OceanObs’09
Community White Paper Proposal
Title
[Gliders as a component of future observing systems]
Lead author
[Pierre Testor, LOCEAN-IPSL/CNRS, Université Pierre et Marie Curie, Paris,
France, testor@locean-ipsl.upmc.fr , +33 1 44 27 72 75]
Contributing authors
[Joaquin Tintore, Bartolomeo Garau, IMEDEA, Esporles, Spain]
[Martin Visbeck, Johannes Karstensen, Gerd Krahmann, IFM-GEOMAR, Kiel,
Germany]
[Alberto Alvarez, NURC, La Spezia, Italy]
[David Smeed, Gwynn Griffiths, NOCS, Southampton, UK]
[Svein Osterhus, Bjerknes Centre for Climate Research, Norway]
[Uwe Send, Russ Davis, Daniel Rudnick, SIO, La Jolla, CA, USA]
[Breck Owens, David Fratantoni, WHOI, USA]
[Charlie Eriksen, Craig Lee, UW-APL, Seattle, WA, USA]
[Oscar Schofield, Scott Glenn, Josh Kohut, Rutgers Univeristy, USA]
[Gary Meyers, IMOS, Hobarth, Australia]
[Laurent Mortier, LOCEAN-IPSL/ENSTA, Université Pierre et Marie Curie, Paris,
France]
[Hervé Claustre, LOV/CNRS, Villefranche/m, France]
[Pascale Lherminier, Thierry Terre, LPO/IFREMER, Brest, France]
[Loic Petit de la Villeon, CORIOLIS/IFREMER, Brest, France]
Description
[The marine environment is a complex system, characterized by strong interactions
between physical, chemical and biological processes. The high spatio-temporal
variability of these processes (1-1000km ; days-years) and their interactions make
difficult their study: first, there is a need to measure physical, chemical, and biological
parameters simultaneously and second, they impose to carry out ocean
measurements at high spatial and temporal resolutions.
Observations of the marine environment have been traditionally carried out by
oceanographic ships, moorings and floats. All these observing platforms can carry
out interdisciplinary measurements of the ocean, but not always with the spatiotemporal resolution required. The key point here, is to avoid any aliasing effect
leading to erroneous conclusions. The widest variety of interdisciplinary
measurements at high spatial resolution can be obtained from oceanographic ships.
Unfortunately, logistical and economical aspects involved in oceanographic ships
usage invalidate them as platforms able to carry out continuous and sustained ocean
observations. With less capacity concerning the measured parameters, ships of
opportunity can be used for ocean monitoring but they need to be manned on each
trip and are constrained by existing maritime routes so they do not always pass the
sections of maximum scientific interest.
Unlike oceanographic ships, moorings provide interdisciplinary data with very high
temporal resolution over long periods. Nowadays, moorings can operate for more
than five years. Satellites and surface buoys and/or submarine cables can convert
them into sustained ocean observing platforms, allowing near real time data transfer
from moorings to land bases. However, the spatial resolution is very poor unless an
unrealistic number of moorings is considered. Profiling floats naturally drift away from
their deployment locations according to currents and cannot be used to maintain
measurements in a particular region, unless a very high number of floats is used to
monitor the ocean in a global way as it is done in the framework of the ARGO
program. At the moment, floats are mainly used to carry out physical measurements
because the cost of biogeochemical sensors prevent them to be deployed as
massively as required for this "random" sampling strategy.
A notorious advance in ocean knowledge has been achieved with the above
described ocean observing platforms, but ocean monitoring is still insufficient.
Limitations of conventional ocean observing platforms avoid monitoring the ocean at
adequate spatial and temporal resolutions. For this reason and with the help of
present technological development, new ocean observing platforms able to be
steered remotely and to carry out continuously ocean measurements at high spatial
and temporal resolution, have been developed. Gliders come from the idea that a
network of small, intelligent and cheap observing platforms can fill the gaps leaved
by the other observing platforms for the in-situ observation (physical and
biogeochemical).
Since the early glider deployments for development, the use of gliders fro
oceanographic research has been increasing regularly. This platform has now
reached a stage allowing not only glider developers but also other teams of
oceanographers to deploy gliders and collect in-situ data for their scientific
objectives. Single deployments of gliders but also coordinated deployments of fleets
(of a dozen) have been carried out with success. Endurance lines or repeat-sections
have been maintained for months or even years. The gliders are considered to be
used in conjunction with moorings to assess the spatio-temporal variability around
them but also as 'messengers' (with acoustics) for data telemetry or even as possible
platforms for data collection under sea ice (with acoustic positioning). Gliders have
proven they can provide both physical and biogeochemical data as a number of
small and low-energy sensors has been tested on them: CTD, oxygen, as well as
backscatter and fluorescence at various wavelengths.
The next step is to define the role of gliders in the future observing systems that are
required by fundamental research and operational oceanography. One can
distinguish four in-situ observing strategies:
1) Process studies: many oceanic processes at (sub)mesoscale (1-100km,
weeks) require further investigation and observations at these scales.
2) Observing systems for scientific projects: many scientific projects aim to
address the oceanic variability at low frequency and have set up observing
systems on a relatively long term (years) like repeated transoceanic sections
or mooring arrays in particular areas.
3) Observatories: often with a multidisciplinary approach, observatories are set
for decades in particular areas or at global scale.
4) Operational oceanography: the main focus is the real time data flow with the
major constraint of quality control. Data centers collect these data and
distribute them in a worldwide network including operational forecasting
models.
On behalf of the EGO group (http://www.locean-ipsl.upmc.fr/gliders/EGO ) we will
review in this white paper the possible roles of gliders in all these observing
strategies and provide recommendations, including technical developments,
temporal and spatial sampling requirements, core variables, measurement methods
and protocols, calibration procedures, standards, data sharing and release policy,
data assembly and archival.]