Letters

  • Letter |

    Cement production is a source of CO2. Analysis of carbonation, a process that sequesters CO2 during the lifetime of cement, suggests that between 1930 and 2013, it has offset 43% of CO2 emissions from cement production globally.

    • Fengming Xi
    • , Steven J. Davis
    • , Philippe Ciais
    • , Douglas Crawford-Brown
    • , Dabo Guan
    • , Claus Pade
    • , Tiemao Shi
    • , Mark Syddall
    • , Jie Lv
    • , Lanzhu Ji
    • , Longfei Bing
    • , Jiaoyue Wang
    • , Wei Wei
    • , Keun-Hyeok Yang
    • , Björn Lagerblad
    • , Isabel Galan
    • , Carmen Andrade
    • , Ying Zhang
    •  & Zhu Liu
  • Letter |

    Organic matter represents a large pool of carbon in the ocean. Radiocarbon and chemical analyses suggest that larger particles are preferentially remineralized in the Pacific Ocean, with smaller particles and molecules persisting longer.

    • Brett D. Walker
    • , Steven R. Beaupré
    • , Thomas P. Guilderson
    • , Matthew D. McCarthy
    •  & Ellen R. M. Druffel
  • Letter |

    A lot of methane is emitted from oxygenated seawater, where its production should be inhibited. Seawater incubations and organic matter characterizations reveal that bacteria aerobically produce methane from phosphonates in organic matter.

    • Daniel J. Repeta
    • , Sara Ferrón
    • , Oscar A. Sosa
    • , Carl G. Johnson
    • , Lucas D. Repeta
    • , Marianne Acker
    • , Edward F. DeLong
    •  & David M. Karl
  • Letter |

    Cloud feedbacks strongly influence the magnitude of global warming. Climate model simulations show that these feedbacks vary strongly as the spatial patterns of sea surface temperatures change over time.

    • Chen Zhou
    • , Mark D. Zelinka
    •  & Stephen A. Klein
  • Letter |

    The late Palaeozoic was marked by a series of glacial–interglacial cycles. Geochemical and fossil data suggest a role for terrestrial vegetation–carbon cycle feedbacks in the climate response to orbital forcing.

    • Isabel P. Montañez
    • , Jennifer C. McElwain
    • , Christopher J. Poulsen
    • , Joseph D. White
    • , William A. DiMichele
    • , Jonathan P. Wilson
    • , Galen Griggs
    •  & Michael T. Hren
  • Letter |

    The North Atlantic Oscillation profoundly influences European and North American winter weather. Dynamical model predictions now exhibit skill in prediction of the winter North Atlantic Oscillation more than one year in advance.

    • Nick Dunstone
    • , Doug Smith
    • , Adam Scaife
    • , Leon Hermanson
    • , Rosie Eade
    • , Niall Robinson
    • , Martin Andrews
    •  & Jeff Knight
  • Letter |

    Links between subduction zone earthquakes and slow slip on the plate interface are unclear. Reconstructions of a slow slip event in the Guerrero subduction zone segment, in Mexico, suggest that the event triggered the 2014 Papanoa earthquake.

    • M. Radiguet
    • , H. Perfettini
    • , N. Cotte
    • , A. Gualandi
    • , B. Valette
    • , V. Kostoglodov
    • , T. Lhomme
    • , A. Walpersdorf
    • , E. Cabral Cano
    •  & M. Campillo
  • Letter |

    The planet Mercury has contracted over its history. The identification of small thrust fault scarps suggests the occurrence of tectonic activity on Mercury within the past 50 million years and thus a slow-cooling planetary interior.

    • Thomas R. Watters
    • , Katie Daud
    • , Maria E. Banks
    • , Michelle M. Selvans
    • , Clark R. Chapman
    •  & Carolyn M. Ernst
  • Letter |

    Life at ocean depths below 100 m requires organic carbon from the upper ocean. Analyses of satellite and Argo-float data reveal that seasonal changes in mixed-layer depth supply substantial amounts of carbon to this deep and dark ecosystem.

