Air-sea disequilibrium enhances ocean carbon storage during glacial periods

Temperature and iron fertilization are more important in driving glacial-interglacial CO2 cycles than previously thought. The prevailing hypothesis for lower atmospheric carbon dioxide (CO2) concentrations during glacial periods is an increased efficiency of the ocean’s biological pump. However, tests of this and other hypotheses have been hampered by the difficulty to accurately quantify ocean carbon components. Here, we use an observationally constrained earth system model to precisely quantify these components and the role that different processes play in simulated glacial-interglacial CO2 variations. We find that air-sea disequilibrium greatly amplifies the effects of cooler temperatures and iron fertilization on glacial ocean carbon storage even as the efficiency of the soft-tissue biological pump decreases. These two processes, which have previously been regarded as minor, explain most of our simulated glacial CO2 drawdown, while ocean circulation and sea ice extent, hitherto considered dominant, emerge as relatively small contributors.

[1]  E. Galbraith,et al.  Carbon burial in deep-sea sediment and implications for oceanic inventories of carbon and alkalinity over the last glacial cycle , 2018, Climate of the Past.

[2]  B. Bostick,et al.  Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods , 2018, Proceedings of the National Academy of Sciences.

[3]  S. Riser,et al.  Autonomous Biogeochemical Floats Detect Significant Carbon Dioxide Outgassing in the High‐Latitude Southern Ocean , 2018, Geophysical Research Letters.

[4]  A. Schmittner,et al.  Weak overturning circulation and high Southern Ocean nutrient utilization maximized glacial ocean carbon , 2018, Earth and Planetary Science Letters.

[5]  E. Galbraith,et al.  The devil's in the disequilibrium: multi-component analysis of dissolved carbon and oxygen changes under a broad range of forcings in a general circulation model , 2018, Biogeosciences.

[6]  J. Jouzel,et al.  Asynchrony between Antarctic temperature and CO2 associated with obliquity over the past 720,000 years , 2018, Nature Communications.

[7]  J. Severinghaus,et al.  Mean global ocean temperatures during the last glacial transition , 2018, Nature.

[8]  A. Schmittner,et al.  Combined Effects of Atmospheric and Seafloor Iron Fluxes to the Glacial Ocean , 2017 .

[9]  J. Sarmiento,et al.  Oxygen in the Southern Ocean From Argo Floats: Determination of Processes Driving Air‐Sea Fluxes , 2017 .

[10]  I. N. McCave,et al.  Radiocarbon constraints on the glacial ocean circulation and its impact on atmospheric CO2 , 2017, Nature Communications.

[11]  A. Oschlies,et al.  Evaluation of the transport matrix method for simulation of ocean biogeochemical tracers , 2017 .

[12]  G. Haug,et al.  Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age , 2017, Proceedings of the National Academy of Sciences.

[13]  S. Riser,et al.  In situ phase-domain calibration of oxygen Optodes on profiling floats , 2016 .

[14]  Jacqueline Boutin,et al.  A multi-decade record of high-quality fCO2 data in version 3 of the Surface Ocean CO2 Atlas (SOCAT) , 2016 .

[15]  R. Gersonde,et al.  Last Glacial Maximum sea surface temperature and sea-ice extent in the Pacific sector of the Southern Ocean , 2016 .

[16]  A. Schmittner,et al.  Complementary constraints from carbon (13C) and nitrogen (15N) isotopes on the glacial ocean's soft‐tissue biological pump , 2016 .

[17]  C. Hillenbrand,et al.  Oxygen depletion recorded in upper waters of the glacial Southern Ocean , 2016, Nature Communications.

[18]  A. Schmittner,et al.  Wind Stress Increases Glacial Atlantic Overturning , 2015 .

[19]  A. Schmittner,et al.  Glacial Atlantic overturning increased by wind stress in climate models , 2015 .

[20]  K. Lambeck,et al.  Ice-sheet configuration in the CMIP5/PMIP3 Last Glacial Maximum experiments , 2015 .

[21]  A. Watson,et al.  Southern Ocean buoyancy forcing of ocean ventilation and glacial atmospheric CO2 , 2015 .

[22]  L. Gallardo,et al.  Dust fluxes and iron fertilization in Holocene and Last Glacial Maximum climates , 2015 .

[23]  E. Galbraith,et al.  Deglacial weakening of the oceanic soft tissue pump: global constraints from sedimentary nitrogen isotopes and oxygenation proxies , 2015 .

[24]  L. Lisiecki,et al.  Deglacial whole‐ocean δ13C change estimated from 480 benthic foraminiferal records , 2014 .

[25]  M. Follows,et al.  Air‐sea disequilibrium of carbon dioxide enhances the biological carbon sequestration in the Southern Ocean , 2013 .

[26]  A. Oschlies,et al.  A novel estimate of ocean oxygen utilisation points to a reduced rate of respiration in the ocean interior , 2013 .

[27]  Michael Sarnthein,et al.  Peak glacial 14 C ventilation ages suggest major draw-down of carbon into the abyssal ocean , 2013 .

[28]  Andy Ridgwell,et al.  Glacial-Interglacial Variability in Atmospheric CO2 , 2013 .

[29]  W. Broecker,et al.  Is There a Tie between Atmosphere CO2 Content and Ocean Circulation , 2013 .

[30]  Tyler Volk,et al.  Ocean Carbon Pumps: Analysis of Relative Strengths and Efficiencies in Ocean‐Driven Atmospheric CO2 Changes , 2013 .

