Extreme water mass anomaly observed in the Hawaii Ocean Time-series

Extremely anomalous water mass properties, with deviations as high as 35 si gma, were observed in the thermocline during January 2001 at the Hawaii Oce an Time-series site north of Oahu. The spatial distribution of the anomalou s waters is consistent with a submesoscale vortex with radius similar to 15 km, possibly a remnant of a mesoscale eddy. The most plausible source loca tion of the anomalous waters is offshore of Mexico near Baja California. Gi ven the southwestward subtropical gyre circulation, it is unlikely that the se waters were transported directly westward to Hawaii. Unusual northward t ransport of Equatorial Waters along the North American coast during the 199 7-98 El Ni (n) over tildeo event, and subsequent transport southwestward in the core of a California Undercurrent eddy is more plausible. El Ni (n) ov er tildeo modulation of eddy transport and diffusion of water mass properti es may substantially impact the mean distribution of properties in the Nort h Pacific subtropical gyre.