How did they achieve the crack in the ice scene?

In 'Eternal Sunshine of the Spotless Mind' there is an ice scene around the beginning of the film where the two main characters lay down on the ice. Screen left there is a unique and very beautiful 'crack' in the ice.

Bonus features on the DVD emphasize less special effects (mostly for the set).

So how did they get the crack in the ice? Was it artificially created? Did the production crew happen to search and then found it (aligning with Director's style)?

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Best Answer

It's real. I watched an interview with Gondry about this, but I can't find it anymore, so this is what I could find now:

From MentalFloss:

You can thank mother nature for that classic scene on the frozen lake. The script called for snow and ice, but Gondry was prepared to omit such details if the weather didn’t cooperate. Luckily, New York State had a fierce winter that year, and the lake froze over as hoped. Carrey and Winslet lying next to a crack in the ice would become one of the film’s iconic images.

From IndieWire:

Michel Gondry comments that critics read the crack in the ice as a symbol for the problems in Joel and Clementine's relationship, but Gondry claims he just positioned them actors near the crack so that the ice would not look fake (it's not).