Annual summaries of ocean indicators of the northern California Current from 2008 to present.
The Pacific Decadal Oscillation (PDO) has been negative, and cold ocean conditions have prevailed for most months from September 2007 through all of 2012. This run of negative values was interrupted by a brief and moderate El Niño event from Aug 2009-May 2010, but otherwise, the PDO has been strongly negative over 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 off Newport OR did not mirror the PDO in 2012; the spring transition was very late – 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 that the PDO alone does not necessarily 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.
The PDO was strongly negative through 2012, reaching a maximum value of -2.21 in September. The most recent value available (-0.59, for November 2012) suggests that the negative phase is weakening. Summer values (cumulated over May-September), -6.43), were the 4th most negative since 1960 (-7.63 in 2008, -6.43 in 2011, and -6.36 in 1962).
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 + 0.83, but the index fell to a slightly negative value in December of -0.09, suggesting “El Niño conditions” are waning.
At the NOAA Buoy 46050, 20 miles offshore of Newport, daily values of SST 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 + 2°C for July, at a time when the PDO value was – 1.52. SST at one of our baseline hydrographic stations (NH05, five miles offshore of Newport) was also above-averaged over the May-September period, with a peak in SST of 15.9°C observed on 25 June. This value was the 12th warmest of 450 measurements made at this location since 1996.
Mixed Layer Temperatures (MLT) refer to temperatures averaged over the upper 20 m of the water column, which is part of the water column mixed by the wind in summer. When these values were calculated for station NH05, we found that despite warm SST in 2012 (and 2007 and 2009), anomalies of MLT during the upwelling season were below average (i.e., cooler than ‘normal’) for the past seven years. Winter MLTs, however, were the same as winter SST, likely because the entire water column is well-mixed by intense winter storms. These observations create a problem for interpreting ocean conditions with respect to juvenile salmon – do they respond to SST or to MLT? 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 is not known with certainty.
Upwelling was initiated on 2 May and ended on 12 October. The duration was 161 days, ranking 11th in 15 years. The start date was three weeks later than the long-term average; however, after only a few days of northerly winds, upwelling ceased and did not resume until early July. The upwelling index pointed towards strong and nearly continuous upwelling, with only brief pauses, until October. However, as shown above, very warm 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 that caused these two basin-scale indicators to fail to index local conditions.
The year 2012 saw the continuation of the 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 that the source of the waters which upwell are from a shallower depth offshore. The April-June 2012 data were among the fresher and warmer years; July-September was cool and fresh (often referred to as ‘minty’ water) as was the season as a whole (May-September). This is also reflected in the sea surface temperature data shown above – slightly warmer waters prevailed through much of 2012.
Copepod species richness continued to track the PDO closely; 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 seven species.
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 and are referred to as the “northern copepods''; those that originate from the south and offshore are called “southern copepods.” High biomass of northern species indicates a lipid- and bioenergetically-rich food chain. Positive anomalies of one or the other indicate the transport of water from the north (for ‘northern’ copepods) or from the south (for ‘southern’ copepods) to the Oregon coast. During the winters of 2011 and 2012 (Jan-Mar), the biomass of northern copepods was the highest of our 17-year time series. Similarly, during the upwelling seasons (May-September,) of the past two years, the northern copepod biomass was also the highest in 17 years suggesting strong transport from the north.
Trawl surveys have been carried out for 15 years, since 1998, using a Nordic 264 rope trawl fished in the upper 20 m of the water column. Catches of spring Chinook salmon in June 2012 were very high, ranking 2nd among all surveys; catches of Coho Salmon in September of 2012 were low, ranking 10th of 15 years.
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
