Annual summaries of ocean indicators of the northern California Current from 2008 to present.
Like 2015, many ocean ecosystem indicators suggest 2016 to be another poor year for juvenile salmon survival, the second consecutive year of poor ocean conditions. The PDO was strongly positive (warm) throughout 2016, coinciding with the continuing of the anomalously warm ocean conditions in the NE Pacific initiated by “The Blob” that began in the fall of 2013. Strong El Niño conditions at the equator also persisted throughout 2015 until May of 2016. Sea surface and upper 20 m water temperatures off Newport, Oregon, remained warmer than usual (+2°C) throughout most of 2016, continuing two consecutive years of anomalously warm ocean conditions. The zooplankton community remained in a lipid-deplete state throughout 2016, with the lowest biomass of lipid-rich northern copepods and the highest species richness observed in the 19-year time series.
An anomalously warm water mass began to form in the Gulf of Alaska during autumn 2013 due to a lack of cyclonic storms that usually mix and subsequently cool the water column. This warm water mass was aptly named the Blob by Washington State Climatologist Nick Bond. The Blob spread across the entire North Pacific in spring 2014, producing temperature anomalies of 3 to 4.5°C by summer 2014. Locally, strong upwelling winds kept the Blob offshore of Oregon during summer 2014, but by mid-September, winds relaxed, and the Blob flooded continental shelf waters with anomalously warm tropical/subtropical water. This resulted in a complete replacement of the “cold water, lipid-rich” food chain with a “warm-water, lipid poor” food chain. By winter (Jan-Mar) 2015, the SST pattern across the Pacific resembled the positive PDO pattern, and this SST pattern continued through all of 2015 and 2016.
While the warm Blob was moving east in the North Pacific Current in spring of 2014, an ENSO warm phase developed at the equator, creating the first pulse of warm water typical of an El Niño along the eastern equatorial Pacific. However, a full El Niño did not develop, but an El Niño did develop the following year, as pulses of warm water moved eastward along the equator in spring and autumn 2015, producing extremely warm surface temperatures from Nov 2015-January 2016. This El Niño event evolved into the strongest event in 19 years and likely reached northern California Current by summer 2016. Thus, this El Niño event further exacerbated poor feeding conditions experienced by salmon, other resident fish, bird and mammal species as well as long-distance migrants since mid-2014/early 2015.
The ecosystem effects of the Blob and El Niño have not yet been fully documented. Relative to the lower trophic levels, two observation are noteworthy: first, during the Blob, at least 18 tropical copepod species occurred off the Oregon coast that have never been seen before, indicating that the source waters for the Blob were from a more southerly/offshore region than has been observed in the past. Second, the lowest biomass anomalies of lipid-rich copepods and the highest biomass anomalies of subtropical lipid-deplete copepods occurred over two consecutive years (2015 and 2016), marking the longest period of poor feeding conditions for higher trophic levels since sampling began in 1996. However, the copepod species we are observing now (January 2017) are the same as those observed during any normal winter, with a dominance of subtropical neritic species that are transported to Oregon from coastal waters of central/southern California by the Davidson Current, which flows poleward from October to March in most years. This suggests that the ecosystem of the northern California Current may become more “normal” in 2017.
Negative impacts have already occurred for adult coho salmon. These are fish that went to sea in spring 2014 and 2015. Adults returns to Bonneville Dam in fall 2015 and 2016 were among the poorest on record (42,000 and 37,000 adults respectively), similar to returns noted for fish that went to sea in spring of the 1998 El Niño event (returns in 1999 of 40,000 adults). For Chinook salmon, spring-run juveniles that went to sea in 2014 returned in spring 2016 at “average” levels. The spring Chinook salmon that went to sea in 2015 and 2016 will not return as adults until 2017 and 2018 at the earliest. For fall-run Chinook, which spend at least three years at sea, impacts will not be observed until 2017 (for 2014 out-migrants) and several years after (for 2015 and 2016 out-migrants). Given the poor ocean conditions when these fish first went to sea, it will be interesting to note how that affected their adult returns in 2017 and 2018.
The PDO turned positive (warm phase) in January 2014 and has remained strongly positive throughout 2015 and 2016, reaching values similar to what was observed during the 1997-1998 El Niño but over a longer period than the 1997-1998 El Niño. Strong El Niño conditions signaled by high values of the Ocean Niño Index (ONI) occurred throughout 2015 until SST values at the equator became neutral in June 2016.
Following higher than average downwelling in the winter of 2015-2016, the upwelling season began (spring transition) on 23 March 2016, which is very early compared to the 40-year climatological mean of 13 April. Although the onset of equatorward winds, which marks the beginning of the upwelling season, started early, the winds were very weak, and upwelling was weak until mid-April. After mid-April, the cumulative upwelling was just above average until it ended on 29 September, slightly earlier than the 40-year climatology. Despite the early onset and end to the upwelling season, the total amount of upwelling in 2016 was just above average.
The anomalous warm ocean conditions in the NE Pacific from the Blob arrived on the Oregon shelf in Sept 2014 with temperature anomalies of +4°C and continued to dominate the surface ocean temperatures for most 2015 and 2016. Sea surface temperatures off Newport remained warmer than usual (+1.5 - 2°C) throughout most of 2016, apart from brief cooling towards the end of June and during August when upwelling was the strongest.
The upper 20 m of the water column on the shelf and the deep water on the shelf and slope were dominated by water anomalously warm and fresh throughout the winter before the onset of upwelling. However, during the upwelling season, the deep water on the shelf and slope was average, being cold and salty.
Similar to 2015, in 2016, this seasonal shift from a warm copepod community to a cold summer community did not occur, which is the second consecutive year that this biological spring transition did not occur. The zooplankton community remained in a lipid-deplete state throughout 2016, with the lowest biomass of lipid-rich northern copepods and the highest biomass of small tropical and sub-tropical southern copepods we’ve observed in the time series. The species richness also remained high throughout 2016, peaking during the summer months when species richness is generally the lowest.
The winter (Jan-March) biomass of larval stages of fish species common in salmon diets was above average this year, ranking fifth-highest over the 19 years of data. However, the species composition of the wintertime larval fish community included high proportions of larval rockfish and anchovies, which are generally indicators of poor feeding conditions for salmon.
Unusual warm water events related to the Blob and large El Niño events provide natural experiments that may serve as proxies to study the potential impacts of a warmer ocean on the pelagic ecosystem and associated fisheries of the California Current. For example, the superposition of strong upwelling on a warmer coastal ocean environment in 2015 and 2016 may serve as a model for the future in that the persistence of the warm water planktonic species through the periods of strong upwelling in summer suggests that even an increase in wind-forced upwelling may not in the future be able to replace a warm-water zooplankton ecosystem with a more lipid-rich cold-water species assemblage. This situation would negatively impact the salmon populations in the Pacific Northwest, long-distance migratory species, and other marine resources.
Two expectations from global climate models were far exceeded during the Blob: the north Pacific warmed quickly by 4.5°C, and many taxa shifted north by one to two thousand km in a few months. Global climate models are unable to anticipate anomalous warming events such as the Blob or major El Niño events, nor can they detect large-scale events related to shifts in the distribution of pelagic species. Thus, long-term ecological observation programs must be maintained, and others initiated so that ecosystem impacts of future unusual events can be anticipated and understood in greater detail.
Cape Shirreff Field Camp, Livingston Island, Antarctica. Credit NOAA Fisheries/Sergio Morales
NOAA Ship Bell M. Shimada during 2010 Pacific Hake Inter-Vessel Calibration off Eureka, California. Credit: NOAA
