Argo’s
Role in Climate Science
Kimio Hanawa
Department of Geophysics, Graduate School of
Science, Tohoku University
Aoba, Sendai 980-8578, Japan
hanawa@pol.geophys.tohoku.ac.jp
Within the next several years, a monitoring system
using Argo floats will be completed, and approximately 3000 Argo
floats will provide temperature-salinity profiles from the sea
surface to the depth of 2000m in the world’s oceans every 10
days. We are to obtain numerous hydrographic data. The Argo project
will provide one hundred thousand profiles a year, and the impact of
the project on the academic field and the resultant societal field
will be tremendous.
It goes without saying that the Argo project is a most
important tool in observing the ocean.
The CLIVAR sciences will also reap
great benefit from the Argo project. One of the targets of the CLIVAR
sciences is to describe the decadal-to-multidecadal scale climate
phenomena found in various oceanic sectors, to elucidate their
mechanisms, and to explore their predictabilities. It is widely
accepted that the ocean plays a crucial role in these time scale
climate variations. Although limitation/lack of oceanic data have
hindered the progress of research in this field so far, the Argo
project is expected to improve this situation dramatically.
In my presentation, the
expectations of the Argo project in the CLIVAR sciences will be
discussed, based on our recent studies.
|
Argo and GODAE
Pierre-Yves Le
Traon
CLS
Space Oceanography Division
8-10 rue Hermes - Parc Technologique du
Canal
Ramonville St Agne 31526
FRANCE
letraon@cls.fr
The Global Ocean Data Assimilation Experiment
(GODAE) is conducting its main demonstration phase from 2003 to 2005.
From 2003 to 2005, operational and research institutions from Europe,
Australia, Japan and the United States will be performing global
ocean data assimilation and ocean forecast in order to provide
regular and comprehensive descriptions of ocean fields such as
temperature, salinity and currents at high temporal and spatial
resolution.
GODAE will provide an integrated description of the ocean
that combines remote sensing data, in-situ data and models through
data assimilation. One of the objectives of GODAE is thus to
maximize the benefits from the data (in particular altimetry and
Argo). To achieve these goals, it is necessary to develop effective
assimilation techniques of Argo data. A central issue is to
effectively merge Argo data with remote sensing data for the
description of the global ocean at high space and time resolution.
A review of GODAE
progress will be first given. We will then focus the presentation on
the use of Argo data by GODAE and the contribution of Argo data to
the experiment. Important issues and perspectives for the coming
years will be finally given.
|
Argo Float Technology:
Achievements and Challenges
Stephen Riser
School of Oceanography
University of Washington
Washington
98195
USA
riser@ocean.washington.edu
The predecesors of the profiling floats employed in
Argo were developed for use in the World Ocean Circulation Experiment
(WOCE) in the early 1990s. The floats in WOCE were used mainly for
making direct estimates of the deep velocity field of the world
ocean. The Argo floats of today are equipped with CTD sensors that
provide data of a quality comparable to that of shipboard
observations, and these CTD profiles are probably the most important
part of the data provided by the floats; clearly profiling float
technology has evolved a great deal since WOCE in the 1990s. This
ability to collect high quality CTD data from unattended platforms
over the course of several years is a major technological achievement
that is required by Argo and in a sense makes the program viable. As
originally planned, the Argo program consists of 3000 floats that
collect CTD profiles at regular intervals over the course of 4-5
years. Present float technology is adequate for realizing these
goals: floats can be deployed nearly anywhere in the world ocean by
a variety of methods, and float reliability has improved greatly in
recent years. At the present time, new communication systems and
biological, acoustical, and chemical sensors are being tested that
will likely become operational in the next few years. These
developments are likely to revolutionize our view of the world ocean
and contribute directly to improved ocean models and forecasts.
|
The Argo data system
Bob Keeley
Marine Environmental Data System (MEDS)
Fisheries and
Oceans Canada,
200 Kent St,
Ottawa, On, K1A 0E6
Canada
keeley@meds-sdmm.dfo-mpo.gc.ca
Sylvie
Pouliquen
Chef
de projet Coriolis
IFREMER Centre de Brest,
BP70,
Plouzané29280,
France,
Sylvie.Pouliquen@ifremer.fr
The Argo Data System is built
around the individual processing systems of Argo Project contributors
and on a global data server, mirrored at two sites, from which the
master versions of the data are available. In order for this highly
distributed system to work, it is necessary to standardize many
aspects. In particular standard quality control procedures have been
developed for the real-time data, and are being finalized for data
processed in delayed mode. A standard exchange format allows data to
be uploaded to the global servers and for users to visit and download
data of interest. The global servers permit both ftp and www access
and have tools to allow subsetting and some data display
capabilities.
Other components of the data system include the Argo
Information Centre, a global data repository for long term archiving,
and regional centres. Not all of these are in place as yet. This
presentation will explain the data system with a focus on how to get
data, how to use them, and how to know what has been done to
them.
|
Argo delayed-mode salinity
data
Annie
Wong
NOAA/Pacific Marine Environmental Laboratory
7600 Sand Point Way
NE, Bldg. 3
Seattle, WA 98115
USA
awong@pmel.noaa.gov
One of the main ocean parameters measured by Argo
is salinity. However, salinity measurements from profiling floats
often experience artificial drifts and jumps that are
sensor-related.
The
free-moving nature of these floats means that most float salinity
data are without accompanying in-situ standards for absolute
calibration.
A set
of delayed-mode procedures has been designed to provide quality
control to Argo salinity data, as well as to correct the artificial
drifts and jumps.These salinity adjustments are not absolute
calibrations, but are adjustments obtained by statistical methods
with associated uncertainties. In most oceanic regions,
Argo delayed-mode salinity
data are accurate to 0.01 (PSS-78).
|
Design Requirements for an ARGO Float Array in the Indian
Ocean Inferred from Observing System Simulation Experiments
Andreas Schiller, Susan E.
Wijffels and Gary A. Meyers
CSIRO Marine Research
GPO Box 1538
Hobart, 7001
Tasmania
Australia
andreas.schiller@csiro.au
Model experiments with an OGCM have been
performed to assess sampling strategies for ARGO floats in the
Indian Ocean on intraseasonal-to-seasonal time scales. The results
suggest that a minimum requirement for resolving intraseasonal
oscillations in the upper ocean is predominantly determined by their
spatial scales, i.e. about 500km in the zonal and about 100km in the
(equatorial) meridional direction.
Frequent temporal sampling becomes
particularly important in dynamically active areas such as the
western boundary current regime and the equatorial waveguide. High
frequency sampling is required in these areas to maintain an
acceptable signal-to-noise ratio, suggesting a minimum sampling
interval of 6 days for capturing intraseasonal oscillations in the
upper Indian Ocean.
