Ocean Observing and Climate
OVAC Theme 2 - NAO-Related SST Anomaly Decay and Potential Feedback
SOC SST and Qnet composite anomalies at lags of 1-3 months with respect to a subset of extreme NAO+ winter months in the period 1980-1997, units are deg C for SST and Wm^-2 for Qnet. Only anomalies that are significant at the 95% level are shown, lag intervals are in units of months.
One of the key research topics under this theme is the identification of the different sets of mechanisms and scales associated with the modification of the atmosphere by the ocean. We have addressed this issue with regard to the potential feedback of sea surface temperature (SST) anomalies that are generated by the North Atlantic Oscillation (NAO) onto the atmosphere via changes in the air-sea heat exchange. The anomalous atmospheric circulation associated with the NAO generates a tripole pattern in SST. The subsequent evolution of this pattern following extreme positive states of the NAO in the period 1980-1997 has been investigated via a lagged composite analysis of the SOC flux dataset.
Composite fields of SST and net heat flux (Qnet) have been calculated at monthly intervals up to 12 months after those contained in a subset of winter months in the period considered with normalised NAO index > 1.5. The fields for lags of 1, 2 and 3 months are shown in the figure, only features that are significant at the 95% level are included. At lags of 1 and 2 months the main elements of the NAO generated SST field persist. Over subsequent months these features weaken on a timescale that increases with latitude, the cold anomaly to the south of Greenland is still significant at a lag of 5 months (not shown). The Qnet composites have been investigated to see whether the SST anomalies are coincident with changes in the net ocean-atmosphere heat exchange. No significant pattern is seen suggesting that any signal is dominated by heat flux anomalies associated with unrelated atmospheric variability at these timescales.
For more information, see Josey et al., 2001.
Links to OVAC Theme 2 Research
Rainfall Variability Atlantic Freshwater SST Anomalies Flux Parameterisations
