Ale fermentation comuplete, why is it bubbling again?

[ForerunnerBrewer]

Yesterday, 3 weeks after pitch, I put my 6 gal carboy with IPA in the kegerator. I have the temperature set at 48˚ and now the airlock is bubbling like it does 36 hours after pitching yeast.

I intended to turn the temp down to cold crash after I had a couple beers this weekend.

What's happening? Will this further attenuate and make this taste a little like a lager?

FYI: The yeast is 3rd gen California Ale V with 73% attenuation

Thanks everyone!

 

[ForerunnerBrewer]

It may have been because the cold air outside of the clear plastic carboy was denser than what was inside? It kept going though... Hmm...