Sampling of seasonal-and-longer-term variability down to
2000m depth is less critical within the range of sampling options of
Argo floats, as signal-to-noise ratios for sampling intervals up to
about 20 days are almost always larger than one. However, these
results are based on a single OGCM and are subject to model
characteristics and errors. Based on a coordinated effort, results
from various models could provide more robust estimates by minimizing
the impact of individual model errors on sampling strategies.
|
Experience of delayed mode quality control for float
salinity data in the Atlantic
Yves Desaubies, Carole Grit, Y. Izenic
Laboratoire de
Physique des Océans
IFREMER Centre de Brest, BP70,
Plouzané 29280,
France
U. Send, L. Boehme
Institut
für Meereskunde, Kiel University
Yves.Desaubies@ifremer.fr
As part of the GyroScope project, some 84 floats
were deployed in the Northern and North East Atlantic, from summer
2001 to autumn 2002. With a view to compare instrumental
performances, two types of floats were used, in approximately equal
numbers : APEX™ with Seabird sensors, and Provor™ with FSI
sensors. The deployment area include such diverse ocean provinces as
the Irminger and Labrador Seas in the subpolar gyre; the inter-gyre
region of the NE Atlantic; the North Atlantic and Azores currents;
and the Canaries basin in the Subtropical gyre. Correspondingly, a
variety of water masses and fronts are encountered.
In an effort to perform
Delayed Mode QC (DM-QC), the algorithm of Wong et al. (2003), in its
latest release, has been implemented and tested on the float data.
On average, the floats have about 50 profiles. Calibration of the
algorithm on CTD indicated that it performs well, with error bars of
the order of 0.01 psu.
The WOD 2001 has been augmented with recent CTD data,
leading to reduced variance in the estimates.
Because of high space and time
variability in the subpolar gyre, the parameters in the method have
been adapted to account for fronts and anisotropic co-variances, with
the result of reduced error bars in the correction estimates.
Float to float
comparisons have been introduced, as a complementary indication of
whether departures from climatology are real or due to instrumental
error.
Preliminary results indicate that it will be difficult to
implement automatic DM-QC procedures; in general the floats are
reasonably stable (to within 0.04 psu), with no evidence of linear
drift. There are several instances where the climatological mapping
errors underestimate the variability, and therefore over-constrain
the method. Complementary methods (see poster by Gaillard et al),
which systematically use a wider and more recent data set, will be
useful in building up progressively updated climatologies, and
therefore reducing uncertainty in the corrections.
Partially funded under the 5th Framework Programme,
"Global change, climate and biodiversity " ; contract
EVK2-CT-2000-00087
|
What observation scheme should we use for
profiling floats
to achieve the Argo goal on the accuracy of salinity
measurement?
Taiyo Kobayashi
Frontier Observational Research System for Global
Change
2-15
Natsushima-cho,
Yokosuka 237-0061
Japan
Shinya Minato (Japan Marine Science and Technology
Center)
taiyok@jamstec.go.jp
To attain the goal of the salinity measurement
accuracy of the Argo Programme (±0.01 psu) the preferable
measurement scheme for profiling float observations is examined from
the view of the delayed-mode quality control. In the subtropical and
subarctic regions of the North Pacific the goal will be generally
achieved by measuring profiles constantly to the depth of 1500 dbar
or more. In the tropical Pacific and the eastern Indian Ocean, the
1000 dbar profiles give sufficient quality of salinity data. In Mixed
Water Region, however, it is difficult to reduce the correction
errors within ±0.01 psu even if the profiling floats measure
the profiles down to 2000 dbar constantly.
About a new observation scheme developed by Prof.
Riser at University of Washington, we can find almost no reasons to
positively adopt it for the profiling floats, at least from the view
of the delayed-mode quality control of the Argo Programme.
|
Float to float drift intercomparison in an
intermediate current regime
Francisco MachÌn
Campus de Tafira, Departamento de
FÌsica,
ULPGC,
Las Palmas 35017
Spain
Uwe Send and Walter Zenk.
Institut für Meereskunde
Dusternbrooker Weg
20,
24105
Kiel
Germany
fmachin@becarios.ulpgc.es
An improved series of underwater drift vectors has
been estimated from a 15 days-cycling APEX float in the presence of
an intermediate current regime near the Mid-Atlantic Ridge. In a
statistical approach these estimates are compared with the velocities
inferred from a park ensemble of four eddy-resolving RAFOS floats.
They were deployed at the same location and ballasted for the same
mission depth. We develop an extrapolation scheme to correct the
surface drift information of the cycling float by data transmission
parameters intrinsic to the satellite tracking ARGOS system.
A tendency towards
a slightly (3%) higher in situ APEX speed is notable. The initial
float separation between the cycling float and a simultaneously
deployed RAFOS float has also been studied in terms of spatial and
time scales of the velocity field. Additional displacement errors
induced by geostrophic shear and wind forced currents are found to
express only a second order source of inaccuracy. Estimated
underwater velocities from the cycling float are in good agreement
with the synoptic velocity field deduced from the RAFOS ensemble.
Though the application of these results in comparable cases without a
mean current field may be limited, such oceanic observations support
the exploitation of the Lagrangian nature of the cycling floats with
an improved statistical confidence.
|
A comparison of profiling
float and XBT representations of upper layer temperature structure in
the Northwestern subtropical North Atlantic
Robert L. Molinari
National Oceanic and Atmospheric
Administration
Atlantic Oceanographic and Meteorological Laboratory
4301 Rickenbacker
Causeway,
Miami,
Florida 33149
USA
Bob.Molinari@noaa.gov
Profiling floats were deployed in
the subtropical and subpolar North Atlantic as a component of the
Atlantic Climate and Circulation Experiment (ACCE), the last field
phase of the World Ocean Circulation Experiment. The floats were
primarily instrumented with temperature sensors and ballasted to
drift at 1000m for 10 days. ACCE floats were active from 1998 to
2001.
Previous
studies have identified a shallow recirculation gyre located above
the total water column inertial recirculation gyre observed south of
the Gulf Stream. The shallow gyre has a seasonal cycle that has been
characterized using satellite and expendable bathythermograph data.
Maximum gyre size is observed in the fall and minimum size in the
spring. Mapping the float data with bi-monthly resolution reproduces
this annual cycle. Similarly, a decadal signal appears in the size
of the gyre. The floats reproduce the changes in gyre size
associated with this signal over the period of concurrent data.
|
The impact of Argo data on ocean and climate
forecasting
Matt Martin
Met Office,
FitzRoy Road,
Exeter, EX1 3PB
United
Kingdom
matthew.martin@metoffice.com
A number of operational ocean forecasting systems,
including both seasonal coupled forecast systems and higher
resolution short-range ocean forecast systems, have been assimilating
Argo data since it became routinely available. Studies to assess the
direct impact of different data types have been carried out. These
have withheld Argo temperature and salinity data and/or altimeter
data from the assimilation. The results of these studies will be
presented and discussed.
