CP Climate of the Past CP Clim. Past 1814-9332 Copernicus Publications Göttingen, Germany 10.5194/cp-7-487-2011 The global ocean circulation on a retrograde rotating earth Kamphuis V. 1 Huisman S. E. 1 Dijkstra H. A. 1 Institute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, The Netherlands 09 05 2011 7 2 487 499 Copyright: © 2011 V. Kamphuis et al. 2011 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://cp.copernicus.org/articles/7/487/2011/cp-7-487-2011.html The full text article is available as a PDF file from https://cp.copernicus.org/articles/7/487/2011/cp-7-487-2011.pdf

To understand the three-dimensional ocean circulation patterns that have occurred in past continental geometries, it is crucial to study the role of the present-day continental geometry and surface (wind stress and buoyancy) forcing on the present-day global ocean circulation. This circulation, often referred to as the Conveyor state, is characterised by an Atlantic Meridional Overturning Circulation (MOC) with a deep water formation at northern latitudes and the absence of such a deep water formation in the North Pacific. This MOC asymmetry is often attributed to the difference in surface freshwater flux: the Atlantic as a whole is a basin with net evaporation, while the Pacific receives net precipitation. This issue is revisited in this paper by considering the global ocean circulation on a retrograde rotating earth, computing an equilibrium state of the coupled atmosphere-ocean-land surface-sea ice model CCSM3. The Atlantic-Pacific asymmetry in surface freshwater flux is indeed reversed, but the ocean circulation pattern is not an Inverse Conveyor state (with deep water formation in the North Pacific) as there is relatively weak but intermittently strong deep water formation in the North Atlantic. Using a fully-implicit, global ocean-only model the stability properties of the Atlantic MOC on a retrograde rotating earth are also investigated, showing a similar regime of multiple equilibria as in the present-day case. These results indicate that the present-day asymmetry in surface freshwater flux is not the most important factor setting the Atlantic-Pacific salinity difference and, thereby, the asymmetry in the global MOC.

 References Briegleb, B., Bitz, C., Hunke, E., Lipscomb, W., Holland, M., Schramm, J., and Moritz, R.: Scientific description of the sea ice component in the Community Climate System Model, Version&nbsp;3, Tech. note tn-463+str, National Center for Atmospheric Research, Boulder, CO, 70&nbsp;pp., 2004. Collins, W.&nbsp;D., Blackmon, M.&nbsp;L., Bonan, G.&nbsp;B., Hack, J.&nbsp;J., Henderson, T.&nbsp;B., Kiehl, J.&nbsp;T., Large, W.&nbsp;G., McKenna, D.&nbsp;S., Bitz, C.&nbsp;M., Bretherton, C.&nbsp;S., Carton, J.&nbsp;A., Chang, P., Doney, S.&nbsp;C., Santer, B.&nbsp;D., and Smith, R.&nbsp;D.: The Community Climate System Model Version&nbsp;3 (CCSM3), J. Climate, 19, 2122–2143, 2006a. Collins, W.&nbsp;D., Rasch, P.&nbsp;J., Boville, B.&nbsp;A., Hack, J.&nbsp;J., McCaa, J.&nbsp;R., Williamson, D.&nbsp;L., Briegleb, B.&nbsp;P., Bitz, C.&nbsp;M., Lin, S.-J., and Zhang, M.: The Formulation and Atmospheric Simulation of the Community Atmosphere Model Version&nbsp;3 (CAM3), J. Climate, 19, 2144–2161, 2006b. Czaja, A.: On the driving processes of the Atlantic meridional overturning circulation, J. Phys. Oceanogr., 39, 234–247, 2009. Dickinson, R.&nbsp;E., Oleson, K.&nbsp;W., Bonan, G., Thornton, P., Vertenstein, M., Hoffman, F., Yang, Z.-L., and Zeng, X.: The Community Land Model and Its Climate Statistics as a Component of the Community Climate System Model, J. Climate, 19, 2302–2324, 2006. Dijkstra, H.&nbsp;A. and Weijer, W.: Stability of the global ocean circulation: Basic bifurcation diagrams, J. Phys. Oceanogr., 35, 933–948, 2005. Dijkstra, H. A., Weijer, W., and Neelin, J. D.: Imperfections of the three-dimensional thermohaline ocean circulation: Hysteresis and unique state regimes, J. Phys. Oceanogr., 33, 2796–2814, 2003. Emile-Geay, J., Cane, M.&nbsp;A., Naik, N., Seager, R., Clement, A.&nbsp;C., and van Geen, A.: Warren revisited: Atmospheric freshwater fluxes and "Why is no deep water formed in the North Pacific", J. Geophys. Res., 108, 3178, <a href="http://dx.doi.org/10.1029/2001JC001058">https://doi.org/10.1029/2001JC001058</a>, 2003. Ganachaud, A. and Wunsch, C.: Improved estimates of global ocean circulation, heat transport and mixing from hydrographic data, Nature, 408, 453–457, 2000. Gordon, A.