• Issue

    Global Biogeochemical Cycles: Volume 34, Issue 2

    February 2020
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ISSUE INFORMATION

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Issue Information

  • First Published: 07 February 2020

Research Articles

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The Distribution and Redox Speciation of Iodine in the Eastern Tropical North Pacific Ocean

Rintaro Moriyasu,  Natalya Evans,  Kenneth M. Bolster,  Dalton S. Hardisty,  James W. Moffett, 
  • First Published: 28 January 2020
Key Points

  • The Eastern Tropical North Pacific oxygen deficient zone is strongly enriched in iodide relative to iodate
  • Enriched iodide indicates robust transport from shelf sediments to the interior basin
  • Similarity to oxygen deficient zones in the Eastern Tropic South Pacific and Arabian Sea reveals importance of common processes

Feature Article

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Evolution of the Global Carbon Cycle and Climate Regulation on Earth

T. T. Isson,  N. J. Planavsky,  L. A. Coogan,  E. M. Stewart,  J. J. Ague,  E. W. Bolton,  S. Zhang,  N. R. McKenzie,  L. R. Kump, 
  • First Published: 30 December 2019
Key Points

  • Long term carbon sources and sinks are likely larger than traditional envisioned
  • There is significant silicate weathering in the marine as well as terrestrial settings
  • Ocean oxygenation and evolution of a biotic Si cycle forced a drop in reverse weathering rates and an increase in marine weathering rates

Research Articles

Free Access

A Synthesis of Blue Carbon Stocks, Sources, and Accumulation Rates in Eelgrass (Zostera marina) Meadows in the Northeast Pacific

C. Prentice,  K. L. Poppe,  M. Lutz,  E. Murray,  T. A. Stephens,  A. Spooner,  M. Hessing-Lewis,  R. Sanders-Smith,  J. M. Rybczyk,  J. Apple,  F. T. Short,  J. Gaeckle,  A. Helms,  C. Mattson,  W. W. Raymond,  T. Klinger, 
  • First Published: 05 January 2020
Key Points

  • Sediment carbon content varied both within and among Northeast Pacific eelgrass meadows, yet there was no clear latitudinal trend
  • Carbon in eelgrass meadow sediments appears to be derived largely from noneelgrass sources
  • Northeast Pacific carbon stocks and accumulation rates are comparable to other Z. marina meadows but lower than global seagrass values

Free Access

Carbon Deposition and Burial in Estuarine Sediments of the Contiguous United States

J. A. Hutchings,  T. S. Bianchi,  R. G. Najjar,  M. Herrmann,  W. M. Kemp,  A. L. Hinson,  R. A. Feagin, 
  • First Published: 16 January 2020
Key Points

  • Sedimentation processes in estuaries within the contiguous United States are estimated to deposit 11.3 [8.5–15.2, 95% confidence] Tg of carbon per year
  • Remineralization liberates a significant portion of deposited carbon, yielding centennial-scale burial of 4.5 [3.1–6.8, 95% confidence] Tg carbon per year
  • Estuaries of the contiguous United States are classified into six clusters based on geospatial and biogeochemical characteristics using k-means analysis

Free Access

Tidal Wetland Gross Primary Production Across the Continental United States, 2000–2019

R. A. Feagin,  I. Forbrich,  T. P. Huff,  J. G. Barr,  J. Ruiz-Plancarte,  J. D. Fuentes,  R. G. Najjar,  R. Vargas,  A. Vázquez-Lule,  L. Windham-Myers,  K. D. Kroeger,  E. J. Ward,  G. W. Moore,  M. Leclerc,  K. W. Krauss,  C. L. Stagg,  M. Alber,  S. H. Knox,  K. V. R. Schäfer,  T. S. Bianchi,  J. A. Hutchings,  H. Nahrawi,  A. Noormets,  B. Mitra,  A. Jaimes,  A. L. Hinson,  B. Bergamaschi,  J. S. King,  G. Miao, 
  • First Published: 24 January 2020
Key Points

  • We created the Blue Carbon (BC) model, which mapped the Gross Primary Production (GPP) of all tidal wetlands within the continental United States
  • The BC model provides maps of tidal wetland GPP at sub-250 m scales and at 16-day intervals for the years 2000-2019
  • The average daily GPP per m2 was 4.32 ± 2.45 g C/m2/day, and the total annual GPP for the continental United States was 39.65 ± 0.89 Tg C/year

Free Access

An Investigation Into the Origin of Nitrate in Arctic Sea Ice

S. C. Clark,  J. Granger,  A. Mastorakis,  A. Aguilar-Islas,  M. G. Hastings, 
  • First Published: 03 February 2020
Key Points

  • Concentration and stable isotopes of N species in samples from the Arctic U.S. GEOTRACES section help constrain the atmospheric contribution
  • Uncycled atmospheric nitrate accounted for 40% or less of sea ice nitrate, while biologically sourced nitrate accounted for at least 60%
  • Nitrate in late-summer sea ice contains an exogenous source of reactive N that could contribute to N-deplete waters in the western Arctic