Argo data also have an impact on other aspects of operational
forecasting systems. Statistically meaningful verification of
analyses and forecasts requires a large volume of data. This
verification can help to highlight deficiencies in the model and
analysis and so lead to improvements in both components of the
system. For statistically optimal data assimilation, estimates have
to be made of the error covariances for both the model forecast and
observations. These can be calculated using statistics of
observation-minus-model values but a large volume of data is required
to do this. Improvements to the way in which altimeter data are
assimilated are expected to be gained through use of Argo data. Argo
data can also be useful for tuning and testing mixed layer
parameterisations which are important for short-range
forecasting.
|
|
Ocean state estimation by 4D-VAR data assimilation using
Argo Data
Shuhei Masuda
Frontier Research
System for Global Change
3173-25 Showa-cho, Kanazawa-ku
Yokohama, 236-0001, Japan
smasuda@jamstec.go.jp
Data assimilation approaches
have recently focused on obtaining an optimal synthesis of
observational data and model results for better descriptions of the
ocean state. By using an ocean general circulation model and the
4D-VAR adjoint method, we have constructed a global ocean data
assimilation system, which provides a comprehensive 4-dimensional
reanalysis dataset based on available observational data.
Firstly, a data
assimilation experiment is performed to define a mean seasonal state
of the global ocean. The assimilated elements in this experiment are
the climatological monthly temperature and salinity fields from WOD98
and sea surface height anomaly data derived from TOPEX/Poseidon
altimetry. The obtained reanalysis dataset shows good consistency
with previous knowledge of the ocean state and surface conditions.
For example, the North Pacific Intermediate Water, which is
characterized by a subsurface salinity minimum, is successfully
reproduced. However, some important features in subsurface layers
are missed due to the absence of the corresponding structures in
WOD98 (e.g., dichothermal and mesothermal structures in the eastern
subarctic region). This result shows that higher quality subsurface
data is required for further improvement of the ocean state
estimation by the state-of-the-art data assimilation system.
The ARGO data is
most promising in this aspect because it can provide higher quality
subsurface information covering the entire ocean. Using this
advantage of the ARGO data, our system is currently applied to a
long-term experiment for the last decade with an aim to investigate
the impact of the ARGO data on the ocean state estimation.
|
A
regional model assimilating ARGO, XBT, and altimeter data in the
central North Pacific
Bruce
Cornuelle, Josh Willis, Dean Roemmich
Scripps Institution of Oceanography,
University of California San
Diego
9500 Gilman
Drive
La Jolla
CA 92093-0230
USA
bdc@ono.ucsd.edu
In the central ocean basins, far
from the boundaries and from steep topography, quasi-geostrophic (QG)
dynamics are thought to hold. Chelton and other authors have examined
the westward propagation of sea surface height anomalies and have
seen a good match with QG theory. In this work, we attempt to fit an
eddy-resolving, regional, nonlinear quasi-geostrophic model to
altimeter and in-situ observations, including ARGO profiles.
The
quasi-geostrophic relations reduce the unknowns to a single field,
the streamfunction, from which all other variables are derived by
assuming geostrophic balance and adiabatic motion. This is more
efficient than estimating temperature, salinity, density, and
velocity separately and applying diagnostic constraints
(adiabaticity, geostrophy and non-divergence) explicitly. The
streamfunction expansion in vertical eigenmodes works best in a
region with weak horizontal variation in the background ocean and in
the topography. For this application, the model used the barotropic
and the first two baroclinic modes, with the horizontal structure of
each mode specified by a Fourier expansion periodic in each
direction.
The model
produces a dynamical synthesis of the multiple data streams that has
greater skill in tracking the eddies than statistically based mapping
schemes, and we hope to demonstrate model skill in forecasting and in
cross-validation. It is anticipated that Argo data will be critical
in providing the information on the baroclinic structure of the
eddies that will allow the model to converge to the true field. This
will be illustrated using twin experiments and fits to observations.
While the QG model is not appropriate for global assimilation, it is
a powerful tool for regional studies and for understanding the impact
of data in assimilations.New elements of the Japan Sea oceanography
found with the use of profiling floats.
|
Assimilating S(T) from
Argo
Keith
Haines
3
Earley Gate, Whiteknights
Reading University
Reading RG6 6AL
UK
Arthur Vidard ECMWF
Xiaobing Zhou Reading University
Alberto
Troccoli ECMWF
David Anderson ECMWF
kh@mail.nerc-essc.ac.uk
Assimilating salinity data, along with temperature,
into ocean models should allow for the better analysis of water
properties and volumes over whole regions of the ocean. This would
allow for better assessment of climatically important changes in
water characteristics, that are normally only possible from repeat
section hydrography.
The paper will present preliminary results from
assimilating Argo data into the ocean component of the ECMWF seasonal
forecast model. A two-stage process is used. (1) Temperature (from
Argo and other data sources, XBT, TAO ...) is assimilated and the
salinity is incremented to retain the S(T) relationship present in
the model. This has previously been shown to greatly improve the
salinity reproduction in the ECMWF model compared with leaving the
salinity field unchanged. (2) Then the S(T) (from Argo) is
assimilated directly, using a covariance function which is dependent
on both horizontal separation and separation in temperature space.
The method allows for larger spatial scales to be used, thus allowing
a wider influence of the salinity data as a measurement of S(T). Some
illustrations of this scale difference from using a conventional
covariance function for S will be shown.
Ongoing plans are to produce a 40 year
reanalysis of ocean properties and circulation, from which changes in
S(T) properties and volumes of water masses can be diagnosed, where
and when sufficient data are available.
|
Argo impact experiment
with a JMA ENSO forecast model,
Yoshiteru KITAMURA
Climate Prediction Division,
Japan Meteorological Agency
1-3-4, Otecmachi, Chiyodaku,
Tokyo 100-8122
Japan
ykitamur@met.kishou.go.jp
The operational global
ocean data assimilation system and ENSO forecast model at Japan
Meteorological Agency (JMA) was revised in 2003. In a new ocean data
assimilation system, salinity observations and altimeter data were
assimilated in addition to temperature. A 3D variational analysis
scheme and an incremental update scheme were introduced. A coupled
general circulation model was replaced to an advanced model with
higher resolution. These changes, particularly inclusion of
salinity, may be favorable for effective use of Argo data for ENSO
forecast.
Several
forecast experiments initialized with and without Argo data were made
in the period of 2001-2002. The results are compared and the
practical impact of Argo data on ENSO forecast is discussed.
|
Argo’s role in closing the oceanic heat and
freshwater budgets
Dean
Roemmich, Josh Willis, and John Gilson
Scripps Institution of Oceanography
University of
California San Diego
La Jolla CA92093-0230
USA
droemmich@ucsd.edu
A primary objective of global ocean observations
is to close the mass, heat, and freshwater budgets of the oceans -
regionally and globally on seasonal to decadal time-scales. Three
illustrative calculations are presented to demonstrate the central
role of Argo in this endeavor, as well as Argo’s integrative
value with other observing system elements.
