Why did "Glaciologist Princess Elsa" have to leave the glacier because it was too warm?
I'm the scientist in the article; someone just saw this question and emailed me about it! (I'm on as a guest here since I don't have an account, so you'll hopefully trust it's me. Even if you don't believe it's me, I hope the answer will still be useful.)

It's entirely a safety issue. The best way to get around on the surface of the glaciers in this area is to cross-country ski on the snowy surface. If that snow gets thin or melts away completely, it's very risky to be on the glacier because the crevasses in the ice below become exposed. We're all trained in crevasse rescue, but we'd rather no one fall in the first place! My field site normally has ample snow thickness at the time I was there, but an early and extreme heat wave in the area put the whole icefield about a month ahead in the melt season. We did our best getting as much data as possible, but ultimately safety comes first and we had to get out of there.