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| Titel |
Oxygen exchange and ice melt measured at the ice-water interface by eddy correlation |
| VerfasserIn |
M. H. Long, D. Koopmans, P. Berg, S. Rysgaard, R. N. Glud, D. H. Søgaard |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 6 ; Nr. 9, no. 6 (2012-06-04), S.1957-1967 |
| Datensatznummer |
250007111
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| Publikation (Nr.) |
 copernicus.org/bg-9-1957-2012.pdf |
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| Zusammenfassung |
| This study examined fluxes across the ice-water interface utilizing the eddy
correlation technique. Temperature eddy correlation systems were used to
determine rates of ice melting and freezing, and O2 eddy correlation
systems were used to examine O2 exchange rates driven by biological and
physical processes. The study was conducted below 0.7 m thick sea-ice in
mid-March 2010 in a southwest Greenland fjord and revealed low rates of ice
melt at a maximum of 0.80 mm d−1. The O2 flux associated with
release of O2 depleted melt water was less than 13 % of the average
daily O2 respiration rate. Ice melt and insufficient vertical turbulent
mixing due to low current velocities caused periodic stratification
immediately below the ice. This prevented the determination of fluxes 61 %
of the deployment time. These time intervals were identified by examining
the velocity and the linearity and stability of the cumulative flux. The
examination of unstratified conditions through vertical velocity and O2
spectra and their cospectra revealed characteristic fingerprints of
well-developed turbulence. From the measured O2 fluxes a
photosynthesis/irradiance curve was established by least-squares fitting.
This relation showed that light limitation of net photosynthesis began at
4.2 μmol photons m−2 s−1, and that algal communities were
well-adapted to low-light conditions as they were light saturated for 75 %
of the day during this early spring period. However, the sea-ice associated
microbial and algal community was net heterotrophic with a daily gross
primary production of 0.69 mmol O2 m−2 d−1 and a respiration
rate of −2.13 mmol O2 m−2 d−1 leading to a net
ecosystem metabolism of −1.45 mmol O2 m−2 d−1. This
application of the eddy correlation technique produced high temporal
resolution O2 fluxes and ice melt rates that were measured without
disturbing the in situ environmental conditions while integrating over an
area of approximately 50 m2 which incorporated the highly variable
activity and spatial distributions of sea-ice communities. |
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