I don't need to tell you that the ground in the north regions of our planet contains a lot of ice. With the beginning of spring season i.e. with the onset of positive temperatures, the ice within the ground starts melting. And as you also probably know, when the ice melts, it looses about 10% of its volume. That's why the ground surface can go down during this period. This settling down is known as the surface subsidence. It can go down as deep as a few cm per season. The process is alternating by migration of melted water within the soil. Therefore, the surface subsidence is directly dependent on the ice content in the ground.

 

What you also might already know is that the ice within the ground contains a lot of carbon dioxide and methane. When the ice melts, naturally all gas is released to the atmosphere through the ground. That's why it's extremely important to know the ice content within the soil.

 

It can sound rather unbelievable, but one can use remote sensing observation to measure the relative surface subsidence. More detailed explanation will come within the next posts. For now, let's just imagine that we have such information. Of course, we need some in-situ measurements for the satellite data validation.

 

That's why we will go to the Lena Delta and will install there ultrasonic sensors, which will measure the distance between the device and the ground during the whole thawing season. Having such dataset, we can easily obtain the relative subsidence.