The Future of Climate Observations

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The Future of Climate Observations in the
Global Ocean Dean Roemmich - with John Gould, Jim
McWilliams, Neville Smith, Detlef Stammer, and
Doug Wallace WOCE and Beyond Conference, San
Antonio, November 22
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The Future of Climate Observations in the
Global Ocean Dean Roemmich - with John Gould, Jim
McWilliams, Neville Smith, Detlef Stammer, and
Doug Wallace WOCE and Beyond Conference, San
Antonio, November 22

• In WOCE we learned that our understanding of the
  oceans role in the climate system is
  fundamentally data limited.
• What follows WOCE should be a serious effort to
  address that problem.

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The Future of Climate Observations in the Global
Ocean

• Outline
• Climate-related objectives of large-scale
  observations.
• The legacies of WOCE and TOGA.
• The present status of implementation and
  planning.
• The (other) major challenges
• - Observing the boundary currents.
• - Biogeochemical measurements.
• - The convergence of observations and models.
• - The research/operations partnership.
• - Data and information management.

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Ocean Observations for Climate Understanding
and prediction of climate and its variability.

• Heat and hydrological cycles The fundamental
  elements of the air/sea/ land climate system are
  heat and water.
• The ocean reservoir Heat content changes
  (seasonal, interannual, decadal) are dominated by
  the ocean - including over 90 of the observed
  global heat increase in the last 40 years. More
  than 96 of water is in the oceans. Ocean
  evaporation is the source of 1.3 x 106 m3/s of
  rainfall over land. The ocean is also an
  important sink for carbon.

• Ocean circulation
  The ocean
  transports massive quantities of heat and water
  on time-scales from interannual to the long-term
  mean. Export of heat from the tropics by ocean
  circulation is comparable to the atmosphere.

Automatic XBT launcher in Drake Passage
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Climate-related objectives of sustained global
ocean observations

• Provide a basic description of the physical state
  of the global ocean, including its variability on
  seasonal and longer time-scales.
• Reveal processes that influence climate on long
  time-scales.

• Provide the large-scale context for regional
  process studies of limited duration.
• Provide the required datasets for data
  assimilation and (seasonal and longer) forecast
  model initialization.
• Complement the satellite remote sensing systems
  with data needed for validation, calibration and
  interpretation.

A Canadian Argo float deployment
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TOGA and WOCE legacies in sustained observations

• TOGA
• - pioneered the concept of an integrated
  observing system on a basin scale.
• - installed long-term tropical observing
  networks TAO/TRITON, broad-scale XBT, surface
  drifter, sea level.
• - provided near real-time public datasets.
• WOCE
• - extended the domain of XBT, surface drifter,
  sea level.
• - produced a baseline global hydrographic
  survey.
• - installed additional long-term observations
  High Resolution XBT/XCTD network, time-series
  stations.
• - devised critical new instrumentation (e.g.
  profiling float, IMET systems) for sustained
  global observations.
• - integrated satellite and in situ
  observations with models on a global scale.

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The ENSO Observing System includes Moored buoys,
Tide gages, Drifting buoys, VOS network
To measure Sea level, thermal profiles, surface
velocity, surface fluxes (air-sea coupling).
For better understanding and improved
prediction of ENSO phenomona.
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The TAO/TRITON tropical moored buoy array is the
backbone of the ENSO Observing System -
collecting temperature profiles and surface
meteorological data near the equator.
(http//www.pmel.noaa.gov/tao)
Near real-time data delivery The warm SST patch
and westerly wind anomaly show developing El Nino
conditions.
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The Sea Level Network provides data with high
regional value and for calibration of satellite
altimeters to provide global sea surface height.
http//uhslc.soest.hawaii.edu/
High central Pacific equatorial sea level shows
developing El Nino conditions.
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Global Surface Drifter Program
Drifter deployments in 2002. The global drifter
array will increase from about 800 today to 1100
in the next 3 years.

