References

Climate of the Past

1814-9332

Copernicus GmbH

Göttingen, Germany

10.5194/cp-2-57-2006

Simulating low frequency changes in atmospheric CO2 during the last 740 000 years

Köhler

¹ Fischer

Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, P.O. Box 12 01 61, 27515 Bremerhaven, Germany

11 09 2006

2 2 57 78

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Atmospheric CO2 measured in Antarctic ice cores shows a natural variability of 80 to 100 ppmv during the last four glacial cycles and variations of approximately 60 ppmv in the two cycles between 410 and 650 kyr BP. We here use various paleo-climatic records from the EPICA Dome C Antarctic ice core and from oceanic sediment cores covering the last 740 kyr to force the ocean/atmosphere/biosphere box model of the global carbon cycle BICYCLE in a forward mode over this time in order to interpret the natural variability of CO2. Our approach is based on the previous interpretation of carbon cycle variations during Termination I (Köhler et al., 2005a). In the absense of a process-based sediment module one main simplification of BICYCLE is that carbonate compensation is approximated by the temporally delayed restoration of deep ocean [CO32−]. Our results match the low frequency changes in CO2 measured in the Vostok and the EPICA Dome C ice core for the last 650 kyr BP (r2≈0.75). During these transient simulations the carbon cycle reaches never a steady state due to the ongoing variability of the overall carbon budget caused by the time delayed response of the carbonate compensation to other processes. The average contributions of different processes to the rise in CO2 during Terminations I to V and during earlier terminations are: the rise in Southern Ocean vertical mixing: 36/22 ppmv, the rise in ocean temperature: 26/11 ppmv, iron limitation of the marine biota in the Southern Ocean: 20/14 ppmv, carbonate compensation: 15/7 ppmv, the rise in North Atlantic deep water formation: 13/0 ppmv, the rise in gas exchange due to a decreasing sea ice cover: −8/−7 ppmv, sea level rise: −12/−4 ppmv, and rising terrestrial carbon storage: −13/−6 ppmv. According to our model the smaller interglacial CO2 values in the pre-Vostok period prior to Termination V are mainly caused by smaller interglacial Southern Ocean SST and an Atlantic THC which stayed before MIS 11 (before 420 kyr BP) in its weaker glacial circulation mode.

References 1

Abelmann, A., Gersonde, R., Cortese, G., Kuhn, G., and Smetacek, V.: Extensive phytoplankton blooms in the Atlantic sector of the glacial Southern Ocean, Paleoceanography, 21, PA1013; doi:10.1029/2005PA001199, 2006.

Adkins, J F., McIntyre, K., and Schrag, D P.: The salinity, temperature, and $\delta^18$O of the glacial deep ocean, Science, 298, 1769–1773, 2002.

Archer, D. and Maier-Reimer, E.: Effect of deep-sea sedimentary calcite preservation on atmospheric CO2 concentration, Nature, 367, 260–263, 1994.

Archer, D., Kheshgi, H., and Maier-Reimer, E.: Multiple timescales for neutralization of fossil fuel CO2, Geophys. Res. Lett., 24, 405–408, 1997.

Archer, D., Kheshgi, H., and Maier-Reimer, E.: Dynamics of fossil fuel neutralization by marine CaCO3, Global Biogeochem. Cycles, 12, 259–276, 1998.

Archer, D., Winguth, A., Lea, D., and Mahowald, N.: What caused the glacial/interglacial atmospheric $p$CO2 cycles?, Rev. Geophys., 38, 159–189, 2000.

Archer, D E.: Equatorial Pacific calcite preservation cycles: production or dissolution?, Paleoceanography, 6, 561–571, 1991.

Archer, D E.: An atlas of the distribution of calcium carbonate in sediments of the deep sea, Global Biogeochem. Cycles, 10, 159–174, 1996.

