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

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.

ACF and PACF plot analysis

Help interpreting ACF- and PACF-plots

Understanding the blue dotted lines in an ACF from R

Autocorrelation and partial autocorrelation interpretation