Looks like you have some DC offset happening. That's when some DC current gets mixed in with the AC audio signal and causes the zero point on your waveform to be offset upwards by a fraction of a volt. It makes sense it's happening on your turntable since there are DC voltages floating around in there.
Audition has a tool that corrects DC Offset. On CS6 for some reason it's tucked away on the Effects/Amplitude and Compression/Normalise menu. Just put a tick in the DC Offset Correction box (and untick the Normalise box if you don't want to change your levels) and it should fix it for you.
Bob's right, but I have to tell you that this is a huge shift - I don't ever recall seeing one that big before! The first thing you need to do before mucking about with the turntable though is to unplug the input to the interface from the phonograph (is it really a phonograph? - see below) and see if the shift is still there when you record, even though it will be silence you are recording. If it is, then don't bother with adjustments - just purchase a new interface, because that's where your fault is, and you won't be able to fix it.
Why do you need a new one when Audition can potentially fix this, you might ask? Well, a 12dB offset is actually going to limit the maximum output you can get from the device, quite considerably - so you are losing headroom. This means that a heavily modulated recording is likely to run out of headroom, and clip. Not good. It indicates that the internal electronics really aren't up to much.
This is a phonograph. Is it actually one of these you are using?