26 December 2014

Is AMOC more predictable than North Atlantic heat content?


The Atlantic Meridional Overturning Circulation (AMOC) would seem to be a component of variability that decadal prediction efforts should focus on due to its direct influence on meridional heat transport in the North Atlantic. On the other hand, what matters for climate prediction is not whether AMOC is predictable by some absolute measure but rather whether it is more or less predictable than North Atlantic heat content. For it is heat content and its sea surface temperature manifestation that have direct societal relevance through their influence on surface climate. Here we applied techniques developed in our previous studies to the CMIP5 models to quantify and compare predictability properties of the AMOC and heat content in the North Atlantic. The results were mixed. When considering generic fluctuations of annual means we found the AMOC is less predictable than heat content. On the other hand,  there are components of AMOC variability that are much more predictable than its generic variations, and these components tend to be more predictable than generic component of North Atlantic heat content. The most predictable of these may be predictable for nearly 2 decades. We were able to isolate these components using two methods. Our results carry implications for decadal predictions and the design of observational and assimilation systems that support the predictions .

G Branstator
Branstator, G, and H Teng.  2014.  "Is AMOC More Predictable than North Atlantic Heat Content?"  Journal of Climate 27: 3537–3550, doi:10.1175/JCLI-D-13-00274.1.