Kein Folientitel

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New technologies Developments during WOCE and
what the future might hold
WOCE Final Conference San Antonio, 18 Nov 2002
Uwe Send IfM Kiel
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In 1983 the community set out to tackle a
challenging task To provide a snapshot of the
global T/S and absolute flow structure of the
global ocean and to determine the components of
variability
The purpose was to collect data for testing
models useful for climate prediction and for
providing a baseline for future observations.
This needs global coverage since no ocean region
is expected to have zero long-term influence in
system or models.

• This global vision and approach
• was a drastic departure from focus on regional
  scale at the time
• had only become realistic (and probably
  inspired) by recent advances in technology
  at the time, notably in satellite altimetry
  and model/computer development.
• was destined to change our view of the ocean and
  our way of doing ocean research

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At the beginning of WOCE a wide range of
techniques already was available. The WOCE
design WGs were faced with the challenge to
determine the right mix and scale of observing
methods.

• Needed to
• pay attention to their abilities and
  limitations
• exploit complementarities
• study the feasibility of the task
• recommend/foresee improvements to existing
  techniques
• take into account developing technologies

Many existing techniques were ultimately used in
WOCE. All of them experienced large improvements
or further developments
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Hydrography, higher accuracy, global standards
transient tracers better techniques, smaller
sample volumes
current meter moorings more reliable, addition
of ADCPs
Molinari et al 98
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XBTs from VOS routine operations, expanded
networks
surface met moorings flux reference measurements
possible
Surface drifters cheaper, smaller, longer life
NTAS buoy (A.Plueddeman)
(P.Niiler)
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Shipboard ADCP leap forward due to improved
navigation
Subsurface Rafos floats commercialized, large-sca
le applications
(Bower et al 2002)
Satellite scatterometry winds now available
globally
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The only technique expected to provide true
global coverage and reveal time variability of a
range of ocean phenomena was altimetry.

• Rationale
• cm-accuracy sea-surface height
• geostrophic surface flow relative to geoid
• heat storage from large-scale steric effect
• variability from 20-10000km, 20days-10years

After the success of SEASAT, the new planned
altimetry missions were adusted to best
complement the in-situ experiment. Topex/Poseidon
(T/P) was essentially designed for WOCE.

• Challenges and limitations
• geoid insufficient at lt3000km
• aliasing of tides at 62, 173,... days
• aliasing of high-frequ. wind-forced variability
• extrapolation to ocean interior
• no coverage in polar (and ice-covered) regions
• land motion of tide gauges for SL rise

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Altimetry in WOCE was hugely successful in terms
of results and insights. It changed our view of
the ocean, and stimulated/enabled many new
activities.
Demonstrated the extremely active
time-dependence of the circulation (barotropic,
baroclinic current systems, eddy motions, etc)
(C. Wunsch)
Quantified SSH and slope variance on all
space/time scales globally
(D.Stammer)
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Eddy contribution to meridional heat flux

• Other results/achievements
• open-ocean tides measured globally to 2-3cm
• surface heat-flux estimates on basin-scales from
  storage
• observation of interannual variability (ENSO,
  circumpolar wave, etc)
• kinetic energy of geostrophic currents in
  agreement with moorings
• eddy energy helped to demonstrate that models
  need 0.1 resolution
• agreement of T/P currents and ADCP data to
  3-5cm/s
• global test of Rossby wave speeds
• global SL rise (calibrated with tide gauges)
  accurate to 0.5mm/yr
• transports of baroclinic current systems
  (variability)
• drove advances in earths gravity field
• drove most of the work in assimilation
• many more.....

(D. Stammer)
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New development for WOCE autonomous deep floats
WOCE need global field of the true (absolute)
interior flow field
The only method
available was acoustically
tracked
floats (RAFOS), which require a

network of sound source moorings.
New approach cycling autonomous floats located
by satellites (ALACE)
(R.Davis)
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Deep floats
The low cost of RAFOS and ALACE floats made it
possible to directly measure the basin-scale
deep flow during WOCE

• provide (Eulerian) mean deep flow field at all
  locations
• quantify eddy variability
• provide reference level velocity for geostrophic
  flow
• visualize transport patterns

The objective of mean flow required minimization
of eddy noise ? deep level. Need 5year record in
each 500km2 box ? 5000 float years in ice-free
ocean.
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Deep floats
In many regions, a statistically reliable
description of deep flow can now be constructed
(R.Davis)
Additional capability for T/S profiling added ?
1000s of CTD profiles from regions not visited
by ships (and during severe conditions)
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Interesting discrepancy Floats mostly remain in
N.Atlantic subpolar gyre, but tracers
clearly show export in boundary
current. Consequence of non-lagrangian property
of ALACE-type floats ?
Profiling floats are NOT lagrangian, they provide
only pieces of average velocity RAFOS floats
more closely lagrangian.
(Zenk/Koltermann)
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Deep floats

• Issues
• restricted to ice-free regions during WOCE
  and at present
• sampling biases (diffusion bias, Stokes drift)
• difficult to separate time and space variability
• unique lagrangian nature of (RAFOS) data not
  exploited yet
• desire to minimize surface interval

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Tracer release techniques
An important element of WOCE was the control
volume concept, a successful implementation took
place in the Brazil Basin. Objective a detailed
study of the deep flow and mixing processes
A new technique for directly observing interior
mixing processes were deliberate tracer releases
(SF6)
(J. Ledwell)
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Tracer release techniques
Very large diapycnal diffusivities observed in
deep Brazil Basin near MAR topography -
sufficient to close budgets and consistent
with accompanying turbulence measurements
(Polzin et al 97)
(Ledwell et al 00)
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Technological issues WOCE did not manage to solve

• CTD and water samples Very time-consuming
  and inefficient to lower CTD/rosette on wire from
  expensive research vessels. Some efforts to
  speed this up did not lead to break-throughs
  (new sampler, fast fish)

• Stability of conductivity sensors Often,
  water samples are only required to calibrate
  conductivity.