    • Giorgio Dall'Olmo
    • , James Dingle
    • , Luca Polimene
    • , Robert J. W. Brewin
    •  & Hervé Claustre
  • Letter |

    Little is known about the character of the Hadean crust. Geochemical analyses of the 4-billion-year-old Acasta Gneiss from Canada suggest Earth’s earliest crust formed from a mafic reservoir, similar to the formation of oceanic crust today.

    • J. R. Reimink
    • , J. H. F. L. Davies
    • , T. Chacko
    • , R. A. Stern
    • , L. M. Heaman
    • , C. Sarkar
    • , U. Schaltegger
    • , R. A. Creaser
    •  & D. G. Pearson
  • Letter |

    The Earth’s outermost core is thought to be stratified. Turbulent mixing experiments suggest that merging between the cores of projectile and planet following the Moon-forming giant impact could have produced the stratification.

    • Maylis Landeau
    • , Peter Olson
    • , Renaud Deguen
    •  & Benjamin H. Hirsh
  • Letter |

    Aquatic CO2 emissions are expected to increase if warming reduces photosynthesis relative to respiration. An analysis of streams across a 41 °C temperature gradient reveals that the thermal responses of respiration and photosynthesis are similar.

    • Benoît O. L. Demars
    • , Gísli M. Gíslason
    • , Jón S. Ólafsson
    • , J. Russell Manson
    • , Nikolai Friberg
    • , James M. Hood
    • , Joshua J. D. Thompson
    •  & Thomas E. Freitag
  • Letter |

    The internal dynamics of pyroclastic density currents are not easily observed. Experiments reveal how the underflow and turbulent ash-cloud regimes within pyroclastic flows are dynamically coupled through a zone of intermediate turbulence.

    • Eric C. P. Breard
    • , Gert Lube
    • , Jim R. Jones
    • , Josef Dufek
    • , Shane J. Cronin
    • , Greg A. Valentine
    •  & Anja Moebis
  • Letter |

    Increasing groundwater abstraction in the Indo-Gangetic Basin poses a threat to groundwater supplies. In situ observations reveal that sustainable groundwater in much of the region is limited more by contamination than depletion.

    • A. M. MacDonald
    • , H. C. Bonsor
    • , K. M. Ahmed
    • , W. G. Burgess
    • , M. Basharat
    • , R. C. Calow
    • , A. Dixit
    • , S. S. D. Foster
    • , K. Gopal
    • , D. J. Lapworth
    • , R. M. Lark
    • , M. Moench
    • , A. Mukherjee
    • , M. S. Rao
    • , M. Shamsudduha
    • , L. Smith
    • , R. G. Taylor
    • , J. Tucker
    • , F. van Steenbergen
    •  & S. K. Yadav
  • Letter |

    Convective precipitation may change in a changing climate. Large eddy simulations of convection with a realistic diurnal cycle suggest that interactions between convective systems and precipitation extremes are influenced by temperature.

    • Christopher Moseley
    • , Cathy Hohenegger
    • , Peter Berg
    •  & Jan O. Haerter
  • Letter |

    The composition of subduction zone lavas varies systematically. Numerical simulations and geochemical analysis of lavas from the Chilean Southern Volcanic Zone suggest that the thermal structure of the mantle wedge controls lava composition.

    • Stephen J. Turner
    • , Charles H. Langmuir
    • , Richard F. Katz
    • , Michael A. Dungan
    •  & Stéphane Escrig
  • Letter |

    Biomass turnover time is a key parameter in the global carbon cycle. An analysis of global land-use data reveals that biomass turnover is almost twice as fast when the land is used to enhance terrestrial ecosystem services.

    • Karl-Heinz Erb
    • , Tamara Fetzel
    • , Christoph Plutzar
    • , Thomas Kastner
    • , Christian Lauk
    • , Andreas Mayer
    • , Maria Niedertscheider
    • , Christian Körner
    •  & Helmut Haberl
  • Letter |

    Warming thaws permafrost, releasing carbon that can cause more warming. Radiocarbon, soil carbon, and remote sensing data suggest that 0.2–2.5 Pg of carbon has been emitted from permafrost as CO2 and CH4 around Arctic lakes since the 1950s.