• Surface drifter observations provide a global
  database for
• describing the mean and variability of the
  near-surface circulation.
• testing models of the surface layer.
• calibration of satellite sea surface
  temperatures.

Drifter data http//www.aoml.noaa.gov/phod/dac/d
ac.html
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Mean surface layer velocity. Square root
of the eddy energy.
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The Broad-Scale Thermal Network
Shipping routes
Broad-scale temperature profiles focus on upper
ocean heat content and thermal variability on
seasonal and longer time-scales.
Temperature profiles in January 1995
(Left) A typical months thermal profiles, XBT
plus TAO. Broad-scale XBT sampling is decreasing
as Argo increases. http//www.nodc.noaa.gov/ GTSPP
/gtspp-home.html
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TOGA and WOCE legacies in sustained observations

• TOGA
• - pioneered the concept of an integrated
  observing system on a basin scale.
• - installed long-term tropical observing
  networks TAO/TRITON, broad-scale XBT, surface
  drifter, sea level.
• - provided near real-time public datasets.
• WOCE
• - extended the domain of XBT, surface drifter,
  sea level.
• - produced a baseline global hydrographic
  survey.
• - installed additional long-term observations
  High Resolution XBT/XCTD network, time-series
  stations.
• - devised critical new instrumentation (e.g.
  profiling float, IMET systems) for sustained
  global observations.
• - integrated satellite and in situ
  observations with models on a global scale.

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• Deep ocean repeat hydrography

http//whpo.ucsd.edu/whp_data.htm

• Objectives
• Investigate variability in water mass
  inventories, physical and biogeochemical
  properties, and renewal rates.
• Learn the nature of deep ocean circulation
  variability - how it responds to and influences
  the global climate system.

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High Resolution XBT/XCTD Network

• Objectives
• measure variability in transport of mass, heat
  and freshwater.
• determine mean fields and statistics of
  variability.
• Some lines sampled quarterly for gt10 yrs.

A typical temperature transect includes 300
profiles, with spacing as tight as 10 km in the
Kuroshio. Salinity is estimated from sparse
XCTDs. VOS IMET systems are being
installed. http//www-hrx.ucsd.edu,
http//www.aoml.noaa.gov/phod/hdenxbt/
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Recent results from a single HRX
line Meridional heat transport across the
tropical/ subtropical boundary of the North
Pacific (1-year running mean, Roemmich et al,
JGR, 2001).
ECMWF air-sea flux
Heat transport
Eddy-induced mean overturning circulation from a
model (left, McWilliams and Danabasoglu, JPO,
2002)) and from HRX data (right, Roemmich and
Gilson, JPO, 2001)
Kuroshio transport south of Taiwan, from
individual HRX cruises, using 2 definitions of
the Kuroshios offshore edge (Gilson and
Roemmich, JO, 2002)
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Argo Global snapshots of temperature, salinity
and circulation every 10 days - over 100,000
profiles annually
Argo Network as of November 12, 2002 - 571 floats
15 nations providing floats
An Argo float
Conceptual map of Argo - 3000 floats - in 2005
and beyond. About 2000 Argo floats are already
funded.
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NZ Argo float deployment
Recent (Nov 9) profile from Float 2039
All Argo data are freely available via GTS and
internet. http//www.ifremer.fr/coriolis or
http//www.usgodae.org
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Pacific and Indian deployment plans.
Large numbers of Argo floats will be deployed in
the coming months in all oceans. With most
float-providing nations in the Northern
Hemisphere, the challenge is to populate the vast
Southern Hemisphere oceans in order to produce a
global Argo array.
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Time-series stations

• Time-series data at fixed points complements
  broad-scale datasets such as Argo.
• Air-sea fluxes of heat, freshwater and momentum.
• Full depth physical and bio/geochemical sampling.