&nbsp;L.: Interocean Exchange of Thermocline Water, J. Geophys. Res., 91, 5037–5046, <a href="http://dx.doi.org/10.1029/JC091iC04p05037">https://doi.org/10.1029/JC091iC04p05037</a>, 1986. Hughes, T. M.&nbsp;C. and Weaver, A.&nbsp;J.: Multiple Equilibria of an Asymmetric Two-Basin Ocean Model, J. Phys. Oceanogr., 24, 619–637, 1994. Huisman, S.&nbsp;E., Dijkstra, H.&nbsp;A., von&nbsp;der Heydt, A., and de&nbsp;Ruijter, W. P.&nbsp;M.: Robustness of Multiple Equilibria in the global ocean circulation, Geophys. Res. Lett., 36, L01610, <a href="http://dx.doi.org/10.1029/2008GL036322">https://doi.org/10.1029/2008GL036322</a>, 2009. Huisman, S.&nbsp;E., den Toom, M., Dijkstra, H.&nbsp;A., and Drijfhout, S.: An Indicator of the Multiple Equilibria Regime of the Atlantic Meridional Overturning Circulation, J. Phys. Oceanogr., 40, 551–567, 2010a. Huisman, S.&nbsp;E., Dijkstra, H.&nbsp;A., von&nbsp;der Heydt, A., and de&nbsp;Ruijter, W. P.&nbsp;M.: Does net $E-P$ determine the preference for Atlantic sinking?, PhD thesis, Chapter&nbsp;4, <a href="http://www.phys.uu.nl/&nbsp;shuisman/JPOsubmitted/">http://www.phys.uu.nl/&nbsp;shuisman/JPOsubmitted/</a> (last access: April&nbsp;2011), 2010b. Kuhlbrodt, T., Griesel, A., Montoya, M., Levermann, A., Hofmann, M., and Rahmstorf, S.: On the driving processes of the Atlantic meridional overturning circulation, Rev. Geophys., 45, RG2001, <a href="http://dx.doi.org/10.1029/2004RG000166">https://doi.org/10.1029/2004RG000166</a>, 2007. Levitus, S.: Climatological Atlas of the World Ocean, NOAA Professional Paper, 1982. Marotzke, J.: Abrupt climate change and thermohaline circulation: Mechanisms and predictability, P. Natl. Acad. Sci., 97, 1347–1350, <a href="http://dx.doi.org/10.1073/pnas.97.4.1347">https://doi.org/10.1073/pnas.97.4.1347</a>, 2000. Marotzke, J. and Willebrand, J.: Multiple equilibria of the global thermohaline circulation, J. Phys. Oceanogr., 21, 1372–1385, 1991. Meehl, G.&nbsp;A., Washington, W.&nbsp;M., Arblaster, J.&nbsp;M., and Hu, A.: Factors affecting climate sensitivity in global coupled models, J. Climate, 17, 1584–1596, 2004. Rahmstorf, S., Crucifix, M., Ganopolski, A., Goosse, H., Kamenkovich, I., Knutti, R., Lohmann, G., Marsh, R., Mysak, L.&nbsp;A., Wang, Z., and Weaver, A.&nbsp;J.: Thermohaline circulation hysteresis: A model intercomparison, Geophys. Res. Lett., 32, L23605, <a href="http://dx.doi.org/10.1029/2005GL023655">https://doi.org/10.1029/2005GL023655</a>, 2005. Schmittner, A., Silva, T. A.&nbsp;M., Fraedrich, K., Kirk, E., and Lunkeit, F.: Effects of Mountains and Ice Sheets on Global Ocean Circulation, J. Climate, <a href="http://dx.doi.org/10.1175/2010JCLI3982.1">https://doi.org/10.1175/2010JCLI3982.1</a>, in press, 2011. Smith, R. and Gent, P.: Reference manual for the Parallel Ocean Program (POP): Ocean component of the Community Climate System Model (CCSM2.0 and 3.0), Tech. rep. laur-02-2484, Los Alamos National Laboratory, Los Alamos, NM, 75&nbsp;pp., 2004. Smith, R.&nbsp;S., Gregory, J.&nbsp;M., Thorpe, R.&nbsp;B., and Rodriguez, J.: Response of the meridional overturning circulation in an idealised reverse world experiment, EGU General Assembly, session CL26 poster; Ref. No.: EGU2008-A-06893, 2008. Stommel, H.: Thermohaline convection with two stable regimes of flow, Tellus, 13, 224–230, 1961. Thomas, D.&nbsp;J.: Evidence for deep-water production in the North Pacific Ocean during the early Cenozoic warm interval, Nature, 430, 65–68, <a href="http://dx.doi.org/10.1038/nature02639">https://doi.org/10.1038/nature02639</a>, 2004. Thompson, L.&nbsp;A. and Cheng, W.: Water Masses in the Pacific in CCSM3, J. Climate, 21, 4514–4528, 2008. Trenberth, K.&nbsp;E., Olson, J.&nbsp;G., and Large, W.&nbsp;G.: A global ocean wind stress climatology based on ECMWF analyses, Tech. rep., National Center for Atmospheric Research, Boulder, CO, USA, 1989. Von&nbsp;der Heydt, A. and Dijkstra, H.&nbsp;A.: The effect of gateways on ocean circulation patterns in the Cenozoic, Global Planet Change, 62, 132–146, 2008. Weijer, W. A. D.&nbsp;H., Öksüzoglu, H., Wubs, F.&nbsp;W., and de&nbsp;Niet, A.&nbsp;C.: A fully-implicit model of the global ocean circulation, J. Comput. Phys., 192, 452–470, 2003. Wunsch, C.: Towards understanding the Paleocean, Quaternary Science Reviews, 29, 1960–1967, 2010. Zaucker, F., Stocker, T.&nbsp;F., and Broecker, W.&nbsp;S.: Atmospheric freshwater flux and their effect on the global thermohaline circulation, J. Geophys. Res., 99, 12443–12457, 1994.