The influence of the AMOC variability on the atmosphere in CCSM3
MetadataShow full item record
KeywordAtmosphere-ocean interaction; North Atlantic Oscillation; Thermohaline circulation; Decadal variability
The influence of the Atlantic meridional overturning circulation (AMOC) variability on the atmospheric circulation is investigated in a control simulation of the NCAR Community Climate System Model, version 3 (CCSM3), where the AMOC evolves from an oscillatory regime into a red noise regime. In the latter, an AMOC intensification is followed during winter by a positive North Atlantic Oscillation (NAO). The atmospheric response is robust and controlled by AMOC-driven SST anomalies, which shift the heat release to the atmosphere northward near the Gulf Stream/North Atlantic Current. This alters the low-level atmospheric baroclinicity and shifts the maximum eddy growth northward, affecting the storm track and favoring a positive NAO. The AMOC influence is detected in the relation between seasonal upper-ocean heat content or SST anomalies and winter sea level pressure. In the oscillatory regime, no direct AMOC influence is detected in winter. However, an upper-ocean heat content anomaly resembling the AMOC footprint precedes a negative NAO. This opposite NAO polarity seems due to the southward shift of the Gulf Stream during AMOC intensification, displacing the maximum baroclinicity southward near the jet exit. As the mode has somewhat different patterns when using SST, the wintertime impact of the AMOC lacks robustness in this regime. However, none of the signals compares well with the observed influence of North Atlantic SST anomalies on the NAO because SST is dominated in CCSM3 by the meridional shifts of the Gulf Stream/North Atlantic Current that covary with the AMOC. Hence, although there is some potential climate predictability in CCSM3, it is not realistic.
Author Posting. © American Meteorological Society, 2013. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 26 (2013): 9774–9790, doi:10.1175/JCLI-D-12-00862.1.
Showing items related by title, author, creator and subject.
The Tokar Gap jet : regional circulation, diurnal variability, and moisture transport based on numerical simulations Davis, Shannon R.; Pratt, Lawrence J.; Jiang, Houshuo (American Meteorological Society, 2015-08-01)The structure, variability, and regional connectivity of the Tokar Gap jet (TGJ) are described using WRF Model analyses and supporting atmospheric datasets from the East African–Red Sea–Arabian Peninsula (EARSAP) region ...
Can Australian multiyear droughts and wet spells be generated in the absence of oceanic variability? Taschetto, Andrea S.; Sen Gupta, Alexander; Ummenhofer, Caroline C.; England, Matthew H. (American Meteorological Society, 2016-08-19)Anomalous conditions in the tropical oceans, such as those related to El Niño–Southern Oscillation and the Indian Ocean dipole, have been previously blamed for extended droughts and wet periods in Australia. Yet the extent ...
Low-latitude western north atlantic climate variability during the past millennium : insights from proxies and models Saenger, Casey P. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2009-09)Estimates of natural climate variability during the past millennium provide a frame of reference in which to assess the significance of recent changes. This thesis investigates new methods of reconstructing low-latitude ...