Dating and melting
“We have these things called thaw depth probes, which is basically just a T-bar, a steel rod that's a centimeter in diameter and 1.5 meters or so long,” Holmes says. “It's like pushing a knife through warm butter or something, and then you hit the bottom of the tray, and boom” — there’s your permafrost.Eventually, if you dig deep enough, the permafrost again thaws due to heat from the Earth’s core.A week earlier, Holmes and his students had set up temperature sensors in the soil near their encampment. The top few inches (up to a few feet) of the permafrost is what’s known as the “active layer.” This topsoil does thaw with yearly seasonal changes, and is home to a thriving ecosystem.So how do scientists know there’s permafrost underneath it?
Permafrost is a layer of frozen soil that covers 25 percent of the Northern Hemisphere.
“Half the volume of permafrost may be frozen water,” Holmes says. The water may head downhill or the water has a lower volume than is ice, so the ground just slumps and kind of falls apart.” (The New York Times has a great new interactive showing how much permafrost in the Alaska may inevitably melt.) Longyearbyen, a settlement in Svalbard, Norway, is home to a seed vault intended to protect plant genetic diversity amid a changing climate.
Its Arctic location may not be as secure as once thought due to rising temperatures and melting permafrost.
Scientists don’t know how much of this mercury could be released, or when, the Washington Post explains.
But they do know this: Continued melting will make it more likely for the mercury to be released, pollute the ocean, and accumulate in the food chain.