What's this line over Lake Baikal? (Score 1)

Looked up lake Baikal (a very large lake in Siberia, 445m above sea-level) after remembering I had a poster on my wall for years showing the surface temperature of the lake from ATSR satellite imagery.. wondered what it looked like in more realistic colour.. but what is this huge line that crosses it?

http://maps.google.co.uk/maps?ll=53.789063,109.610 596&spn=2.120361,2.730103&t=k&hl=en