No way to remove avatar and use Gravatar

Summary: Once a user uploads an avatar, they are unable to remove it, to use a gravatar instead.

Initially, when I joined BitBucket, I uploaded an image as my avatar. Later on, I discovered what gravatars were, and now would like to use my gravatar for BitBucket. How do I do this? There seems to be no way to switch to a gravatar.

If this is not yet possible, can someone please manually reset my avatar? It's seriously bugging me! Thanks.