Archer, D E., Martin, P A., Milovich, J., Brovkin, V., Plattner, G.-K., and Ashendel, C.: Model sensitivity in the effect of Antarctic sea ice and stratification on atmospheric $p$CO2, Paleoceanography, 18, 1012, doi:10.1029/2002PA000760, 2003.

Barnola, J M., Raynaud, D., Korotkevich, Y S., and Lorius, C.: Vostok ice core provides 160 000-year record of atmospheric CO2, Nature, 329, 408–414, 1987.

Bender, M.: Climate-biosphere interactions on glacial-interglacial timescales, Global Biogeochem. Cycles, 17, 1082, doi:10.1029/GB001932, 2003.

Bintanja, R., van~der Wal, R., and Oerlemans, J.: Modelled atmospheric temperatures and global sea levels over the past million years, Nature, 437, 125–128; doi:10.1038/nature03975, 2005.

Broecker, W., Barker, S., Clark, E., Hajdas, I., Bonani, G., and Stott, L.: Ventilation of the glacial deep Pacific Ocean, Science, 306, 1169–1172, 2004.

Broecker, W S. and Peng, T.-H.: The role of CaCO3 compensation in the glacial to interglacial atmospheric CO2 change, Global Biogeochem. Cycles, 1, 15–29, 1987.

Brook, E J.: Tiny bubbles tell all, Science, 310, 1285–1287, doi:10.1126/science.11211535, 2005.

Brzezinski, M A., Pride, C J., Franck, V M., Sigman, D M., Matsumoto, J. L. S K., Gruber, N., Rau, G H., and Coale, K H.: A switch from Si(OH)4 to NO$_3^-$ depletion in the glacial Southern Ocean, Geophys. Res. Lett., 29, 1564, doi:10.1029/2001GL014 349, 2002.

Cavalieri, D J., Gloersen, P., .Parkinson, C L., Comiso, J C., and Zwally, H J.: Observed hemispheric asymmetry in global sea ice changes, Science, 278, 1104–1106, 1997.

Crosta, X., Pichon, J.-J., and Burckle, L H.: Application of modern analog technique to marine Antarctic diatoms: Reconstruction of maximum sea-ice extent at the Last Glacial Maximum, Paleoceanography, 13, 284–297, 1998a.

Crosta, X., Pichon, J.-J., and Burckle, L H.: Reappraisal of Antarctic seasonal sea-ice extent at the Last Glacial Maximum, Geophys. Res. Lett., 14, 2703–2706, 1998b.

Davidson, E A. and Janssens, I A.: Temperature sensitivity of soil carbon decomposition and feedbacks to climate change, Nature, 440, 165–173, doi:10.1038/nature04514, 2006.

de~Baar, H. J W., Boyd, P W., Coale, K H., Landry, M R., Tsuda, A., Assmy, P., Bakker, D. C E., Bozec, Y., Barber, R T., Brzezinski, M A., Buesseler, K O., Boyé, M., Croot, P L., Gervais, F., Gorbunov, M Y., Harrison, P J., Hiscock, W T., Laan, P., Lancelot, C., Law, C S., Levasseur, M., Marchetti, A., Millero, F J., Nishioka, J., Nojiri, Y., van Oijen, T., Riebesell, U., Rijkenberg, M. J A., Saito, H., Takeda, S., Timmermans, K R., Veldhuis, M. J W., Waite, A M., and Wong, C.-S.: Synthesis of iron fertilization experiments: From the Iron Age in the Age of Enlightenment, J. Geophys. Res., 110, C09S16, doi:10.1029/2004JC002 601, 2005.

EPICA-community-members: Eight glacial cycles from an Antarctic ice core, Nature, 429, 623–628, 2004.

Farrell, J W. and Prell, W L.: Climate change and CaCO3 preservation: An 800,000 year bathymetric reconstruction from the central equatorial Pacific Ocean, Paleoceanography, 4, 447–466, 1989.