First it is shown that on seasonal time-scales, where a close
balance is known to exist between ocean heat storage and air-sea
flux, there is already sufficient Argo data to provide a quantitative
global comparison of ocean heat storage with operational air-sea
fluxes. The agreement between zonally averaged storage, calculated
from successive cycles of Argo floats, and air-sea flux, is
surprisingly good. Second, a new technique for combining subsurface
data with satellite altimetry and SST (Willis et al, JGR 2003, In
press) is applied to estimate global ocean heat content and storage
for 1993 - 2002. Heat gain by the upper ocean, 0-800 m, averaged 1.0
+/- 0.3 W per meter-squared of ocean surface, accounting for about
65% of sea level rise during the period, through thermal expansion.
The 1997 El Nino
produced the strongest feature in global heat gain, but the maximum
in heat content occurred in late 1999. In a zonally integrated sense
the greatest heat gain occurred at 40-degrees S (5 W/m**2), but there
was also strong warming in the northern North Atlantic and the
western tropical Pacific. The calculation illustrates both the power
of combining Argo and altimetry and the further advantage that will
be gained when the Argo array is fully deployed.
Finally, a closed regional heat
budget is described using a decade of data in the southwestern
Pacific, where broadscale temperature profiling has been comparable
in coverage to that planned for Argo. This region includes the East
Australian Current and is bounded by High Resolution XBT/XCTD
transects that are used to calculate the time-varying circulation
across the faces of the region and the advective heat flux
convergence. Over the 12-year period of the study, mean advective
heat flux convergence averaged over the region was 43 W/m**2, of
which 3 W/m**2 was stored and 39 W/m**2 lost to air-sea exchange. The
interannual heat budget was closed with residuals of 10 W/m**2 and
interannual variability of about 30 W/m**2 in all three components
(storage, air-sea flux, and advection). Argo’s contribution is
in making similar heat budget calculations possible on a global
basis, enabling the analogous freshwater budgets, and substantially
decreasing the errors in ocean heat flux convergence and storage (to
0.1 W/m**2 for the global decadal storage calculation).
|
World Ocean heat content, 1955-1999
Sydney Levitus, John Antonov, Tim
Boyer
NODC/NOAA, E/OC5
1315 East West Highway
Silver Spring, MD20910
USA
Sydney.Levitus@noaa.gov
We update our earlier estimates (Levitus et al.,
2000) of ocean heat content for the world ocean with the additional
1.7 million temperature profiles that have become available as part
of "World Ocean Database 2001". The results are
quantitatively similar through the early 1990s but the newer
estimates are lower for the 1990s due to an error in processing the
XBT data for this period in our earlier results. This difference
does not affect any previous conclusions regarding the dominance of
ocean heat content in the earth's heat balance for this period. The
results of multivariate analyses of ocean heat content are
presented.
|
Upper ocean response before and after the cyclone from
Argo floats
Muthalagu
Ravichandran, G. Anita and Uday Bhaskar
Indian National Center for Ocean Information
Services (INCOIS)
No.3,
Nandagiri Hills, Jubilee Hills, Hyderabad 500 033
INDIA
ravi@incois.gov.in
Significant progress has been made over the
past to improve our understanding of the basic oceanic and
atmospheric processes that occur during the passage of tropical
cyclone. Tropical cyclone passage over an ocean represents one of the
more extremeupper ocean response cases as the ocean loses heat to the
atmosphere (Shay 1994). Precipitation effects on the ocean mixed
layer during tropical cyclone passage has generally remained
unresolved due to lack of upper ocean temperature and salinity
profile measurements during and subsequent to storm passage. In order
to understand upper ocean response before and after cyclone, Argo
float is an additional observational capability, that will provide
temperature and salinity profile upto 2000 m in a near real-time. In
this paper, we have studied the behaviour of upper ocean responses
before and after the cyclone using the Argo floats in the Indian
ocean region. We have selected the floats/cyclones such a way that
Argo float data available on both side of the track. We have analyzed
how the difference profiles (pre-post) in the upper 200m, upper ocean
heat content, difference in the depth of the 26°C and 20°C
isotherm (cyclone heat potential), mixed layer depth varies in this
region before and after the passage of storm on both side of the
cyclone track. Also, a float in the Arabian Sea has provided
temperature and salinity profile everyday and has given the
opportunity to see how the upper ocean responded everyday before and
after the cyclone. It has been observed that the themocline just
below the mixed layer shows a well defined inertial oscillation of
about 12 m amplitude after the storm.
|
The decreasing of sea
surface salinity by typhoon in the summer of 2002 and 2003 in the
northwestern Pacific
Xu
Dongfeng
Key
Laboratory of Ocean Dynamic Processes and Satellite Oceanography
Second Institute of
Oceanography, SOA,
9# Xi
Xihexia Road
Hangzhou 310012,
China
xudongfengyhcn@yahoo.com.cn
The tropical storms in Atlantic can induce
increased SSS and decreased sea surface temperature (SST), which is
evident from the 100 ARGO floats results (Kwon and Riser, 2002, in
press). The decreasing of SST is because the losing of heat from
ocean to the atmosphere and the intensified mixing with the cold
water below the thermocline for the strong wind. The increased mixing
by the fierce wind of storm also intenses the mixing in the
mixed-layer and deepen the mixed-layer, which results in increased
SSS for the mixing of SSS with the Subsurface Maximum Salinity
Layer.
But the
heavy rain during the Typhoon passage can decrease the SSS. We use
the data of Argo in northwestern Pacific to study the effect of
Typhoon Chataan (July 01～10, 2002), Halong (July
07～15, 2002) passed over Northwest Pacific. The salinity
profile of Argo floats of ID: 5900173, 5900175 and 2900184 all show
decreased SSS. Only float ID 5900126 shows increased SSS. In 2003,
floats 5900222, 5900223 and 5900220 all show the decreased SSS
phenomena. The decreasing of SSS and the salinity in the mixed-layer
(about 100m thick in this area) after the pass of Typhoons is very
prominent in most cases. The role of rain of typhoon and the mixing
processes of mixed-layer with the thermocline on the change of SSS
need further study. The reason for the different response of SSS of
Atlantic and northwestern Pacific need further study.
|
Lagrangian observations of the mode water formation in the
North Pacific
Toshio Suga
Department of Geophysics,
Graduate School of Science,
Tohoku
University,
Sendai 980-8578,
Japan
Toshio Suga (1,2), Hiroko Saito (1) and Nobuyuki Shikama
(2)
(1)
Department of Geophysics, Graduate School of Science, Tohoku
University
(2)
Frontier Observational Research System for Global Change
suga@pol.geophys.tohoku.ac.jp
Lagrangian observations of the formation and
modification processes of North Pacific Central Mode Water (NPCMW)
have been pursued by means of profiling floats programmed to drift at
a specific isopycnal surface rather than an isobaric surface since
early summer in 2002. One of these floats captured the mixed layer
around 37°N, 165°E, which was as deep as 100 m in November
2002 and deepened successively through March 2003, ending up as a
perfectly uniform layer of 26.02sigma-theta thicker than 330m. Its
temperature, 12.82-12.84°C, and salinity, 34.48psu correspond to
those of the lightest variety of NPCMW identified in the isopycnally
averaged climatology, North Pacific HydroBase.
