2012: Annual summary of ocean ecosystem indicators and pre-season outlook for 2013
The Pacific Decadal Oscillation (PDO) has been negative and cold ocean conditions have prevailed for most of the period between September 2007 through 2012. This was interrupted by a brief moderate El Niño event from Aug 2009-May 2010, but otherwise the PDO has been strongly negative over a period of more than five years. If the PDO were the only indicator of "ocean conditions" for the northern California Current, this situation would be worthy of praise. However, local conditions did not mirror the PDO in 2012; the date of spring transition (from winter downwelling conditions to summer upwelling) was very late – it did not occur until 2 May, three weeks later than the long-term average. Moreover, winds were light and variable through May and June, and sea surface temperature values were several degrees warmer than ‘normal’ from mid–June through July. The significance of these observations is two–fold:
The PDO alone does not reflect local conditions because values during much of 2012 were among the most negative of any in the past 100 years, yet sea surface temperatures were elevated;
Very warm surface water in June and July was almost certainly harmful to juvenile salmon which entered the sea in May because elevated temperatures will result in increased metabolism and likely poor feeding conditions.
This suggests that the early summer period of 2012 was a time of poor ocean conditions from the viewpoint of those taxa of juvenile salmon that live locally. However, fish such as juvenile Snake River spring (stream-type; yearling) Chinook salmon that migrate out of the area quickly may have migrated northwards and left the area before poor conditions prevailed.
A final comment is that an El Niño is brewing at the equator with all equatorial indices in the “positive” range. However, at the time of this writing (mid-December 2012), “El Niño neutral” conditions exist.
Next we discuss the state of each of our ecological indicators of ocean conditions in the context of how our measurements in 2012 compared to those made by our research team since 1998. Annual values for each indicator from 1998 until present are listed in Table 3.
Pacific Decadal Oscillation—The PDO was strongly negative through 2012, reaching a value of -2.21 in September (Figure 5). The most recent value available (-0.59, for November) suggests that the negative phase is weakening.
The Oceanic Niño Index (ONI)—The ONI values have been steadily increasing since December 2011 and have been positive since June 2012; as of November 2012 the ONI index was + 0.8 suggesting “El Niño conditions”, however the NOAA Climate Prediction Center’s website, http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf, states that it is considered unlikely that a fully coupled El Niño will develop during the next several months. ENSO-neutral is now favored through the Northern Hemisphere winter 2012-13 and into spring 2013.
Sea Surface Temperature (SST)—At the NOAA Buoy 46050, 20 miles offshore of Newport, SST usually tracks the PDO closely, however this was not the case during the summer of 2012 (Figure 5). Daily values of SST (Figure 6), show positive (warm) temperature anomalies in June and July, with daily values of temperature anomalies around +3°C in mid-July. The monthly average anomaly was + 1.7°C for July, at a time when the PDO value was – 1.52. Thus, we issue a warning -- although the PDO usually tracks local conditions, this was not the case during summer 2012. SST at one of our baseline hydrographic stations (NH05, five miles offshore of Newport) was also above-average over the May-September period (Figure 7), with a peak in SST (15.9°C) observed on 25 June, a value which was the 12th warmest of 450 measurements made at this location since 1996.
Mixed Layer Temperatures (MLT). —Mixed Layer Temperatures refer to temperatures averaged over the upper 20 m of the water column, that part of the water column that is mixed by the wind in summer. When these values are calculated, we learned that despite warm sea surface temperatures in 2012 (and 2007 and 2009), when the mixed layer temperatures are compared, anomalies during the upwelling season were below average (i.e., cooler than ‘normal’) for the past seven years (Figure 7). Winter MLTs however were the same as winter SST (Figure 7), likely because the entire water column is well-mixed by intense winter storms. These observations create a problem for interpreting ocean conditions. SST values are readily available from satellite and buoy measurements, but do they adequately represent habitat conditions for juvenile salmon, or is the MLT more representative? We know for certain that they live in the upper parts of the water column in depths < 20 m, but exactly where in the upper layer, and for how long, is not known with certainty.
Coastal Upwelling.—Upwelling was initiated on 2 May and ended on 12 October. The duration was 161 days (Figure 11), ranking 11th out of 15 years. The start date was three weeks later than the long-term average; however, after only a few days, upwelling ceased and did not resume until early July, after which the upwelling index pointed towards strong and nearly continuous upwelling, with only brief pauses, until October. However as shown above, very warm surface water was found on the continental shelf on nearly all days in July (at a time when the upwelling index was suggesting strong upwelling). Thus, the UI did not index local conditions during the summer of 2012. Since the UI is a large-scale indicator (as is the PDO), we wonder what kinds of atmospheric events occurred locally and caused these two basin-scale indicators to fail to index local conditions.