Free Access

A Global Model for Methylmercury Formation and Uptake at the Base of Marine Food Webs

Yanxu Zhang,  Anne L. Soerensen,  Amina T. Schartup,  Elsie M. Sunderland, 
  • First Published: 03 February 2020
Key Points

  • A new global ocean model for methylmercury formation and plankton food web dynamics is developed
  • Important drivers are identified: substrate availability, microbial activity, shortwave radiation, community structure, and temperature
  • The model developed in this study provides a quantitative framework for evaluation of the impact of climate change

Free Access

Origin and Accumulation of an Anthropogenic CO2 and 13C Suess Effect in the Arctic Ocean

Young Ho Ko,  Paul D. Quay, 
  • First Published: 04 February 2020
Key Points

  • We estimated an anthropogenic CO2 accumulation and δ13C decrease that extends to ~2,000 m in the Arctic Ocean since preindustrial times
  • The primary source of anthropogenic CO2 and δ13C change occurs via an input of intermediate water originating in the North Atlantic
  • The δ13C change in halocline waters occurs via North Pacific input as indicated by distinct δ13C signature from that in intermediate waters

Open Access

A Cross-System Comparison of Dark Carbon Fixation in Coastal Sediments

Diana Vasquez-Cardenas,  Filip J. R. Meysman,  Henricus T. S. Boschker, 
  • First Published: 06 February 2020
Key Points

  • Coastal dark carbon fixation rates are highest in diffusion-driven intertidal areas and lowest in permeable continental shelf sediments
  • Pore water transport and microbial sulfur oxidation mechanisms determine five depth distribution models of dark carbon fixation in sediments
  • The renewal of labile organic matter by dark carbon fixation is important in coastal carbon budgets

Open Access

Sources of Uncertainty in Regional and Global Terrestrial CO2 Exchange Estimates

A. Bastos,  M. O'Sullivan,  P. Ciais,  D. Makowski,  S. Sitch,  P. Friedlingstein,  F. Chevallier,  C. Rödenbeck,  J. Pongratz,  I. T. Luijkx,  P. K. Patra,  P. Peylin,  J. G. Canadell,  R. Lauerwald,  W. Li,  N. E. Smith,  W. Peters,  D. S. Goll,  A.K. Jain,  E. Kato,  S. Lienert,  D. L. Lombardozzi,  V. Haverd,  J. E. M. S. Nabel,  B. Poulter,  H. Tian,  A. P. Walker,  S. Zaehle, 
  • First Published: 07 February 2020
Key Points

  • Top-down and bottom-up estimates of net land-atmosphere CO urn:x-wiley:gbc:media:gbc20956:gbc20956-math-0004 fluxes agree well globally but show important mismatches at regional scales
  • Regional mismatches are dominated by differences between inversions and interannual variability in CO urn:x-wiley:gbc:media:gbc20956:gbc20956-math-0005 fluxes
  • Mismatches between top-down and bottom-up data sets are explained by sensitivity to climate and by uncertainty in land use change forcing

Free Access

A Spatially Explicit, Empirical Estimate of Tree-Based Biological Nitrogen Fixation in Forests of the United States

Anika Staccone,  Wenying Liao,  Steven Perakis,  Jana Compton,  Christopher M. Clark,  Duncan Menge, 
  • First Published: 07 February 2020
Key Points

  • N-fixing trees in the temperate United States contribute less reactive N than previously thought
  • Alnus and Robinia fix the majority of tree-based N fixation in the United States
  • The flux of fixed N from trees is similar to that from understory plants or asymbiotic fixers across the United States

Comments

Free Access

Comment on “Absence of Age-Related Trends in Stable Oxygen Isotope Ratios From Oak Tree Rings” by Duffy et al. (2019)

S. Helama,  V. V. Matskovsky, 
  • First Published: 26 January 2020
Key Points

  • The Regional Curve Standardization should not be neglected in efforts to assess nonclimatic, age-related trends in any tree-ring data
  • The effects of data heterogeneity for curve estimation can be considerably reduced by increasing the sample size of tree-ring series
  • More testing with larger sample size and using the existing tree-ring methods is needed for detailed assessments of age-related trends

Replies

Open Access

Reply to Comment by S. Helama and V. V. Matskovsky on“Absence of Age-Related Trends in Stable Oxygen Isotope Ratios From Oak Tree Rings”

Danny McCarroll,  Josie E. Duffy,  Neil J. Loader,  Giles H.F. Young,  Darren Davies,  Daniel Miles,  Christopher Bronk Ramsey, 
  • First Published: 26 January 2020
Key Point

  • There is no evidence for age trends in the stable oxygen isotope ratios and thus no need for de-trending of any kind