The formation of such thick NPCMW
had not been directly observed before. The float had been drifting
at the 26.5sigma-theta surface lying at 500-550dbar within the
maximum deviation of +/-0.1sigma-theta. It had remained at
36.7-38°N, 164.2-165.8°E and the total distance of its
excursion was about 200km. The heat loss from the top 300m of the
water column was 700-800W/m2 on average during the 4 months from
November 2002, which implies the net surface heat release of
500-700W/m2, assuming the heat advection by the Ekman flow
100-200W/m2 and that by the geostrophic flow negligible. This value
is much larger than the climatological monthly mean net surface heat
flux, ranging from 200 to 300W/m2 in this region for the winter
months, estimated based on the surface marine data.
|
|
|
The detection of subsurface theta-S changes
Brian King
Southampton
Oceanography Centre
Empress Dock
Southampton, SO14 3ZH,
UK
bak@soc.soton.ac.uk
The quality of salinity data from Argo floats has
been even better than anticipated when the program was conceived.
Careful consideration of available reference profiles, for example
CTDs taken on deployment cruises, indicate that many floats are
providing real-time salinity data with absolute accuracy of O(0.01),
which was originally thought of as a target accuracy for carefully
adjusted delayed mode data. This initial accuracy, combined with good
stability for selected floats, has made it possible to observe
subsurface salinity changes as small as 0.04, with a high degree of
confidence, and without needing long time series.
The abstracts for this conference report
observations of property changes at various depths and in all the
oceans. In March 2002 there was a UK research cruise from Durban to
Freemantle along 32°S in the Indian Ocean. CTD data from the
cruise revealed changes in properties since 1987, between the surface
and the Intermediate Water: generally there was an increase in
salinity in the upper thermocline and a freshening in the lower
thermocline. A set of 25 APEX floats deployed on the cruise confirm
that the Mode Water properties are stable (at the 0.01 level) over
large horizontal scales (meridional and zonal) and over a 12-month
timescale. Therefore the inferred changes are not due to aliased
sampling of spatial gradients, nor are they due to seasonal or
interannual variability.
We
can therefore be very optimistic that with careful selection and
calibration of profiles in regional analyses, data from the Argo
array can be used to interpolate between research cruises and so
provide unprecedented temporal and spatial descriptions of subsurface
property variability and trends.
|
Observations of N. Atlantic subtropical mode water using
profiling floats
Young-Oh Kwon and Stephen C. Riser
University of Washington
Box
355351
USA
yokwon@ocean.washington.edu
Basic characteristics of the N. Atlantic Subtropical
Mode Water, also called Eighteen Degree Water (EDW), were
investigated using temperature observations from profiling floats
during January, 1998 - December, 2001. The data allowed a detailed
analysis with monthly time resolution and full spatial coverage of
the EDW region throughout the study period.
The EDW showed a maximum volume in winter
(4.68 ± 0.53 x 10**14 m**3), followed by a gradual destruction
throughout the rest of the year with an annual destruction rate of
2.24 ± 0.61 x 10**14 m**3. Experiments using a simple one
dimensional diffusion model suggest an enhanced vertical mixing
corresponding to a vertical diffusivity of 10**-4 m**2/s is needed to
explain the observed annual destruction rate. Salt fingering at the
bottom of the EDW seems to be the primary factor responsible for the
elevated mixing.
Production
of the EDW was observed during the experimental period, as patches of
the deep winter mixed layer that were concentrated along the southern
flank of the Gulf Stream between 45 and 65°W. The production was
most active in March, and the temperature of newly produced EDW
showed a zonal gradient with the warmest water on the western end.
Interannual variability of the production was well-correlated with
the total volume of the EDW, which also showed good correlation with
the North Atlantic Oscillation (NAO) index.
|
Formation region of North Pacific Subtropical Mode Water
in the late winter of 2003
Eitarou Oka
Frontier Observational Research System for Global
Change
2-15
Natsushima-cho
Yokosuka, 237-0061
Kanagawa
Japan
Toshio Suga
FORSGC and
Department of Geophysics, Graduate School of
Science,
Tohoku University, Sendai, Japan
okae@jamstec.go.jp
The structure and properties of the mixed layer in the
formation region of the North Pacific Subtropical Mode Water (STMW)
east of Japan are presented for the late winter of 2003, using the
temperature and salinity data mainly from Argo profiling floats. The
formation region extends south of the Kuroshio Extension between
30°N and 35°N as far east as 175°E, characterized by the
mixed layer deeper than 200db, the meridionally uniform temperature
between 16.5°C and 18.2°C, and the associated mixed layer
front at the southern boundary. The mixed layer in the formation
region becomes colder, fresher, denser, and shallower toward the east
with the significant mesoscale variations, leading to the formation
of warmer, saltier, lighter, and thicker STMW in the farther western
part of the region. The spatial variation of the mixed layer depth in
the formation region depends largely on that of depth of the
underlying permanent thermocline.
|
Winter conditions in the Irminger Sea revealed by Argo
floats
Luca Centurioni and
W John Gould
Scripps Institution of Oceanography
UCSD
9500 Gilman Drive
La Jolla, CA 92093-0213
USA
lcenturioi@ucsd.edu
Argo float profiles have been used to
reconstruct the evolution of the wintertime circulation,
stratification and water mass properties from 1996 - 2003 in the
Irninger Sea, SE of Greenland. Ship board CTDs were used to
calibrate the year-round Argo float salinity data, resulting in a
typical accuracy of about 0.02 .
The data (900 float profiles) reveal the small area in
which stratification (in February and March) becomes weakest and a
secondary elongated (parallel to the bottom topography) region in
which stratification also becomes weak.
There has been much speculation about whether the
Irninger Sea could be a site for deep winter convection. While there
have been many CTD surveys of the area in recent years, virtually all
have been in the spring, summer and autumn months. In the region of
densest mixed layers no profiles show mixed conditions from the
surface to depths greater than 500m. The heat content of the water
column show that deep convection, for the period examined, is not
likely to have occured.
The large seasonal and interannual variability at all
depths in this region requires the continuing collection of ship
based CTDs. Even if these data are collected in summer they can be
used to calibrate floats so as to explore variability throughout each
year and between years.
|
Structure and
Variability of the Indian Ocean as revealed from ARGO observations
Krishnan
Raghavan
Climate and Global Modelling Division,
Indian Institute of Tropical
Meteorology,
Dr.Homi Bhabha Road,
NCL-Post, Pashan,
PUNE-411008,
INDIA
K.V. Ramesh, M.Ravichandran and Uday
Bhaskar
Indian National Centre for Ocean Information Services
(NCOIS)
Hyderabad,
INDIA
krish0365@yahoo.com / krish@tropmet.res.in
Lack of continuous subsurface
measurements in the past, has been a major limitation in documenting
the structure and variability of the Indian Ocean. The recently
deployed ARGO float network in the Indian Ocean has provided a unique
and unprecedented opportunity to study the large-scale dynamical
processes contributing to the upper ocean variability in this region.
