Poorly ventilated deep ocean at the Last Glacial Maximum inferred from carbon isotopes: A data-model comparison study

Atmospheric CO₂ was ~90 ppmv lower at the Last Glacial Maximum (LGM) compared to the late Holocene, but the mechanisms responsible for this change remain elusive. Here we employ a carbon isotope-enabled Earth System Model to investigate the role of ocean circulation in setting the LGM oceanic δ¹³C distribution, thereby improving our understanding of glacial/interglacial atmospheric CO₂ variations. We find that the mean ocean δ¹³C change can be explained by a 378 ± 88 Gt C(2σ) smaller LGM terrestrial carbon reservoir compared to the Holocene. Critically, in this model, differences in the oceanic δ¹³C spatial pattern can only be reconciled with a LGM ocean circulation state characterized by a weak (10–15 Sv) and relatively shallow (2000–2500 m) North Atlantic Deep Water cell, reduced Antarctic Bottom Water transport (≤10 Sv globally integrated), and relatively weak (6–8 Sv) and shallow (1000–1500 m) North Pacific Intermediate Water formation. This oceanic circulation state is corroborated by results from the isotope-enabled Bern3D ocean model and further confirmed by high LGM ventilation ages in the deep ocean, particularly in the deep South Atlantic and South Pacific. This suggests a poorly ventilated glacial deep ocean which would have facilitated the sequestration of carbon lost from the terrestrial biosphere and atmosphere.

[1]  A. Timmermann,et al.  Strong middepth warming and weak radiocarbon imprints in the equatorial Atlantic during Heinrich 1 and Younger Dryas , 2016 .

[2]  C. Waelbroeck,et al.  Radiocarbon evidence for enhanced respired carbon storage in the Atlantic at the Last Glacial Maximum , 2016, Nature Communications.

[3]  S. Mulitza,et al.  North Atlantic Deep Water Production during the Last Glacial Maximum , 2016, Nature Communications.

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

[5]  J. Southon,et al.  Radiocarbon constraints on the extent and evolution of the South Pacific glacial carbon pool , 2016, Nature Communications.

[6]  F. Joos,et al.  Impact of oceanic circulation changes on atmospheric δ13CO2 , 2015 .

[7]  A. Timmermann,et al.  An Atlantic–Pacific ventilation seesaw across the last deglaciation , 2015 .

[8]  A. Schmittner,et al.  Southwest Atlantic water mass evolution during the last deglaciation , 2015 .

[9]  L. Keigwin,et al.  Radiocarbon profiles of the NW Pacific from the LGM and deglaciation: Evaluating ventilation metrics and the effect of uncertain surface reservoir ages , 2015 .

[10]  Gerrit Lohmann,et al.  Higher Laurentide and Greenland ice sheets strengthen the North Atlantic ocean circulation , 2015, Climate Dynamics.

[11]  I. N. McCave,et al.  Reduced ventilation and enhanced magnitude of the deep Pacific carbon pool during the last glacial period , 2015 .

[12]  J. Fohlmeister,et al.  Strong and deep Atlantic meridional overturning circulation during the last glacial cycle , 2014, Nature.

[13]  A. Timmermann,et al.  Ocean circulation reconstructions from εNd: A model‐based feasibility study , 2014 .

[14]  A. Mackensen,et al.  Modelling δ13C in benthic foraminifera: Insights from model sensitivity experiments , 2014 .

[15]  M. England,et al.  Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning , 2014, Nature Communications.

[16]  A. Mix,et al.  Late Glacial to Holocene radiocarbon constraints on North Pacific Intermediate Water ventilation and deglacial atmospheric CO2 sources , 2014 .

[17]  M. Sarnthein,et al.  Deep water formation in the North Pacific and deglacial CO2 rise , 2014 .

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

[19]  C. Waelbroeck,et al.  Radiocarbon evidence for alternating northern and southern sources of ventilation of the deep Atlantic carbon pool during the last deglaciation , 2014, Proceedings of the National Academy of Sciences.

[20]  F. Anslow,et al.  Assessing the impact of Laurentide Ice Sheet topography on glacial climate , 2014 .

[21]  G. Gebbie.  How much did Glacial North Atlantic Water shoal , 2014 .

[22]  M. England,et al.  Atlantic‐Pacific seesaw and its role in outgassing CO2 during Heinrich events , 2014 .

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

[24]  E. Michel,et al.  Carbon isotope records reveal precise timing of enhanced Southern Ocean upwelling during the last deglaciation , 2013, Nature Communications.

[25]  S. Eggins,et al.  Responses of the Deep Ocean Carbonate System to Carbon Reorganization During the Last Glacial-Interglacial Cycle , 2013 .