Fischer, H., Wahlen, M., Smith, J., Mastroianni, D., and Deck, B.: Ice core records of atmospheric CO2 around the last three glacial terminations, Science, 283, 1712–1714, 1999.

Flower, B P., Oppo, D W., McManus, J F., Venz, K A., Hodell, D A., and Cullen, J L.: North Atlantic intermediate to deep water circulation and chemical stratification during the past 1 Myr, Paleoceanography, 15, 388–403, 2000.

François, R., Altabet, M A., Yu, E.-F., Sigman, D M., Pacon, M P., Frankl, M., Bohrmann, G., Bareille, G., and Labeyrie, L D.: Contribution of Southern Ocean surface-water stratification to low atmopsheric CO2 concentrations during the last glacial period, Nature, 389, 929–935, 1997.

Friedlingstein, P., Dufresne, J.-L., Cox, P M., and Rayner, P.: How positive is the feedback between climate change and the carbon cycle?, Tellus, 55B, 692–700, 2003.

Ganachaud, A. and Wunsch, C.: Improved estimates of global ocean circulation, heat transport and mixing from hydrographic data, Nature, 408, 453–457, 2000.

Gaspari, V., Barbante, C., Cozzi, G., Cescon, P., Boutron, C F., Gabrielli, P., Capodaglio, G., Ferrari, C., Petit, J R., and Delmonte, B.: Atmospheric iron fluxes over the last deglaciation: Climatic implications, Geophys. Res. Lett., 33, L03704; doi:10.1029/2005GL024352, 2006.

Gersonde, R., Crosta, X., Abelmann, A., and Armand, L.: Sea-surface temperature and sea ice distribution of the Southern Ocean at the EPILOG Last Glacial Maximum – a circum-Antarctic view based on siliceous microfossil records, Quat. Sci. Rev., 24, 869–896, 2005.

Gildor, H., Tziperman, E., and Toggweiler, J R.: Sea ice switch mechanism and glacial-interglacial CO2 variations, Global Biogeochem. Cycles, 16, 1032, doi:10.1029/2001GB001446, 2002.

Gnanadesikan, A., Slater, R D., Gruber, N., and Sarmiento, J L.: Oceanic vertical exchange and new production: a comparison between models and observations, Deep-Sea Res. II, 49, 363–401, 2002.

Gosink, T A., Pearson, J G., and Kelley, J J.: Gas movement through sea ice, Nature, 263, 41–42, 1976.

Heinrich, H.: Origin and consequences of cyclic ice rafting in the northeast Atlantic ocean during the past 130,000 years, Quat. Res., 29, 142–152, 1988.

Hodell, D A., Venz, K A., Charles, C D., and Ninnemann, U S.: Pleistocene vertical carbon isotope and carbonate gradients in the South Atlantic sector of the Southern Ocean, Geochemistry, Geophysics, Geosystems, 4, 1004, doi:10.1029/2002GC000367, 2003.

Hönisch, B. and Hemming, N G.: Surface ocean pH response to variations in pCO2 through two full glacial cycles, Earth Planet. Sci. Lett., 236, 305–314, 2005.

Jaccard, S L., Haug, G H., Sigman, D M., Pedersen, T F., Thierstein, H R., and Röhl, U.: Glacial/interglacial changes in subarctic North Pacific stratification, Science, 308, 1003–1006, 2005.

Jin, X., Gruber, N., Dunne, J P., Sarmiento, J L., and Armstrong, R A.: Diagnosing the contribution of phytoplankton functional groups to the production and export of particulate organic carbon, CaCO3, and opal from global nutrient and alkalinity distributions, Global Biogeochem. Cycles, 20, GB2015; doi:10.1029/2005GB002532, 2006.

Jones, I W., Munhoven, G., Tranter, M., Huybrechts, P., and Sharp, M J.: Modelled glacial and non-glacial HCO$_3^-$, Si and Ge fluxes since the LGM: little potential for impact on atmospheric CO2 concentrations and a potential proxy of continental chemical erosion, the marine Ge/Si ratio, Global and Planetary Change, 33, 139–153, 2002.

