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Toward Climate Prediction: Interannual Potential Predictability due to an Increase in CO2 Concentration as Diagnosed from an Ensemble of AO GCM Integrations.
- Source :
- Journal of Climate; Sep2008, Vol. 21 Issue 18, p4607-4628, 22p, 10 Graphs, 6 Maps
- Publication Year :
- 2008
-
Abstract
- Predictability studies of the second kind are often carried out to address the potential in predicting atmospheric variables based on knowledge of changes in sea surface temperature (SST). Here a predictability study of the second kind is performed for the coupled atmosphere–ocean system based on knowledge of changes in CO<subscript>2</subscript> concentration. The focus is on potential predictabilities obtained after imposing a CO<subscript>2</subscript> forcing over a short time period (i.e., a few years), which are less sensitive to the exact future time evolution of the CO<subscript>2</subscript> forcing. Potential predictability is measured by the ensemble mean difference resulting from the CO<subscript>2</subscript> forcing relative to the ensemble spread subjected to the same forcing. The measure is calculated from a 50-member prediction ensemble obtained from an atmosphere–ocean GCM forced by a 3% increase in CO<subscript>2</subscript> concentration per year and a reference ensemble obtained under a constant CO<subscript>2</subscript> concentration. The largest potential predictabilities are found in and over the Southern Ocean. The origin of these predictabilities is a positive feedback involving interactions between the atmosphere and the upper ocean. An increase in the meridional gradient of SST resulting from a large SST increase in the southern subtropics leads to a strengthening of atmospheric circulation, and from that increases in surface zonal wind stress result. The latter enhances the northward Ekman transport over the southern high latitudes, which transports polar water equatorward, whereby maintaining the meridional temperature gradient. Potential predictability is also found in the deep ocean, characterized by the downward propagation of the surface warming within a few years through two “corridors,” located at 40°S and 40°N and extending from the near surface to about 3000–3500 m. The warming in the atmosphere and the upper ocean is reduced by half because of this downward heat propagation. [ABSTRACT FROM AUTHOR]
- Subjects :
- CLIMATOLOGY
ATMOSPHERE
METEOROLOGY
OCEAN
CARBON dioxide
GENERAL circulation model
Subjects
Details
- Language :
- English
- ISSN :
- 08948755
- Volume :
- 21
- Issue :
- 18
- Database :
- Complementary Index
- Journal :
- Journal of Climate
- Publication Type :
- Academic Journal
- Accession number :
- 34403228
- Full Text :
- https://doi.org/10.1175/2008JCLI1954.1