    • Katey Walter Anthony
    • , Ronald Daanen
    • , Peter Anthony
    • , Thomas Schneider von Deimling
    • , Chien-Lu Ping
    • , Jeffrey P. Chanton
    •  & Guido Grosse
  • Letter |

    Rivers transport terrestrial organic carbon. Ancient molecular markers of methanogens and radiocarbon data from offshore sediments suggest that much of this carbon in the Congo River is aged, and that hydrology controls the amount transported.

    • Enno Schefuß
    • , Timothy I. Eglinton
    • , Charlotte L. Spencer-Jones
    • , Jürgen Rullkötter
    • , Ricardo De Pol-Holz
    • , Helen M. Talbot
    • , Pieter M. Grootes
    •  & Ralph R. Schneider
  • Letter |

    Most oceanic crust is subducted back into Earth’s mantle within 200 million years of formation. Analysis of magnetic data from the eastern Mediterranean reveals oceanic crust formed up to 340 million years ago, as part of an ancient ocean basin.

    • Roi Granot
  • Letter |

    The Moon has a tenuous exosphere and dust-sized particles have been detected. Analysis of spectral observations by the LADEE spacecraft suggests that the Moon also has a spatially and temporally variable exosphere of nanodust particles.

    • D. H. Wooden
    • , A. M. Cook
    • , A. Colaprete
    • , D. A. Glenar
    • , T. J. Stubbs
    •  & M. Shirley
  • Letter |

    Whether fast and slow earthquakes nucleate in the same way is unclear. Laboratory simulations of fast and slow slip reveal similar precursor seismic signals for both modes, suggesting the same physical mechanisms may govern both types of slip.

    • M. M. Scuderi
    • , C. Marone
    • , E. Tinti
    • , G. Di Stefano
    •  & C. Collettini
  • Letter |

    Land carbon uptake reduced atmospheric CO2 levels during the Little Ice Age. Numerical simulations of atmospheric carbonyl sulfide levels and ice-core carbon isotope data reveal that temperature change, not land-cover change, was responsible.

    • M. Rubino
    • , D. M. Etheridge
    • , C. M. Trudinger
    • , C. E. Allison
    • , P. J. Rayner
    • , I. Enting
    • , R. Mulvaney
    • , L. P. Steele
    • , R. L. Langenfelds
    • , W. T. Sturges
    • , M. A. J. Curran
    •  & A. M. Smith
  • Letter |

    Laurentide ice-sheet retreat continued into the mid-Holocene. Speleothem-based precipitation records suggest the cessation of melt led to the establishment of the present precipitation patterns associated with the North Atlantic Oscillation.

    • Jasper A. Wassenburg
    • , Stephan Dietrich
    • , Jan Fietzke
    • , Jens Fohlmeister
    • , Klaus Peter Jochum
    • , Denis Scholz
    • , Detlev K. Richter
    • , Abdellah Sabaoui
    • , Christoph Spötl
    • , Gerrit Lohmann
    • , Meinrat O. Andreae
    •  & Adrian Immenhauser
  • Letter |

    Earth’s crust diverges and extends along mid-ocean ridges. Analyses of gravity and seismic data from the equatorial Atlantic show that propagation of ridge segments can compress the crust and create sufficient uplift to create small islands.

    • Marcia Maia
    • , Susanna Sichel
    • , Anne Briais
    • , Daniele Brunelli
    • , Marco Ligi
    • , Nicolas Ferreira
    • , Thomas Campos
    • , Bérengère Mougel
    • , Isa Brehme
    • , Christophe Hémond
    • , Akihisa Motoki
    • , Denise Moura
    • , Carla Scalabrin
    • , Ivo Pessanha
    • , Eliane Alves
    • , Arthur Ayres
    •  & Pedro Oliveira
  • Letter |

    It is unclear whether subduction is still active beneath the Indo-Burman mountain range. Analyses of GPS measurements from this region reveal a locked megathrust fault, implying that subduction is active and could generate a large earthquake.

    • Michael S. Steckler
    • , Dhiman Ranjan Mondal
    • , Syed Humayun Akhter
    • , Leonardo Seeber
    • , Lujia Feng
    • , Jonathan Gale
    • , Emma M. Hill
    •  & Michael Howe
  • Letter |

    Mars has two small moons that may have formed in the aftermath of a giant impact. Simulations suggest that Phobos and Deimos accreted from the disperse outer region of the debris disc that was stirred up by short-lived larger moons.