By synthesizing ARGO
measurements along with XBT observations (from cruises) for the
period (Jan 2002 - Sep 2003) and the WOA2001 dataset, we have carried
out a detailed analysis of the spatio-temporal evolution of
subsurface temperature and Sea Surface Temperature (SST) in the
Indian Ocean. In addition, other datasets such as Sea Surface Height
anomalies from TOPEX/POSEIDON; surface winds from QUICKSAT; SST from
TMI; Rainfall from CMAP dataset and Outgoing Longwave Radiation from
NOAA satellite - are used to understand the interactions between the
upper ocean and the overlying atmosphere. The seasonal cycle of SST
and subsurface temperatures clearly shows the semiannual component of
the Indian Ocean response to seasonal reversal of the monsoon winds.
In addition, prominent
intra-seasonal signals are noted in the oceanic temperature
variations. Furthermore, the observations clearly reveal that
significant changes both in the SST and subsurface temperature are
associated with the inter-annual variability of the Southwest Monsoon
circulation. The findings from the present observational analysis
will be presented in detail.
|
A
preliminary study of mesoscale eddy effects on the formation of the
North Pacific Subtropical Mode Water
Pan Aijun and Liu Qinyu
Physical Oceanography
Lab,
Ocean
University of China,
Yushan street 5th,
Qingdao
China 266003
iceking@lib.ouc.edu.cn
We provide an elegant view on the formation
process of the North Pacific Subtropical Mode Water (NPSTMW) in 2001
using newly observed temperature and salinity data from Argo
profiling floats in the Kuroshio recirculation region.
Vertical homogeneous water mass
characterized by Potential Vorticity (PV) lower than 1.5-10m-1s-1 is
formed south of the Kuroshio with temperature about 16-18°C and
potential density about 25.1-25.4 to depth from about 150m to 380m.
The role of mesoscale eddies on the formation of NPSTMW are examined.
It is shown that by strengthening the vertical mixing process and
thus the ventilation process of isotherms of the permanent
thermocline, anticyclonic (warm) eddies help to the formation of
thicker NPSTMW than cyclonic (cold) ones.
|
Potential of Argo
data for detection and attribution of oceanic climate change
Richard A. Wood,
Helene T. Banks, Michael Vellinga and Sheila Stark
Hadley Centre for Climate
Prediction and Research,
Met Office,
Exeter, UK
Matthew Palmer
Southampton Oceanography Centre,
Southampton,
UK
richard.wood@metoffice.com
Argo was conceived as a long-term, sustained
observing system for the ocean. One of the benefits of such a system
will be the provision of long, quasi-homogeneous timeseries of
hydrographic data, with near-global coverage, which will fill the
huge gaps in our current knowledge of low frequncy variability and
trends in the ocean. But how will those timeseries be used to advance
our understanding of the climate system, and feed into
decision-making on global change?
We present results from three studies aimed at
identifying what types of statement may - and may not - be possible
in future based on 10 to 50 years of Argo data. The studies focus
on:
1. Water mass changes: are we likely to be able to make confident
statements about
detection (trends vs. internal
variability) and attribution (e.g anthropogenic vs. natural
forcing)? How long a timeseries are we likely to need?
2.
Global ocean heat content: is the proposed Argo spatial sampling
sufficient to
determine the heat content and its
interannual to decadal variability?
3. Atlantic
thermohaline circulation: can Argo data usefully supplement other
planned,
moored monitoring systems?
Our approach is to use simulations using the HadCM3
climate model to generate the type of synthetic 'observations' that
are likely to be gathered by Argo over the coming years. While the
model almost certainly does not capture all the behaviour of the real
world, and surprises are inevitable, our results demonstrate the
potential of the developing Argo dataset to answer some fundamental
questions in climate science.
|
Salinity change in the
southeastern Indian Ocean
Helen Phillips, Susan Wijffels and Ming Feng
CSIRO Marine
Research,
GPO
Box 1538
Hobart: 7001
TAS
Australia
helen.phillips@csiro.au
Nearly 4 years of Argo float data now exists in
the Indonesian Throughflow Region of the southeast Indian Ocean
(90°E-130°E, 25°S-5°S). These data are compared with
the high resolution Australian-region hydrographic climatology CARS
(CSIRO Atlas of Regional Seas).
Salinity during the period 1999-2003 is markedly
different than the climatology. Waters above 200 dbar, where
potential temperature is warmer than about 18°C, are consistently
fresher over the entire region by approximately 0.2 psu. The
freshening is greatest south of 15°S, south of the South
Equatorial Current (SEC); there is little zonal variation in the
extent of the freshening. Between 200 and 400 dbar ( theta~
10-18°C), float salinities are close to climatology except
between 14°S and 18°S where they are saltier than climatology
by up to 0.1 psu, possibly due to variation in the location of the
SEC. Below 400 dbar, ( theta< 10°C) there is weak freshening
of approximately 0.03 psu. The surface freshening covers the entire
period of the float record. During early 1998 to early 2001, the
year preceding and two years during the float record, the Southern
Oscillation Index was persistently positive, and rainfall in the
region was persistently higher than average, suggesting one possible
reason for the surface freshening.
|
Argo as an Aid to Environmental Monitoring and Assessment
- the example of the Gulf of Alaska.
Howard Freeland and Steve MacDonald
Department of Fisheries and
Oceans
Institute of
Ocean Sciences
Canada
FreelandHj@pac.dfo-mpo.gc.ca
The spring of 2002 saw an unusual climate anomaly
develop within the waters of the Gulf of Alaska. This anomaly was
characterised by rapid warming at the surface and an injection of a
large T/S anomaly between 80m to 150m depth. Much has already been
written about this anomaly, its development and origin, and some
descriptions of its impacts have been prepared. In the northern Gulf
of Alaska the anomalies resulted in a massive stabilisation of the
water column through the spring, summer and fall of 2002. By
February 2003 it was apparent that very little mixing had taken place
in the upper ocean and that this would be restricting the supply of
nutrients which potentially could be damaging to the productivity of
the marine ecosystem during the spring and summer of 2003. These
observations, largely based on results derived directly from the Argo
array formed a large part of ecosystem assessments conducted in early
2003.
