Based on a mixed layer temperature budget, these anomalies were caused by lower than normal rates of the loss of heat from the ocean to the atmosphere and of relatively weak cold advection in the upper ocean.
Both of these mechanisms can be attributed to an unusually strong and persistent weather pattern featuring much higher than normal sea level pressure over the waters of interest. This anomaly was the greatest observed in this region since at least the 1980s.
The region of warm sea surface temperature anomalies subsequently expanded and reached coastal waters in spring and summer 2014, introducing impacts on fisheries and regional weather. Sea surface temperature anomalies in this region also affect air temperatures downwind in Washington state.
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