GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L01603, doi:10.1029/2011GL050078, 2012
Underwater glider observations and modeling of an abrupt mixing
event in the upper ocean
Simón Ruiz,1 Lionel Renault,2 Bartolomé Garau,2 and Joaquín Tintoré1,2
Received 20 October 2011; revised 1 December 2011; accepted 2 December 2011; published 13 January 2012.
[1] An abrupt mixing event in the upper ocean is investigated in the Northwestern Mediterranean Sea using gliders, a
new ocean monitoring technology, combined with regional
atmospheric model outputs and mooring data. Intense winds
(up to 20 m s 1) and buoyancy forcing during December
2009 induced strong vertical mixing of the upper ocean layer
in the Balearic Sea. High-resolution data from a coastal glider
reveal a surface cooling of near 2 °C and the deepening of
the Mixed Layer Depth (MLD) by more than 40 meters in
the center of the basin. Comparisons between glider and
ship-emulated sections of hydrographic profiles show that the
glider data make visible the small-scale spatial variability of
the MLD. The heat content released to the atmosphere by the
upper ocean during this mixing event exceeds 1000 W m 2.
A simulation from the Weather Research and Forecasting
model reports values consistent with these observations.
Additionally the atmospheric numerical simulation shows the
development and evolution of a cyclone located south of the
Balearic Islands. This cyclone is likely to be responsible for
the wind intensification and the consequent air-sea energy
exchanges that occurred in the study area during this period.
Citation: Ruiz, S., L. Renault, B. Garau, and J. Tintoré (2012),
Underwater glider observations and modeling of an abrupt mixing
event in the upper ocean, Geophys. Res. Lett., 39, L01603,
doi:10.1029/2011GL050078.
1. Introduction
[2] Characterization of the spatial and temporal variability
of the Mixed Layer Depth (MLD) is essential to developing
a better understanding of the exchanges of air-sea fluxes
(wind stress, heat and fresh water) that occur daily at the
ocean surface. The MLD perturbs the sea surface temperature, which has direct implications for atmosphere and ocean
heat budgets [Roads et al., 2003]. Different criteria to estimate the MLD have been studied with successful results
[de Boyer Montégut et al., 2004; Lorbacher et al., 2006;
Chu and Fan, 2010], and de Boyer Montégu et al. [2004]
developed a climatology (2° resolution) of the MLD for
the global ocean. In the Mediterranean Sea, D’Ortenzio et al.
[2005] produced a climatology (0.5° resolution) that reproduces the MLD associated with the main features of the
surface circulation and deep-water formation areas.
[3] For shorter space and time scales the MLD is less well
studied, as this requires in-situ experiments under specific
1
Instituto Mediterraneo de Estudios Avanzados, IMEDEA (CSIC-UIB),
Esporles, Spain.
2
Balearic Islands Coastal Observing and Forecasting System, SOCIB,
Palma de Mallorca, Spain.
Copyright 2012 by the American Geophysical Union.
0094-8276/12/2011GL050078
(often extreme) weather conditions to characterize the high
resolution horizontal and vertical extension of the MLD
associated with atmosphere-ocean mesoscale processes. For
example, Weller (1991) carried out an exhaustive study on
air-sea interactions in the Atlantic Ocean combining mooring, drifters, SeaSoar and ADCP data. In the Northwestern
Mediterranean Sea the exchanges of energy between mesoscale atmospheric fronts and the upper ocean are especially
significant during the winter period when northwesterly
winds are dominant [Jansá, 1987; Flamant, 2003], however
studies to investigate the MLD under the influence of strong
winds in this area are scarce and based on mooring data
[Marty et al., 2002], upward looking ADCPs [Schott and
Leaman, 1991] or coastal weather stations, model outputs
and ship CTD observations [Mertens and Schott, 1998]. The
hydrographic observations from these previous studies have
usually been collected by performing CTD casts around the
moorings or by defining transects with large spatial sampling intervals (5 to 10 km). In this context, the objective of
this study is to investigate the upper ocean response to
intense winds and buoyancy forcing in the Western Mediterranean using high resolution glider observations, in situ
buoys and an atmospheric numerical simulation. A major
advantage of using gliders is the acquisition of high spatial
resolution hydrographic data (0.5 km) in wintertime, when
CTD sampling from ship surveys is complicated by frequent
adverse weather conditions. First we characterize the MLD
before and after the mixing event, estimating the heat fluxes
exchanges from the glider data. These results are compared
with those obtained from ship-emulated sections of hydrographic profiles to assess the impact of using the higher
resolution glider data. Then, an atmospheric numerical
simulation is considered, to show the heat flux exchange and
the potential mechanism responsible for the ocean mixing
event. Finally, a discussion of the results and concluding
remarks are given.
