2011 Ocean Indicators Summary
A summary of ocean indicators of the northern California Current for 2011.
The trend of cold ocean conditions that started in September 2007 was interrupted by a moderately strong El Niño event in mid‑2009: this warming event continued from August 2009-May 2010 and had a negative influence on productivity in the coastal waters of the northern California Current.
However, in June 2010, La Niña (cold ocean) conditions returned and have continued throughout 2011. Should these conditions persist into spring 2012, ocean conditions will be the best observed in the past few decades for Pacific salmon juveniles that enter the sea during spring (spring Chinook, coho, and steelhead). Juvenile migrants entering the ocean in spring 2012 would have very high ocean survival.
There is some uncertainty in this outlook: some NOAA forecast models predict a weakening La Niña, whereas others predict a strengthening. Regardless, cold ocean conditions will likely prevail through spring.
Here we discuss each of our indicators in the context of how our measurements in 2011 compare to those made by our research team since 1998.
Pacific Decadal Oscillation
The PDO is now once again negative; values have been strongly negative since July 2011 (> -1.3). The PDO value for November 2011 (-2.33) was the lowest observed since the early 1950s and 1960s and ranks as the 13th lowest since 1900.
The Oceanic Nino Index (ONI)
The ONI has a value of –0.7 as of November 2011; although not strongly negative, it should be noted that this value has become more negative each month since July 2010.
Sea Surface Temperature (SST)
In winter 2010-2011, SST values were colder than usual, at -0.5°C below normal. In summer 2011, SST values were also cooler than normal, at -0.66°C below normal.
Upwelling in 2011 was initiated on 13 April (day 105), near the average start date, and continued until mid-September (day 256). Thus, upwelling ended nearly a month earlier than the 10 October average (day 283). The upwelling season was initially weak in April and May and did not begin to strengthen until early June, resulting in a negative upwelling anomaly for April-May. This was the 3rd worst start to the upwelling season observed in the past 14 years.
Physical Spring Transition
The spring transition date in 2011 came on day 105 (13 April); however, northerly winds were weak and inconsistent until day 160 (9 June). Thus, even though the strong winter storms ended in early April, consistent upwelling winds did not commence until early June, after which they were quite strong. The upwelling season ended early, on 13 September.
Deep Water Temperature and Salinity
As a result of relatively weak upwelling in spring 2011, deep waters on the continental shelf were not as cold as they have been in years of stronger upwelling. This pattern continued through summer 2011 when the deep water temperature was the third warmest of our 14‑year data set. Overall, the upwelling season of 2011 would be categorized as moderate-to-weak.
Length of the Upwelling Season
Even though the strong winter storms ended in early April, and the first puff of upwelling winds was seen on 13 April (day 105), as noted above, significant amounts of upwelling did not begin until 9 June. The season ended early, on 13 September, resulting in an upwelling season that was 161 days in length, or 20% shorter than the climatological average.
Copepod Biodiversity (Species Richness)
Species richness is the number of copepod species in plankton samples. Monthly averaged values of copepod species composition continue to track the PDO and SST quite closely. When the PDO is negative, surface waters are cold, and the copepod community is dominated by only a few cold–water, subarctic species; however, when the PDO is positive, SSTs are warm, and the community is dominated by a greater number of warm–water, subtropical copepod species. We found low values of species–richness values throughout 2011, an indication of improving ocean conditions.
Northern Copepod Anomalies
Copepods are transported to the Oregon coast, either from the north/northwest or from the west/south. Copepods that arrive from the north are cold–water species that originate from the coastal Gulf of Alaska; these are referred to as the "northern copepods." The "northern copepod index" is the log biomass anomaly of three species of cold–water copepods: Calanus marshallae, Pseudocalanus mimus, and Acartia longiremis. This index tracks closely with the PDO. This index was especially significant in summer 2011 because the log of the northern copepod biomass anomaly was the highest we have seen in recent years, indicating “good ocean conditions” in 2011.
Biological Spring Transition
The biological spring transition is defined as the date when the zooplankton community has transitioned from a warm–water "winter" community to a cold–water "summer" community. During 2011, the biological transition came early, on day 82 (21 March). This is another indicator of improving ocean conditions.
Annual abundance estimates of key salmon prey in winter and early spring provide an indicator of survival in the months before juvenile salmon enter the sea because these estimates reflect the feeding conditions they will potentially encounter. Data from January-March 2011 (winter) indicate some of the poorest feeding conditions for salmon that entered the sea in spring 2011.
Catches of Spring Chinook in June
Pelagic trawl surveys have been carried out for 14 years, since 1998. In recent June surveys (2008‑2010), catches of spring Chinook have been high, with record-high catches in 2008. However, catches in June 2011 were poor, ranking 10th among the 14 years of surveys.
Catches of Coho in September
Catches of juvenile coho salmon in our September trawl surveys have been a fairly good indicator of rates of return of coho the following year. Catches over the past few years have been among the lowest since 1998; however, numbers of coho in the September 2011 survey ranked 5th overall.
When all of the indicators are taken as a whole, the year 2011 has a rank of 8 out of 14, suggesting below‑average returns of coho in 2012 and Chinook in 2013. However, similar to the past two years, individual indicators have sent a mixed message. Certain indicators suggest the potential for above‑average returns: persistence of strong La Niña conditions, a negative PDO, positive copepod anomalies from May-September, and reasonably high catches of coho in the September survey. However, negative indicators include relatively warm surface and deep waters on the continental shelf, weak upwelling in spring, a short upwelling season, and low abundances of ichthyoplankton during January-March. Because of these mixed signals, we are less certain of our prediction for coho in 2012 and Chinook in 2013.