Between July 1997 and March 1999, we have made 10 cruises with CTD/ADCP sections off Newport, Oregon (44.6°N), most extending from the coast to 150 km offshore. A historical (1961-71) hydrographic data base exists for this section.

The surface layer off Oregon was warmer than normal when we began the LTOP in July 1997; the largest anomalies (>6C) were offshore (>90 km), which would be unusual for El Nino. In September 1997, the largest anomalies were inshore (<50 km) and the surface layer was everywhere warm (>17°C) with low salinity; subsurface slope waters were >1C above normal with isotherm slope indicating northward advection and clearly indicating the arrival of El Nino. In November 1997, subsurface waters over the slope were even warmer than in September and steric height rose steeply toward shore over 60 km, consistent with strong northward flow on the shelf. In February 1998, all water on the shelf was >12°C (>2°C above normal). Temperatures over the shelf were above normal to June 1998 but were near normal by August 1998. Temperature and salinity fields suggest that upwelling was suppressed from September 1997 to June 1998. (The PFEL Upwelling Index, based on wind stress, for 45°N was negative or anomalously weak from June 1997 to June 1998.) Subsurface waters over the upper slope (100-400 m) remained warmer than normal from July 1997 through September 1998. The winter and spring sections showed enhanced poleward advection, with a local anomaly maximum near the shelf-break. The geostrophic currents were consistent with ADCP data in showing a strong current jet flowing poleward beyond the shelf break off Newport during the El Nino winter (November 1997 and February 1998). This poleward jet was surface-intensified with speed ~ 0.5 m/s, width ~ 20 km, and extending to depths > 200m. In August and September 1998 the equatorward surface jet associated with normal coastal upwelling was present over the shelf, shelf temperatures were only slightly above normal, and the PFEL Upwelling Index was stronger than average for August and September 1998. The temperature sections in November 1998 and February 1999 were nearly normal and suggest the physical oceanographic traces of El Nino have gone.

Sections were also made at several latitudes between Newport, Oregon and San Francisco, California in November 1997, April, August and November 1998. These extended cruises showed much alongshore homogeneity in winter, especially during El Nino. In November 1997, sections at 39°, 42°, 43.2°, and 44.7°N all show the steric height of the sea surface rising steeply toward shore (~20 cm in ~ 60 km), while the 7° and 8°C isotherms slant down toward the continental slope, indicating enhanced poleward flow over the shelf and upper slope. In April 1998, steric height profiles were flat (at 39° and 44.7°N) or slanting down toward the coast (at 42° and 43.2°N), indicating that the anomalous poleward flow had weakened or ceased. In August 1998, these sections showed evidence of near-normal coastal upwelling inshore although subsurface waters offshore remained warmer than normal; they also show the 6.5° and 9°C isotherms diverging toward shore, suggesting geostrophic poleward flow with a subsurface core offshore of the continental slope. At this time, the ADCP observations along each section showed a band of poleward flow 20-40 km wide, with a subsurface maximum centered at 150-200m, typical of the scales of the poleward undercurrent but with the core of the flow detached from the continental slope and offshore of the shelf break by 15 to 40 km.

Satellite-tracked drifters (drogue at 15 m) were released off Newport along 44.6°N during the January through September 1998 cruises. Eight drifters released off Newport in January 1998 initially moved coherently to the north, with strongest poleward flow (0.65 m/s) near the continental shelf break. Five eventually beached between 47° and 56°N, two not until September 1998 and January 1999; the other three, which were between 49.5°N and 48°N about 1 March 1998, turned southward in spring and were south of 35°N in March 1999. These drifter observations are consistent with the enhanced poleward advection noted in ADCP measurements and geostrophic estimates during winter 1998. Of the seven drifters released off Newport in April 1998, the five released over the shelf and slope were advected by variable wind-driven currents, including some initial northward motion. Through August and September most drifters were moving equatorward and offshore, delineating the meandering jets of the California Current; by October some drifters from the January, April, June and August releases were between 35° and 39°N. The drifters released in late September initially moved offshore and southward but, with the onset of fall storms, moved back toward the coast and all eventually beached. The most recent drifters to beach were those deployed 65 and 45 n. miles off Newport in September 1998; they came onto the continental shelf within a few days and a few 10s of km of each other and the New Carissa (which beached in February 1999 near 43.5°N) and moved northward over the mid- and inner-shelf for more than 100 km before beaching near 44.5° and 46.5°N.

For a more complete discussion and figures, see our web-site (Monitoring the Coastal Ocean off Oregon: El Nino and beyond) under: http://www.coas.oregonstate.edu/po/coastal.html

The GLOBEC processed CTD files are on our public ftp site. The ftp site address is ftp.coas.oregonstate.edu (login as anonymous, with your email address as your password), then cd to /dist/globec/ - the files are under their respective cruise names. The contact is Jane Fleischbein (flei@coas.oregonstate.edu).