ALOHA Cabled Observatory: Continuing results and lessons

1. ALOHA Cabled Observatory: Continuing results and lessons Bruce M. Howe, Roger Lukas and many more! School of Ocean and Earth Science and Technology University of Hawai’i at Manoa American Geophysical Union, OS51F-06 San Francisco, California 7 December 2012

2. Station ALOHA ACO R. Lukas, D. Karl and many others ALOHA Cabled Observatory (ACO) F. Duennebier et al.

3. ACO Mosaic

4. ACO bottom configuration – June 2011 ✔ ✗ ✔ ✗ ✔ ✗ ✗ ✔ ✗ ✔ ✗ ✔ ✗ ✔ ✗ ✗ ✗

5. Data and results Aloha.manoa.hawaii.edu

6. Video samples Deep-sea lizard fish attempting to eat an aristeid shrimp

7. 450 observations of animals per monthshrimp and other inverts make up 93% of observationstemporal patterns in abundance under investigation • Jeff Drazen, AharonFleury, UH 15 species + unknown Aristeid Shrimp Polychaete worms Benthic shrimp

8. Heavy rain Tuesday night • 20121205T0956 First blues31 October 2012 ALOHA Synergies Ground truth: WHOTS Met/upper ocean buoy R/V Kilo Moana on site Oahu-based Doppler radar x10

9. Marine mammal papers • Oswald et al., JASA, 2011 – minke boings • Ou et al., JASA-EL, 2012 – time domain baleen whale detector

10. Acoustic Doppler profilers N ✗ 250 kHz ADP 250 kHz L-ADCP ✔

11. January 2012 Currents @ ALOHA good signals between ~23 m - 80 m above bottom 8 m bins 4 min avgs, after screening 2 s samples diurnal and semidiurnal tides u m/s bottom depth = 4728 m Abyssal ocean v m/s

12. Observed Currents and Detiding currents averaged over 31-71 m above bottom 120 days 24 days internal wave packets ~3 day LP/HP (Blackman 72 hour half-width

13. Rotary Spectra, De-tided ACO K1 internal tides more energetic than expected nonlinear tides M2+K1 CCW diurnal barely above background

14. 36-hour low pass flow 1.5 year • mean current ±6 cm/s, rapid changes • Still QC • Upward +W bias – instrumental, or ACO flow distortion? • Correlated with “horizontal” flow – ACO tilted (~5°, negligible in horizontal flow, correctable in vertical component) V 3 mm/s W

15. ADP – Instrument and Science Summary • SonTek 250 kHz, 6 mm scattering length-scale (turbulence+?) • Coherent signals at significant range (80 m) • Old 4-element unit works well, new 3-element unit has noisy beam • Must poll for data (clocks, interference, use SIAM) • Strong tidal flows, more energetic than TPXO7.2 barotropic tides • Significant internal tide energy in near-bottom currents, with diurnal and nonlinear harmonics • Cold, bottom-intensified events are a major source of non-stationary stratification – is this an important source of abyssal internal tide modulation? Acknowledgements: Martin Guiles for SuperTide analysis

16. CT on OBS – above power supply Primary CTDS Ground fault SBE-37, un-pumped (secondary) N Example T-spike 25 m°C power supply 24 h, 2 s sampling

17. In situ temperature record 0.01°C raw temperature (red) with spikes and de-spiked (blue) 0.001°C

18. De-spiked daily averaged temperature at 4726 m cold overflow event large oscillations slow recovery 1.5 years now real features – not observatory artifacts or aliases 20 m°C 4 m°C Red - HOT CTD averaged over deepest 10 m, 16-24 m above bottom 3 months

19. Temperature Summary • Heisenberg bites! ACO heat dissipation causes thermal plumes • De-spiked daily averaged SBE-37 temperature agrees with shipboard CTD SBE 9/11+ profile data to within 1 m°C • Major cold overflow event captured, no aliasing • Sloshing mode hypothesized by Lukas et al. (2001, DSR) supported • Cf Alford et al., 2011

20. Problems and Failures • Ground faults – acoustic modem, AMM secondary node with primary CTDO2 and FLNTU • Lights?? – bad heat sink, bad control circuit • Thermistor array; connector to ACO broke on deployment; internally recording; being recovered now • SBE-37 conductivity/salinity? • Pressure sensor - ? (initially odd, now drift/jumps) • Shore-side • Hardware (UPS failed Christmas Eve, …), • Backhaul 3 Mb/s – large constraint (expect +ve change) • Software – data transfers • Underfunded

21. Lessons • Even more testing • Cables and connectors • Sensor/system interactions, electrical noise/interference, heat sinking • Precise time sampling, control • Improve deployment/ops, spread out seafloor equipment • Don’t underestimate shore-side needs • Network management – intensive! • Data management – intensive! • Documentation – intensive! • Real-time – intensive! • Understanding problems with data – intensive! • Observatories prove value with un-aliased data

22. Expanding science at ALOHA • Water column • Dynamics, mixing, turbulence, episodic events • Biogeochemistry – nutrients, production, fluxes • Benthic communities – vertical fluxes, top predators • Surface wave phenomena (e.g., ultra-gravities) • Marine mammal studies – ships, behavior, population • Basin scale communications and thermometry • Synergies with historical/on-going ALOHA/HOT program

23. Present and future • Getting science results • Faults/failures, lessons • NSF OTIC O&M project • 2012-2015 • Includes 5 days ship/rov time • Barebones • September 2013 cruise • repair/replace non-working core sensors • Proposals to use – Submit to NSF, others