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The Effect of Baroclinic Processes on Marine Primary Production /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	The Effect of Baroclinic Processes on Marine Primary Production // Jasen Robert Jacobsen.
作者:	Jacobsen, Jasen Robert,
面頁冊數:	1 electronic resource (165 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-07, Section: B.
Contained By:	Dissertations Abstracts International86-07B.
標題:	Physical oceanography. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31764532
ISBN:	9798302852717

The Effect of Baroclinic Processes on Marine Primary Production /
Jacobsen, Jasen Robert,

The Effect of Baroclinic Processes on Marine Primary Production /Jasen Robert Jacobsen. - 1 electronic resource (165 pages)

Source: Dissertations Abstracts International, Volume: 86-07, Section: B.

The base of the marine ecosystem is supported by marine microalgae known as phytoplankton. Phytoplankton rely on the combination of light and nutrients to survive. Plankton and nutrients move with water parcels, and fluid motion dictates the light environment essential to most primary production. In geophysical systems, fluid motion is often described as barotropic or baroclinic. Barotropic motion corresponds to the depth-averaged flow, and is largely independent of stratification. When lateral changes in density occur in a stratified fluid, motion deviates from the depth depth-averaged flow and is referred to as baroclinic motion. Many different types of baroclinic processes exist in the ocean, each one affecting light and nutrient availability for primary production. This dissertation uses idealized numerical models to explore three different baroclinic systems and how each affects light and nutrient availability for primary production in the ocean.Chapter One investigates the primary production response to the generation of internal tides by fluctuating tidal flow over varying bathymetry. This process concentrates baroclinic wave energy into a coherent structure known as a tidal beam. The tidal beam leads to a large displacement of phytoplankton through a light field that varies exponentially with depth, leading to more light available for primary production. At the same time, the tidal beam elevates the average position of isopycnal surfaces, carrying nutrients and phytoplankton into the euphotic zone. Analysis of Lagrangian parcels that move with ocean currents and representing phytoplankton shows that the effect on nutrient availability enhances primary production more than the increase in light.Chapter Two turns to a different type of baroclinic wave known as an Island Trapped Wave (ITW). ITWs are analogous to coastal trapped waves where an island acts as a waveguide boundary. In the case considered here, an ITW that travels around the island in a 24-hour period is excited as a resonant response to a land-sea breeze with a 24-hour period. As part of the resonant response, ITWs affect light and nutrient availability for primary production. Nonlinear processes associated with the ITW increase nutrient concentrations in the euphotic zone through elevated advective and diffusive flux divergences. With regard to light availability, a diel light cycle causes a dipole structure of primary production across the island with the largest enhancement of primary production occurring where the upwelling phase of the ITW arrives at noon. To quantify this effect, phytoplankton biomass, nutrient, and light are decomposed into their mean states and fluctuations around their means. Primary production associated with the mean state is the larger, indicating that the enhancement of primary production occurs due to state adjustment of the nutrient field rather than light fluctuations. However, the correlation of light and nutrient fluctuations further increases this enhancement by an additional 30%.Chapter Three considers yet another baroclinic process, wind-driven coastal upwelling, and compares the primary production response in two- and three-dimensional idealized numerical models. Coastal upwelling is driven by offshore surface Ekman transport which removes surface water from the coast and replaces it with nutrient-rich waters from below, often causing large phytoplankton blooms. The depth of the upwelled water determines the nutrient content, with deeper waters having higher nutrient concentrations. The geometry of the continental shelf affects the upwelling source depth and thus magnitude of the primary production response. Two-dimensional upwelling theory and numerical modeling studies predict that steeper shelves source water from deeper depths compared to wider shelves. In three-dimensions, changes in alongshore shelf width also adjust upwelling source depth. Deeper, higher nutrient water is transported cross-shelf with the bottom boundary when a shelf widens in the downwind direction. Results from this chapter show that the primary production response is laterally displaced downstream from bottom boundary layer transport by alongshore transport. Primary production is elevated up to 100 km downwind of the change in shelf width after ten days of upwelling. Conversely, where the shelf narrows in the direction of the wind, the reduced transport along the bottom boundary causes less nutrients to be delivered to the euphotic zone and lower levels of primary production. In both cases, changes in shelf width in the alongshore direction locally affect upwelling source depth, and the resulting elevated or diminished nutrient concentrations are then delivered to the euphotic zone downwind of the change in shelf width.In summary, this dissertation examines how baroclinic processes affect light and nutrient availability differently depending on the context of the generating mechanism. These baroclinic processes primarily affect phytoplankton growth through vertical nutrient transport; however, some processes can affect light availability as well, highlighting the diversity of biological responses to baroclinic motion.

