New paper finds excuse #55 for the ‘pause’ in global warming: Reduced warming in N. Atlantic subpolar gyre
A paper published today in the Journal of Climate finds, “the sea level rise in the North Atlantic subpolar gyre developed at a reduced rate in the 2000s compared to rates in the 1990s” and “the heat content balance ([is assumed] equivalent [to] variations in the sea level)” and that this “low-frequency variability in the North Atlantic subpolar gyre relates to the propagation of Atlantic meridional overturning circulation (AMOC) variations from the deep-water formation region to mid-latitudes in the North Atlantic, which might have the implications for recent global surface warming hiatus.” Thus, a decline in the rate of heat content and thermosteric sea level rise of the North Atlantic subpolar gyre affected the propagation [speed] of the Atlantic meridional overturning circulation (AMOC) and might be a cause for the “recent global surface warming hiatus.” A prior paper has also related the “hiatus” to natural variability of heat content changes in the AMOC, but not specifically related to the North Atlantic subpolar gyre as in this new paper. The North Atlantic subpolar gyre has been linked to the natural North Atlantic Oscillation [NAO], which in-turn has been linked to solar activity. The paper adds to many others attempting to explain the 18-26 year “pause” or “hiatus” in global warming. Journal of Climate 2014 ; e-View doi: http://dx.doi.org/10.1175/JCLI-D-12-00670.1 Climate signals in the mid to high latitude North Atlantic from altimeter observations Feili Li1,2 Young-Heon Jo1,3 Xiao-Hai Yan1,4W. Timothy Liu5 1 College of Earth, Ocean and Environment, University of Delaware, Newark, DE 2 now at Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC 3 now at Department of Oceanography, Pusan National University, Busan, South Korea 4 University of Delaware/Xiamen University Joint Institute of Coastal Research and Management, Newark, DE 5 Jet Propulsion Laboratory 300-323, California Institute of Technology, Pasadena, CA Abstract The variability of the sea surface height anomaly (SSHA) in the mid- to high-latitude North Atlantic for the period of 1993 – 2010 was investigated using the Ensemble Empirical Mode Decomposition to identify the dominant timescales. Sea level variations in the North Atlantic subpolar gyre (SPG) are dominated by the annual cycle and the long-term increasing trend. In comparison, the SSHA along the Gulf Stream (GS) is dominated by variability at intra-seasonal and annual timescales. Moreover, the sea level rise in the SPG [North Atlantic subpolar gyre] developed at a reduced rate in the 2000s compared to rates in the 1990s, which was accompanied by rebound in SSHA variability following a period of lower variability in the system. These changes in both apparent trend and low-frequency SSHA oscillations reveal the importance of low-frequency variability in the SPG. To identify the possible contributing factors for these changes, the heat content balance (equivalent variations in the sea level) in the subpolar region was examined. The results indicate that horizontal circulations [ocean oscillations] may primarily contribute to the interannual to decadal variations, while the air-sea heat flux is not negligible at annual timescale. Furthermore, the low-frequency variability in the SPG [North Atlantic subpolar gyre] relates to the propagation of Atlantic meridional overturning circulation (AMOC) variations from the deep-water formation region to mid-latitudes in the North Atlantic, which might have the implications for recent global surface warming hiatus.
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