North Pacific atmospheric and SST anomalies in 1997: Links to ENSO?

In the summer of 1997, positive sea surface temperature anomalies (SSTA) ex tended across the Gulf of Alaska (GOA) and into the eastern Bering Sea (EBS ). The SSTA in the EBS are at least in part due to atmospheric causes. Anom alously high 925 mb temperatures and 700 mb geopotential heights and low 92 5 mb relative humidities, and hence decreased low cloud cover, occurred ove r the region during April to August. This resulted in enhanced warming of t he GOA and EBS owing to increased insolation. The anomalous solar heating w as particularly great in the EBS from mid-May to mid-July. The pattern of p ositive 700 mb height anomalies for April to August 1997 is similar to its counterpart formed by compositing the April to August anomalies that occurr ed during previous El Ninos. The positive equatorial SSTA for 1997 was one of the strongest on record for summer months. The existence of an equatoria l/high-latitude connection and the strength of the summer equatorial SSTA i n 1997 suggest an El Nino/Southern Oscillation (ENSO) influence in the GOA and EBS. The warming in the Bering Sea and North Pacific during summer 1997 appears to be due in part to the confluence of three meteorological factor s which favoured clear skies. There was not only an El Nino influence, but also a decadal trend toward higher 700 mb geopotential heights and a partic ularly strong blocking ridge weather pattern over the Gulf of Alaska in May .