so last week when it was negative degrees i noticed when my car was COLD the steering was stiff and the power steering would wine when i turned left or right but after it warmed up the whine went away and it has been fine since for about 7-10 days. Today i went to start it and it was in 20's so it was warmer but the whine was there and has been all day. I thought it may have been fluid but it was almost to the top and i topped it off anyway but sound still there. I have a leak somewhere where im losing power steering fluid but its not at an alarming rate.

any ideas of why it would make that whining sound and sometimes when parked it will be very stiff and difficult to turn wheel. BTW vehicle is a 2000 2.8 30v.