Joos, F., Gerber, S., Prentice, I C., Otto-Bliesner, B L., and Valdes, P J.: Transient simulations of Holocenic atmospheric carbon dioxide and terrestrial carbon since the Last Glacial Maximum, Global Biogeochem. Cycles, 18, GB2002, doi:10.1029/2003GB002156, 2004.

Jouzel, J., Lorius, C., Petit, J R., Genthon, C., Barkov, N I., Kotlyakov, V M., and Petrov, V M.: Vostok ice core: a continuous isotope temperature record over the last climate cycle (160 000 years), Nature, 329, 403–408, 1987.

Jouzel, J., Vimeux, F., Caillon, N., Delaygue, G., Hoffmann, G., Masson-Delmotte, V., and Parrenin, F.: Magnitude of isotopics/temperature scaling for interpretation of central Antarctic ice cores, J. Geophys. Res., 108, 4361, doi:10.1029/2002JD002677, 2003.

Kawamura, K., Nakazawa, T., Aoki, S., Sugawara, S., Fujii, Y., and Watanabe, O.: Atmopsheric CO2 variations over the last three glacial-interglacial climatic cycles deduced from the Dome Fuji deep ice core, Antarctica using a wet extraction technique, Tellus, 55B, 126–137, 2003.

Klaas, C. and Archer, D E.: Association of sinking organic matter with various types of mineral ballast in the deep sea: Implications for the rain ratio, Global Biogeochem. Cycles, 16, 1116, doi:10.1029/2001GB001765, 2002.

Knorr, G. and Lohmann, G.: Southern Ocean origin for the resumption of Atlantic thermohaline circulation during deglaciation, Nature, 424, 532–536, 2003.

Köhler, P. and Fischer, H.: Simulating changes in the terrestrial biosphere during the last glacial/interglacial transition, Global and Planetary Change, 43, 33–55, doi:10.1016/j.gloplacha.2004.02.005, 2004.

Köhler, P., Fischer, H., Munhoven, G., and Zeebe, R E.: Quantitative interpretation of atmospheric carbon records over the last glacial termination, Global Biogeochem. Cycles, 19, GB4020, doi:10.1029/2004GB002 345, 2005a.

Köhler, P., Joos, F., Gerber, S., and Knutti, R.: Simulated changes in vegetation distribution, land carbon storage, and atmospheric CO2 in response to a collapse of the North Atlantic thermohaline circulation, Clim. Dyn., 25, 689–708, doi:10.1007/s00 382–005–0058–8, 2005b.

Köhler, P., Muscheler, R., and Fischer, H.: A model-based interpretation of low frequency changes in the carbon cycle during the last 120 kyr and its implications for the reconstruction of atmospheric $\Delta^14$C, Geochemistry, Geophysics, Geosystems, in press, doi:10.1029/2005GC001228, 2006.

Kutzbach, J., Gallimore, R., Harrison, S., Behling, P., Selin, R., and Laarif, F.: Climate and biome simulations for the past 21 000 years, Quat. Sci. Rev., 17, 473–506, 1998.

Labeyrie, L D., Duplessy, J C., and Blanc, P L.: Variations in mode of formation and temperature of oceanic deep waters over the past 125 000 years, Nature, 327, 477–482, 1987.

Legrand, M.: Chemistry of Antarctic snow and ice, J. Phys., 48/C1, 77–86, 1987.

Lisiecki, L E. and Raymo, M E.: A Pliocene-Pleistocene stack of 57 globally distributed benthic $\delta^18$O records, Paleoceanography, 20, PA1003, doi:10.1029/2004PA001071, 2005.