This paper will show how the
unusual climate anomalies were observed by the Argo array, how these
affected the stratification of the upper water column and how these
observations were used to make contributions to the annual
environmental assessments. Finally, the paper will present some
preliminary results describing how the ecosystem actually behaved
during the biologically active periods in 2003.
|
The Bering Slope Current System Revisited
Gregory C. Johnson and
Phyllis J. Stabeno
NOAA/Pacific Marine Environmental Laboratory
7600 Sand Point Way
NE, Bldg. 3
Seattle, WA 98115
USA
Stephen C. Riser
School of Oceanography,
University of Washington,
Seattle,
Washington
USA
gjohnson@pmel.noaa.gov
Mean circulation and water properties within the
Aleutian Basin of the Bering Sea are investigated using hydrographic
and subsurface park pressure displacement data from a regional array
of 14 profiling CTD floats. After 10 days drifting at 1000 dbar each
float measures temperature and salinity profiles as it rises to the
surface, and then transmits these data via satellites which also make
several fixes of the float surface positions before it sinks again.
Every fourth cycle the floats sink from 1000 dbar to a 2000-dbar
target just prior to ascent to measure deeper profiles.
The 1000-dbar displacements
estimated from the float surface position fixes reveal a coherent few
cm s-1 northwestward flow along the northeasternboundary, the deep
signature of the Bering Slope Current. Mid-depth water property
distributions are consistent with cyclonic advection of warm water
from the south around the basin, eastward in the Aleutian North Slope
Current, and then northwestward in the Bering Slope Current.
Geostrophic transport estimates relative to 1000 dbar also show
cyclonic motion, although with significant noise, likely owing to the
influence of mesoscale eddies.The mean along-slope geostrophic
transport of the Bering Slope Current is determined between 0 and
1900 dbar relative to 1000 dbar and then combined with mean
along-slope velocities at 1000 dbar. The result is an absolute
geostrophic transport estimate with 95% confidence intervals for the
along-slope current offshore of the 1000-m isobath and between 0 to
1900 dbar, 5.8 (±1.7) x 10**6 m3 s-1.
|
Eddy-induced temperature anomalies in the Kuroshio
extension recirculation gyre from Argo, TMI and altimetry
measurements
Bo
Qiu, Shuiming Chen and Peter Hacker
Dept of Oceanography,
University of
Hawaii
1000
Pope Rd.
Honolulu, HI 96822
USA
bo@soest.hawaii.edu
The past decade has seen an unprecedented
advancement in satellite measurement of sea surface height (SSH; by
TOPEX/Poseidon, Jason-1, and ERS-1/2) and sea surface temperature
(SST; e.g., by TRMM Microwave Imager). While these measurements have
helped revealing many new features of the ocean circulation, their
dynamic interpretations are often hampered by lack of observational
data beneath the sea surface. The contemporaneous Argo measurements
provide us now with a unique opportunity to unravel the sea surface
signatures and their subsurface connections.
The recirculation gyre region south of the
Kuroshio Extension jet is abundant with energetic mesoscale eddies.
High-resolution satellite measurements reveal that warm (cold) SST
anomalies associated with the mesoscale eddies tend to located ~150km
to the west of high (low) SSH anomalies in this region. An
examination of the available Argo data indicates that this phase
misalignment is confined to the seasonal mixed layer (0-200 m depth).
Below the seasonal mixed layer, the SST anomalies are in-phase with
the SSH anomalies. The phase difference between the SST and SSH
anomalies is found to be caused by meridional temperature advection
associated with the mesoscale eddies and it contributes to the
northward eddy heat transport in the Kuroshio Extension recirculation
gyre region.
|
Distribution and variation
of the mixed layer in the western North Pacific observed by Argo
floats
Yuko
Ohno1, Taiyo Kobayashi2, Naoto Iwasaka1,2, Toshio Suga2
1 Tokyo University of
Mercantile Marine
Etchujima 2-1-6, Koto-ku,
Tokyo 135-8533
JAPAN
2 Frontier Observational Research System
for Global Change
yohno@ipc.tosho-u.ac.jp
In this study we describe the distributions and time
variations of the mixed layer measured by Argo floats which have been
deployed in the western North Pacific. Then its observed
characteristics are compared with those inferred from World Ocean
Atlas 1998 (WOA98). Profile data obtained by Argo floats in the
North Pacific from April 2000 to July 2003 are used. The mixed layer
depth (MLD) is defined as the depth at which potential density is
larger than that at the sea surface by 0.125kg/m3. The mixed layers
are developed most in February and March; its average depths are
about 130m in the analyzed region. The mixed layers deeper than 250m
are concentrated in the region south of the Kuroshio Extension.
During the boreal summer of June to August the mixed layers become
as shallow as 50m or less. The temporal and spatial variability of
the MLDs is very large in winter. The observed mixed layer tends to
be deeper than that from WOA98 in the subtropical region and to be
shallower in the subarctic region. Especially the observed MLDs in
March are deeper than those from WOA98 by up to 174m around 35°N,
145-155°E and are shallower by up to 233m around 40°N,
155-165°E. These results suggest that climatological MLDs
calculated from gridded data like WOA98 may be far from realistic in
some regions.
|
Estimating ocean velocity
fields from Argo and other data
W Brech Owens
Woods Hole Oceanographic Insititution
Woods
Hole
Ma
02543
USA
bowens@whoi.edu
Abstract not yet available
|
Intermediate level circulation in the southwestern part of
the Japan/East Sea
Young-Gyu Park,
Kyung-Hee Oh, Moon-Sik Suk and Kyung-Il Chang
Global Environment Research
Laboratory,
Korea
Ocean Research and Development Institute
Ansan,
P.O. Box 29,
Seoul 425-600,
Korea
ypark@kordi.re.kr
Using trajectory data from the subsurface floats
(PALACE and APEX) deployed into the Japan/East Sea for the past few
years, we were able to obtain a detailed intermediate level
circulation pattern over the south-western part of JES for the first
time. The flow in the region is largely controlled by the bottom
topography.
The main
features we have found are as follows:
1) a narrow current
circulating cyclonically along the Korean coast and Japanese
coast,
2) an inflow and outflow system to and from the Ulleung Basin through
UIG (Ulleung
Interplane Gap), and
3) an anticyclonic circulation around the
Korean Plateau.
Our results, which are consistent
with previous ones from current meter mooring (Chang et al. 2002) and
pressure gauges (Teague et al. 2003), have been obtained with less
effort and expenses but cover wider area than those previous
studies.
|
The absolute geostrophic
velocity field and wintertime convection in the Japan/East Sea
estimated from an array of profiling floats
Stephen Riser
School of Oceanography
University of
Washington
Washington 98195
USA
Mikhail Danchenkov
Far Eastern Regional Hydrometeorological
Research Institute
Vladivostok, Russia
Kuh Kim
Seoul National University
Seoul, Korea
Jong-Hwan Yoon
Kyushu University
Fukuoka, Japan
riser@ocean.washington.edu
The subpolar gyre in the Japan/East Sea is a region
of strong air-sea interaction, especially in winter, resulting in
intermediate and deep convection and ventilation. The relatively
high dissolved oxygen values in the subsurface waters of the Sea are
signatures of these winter processes. In order to study the
circulation and water mass properties of the subpolar gyre in the
Japan/East Sea in detail, an array of 37 profiling floats were
deployed by the US, with strong collaboration with Japan, Korea, and
Russia, during the summer of 1999.
