...final answer...
The sun/light source is coming from approx. 11 O'clock, the shadows fall along the same line, but, between the 'lake reflection' and elevation line, if there is a true reflection, then where the shoreline meets the reflective surface there should be a highlight or sun reflected area as well and in this case, there is. It is most probably also coated with the same type of ice or frost as the 'lake'. If it was a shadow, then the that shoreline would be in shadow also and not as highlighted as it is in the photo. So, I'll say that it is a reflection (of frozen CO2?!). :)
Marcia
*Ducking.