These results are in accordance with those of the first group of scientists to study this question, who stated that a negative NAO implied a weaker ocean current (and vice versa). There were also similarities to the third group, that the PhD student had referenced in his bibliography, which for its part maintained that a positive NAO would draw the Gulf Stream more northward (and the contrary).

“However, we have to put things into perspective, he indicates. The intensity index is based only on surface data.  I have not worked in three dimensions yet. That will be one of the next stages. I am going to try to reconstruct an intensity index by using the lower layers to attempt to determine what the quantity of warm water is compared to the quantity of cold water as well as the speed of the Gulf Stream at different depths, in order to quantify the state of flux of water making up the GS. This would be a new intensity index for the Gulf Stream, in 3D this time.”  That should keep him busy for a while!

Of interest for fishing?

While awaiting these improvements, the results could be used to improve predictions regarding the intensity and location of the Gulf Stream. “Since the NAO and GS location time lag is one year, if we knew the current value of the NAO, we could try to predict the location of the GS in one year. The question remains open as to what that could achieve but it is not devoid of interest.” The PhD student thinks that fishermen might be interested in predicting the behaviour of these relatively warm waters. Just as long term meteorological forecasts might be found to improve. “The Western European climate system is mainly influenced by factors from the West. If we understand these better we could have a better understanding of our climate”.

As for the theories bandying around about the possibility of the Gulf Stream stopping in the future, leading to the temperatures in the West of Europe falling, Sylvain Watelet dismisses them totally. “It is very unlikely that the GS will stop altogether. Having said that we can observe a decrease in the intensity of the current since the early 2000s, though not significant, in parallel with the evolution of the NAO. Some people think that this is due to global warming but I think it is because the NAO is also decreasing. We must keep in mind that 10 years is very short as a reference period. Ideally, you should be working on a minimum of 30 years. My long-term analysis shows that there have already been troughs in the past, but they did not last and we saw them followed by increases. Incidentally between 1960 and 2012, the intensity of the Gulf Stream saw a slight increase, this time significant.” We’ll see in a few decades if it was just a temporary decrease or the start of a more radical change...