[31]  L. Yi,et al.  Last Glacial Maximum Sea Surface Temperatures: A Model-Data Comparison , 2013 .

[32]  H. Renssen,et al.  Evaluating Southern Ocean sea-ice for the Last Glacial Maximum and pre-industrial climates: PMIP-2 models and data evidence , 2012 .

[33]  M. Holzer,et al.  Ventilation of the deep ocean constrained with tracer observations and implications for radiocarbon estimates of ideal mean age , 2012 .

[34]  J. Toggweiler,et al.  The control of atmospheric pCO2 by ocean ventilation change: The effect of the oceanic storage of biogenic carbon , 2011 .

[35]  M. Follows,et al.  Ocean Dynamics and the Carbon Cycle: Principles and Mechanisms , 2011 .

[36]  A. Abe‐Ouchi,et al.  Mechanisms controlling export production at the LGM: Effects of changes in oceanic physical fields and atmospheric dust deposition , 2011 .

[37]  G. Haug,et al.  Carbon dioxide effects of Antarctic stratification, North Atlantic Intermediate Water formation, and subantarctic nutrient drawdown during the last ice age: Diagnosis and synthesis in a geochemical box model , 2010 .

[38]  G. Haug,et al.  The polar ocean and glacial cycles in atmospheric CO2 concentration , 2010, Nature.

[39]  K. Matsumoto,et al.  Effects of sea ice on atmospheric pCO2: A revised view and implications for glacial and future climates , 2010 .

[40]  Jean-Claude Dutay,et al.  Quantifying the roles of ocean circulation and biogeochemistry in governing ocean carbon-13 and atmospheric carbon dioxide at the last glacial maximum , 2009 .

[41]  M. Weinelt,et al.  Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum: report of the MARGO Project , 2009 .

[42]  J. Toggweiler,et al.  Impact of oceanic circulation on biological carbon storage in the ocean and atmospheric pCO2 , 2008 .

[43]  J. Sarmiento,et al.  How does ocean biology affect atmospheric pCO2? Theory and models , 2008 .

[44]  V. Brovkin,et al.  Lowering of glacial atmospheric CO2 in response to changes in oceanic circulation and marine biogeochemistry , 2007 .

[45]  E. Galbraith,et al.  Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction , 2007 .

[46]  Samar Khatiwala,et al.  A computational framework for simulation of biogeochemical tracers in the ocean , 2007 .

[47]  Michael J. Follows,et al.  Preformed phosphate, soft tissue pump and atmospheric CO 2 , 2005 .

[48]  M. Prange,et al.  Radiocarbon simulations for the glacial ocean: The effects of wind stress, Southern Ocean sea ice and Heinrich events , 2005 .

[49]  Corinne Le Quéré,et al.  Role of Marine Biology in Glacial-Interglacial CO2 Cycles , 2005, Science.

[50]  Richard A. Feely,et al.  A global ocean carbon climatology: Results from Global Data Analysis Project (GLODAP) , 2004 .

[51]  E. Boyle,et al.  Is AOU a good measure of respiration in the oceans? , 2004, Geophysical Research Letters.

[52]  Andrew G. Dickson,et al.  Variability in oxygen and nutrients in South Pacific Antarctic Intermediate Water , 2003 .

[53]  Corinne Le Quéré,et al.  Dust impact on marine biota and atmospheric CO2 in glacial periods , 2003 .

[54]  S. Khatiwala,et al.  Accelerated simulation of passive tracers in ocean circulation models , 2003 .

[55]  J. Toggweiler,et al.  Representation of the carbon cycle in box models and GCMs: 1. Solubility pump , 2003 .

[56]  J. Toggweiler,et al.  Representation of the carbon cycle in box models and GCMs, 2, Organic pump , 2003 .

[57]  Marika M. Holland,et al.  The UVic earth system climate model: Model description, climatology, and applications to past, present and future climates , 2001, Data, Models and Analysis.

[58]  E. Boyle,et al.  Glacial/interglacial variations in atmospheric carbon dioxide , 2000, Nature.

[59]  B. Stephens,et al.  The influence of Antarctic sea ice on glacial–interglacial CO 2 variations , 2000, Nature.

[60]  Thierry Fichefet,et al.  Problems with using radiocarbon to infer ocean ventilation rates for past and present climates , 1999 .

[61]  D. Sigman,et al.  Contribution of Southern Ocean surface-water stratification to low atmospheric CO2 concentrations during the last glacial period , 1997, Nature.

[62]  John H. Martin.  glacial-interglacial Co2 change : the iron hypothesis , 1990 .

[63]  E. Galbraith,et al.  Response of a comprehensive climate model to a broad range of external forcings: relevance for deep ocean ventilation and the development of late Cenozoic ice ages , 2018, Climate Dynamics.

[64]  Stephen C. Riser,et al.  SOCCOM float data - Snapshot 2018-03-06. In Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) Float Data Archive , 2018 .

[65]  Lisa Dresner,et al.  Ocean Dynamics And The Carbon Cycle Principles And Mechanisms , 2016 .

[66]  Margo Project Members.  Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum , 2009 .

[67]  Samar Khatiwala,et al.  Fast spin up of Ocean biogeochemical models using matrix-free Newton–Krylov , 2008 .

[68]  Wallace S. Broecker,et al.  The Carbon cycle and atmospheric CO[2] : natural variations Archean to present , 1985 .