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| Titel |
NIOZ high-resolution moored temperature observations: benefits and new challenges. |
| VerfasserIn |
Andrea Cimatoribus, Louis Gostiaux, Frédéric Cyr, Hans van Haren |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250121653
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| Publikation (Nr.) |
 EGU/EGU2016-446.pdf |
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| Zusammenfassung |
| The Royal Netherlands Institute for Sea Research has been developing for several years a
family of temperature sensors (NIOZ1 to NIOZ5). In the latest iterations of this project, these
instruments are precise (10−3 K or better), have a very low noise level (below 10−3 K), are
relatively fast (sampling rate of 1Hz) and can measure for extended periods of time (several
months). Being also compact and lightweight, several thermistors can be attached on a
single line at a fine vertical spacing (20cm or more). When mounted on a cable, the
instruments are all synchronised to a single clock, thus providing simultaneous
measurements throughout the depth range of the mooring (usually in the order of
100m). Recently, the instruments have also been deployed in a group of 5 lines
approximately 5m apart from each other, providing a unique view on the three-dimensional
temperature field. After almost 10 years of successful deployments at sea, we try to
draw some conclusions from this effort, from the scientific and technical point of
view.
This observational system provides temperature measurements with vertical spatial
resolution comparable to that of microstructure profilers, but in comparison to ship-borne
systems it offers some distinctive features:
providing instantaneous measurements throughout the mooring, observations of
waves and overturning structures are not influenced by the time delay between
measurements at different depths;
the very low noise level and high precision enables the study of the deep, weakly
stratified ocean;
by using a heavy ballast at the bottom and a high net buoyancy at the top of the
mooring, Eulerian measurements are effectively obtained;
continuous, high sampling rate Eulerian measurements enable to assess the
intermittent, sporadic nature of turbulence and wave activity in the ocean;
the large range of time scales included in the observations (100 − 106 s) allows
to study a large portion of the turbulence inertial range, the full internal wave
spectrum, modulation by submesoscale and mesoscale activity and seasonal
variations.
These features have been exploited for characterising the internal wave spectrum in the
open ocean, for evaluating turbulence parameters above seamounts, and to characterise
the statistics of temperature fluctuations. Main results include the observational
demonstration of extreme inhomogeneity in space and intermittency in time of turbulence,
and evidence of the importance of convective activity within strong geophysical
turbulence.
The data collected challenges the classical methods of turbulence parameters estimation
in the ocean. Classical “Thorpe scale” methods have been adapted to the particular
characteristics of the data, and efforts have been made to adapt other methods, providing
higher detail on the vertical and temporal modulation of turbulence. The large datasets have
also enabled the application on observational data of analysis methods previously used on
laboratory data alone. |
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