[26]  Dawei Li.  Meridional Overturning Circulation of a Snowball Ocean , 2013 .

[27]  A. Mouchet.  The Ocean Bomb Radiocarbon Inventory Revisited , 2013, Radiocarbon.

[28]  Fortunat Joos,et al.  A reconstruction of radiocarbon production and total solar irradiance from the Holocene 14 C and CO 2 records: implications of data and model uncertainties , 2013 .

[29]  F. Joos,et al.  Simulating atmospheric CO2, 13C and the marine carbon cycle during the Last Glacial–Interglacial cycle: possible role for a deepening of the mean remineralization depth and an increase in the oceanic nutrient inventory , 2012 .

[30]  H. Schulz,et al.  Strength and geometry of the glacial Atlantic Meridional Overturning Circulation , 2012 .

[31]  I. Usoskin,et al.  A new model of cosmogenic production of radiocarbon 14C in the atmosphere , 2012, 1206.6974.

[32]  Thomas F. Stocker,et al.  Carbon Isotope Constraints on the Deglacial CO2 Rise from Ice Cores , 2012, Science.

[33]  A. Burke,et al.  The Southern Ocean’s Role in Carbon Exchange During the Last Deglaciation , 2012, Science.

[34]  P. Ciais,et al.  Large inert carbon pool in the terrestrial biosphere during the Last Glacial Maximum , 2012 .

[35]  G. Lohmann,et al.  A model-data comparison of δ13C in the glacial Atlantic Ocean , 2011 .

[36]  A. Timmermann,et al.  Deconstructing the Last Glacial termination: the role of millennial and orbital-scale forcings , 2011 .

[37]  W. Broecker,et al.  The Deglacial Evolution of North Atlantic Deep Convection , 2011, Science.

[38]  V. Brovkin,et al.  Last Glacial Maximum CO2 and δ13C successfully reconciled , 2011 .

[39]  A. Mouchet.  A 3D model of ocean biogeochemical cycles and climate sensitivity studies , 2011 .

[40]  V. Brovkin,et al.  Last Glacial Maximum CO 2 and 13 C δ successfully reconciled , 2011 .

[41]  Benoît Tartinville,et al.  Description of the Earth system model of intermediate complexity LOVECLIM version 1.2 , 2010 .

[42]  F. Joos,et al.  Deep ocean ventilation, carbon isotopes, marine sedimentation and the deglacial CO 2 rise , 2010 .

[43]  T. Guilderson,et al.  Upper-ocean-to-atmosphere radiocarbon offsets imply fast deglacial carbon dioxide release , 2010, Nature.

[44]  M. Vautravers,et al.  Extreme deepening of the Atlantic overturning circulation during deglaciation , 2010 .

[45]  A. Abe-Ouchi,et al.  Deepwater Formation in the North Pacific During the Last Glacial Termination , 2010, Science.

[46]  E. Michel,et al.  Ventilation of the Deep Southern Ocean and Deglacial CO2 Rise , 2010, Science.

[47]  L. Keigwin,et al.  No signature of abyssal carbon in intermediate waters off Chile during deglaciation , 2010 .

[48]  K. Suzuki,et al.  Ventilation of the Deep Southern Ocean and Deglacial CO 2 Rise , 2010 .

[49]  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 .

[50]  Jerry F. McManus,et al.  Glacial‐interglacial circulation changes inferred from 231Pa/230Th sedimentary record in the North Atlantic region , 2009 .

[51]  G. Foster,et al.  Variable Quaternary chemical weathering fluxes and imbalances in marine geochemical budgets , 2009, Nature.

[52]  David Pollard,et al.  Modelling West Antarctic ice sheet growth and collapse through the past five million years , 2009, Nature.

[53]  G. Haug,et al.  Subarctic Pacific evidence for a glacial deepening of the oceanic respired carbon pool , 2009 .

[54]  A. Timmermann,et al.  Climate and marine carbon cycle response to changes in the strength of the southern hemispheric westerlies , 2008 .

[55]  H. Elderfield,et al.  Seawater carbonate ion-δ13C systematics and application to glacial–interglacial North Atlantic ocean circulation , 2008 .

[56]  T. Stocker,et al.  Modeling the effect of abrupt ocean circulation change on marine reservoir age , 2008 .

[57]  G. Haug,et al.  Carbon dioxide release from the North Pacific abyss during the last deglaciation , 2007, Nature.

[58]  A. Abe‐Ouchi,et al.  Climatic Conditions for modelling the Northern Hemisphere ice sheets throughout the ice age cycle , 2007 .

[59]  B. Otto‐Bliesner,et al.  Last Glacial Maximum ocean thermohaline circulation: PMIP2 model intercomparisons and data constraints , 2007 .