2. In-Situ Data and Atmospheric Model
2.1. Glider Data
[4] In the framework of the IMEDEA observational program for autonomous underwater vehicles in the Balearic
Sea (Western Mediterranean), a glider mission was carried
out between 9 to 20 December 2009 (Figure 1a). As in
previous missions (see details in work by Ruiz et al. [2009]
and Bouffard et al. [2010]), the data acquisition strategy
consisted of performing a section almost perpendicular to
the Balearic and Northern Currents, that flow along the north
coast of Mallorca and along the Iberian Peninsula respectively [La Violette et al., 1990]. 700 CTD profiles were
collected, between surface and 180 m, covering a total track
length (go and return) of about 270 km. The glider data
L01603
1 of 7
L01603
RUIZ ET AL.: ABRUPT MIXING IN THE UPPER OCEAN
L01603
data at 5 km horizontal resolution and giving rise to a dataset
we have called “ship-emulated” data.
2.2. Moorings
[7] Averaged hourly data from the network of buoys
operated by Puertos de Estado (Spanish Port Authority) are
used for the study at 4 locations (Figure 1a). These buoys
provide information on atmospheric and oceanographic
parameters, near Mallorca (Mallorca buoy) where the glider
mission started and finished, and also in the vicinity of
the end point reached by the glider near the mainland
(Tarragona buoy). Two additional buoys, located to the north
(Begur buoy) and south (Valencia buoy) of the glider mission, are also used. The specific variables analyzed from the
buoys are wind speed and direction, sea level atmospheric
pressure, sea surface height and air temperature at 2 m.
Figure 1. (a) Map of the study area in the Northwestern
Mediterranean Sea. Glider tracks (magenta and yellow lines)
are indicated. Black dots correspond to locations of the 4 permanent oceanographic/meteorological deep-buoys. (b) Model
domains for the WRF model implementation.
processing included the thermal lag correction for the
un-pumped CTD unit, standard on Slocum gliders [Garau
et al., 2011]. Final profiles have a 0.5 km horizontal alongtrack resolution and were averaged in the vertical to 1 db.
[5] To compute the MLD different approaches are available [Kara et al., 2000; Lorbacher et al., 2006]. Here, the
MLD that is commonly defined as the layer between surface
and the depth where hydrographic measurements (temperature, salinity and density) are quasi-constant, is computed
following de Boyer Montégut et al. [2004]. The specific criteria considered for the computation is T(10 m) - T(h) =
0.2 °C, where T(h) is temperature at depth h and T(10 m) is
temperature at 10 m depth, as the first data available from
the glider for all the profiles is at 10 m depth.
