Based on the recorded changes in the area—decreasing runoff, increasing temperature, and decreasing precipitation—the most likely result would be:
A. Permafrost thawing
Increasing temperatures can lead to the thawing of permafrost, especially if the region is already experiencing changes in precipitation and runoff. The combination of these factors aligns most closely with the phenomenon of permafrost thawing. The other options, such as rivers flooding and sea levels increasing, do not fit as well with the given changes in the area.