After 15,000 years, it's waking up

Where is the material that was dug out to form the tunnel? Isn't the tunnel contributing to the melting? ie. If the tunnel was not there,  there'd by no sublimation in the tunnel path. If anything was released from the permafrost,  it would need to multiply before we'd see it's effects,  we wouldn't know until it actually leaves a footprint/ trail behind.