[6] To assess the impact of high-resolution glider data on
the estimation of the MLD, a second dataset at lower resolution has been produced; through sub-sampling the glider
2.3. Atmospheric Model
[8] The Weather Research and Forecasting (WRF) Model
(v3.00 [Skamarock and Klemp, 2007] was implemented in a
nested 2 grid configuration (Figure 1b): the largest domain,
with a horizontal resolution of 30 km, approximately covers
the western Mediterranean, the inner domain, with a horizontal resolution of 7.5 km, covers the area 35.4 N–43.2 N,
1.9W–7.6E, which includes the Balearic Islands. The coarser
grid reproduces the large-scale features, which force the
local dynamics in grid 2 at each time step. The simulation is
performed using a two-way nesting technique, starting at
00:00 UTC 1st November 2009 and lasting 2 months. Fortysix vertical levels are employed, more closely distributed
in the upper levels. Initial and boundary conditions are
provided by the NCEP FNL analysis (http://dss.ucar.edu/
datasets/ds083.2). A full set of parameterization schemes
are included in the model for microphysics, convection,
turbulence, soil processes, boundary layer processes, and
radiation. In the model configuration used here, the following
parameterization schemes have been selected: the WRF
Single-Moment 5-class scheme microphysics [Skamarock
et al., 2008], the Kain cumulus parameterization on the
coarser grid [Skamarock et al., 2008], the Rapid Radiative
Transfer Model (RRTM) for long-wave radiation (based on
work by Mlawer et al. [1997]), the Dudhia [1989] scheme
for shortwave radiation, and the Noah Land Surface Model
[Skamarock et al., 2008]. The planet boundary (PBL)
scheme used is the Mellor-Yamada-Janjic scheme [Janjic,
2002]. SST forcing was derived from a high resolution
(5 km) daily SST product [Marullo et al., 2007]. Fluxes
data from WRF have been interpolated to the exact glider
positions using cubic splines.
3. Results
3.1. Oceanographic Conditions
[9] During the glider mission, relatively cold (15 °C) and
salty (>38 PSU) Mediterranean waters occupied the upper
100 m near the Spanish mainland coast, while on the island
side, relatively warm (17 °C) and fresh (<38 PSU) of recent
Atlantic origin was found in a shallower layer of about 60 m
(Figures 2a and 2b). Dynamics of the area is dominated by
two main currents [La Violette et al., 1990], that have been
intensively studied using gliders and altimetry in the last
5 years [Bouffard et al., 2010] and that can be briefly
described as the Northern Current flowing southwestward
2 of 7
L01603
RUIZ ET AL.: ABRUPT MIXING IN THE UPPER OCEAN
L01603
Figure 2. Vertical sections of high-resolution temperature (a, b), density (c, d) and Brunt-Väisälä frequency (e, f ) obtained
from glider (left) ‘go’ and (right) ‘return.’ The black line on the density field corresponds to MLD.
along the Spanish coast and the Balearic Current that progress northeastward along the Balearic coast. Intense mesoscale variability associated to this general pattern has been
also reported [Tintoré et al., 1990].
[10] Density fields and MLD are shown in Figures 2c and
2d. For the ‘go’ transect the MLD is found at 40 m in the
center of the basin, which is in good agreement with the low
resolution (1 degree) climatology values [de Boyer Montégut
et al., 2004]. At the ends of the transect, associated with the
along-coast currents, the MLD is located at deeper levels
(about 90 m). The climatology does not have sufficient
resolution to detect this spatial variability at the edges of the
domain (not shown). The stability of the water column has
been also illustrated through computing the Brunt-Väisälä
frequency (Figures 2e and 2f), which confirms that maximum values are associated with the pycnocline, which is
3 of 7
L01603
RUIZ ET AL.: ABRUPT MIXING IN THE UPPER OCEAN
L01603
shallower in the center of the basin. The equilibrium of this
upper ocean layer, as sampled by the glider during the first
4 days, was abruptly modified during the second part of the
mission (glider ‘return’ transect from mainland to Mallorca).
On 13th December, atmospheric pressure started to drop off
drastically, decreasing from 1025 hPa to values near 995 hPa
by 15th December (Figure 3a). In this short period, wind
velocity increased from less than 5 m s 1 to maximum
values of 20 m s 1, inducing significant wave heights of up
to 6 m (Figure 3b). Under these adverse sea conditions,
gathering hydrographic data by ship would be a difficult and
risky task. However, the autonomous underwater platform
was able to successfully accomplish the transit from the
mainland to Mallorca.
