Retreating Yukon glacier makes river disappear

In this case, the glacier has receded a bit, so the melt from it no longer split north and south. Instead, it all flows south which is downhill, thus nothing going north to Kluane Lake.

A lot will depend on the outflow area at the north end of the lake, at the Kluane River. Plus there's more evaporation in this warmer weather we are having now.