<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def is_circumpolar(self, var):
 """ Test if a variable is on a circumpolar grid Parameters %(CFDecoder.is_triangular.parameters)s Returns ------- %(CFDecoder.is_triangular.returns)s"""

        xcoord = self.get_x(var)
        return xcoord is not None and xcoord.ndim == 2