Atmospheric turbulence
Air contains interacting eddies over an enormous range of sizes. How can their combined effect on heat, momentum, and pollutants be predicted reliably?
Earth science
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Earth’s core composition
Earth’s core is mostly iron and nickel, but these alone do not explain its measured properties. Which lighter elements are mixed in, and how are they distributed?
Onset of plate tectonics
Earth’s moving plates are well established today. How and when did its early surface develop the connected system of recycling and motion we recognize as plate tectonics?
Large low shear velocity provinces
Two enormous regions near the bottom of Earth’s mantle slow seismic waves. What mixtures of heat and material create them, and how have they changed through time?
Aerosol–cloud interactions
Airborne particles change how clouds form and reflect sunlight. How much cooling do those changes produce, across different clouds and weather conditions?
Earthquake nucleation
How does slow fault slip develop into the unstable rupture of a natural earthquake?
Deep-focus earthquake mechanism
How do earthquakes occur hundreds of kilometres down, where ordinary brittle failure is suppressed?
Early geodynamo energy budget
What supplied the energy to sustain Earth’s magnetic dynamo before the solid inner core grew?
Deep mantle water cycle
How much water do subducting rocks carry deep into the mantle, and how is it exchanged?
Lightning initiation
How does fast electrical breakdown become a lightning leader in natural thunderstorm fields?
Low-cloud climate feedback
How will low clouds change under sustained warming, and how will that change affect Earth’s energy balance?
Inner-core seismic anisotropy
Seismic waves travel through Earth’s inner core at different speeds in different directions. What produces the pattern and its changes with depth?
Marine ice-cliff instability
A tall Antarctic ice cliff could break up faster than ice flows forward. Whether this can sustain accelerating retreat depends on competing deformation and failure processes.
Mid-Pleistocene transition
Why did the dominant rhythm of ice ages change about a million years ago?
Dansgaard–Oeschger events
What drove Greenland’s repeated rapid warmings during the last ice age?
Great Oxidation Event
What controlled the rise and fluctuations of atmospheric oxygen about 2.4 billion years ago?
Paleocene–Eocene Thermal Maximum carbon sources
Which carbon sources triggered and amplified the rapid warming about 56 million years ago?
Great Unconformity
Which erosion histories produced the huge gaps beneath many younger sedimentary rocks?
Deep long-period volcanic earthquakes
What produces unusual low-frequency seismic signals deep beneath volcanoes?
Hydrogen generation by serpentinization
How quickly do water and iron-bearing mantle rocks generate hydrogen underground?
Messinian salinity crisis
How much water remained in the Mediterranean during the crisis’s final freshwater-influenced stage?