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Bruce M. Howe, Roger Lukasand many more!
School of Ocean and Earth Science and TechnologyUniversity of Hawai’i at Manoa
American Geophysical Union, OS51F-06San Francisco, California
7 December 2012
ALOHA Cabled Observatory: Continuing results and lessons
R. Lukas, D. Karl and many others
ALOHA Cabled Observatory (ACO)
Station ALOHA
ACO
F. Duennebier et al.
ACO Mosaic
ACO bottom configuration – June 2011
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Data and results
Aloha.manoa.hawaii.edu
Video samplesDeep-sea lizard fish
attempting to eat an aristeid shrimp
AristeidBenthic ShrimpPolychaeteCoryphaenoidesOphidiidaeSmall Fish (Ophidiid/Barathrites?)ScopeloberyxPaleopatides?Squid/Cephalopod?EnypniastesUnknown JellyBathysaurus mollisIsopod?Unknown SpeciesNudibranch
Polychaete wormsAristeid Shrimp
Benthic shrimp
450 observations of animals per monthshrimp and other inverts make up 93% of observations
temporal patterns in abundance under investigation
15 species + unknown
Jeff Drazen, Aharon Fleury, UH
First blues 31 October 2012
x10
Heavy rain Tuesday night
20121205T0956
ALOHA SynergiesGround truth:WHOTS Met/upper ocean buoyR/V Kilo Moana on siteOahu-based Doppler radar
Marine mammal papers
• Oswald et al., JASA, 2011 – minke boings
• Ou et al., JASA-EL, 2012 – time domain baleen whale detector
N
250 kHz
L-ADCP
Acoustic Doppler profilers
250 kHz ADP✗
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January 2012 Currents @ ALOHA
u
v
bottom depth = 4728 m Abyssal ocean
good signals between ~23 m - 80 m above bottom
8 m bins
4 min avgs, after screening 2 s samples
diurnal and semidiurnal tides
m/s
m/s
Observed Currents and Detiding
~3 day LP/HP (Blackman 72 hour half-width
currents averaged over 31-71 m above bottom
internal wave packets
120 days 24 days
Rotary Spectra, De-tided ACO
M2+K1
nonlinear tides
CCW diurnal barely above background
K1 internal tides more energetic than expected
36-hour low pass flow
3 mm/s
1.5 yearV
W
• 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)
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
NSBE-37, un-pumped (secondary)
CT on OBS – above power supply
power supply
Primary CTDSGround fault
Example T-spike25 m°C
24 h, 2 s sampling
In situ temperature record
raw temperature (red) with spikes and de-spiked (blue)
0.01°C
0.001°C
De-spiked daily averaged temperature at 4726 m
Red - HOT CTD averaged over deepest 10 m, 16-24 m above bottom
cold overflow eventlarge oscillations slow recovery
1.5 years now
4 m°C
20 m°C
real features – not observatory artifacts or aliases
3 months
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
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
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
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
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