[11] The abrupt change in atmospheric conditions induces
an immediate response in the upper ocean. Potential temperature at the surface ocean diminished from 16 °C to about
14.5 °C and the momentum and buoyancy forcing causes a
sinking of the MLD. While the pycnocline is maintained at
almost the same depth at the boundaries of the study area, it
sinks by about 40 meters in the middle of the basin. A closer
inspection of the thermohaline structure reveals additional
changes in the southern part of the domain, near the north of
Mallorca coast. In this area the structure located between the
surface and about 70 m, characterized by relative warm and
fresh water (typical of the Balearic Current, Pinot et al.
[2002]), was split in two parts; a main core near the coast
and a small-detached filament centered at about 40°N
(Figure 2b). After the mixing event, the maximum value of
N2 at the pycnocline is still of the order 50 (radians s 1)2 but
now it is located at 80 m depth at both the ends and at the
center of the basin (Figure 2f). The heat content of the upper
ocean layer has been estimated for the glider data (go and
return tracks) and the difference reveals loss of about
1100 W m 2 in the center of the basin (Figure 3c).
[12] A first look to the glider and ship-emulated sections
of hydrographic profiles indicates that, as expected, the
large-scale pattern in both samplings is very similar
(Figures 2a and 2b and auxiliary material).1 However, in the
glider data it is possible to determine the small-scale spatial
variability of the MLD, which has an impact on the estimation of the upper ocean heat content. The smoothed MLD
estimated from the ship-emulated dataset in the south part of
the domain, between latitude 39.85 N and 40.1 N, shows a
substantial underestimation (about 20%) of the heat content
(Figure 3c) when compared with the value estimated from
the glider data.
Figure 3. (a, b)Atmospheric pressure and significant sea
surface height measured during glider mission. Gray shadow
colour indicates coincident period between glider and buoy
measurements. (c) Heat content as estimated from glider
and ship-emulated data. Units are indicated on the y axes.
The mean value of the heat capacity used in the computation
is 3.97 103 J/kg °C.
3.2. Local Forcing and Atmospheric Model Outputs
[13] The 4 buoys, located in the Northwestern Mediterranean area, gathered the atmospheric conditions for the whole
period of the glider mission. Comparisons between the wind
speed and pressure from the buoys and model simulation
show good agreement (auxiliary material), demonstrating
that the chosen model parameterization accurately reproduces the local atmospheric variability and allows us to use
the regional atmospheric simulation to study the air-sea
interaction mechanisms forcing the glider observed ocean
mixing event.
1
Auxiliary materials are available in the HTML. doi:10.1029/
2011GL050078.
4 of 7
L01603
RUIZ ET AL.: ABRUPT MIXING IN THE UPPER OCEAN
L01603
Figure 4. (a) Sensible and (b) latent heat from the WRF model. (c) Sea surface wind (vectors), atmospheric pressure (white
isolines) and air temperature at 2 m (color scale) from the WRF model for 2009/12/14 at 16:00. (d) Mean sea level pressure
and RMS for the period 14-16 December 2011. Storm track from the model simulation is overplotted. Units are indicated on
the y axes.
[14] Heat fluxes (sensible and latent) from the WRF
model reveal a significant loss of energy from the ocean
on 14th December. Latent heat fluxes reach maximum
values of about -750 W m 2 while the sensible heat
released to the atmosphere is of the order of -400 W m 2
(Figures 4a and 4b). The heat balance given by the WRF
simulation is about -1200 W m 2, which is in good
agreement with the estimation from the in-situ glider
observations (see Figure 3c).
[15] The WRF output also allows us to understand the
important role of the latent heat during this event. From
13th December onwards, the atmospheric simulation reveals
the arrival of cold air and intense northwesterly winds. The
atmospheric pressure from the model shows a core of low
pressure (around 990 hPa) located south of the Balearic
Islands at the same time that the glider was performing
the ‘return’ sampling towards Mallorca (14th December).
Intense winds of up to 25 m s 1 (Figure 4c) crossed the study
area cooling the surface layer and producing the mixing of
the upper ocean layer, as described above, and a net surface
heat loss across the Balearic Sea.
