Not sure if this is intentional, but it looks weird so I figured it'd be worth a report. I couldn't find any other reports mentioning this, so apologies if this is already known.

Under frozen ocean biomes, large pillars of packed ice generate deep into caves before being abruptly cut off around y=0.

The world seed I found this on was -769589292261774749, a frozen ocean can be found very close to the world's center.