Investigating SST influence on the North Atlantic Oscillation using the NCAR community atmospheric model

The North Atlantic Oscillation (NAO) contributes greatly to the climate of the Northern Hemisphere, but many open issues remain about the mechanisms driving NAO variability. Evidence suggests the underlying ocean is one pathway in which some predictability of NAO evolution may exist. The NAO produces an anomalous sea surface temperature (SST) tripole pattern and a longstanding question is how the SST tripole pattern feeds back on to the atmosphere. This study investigates this question using the NCAR community atmospheric model (CAM). Ten one-year CAM runs were forced with the SST tripole pattern during the winter season (perturbed) and compared to ten one-year control runs. The model results show the SST tripole leads to a strengthened NAO. This is primarily a response from a negative SST anomaly area south of Greenland that produces a barotropic positive atmospheric pressure response in the early winter. This creates an increased zone of baroclinicity in the North Atlantic that leads to a strengthened "Icelandic low" in late winter. The findings imply the SST tripole does feedback on to the NAO however more research is required to fully understand this relationship.