Date of Award

Winter 2004

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean & Earth Sciences

Committee Director

Eileen E. Hofmann

Committee Member

Larry P. Atkinson

Committee Member

Chester Grosch

Committee Member

John M. Klinck

Abstract

This study presents results from models that are designed to simulate the underwater light field, to simulate phytoplankton primary production, and to estimate the fate of phytoplankton carbon in continental shelf waters of the west Antarctic Peninsula (WAP) and Ross Sea. Simulation of the underwater light field required derivation of new coefficient sets for power function-type cloud cover correction algorithms, which were found to be influenced by multiple reflections between the bottom of clouds and the surface. The coefficient sets indicate that the spectral effect of clouds on the properties of the surface irradiance was spectrally-neutral for wavelengths greater than 330 nm. The regional dependency of the newly-derived coefficient sets provide an approach for developing general cloud cover correction algorithms for Antarctic coastal waters. Next, a bio-optical production model that was forced with the simulated surface irradiance fields, corrected for cloud conditions, and the simulated underwater light field was used to estimate primary production and subsequent carbon flux at several sites along the western Antarctic Peninsula and in the Ross Sea. The parameterizations used in the bio-optical production model included depth-dependent photosynthesis-irradiance relationships that involved different patterns of diel variation. Sensitivity studies showed simulated primary production estimates were increased by up to 130% when photosynthetic parameters with a diel periodicity were used in the production model. Inclusion of spectrally-resolved quantum yields increased primary production estimates by as much as 300%, relative to a reference simulation that used constant parameters. The fate of newly-produced phytoplankton carbon obtained from simulations for the WAP and Ross Sea was investigated using budget calculations that included the effects of grazing, advection, and sinking. For the western Antarctic Peninsula region, horizontal (across-shelf component) advection is the dominant process controlling primary production carbon in the outer-shelf areas in all seasons. Depending on season, advection can remove up to 40% of the phytoplankton carbon in the shelf waters. Grazing, however, is as important as across-shelf advection during the summer and can be an order of magnitude greater in inner shelf waters than in mid- and outer-shelf waters.

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DOI

10.25777/0fah-rk06

ISBN

9780496977277

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