English

ISBN: 9798302852717Subjects--Topical Terms:

3168433
Physical oceanography.
Subjects--Index Terms:

Coastal upwelling

The Effect of Baroclinic Processes on Marine Primary Production /
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520 $a The base of the marine ecosystem is supported by marine microalgae known as phytoplankton. Phytoplankton rely on the combination of light and nutrients to survive. Plankton and nutrients move with water parcels, and fluid motion dictates the light environment essential to most primary production. In geophysical systems, fluid motion is often described as barotropic or baroclinic. Barotropic motion corresponds to the depth-averaged flow, and is largely independent of stratification. When lateral changes in density occur in a stratified fluid, motion deviates from the depth depth-averaged flow and is referred to as baroclinic motion. Many different types of baroclinic processes exist in the ocean, each one affecting light and nutrient availability for primary production. This dissertation uses idealized numerical models to explore three different baroclinic systems and how each affects light and nutrient availability for primary production in the ocean.Chapter One investigates the primary production response to the generation of internal tides by fluctuating tidal flow over varying bathymetry. This process concentrates baroclinic wave energy into a coherent structure known as a tidal beam. The tidal beam leads to a large displacement of phytoplankton through a light field that varies exponentially with depth, leading to more light available for primary production. At the same time, the tidal beam elevates the average position of isopycnal surfaces, carrying nutrients and phytoplankton into the euphotic zone. Analysis of Lagrangian parcels that move with ocean currents and representing phytoplankton shows that the effect on nutrient availability enhances primary production more than the increase in light.Chapter Two turns to a different type of baroclinic wave known as an Island Trapped Wave (ITW). ITWs are analogous to coastal trapped waves where an island acts as a waveguide boundary. In the case considered here, an ITW that travels around the island in a 24-hour period is excited as a resonant response to a land-sea breeze with a 24-hour period. As part of the resonant response, ITWs affect light and nutrient availability for primary production. Nonlinear processes associated with the ITW increase nutrient concentrations in the euphotic zone through elevated advective and diffusive flux divergences. With regard to light availability, a diel light cycle causes a dipole structure of primary production across the island with the largest enhancement of primary production occurring where the upwelling phase of the ITW arrives at noon. To quantify this effect, phytoplankton biomass, nutrient, and light are decomposed into their mean states and fluctuations around their means. Primary production associated with the mean state is the larger, indicating that the enhancement of primary production occurs due to state adjustment of the nutrient field rather than light fluctuations. However, the correlation of light and nutrient fluctuations further increases this enhancement by an additional 30%.Chapter Three considers yet another baroclinic process, wind-driven coastal upwelling, and compares the primary production response in two- and three-dimensional idealized numerical models. Coastal upwelling is driven by offshore surface Ekman transport which removes surface water from the coast and replaces it with nutrient-rich waters from below, often causing large phytoplankton blooms. The depth of the upwelled water determines the nutrient content, with deeper waters having higher nutrient concentrations. The geometry of the continental shelf affects the upwelling source depth and thus magnitude of the primary production response. Two-dimensional upwelling theory and numerical modeling studies predict that steeper shelves source water from deeper depths compared to wider shelves. In three-dimensions, changes in alongshore shelf width also adjust upwelling source depth. Deeper, higher nutrient water is transported cross-shelf with the bottom boundary when a shelf widens in the downwind direction. Results from this chapter show that the primary production response is laterally displaced downstream from bottom boundary layer transport by alongshore transport. Primary production is elevated up to 100 km downwind of the change in shelf width after ten days of upwelling. Conversely, where the shelf narrows in the direction of the wind, the reduced transport along the bottom boundary causes less nutrients to be delivered to the euphotic zone and lower levels of primary production. In both cases, changes in shelf width in the alongshore direction locally affect upwelling source depth, and the resulting elevated or diminished nutrient concentrations are then delivered to the euphotic zone downwind of the change in shelf width.In summary, this dissertation examines how baroclinic processes affect light and nutrient availability differently depending on the context of the generating mechanism. These baroclinic processes primarily affect phytoplankton growth through vertical nutrient transport; however, some processes can affect light availability as well, highlighting the diversity of biological responses to baroclinic motion.
546 $a English
590 $a School code: 0036
650 4 $a Physical oceanography. $3 3168433
650 4 $a Biological oceanography. $3 2122748
650 4 $a Marine geology. $3 3173821
653 $a Coastal upwelling
653 $a Internal tides
653 $a Island trapped waves
653 $a Primary production
690 $a 0415
690 $a 0416
690 $a 0556
710 2 $a University of California, Santa Cruz. $b Ocean Sciences. $e degree granting institution. $3 3816884
720 1 $a Edwards, Christopher A. $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 86-07B.
790 $a 0036
791 $a Ph.D.
792 $a 2024
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31764532