Thermally modulated variable restrictors used in chromatography systems enable independent control of system pressure and linear velocity of a compressible mobile phase passing through a chromatographic column. The restrictors include a restrictor body having a fluidic channel with an inlet that receives the mobile phase from the column and an outlet through which the mobile phase leaves the fluidic channel. A restrictor tip, disposed adjacent the outlet of the fluidic channel, has an egress opening that is smaller than an internal diameter of the fluidic channel. A heating element, thermally coupled to a subsection of the fluidic channel between its inlet and outlet, heats the mobile phase passing through that subsection of the fluidic channel. The restriction produced by the restrictor tip in response to the heating of the mobile phase enables independent control of system pressure and linear velocity of the mobile phase within the column.