EFFECTS of the RECENT WARMING OF THE NE PACIFIC OCEAN

Strongly positive sea surface temperature (SST) anomalies have prevailed in the NE Pacific Ocean since 2013. The effects of this abnormally warm water, sometimes referred to as the “blob”, are examined. The initiation of these conditions can be attributed to anomalous air-sea interactions associated with a strong and persistent ridge of higher than normal sea-level pressure (SLP), which resulted in reduced seasonal cooling of the upper ocean during the winter of 2013-14. Upon formation, this warm water appears to have produced substantial effects on the regional marine ecosystem, and on the weather along the west coast of North America. From the biological perspective, the latter portion of 2014 featured an abrupt shift of copepod populations from predominantly sub-arctic to sup-tropical species in the Pacific Northwest, with consequences for higher trophic levels. The latter region has experienced systematically warmer than normal air temperatures since early 2014 and this result can be attributed in part due to the underlying SST anomalies upstream, based on the relationships between SST and atmospheric boundary layer thermodynamic properties found in the observational record back to the 1940s.