Subtidal velocity correlation scales on the northern California shelf

Abstract

Along- And cross-shelf correlation scales of subtidal cross-shelf (u) and along- shelf (v) velocities are estimated using moored records from several field programs over the northern California shelf. Over record lengths of 4-6 months, along-shelf correlation scales of v are greater than maximum mooring separations (60 km). In the cross-shelf direction, v is generally correlated between the 60 and 130 m isobaths (10-15 km separation). Along-shelf correlation scales of u are much smaller than those of v and are often not resolved by minimum mooring separations. Time series between November 1988 and May 1989 do resolve along-shelf correlation scales of near-surface u and indicate that they are 15-20 km. During this time the along-shelf correlation scale of near-surface u shows variability on a monthly scale. It is generally long (30 km or more) when correlation of u with wind stress is high and short (15 km or less) when correlation with wind stress is low. On at least one occasion, short along-shelf correlation scales coincide with the intrusion of an offshore mesoscale feature onto the shelf. Cross-shelf correlation scales of u are resolved for typical mooring separations. In general, u is correlated between the 90 and 130 m isobaths (7-13 km separation) and between the 60 and 90 m isobaths (~5 km).