The role of ENSO in global ocean temperature changes during 1955–2011 simulated with a 1D climate model
- 433 Downloads
Global average ocean temperature variations to 2,000 m depth during 1955–2011 are simulated with a 40 layer 1D forcing-feedback-mixing model for three forcing cases. The first case uses standard anthropogenic and volcanic external radiative forcings. The second adds non-radiative internal forcing (ocean mixing changes initiated in the top 200 m) proportional to the Multivariate ENSO Index (MEI) to represent an internal mode of natural variability. The third case further adds ENSO-related radiative forcing proportional to MEI as a possible natural cloud forcing mechanism associated with atmospheric circulation changes. The model adjustable parameters are net radiative feedback, effective diffusivities, and internal radiative (e.g., cloud) and non-radiative (ocean mixing) forcing coefficients at adjustable time lags. Model output is compared to Levitus ocean temperature changes in 50 m layers during 1955–2011 to 700 m depth, and to lag regression coefficients between satellite radiative flux variations and sea surface temperature between 2000 and 2010. A net feedback parameter of 1.7Wm−2 K−1 with only anthropogenic and volcanic forcings increases to 2.8Wm−2 K−1 when all ENSO forcings (which are one-third radiative) are included, along with better agreement between model and observations. The results suggest ENSO can influence multi-decadal temperature trends, and that internal radiative forcing of the climate system affects the diagnosis of feedbacks. Also, the relatively small differences in model ocean warming associated with the three cases suggests that the observed levels of ocean warming since the 1950s is not a very strong constraint on our estimates of climate sensitivity.
Key wordsClimate sensitivity climate change climate modeling El Nino Southern Oscillation ocean heat content
Unable to display preview. Download preview PDF.
- Intergovernmental Panel on Climate Change (IPCC), 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon et al., Cambridge Univ. Press, New York, 996 pp.Google Scholar
- Levitus, S., J. I. Antonov, T. P. Boyer, R. A. Locarnini, H. E. Garcia, and A. V. Mishonov, 2009: Global ocean heat content 1955–2008 in light of recently revealed instrumentation Problems. Geophys. Res. Lett., 36, L07608, doi:10.1029/2008GL037155.Google Scholar
- Lindzen, R. S., 2002: Do deep ocean temperature records verify models? Geophys. Res. Lett., 29, 10.1029/2001GL014360.Google Scholar
- Meinshausen, M., and Coauthors, 2011: The RCP Greenhouse Gas Concentrations and their Extension from 1765 to 2300. Climatic Change, doi:10.1007/s10584-011-0156-z.Google Scholar
- Rayner, N. A., P. Brohan, D. E. Parker, C. K. Folland, J. J. Kennedy, M. Vanicek, T. Ansell and S. F. B. Tett, 2006: Improved analyses of changes and uncertainties in sea surface temperature measured in situ since the mid-nineteenth century: the HadSST2 data set. J. Climate, 19, 446–469.CrossRefGoogle Scholar
- Solomon, A., and M. Newman, 2012: Reconciling disparate 20th century Indo-Pacific ocean temperature trends in the instrumental record. Nature Climate Change, 2, 691–699, doi:10.1038/nclimate1591.Google Scholar
- Spencer, R. W., and W. D. Braswell, 2010: On the diagnosis of radiative feedback in the presence of unknown radiative forcing. J. Geophys. Res., 115, doi:10.1029/2009JD013371.Google Scholar