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S. D. Jacobsen

Editor, Geophysical Research Letters

World map showing location of permanent geomagnetic observatories and their data availability for electromagnetic source characterization.
Posted inEditors' Highlights

Globally Variable Water Content in the Mantle Transition Zone

by S. D. Jacobsen 9 June 20204 August 2023

Using electromagnetic waves originating in the ionosphere and magnetosphere, conductivity profiles reaching the deep upper mantle show surprising variability in water content.

Map of the Lesser Antilles volcanic arc showing the subduction zone trench and the location of two Deep Sea Drilling Cores
Posted inEditors' Highlights

Extremely High Carbon Return in Certain Volcanic Arcs

by S. D. Jacobsen 3 June 202023 September 2022

By comparing measured volcanic output with subducted carbon fluxes from drill cores, the Lesser Antilles subduction zone shows nearly complete slab carbon release at sub-arc depths.

Sediment sampling sites along the Chilean coast showing the locations of marine surface sediment sampling and river sediment sampling.
Posted inEditors' Highlights

Tracking Reverse Weathering

by S. D. Jacobsen 12 March 202024 February 2022

Using beryllium isotopes to track in situ formation of clays in the ocean, known as reverse weathering, will improve global models of atmospheric carbon dioxide and ocean alkalinity.

Photo of outcrop of the Loma Blanca fault-damage zone in New Mexico, USA
Posted inEditors' Highlights

What Controls How Quickly Faults Heal?

by S. D. Jacobsen 11 December 20196 October 2021

The rates at which fault zones “heal” through secondary mineralization have been elusive, but uranium-thorium dating of calcite growth in fault-zone fractures may provide the answer.

A graph showing total conductive heat flow in the core as a function of radius for pure iron (black line) and compositional models containing Fe-Ni-S (blue line) and Fe-Ni-Si (red line)
Posted inEditors' Highlights

Thermal Convection Can Power the Geodynamo

by S. D. Jacobsen 4 November 201910 March 2022

New high-pressure experiments on fluid iron suggest thermal convection without compositional buoyancy is sufficient to drive the dynamo generating Earth’s magnetic field.

Structure of hydrous eutectic silicate melts at different temperatures and pressures
Posted inEditors' Highlights

Hiding Deep Hydrous Melts at the Core-Mantle Boundary

by S. D. Jacobsen 13 September 20194 August 2023

Silicate melts containing H2O in the lowermost mantle are surprisingly dense and may stagnate there, trapping primordial volatiles and potentially causing some of the ultra-low velocity zones.

X-ray tomography images of experimental magmas captured at different crystal contents
Posted inEditors' Highlights

Crystals Connect Bubbles in Explosive Magmas

by S. D. Jacobsen 28 May 20195 October 2022

Hydrous silica-rich magmas can degas through connected bubble pathways when as little as 20% crystals are present, influencing transitions from explosive, Vulcanian-style eruptions to lava effusion.

Posted inEditors' Highlights

Carbonate Melting Enhances Mantle CO2 Fluxes in Old Ocean Basins

by S. D. Jacobsen 17 August 20184 August 2023

The amount of CO2 segregated from the mantle by carbonate melting beneath old oceanic crust may equal that emitted along the mid-ocean ridge system, thereby contributing to the global carbon cycle.

A view of a Washington, D.C., skyline from the Potomac River at night. The Lincoln Memorial (at left) and the Washington Monument (at right) are lit against a purple sky. Over the water of the Potomac appear the text “#AGU24 coverage from Eos.”

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Decoding Crop Evapotranspiration

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