  We present here observational evidence that the snowline plays a significant
role in the formation and evolution of gas giant planets. When considering the
population of observed exoplanets, we find a boundary in mass-semimajor axis
space that suggests planets are preferentially found beyond the snowline prior
to undergoing gap-opening inward migration and associated gas accretion. This
is consistent with theoretical models suggesting that sudden changes in opacity
-- as would occur at the snowline -- can influence core migration. Furthermore,
population synthesis modelling suggests that this boundary implies that gas
giant planets accrete ~ 70 % of the inward flowing gas, allowing ~ 30$ %
through to the inner disc. This is qualitatively consistent with observations
of transition discs suggesting the presence of inner holes, despite there being
ongoing gas accretion.