[60]  W. Broecker,et al.  Deep water mass geometry in the glacial Atlantic Ocean: A review of constraints from the paleonutrient proxy Cd/Ca , 2006 .

[61]  W. Peltier,et al.  The modern and glacial overturning circulation in the Atlantic ocean in PMIP coupled model simulations , 2006 .

[62]  J. Toggweiler,et al.  Midlatitude westerlies, atmospheric CO2, and climate change during the ice ages , 2006 .

[63]  BCI 12 C Fractionation during CO 2 Transfer from Air to Sea , 2006 .

[64]  J. Lynch‐Stieglitz,et al.  Meridional overturning circulation in the South Atlantic at the last glacial maximum , 2005 .

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

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

[67]  William B. Curry,et al.  Glacial water mass geometry and the distribution of δ13C of ΣCO2 in the western Atlantic Ocean , 2004 .

[68]  L. Keigwin.  Radiocarbon and stable isotope constraints on Last Glacial Maximum and Younger Dryas ventilation in the western North Atlantic , 2004 .

[69]  H. Fischer,et al.  Simulating changes in the terrestrial biosphere during the last glacial/interglacial transition , 2004 .

[70]  Paul J. Valdes,et al.  Transient simulations of Holocene atmospheric carbon dioxide and terrestrial carbon since the Last Glacial Maximum , 2004 .

[71]  C. Wunsch.  Determining paleoceanographic circulations, with emphasis on the Last Glacial Maximum , 2003 .

[72]  J. Lynch‐Stieglitz,et al.  Interior hydrography and circulation of the glacial Pacific Ocean , 2002 .

[73]  L. Keigwin,et al.  Ocean ventilation and sedimentation since the glacial maximum at 3 km in the western North Atlantic , 2002 .

[74]  G. Munhoven.  Glacial–interglacial changes of continental weathering: estimates of the related CO2 and HCO3− flux variations and their uncertainties , 2002 .

[75]  R. Zeebe.  Glacial/interglacial variations in atmospheric CO2 , 2002 .

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

[77]  T. Guilderson,et al.  Old radiocarbon ages in the southwest Pacific Ocean during the last glacial period and deglaciation , 2000, Nature.

[78]  D. Lea,et al.  Temperature influence on the carbon isotopic composition of Globigerina bulloides and Orbulina universa (planktonic foraminifera) , 2000 .

[79]  William B. Curry,et al.  Weaker Gulf Stream in the Florida Straits during the Last Glacial Maximum , 1999, Nature.

[80]  J. Toggweiler.  Variation of atmospheric CO2 by ventilation of the ocean's deepest water , 1999 .

[81]  G. Ramstein,et al.  Carbon stocks and isotopic budgets of the terrestrial biosphere at mid-Holocene and last glacial maximum times , 1999 .

[82]  Jelle Bijma,et al.  Effect of seawater carbonate concentration on foraminiferal carbon and oxygen isotopes , 1997, Nature.

[83]  V. Brovkin,et al.  A continuous climate-vegetation classification for use in climate-biosphere studies , 1997 .

[84]  L. François,et al.  Sensitivity of a global oceanic carbon cycle model to the circulation and to the fate of organic matter: preliminary results , 1996 .

[85]  G. Farquhar,et al.  Terrestrial carbon storage at the LGM , 1994, Nature.

[86]  Laurent Labeyrie,et al.  Changes in east Atlantic deepwater circulation over the last 30 , 1994 .

[87]  A. Mackensen,et al.  The δ13C in benthic foraminiferal tests of Fontbotia wuellerstorfi (Schwager) Relative to the δ13C of dissolved inorganic carbon in Southern Ocean Deep Water: Implications for glacial ocean circulation models , 1993 .

[88]  J. Hayes,et al.  Fractionation of carbon isotopes by phytoplankton and estimates of ancient CO2 levels. , 1992, Global biogeochemical cycles.

[89]  I. Lerche,et al.  Opening the carbon isotope "vital effect" black box, 2, Quantitative model for interpreting foramini , 1991 .

[90]  Laurent Labeyrie,et al.  Deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation , 1988 .

[91]  N. Shackleton.  Carbon-13 in Uvigerina: Tropical Rainforest History and the Equatorial Pacific Carbonate Dissolution Cycles , 1977 .

[92]  W. G. Mook,et al.  CARBON ISOTOPE FRACTIONATION BETWEEN DISSOLVED BICARBONATE AND GASEOUS CARBON-DIOXIDE , 1974 .

[93]  I. Friedmann.  Cell Membrane Fusion and the Fertilization Mechanism in Plants and Animals , 1962, Science.