|
1-10-2004
The oceans are good thermometers for measuring the effects of climatic change . Studies have abounded in recent years on the effects of global warming on the ocean. Some people warn in apocalyptic terms that within a few decades' time the rising sea level will inundate coastal cities . Others go so far as to predict a new ice age, which would suddenly stop the polar ice caps from melting and return the rivers and seas to safe levels. Everyone has their theory. However, according to Azti scientist Ángel Borja, the only thing that is certain is that there is not enough data yet to go one way or the other.
Borja is a privileged witness to the evolution over the years of the waters in the Bay of Biscay . As a long-time researcher of the marine environment, Borja has taken part in countless projects. "It's not that we've conducted a special study on warming waters in the Bay of Biscay, but we have collected a lot of data which gives us a fairly good idea of what's going on."
One of these sets of data centres precisely on the evolution of water temperature over the years. The Azti researchers have the advantage of one of the oldest registers in the Bay of Biscay: the Donostia-San Sebastián Aquarium , where water temperatures have been monitored regularly since July 1946. Ocean temperature measurement stations are not as common as one might think, the closest one being at the Biarritz aquarium, where water temperatures have been monitored since 1960.
Therefore, the data collected at the Aquarium is very valuable for analysing temperature changes in the Bay of Biscay. The systematic study of data shows the existence of several alternating warming and cooling cycles in water temperatures. The warmest temperatures date from the early 1950s , when the water reached around 17.5ºC. This was the highest mean annual water temperature ever registered in San Sebastián. Warm temperatures continued, with occasional cooler interludes, until the seventies, when temperatures dropped suddenly and generally remained cooler until the nineties.
The temperature diagram shows a significant increase starting in 2002 . Since then temperatures have continued to rise, although they have not yet reached the levels registered in the 1950s and 60s. "If you look at the measurements taken since 1947, you can see a downward, not upward, trend. It is true, however, that we are lacking data dating from the previous decades, which would help give us a more representative picture, " added Borja.
Anchovies head north
Borja indicated the records for scientifically measured marine temperatures make one thing evident: the temperature of the ocean remained more or less consistent up until the latter part of the nineteenth century . "From that time until the present experts say that it has gone up two or three degrees," he added. We are beginning to see the effects of these changes on the marine environment. According to Borja, Azti's research shows a northerly shift in populations of species dependent on plankton . "Species that once thrived in the Bay of Biscay have moved toward Scotland and are being replaced by organisms that used to live in a more southerly habitat."
This is the case of the anchovy. In the past, its territory did not reach beyond the mouth of the Loire river in southern Brittany in France, but now they are beginning to be seen in the area of the English Channel. As Borja explained, "We've also begun to detect stable populations of Trigger fish, a species that once only lived in southern waters, and rarely entered the Bay of Biscay."
Scientists refer to the southernization of the Bay of Biscay , a warming trend which would be accompanied by other phenomena such as an increase in winter storms and periods of dead calm in summer. In Borja's opinion, there is no call for alarm, adding that "The sea isn't static. It's always been subject to change." |
Home
Marine Life
