  One of the most prominent features of quantum entanglement is its
invariability under local unitary transformations, which implies the degree of
entanglement remains constant during free-space propagation. While this is true
for quantum and classically--entangled modes, here we demonstrate a novel type
of classically-entangled modes that experience an entanglement decay upon
free-space propagation. We show this by numerical simulations and corroborate
experimentally. Our results evinces novel properties of classically-entangled
modes, which pave the way to novel applications.
