Journal: Annual Review of Earth and Planetary Sciences

Abbreviation

Annu. Rev. Earth Planet. Sci.

Publisher

Annual Reviews

Journal Volumes

ISSN

0084-6597
1545-4495

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2010 - 201932020 - 20259
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Publications 1 - 10 of 12
  • Instructive Surprises in the Hydrological Functioning of Landscapes
    Item type: Review Article
    Kirchner, James W.; Benettin, Paolo; van Meerveld, Ilja (2023)
    Annual Review of Earth and Planetary Sciences
    Landscapes receive water from precipitation and then transport, store, mix, and release it, both downward to streams and upward to vegetation. How they do this shapes floods, droughts, biogeochemical cycles, contaminant transport, and the health of terrestrial and aquatic ecosystems. Because many of the key processes occur invisibly in the subsurface, our conceptualization of them has often relied heavily on physical intuition. In recent decades, however, much of this intuition has been overthrown by field observations and emerging measurement methods, particularly involving isotopic tracers. Here we summarize key surprises that have transformed our understanding of hydrological processes at the scale of hillslopes and drainage basins. These surprises have forced a shift in perspective from process conceptualizations that are relatively static, homogeneous, linear, and stationary to ones that are predominantly dynamic, heterogeneous, nonlinear, and nonstationary.
  • Toward a Natural History of Microbial Life
    Item type: Review Article
    Magnabosco, Cara; Husain, Fatima; Paoletti, Madeline M.; et al. (2024)
    Annual Review of Earth and Planetary Sciences
    For most of Earth's history life was microbial, with archaeal and bacterial cells mediating biogeochemical cycles through their metabolisms and ecologies. This diversity was sufficient to maintain a habitable planet across dramatic environmental transitions during the Archean and Proterozoic Eons. However, our knowledge of the first 3 billion years of the biosphere pales in comparison to the rich narrative of complex life documented through the Phanerozoic geological record. In this review, we attempt to lay out a microbial natural history framework that highlights recent and ongoing research unifying microbiology, geochemistry, and traditional organismal evolutionary biology, and we propose six broadly applicable principles to aid in these endeavors. In this way, the evolutionary history of microbial life-once considered only a prelude to the much more storied history of complex metazoan life in the Phanerozoic-is finally coming into its own.
  • The Composition of Earth's Lower Mantle
    Item type: Review Article
    Murakami, Motohiko; Khan, Amir; Sossi, Paolo A.; et al. (2024)
    Annual Review of Earth and Planetary Sciences
    Determining the composition of Earth's lower mantle, which constitutes almost half of its total volume, has been a central goal in the Earth sciences for more than a century given the constraints it places on Earth's origin and evolution. However, whether the major element chemistry of the lower mantle, in the form of, e.g., Mg/Si ratio, is similar to or different from the upper mantle remains debated. Here we use a multidisciplinary approach to address the question of the composition of Earth's lower mantle and, in turn, that of bulk silicate Earth (crust and mantle) by considering the evidence provided by geochemistry, geophysics, mineral physics, and geodynamics. Geochemical and geodynamical evidence largely agrees, indicating a lower-mantle molar Mg/Si of ≥1.12 (≥1.15 for bulk silicate Earth), consistent with the rock record and accumulating evidence for whole-mantle stirring. However, mineral physics–informed profiles of seismic properties, based on a lower mantle made of bridgmanite and ferropericlase, point to Mg/Si ∼ 0.9–1.0 when compared with radial seismic reference models. This highlights the importance of considering the presence of additional minerals (e.g., calcium-perovskite and stishovite) and possibly suggests a lower mantle varying compositionally with depth. In closing, we discuss how we can improve our understanding of lower-mantle and bulk silicate Earth composition, including its impact on the light element budget of the core. ▪ The chemical composition of Earth's lower mantle is indispensable for understanding its origin and evolution. ▪ Earth's lower-mantle composition is reviewed from an integrated mineral physics, geophysical, geochemical, and geodynamical perspective. ▪ A lower-mantle molar Mg/Si of ≥1.12 is favored but not unique. ▪ New experiments investigating compositional effects of bridgmanite and ferropericlase elasticity are needed to further our insight.
  • Atmospheric CO2 over the Past 66 Million Years from Marine Archives
    Item type: Review Article
    Rae, James W.B.; Zhang, Yi G.; Liu, Xiaoqing; et al. (2021)
    Annual Review of Earth and Planetary Sciences
    Throughout Earth's history, CO2 is thought to have exerted a fundamental control on environmental change. Here we review and revise CO2 reconstructions from boron isotopes in carbonates and carbon isotopes in organic matter over the Cenozoic—the past 66 million years. We find close coupling between CO2 and climate throughout the Cenozoic, with peak CO2 levels of ∼1,500 ppm in the Eocene greenhouse, decreasing to ∼500 ppm in the Miocene, and falling further into the ice age world of the Plio–Pleistocene. Around two-thirds of Cenozoic CO2 drawdown is explained by an increase in the ratio of ocean alkalinity to dissolved inorganic carbon, likely linked to a change in the balance of weathering to outgassing, with the remaining one-third due to changing ocean temperature and major ion composition. Earth system climate sensitivity is explored and may vary between different time intervals. The Cenozoic CO2 record highlights the truly geological scale of anthropogenic CO2 change: Current CO2 levels were last seen around 3 million years ago, and major cuts in emissions are required to prevent a return to the CO2 levels of the Miocene or Eocene in the coming century. - CO2 reconstructions over the past 66 Myr from boron isotopes and alkenones are reviewed and re-evaluated. - CO2 estimates from the different proxies show close agreement, yielding a consistent picture of the evolution of the ocean-atmosphere CO2 system over the Cenozoic. - CO2 and climate are coupled throughout the past 66 Myr, providing broad constraints on Earth system climate sensitivity. - Twenty-first-century carbon emissions have the potential to return CO2 to levels not seen since the much warmer climates of Earth's distant past.
  • Molecular Paleohydrology
    Item type: Journal Article
    Sachse, Dirk; Billault, Isabelle; Bowen, Gabriel J.; et al. (2012)
    Annual Review of Earth and Planetary Sciences
  • Role of Soil Erosion in Biogeochemical Cycling of Essential Elements: Carbon, Nitrogen, and Phosphorus
    Item type: Review Article
    Berhe, Asmeret A.; Barnes, Rebecca T.; Six, Johan; et al. (2018)
    Annual Review of Earth and Planetary Sciences
  • Physics of Melt Extraction from the Mantle: Speed and Style
    Item type: Review Article
    Katz, Richard F.; Jones, David W. Rees; Rudge, John F.; et al. (2022)
    Annual Review of Earth and Planetary Sciences
    Melt extraction from the partially molten mantle is among the fundamental processes shaping the solid Earth today and over geological time. A diversity of properties and mechanisms contribute to the physics of melt extraction. We review progress of the past ∼25 years of research in this area, with a focus on understanding the speed and style of buoyancy-driven melt extraction. Observations of U-series disequilibria in young lavas and the surge of deglacial volcanism in Iceland suggest this speed is rapid compared to that predicted by the null hypothesis of diffuse porous flow. The discrepancy indicates that the style of extraction is channelized. We discuss how channelization is sensitive to mechanical and thermochemical properties and feedbacks, and to asthenospheric heterogeneity. We review the grain-scale physics that underpins these properties and hence determines the physical behavior at much larger scales. We then discuss how the speed of melt extraction is crucial to predicting the magmatic response to glacial and sea-level variations. Finally, we assess the frontier of current research and identify areas where significant advances are expected over the next 25 years. In particular, we highlight the coupling of melt extraction with more realistic models of mantle thermochemistry and rheological properties. This coupling will be crucial in understanding complex settings such as subduction zones. - Mantle melt extraction shapes Earth today and over geological time. - Observations, lab experiments, and theory indicate that melt ascends through the mantle at speeds ∼30 m/year by reactively channelized porous flow. - Variations in sea level and glacial ice loading can cause significant changes in melt supply to submarine and subaerial volcanoes. - Fluid-driven fracture is important in the lithosphere and, perhaps, in the mantle wedge of subduction zones, but remains a challenge to model.
  • Biomarker Approaches for Reconstructing Terrestrial Environmental Change
    Item type: Review Article
    Inglis, Gordon N.; Bhattacharya, Tripti; Hemingway, Jordon; et al. (2022)
    Annual Review of Earth and Planetary Sciences
