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Frequency- or amplitude-dependent effects of the Atlantic meridional overturning on the tropical Pacific Ocean

(a) AMO index (solid) and maximum AMOC at 35N (dashed) for standard ensemble member 4. (b) Lag correlation between maximum AMOC at 35N and the AMO index. For positive lags the AMOC is leading. The green band indicates the 95% confidence interval based on a decorrelation time scale of 5 years. (c) Regression (°C/°C) of SST on the AMO index. (d) Regression (°C/Sv) of SST on maximum AMOC at 35N. (e) Regression (°C/Sv) of annual mean SST on annual mean maximum AMOC at 35N. Unless stated otherwise, in all panels data are 5-yr running means of anomalies with respect to the ensemble mean. In (b)-(e), data of all standard ensemble members have been used. Areas in (c)-(e) for which the p-value exceeds 10% in a two-sided t-test are not shaded.
GJ van Oldenborgh, LA te Raa, HA Dijkstra, SY Philip

Using the ECHAM5/MPI-OM model, we study the relation between the variations in the Atlantic meridional overturning circulation (AMOC) and both the Pacific sea surface temperature (SST) and the El Niño-Southern Oscillation (ENSO) amplitude. In a 17-member 20C3M/SRES-A1b ensemble for 1950-2100 the Pacific response to AMOC variations associated with the Atlantic Multidecadal Oscillation (AMO) is very small. In a 5-member hosing ensemble where the AMOC collapses due to a large freshwater anomaly, the Pacific response is large and in correspondence with previous work. Our results show that the connection between AMOC and ENSO depends very strongly on the frequency and/or the amplitude of the AMOC variations. Interannual AMOC variations, decadal AMOC variations and an AMOC collapse are associated with entirely different responses in the Pacific Ocean.

Bibliografische gegevens

GJ van Oldenborgh, LA te Raa, HA Dijkstra, SY Philip. Frequency- or amplitude-dependent effects of the Atlantic meridional overturning on the tropical Pacific Ocean
published, Ocean Science, 2009, 5

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