Is there a way to separate 2 signals recorded on the same channel? I have 2 low frequency signals on the same line that look like this:



I would like to separate them so that I obtain the two signals that can be seen here:



The sampling is not perfectly intercalated, so it's not as simple as taking one point each in alternation.

I looked at ICA but my understanding is that I would need 2 recordings of the 2 mixed signals in order to separate them.

Any ideas?
You should look into a generalization of ICA called Independent Subspace Analysis (ISA). Practically it is Principal Component Analysis (PCA) followed by ICA.

There are threads on dsp.stackexchange that discuss this as well as github repos (and here) that provide various implementations.