Drivers of past and future Southern Ocean change: Stratospheric ozone versus greenhouse gas impacts by M. Sigmond, M. C. Reader, J. C. Frye & N. P. Gillett, GRL, 38

Geophysical Research Letters, 38 (2011) L12601; doi: 10.1029/2011GL047120

Drivers of past and future Southern Ocean change: Stratospheric ozone versus greenhouse gas impacts

Key points:

• GHG and stratospheric ozone trends drive changes in the ocean circulation
• The ozone impact on the ocean circulation exceeds that due to GHGs up to ∼2035
• Previously neglected ozone trends should be included in ocean modeling studies

M. Sigmond

Department of Physics, University of Toronto, Toronto, Ontario, Canada

M. C. Reader

School of Earth and Ocean Sciences, University of Victoria, Victoria, BC, Canada

J. C. Fyfe

Canadian Centre for Climate Modelling and Analysis, Environment Canada, Victoria, BC, Canada

N. P. Gillett

Canadian Centre for Climate Modelling and Analysis, Environment Canada, Victoria, BC, Canada

Abstract

We study the separate impacts of changing atmospheric greenhouse gas (GHG) and stratospheric ozone concentrations on past (1960–2010) and future (2010–2100) Southern Ocean conditions. To this end we employ a coupled atmosphere-ocean model with interactive stratospheric chemistry. In our model we separately prescribe: (i) GHGs that monotonically increase to 2100 and (ii) ozone depleting substances (ODSs) that rapidly increase to a maximum in 1995 and then slowly return to 1960 values around 2100, following moderate emission scenarios. Past GHG and ODS changes in our model drive, in about equal measure in the annual mean, poleward intensified surface winds which act to strengthen the sub polar meridional ocean circulation cell and Antarctic Circumpolar Current (ACC). Future GHG-induced oceanic changes continue nearly monotonically to 2100, while the ODS-induced ACC transport peaks, and then reverses, a couple of decades after the ODS maximum in 1995. The ODS impact on ACC transport exceeds the corresponding GHG impact up to the second quarter of the 21st century, a result that highlights the importance of often-neglected stratospheric ozone trends for the simulation of the ocean circulation.

Received 21 February 2011; accepted 3 May 2011; published 16 June 2011.

Citation: Sigmond, M., M. C. Reader, J. C. Fyfe, and N. P. Gillett (2011), Drivers of past and future Southern Ocean change: Stratospheric ozone versus greenhouse gas impacts, Geophys. Res. Lett., 38, L12601, doi:10.1029/2011GL047120.

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