[16] In addition, the potential origin of the atmospheric
forcing has been investigated using the WRF model. Mean
sea level pressure and RMS for the 14-16 December period
is shown in Figure 4d. The core of the cyclone is detected
near the Moroccan coast by November and it then advanced
northeast towards the south of the Balearic Islands, overlapping with the period of glider sampling. By the end of
December the storm had progressed southeast, towards the
African coast, where it finally dissipated (Figure 4d).
4. Discussion and Concluding Remarks
[17] We have characterized an air-sea interaction in the
Western Mediterranean using new technologies such as gliders; regional atmospheric model outputs and data from
buoys are also used. From 9th to 13th December 2009, the
high-resolution hydrographic data reported the characteristic
pattern of the thermohaline structure in the Balearic Sea. The
situation changed drastically from 13th December onwards.
Simultaneous to intense winds and buoyancy forcing a
glider recorded, at high spatial resolution, the strong vertical mixing event of the upper ocean layer. Surface ocean
water suffered a sudden cooling of near 2 °C and the MLD
deepened by more than 40 m in the center of the basin.
Comparisons between glider and ship-emulated sampling
demonstrate some of the advantages of using these
5 of 7
L01603
RUIZ ET AL.: ABRUPT MIXING IN THE UPPER OCEAN
autonomous platforms. Gliders can provide a more detailed
picture of the spatial variability of the MLD depth and
therefore a more accurate estimation of the ocean heat
content is possible. However, gliders also have some limitations, such as the low speed of displacement [Rudnick
and Cole, 2011], which affect the synopticity of the data.
In our study, as the event lasted several days, the 4 day
glider transect is viewed as sufficiently synoptic to accurately represent the significant changes in MLD that
occurred during this period.
[18] The amount of heat content released to the atmosphere by the upper ocean during the mixing event was
estimated from the glider data and found to exceed
1000 W m 2. The simulation of heat fluxes from the WRF
model reports values consistent with these observations. It is
also worth noting that similar values have been reported in
the area under equivalent wind conditions [Mertens and
Schott, 1998; Schott and Leaman, 1991]. The slight differences between glider and model fluxes (less than
100 W m 2) could be explained by the lateral advection
(which should be estimated from accurate ADCP velocities
not available for this study) and errors in the SST forcing
used by the WRF model [Marullo et al., 2007]. A regional
atmospheric model simulation carried out for the glider
sampling period reveals the development and evolution of
an atmospheric cyclone located south of the Balearic
Islands. This cyclone appears to be responsible for the
intensification of winds from the north and the consequent
increase in air-sea exchanges in the basin. Campins et al.
[2000] and Lebeaupin Brossier and Drobinski [2009]
have reported similar wintertime events, characterized by
intense, cold and dry winds from Northern Europe.
[19] This study demonstrates that autonomous underwater platforms represent a valuable new tool for investigating the air-sea interactions in extreme conditions, as
they can be operated remotely and collect data at a high
horizontal resolution (0.5 km). Moreover, glider data
could contribute to validate atmospheric model products
such as heat fluxes. In the coming years we plan to
maintain and increase our glider activities in the Western
Mediterranean and to learn more about the capabilities
and benefits of these platforms in studying the upper
ocean.
[20] Acknowledgments. This work has been partially supported by
Gliderbal and MyOcean projects, funded by the Govern Balear
(AAEE0051/08) and the European Commission respectively. We would
like to acknowledge the support of the technicians from the TMOOS
Department at IMEDEA (CSIC-UIB), for their collaboration during the
glider preparation, launch and recovery, and of Puertos del Estado in providing the mooring data. Emma Heslop and two anonymous reviewers provided valuable comments that helped improving the manuscript. The FNL
data (http://dss.ucar.edu/ds083) are from the Research Data Archive
(RDA) maintained by the Computational and Information Systems Laboratory (CISL) at the National Center for Atmospheric Research (NCAR).
