  The conjecture that helicity (or knottedness) is a fundamental conserved
quantity has a rich history in fluid mechanics, but the nature of this
conservation in the presence of dissipation has proven difficult to resolve.
Making use of recent advances, we create vortex knots and links in viscous
fluids and simulated superfluids and track their geometry through topology
changing reconnections. We find that the reassociation of vortex lines through
a reconnection enables the transfer of helicity from links and knots to helical
coils. This process is remarkably efficient, owing to the anti-parallel
orientation spontaneously adopted by the reconnecting vortices. Using a new
method for quantifying the spatial helicity spectrum, we find that the
reconnection process can be viewed as transferring helicity between scales,
rather than dissipating it. We also infer the presence of geometric
deformations which convert helical coils into even smaller scale twist, where
it may ultimately be dissipated. Our results suggest that helicity conservation
plays an important role in fluids and related fields, even in the presence of
dissipation.