Marchitto, T M., Lynch-Stieglitz, J., and Hemming, S R.: Deep Pacific CaCO3 compensation and glacial-interglacial atmospheric CO2, Earth Planet. Sci. Lett., 231, 317–336, 2005.

Martin, J H.: Glacial-interglacial CO2 change: the iron hypothesis, Paleoceanography, 5, 1–13, 1990.

Matsumoto, K., Sarmiento, J L., and Brzezinski, M A.: Silicic acid leakage from the Southern Ocean: a possible explanation for glacial atmospheric $p$CO2, Global Biogeochem. Cycles, 16, 1031, doi:10.1029/2001GB001442, 2002.

McManus, J F., Oppo, D W., and Cullen, J L.: A 0.5-million-year record of millennial-scale climate variability in the North Atlantic, Science, 283, 971–975, 1999.

McManus, J F., Francois, R., Gheradi, J.-M., Keigwin, L D., and Brown-Leger, S.: Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes, Nature, 428, 834–837, 2004.

McNeil, B. I., Metzl, N., Key, R. M., and Matear, R. J.: An Empirical Estimate of the Southern Ocean air-sea CO2 flux, Eos Trans. AGU, 87(36), Ocean Science Meeting Supplements, Abstract OS24G-02, 2006.

Meissner, K J., Schmittner, A., Weaver, A J., and Adkins, J F.: Ventilation of the North Atlantic Ocean during the Last Glacial Maximum: a comparison between simulated and observed radiocarbon ages, Paleoceanography, 18, 1023, doi:10.1029/2002PA000762, 2003.

Monnin, E., Indermühle, A., Dällenbach, A., Flückiger, J., Stauffer, B., Stocker, T F., Raynaud, D., and Barnola, J.-M.: Atmospheric CO2 concentrations over the last glacial termination, Science, 291, 112–114, 2001.

Morales-Maqueda, M A. and Rahmstorf, S.: Did Antarctic sea-ice expansion cause glacial CO2 decline?, Geophys. Res. Lett., 29, 1011, doi:10.1029/2001GL013240, 2001.

Munhoven, G.: Glacial-interglacial changes of continental weathering: estimates of the related CO2 and HCO$_3^-$ flux variations and their uncertainties, Global and Planetary Change, 33, 155–176, 2002.

Paillard, D. and Parrenin, F.: The Antarctic ice sheet and the triggering of deglaciations, Earth Planet. Sci. Lett., 227, 263–271, 2004.

Petit, J R., Jouzel, J., Raynaud, D., Barkov, N I., Barnola, J.-M., Basile, I., Bender, M., Chappellaz, J., Davis, M., Delaygue, G., Delmotte, M., Kotlyakov, V M., Legrand, M., Lipenkov, V Y., Lorius, C., Pépin, L., Ritz, C., Saltzman, E., and Stievenard, M.: Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica, Nature, 399, 429–436, 1999.

Reimer, P J., Baillie, M. G L., Bard, E., Bayliss, A., Beck, J W., Bertrand, C. J H., Blackwell, P G., Buck, C E., Burr, G S., Cutler, K B., Damon, P E., Edwards, R L., Fairbanks, R G., Friedrich, M., Guilderson, T P., Hogg, A G., Hughen, K A., Kromer, B., McCormac, G., Manning, S., Ramsey, C B., Reimer, R W., Remmele, S., Southon, J R., Stuiver, M., Talamo, S., Taylor, F W., van~der Plicht, J., and Weyhenmeyer, C E.: INTCAL04 terrestrial radiocarbon age calibration, 0–26 Cal kyr BP, Radiocarbon, 46, 1029–1058, 2004.

Ridgwell, A J.: An end to the rain ratio reign?, Geochemistry, Geophysics, Geosystems, 4, 1051, doi:10.1029/2003GC000512, 2003a.

Ridgwell, A J.: Implications of the glacial CO2 iron hypothesis for Quaternary climate change, Geochemistry, Geophysics, Geosystems, 4, 1076, doi:10.1029/2003GC000563, 2003b.

