Apparently yes. As sea water freezes, salt is excluded from the resulting solid and remains in the water. If you deep-freeze a glass of salt water, the ice forms as salt-free. The remaining water gets saltier until, at -21c, the saturated solution freezes while the remaining salt crystallizes and remains separate from the ice.
www.worsleyschool.net/science/files/saltandfreezing/ofwater. www.fwr.org/desal.pdf
www.worsleyschool.net/science/files/saltandfreezing/ofwater. www.fwr.org/desal.pdf