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CMR SailBuoy deployment in the Northern Gulf of Mexico

Authors:
Lars Robert Hole at Norwegian Meteorological Institute
Lars Robert Hole
Mahmud Hasan Ghani
Mahmud Hasan Ghani
Mahmud Hasan Ghani
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Ilker Fer
Ilker Fer
Ilker Fer
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Villy H. Kourafalou at University of Miami
Villy H. Kourafalou
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Abstract

An experimental deployment of a new type of unmanned vessel is presented. The Christian Michelsen Research SailBuoy, a remotely-controlled surface vehicle, sampled near-surface properties during a two-month mission in the northern Gulf of Mexico in March – May, 2013. The vessel speed over ground was 42 ± 30 cm s-1 with a maximum of 180 cm s-1. During the 62 days of the mission, the SailBuoy covered a total range of approximately 400 km in both meridional and zonal directions, with a cumulative total distance of approximately 2400 km. Three parameters were recorded: sea surface temperature, conductivity, and dissolved oxygen.
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Abstract
Background
Methods Results
Conclusion
Hole et al., Deep-C GoM SailBuoy Experiment
CMR SailBuoy deployment in the Northern Gulf of Mexico
Lars R. Hole a*, Mahmud Hasan Ghani a,b, Ilker Fer b,c , Vassiliki H. Kourafalou d, Nicolas Wienders e, HeeSook Kang d, Kyla Drushka f, David Peddie c
a Norwegian Meteorological Institute, b Geophysical Institute, University of Bergen, Norway, c Christian Michelsen Research AS, Norway d University of
Miami/RSMAS Miami, e Florida State University, f Applied Physics Laboratory, University of Washington. * lrh@met.no
An experimental deployment of a new type of unmanned
vessel is presented. The Christian Michelsen Research
SailBuoy, a remotely-controlled surface vehicle, sampled
near-surface properties during a two-month mission in the
northern Gulf of Mexico in March – May, 2013. The vessel
speed over ground was 42 ± 30 cm s-1 with a maximum of
180 cm s-1. During the 62 days of the mission, the SailBuoy
covered a total range of approximately 400 km in both
meridional and zonal directions, with a cumulative total
distance of approximately 2400 km. Three parameters were
recorded: sea surface temperature, conductivity, and
dissolved oxygen.
Near surface properties, such as the sea surface
temperature (SST), and sea surface salinity (SSS) play a
crucial role in controlling the exchange between the ocean
and the atmosphere, as well as in influencing the weather
and large scale ocean and atmospheric circulation. Near-
surface dissolved oxygen concentration is a component that
responds to both physical changes as well as biological
changes.
Being 100% wind driven and using battery power only for
automatic tacking, the CMR SailBuoy system is capable of
carrying out long missions for up to 6 months.
It can both receive navigational instructions and transmit
data in real time via 2-way Iridium communication. A full
array of sensors can be used for applications in
oceanography, meteorology, marine mammal monitoring,
algae surveys, oil tracking, and wave measurements.
Length: 2.0 m.
Displacement: 60 kg.
Payload: 15 kg / 60 dm3.
Figure 4. Ground-tracks of the Aquarius satellite colored
by salinity observed during the study period (straight,
slanted lines) and the SailBuoy track, colored by its
measured salinity. For the coastal region (within 100 km of
the coast), the SailBuoy track is plotted in black and the
Aquarius data are not included. (b) salinity measured by
the SailBuoy and by Aquarius: Level 3 Aquarius data were
extracted at 87W, 28N and Level 2 data were extracted
along the SailBuoy path. The vertical dashed line
indicates the time at which the SailBuoy moved offshore
of the coastal region [2].
[1] Schiller, R. V., & Kourafalou, V. H. (2010). Modeling river plume
dynamics with the HYbrid Coordinate Ocean Model. Ocean
Modelling, 33(1), 101-117.
[2] M. Hasan Ghani, L. R. Hole, I. Fer, V. H. Kourafalou, N. Wienders, H.
