Following are acf and pacf plots of a monthly data series. The second plot is acf with ci.type='ma':
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.
Help interpreting ACF- and PACF-plots
Understanding the blue dotted lines in an ACF from R
Autocorrelation and partial autocorrelation interpretation
Edit: following is the graph for lag upto 60:
Following are plots of diff(my_series):
And upto lag 60: