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  • Carbon cycle  (18)
  • 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
  • John Wiley & Sons  (17)
  • Nature Publishing Group  (3)
  • 1
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    Dynamic feeder dyke systems in basaltic volcanoes: the exceptional example o fthe 1809 Etna eruption (Italy) (2015)
    Nature Publishing Group
    Details
    Publication Date: 2017-04-04
    Description: In this paper, we describe the 1809 eruption of Mt. Etna, Italy, which represents one historical rare case in which it is possible to observe details of the internal structure of the feeder system. This is possible thanks to the presence of two large pit craters located in the middle of the eruptive fracture field that allow studying a section of the shallow feeder system. Along the walls of one of these craters, we analysed well-exposed cross sections of the uppermost 15–20 m of the feeder system and related volcanic products. Here, we describe the structure, morphology and lithology of this portion of the 1809 feeder system, including the host rock which conditioned the propagation of the dyke, and compare the results with other recent eruptions. Finally, we propose the dynamic model of the magma behaviour inside a laterally-propagating feeder dyke, demonstrating how this dynamic triggered important changes in the eruptive style (from effusive/Strombolian to phreatomagmatic) during the same eruption. Our results are also useful for hazard assessment related to the development of flank eruptions, potentially the most hazardous type of eruption from basaltic volcanoes in densely urbanized areas, such as Mt. Etna.
    Description: Published
    Description: 1-11
    Description: 2T. Tettonica attiva
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: 3V. Dinamiche e scenari eruttivi
    Description: 4V. Vulcani e ambiente
    Description: 6A. Monitoraggio ambientale, sicurezza e territorio
    Description: N/A or not JCR
    Description: open
    Keywords: feeder dyke ; basaltic volcanoes ; flank eruptions ; Etna ; volcanic hazards ; sill ; volcanic rift ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.04. Thermodynamics ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
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    Rapid differentiation in a sill-like magma reservoir: a case study from the campi flegrei caldera (2012)
    Nature Publishing Group
    Details
    Publication Date: 2017-04-04
    Description: In recent decades, geophysical investigations have detected wide magma reservoirs beneath quiescent calderas. However, the discovery of partially melted horizons inside the crust is not sufficient to put constraints on capability of reservoirs to supply cataclysmic eruptions, which strictly depends on the chemical-physical properties of magmas (composition, viscosity, gas content etc.), and thus on their differentiation histories. In this study, by using geochemical, isotopic and textural records of rocks erupted from the high-risk Campi Flegrei caldera, we show that the alkaline magmas have evolved toward a critical state of explosive behaviour over a time span shorter than the repose time of most volcanic systems and that these magmas have risen rapidly toward the surface. Moreover, similar results on the depth and timescale of magma storage were previously obtained for the neighbouring Somma-Vesuvius volcano. This consistency suggests that there might be a unique long-lived magma pool beneath the whole Neapolitan area.
    Description: Published
    Description: article 712
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: N/A or not JCR
    Description: open
    Keywords: magma ; campi flegrei caldera ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 3
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    The multiple fates of sinking particles in the North Atlantic Ocean (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 29 (2015): 1471–1494, doi:10.1002/2014GB005037.
    Description: The direct respiration of sinking organic matter by attached bacteria is often invoked as the dominant sink for settling particles in the mesopelagic ocean. However, other processes, such as enzymatic solubilization and mechanical disaggregation, also contribute to particle flux attenuation by transferring organic matter to the water column. Here we use observations from the North Atlantic Ocean, coupled to sensitivity analyses of a simple model, to assess the relative importance of particle-attached microbial respiration compared to the other processes that can degrade sinking particles. The observed carbon fluxes, bacterial production rates, and respiration by water column and particle-attached microbial communities each spanned more than an order of magnitude. Rates of substrate-specific respiration on sinking particle material ranged from 0.007 ± 0.003 to 0.173 ± 0.105 day−1. A comparison of these substrate-specific respiration rates with model results suggested sinking particle material was transferred to the water column by various biological and mechanical processes nearly 3.5 times as fast as it was directly respired. This finding, coupled with strong metabolic demand imposed by measurements of water column respiration (729.3 ± 266.0 mg C m−2 d−1, on average, over the 50 to 150 m depth interval), suggested a large fraction of the organic matter evolved from sinking particles ultimately met its fate through subsequent remineralization in the water column. At three sites, we also measured very low bacterial growth efficiencies and large discrepancies between depth-integrated mesopelagic respiration and carbon inputs.
    Description: U.S. Environmental Protection Agency (EPA) STAR Grant Number: FP-91744301-0; National Science Foundation Grant Numbers OCE-1061883, EF-0424599, OCE-1155438, OCE-1059884, OCE-1031143; Gordon and Betty Moore Foundation Grant Numbers: 3301, 3789; Gordon and Betty Moore Foundation; Woods Hole Oceanographic Institution
    Description: 2016-03-25
    Keywords: Carbon cycle ; Particle flux ; Bacterial growth efficiency ; Bacterial respiration ; Microbial respiration
    Repository Name: Woods Hole Open Access Server
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  • 4
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    The annual cycle of gross primary production, net community production, and export efficiency across the North Pacific Ocean (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 30 (2016): 361–380, doi:10.1002/2015GB005318.
    Description: We measured triple oxygen isotopes and oxygen/argon dissolved gas ratios as nonincubation-based geochemical tracers of gross oxygen production (GOP) and net community production (NCP) on 16 container ship transects across the North Pacific from 2008 to 2012. We estimate rates and efficiency of biological carbon export throughout the full annual cycle across the North Pacific basin (35°N–50°N, 142°E–125°W) by constructing mixed layer budgets that account for physical and biological influences on these tracers. During the productive season from spring to fall, GOP and NCP are highest in the Kuroshio region west of 170°E and decrease eastward across the basin. However, deep winter mixed layers (〉200 m) west of 160°W ventilate ~40–90% of this seasonally exported carbon, while only ~10% of seasonally exported carbon east of 160°W is ventilated in winter where mixed layers are 〈120 m. As a result, despite higher annual GOP in the west than the east, the annual carbon export (sequestration) rate and efficiency decrease westward across the basin from export of 2.3 ± 0.3 mol C m−2 yr−1 east of 160°W to 0.5 ± 0.7 mol C m−2 yr−1 west of 170°E. Existing productivity rate estimates from time series stations are consistent with our regional productivity rate estimates in the eastern but not western North Pacific. These results highlight the need to estimate productivity rates over broad spatial areas and throughout the full annual cycle including during winter ventilation in order to accurately estimate the rate and efficiency of carbon sequestration via the ocean's biological pump.
    Description: This work was funded by a NDSEG Fellowship from the Office of Naval Research, a NSF Graduate Research Fellowship, and an ARCS Foundation Fellowship to H.I.P. and by NSF Ocean Sciences (0628663 and 1259055 to P.D.Q.).
    Description: 2016-08-27
    Keywords: North Pacific ; Carbon cycle ; Productivity ; Biological pump ; Gross oxygen production ; Net community production
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  • 5
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    Seasonal asymmetry in the evolution of surface ocean pCO2 and pH thermodynamic drivers and the influence on sea‐air CO2 flux (2018)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Global Biogeochemical Cycles 32 (2018): 1476-1497, doi:10.1029/2017GB005855.
    Description: It has become clear that anthropogenic carbon invasion into the surface ocean drives changes in the seasonal cycles of carbon dioxide partial pressure (pCO2) and pH. However, it is not yet known whether the resulting sea‐air CO2 fluxes are symmetric in their seasonal expression. Here we consider a novel application of observational constraints and modeling inferences to test the hypothesis that changes in the ocean's Revelle factor facilitate a seasonally asymmetric response in pCO2 and the sea‐air CO2 flux. We use an analytical framework that builds on observed sea surface pCO2 variability for the modern era and incorporates transient dissolved inorganic carbon concentrations from an Earth system model. Our findings reveal asymmetric amplification of pCO2 and pH seasonal cycles by a factor of two (or more) above preindustrial levels under Representative Concentration Pathway 8.5. These changes are significantly larger than observed modes of interannual variability and are relevant to climate feedbacks associated with Revelle factor perturbations. Notably, this response occurs in the absence of changes to the seasonal cycle amplitudes of dissolved inorganic carbon, total alkalinity, salinity, and temperature, indicating that significant alteration of surface pCO2 can occur without modifying the physical or biological ocean state. This result challenges the historical paradigm that if the same amount of carbon and nutrients is entrained and subsequently exported, there is no impact on anthropogenic carbon uptake. Anticipation of seasonal asymmetries in the sea surface pCO2 and CO2 flux response to ocean carbon uptake over the 21st century may have important implications for carbon cycle feedbacks.
    Description: Cooperative Institute for Climate Science Grant Number: NA17RJ2612; David and Lucile Packard Foundation/MBARI Grant Number: 4696; NOAA Office of Climate Observations Grant Number: NA11OAR4310066; NOAA. Grant Number NA11OAR4310066; KBR Grant Numbers: A08OAR4320752, NA17RJ2612
    Keywords: Revelle Factor ; Carbon cycle ; Seasonal cycle ; CO2 fluxes ; Ocean acidification
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Impact of recently upwelled water on productivity investigated using in situ and incubation-based methods in Monterey Bay (2017)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 1901–1926, doi:10.1002/2016JC012306.
    Description: Photosynthetic conversion of inline image to organic carbon and the transport of this carbon from the surface to the deep ocean is an important regulator of atmospheric inline image. To understand the controls on carbon fluxes in a productive region impacted by upwelling, we measured biological productivity via multiple methods during a cruise in Monterey Bay, California. We quantified net community production and gross primary production from measurements of inline image/Ar and inline image triple isotopes ( inline image), respectively. We simultaneously conducted incubations measuring the uptake of 14C, inline image, and inline image, and nitrification, and deployed sediment traps. At the start of the cruise (Phase 1) the carbon cycle was at steady state and the estimated net community production was 35(10) and 35(8) mmol C m−2 d−1 from inline image/Ar and 15N incubations, respectively, a remarkably good agreement. During Phase 1, net primary production was 96(27) mmol C m−2 d−1 from C uptake, and gross primary production was 209(17) mmol C m−2 d−1 from inline image. Later in the cruise (Phase 2), recently upwelled water with higher nutrient concentrations entered the study area, causing 14C and inline image uptake to increase substantially. Continuous inline image/Ar measurements revealed submesoscale variability in water mass structure and likely productivity in Phase 2 that was not evident from the incubations. These data demonstrate that inline image/Ar and inline image incubation-based NCP estimates can give equivalent results in an N-limited, coastal system, when the nonsteady state inline image fluxes are negligible or can be quantified.
    Description: Funding for this work was provided by NSF awards OCE-1060840 to R.H.R. Stanley, OCE-1129644 to D.P. Nicholson, OCE-1357042 to F.P. Chavez, NASA award NNX14AI06G to M.R. Fewings, the David and Lucile Packard Foundation through their generous annual donation to the Monterey Bay Aquarium Research Institute, an Ocean Ventures Fund award from the WHOI Academic Programs Office to CC Manning, and graduate scholarships from NSERC and CMOS to CC Manning.
    Description: 2017-09-11
    Keywords: Marine productivity ; Carbon cycle ; Dissolved gases
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  • 7
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    Discrepant estimates of primary and export production from satellite algorithms, a biogeochemical model, and geochemical tracer measurements in the North Pacific Ocean (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 43 (2016): 8645–8653, doi:10.1002/2016GL070226.
    Description: Estimates of primary and export production (PP and EP) based on satellite remote sensing algorithms and global biogeochemical models are widely used to provide year-round global coverage not available from direct observations. However, observational data to validate these approaches are limited. We find that no single satellite algorithm or model can reproduce seasonal and annual geochemically determined PP, export efficiency (EP/PP), and EP rates throughout the North Pacific basin, based on comparisons throughout the full annual cycle at time series stations in the subarctic and subtropical gyres and basin-wide regions sampled by container ship transects. The high-latitude regions show large PP discrepancies in winter and spring and strong effects of deep winter mixed layers on annual EP that cannot be accounted for in current satellite-based approaches. These results underscore the need to evaluate satellite- and model-based estimates using multiple productivity parameters measured over broad ocean regions throughout the annual cycle.
    Description: NDSEG Fellowship from the Office of Naval Research; NSF Graduate Research Fellowship; ARCS Foundation Fellowship
    Description: 2017-02-28
    Keywords: North Pacific ; Productivity ; Biological pump ; Carbon cycle
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  • 8
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    Sea surface pCO2 and O2 dynamics in the partially ice-covered Arctic Ocean (2017)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 1425–1438, doi:10.1002/2016JC012162.
    Description: Understanding the physical and biogeochemical processes that control CO2 and dissolved oxygen (DO) dynamics in the Arctic Ocean (AO) is crucial for predicting future air-sea CO2 fluxes and ocean acidification. Past studies have primarily been conducted on the AO continental shelves during low-ice periods and we lack information on gas dynamics in the deep AO basins where ice typically inhibits contact with the atmosphere. To study these gas dynamics, in situ time-series data have been collected in the Canada Basin during late summer to autumn of 2012. Partial pressure of CO2 (pCO2), DO concentration, temperature, salinity, and chlorophyll-a fluorescence (Chl-a) were measured in the upper ocean in a range of sea ice states by two drifting instrument systems. Although the two systems were on average only 222 km apart, they experienced considerably different ice cover and external forcings during the 40–50 day periods when data were collected. The pCO2 levels at both locations were well below atmospheric saturation whereas DO was almost always slightly supersaturated. Modeling results suggest that air-sea gas exchange, net community production (NCP), and horizontal gradients were the main sources of pCO2 and DO variability in the sparsely ice-covered AO. In areas more densely covered by sea ice, horizontal gradients were the dominant source of variability, with no significant NCP in the surface mixed layer. If the AO reaches equilibrium with atmospheric CO2 as ice cover continues to decrease, aragonite saturation will drop from a present mean of 1.00 ± 0.02 to 0.86 ± 0.01.
    Description: U.S. National Science Foundation Arctic Observing Network Grant Number: ARC-1107346 and ARC-0856479
    Description: 2017-08-25
    Keywords: Arctic Ocean ; CO2 ; O2 ; Biogeochemistry ; Dynamics ; Carbon cycle
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  • 9
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    Carbon budget of tidal wetlands, estuaries, and shelf waters of eastern North America (2018)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 32 (2018): 389-416, doi:10.1002/2017GB005790.
    Description: Carbon cycling in the coastal zone affects global carbon budgets and is critical for understanding the urgent issues of hypoxia, acidification, and tidal wetland loss. However, there are no regional carbon budgets spanning the three main ecosystems in coastal waters: tidal wetlands, estuaries, and shelf waters. Here we construct such a budget for eastern North America using historical data, empirical models, remote sensing algorithms, and process‐based models. Considering the net fluxes of total carbon at the domain boundaries, 59 ± 12% (± 2 standard errors) of the carbon entering is from rivers and 41 ± 12% is from the atmosphere, while 80 ± 9% of the carbon leaving is exported to the open ocean and 20 ± 9% is buried. Net lateral carbon transfers between the three main ecosystem types are comparable to fluxes at the domain boundaries. Each ecosystem type contributes substantially to exchange with the atmosphere, with CO2 uptake split evenly between tidal wetlands and shelf waters, and estuarine CO2 outgassing offsetting half of the uptake. Similarly, burial is about equal in tidal wetlands and shelf waters, while estuaries play a smaller but still substantial role. The importance of tidal wetlands and estuaries in the overall budget is remarkable given that they, respectively, make up only 2.4 and 8.9% of the study domain area. This study shows that coastal carbon budgets should explicitly include tidal wetlands, estuaries, shelf waters, and the linkages between them; ignoring any of them may produce a biased picture of coastal carbon cycling.
    Description: NASA Interdisciplinary Science program Grant Number: NNX14AF93G; NASA Carbon Cycle Science Program Grant Number: NNX14AM37G; NASA Ocean Biology and Biogeochemistry Program Grant Number: NNX11AD47G; National Science Foundation's Chemical Oceanography Program Grant Number: OCE‐1260574
    Description: 2018-10-04
    Keywords: Carbon cycle ; Coastal zone ; Tidal wetlands ; Estuaries ; Shelf waters
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  • 10
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    Freshwater and its role in the Arctic Marine System : sources, disposition, storage, export, and physical and biogeochemical consequences in the Arctic and global oceans (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Geophysical Research: Biogeosciences 121 (2016): 675-717, doi:10.1002/2015JG003140.
    Description: The Arctic Ocean is a fundamental node in the global hydrological cycle and the ocean's thermohaline circulation. We here assess the system's key functions and processes: (1) the delivery of fresh and low-salinity waters to the Arctic Ocean by river inflow, net precipitation, distillation during the freeze/thaw cycle, and Pacific Ocean inflows; (2) the disposition (e.g., sources, pathways, and storage) of freshwater components within the Arctic Ocean; and (3) the release and export of freshwater components into the bordering convective domains of the North Atlantic. We then examine physical, chemical, or biological processes which are influenced or constrained by the local quantities and geochemical qualities of freshwater; these include stratification and vertical mixing, ocean heat flux, nutrient supply, primary production, ocean acidification, and biogeochemical cycling. Internal to the Arctic the joint effects of sea ice decline and hydrological cycle intensification have strengthened coupling between the ocean and the atmosphere (e.g., wind and ice drift stresses, solar radiation, and heat and moisture exchange), the bordering drainage basins (e.g., river discharge, sediment transport, and erosion), and terrestrial ecosystems (e.g., Arctic greening, dissolved and particulate carbon loading, and altered phenology of biotic components). External to the Arctic freshwater export acts as both a constraint to and a necessary ingredient for deep convection in the bordering subarctic gyres and thus affects the global thermohaline circulation. Geochemical fingerprints attained within the Arctic Ocean are likewise exported into the neighboring subarctic systems and beyond. Finally, we discuss observed and modeled functions and changes in this system on seasonal, annual, and decadal time scales and discuss mechanisms that link the marine system to atmospheric, terrestrial, and cryospheric systems.
    Description: World Climate Research Program-Climate and Cryosphere (WCRP-CliC); Arctic Monitoring and Assessment Program (AMAP) International Arctic Science Committee (IASC); Norwegian Ministries of Environment and of Foreign Affairs; Swedish Secretariat for Environmental Earth System Sciences (SSEESS); Swedish Polar Research Secretariat; NSF Grant Numbers: OCE 1130008, 1249133, AON-1203473, AON-1338948, OCE 1434041; Polar Research Programme of the Norwegian Research Council Grant Number: 226415
    Keywords: Arctic ; Oceans ; Circulation ; Freshwater ; Carbon cycle ; Acidification
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  • 11
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    Influence of biological carbon export on ocean carbon uptake over the annual cycle across the North Pacific Ocean (2017)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 31 (2017): 81–95, doi:10.1002/2016GB005527.
    Description: We evaluate the influences of biological carbon export, physical circulation, and temperature-driven solubility changes on air-sea CO2 flux across the North Pacific basin (35°N–50°N, 142°E–125°W) throughout the full annual cycle by constructing mixed layer budgets for dissolved inorganic carbon (DIC) and pCO2, determined on 15 container ship transects between Hong Kong and Long Beach, CA, from 2008 to 2012. Annual air-sea CO2 flux is greatest in the western North Pacific and decreases eastward across the basin (2.7 ± 0.9 mol C m−2 yr−1 west of 170°E, as compared to 2.1 ± 0.3 mol C m−2 yr−1 east of 160°W). East of 160°W, DIC removal by annual net community production (NCP) more than fully offsets the DIC increase due to air-sea CO2 flux. However, in the region west of 170°E influenced by deep winter mixing, annual NCP only offsets ~20% of the DIC increase due to air-sea CO2 flux, requiring significant DIC removal by geostrophic advection. Temperature-driven solubility changes have no net influence on pCO2 and account for 〈25% of annual CO2 uptake. The seasonal timing of NCP strongly affects its influence on air-sea CO2 flux. Biological carbon export from the mixed layer has a stronger influence on pCO2 in summer when mixed layers are shallow, but changes in pCO2 have a stronger influence on air-sea CO2 flux in winter when high wind speeds drive more vigorous gas exchange. Thus, it is necessary to determine the seasonal timing as well as the annual magnitude of NCP to determine its influence on ocean carbon uptake.
    Description: NDSEG Fellowship from the Office of Naval Research; NSF Graduate Research Fellowship; NSF Ocean Sciences Grant Numbers: 0628663, 1259055; NOAA Climate Program Office Grant Number: A10OAR4310088
    Description: 2017-07-21
    Keywords: Carbon cycle ; North Pacific ; Biological pump
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  • 12
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    Interactions between land use change and carbon cycle feedbacks (2017)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 31 (2017): 96–113, doi:10.1002/2016GB005374.
    Description: Using the Community Earth System Model, we explore the role of human land use and land cover change (LULCC) in modifying the terrestrial carbon budget in simulations forced by Representative Concentration Pathway 8.5, extended to year 2300. Overall, conversion of land (e.g., from forest to croplands via deforestation) results in a model-estimated, cumulative carbon loss of 490 Pg C between 1850 and 2300, larger than the 230 Pg C loss of carbon caused by climate change over this same interval. The LULCC carbon loss is a combination of a direct loss at the time of conversion and an indirect loss from the reduction of potential terrestrial carbon sinks. Approximately 40% of the carbon loss associated with LULCC in the simulations arises from direct human modification of the land surface; the remaining 60% is an indirect consequence of the loss of potential natural carbon sinks. Because of the multicentury carbon cycle legacy of current land use decisions, a globally averaged amplification factor of 2.6 must be applied to 2015 land use carbon losses to adjust for indirect effects. This estimate is 30% higher when considering the carbon cycle evolution after 2100. Most of the terrestrial uptake of anthropogenic carbon in the model occurs from the influence of rising atmospheric CO2 on photosynthesis in trees, and thus, model-projected carbon feedbacks are especially sensitive to deforestation.
    Description: National Science Foundation Grant Numbers: AGS 1049033, CCF-1522054
    Description: 2017-07-23
    Keywords: Carbon cycle ; Climate change ; Land use and land cover change ; Earth system models
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  • 13
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    Separating the influence of temperature, drought, and fire on interannual variability in atmospheric CO2 (2015)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Global Biogeochemical Cycles 28 (2014): 1295–1310, doi:10.1002/2014GB004890.
    Description: The response of the carbon cycle in prognostic Earth system models (ESMs) contributes significant uncertainty to projections of global climate change. Quantifying contributions of known drivers of interannual variability in the growth rate of atmospheric carbon dioxide (CO2) is important for improving the representation of terrestrial ecosystem processes in these ESMs. Several recent studies have identified the temperature dependence of tropical net ecosystem exchange (NEE) as a primary driver of this variability by analyzing a single, globally averaged time series of CO2 anomalies. Here we examined how the temporal evolution of CO2 in different latitude bands may be used to separate contributions from temperature stress, drought stress, and fire emissions to CO2 variability. We developed atmospheric CO2 patterns from each of these mechanisms during 1997–2011 using an atmospheric transport model. NEE responses to temperature, NEE responses to drought, and fire emissions all contributed significantly to CO2 variability in each latitude band, suggesting that no single mechanism was the dominant driver. We found that the sum of drought and fire contributions to CO2 variability exceeded direct NEE responses to temperature in both the Northern and Southern Hemispheres. Additional sensitivity tests revealed that these contributions are masked by temporal and spatial smoothing of CO2 observations. Accounting for fires, the sensitivity of tropical NEE to temperature stress decreased by 25% to 2.9 ± 0.4 Pg C yr−1 K−1. These results underscore the need for accurate attribution of the drivers of CO2 variability prior to using contemporary observations to constrain long-term ESM responses.
    Description: This work was supported by the Department of Energy Office of Science Biological and Environmental Research Division, the National Science Foundation Decadal and Regional Climate Prediction using Earth System Models (EaSM) program (NSF AGS 1048890 and AGS 1048827), and NASA Carbon Cycle Science (NASA NNX11AF96G). G.K.A. acknowledges a NOAA Climate and Global Change postdoctoral fellowship. J.B.M. and E.J.D. thank NOAA's Climate Program Office's Atmospheric Chemistry, Carbon Cycle, and Climate (AC4) program for support
    Keywords: Carbon cycle ; Climate variability ; Drought ; Fire ; Terrestrial ecosystems ; Atmospheric CO2
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  • 14
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    Temporal and spatial variability of particle transport in the deep Arctic Canada Basin (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Geophysical Research: Oceans 120 (2015): 2784–2799, doi:10.1002/2014JC010643.
    Description: To better understand the current carbon cycle and potentially detect its change in the rapidly changing Arctic Ocean, we examined sinking particles collected quasi-continuously over a period of 7 years (2004–2011) by bottom-tethered sediment trap moorings in the central Canada Basin. Total mass flux was very low (〈100 mg m−2 d−1) at all sites and was temporally decoupled from the cycle of primary production in surface waters. Extremely low radiocarbon contents of particulate organic carbon and high aluminum contents in sinking particles reveal high contributions of resuspended sediment to total sinking particle flux in the deep Canada Basin. Station A (75°N, 150°W) in the southwest quadrant of the Canada Basin is most strongly influenced while Station C (77°N, 140°W) in the northeast quadrant is least influenced by lateral particle supply based on radiocarbon content and Al concentration. The results at Station A, where three sediment traps were deployed at different depths, imply that the most likely mode of lateral particle transport was as thick clouds of enhanced particle concentration extending well above the seafloor. At present, only 1%–2% of the low levels of new production in Canada Basin surface waters reaches the interior basin. Lateral POC supply therefore appears to be the major source of organic matter to the interior basin. However, ongoing changes to surface ocean boundary conditions may influence both lateral and vertical supply of particulate material to the deep Canada Basin.
    Description: This research was funded by the NSF Division of Polar Programs (ARC-0909377), the Ocean and Climate Change Institute of Woods Hole Oceanographic Institution, and ETH Zürich. J.H. and M.K. were partly supported by the National Research Foundation of Korea grant funded by the Korean Government (2011–0013629).
    Keywords: Canada Basin ; Particulate organic carbon ; Lateral supply ; Radiocarbon ; Carbon cycle
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 15
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    Can rates of ocean primary production and biological carbon export be related through their probability distributions? (2018)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Global Biogeochemical Cycles 32 (2018): 954-970, doi:10.1029/2017GB005797.