Ridgwell, A J. and Watson, A J.: Feedback between aeolian dust, climate, and atmospheric CO2 in glacial time, Paleoceanography, 17, 1059, 10.1029/2001PA000729, 2002.

Riebesell, U., Zondervan, I., Rost, B., Tortell, P D., Zeebe, R E., and Morel, F. M M.: Reduced calcification of marine plankton in response to increased atmospheric CO2, Nature, 407, 364–367, 2000.

Röthlisberger, R., Mulvaney, R., Wolff, E W., Hutterli, M A., Bigler, M., Sommer, S., and Jouzel, J.: Dust and sea salt variability in central East Antarctica (Dome C) over the last 45 kyrs and its implications for southern high-latitude climate, Geophys. Res. Lett., 29, 1963, doi:10.1029/GL015186, 2002.

Röthlisberger, R., Bigler, M., Wolff, E W., Monnin, E., Joos, F., and Hutterli, M.: Ice core evidence for the extent of past atmospheric CO2 change due to iron fertilization, Geophys. Res. Lett., 31, L16207, doi:10.1029/2004GL020338, 2004.

Sachs, J P. and Anderson, R F.: Increased productivity in the subantarctic ocean during Heinrich events, Nature, 434, 1118–1121, 2005.

Sarnthein, M., Pflaumann, U., and Weinelt, M.: Past extent of sea ice in the northern North Atlantic inferred from foraminiferal paleotemperature estimates, Paleoceanography, 18, 1047, doi:10.1029/2002PA000771, 2003.

Schmittner, A.: Decline of the marine ecosystem caused by a reduction in the Atlantic overturning circulation, Nature, 434, 628–633, 2005.

Schwander, J., Jouzel, J., Hammer, C U., Petit, J.-R., Udisti, R., and Wolff, E.: A tentative chronology for the EPICA Dome Concordia ice core, Geophys. Res. Lett., 28, 4243–4246, 2001.

Semiletov, I., Makshtas, A., and Akasofu, S.-I.: Atmospheric CO2 balance: the role of Arctic sea ice, Geophys. Res. Lett., 31, L05121, doi:10.1029/2003GL017996, 2004.

Shackleton, N.: The 100,000-year ice-age cycle identified and found to lag temperature, carbon dioxide, and orbital eccentricity, Science, 289, 1897–1902, 2000.

Shackleton, N J., Berger, A., and Peltier, W P.: An alternative astronomical calibration of the lower Pleistocene timescale based on OPD site 677, Transactions of the Royal Society of Edinburgh: Earth Sciences, 81, 251–261, 1990.

Siddall, M., Rohling, E J., Almogi-Labin, A., Hemleben, C., Meischner, D., Schmelzer, I., and Smeed, D A.: Sea-level fluctuations during the last glacial cycle, Nature, 423, 853–858, 2003.

Siegenthaler, U., Stocker, T F., Monnin, E., Lüthi, D., Schwander, J., Stauffer, B., Raynaud, D., Barnola, J.-M., Fischer, H., Masson-Delmotte, V., and Jouzel, J.: Stable carbon cycle-climate relationship during the late Pleistocene, Science, 310, 1313–1317; doi:10.1126/science.1120 130, 2005.

Sigman, D M. and Boyle, E A.: Glacial/interglacial variations in atmospheric carbon dioxide, Nature, 407, 859–869, 2000.

Smith, H J., Fischer, H., Wahlen, M., Mastroianni, D., and Deck, B.: Dual modes of the carbon cycle since the Last Glacial Maximum, Nature, 400, 248–250, 1999.

Stephens, B B. and Keeling, R F.: The influence of Antarctic sea ice on glacial-interglacial CO2 variations, Nature, 404, 171–174, 2000.

Stocker, T F. and Johnsen, S J.: A minimum thermodynamic model for the bipolar seesaw, Paleoceanography, 18, 1087, doi:10.1029/2003PA000920, 2003.

