What effect does altitude have on indicated airspeed in relation to groundspeed?

Indicated airspeed is the speed displayed on the aircraft's airspeed indicator, which is a function of dynamic pressure and is subject to the characteristics of the atmosphere, including altitude. As altitude increases, the air density decreases, which affects how the airspeed indicator functions. Specifically, for an aircraft flying at a constant true airspeed (the actual speed of the aircraft relative to the surrounding air), the indicated airspeed will decrease because the lower air density results in a lower dynamic pressure acting on the sensors of the airspeed indicator.

Meanwhile, groundspeed is the speed of the aircraft relative to the ground. As altitude increases, if the same flight path is maintained, and regardless of the lower indicated airspeed, the aircraft may still cover ground faster due to the jet stream or other wind factors. Therefore, while indicated airspeed decreases, groundspeed may increase due to these external aerodynamic conditions, hence the correct relationship observed.

This is why the understanding of indicated airspeed versus groundspeed is significant in aviation, especially at varying altitudes where wind patterns can critically affect ground travel.