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

✔

✔

✔

✔✔

✔

✔

✗

✗

✗

✗✗

✗✗

✗

✗✗

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✗

✔

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