How do I stop GPU temp fluctuations in Death Stranding 2?

Night scenes in Death Stranding 2 had my GPU temp bouncing between 65℃ and 72℃, causing light flickering. I tried increasing the water cooling fan speed, which cooled it down but made the noise unbearable. I used GamePP Hardware Sensor Monitor and saw the pump speed jittering between 2500-3000 RPM. I locked the pump speed to 2800 RPM, which eliminated the abnormal noise. 3DMark confirmed GPU temperature converging to 62-65℃. Fan speed stayed at 1400-1600 RPM. The lighting quality is now stable, and I can switch between scenes without visual artifacts.