Is there an equation of state for hypersaline water at very cold temperatures?

A friend of mine is looking to calculate changes in density of a hypersaline Antarctic lake from summer to winter. Apparently, this lake is about 10 times saltier than the ocean and often cools down to -17C at the bottom.

My own spontaneous answer was that I am not aware of such an equation of state, and that I doubt that there is a lot of empirical data in that property range. Plus from talking to Dead Sea researchers while working on double diffusion, I know that measuring salinities that are that high is not at all easy – the constancy of composition of sea water breaks down (at least in the Dead Sea) which has consequences for the measurement methods that can be used, and in any case CTDs aren’t calibrated for those salinities. But I am hoping that the collective wisdom of my readers will come up with a better answer.

So, dear readers. Do you know of an equation of state that applies to that range of properties, or do you have any other comments on the issue? Please leave a comment below or get in touch with me! That would a) really help my friend, and b) help satisfy my curiosity :-)