Takahashi, T., Sutherland, S C., Sweeney, C., Poisson, A., Metzl, N., Tilbrook, B., Bates, N., Wanninkhof, R., andd C Sabine, R. A F., Olafsson, J., and Nojiri, Y.: Global sea-air CO2 flux based on climatological surface ocean $p$CO2, and seasonal biological and temperature effects, Deep-Sea Res. II, 49, 1601–1622, 2002.

Toggweiler, J R.: Variation of atmospheric CO2 by ventilation of the ocean's deepest water, Paleoceanography, 14, 571–588, 1999.

Toggweiler, J R., l Russell, J., and Carson, S R.: Midlatitude westerlies, atmospheric CO2, and climate change during the ice ages, Paleoceanography, 21, PA2005; doi:10.1029/2005PA001154, 2006.

Vecsei, A. and Berger, W H.: Increase of atmospheric CO2 during deglaciation: constraints on the coral reef hypothesis from patterns of deposition, Global Biogeochem. Cycles, 18, GB 1035, doi:10.1029/2003GB002147, 2004.

Vimeux, F., Cuffey, K M., and Jouzel, J.: New insights into Southern Hemisphere temperature changes from Vostok ice cores using deuterium excess correction, Earth Planet. Sci. Lett., 203, 829–843, 2002.

Visser, K., Thunell, R., and Stott, L.: Magnitude and timing of temperature change in the Indo-Pacific warm pool during deglaciation, Nature, 421, 152–155, 2003.

Watson, A J. and Naveira-Garabato, A C.: The role of Southern Ocean mixing and upwelling in glacial-interglacial atmospheric CO2 change, Tellus B, 58B, 73–87, 2006.

Wolff, E W., Chappellaz, J A., Fischer, H., Krull, C., Miller, H., Stocker, T., and Watson, A J.: The EPICA challenge to the Earth System Modeling Community, EOS, 85, 363, 2004.

Wolff, E W., Kull, C., Chappellaz, J., Fischer, H., Miller, H., Stocker, T F., Watson, A J., Flower, B., Joos, F., Köhler, P., Matsumoto, K., Monnin, E., Mudelsee, M., Paillard, D., and Shackleton, N.: Modeling past atmospheric CO2: results of a challenge, EOS, 86 (38), 341, 345, 2005.

Wolff, E W., Fischer, H., Fundel, F., Ruth, U., Twarloh, B., Littot, G C., Mulvaney, R., Röthlisberger, R., de~Angelis, M., Boutron, C F., Hansson, M., Jonsell, U., Hutterli, M., Lambert, F., Kaufmann, P., Stauffer, B., Stocker, T F., Steffensen, J P., Bigler, M., Siggaard-Andersen, M L., Udisti, R., Becagli, S., Castellano, E., Severi, M., Wagenbach, D., Barbante, C., Gabrielli, P., and Gaspari, V.: Southern Ocean sea-ice extent, productivity and iron fluxes over the past eight glacial cycles, Nature, 440, 491–496; doi:10.1038/nature04614, 2006.

Wright, A K. and Flower, B P.: Surface and deep ocean circulation in the subpolar North Atlantic during the mid-Pleistocene revolution, Paleoceanography, 17, 1068, doi:10.1029/2002PA000782, 2002.

Zeebe, R E. and Westbroek, P.: A simple model for the CaCO3 saturation state of the ocean: the Strangelove, the Neritan, and the Cretan Ocean, Geochemistry, Geophysics, Geosystems, 4, 1104, doi:10.1029/2003GC000538, 2003.

Zeebe, R E. and Wolf-Gladrow, D A.: CO2 in Seawater: Equilibrium, Kinetics, Isotopes, vol 65 of Elsevier Oceanography Book Series, Elsevier Science Publishing, Amsterdam, The Netherlands, 2001.