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A WOCE example is the Hawaii Ocean Time-Series
Station, providing shipboard plus moored
physical and biogeochemical datasets.
http//www.soest.hawaii.edu/HOT_WOCE/index.html
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Challenges to effective implementation I. What
is missing from the observing system? Boundary
currents play a key role in the oceans mass,
heat, and freshwater budgets. An observing
system component for BCs is not yet designed.
It will require substantial regional cooperation
- technical, logistical and political. (Left)
Schematic of Pacific Ocean surface circulation,
from Tomczak and Godfrey (1994).
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Boundary current measurements Gliders and other
autonomous vehicle technologies may offer a cost
effective solution for sustained observations of
boundary currents.
Velocity and density from a glider off southern
California (R. Davis)
One of several autonomous gliders under
development.
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A 4-D Glider survey
Port
35oN
Argo floats
WBC
Glider track total length 4000 km (160 d)
follow meanders by seeking isotherm depths
Port
NEC
15oN
LLWBC
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Challenges II. Biogeochemical measurements Can we
systematically introduce new sensors into the
observing system?

• Repeat hydrography and time-series stations have
  been the starting points floats and gliders will
  be more difficult.
• Many new sensors are possible and some have been
  tested.
• The multi-user aspect of the OS is a critical
  selling point, but careful judgements are
  necessary for initiating long-term measurements.

Water-catching in the pre-WOCE era (J. Swift).
Float with POC light attenuation sensor (J.
Bishop)
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Challenges III Observations and Models Can the
evolution of the OS be harmonized with the state
of modeling and data assimilation, and the
results used to demonstrate the value of the OS?

• Observations are required to
• Provide data and statistics for model
  initialization and data assimilation.
• Provide independent information for testing model
  results and model processes.
• Discover new phenomena not anticipated by models,
  thereby stimulating model improvement.

(Above) NCEP net air-sea heat fluxes are adjusted
for consistency with ocean data.
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In addition to satellite data, there is a strong
need for subsurface datasets appropriate for
basin to global scale model testing.
(Above) Maps of SSH variability (RMS) for a 1/10o
Atlantic model (left) compared to blended
TOPEX/ERS data (right) - Smith et al, JPO, 2000.
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Challenges IV The research/operations interface.

• A definition of operational oceanography is
• its objectives and characteristics can be
  specified in advance.
• it has an indefinite operating life and evolves
  cautiously.
• its success is judged by contributions with
  public.
• By this definition, the TAO/TRITON Network is
  operational.

For the OS to succeed, it must have vertical
integration (instrumentation development, network
design, implementation, data management,
scientific analysis, data assimilation) as well
as horizontal integration across the observing
system elements. Research objectives of the OS
will be seriously compromised if data collection
is de-coupled from the other functions.
(Right) A TAO/TRITON Buoy
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Why?

• The research community designed and implemented
  the present observing system, and has
  demonstrated its capacity and commitment for high
  quality long-term observations.
• Technical improvements continue to expand the
  capabilities and efficiency of instrumentation.
• While there is need for stability, OS design will
  continue to evolve as understanding of sampling
  requirements increases.
• An operational OS will require full partnerships
  between research institutions, instrument
  manufacturers, and operational agencies.

A French Argo float
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Challenges V Data and information management. To
serve the needs of multiple users, data
management and delivery systems must become
increasingly sophisticated and versatile - and
they require resources.
Example The Argo Data System provides both near
real-time data for operational applications, and
a scientifically QCed dataset for
research. Argo Global Data Centers merge the
data from all floats and maintain best copy
profile and trajectory data and
metadata. http//www.ifremer.fr/coriolis or
http//www.usgodae.org
Schematic of data flow in Argo
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Summary

• A major legacy of WOCE and TOGA is the creation
  of a global ocean observing system for climate.
• The global observing system is started but is far
  from complete. There are major challenges ahead
  for full implementation and maximum value.
• We have a one-time opportunity and a
  responsibility to society to implement an
  efficient and effective observing system of the
  oceans role in climate.