Salinity Profiling Autonomous
LAgrangian Circlulation Explorer
(S-PALACE) floats are new tools for acquiring temperature and salinity
profiles in remote or inhospitable regions. These autonomous
floats have the advantage that once deployed, no ships or people are
required on site to obtain the measurements. The data is collected by the
float and telemetered back to land via satellite link.
Floats can last as long as 150 profiles or more, giving a 4-5 year
lifetime on a two-week cycle. By analysing the data as it is returned,
we can learn more about the characteristics of the upper ocean's heat and
salt content as well as its circulation. S-PALACE data are expected
to be important inputs to predictive ocean-atmosphere coupled models in
the future, as greater numbers are deployed in the global ocean.
The schematic above shows the operational cycle of an upward profiling S-PALACE float. After the float is deployed, it sinks to the depth for which it was ballasted and drifts with the currents at that depth for a pre-programmed period of time. It then ascends to the surface measuring temperature and conductivity. The profile data is averaged into pressure bins and encoded for compression to minimize bandwith. Once at the surface, the float transmits the encoded profile data to passing satellites for a period of 24 hours. Finally the float descends again to its ballast depth for another drifting interval. Some of the newer floats are programmed to collect data as they descend, and then actively maintain a target depth while they drift- these are called "parking" floats.
The data transmitted to the satellites by the floats is collected by Service ARGOS, who send it daily to our computers for processing. The conversion and storage process done to PALACE floats at WHOI is automated. We recieve the data from ARGOS via email, and then programs are run automatically at pre-set times every day to unpack the data, store it, and generate figures that are displayed on the ACCE pages of this web page. A diagram of the automated data processing system shows more detail of how the system operates. The error checking is accomplished by looking at the profiles and deciding whether there are any problems. In the future, this may become part of the automated process.
Current Experimental programs
These smart floats have been deployed as part of the Atlantic Circulation and Climate Experiment (ACCE), funded by the National Science Foundation, Division of Ocean Sciences. This a large program with several components, from direct observations from instruments like the S-PALACE floats to modeling studies that attempt to make sense of the incoming data. The S-PALACE data collected by WHOI investigators is accessible below.
ACCE Year 1 floats (Schmitt) - 10 deployed on 6N in 7/97, 1 still operational ACCE Year 2 floats (Schmitt) - 13 deployed on 11N in 10/98, none still operational 6 deployed on 13.5N in 10/98, none still operational 11 deployed on 16N in 10/98, none still operational Greenland Sea (Owens)- 40 deployed in 11-12/96 35 Launched in 10-11/97
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