Effects of solar irradiance forcing on the ocean circulation and sea-ice in the North Atlantic in an isopycnic coordinate ocean general circulation model

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Otterå, Odd Helge ; Drange, Helge (2004)

The sensitivity of the ocean circulation to changes in solar irradiance is examined using an isopycnic coordinate, global ocean general circulation model (OGCM) coupled to a thermodynamic/dynamic sea-ice model. In the experiments, changes in the surface radiation forcing are calculated based on orbital data assuming that the atmospheric conditions are otherwise unchanged. Two sensitivity experiments are run with the ocean-sea-ice model: one with high and one with low solar irradiance representative of the last interglacial and glacial periods, respectively. The results show that the Atlantic merdional overturning circulation (AMOC) is increased (reduced) in response to lower (higher) summer solar irradiance. It is found that changes in the Arctic sea-ice volume and area are the main reason for the response. For the low solar irradiance case, less sea-ice is melted in summer leading to a saltier Arctic Ocean. This saltier water is then advected into the sinking regions in the winter, enhancing the intermediate and deep water formation. For the high solar irradiance case, a similar, but opposite, response occurs. The results thus confirm that the AMOC is very sensitive to external forcing. It is suggested that the scheme used for calculating changes in solar irradiance could prove useful when conducting glacial inception studies with fully coupled atmosphere-ocean models.
  • References (43)
    43 references, page 1 of 5

    Bentsen, M. 2002. Modelling Ocean Climate Variability of the North Atlantic and the Nordic Seas. PhD Thesis. Department of Mathematics, University of Bergen and Nansen Environmental and Remote Sensing Center, Bergen, Norway.

    Bentsen, M. and Drange, H. 2000. Parametrizing surface fluxes in ocean models using the NCEP/NCAR reanalysis data. In: RegClim General Technical Report No. 4, Norwegian Institute for Air Research, Kjeller, Norway.

    Bentsen, M., Evensen, G., Drange, H. and Jenkins, A. D. 1999. Coordinate transformation on a sphere using conformal mapping. Mon. Wea. Rev. 127, 2733-2740.

    Berger, A. and Loutre, M. F. 1991. Insolation values for the climate of the last 10 million years. Quat. Sci. Rev. 10, 297-317.

    Bleck, R., Dean, S., Keefe, M. O. and Sawdey, A. 1995. A comparison of data-parallell and message-passing versions of the Miami isopycnic coordinate ocean model. Parallell Comput. 21, 1695-1720.

    Bleck, R., Rooth, C., Hu, D. and Smith, L. T. 1992. Salinity-driven thermocline transients in a wind- and thermohaline-forced isopycnic coordinate model of the North Atlantic. J. Phys. Oceanogr. 22, 1486- 1505.

    Boyle, E. 1995. Last-glacial-maximum North Atlantic deep water: on, off or somewhere in-between? Phil. Trans. R. Soc. London B 348, 243-253.

    Broecker, W. S. 1991. The great ocean conveyor. Oceanography 4, 79- 89.

    Broecker, W. S. and Denton, G. H. 1990. What drives glacial cycles? Sci. Am. 262, 49-56.

    Budyko, M. I. 1969. The effect of solar radiation variations on the climate of the earth. Tellus 21, 611-619.

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