phenomenon and found an excellent fit between the level of the lagoon, the precipitations in Daroca and the El Niño index , a magnitude that serves to quantify the phenomenon and that is calculated as the difference in atmospheric pressure between two cities, Tahiti -the largest island in French Polynesia- and the Australian city of Darwin.
One might wonder if this El Niño effect is exclusive to Gallocanta or extends to other regions. The ecologists then decided to look for precipitation data spread throughout the peninsula, including North Africa. They found that for the south and east of the Iberian Peninsula there is a very good relationship between precipitation and the El Niño index . In fact, 25% of the interannual variation in the 100 years collected could be explained by the variation of the El Niño index. That a quarter of the rainfall variability can be explained by a single external conditioning factor means a lot in climatology.
Is it or isn’t it incredible that from the study of an ecosystem like that of the Gallocanta lagoon we can infer results about the global behavior of the atmosphere?
Comín, F. A., Rodó, X. (2003) Global Climate: Current Research and Uncertainties in the Climate System, Springer