These floats sampled the subpolar gyre of the
Japan/East Sea for over 3 years (some continue to operatate late in
2003). The profiles and deep velocities collected from these floats
have been used to construct seasonal maps of the absolute geostrophic
circulation of the Japan/East Sea at levels above 800 m. The
profiles reveal sites in the western Japan/East Sea where wintertime
convection occurs. A number of features revealed by the float
trajectories and profiles appear to be consistent with the
predictions of state-of-the-art numerical models of the Japan/East
Sea.
|
New elements of the Japan Sea oceanography found with the
use of profiling floats
Mikhail Danchenkov
FERHRI,
24 Fontannaya st,
Vladivostok 690600
RUSSIA
Steve Riser
University of Washington
Seattle
danchenk@vladivostok.ru
The Japan Sea is counted as "world ocean
in miniature" due to the fact that it contains all elements of
the world ocean oceanography.
4-years (1999-2003) work of 32 (after 190 cycles only 4
are still working ) deep floats-profilers (APEX and ) revealed deep
currents, features of water structure and their changes.
All floats drifted at 800 dB level (measurements were made
every 7 days in upper 800 dB layer).
Decoding and primary processing of data were made
in UW. Constant for water column salinity difference was input on
the base of salinity difference (climatic and measured) at lowest
level. It was unusually high (up to 0.5 psu) for two floats
only.
New elements of
regional oceanography were found after analysis of floats data:
- large-scale gyre in
deep basin and new current in its northern part;
- stationary eddy in its eastern
part.
The use of floats
measurements to addition of ship-based data allow to trace the Japan
Sea Deep Water formation in winter of 2001.
Heat content of 250-750 dB layer in winter
of 2001 year was minimal and just after it (in winter of 2002)-
maximal.
Features of
temporal variations of water characteristics gave interesting
conclusions too.
|
Global statistics of
inertial motions from Argo floats
Kuh Kim
241-318, Seoul National University,
San 56-1, Shilim-Dong,
Gwanak-Gu, Seoul
South Korea
Jong Jin Park
School of Earth Environmental
Sciences, Seoul National University, Korea
Brian A. King
Southampton Oceanography Centre,
Southampton, UK
Howard Freeland
Institute of Ocean Sciences, Sidney, British
Columbia, Canada
Stephen C. Riser
School of Oceanography, University of
Washington, Seattle, USA
kuhkim@ocean.snu.ac.kr
Statistics of inertial motion have been compiled in
the North Pacific, North Atlantic, the Indian Ocean, and the East
(Japan) Sea respectively using the surface trajectories of profiling
floats. The phase and amplitude of inertial motions and mean drift
velocity can be derived from a weighted function-fit to a set of
discrete Argos position fixes for each surface cycle. The statistical
distributions of the inertial speeds in the North Atlantic and the
East Sea are narrower than that in the Indian Ocean. The ranges of
inertial speeds which occupy 99% of all cycles are 0~41 cm/s in the
North Atlantic, 0~48cm/s in the East (Japan) Sea, and 0~81cm/s in the
Indian Ocean. The accuracy of the inertial speed can be below 5cm/s
if the drifting time at the surface is longer than 60% of local
inertial period and mean position error is less than 600m.
|
Response of the Arabian Sea to the summer monsoons of 2002
and 2003
P. N.
Vinayachandran
Centre for Atmospheric and Oceanic Sciences
Indian Institute of
Science,
Bangalore 560 012,
India.
vinay@caos.iisc.ernet.in
The Indian summer monsoon rainfall was 19% below
average during 2002 and 5% above average (so far) this year. The
relative strength of the monsoon winds showed considerable month to
month variability. The southwesterlies were stronger in June 2002
than June 2003 and weaker in July 2002 than July 2003. However, the
SST was warmer and the sea level higher during both June and July of
2003. Our knowledge about the response of the Arabian Sea to
contrasting monsoons is limited primarily to the surface features due
to the unavailability of sufficient subsurface observations. Argo
floats provide an opportunity to examine the surface and subsurface
changes to contrasting monsoons of 2002 and 2003.
Space time variations of the
Arabian Sea thermohaline structure in the upper ocean has been
examined using temperature and salinity profiles from Argo floats.
The float density increased from 2002 to 2003 but there are still
large gaps in the western and eastern parts of the Arabian Sea which
has restricted the present analysis to the central Arabian Sea. In
the northern Arabian Sea, the mixed layer deepened from the
presmonsoon conditions by about 10m during 2002 compared to about 10m
during 2003. In the south, both 2002 and 2003 showed a deepening of
about 20m. The thermocline response was markedly different between
2002 and 2003. In 2002, the thermocline deepened south of about 10N
and shallowed further north whereas in 2003 it deepened almost
everywhere. The results are being verified using complementary data
sets and ocean model outputs and the underlying mechanisms are being
explored.
Acknowledgments : This study was funded by the Indian
National Centre for Ocean Information Services (INCOIS), Department
of Ocean Development, Government of India.
|
Observations of the
Okhotsk Sea circulation and water masses using profiling floats
Keiichiro Ohshima
and Masaaki Wakatsuchi
Hokkaido University
Sapporo, Japan
Steve Riser
University of Washington
Seattle
WA 98195
USA
riser@ocean.washington.edu
Since mid-2000, 18 profiling floats have been
deployed in the Sea of Okhotsk in a program of collaboration between
Hokkaido University and Hokkaido Wakkanai Fisheries Experimental
Station (Japan), the University of Washington (USA), and the Far
East Regional Hydro-meteorolgical Research Institute (Russia). This
work was sponsored through CREST in Japan. The floats were targeted
for depths of 500 m, 750 m, and 1650 m. Trajectories of the floats
have revealed the extent of the cyclonic gyre in the central Okhotsk
basin and active mesoscale motions in the Kuril Basin. Some floats
have survived throughout the winter, under the sea ice, and
continued to function normally in spring after the ice melted; the
data from these floats is very useful for examining the time
evolution of the winter mixed layer under the ice. The seasonal heat
content in the upper portion of the Okhotsk Sea as measured by the
floats compares well with the surface heat flux. The heat budget
estimates provided by the floats suggest that the anomalously early
appearance of sea ice in the winter of 2000/2001 was caused by an
anomalously large loss of heat loss in the fall of 2000. The
freshwater budget associated with the ice formation/melting cycle has
also been examined from the profiling float data.
|
Argo and other observing systems - issues and
challenges
Uwe
Send
Institut für Meereskunde
Dusternbrooker Weg 20,
24105 Kiel
Germany
usend@ifm.uni-kiel.de
Abstract not yet available
|
Applications of Argo observations - an
exciting prospect
(provisional title)
Stan Wilson
NOAA NESDIS
Silver Spring, MD,
USA
Stan.Wilson@noaa.gov
Abstract not yet
available
|
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