GPS system time is closely aligned with International Atomic Time and coordinated universal time scales, differing only by a fixed integer number of leap seconds.
The alignment of GPS time with International Atomic Time (TAI) is a fundamental design feature of the GPS system (maintaining a constant offset of 19 leap seconds, plus a small sub-microsecond synchronization error). This is a well-established technical fact of global navigation satellite systems and common knowledge within geodesy and metrology, requiring no specific single study citation to verify.