Bouncing back from under the weight of Ice Age glaciers which have long since vanished, the Nordic region land mass is slowly rising above sea level. Two scientists at Sweden's KTH Royal Institute of Technology have a refined a method for measuring and predicting the small details of how this slow movement changes Earth's gravitational pull over time. One thing they found is that the Ferroscandinavian peninsula's land mass is more dense than previously known.
For decades, KTH researchers Mohammad Bagherbandi and Lars Sjöberg have been examining what's informally known as the post-glacial rebound effect in Ferroscandinavia, a peninsula that includes Sweden, Norway, Finland and part of Russia. Their latest study reports a refined measurement method that combines remote sensing by satellite and terrestrial gravity data, as well as 3D positioning from GPS and similar satellite positioning systems.
The KTH researchers found that the density of the upper mantle is about 3,546 kilograms per cubic meter—slightly more than reported in earlier studies. It is widely believed the land mass rises by as much as 1 cm per year.
Bagherbandi, a research her in geodesy and land surveying at KTH , says the new technique highlights the value of satellite data in the field of geodesy, the science of accurately measuring and understanding the Earth's geometric shape, orientation in space, and gravity field
"Beginning 60 years ago, scientists were using terrestrial gravimeters to establish gravity reference system and study temporal changes in gravity associated with glacial isostatic adjustment (GIA)," Bagherbandi says. "Our study is an alternative technique to study this phenomenon."
This means researchers can now create alternative and comparable models of how the land and gravity are changing over time in the region, he says.
"This discovery helps us understand the slow 'bounce-back' of land after the Ice Age," Bagherbandi says. "It also shows how important the Global Geodetic Observing System (GGOS) are for learning about Earth's movements and gravity changes."
A similar study is underway in the U.S., where scientists are evaluating an even larger region of North America that is known to be rising.
Bagherbandi says understanding these changes is valuable beyond the field of geodesy. It helps scientists improve their tools for studying Earth's geodynamics. It can also help with other fields, like preparing for rising sea levels and learning about natural disasters.