NCAR is sponsored by the National Science Foundation (NSF).
[21] The Editor thanks two anonymous reviewers for their assistance in
evaluating this paper.
References
Bouffard, J., A. Pascual, S. Ruiz, Y. Faugère, and J. Tintoré (2010), Coastal
and mesoscale dynamics characterization using altimetry and gliders: A
case study in the Balearic Sea, J. Geophys. Res., 115, C10029,
doi:10.1029/2009JC006087.
Campins, J., A. Genoves, A. Jansá, J. A. Guijarro, and C. Ramis (2000), A
catalogue and a classification of surface cyclones for the western
L01603
Mediterranean, Int. J. Climatol., 20, 969–984, doi:10.1002/1097-0088
(200007)20:9<969::AID-JOC519>3.0.CO;2-4.
Chu, P. C., and C. Fan (2010), Optimal linear fitting for objective determination of ocean mixed layer depth from glider profiles, J. Atmos. Oceanic
Technol., 27, 1893–1898, doi:10.1175/2010JTECHO804.1.
D’Ortenzio, F., D. Iudicone, C. de Boyer Montegut, P. Testor, D. Antoine,
S. Marullo, R. Santoleri, and G. Madec (2005), Seasonal variability of the
mixed layer depth in the Mediterranean Sea as derived from in situ profiles, Geophys. Res. Lett., 32, L12605, doi:10.1029/2005GL022463.
de Boyer Montégut, C., G. Mardec, A. S. Fischer, A. Lazar, and D.
Iudicone (2004), Mixed layer depth over the global ocean: An examination of profile data and a profile based climatology, J. Geophys.
Res., 109, C12003, doi:10.1029/2004JC002378.
Dudhia, J. (1989), Numerical study of convection observed during the winter monsoon experiment using a mesoscale two-dimensional model, J.
Atmos. Sci., 46, 3077–3107, doi:10.1175/1520-0469(1989)046<3077:
NSOCOD>2.0.CO;2.
Flamant, C. (2003), Alpine lee cyclogenesis influence on air-sea heat
exchanges and marine atmospheric boundary layer thermodynamics over
the western Mediterranean during a Tramontane/Mistral event, J. Geophys. Res., 108(C2), 8057, doi:10.1029/2001JC001040.
Garau, B., S. Ruiz, G. W. Zang, E. Heslop, J. Kerfoot, A. Pascual, and J.
Tintoré (2011), Thermal lag correction on Slocum CTD glider data, J.
Atmos. Oceanic Technol., 28, 1065–1071, doi:10.1175/JTECH-D-1005030.1.
Janjic, Z. I. (2002), Nonsingular implementation of the Mellor-Yamada
level 2.5 scheme in the NCEP Meso model, Off. Note 437, 61 pp., Natl.
Cent. for Environ. Predict., Camp Springs, Md.
Jansá, A. (1987), Distribution of the mistral: A satellite observation,
Meteorol. Atmos. Phys., 36, 201–214, doi:10.1007/BF01045149.
Kara, A., A. Rochford, and H. Hurlbutt (2000), Mixed layer depth variability and barrier layer formation over the North Pacific Ocean, J. Geophys.
Res., 105(C7), 16,783–16,801, doi:10.1029/2000JC900071.
La Violette, P. E., J. Tintoré, and J. Font (1990), The surface circulation of
the Balearic Sea, J. Geophys. Res., 95, 1559–1568, doi:10.1029/
JC095iC02p01559.
Lebeaupin Brossier, B., and C. P. Drobinski (2009), Numerical highresolution air-sea coupling over the Gulf of Lions during two Tramontane/
Mistral events, J. Geophys. Res., 114, D10110, doi:10.1029/
2008JD011601.
