Big Data Seismology is an emergent subdiscipline that uses “big data” inquiries to explore fundamental science questions in seismology

Three drivers of Big Data Seismology are the growth of large data volumes, the development of new algorithms, and advances in computing

Big Data Seismology is being applied to study earthquakes, to better resolve Earth structure, and to open new frontiers in seismology

The editorial board thanks the 2021 peer reviewers

Anthropogenic CO₂ emissions would have produced larger atmospheric increases if ocean and land sinks had not removed over half of this CO₂

Uptake by both ocean and land sinks increased in response to rising atmospheric CO₂ levels, maintaining the airborne fraction near 45%

Improved and sustained measurements and models are needed to track changes in sinks and enhance the scientific basis for carbon management

We critically review the potential role(s) of quartz cementation as a mechanism of fault “healing” on seismic cycle timescales

Our current understanding of silica kinetics cannot explain cementation of mesoscale fault-fracture networks within interseismic periods

Thin principal slip zones may be cemented interseismically but a complete understanding of fault-related quartz growth requires further work

Tides play a primary role in salt marsh surface water and groundwater interactions

Surface water and groundwater interactions affect plant zonation, and carbon and nutrient outwelling

Future research needs to couple hydrological processes to ecological and geochemical processes

Understanding and predicting fractured systems requires integrating field and lab experiments, simulation and uncertainty quantification

Densely monitored field sites and in situ lab experiments provide quantitative measures of flow and transport that can constrain models

Physics-based models with machine-learning emulators enable uncertainty quantification of flow and transport in complex fracture networks

Radiocarbon is a powerful carbon cycle tracer and radiometric dating tool, that is widely used in paleoceanography

Marine radiocarbon activities, relative to the contemporary atmosphere, integrate three main effects: gas exchange, transport times, and the mixing of different water masses

Reconstructions attest to ocean ventilation's role in past CO₂ change, but the long-term closure of the radiocarbon cycle remains unresolved

Using station and gridded data sets, we compare global precipitation and temperature trends by elevation

Local comparisons of paired stations and regional comparisons using gridded data often show faster mountain than lowland warming

Precipitation differences between mountains and adjacent lowlands are reducing, often driven by stronger precipitation increase in lowlands

Most forests are naturally patchy. Many are being fragmented by humans. Studies of forest-air exchange rarely consider this heterogeneity

Gaps, edges, and patchy sources/sinks generate fluxes of momentum and scalars. Scalar quantities are rarely at equilibrium around forests

Better representations of forest structure, for example, from laser scans, should be included in models, along with more physics and chemistry