Progression of Spring Thaw
- What is the location that the map is focused on? We are looking at the Arctic in the northern hemisphere
- What two dates are being compared? April 1st, 2015 and April 13, 2015
- What variable is being analyzed? The state of H2O in the soil changing from solid to liquid during spring thawing
- The two maps are 12 days apart. What do you predict would happen in 12 more days? Why? There would be more thawing, but less because at the high latitudes as there is less solar insolation. Why? Even though the hours of daylight increases as we move from winter to spring and the illumination of solar energy increases at the poles, the bright white snow and sea ice reflect a significant portion of the incoming light, reducing the potential for solar heating.
- When the surface changes from blue to red, what happens to the environment of that area? Rapid warming releases liquid water. As liquid water becomes more readily available, plant and animal activity are energized. The land greens up, and animals return to graze.
- Pick a country on the map. Does it follow the general trend? What evidence can be used in your argument? Answers can vary. The progression of melt northward across Alaska is evident, along with changes across the boreal forests of northern Canada. Large areas of Russia also changed from frozen to thawed.
The radar measurements made by NASA's Soil Moisture Active Passive (SMAP) observatory are sensitive to whether land surfaces are frozen or thawed. As liquid water freezes in soil, the water molecules become bound in a crystalline lattice, which changes how the incoming radar energy from SMAP interacts with Earth's surface, compared to soil containing freely oriented liquid water molecules.
Shades of red indicate regions where the landscape is thawed; shades of blue correspond to frozen areas. The transition from frozen to thawed conditions is evident over extensive regions between the two images, acquired April 1 and April 13. For instance, the progression of melt northward across Alaska is evident, along with changes across the boreal forests of northern Canada. Large areas of Russia also changed from frozen to thawed. The SMAP radar measurements indicate frozen soil conditions for some regions near the southern edge of the maps (in the United States and Eurasia), even though these regions are now thawed. This is a result of the influence of other characteristics of the land surface, such as soil moisture, on the radar signal. These mid-latitude regions also undergo a much more moderate freeze cycle each winter, which weakens the SMAP radar's sensitivity to the freeze/thaw state in these areas.
In the planet’s highest northern latitudes, even the water in the soil is locked away as ice, making it mostly inaccessible to plants. But just a short distance to the south, in the boreal areas of Alaska, Canada, Siberia, and Scandinavia, the landscape comes alive each year after the spring thaw.