2013 Ocean Indicators Summary
A summary of ocean indicators of the northern California Current for 2013.
In 2013, the recent trend of mixed ocean conditions continued. The physical indicators such as PDO and El Niño were both “neutral,” sea surface temperatures were warmer than usual, and upwelling was weak (except for July). However, all biological indicators pointed to good ocean conditions – large lipid-rich zooplankton were present in high numbers, winter fish larvae that become salmon prey in spring were moderately abundant, and spring catches Chinook during the June survey off Washington and Oregon were second highest in 16 years. Given these mixed signals (and by assigning greater weight to the ‘biological indicators’), we are leaning towards good returns of coho salmon in 2014 and both types of Chinook salmon in 2015.
PDO and ONI
The PDO remained negative throughout 2013 but was transitioning to near-neutral conditions. Similarly, the ONI remained only slightly negative throughout the year, maintaining ENSO neutral conditions. The continued forecast from the NOAA Climate Prediction Center is for neutral conditions through at least mid-2014.
Upwelling Index at 45°N
This year had a very mild winter with no large southwesterly storms, and therefore almost no downwelling in January-March, as indexed by the Cumulative Upwelling Index (CUI). The day of spring transition (based on the CUI) was on 7 April, which is six days earlier than average (40-year climatology). Despite the near-average date of transition (which signifies the end of the winter downwelling season and the beginning of the upwelling season), upwelling was not particularly strong from April-June. Upwelling continued to be weak through most of May and June, including a two-week period in mid-June of southwesterly winds, which, as shown later in this report, was accompanied by a stranding of massive amounts of euphausiids on the beaches of Oregon and N. California. Much of the summer upwelling was concentrated in July. The upwelling season ended on 18 September (Day 261), nearly three weeks earlier than usual. Despite the weak start and early ending, the strong upwelling in July compensated, and overall, the total amount of upwelling was nearly the same as the 16-year average.
Sea Surface Temperatures (SST) at NOAA Buoy 46050
The first few months of the year showed negative SST anomalies ranging from -0.5 to -1°C from Jan-May, followed by a strong positive anomaly through the latter half of June resulting from a lengthy period of southwesterly winds and downwelling. Strong, upwelling favorable winds in July brought cold waters to the surface leading to strongly negative SST anomalies. An early end to upwelling in mid-September is reflected by strongly positive SST anomalies throughout September and much of October.
Temperature and Salinity
Bottom waters on the shelf at our baseline station (NH 5) during the spring (April – June) of 2013 were the second coldest temperature and highest salinity values observed since 1997. The other “cold-and-salty” years were 2002, 2007, and 2008. However, averaged conditions during the summer upwelling period (May-Sept) changed dramatically. During the upwelling period, the average temperature and salinity were warm and fresh, ranking the third and second warmest and freshest water observed during the upwelling season since 1998. The temperature and salinity characteristics of the deep water at this station are good indicators of upwelling onto the shelf. Although the total upwelling from May-Sept was nearly the same as the 16-year average, most of the upwelling occurred during July and August. Upwelling was weak through most of May and June, with two weeks in mid-June of southwesterly winds and very warm sea surface temperatures. Similarly, September was characterized by southwesterly winds during most of the month. The weak start to the upwelling season and the strong southwesterly winds in June likely contributed to the overall average of relatively warm and fresh deepwater observed during the upwelling season in 2013.
June (and early July) had the lowest oxygen concentrations that we have measured in that period since we began collecting data in 2005. Values in June were 1.28 ml L-1 (07 June) and 1.1 ml L-1 (19 June), and in early July, 0.94 ml L-1. Values < 1 ml L-1 have in the past not been seen until August or September at station five along the Newport Line.
A June survey of coastal waters off the Washington and northern Oregon coast detected hypoxic water over 41% of the shelf north of Newport, Oregon. This is the greatest extent of hypoxic waters detected in June over the last seven years. There is no direct impact of these low oxygen waters on salmon, as the hypoxia is primarily in the lower portion of the water column and the salmon (especially juveniles) tend to be in the upper portion.
The winter-time (Jan-March) abundance of larval stages of fish species common in salmon diets was above average this year (Figure WI-01), ranking fifth-highest over the 16 years of data. The abundance of all larval fish species combined ranked 7th of 16.
During winter (Nov 2012–March 2013), copepod species richness and the biomass of southern (“warm water”) copepods were moderately high, which likely corresponded to positive values of the Oceanic Niño Index during autumn 2012. In the spring (April – June) of 2013, copepod species richness and the biomass of southern copepods declined, while the biomass of northern (“cold water”) copepods increased dramatically and remained high throughout the summer upwelling period. This increase in northern copepods is an indicator of good ocean conditions and generally follows strongly negative values of the PDO. However, the PDO during this time was only moderately negative. Low copepod species richness and high biomass of northern species point to greater–than–average transport of subarctic water into the northern California Current.
Adult Salmon Returns
The spring Chinook counts at Bonneville Dam in 2013 was much lower than anticipated (based on ocean conditions in 2011 when the juveniles were entering the ocean). Only ~ 83,000 spring chinooks were counted at Bonneville from 15 march-31 May, less than half of what was predicted based on our Ocean Indicators. On the other hand, returns of fall Chinook were far higher than anticipated (based on ocean conditions in 2011) and set a record of nearly 1 million fish! We noted that in 2011, individual indicators sent a mixed message: certain indicators suggested the potential for above-average returns -- the persistence of strong La Niña conditions, a negative PDO, and positive northern copepod anomalies from May-September; however, negative indicators included relatively warm surface 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 were less certain of our outlook for returns of spring and fall Chinook salmon in 2013.
How could we have overestimated spring Chinook by half and underestimated fall Chinook by two-fold? The year 2013 returns mark the first time that our outlooks on Chinook salmon returns have missed significantly since our first attempts in 2006. This “miss” lends the opportunity to re-examine our set of ecological indicators to determine if we are missing a key variable or if other variables were expressed for the first time in 2011. One hypothesis which we will explore is that some aspect of ocean conditions elsewhere was the cause of poor returns of spring Chinook salmon in 2013. Since spring Chinook migrate north into the Gulf of Alaska within 4-6 weeks after exiting the Columbia River, we will see new indicators of ocean conditions for waters off northern British Columbia and Alaska to determine if perhaps spring Chinook encountered poor ocean conditions in those waters. As for fall Chinook salmon, we have no immediate explanation for their record returns from an ocean perspective other than to note that perhaps these fish responded positively to the La Niña conditions, negative PDO and positive northern copepod biomass anomalies and that they are not bothered by weak upwelling and warm SST.