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Frequency Domain Multimodel Analysis of the Response of Atlantic Meridional Overturning Circulation to Surface Forcing

MacMartin, Douglas G. and Tziperman, Eli and Zanna, Laure (2013) Frequency Domain Multimodel Analysis of the Response of Atlantic Meridional Overturning Circulation to Surface Forcing. Journal of Climate, 26 (21). pp. 8323-8340. ISSN 0894-8755. doi:10.1175/JCLI-D-12-00717.1.

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The dynamics of the Atlantic meridional overturning circulation (AMOC) vary considerably among different climate models; for example, some models show clear peaks in their power spectra while others do not. To elucidate these model differences, transfer functions are used to estimate the frequency domain relationship between surface forcing fields, including sea surface temperature, salinity, and wind stress, and the resulting AMOC response. These are estimated from the outputs of the Coupled Model Intercomparison Project phase 5 (CMIP5) and phase 3 (CMIP3) control runs for eight different models, with a specific focus on Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1 (GFDL CM2.1), and the Community Climate System Model, version 4 (CCSM4), which exhibit rather different spectral behavior. The transfer functions show very little agreement among models for any of the pairs of variables considered, suggesting the existence of systematic model errors and that considerable uncertainty in the simulation of AMOC in current climate models remains. However, a robust feature of the frequency domain analysis is that models with spectral peaks in their AMOC correspond to those in which AMOC variability is more strongly excited by high-latitude surface perturbations that have periods corresponding to the frequency of the spectral peaks. This explains why different models exhibit such different AMOC variability. These differences would not be evident without using a method that explicitly computes the frequency dependence rather than a priori assuming a particular functional form. Finally, transfer functions are used to evaluate two proposed physical mechanisms for model differences in AMOC variability: differences in Labrador Sea stratification and excitation by westward-propagating subsurface Rossby waves.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
MacMartin, Douglas G.0000-0003-1987-9417
Tziperman, Eli0000-0002-7998-5775
Additional Information:© 2013 American Meteorological Society. Manuscript received 30 September 2012, in final form 6 March 2013. This work was supported by Grant DE-SC0004984 from the DOE Climate and Environmental Sciences Division, Office of Biological and Environmental Research (DM and ET). LZ was supported by the U.K. Natural Environment Research Council, Grant NE/J00586X/1. Eli Tziperman thanks the Weizmann Institute for its hospitality during parts of this work. We acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups (listed in Table 1) for producing and making available their model output. For CMIP the U.S. Department of Energy’s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004984
Natural Environment Research Council (NERC)NE/J00586X/1
Subject Keywords:Atlantic Ocean; Meridional overturning circulation; Ocean dynamics; Climate models
Issue or Number:21
Record Number:CaltechAUTHORS:20140221-095813127
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Official Citation:MacMartin, Douglas G., Eli Tziperman, Laure Zanna, 2013: Frequency Domain Multimodel Analysis of the Response of Atlantic Meridional Overturning Circulation to Surface Forcing. J. Climate, 26, 8323–8340. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43924
Deposited By: Tony Diaz
Deposited On:28 Feb 2014 16:23
Last Modified:10 Nov 2021 16:45

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