Enhanced southward flow over the Oregon shelf in 2002: A conduit for subarctic water

Abstract

Moored current measurements from the Oregon shelf during 1998-2003 are used to estimate time series of anomalous alongshore currents and pseudo-displacements, after accounting for the mean and seasonal cycle. From early January through mid-June, 2002, currents at 10 m were anomalously strong toward the south by an average 12 cm/s, producing an anomalous displacement of more than 1500 km over about 5 months. This may be compared with the finding by Freeland et al. [2003] that waters at the same latitude off Oregon, and off Vancouver Island, were anomalously cool and fresh at depths between 30 and 150 m, suggesting displacement from a more northern source. Anomalous displacements of several hundred kilometers were also found during at least three other periods in the record. Moored temperature measurements at the same location confirm that local waters were persistently cooler during March to October of 2002 than during the previous two years, with the strongest anomaly near 20 m. Coastal sea levels were lower than usual along the northwest coast during spring and early summer 2002, consistent with a southward current anomaly of large scale. Local winds near Newport did not show strong mean anomalies during this period.