    The response of the terrestrial biosphere to warming remains one of the most poorly understood and quantified aspects of the climate system. One way to test the behavior of the Earth system in warm climate states is to examine the geological record. The abundance, distribution, and/or isotopic composition of source-specific organic molecules (biomarkers) have been used to reconstruct terrestrial paleoenvironmental change over a range of geological timescales. Here, we review new or recently improved biomarker approaches for reconstructing (a) physical climate variables (land temperature, rainfall), (b) ecosystem state variables (vegetation, fire regime), and (c) biogeochemical variables (soil residence time, methane cycling). This review encompasses a range of key compound classes (e.g., lipids, lignin, and carbohydrates). In each section, we explore the concept behind key biomarker approaches and discuss their successesas paleoenvironmental indicators. We emphasize that analyzing several biomarkers in tandem can provide unique insights into the Earth system. - Biomarkers can be used to reconstruct terrestrial environmental change over a range of geological timescales. - A multi-proxy biomarker approach provides novel insights into climate and the environment.
  • Coccoliths as Recorders of Paleoceanography and Paleoclimate over the Past 66 Million Years
    Item type: Review Article
    Bolton, Clara T.; Stoll, Heather (2025)
    Annual Review of Earth and Planetary Sciences
    Coccolithophores are a major group of oceanic calcifying phytoplankton, and their calcite skeletal remains, termed calcareous nannofossils, are a major component of deep-sea sediments accumulating since the Jurassic. Coccolithophores play a role in both the biological pump and the carbonate pump, exporting organic and inorganic carbon, respectively, out of the surface ocean. This means that they are key responders to and recorders of ocean carbon cycle and climate changes over geological and shorter timescales, and studying these responses can help elucidate the uncertain fate of calcifying phytoplankton under projected climate change scenarios. Here, we review established and emerging approaches for reconstructing (a) mixed-layer ocean temperature, (b) marine productivity, and (c) aspects of the ocean carbon cycle, using calcareous nannofossils from deep-sea sediments. For each parameter, we discuss the different proxies that have been proposed, based on abundance or species composition, inorganic geochemistry, and/or coccolith morphology, and explore their applications and limitations in Cenozoic paleoceanography. ▪ Calcareous nannofossils can be used to reconstruct upper ocean conditions and changes over centennial to million-year timescales. ▪ Key coccolith-based proxies for temperature, productivity, and the carbon cycle are reviewed. ▪ Approaches based on assemblages, geochemistry, and morphology provide novel insights into the evolution and adaptation of coccolithophores and past climate.
  • Carbon Fluxes in the Coastal Ocean: Synthesis, Boundary Processes, and Future Trends
    Item type: Review Article
    Dai, Minhan; Su, Jianzhong; Zhao, Yangyang; et al. (2022)
    Annual Review of Earth and Planetary Sciences
    This review examines the current understanding of the global coastal ocean carbon cycle and provides a new quantitative synthesis of air-sea CO2 exchange. This reanalysis yields an estimate for the globally integrated coastal ocean CO2 flux of −0.25 ± 0.05 Pg C year−1, with polar and subpolar regions accounting for most of the CO2 removal (>90%). A framework that classifies river-dominated ocean margin (RiOMar) and ocean-dominated margin (OceMar) systems is used to conceptualizecoastal carbon cycle processes. The carbon dynamics in three contrasting case study regions, the Baltic Sea, the Mid-Atlantic Bight, and the South China Sea, are compared in terms of the spatio-temporal variability of surface pCO2. Ocean carbon models that range from box models to three-dimensional coupled circulation-biogeochemical models are reviewed in terms of the ability to simulate key processes and project future changes in different continental shelf regions. Common unresolved challenges remain for implementation of these models across RiOMar and OceMar systems. The long-term trends in coastal ocean carbon fluxes for different coastal systems under anthropogenic stress that are emerging in observations and numerical simulations are highlighted. Knowledge gaps in projecting future perturbations associated with before and after net-zero CO2 emissions in the context of concurrent changes in the land-ocean-atmosphere coupled system pose a key challenge. - A new synthesis yields an estimate for a globally integrated coastal ocean carbon sink of −0.25 Pg C year−1, with greater than 90% of atmospheric CO2 removal occurring in polar and subpolar regions. - The sustained coastal and open ocean carbon sink is vital in mitigating climate change and meeting the target set by the Paris Agreement. - Uncertainties in the future coastal ocean carbon cycle are associated with concurrent trends and changes in the land-ocean-atmosphere coupled system. - The major gaps and challenges identified for current coastal ocean carbon research have important implications for climate and sustainability policies.
Publications 1 - 10 of 12