• Observations in ice-covered regions

• Mooring technology Did not change much
  during WOCE. Endurance of hardware and sensors
  limited to 1-2 years. No telemetry capability
  from deep sensors.

• Satellite surface flux measurements All 4
  heat flux components are difficult to measure,
  total flux cannot meet research (or
  operational) requirements at present.

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Lessons and Achievements of WOCE observing
techniques

• First 3-D view of the global ocean structure
• Demonstration that the long-term global
  observations required for climate studies are
  feasible
• Requires ongoing technological developments and
  integration of a variety of techniques
• The implementation needs the determination and
  commitment of the global community
• An efficient infrastructure is required for data
  management and dissemination
• Joining forces with the biogeochemical community
  has a high pay-off for both (e.g. JGOFS
  sampling from WOCE cruises)

Through WOCE, the observation of the global
ocean came of age, and wenow have the tools and
understanding to address observe global issues.
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Developments for the near future
Satellite gravity missions GRACE and GOCE will
deliver geoid with 1cm accuracy above 100km
scale. Also mass field (bottom pressure) of ocean
above these scales. Helps to distinguish SL
changes due to steric and mass anomalies.
Sea surface salinity from space SMOS satellite
mission scheduled for 2006.
Wide-swath Ocean Altimeter replace altimeter
data along line with a200km wide swath ?
complete ground coverage every 5 days
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Developments for the near future
SEAGLIDER (C.Eriksen)

• Autonomous gliders (battery power)
• use buoyancy change like floats to glide at
  inclined paths of 20
• horiz. speed up to 25cm/s
• can do sections or profiles in fixed location
  (virtual moorings)
• operating ranges of up to 7000km
• deployment from shore
• multidisciplinary sensors feasible

• Autonomous gliders (thermal power)
• energy for pumping from ocean thermal
  contrast
• projected range of up to 30,000km

SPRAY (R.Davis)

• Two-way high-rate satellite communication
• enables control of gliders (and floats)
• minimizes surface time energy consumption
• adaptive sampling

• Acoustic UW telemetry
• low-power high-rate allows long-term
  bottom deployments

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(N. Hogg)
Developments for the near future
Ice-sensing floats Detect ice and store
data/navigate acoustically

• Sensor stability
• Salinity from floats and for long-term
  moorings feasible now, better than 0.01psu.
• Bottom pressure better than 1cm, telemetry
  eliminates drift.

• Moorings
• profiling vehicles
• 5-year development (Ultramoor)
• telemetry underwater (acoustic/inductive) and
  above (satellite, capsules)
• increasing of interdisciplinary sensors

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Developments for the near future
Interdisciplinary sensors For autonomous moored
applications, sensors for many variables are
available now
CO2 sensor (M. DeGrandpre)
14C Primary Production Measurements(C. Taylor)
Optical (Dickey) and O2 sensors (Wanninkhof)

• New sound sources
• Prototype new design that can
• serve both tomography and
• Rafos signals
• high power
• high bandwidth
• high efficiency
• simple and affordable

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Developments for the near future
Data management systems and structures WOCE has
demonstrated the importance and feasibility of
data assembly, quality control, data archiving
and user-friendly dissemination structures.
Argo is implementing this with modern techniques
(S.Pouliquen)
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Where should we go

• Ultimate goal
• Develop techniques for implementing an ocean
  observing system that is
• global
• multidisciplinary
• truly integrated
• resolves all space and time-variability of
  interest (build in flexibility)
• user-friendly
• cost-effective
• providing data publicly and in real-time
• can evolve with technological advances and new
  demands danger to freeze functioning
  operational systems

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Where should we go
Minituarize sensors

• Biogeochemical sensors that are small,
  low-power, dry (optical, acoustic, chips)

MEMS chip
Optical O2 sensor

• meteorological sensors that can be submerged

• acoustic receivers/amplifiers/clocks for
  tomography and rafos signals

Micro-humidity sensor (JPL)
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Where should we go
3rd generation autonomous vehicles (symbiosis of
glider, float, AUV)

• ability to travel long distances to mission
  area and back to shore base (propelled or
  glider mode)

• choice of going into float mode, glider mode
  (sections) or mooring mode

• long endurance (thermal or solar power)

• option to receive sound signals for tracking
  (Rafos), e.g. under ice, and tomography

• flexible choice of sensors

• ability to collect ml water samples and bring
  home for analysis

Autonomous surface craft should also receive
more attention
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Where should we go
Multidisciplinary moorings for -
high-frequency observations - strong current
regimes - process studies - heavy/large
sensors - reference sites - sound sources

• long-life, advanced telemetry, expendable?

• docking of gliders for calibration and to
  return samples

• self-calibrating sensors

• deployable from VOS ?

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Integration
Expand the satellite network
Complete and maintain the ARGO network gradually
enhance/replace with 3rd generation vehicles
Implement the pilot timeseries network
and sustain it
gradually add sound sources to provide
distributed signals
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Integration

• develop data merging, assimilation, forecasting
  techniques for the integrated system
• recognize and exploit common users and needs
  of research and operational networks
• ensure multi-use of sensors and platforms
• implement data assembly, quality control,
  dissemination infrastructure
• establish international coordination/managemen
  t structure

The WOCE vision led to a demonstration of global
ocean observations. We now need the determination
and commitment to take the steps beyond.