    Description: We describe the basis of a theory for interpreting measurements of two key biogeochemical fluxes—primary production by phytoplankton (p, μg C · L−1 · day−1) and biological carbon export from the surface ocean by sinking particles (f, mg C · m−2 · day−1)—in terms of their probability distributions. Given that p and f are mechanistically linked but variable and effectively measured on different scales, we hypothesize that a quantitative relationship emerges between collections of the two measurements. Motivated by the many subprocesses driving production and export, we take as a null model that large‐scale distributions of p and f are lognormal. We then show that compilations of p and f measurements are consistent with this hypothesis. The compilation of p measurements is extensive enough to subregion by biome, basin, depth, or season; these subsets are also well described by lognormals, whose log‐moments sort predictably. Informed by the lognormality of both p and f we infer a statistical scaling relationship between the two quantities and derive a linear relationship between the log‐moments of their distributions. We find agreement between two independent estimates of the slope and intercept of this line and show that the distribution of f measurements is consistent with predictions made from the moments of the p distribution. These results illustrate the utility of a distributional approach to biogeochemical fluxes. We close by describing potential uses and challenges for the further development of such an approach.
    Description: National Science Foundation Grant Number: OCE-1315201; Simons Foundation Grant Numbers: 329108, 553242; National Aeronautics and Space Administration Grant Numbers: NNX16AR47G, NNX16AR49G
    Keywords: Primary production ; Carbon export ; Export flux ; Lognormal distribution ; Scaling relationship ; Carbon cycle
    Repository Name: Woods Hole Open Access Server
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  • 16
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    How data set characteristics influence ocean carbon export models (2018)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 32 (2018): 1312-1328, doi:10.1029/2018GB005934.
    Description: Ocean biological processes mediate the transport of roughly 10 petagrams of carbon from the surface to the deep ocean each year and thus play an important role in the global carbon cycle. Even so, the globally integrated rate of carbon export out of the surface ocean remains highly uncertain. Quantifying the processes underlying this biological carbon export requires a synthesis between model predictions and available observations of particulate organic carbon (POC) flux; yet the scale dissimilarities between models and observations make this synthesis difficult. Here we compare carbon export predictions from a mechanistic model with observations of POC fluxes from several data sets compiled from the literature spanning different space, time, and depth scales as well as using different observational methodologies. We optimize model parameters to provide the best match between model‐predicted and observed POC fluxes, explicitly accounting for sources of error associated with each data set. Model‐predicted globally integrated values of POC flux at the base of the euphotic layer range from 3.8 to 5.5 Pg C/year, depending on the data set used to optimize the model. Modeled carbon export pathways also vary depending on the data set used to optimize the model, as well as the satellite net primary production data product used to drive the model. These findings highlight the importance of collecting field data that average over the substantial natural temporal and spatial variability in carbon export fluxes, and advancing satellite algorithms for ocean net primary production, in order to improve predictions of biological carbon export.
    Description: NASA Ocean Biology and Biogeochemistry Program Grant Numbers: NNX16AR49G, NNXA122G, NNX16AR47G, OBB16_2‐0031; National Science Foundation
    Description: 2019-03-13
    Keywords: Carbon flux ; Remote sensing ; Carbon cycle ; Mechanistic model ; Optimization
    Repository Name: Woods Hole Open Access Server
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  • 17
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    Land carbon sequestration within the conterminous United States : regional- and state-level analyses (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 120 (2015): 379–398, doi:10.1002/2014JG002818.
    Description: A quantitative understanding of the rate at which land ecosystems are sequestering or losing carbon at national-, regional-, and state-level scales is needed to develop policies to mitigate climate change. In this study, a new improved historical land use and land cover change data set is developed and combined with a process-based ecosystem model to estimate carbon sources and sinks in land ecosystems of the conterminous United States for the contemporary period of 2001–2005 and over the last three centuries. We estimate that land ecosystems in the conterminous United States sequestered 323 Tg C yr−1 at the beginning of the 21st century with forests accounting for 97% of this sink. This land carbon sink varied substantially across the conterminous United States, with the largest sinks occurring in the Southeast. Land sinks are large enough to completely compensate fossil fuel emissions in Maine and Mississippi, but nationally, carbon sinks compensate for only 20% of U.S. fossil fuel emissions. We find that regions that are currently large carbon sinks (e.g., Southeast) tend to have been large carbon sources over the longer historical period. Both the land use history and fate of harvested products can be important in determining a region's overall impact on the atmospheric carbon budget. While there are numerous options for reducing fossil fuels (e.g., increase efficiency and displacement by renewable resources), new land management opportunities for sequestering carbon need to be explored. Opportunities include reforestation and managing forest age structure. These opportunities will vary from state to state and over time across the United States.
    Description: This work was supported by NSF grants 104918, 1137306, and 1237491; EPA grant XA-83600001-1; and DOE grant DE-FG02-94ER61937.