Deep Water Temperature and Salinity—The year 2012 saw the continuation of a trend that began in 2009 towards slightly warmer and fresher water at depth on the continental shelf. We take this as an indication that upwelling has been weak and the source of the waters which upwell are from a shallower depth offshore. The April-June 2012 data Figure 17 were among the fresher and warmer years; July-September was cool and fresh (often referred to as ‘minty’ water). This is reflected in the sea surface temperature data as well – warmer waters prevailed through much of 2012.
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 quite closely Figure 21; the average for the upwelling season (May-September) in 2012 was ~ 9 species, the same as observed from 2007-2009 and in 2011, but higher than during the cool period of 2000-2001 when the average was about 7 species (Figure 23).
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 (Figure 24). This index was especially significant in summer 2011 and 2012 because the log of the northern copepod biomass anomaly during these two years was the highest we have seen (Table 2 and 3). Further, we experienced a relatively cool winter/spring starting in late 2011, with strongly negative PDO values, and correspondingly the biomass of northern copepods was much higher than average (Figure 24). The high biomass of northern copepods observed in 2011, and persisting into winter and through the summer 2012, is indicative of very good ocean conditions.
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 2012, the biological transition occurred on day 125 (4 May), as shown in Table 3. May 8th is the median date of transition, so 2012 was about average. However, it was ranked fourth out of the 15 years so this is an indication of fair ocean conditions. Several methods are used to calculate dates of the spring and fall transition, and a compilation of the different methods (including our “biological transition”) is available from Columbia River DART (Data Access in Real Time), a project of the University of Washington School of Aquatic and Fishery Sciences (http://www.cbr.washington.edu/data/trans.html).
Winter Ichthyoplankton—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 2012 (Table 3) were also ranked sixth out of the 15 years, indicating average feeding conditions for juvenile salmon that entered the sea in spring 2012 (Figure 34).
Catches of Spring Chinook in June—Pelagic trawl surveys have been carried out for 15 years, since 1998. In recent June surveys (2008 & 2009) catches of spring Chinook salmon have been high, with record high catches in 2008. Although, catches in June 2011 were poor, catches in June 2012 were high, ranking 2nd among the 15 years of surveys (Figure 36).
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 salmon the following year (Figure 37). ). Catches in September 2011 were high, however catches of juvenile coho salmon in the September 2012 survey were relatively low and ranked 10th out of the 15 years (Figure 36).
Positive Signals in 2012:
PDO and ONI strongly negative during winter 2012;
Ocean was colder than normal by 1°C during winter, the 2nd coldest value in 17 years.
Northern copepod biomass was the highest in 17 years and the copepod community composition index, the 4th highest.
Winter ichthyoplankton biomass had a rank of 6, slightly above average
Despite good local ocean conditions in winter, upwelling was delayed by three weeks from its normal start date to the first week of May – shown by both the upwelling index (physical transition was on 2 May) and the copepod index (biological transition was 4 May).
The cumulative upwelling index showed that even though upwelling began on 2 May, winds remained light and variable such that significant amounts of upwelling did not occur until early July. Furthermore, sea surface temperatures remained anomalously high in July, averaging about 2°C above normal. This condition may have been unfavorable for those taxa of juvenile salmon which live in the surface layers of the ocean because these temperatures would have significantly elevated their metabolism, requiring them to feed at higher rates. However, the average temperatures for the upper mixed layer were average.
On the other hand, spring Chinook salmon catches in our June surveys were the second highest in 15 years. These fish migrate northwards quickly en route to the coastal Gulf of Alaska, and by June are at the northern end of our survey area (and already off Vancouver Island) thus they may not have experienced the warm temperatures which first appeared on 15 June. Coho salmon on the other hand (which are more resident in local waters) would have experienced high SST throughout much of summer which may explain why catches in September were poor, ranking 10th of 15 years.
When all of the indicators are taken as a whole (Table 2), the year 2012 has a rank 4 out of 15, suggesting above-average returns of coho in 2013 and Chinook in 2014. (Note that we now exclude the "upwelling indicators" from the average rankings, but all values are shown in Table 3).
Similar to the past several 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 indicators from May-September, and high catches of spring Chinook salmon in the June survey. However, negative indicators include a late start to the upwelling season (first week of May), nearly a two month delay until upwelling became strong (not until early July), and very warm sea surface temperatures in June and July. The upwelling season was among the shorter ones, only 161 days (as compared to more than 200 days in 1999, 2002, and 2009). Because of these mixed signals, we are less certain of our prediction for coho salmon in 2013 and Chinook salmon in 2014, a statement that we made last year as well.
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