Following are acf and pacf plots of a monthly data series. The second plot is acf with ci.type='ma':

![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


Edit: following is the graph for lag upto 60: 

![enter image description here][2]


  [1]: https://i.sstatic.net/o0ujY.png
  [2]: https://i.sstatic.net/UMWx3.png