Kang, K. Drushka and D. Peddie. TheSailBuoy remotely-controlled
unmanned vessel: measurements of near surface temperature, salinity
andoxygen concentration in the Northern Gulf of Mexico. Methods in
Oceanography, 2014. DOI 10.1016/j.mio.2014.08.001.
Figure 1: The CMR SailBuoy.
More details: www.sailbuoy.no
and www.deep-c.org/sailbuoy .
Figure 2: Maps with the SailBuoy track showing (a) velocity
vectors (every 7th data point), b) sea surface temperature
[oC], c) salinity [Practical Salinity Units - PSU], and d) oxygen
concentration [mg/l].
Figure 3: SailBuoy SSS on top of the Northern GoM nested
model [1].
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The SailBuoy remotely-controlled unmanned vessel: Measurements of near surface temperature, salinity and oxygen concentration in the Northern Gulf of Mexico
Article
Full-text available
  • Sep 2014
An experimental deployment of a new type of unmanned vessel is presented. The Christian Michelsen Research SailBuoy, a remotely-controlled surface vehicle, sampled near-surface properties during a two-month mission in the northern Gulf of Mexico in March–May, 2013. Averaged over the entire deployment, the vessel speed over ground was 42±30cm s−1 (±± one standard deviation) with a maximum of 180cm s−1. During the 62 days of the mission, the SailBuoy covered a total range of approximately 400 km in both meridional and zonal directions, with a cumulative total distance of approximately 2400 km. Three parameters were recorded: sea surface temperature, conductivity, and dissolved oxygen. Observed surface temperature and salinity records are compared with remote sensing data and the salinity fields from a regional ocean modeling system, respectively. The absolute difference between remote sensing data to surface temperature is on an average approximately 0.5 °C. The comparison with the full Gulf of Mexico and the nested Northern Gulf of Mexico HYCOM models demonstrates the validity and usefulness of SailBuoy measurements and the instrument’s utility in evaluating fields produced by ocean models having different attributes. The potential of the SailBuoy for mapping a large-scale river plume, which would be challenging or costly with conventional ship surveys and/or remote sensing, is demonstrated.
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Modeling river plume dynamics with the HYbrid Coordinate Ocean Model
Article
  • Dec 2010
  • OCEAN MODEL
The dynamics of large-scale river plumes are investigated in idealized numerical experiments using the HYbrid Coordinate Ocean Model (HYCOM). The focus of this study is to address how the development and structure of a buoyant plume are affected by the outflow properties, as impacted by processes within the estuary and at the point of discharge to the coastal basin. Changes in the outflow properties involved vertical and horizontal redistribution of the river inflow and enhanced vertical mixing inside an idealized estuary. The development of the buoyant plume was evaluated in a rectangular, f-plane basin with flat and sloping bottom conditions and in the absence of other external forcing. The general behavior of a mid-latitude river plume was reproduced, with the development of a surface anticyclonic bulge off the estuary mouth and a surface along-shore coastal current which flows in the direction of Kelvin wave propagation (“downstream”); the momentum balance was predominantly geostrophic. Conditions within the estuary and the outflow properties at the river mouth (where observed profiles may be available) greatly impacted the fate of riverine waters. In flat bottom conditions, larger mixing at the freshwater source enhanced the estuarine gravitational circulation, promoting larger upward entrainment and stronger outflow velocities. Although the overall geostrophic balance was maintained, estuarine mixing led to an asymmetry of the currents reaching the river mouth and to a sharp anticyclonic veering within the estuary, resulting in reduced upstream flow and enhanced downstream coastal current. These patterns were altered when the plumes evolved in the presence of a bottom slope. The anticyclonic veering of the buoyant outflow was suppressed, the offshore intrusion decreased and the recirculating bulge was displaced upstream. The sloping bottom impacts were accompanied by enhanced transport and increased downstream extent of the coastal current in most cases. No major changes in the general properties and especially the vertical structure of the plumes were observed when the vertical coordinates were changed from cartesian–isopycnal, to sigma or to sigma–isopycnal. The findings offer a benchmark for coastal studies with HYCOM, where plume dynamics should be examined in tandem with additional circulation forcing mechanisms, resulting in transitions of the vertical coordinate system that are dictated by the prevailing dynamics.
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