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Lukas, R. ., University of Hawaii, Honolulu, USA, rlukas@hawaii.edu
Santiago-Mandujano, F. ., University of Hawaii, Honolulu, USA, mandujan@soest.hawaii.edu
Nosse, C. ., University of Hawaii, Honolulu, USA, nosse@soest.hawaii.edu
Firing, E. ., University of Hawaii, Honolulu, USA, efiring@hawaii.edu
Luther, D. ., University of Hawaii, Honolulu, USA, dluther@hawaii.edu
Alford, M. ., U. Washington Applied Physics Laboratory, Seattle, USA, malford@apl.washington.edu
Howe, B. ., University of Hawaii, Honolulu, USA, bhowe@hawaii.edu
Duennebier, F. ., University of Hawaii, Honolulu, USA, fred@soest.hawaii.edu

SURPRISING ABYSSAL TIDAL SIGNALS AT STATION ALOHA

The real-time ALOHA Cabled Observatory (ACO) has operated at Station ALOHA at 4728 m since June 2011. The ACO pressure sensor shows a dominant M2 tidal signal with a range of ~0.7 dbar. The difference from the TPXO7.2 barotropic tide model has a comparable range and frequency, but it is sharply peaked near high tide, which cannot be simply due to model M2 amplitude and phase errors. The ACO acoustic Doppler profiler 2.5 m above the bottom (mab) consistently measures the flow from 20 to 70 mab, revealing tidal flows with a range of 0.2 m/s while TPXO7.2 predicts a barotropic tidal range of ~0.04 m/s. Currents are weaker below 30 mab, as expected for a boundary layer. However, the structure above that is not simply barotropic, consistent with earlier moored measurements at the site. Occasional short duration accelerations occur with downwelling and upward phase lag. These episodes are sometimes seen in temperatures and salinity 2 mab, with unexpectedly large temperature range of 0.01K and salinity range of 0.005. These may be turbulent bursts in the benthic boundary layer.

http://aloha.manoa.hawaii.edu

Session #:021
Date: 2/20/2012
Time: 12:15
Location: Ballroom G

Presentation is given by student: No