One of the world's biggest cold fronts might be under our feet rather than over our heads, according to results from earth scientists at The Johns Hopkins University.
Writing in this week's issue of "Science," Hopkins researchers describe a laboratory experiment designed to model conditions in the outer core of the Earth, which is composed of molten iron. The laboratory results point to the possibility that a thin jet of relatively cold molten iron is streaming down across the liquid outer core from an area in the mid-Pacific to Earth's solid iron inner core.
Ikuro Sumita, a postdoctoral researcher at Hopkins and lead author on the paper, cautions that the new model is a "working hypothesis" and that there are many questions and concerns still to be addressed. But he has developed several tantalizingly direct ways to use the model to answer questions about observations relating to the Earth's core.
The Earth's molten outer core lies beneath the rocky mantle, which includes the surface. Earth scientists think of the mantle as the "master" that directs the activity of the outer core, which acts like a "slave" in response. Because of this close relationship, understanding the core's activity should help scientists better understand the mantle's behavior.
It's not possible, however, to directly observe the outer core. Scientists can image the solid inner core using energy from earthquakes, known as seismic waves. But this reveals little of the liquid outer core.
"What we have to rely on instead to study the outer core is Earth's magnetic field, which is produced by the flow of molten iron," says Sumita.
Scientists can link changes in the strength and direction of magnetic fields above ground to the ebb and flow of molten iron below ground, Sumita explains. "For example, we can interpret the westward motion of the magnetic field patches as a manifestation of the westward flow in the core," he notes.