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Is the 2004–2012 reduction of the Atlantic meridional overturning circulation significant?
Author(s) -
Roberts C. D.,
Jackson L.,
McNeall D.
Publication year - 2014
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl059473
Subject(s) - climatology , coupled model intercomparison project , environmental science , general circulation model , climate model , zonal and meridional , range (aeronautics) , baseline (sea) , climate change , geology , oceanography , materials science , composite material
The Atlantic meridional overturning circulation (AMOC) at 26.5°N weakened by −0.53 sverdrup (Sv)/yr between April 2004 and October 2012. To assess whether this trend is consistent with the expected “noise” in the climate system, we compare the observed trend with estimates of internal variability derived from 14 control simulations from the Climate Model Intercomparison Project 5 (CMIP5). Eight year trends of −0.53 Sv/yr are relatively common in two models but are extremely unusual (or out of range) in the other 12. However, all 14 models underestimate AMOC variability on interannual time scales. To account for this bias, we estimate plausible upper limits of internal AMOC variability by combining the temporal correlation characteristics of the AMOC from CMIP5 models with an observational estimate of interannual variability. We conclude that the observed AMOC trend is not significantly different ( p > 0.01) from plausible estimates of internal variability. Detecting the influence of external climate forcings on the AMOC will require more than one decade of continuous observations.