Your stock fan curve is too mild. 45% isn't nearly enough to keep even a stock or mildly OC'd 7970 cool at full load. I used a much more aggressive fan curve and my GPU still hit 84c when mining @ 1150 core, with 100% fan speed (!). Just replacing TIM got it to 79.
This is what my fan profile in Trixx looked like when I was single card and still used it. Once it hit 70c it quickly ramped, reaching 100% fan by 75c. Note that the stock fan is LOUD at full speed.
No way to know if fan profile has been changed unless you manually edit the BIOS for it, your warranty will be fine. Using software to change fan profiles and speed is temporary and untraceable...reseating the TIM though will voide the warranty, which is why I first recommended you to check every screw for stickers that block them or will tear if you remove the stock cooler. There were none on my reference 7970.