    Description: 2015-08-28
    Keywords: Carbon cycle ; Land carbon sinks ; Land use and land cover change ; Stand age ; Fossil fuel emissions ; Land use legacies
    Repository Name: Woods Hole Open Access Server
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  • 18
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    Global assessment of ocean carbon export by combining satellite observations and food-web models (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 28 (2014): 181-196, doi:10.1002/2013GB004743.
    Description: The export of organic carbon from the surface ocean by sinking particles is an important, yet highly uncertain, component of the global carbon cycle. Here we introduce a mechanistic assessment of the global ocean carbon export using satellite observations, including determinations of net primary production and the slope of the particle size spectrum, to drive a food-web model that estimates the production of sinking zooplankton feces and algal aggregates comprising the sinking particle flux at the base of the euphotic zone. The synthesis of observations and models reveals fundamentally different and ecologically consistent regional-scale patterns in export and export efficiency not found in previous global carbon export assessments. The model reproduces regional-scale particle export field observations and predicts a climatological mean global carbon export from the euphotic zone of ~6 Pg C yr−1. Global export estimates show small variation (typically 〈 10%) to factor of 2 changes in model parameter values. The model is also robust to the choices of the satellite data products used and enables interannual changes to be quantified. The present synthesis of observations and models provides a path for quantifying the ocean's biological pump.
    Description: D.A.S. and K.O.B. acknowledge support from the National Aeronautics and Space Administration (NNX11AF63G). S.C.D. and S.F.S. acknowledge support from the National Science Foundation through the Center for Microbial Oceanography: Research and Education (C-MORE) (NSF EF-0424599).
    Description: 2014-09-10
    Keywords: Carbon cycle ; Biological pump ; Carbon export ; Remote sensing ; Food webs
    Repository Name: Woods Hole Open Access Server
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  • 19
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    Tectonically-triggered sediment and carbon export to the Hadal zone (2018)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 121, doi:10.1038/s41467-017-02504-1.
    Description: Sediments in deep ocean trenches may contain crucial information on past earthquake history and constitute important sites of carbon burial. Here we present 14C data on bulk organic carbon (OC) and its thermal decomposition fractions produced by ramped pyrolysis/oxidation for a core retrieved from the 〉7.5 km-deep Japan Trench. High-resolution 14C measurements, coupled with distinctive thermogram characteristics of OC, reveal hemipelagic sedimentation interrupted by episodic deposition of pre-aged OC in the trench. Low δ13C values and diverse 14C ages of thermal fractions imply that the latter material originates from the adjacent margin, and the co-occurrence of pre-aged OC with intervals corresponding to known earthquake events implies tectonically triggered, gravity-flow-driven supply. We show that 14C ages of thermal fractions can yield valuable chronological constraints on sedimentary sequences. Our findings shed new light on links between tectonically driven sedimentological processes and marine carbon cycling, with implications for carbon dynamics in hadal environments.
    Description: This study is supported by Doc.Mobility Fellowship (P1EZP2_159064) (R.B.) from the Swiss National Science Foundation (SNSF). This work is also supported by SNF “CAPS-LOCK” project 200021_140850 (T.I.E.), by SNSF grant (133481) (M.S.), and Austrian Science Foundation (P 29678-N28) (M.S.).
    Keywords: Carbon cycle ; Sedimentology
    Repository Name: Woods Hole Open Access Server
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    Nonuniform ocean acidification and attenuation of the ocean carbon sink (2017)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 44 (2017): 8404–8413, doi:10.1002/2017GL074389.
    Description: Surface ocean carbon chemistry is changing rapidly. Partial pressures of carbon dioxide gas (pCO2) are rising, pH levels are declining, and the ocean's buffer capacity is eroding. Regional differences in short-term pH trends primarily have been attributed to physical and biological processes; however, heterogeneous seawater carbonate chemistry may also be playing an important role. Here we use Surface Ocean CO2 Atlas Version 4 data to develop 12 month gridded climatologies of carbonate system variables and explore the coherent spatial patterns of ocean acidification and attenuation in the ocean carbon sink caused by rising atmospheric pCO2. High-latitude regions exhibit the highest pH and buffer capacity sensitivities to pCO2 increases, while the equatorial Pacific is uniquely insensitive due to a newly defined aqueous CO2 concentration effect. Importantly, dissimilar regional pH trends do not necessarily equate to dissimilar acidity ([H+]) trends, indicating that [H+] is a more useful metric of acidification.
    Description: 2018-02-16
    Keywords: Ocean acidification ; Carbon sink ; Revelle factor ; Carbon cycle
    Repository Name: Woods Hole Open Access Server
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