  We report on a theoretical investigation of artificial spin-ice dipolar
arrays, using a nanoisland geometry adopted from recent experiments [A. Farhan
\textit{et al.}, Nature Phys.\ \textbf{9} (2013) 375]. The number of thermal
magnetic string excitations in the square lattice is drastically increased by a
vertical displacement of rows and columns. We find large increments especially
for low temperatures and for string excitations with quasi-monopoles of charges
$\pm 4$. By kinetic Monte Carlo simulations we address the thermal stability of
such excitations, thereby providing time scales for their experimental
observation.

Mesoscale and Nanoscale Physics;Materials Science