Following are acf and pacf plots of a monthly data series:

![enter image description here][1]

The persistence of high values in acf plot probably represent a long term positive trend. The question is if this represent seasonal variation?

I tried to see different sites on this topic but I am not sure if these plots show seasonality. 

http://stats.stackexchange.com/questions/108983/acf-and-pacf-plot-analysis

http://stats.stackexchange.com/questions/56824/help-interpreting-acf-and-pacf-plots

http://stats.stackexchange.com/questions/49571/help-understanding-the-following-picture-of-acf

http://stats.stackexchange.com/questions/59694/autocorrelation-and-partial-autocorrelation-interpretation


  [1]: https://i.sstatic.net/wh6s3.png