Lorbacher, K., D. Dommenget, P. P. Niiler, and A. Kohl (2006), Ocean
mixed layer depth: A subsurface proxy of ocean-atmosphere variability,
J. Geophys. Res., 111, C07010, doi:10.1029/2003JC002157.
Marty, J.-C., J. Chiavérini, M.-D. Pizay, and B. Avril (2002), Seasonal and
interannual dynamics of nutrients and phytoplankton pigments in the
western Mediterranean Sea at the DYFAMED time-series station
(1991–1999), Deep Sea Res., Part II, 49, 1965–1985, doi:10.1016/
S0967-0645(02)00022-X.
Marullo, S., B. Nardelli, M. Guarracino, and R. Santoleri (2007), Observing
the Mediterranean Sea from space: 21 years of Pathfinder-AVHRR sea
surface temperatures (1985 to 2005). Re-analysis and validation, Ocean
Sci., 3, 299–310.
Mertens, C., and F. Schott (1998), Interannual variability of deep-water
formation in the northwestern Mediterranean, J. Phys. Oceanogr., 28,
1410–1424.
Mlawer, E. J., S. J. Taubman, P. D. Brown, M. J. Iacono, and S. A. Clough
(1997), Radiative transfer for inhomogeneous atmosphere: RRTM, a validated correlated-k model for the longwave, J. Geophys. Res., 102,
16,663–16,682, doi:10.1029/97JD00237.
Pinot, J.-M., J. L. López-Jurado, and M. Riera (2002), The CANALES
experiment (1996–98). Interannual, seasonal, and mesoscale variability
of the circulation in the Balearic Channels, Prog. Oceanogr., 55, 335–
370, doi:10.1016/S0079-6611(02)00139-8.
Roads, J., et al. (2003), GCIP water and energy budget synthesis (WEBS),
J. Geophys. Res., 108(D16), 8609, doi:10.1029/2002JD002583.
Rudnick, D. L., and S. T. Cole (2011), On sampling the ocean using
underwater gliders, J. Geophys. Res., 116, C08010, doi:10.1029/
2010JC006849.
Ruiz, S., A. Pascual, B. Garau, Y. Faugere, A. Alvarez, and J. Tintoré
(2009), Mesoscale dynamics of the Balearic Front, integrating glider,
ship and satellite data, J. Mar. Syst., 78, S3–S16, doi:10.1016/j.
jmarsys.2009.01.007.
Schott, F., and K. Leaman (1991), Observations with moored acoustic
Doppler current profilers in the convection regime in the Golfe du
Lion, J. Phys. Oceanogr., 21, 558–574, doi:10.1175/1520-0485
(1991)021<0558:OWMADC>2.0.CO;2.
Skamarock, W. C., and J. B. Klemp (2007), A time-split nonhydrostatic
atmospheric model for research and NWP applications, J. Comput. Phys.,
227, 3465–3485.
Skamarock, W. C., et al. (2008) A description of the Advanced Research
WRF version 3, Tech. Note NCAR/TN-475+STR, Natl. Cent. for Atmos.
6 of 7
L01603
RUIZ ET AL.: ABRUPT MIXING IN THE UPPER OCEAN
Res., Boulder, Colo. [Available at http://www.mmm.ucar.edu/wrf/users/
docs/arw_v3.pdf.]
Tintoré, J., D. P. Wang, and P. E. La Violette (1990), Eddies and thermohaline intrusions of the shelf/slope front off northeast Spain, J. Geophys.
Res., 95, 1627–1633, doi:10.1029/JC095iC02p01627.
Weller, R. A. (1991), Overview of the Frontal Air-Sea Interaction Experiment (FASINEX): A study of air-sea interaction in a region of strong oce-
L01603
anic gradients, J. Geophys. Res., 96(C5), 8501–8516, doi:10.1029/
90JC01868.
B. Garau and L. Renault, Balearic Islands Coastal Observing and
Forecasting System, SOCIB, Parcbit, Palma de Mallorca, E-07190, Spain.
S. Ruiz and J. Tintoré, Instituto Mediterraneo de Estudios Avanzados,
IMEDEA (CSIC-UIB), C/Miquel Marquès, 21, Esporles, E-07190, Spain.
([email protected])
7 of 7