The phrase "tundra fires" refers to fires occurring in the tundra region, which is a cold, treeless ecosystem found in the Arctic and high mountain areas. It means that there are fires burning in this icy environment. Full definition
This ongoing ice retreat is spawning a variety of changes in the Arctic ecosystem, from increased parasites in caribou herds to a growth in annual tundra fires in Alaska, according to the assessment in Science last week, which reviews prior data. (scientificamerican.com)
He wondered what impact soot from the fires — and others raging closer to the Arctic, including the largest tundra fire in history — might have on the ice sheets. (ensia.com)
The MBL Ecosystem Center is involved with the Arctic Long Term Ecological Research (LTER) site on Alaska's North Slope whose website has a dramatic photo and report of the largest tundra fire ever recorded on the North Slope. (dotearth.blogs.nytimes.com)