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Titel |
Autonomous Studies of Coupled Physical-Biogeochemical Processes- Lessons from NAB08 and Prospects for the Future |
VerfasserIn |
Craig Lee, Eric D'Asaro, Mary Jane Perry |
Konferenz |
EGU General Assembly 2013
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 15 (2013) |
Datensatznummer |
250075294
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Zusammenfassung |
Motivated by the increasing application of autonomous sensors to physical, biological and
biogeochemical investigations at the submesoscale, we examine techniques developed during
the 2008 North Atlantic Bloom Experiment (NAB08), review successes, failures, and lessons
learned, and offer perspectives on how these approaches might evolve in response to
near-term shifts in scientific goals and technological advances. NAB08 exploited the
persistence of autonomous platforms coupled with the extensive capabilities of a ship-based
sampling program to investigate the patch-scale physics, biogeochemistry and community
dynamics of a spring phytoplankton bloom. Autonomous platforms (Seagliders
following a heavily-instrumented Lagrangian float) collected measurements in a
quasi-Lagrangian frame, beginning before bloom initiation and extending well
past its demise. This system of autonomous instruments resolved variability at the
patch scale while also providing the persistence needed to follow bloom evolution.
Biological and biogeochemical measurements were conducted from R/V Knorr
during the bloom. An aggressive protocol for sensor calibration and proxy building
bridged the ship-based and autonomous efforts, leveraging the intensive but sparse
ship-based measurements onto the much more numerous autonomous observations. The
combination of sampling in the patch-following frame, persistent, autonomous
surveys and focused, aggressive calibration and proxy building produced robust,
quantitative estimates of physical and biogeochemical processes. For example, budgets
of nitrate, dissolved oxygen and particulate organic carbon (POC) following the
patch were used to estimate net community production (NCP) and apparent POC
export. Net community production was 805 mmol C-
m-2 during the main bloom,
with apparent POC export of 564 mmol C-
m-2 and 282 mmol C-
m-2 lost due
to net respiration (70%) and apparent export (30%) on the day following bloom
termination. Thus, POC export of roughly 70% NCP occurred steadily throughout the
main bloom, while respiration, rather than sinking, drove the rapid drop in POC
at bloom termination. Sensor networks require proper intercalibration to support
quantitative use of the measurements, but calibration efforts become increasingly
difficult as the number of independent sensors grows. NAB08 offers a suitable model
for modest networks, but alternative approaches will be required for larger arrays. |
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