Get yourself some Belt Conditioner sold at most auto part stores. Start your MO and open the hood. Look on the passenger front side of the engine and you should see the drive belt. Liberally squirt with the Belt Conditioner and noise should fade away. Hope this helps.
If it's a belt whine, it will be most audible on the passenger side next to the strut. An 09 is six years old, so it might be time to replace the belts, too.
If it's an alternator bearing or some such thing, the best way to find it is with an auto stethoscope - or by putting the tip of a long screwdriver against the engine in various placed (DON'T get caught in moving parts, including the radiator fan) and pressing the other end against your ear. That helps to localize it.
Unfortunately most of the rotating accessory parts like alternator, PS pump and AC compressor are down low enough that they're hard to reach.
I bet it is the power steering fluid. If you haven't done a flush, def want to the next service. I had to do mine at 75k and it cured the whining noise for me and idle and low speeds.
going to add on here cause I mucked up on something with the power steering. Short story I added a drop of DOT 3 to the power steering reservoir
that looked a bit low. Maybe a table spoon worth. Critical error? Never have done a flush on it, so I guess it deserves it now. I see some sort of TSB on the reservoir I did not know about. Had no issues steering or noise wise. Never to make that mistake again. Thought for sure one I'd goof on the coolant and washer fillups one day - that is the worst placement , right together.
Now that I finally figured out how to share videos... I have a strange hum, and now a whine on my 2017.5, week and a half old Murano SL
Love some comments on whether this is normal and I'm just paranoid, or is this something I should have looked at.
2 short vids which demonstrate both noises https://www.dropbox.com/sh/rs1jjoooqq6qqlb/AACUQWLEGw4HSIOzdDBbYyzVa?dl=0