    • Pascal Rosenblatt
    • , Sébastien Charnoz
    • , Kevin M. Dunseath
    • , Mariko Terao-Dunseath
    • , Antony Trinh
    • , Ryuki Hyodo
    • , Hidenori Genda
    •  & Stéven Toupin
  • Letter |

    Sea-ice formation is a key factor in the lower branch of the Southern Ocean overturning circulation. Observation-based data in conjunction with a water-mass transformation framework reveal that sea ice plays a central role in the upper branch too.

    • Ryan P. Abernathey
    • , Ivana Cerovecki
    • , Paul R. Holland
    • , Emily Newsom
    • , Matt Mazloff
    •  & Lynne D. Talley
  • Letter |

    Vertical crustal motions during the earthquake cycle are poorly constrained for strike–slip faults. Analysis of GPS data from the San Andreas Fault shows that the crust flexes over hundreds of kilometres due to locking of the fault at depth.

    • Samuel Howell
    • , Bridget Smith-Konter
    • , Neil Frazer
    • , Xiaopeng Tong
    •  & David Sandwell
  • Letter |

    Atmospheric non-methane hydrocarbon concentrations began declining in the 1970s. Surface and column measurements show that Northern Hemisphere ethane concentrations are now rising, probably due to North American oil and natural gas emissions.

    • Detlev Helmig
    • , Samuel Rossabi
    • , Jacques Hueber
    • , Pieter Tans
    • , Stephen A. Montzka
    • , Ken Masarie
    • , Kirk Thoning
    • , Christian Plass-Duelmer
    • , Anja Claude
    • , Lucy J. Carpenter
    • , Alastair C. Lewis
    • , Shalini Punjabi
    • , Stefan Reimann
    • , Martin K. Vollmer
    • , Rainer Steinbrecher
    • , James W. Hannigan
    • , Louisa K. Emmons
    • , Emmanuel Mahieu
    • , Bruno Franco
    • , Dan Smale
    •  & Andrea Pozzer
  • Letter |

    Great Himalayan earthquakes are rare. Analysis of surface motions in the months after the 2015 Gorkha earthquake reveals negligible aseismic slip, implying that stress may be stored in the crust to be tapped during future great earthquakes.

    • David Mencin
    • , Rebecca Bendick
    • , Bishal Nath Upreti
    • , Danda Pani Adhikari
    • , Ananta Prasad Gajurel
    • , Roshan Raj Bhattarai
    • , Hari Ram Shrestha
    • , Tara Nidhi Bhattarai
    • , Niraj Manandhar
    • , John Galetzka
    • , Ellen Knappe
    • , Beth Pratt-Sitaula
    • , Abdelkrim Aoudia
    •  & Roger Bilham
  • Letter |

    The mid-1990s’ warming of the North Atlantic subpolar gyre was probably related to strengthened overturning. Observations and numerical models suggest that a climate reversal to a cooling trend occurred around 2005.

    • Jon Robson
    • , Pablo Ortega
    •  & Rowan Sutton
  • Letter |

    Eastern boundary coastal upwelling systems are locations of high ocean productivity. Numerical simulations reveal that wind alters current- and eddy-driven nutrient supply, which affects net primary productivity in the California Current system.

    • Lionel Renault
    • , Curtis Deutsch
    • , James C. McWilliams
    • , Hartmut Frenzel
    • , Jun-Hong Liang
    •  & François Colas
  • Letter |

    Sulfur dioxide is a key air contaminant. A satellite-based emissions inventory reveals a number of hitherto unknown sources, with a cluster around the Persian Gulf, and identifies large discrepancies with conventional inventories in some regions.

    • Chris A. McLinden
    • , Vitali Fioletov
    • , Mark W. Shephard
    • , Nick Krotkov
    • , Can Li
    • , Randall V. Martin
    • , Michael D. Moran
    •  & Joanna Joiner
  • Letter |

    An energetic process is needed to convert N2 into compounds essential for life. Simulations show that interactions between powerful solar flares and Earth’s magnetic field could have facilitated nitrogen fixation in the early atmosphere.

    • V. S. Airapetian
    • , A. Glocer
    • , G. Gronoff
    • , E. Hébrard
    •  & W. Danchi