Intradecadal Climate Stanzas for the Northwestern Pacific Ocean and Remote Influence on the Bering Sea International Journal of Climatology

A recent event in the Bering Sea during 2017–2020 saw localised anomalies of increased storminess, persistent southerly winds, warm surface waters and record minimums of wintertime sea ice that influenced a major ecosystem reorganisation including northward migration of fisheries. Ecological shifts impacted Alaskan coastal communities. Following this event, the Bering Sea returned to a typical range of environmental conditions. The Pacific Decadal Oscillation (PDO) represents a robust, recurring pattern of sea surface temperature (SST) and ocean–atmosphere climate variability centered over the northern mid-latitude Pacific Ocean basin. The resulting positive (negative) PDO pattern has anomalously cool (warm) SSTs in the interior northern North Pacific. The PDO had a short shift to positive values at the same time as the 2017–2020 Bering Sea event, and then returned to long-term negative values thereafter. We propose a teleconnection between northern North Pacific positive SST anomalies and Bering Sea conditions, mediated by the position of the Aleutian Low storm track. During a negative PDO phase, the gradient of overlying lower tropospheric air temperatures on the north side of the warm North Pacific SST pattern reinforces strong zonal flow of the Aleutian Low that inhibits advection of warm air temperatures into the central Bering Sea. PDO index values are often observed on decade and longer periods of one prevailing sign and thus give a mechanism for multi-year memory. We refer to sequential values of Bering Sea and PDO indicators as stanzas, although it is not possible to statistically determine if they represent clear regime shifts. The ongoing 2021–2025 negative PDO stanza, and its contrast with the previous 2017–2020 period, suggest a mechanism for the recent return of the Bering Sea to historical typical conditions, and provides a low chance of the Bering Sea returning to 2017–2020-like extreme conditions in the near future.