Observations from moorings in the Aleutian Passes: temperature, salinity and transport

AbstractBetween May 2001 and September 2003, a series of moorings were deployed in four of the Aleutian Passes – Tanaga Pass (12 months of data), Akutan Pass and Seguam Pass (18 months), and Amukta Pass (36 months). Instruments on each mooring measured temperature, salinity and current velocity. Tidal currents dominated the flow in each pass, including a strong fortnightly component in the three deeper passes (Tanaga, Seguam, and Amukta). Net transport in each of the passes was northward, varying from 0.1 × 106 m3 s−1 in Akutan Pass and 0.4 × 106 m3 s−1 in Seguam to >4.0 × 106 m3 s−1 in Amukta Pass. The transport in Amukta Pass, calculated from current meters, was approximately five times as large as previously estimated from hydrographic surveys. At monthly and longer periods, the variability in transport in Amukta Pass was related to the position and strength of the Alaskan Stream southeast of the pass. Vertical mixing was examined in Akutan and Seguam Passes. Strong tidal currents mix the water column top‐to‐bottom over the shallow sills in the passes, a depth of 80 m in Akutan and 140 m in Seguam Pass, providing a critical source of nutrients to the Bering Sea ecosystem.