Modeling Coastal Hypoxia

Modeling Coastal Hypoxia PDF

Author: Dubravko Justic

Publisher: Springer

Published: 2017-05-03

Total Pages: 433

ISBN-13: 331954571X

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This book provides a snapshot of representative modeling analyses of coastal hypoxia and its effects. Hypoxia refers to conditions in the water column where dissolved oxygen falls below levels that can support most metazoan marine life (i.e., 2 mg O2 l-1). The number of hypoxic zones has been increasing at an exponential rate since the 1960s; there are currently more than 600 documented hypoxic zones in the estuarine and coastal waters worldwide. Hypoxia develops as a synergistic product of many physical and biological factors that affect the balance of dissolved oxygen in seawater, including temperature, solar radiation, wind, freshwater discharge, nutrient supply, and the production and decay of organic matter. A number of modeling approaches have been increasingly used in hypoxia research, along with the more traditional observational and experimental studies. Modeling is necessary because of rapidly changing coastal circulation and stratification patterns that affect hypoxia, the large spatial extent over which hypoxia develops, and limitations on our capabilities to directly measure hypoxia over large spatial and temporal scales. This book consists of 15 chapters that are broadly organized around three main topics: (1) Modeling of the physical controls on hypoxia, (2) Modeling of biogeochemical controls and feedbacks, and, (3) Modeling of the ecological effects of hypoxia. The final chapter is a synthesis chapter that draws generalities from the earlier chapters, highlights strengths and weaknesses of the current state-of-the-art modeling, and offers recommendations on future directions.

Coastal Hypoxia on the Texas Shelf

Coastal Hypoxia on the Texas Shelf PDF

Author: Ruth Louise Mullins

Publisher:

Published: 2013

Total Pages:

ISBN-13:

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A combination of in situ sampling and real-time ocean observations was used to investigate the processes responsible for the formation and the areal extent of Texas coastal hypoxia from 2002 to 2011. In situ sampling, real-time mooring and buoy observations, and multivariate statistical modeling were used to investigate the physical processes driving hypoxia formation. Geostatistical interpolation (ordinary kriging) models were tested to compare the differences in annual hypoxia area on the Texas shelf. Results from these two sections were integrated into recommendations for improving federal hypoxia monitoring and mitigation strategies in the northwestern Gulf of Mexico. Winds, currents, temperature, salinity, and dissolved oxygen records revealed the annual, seasonal, and daily variability of hypoxia formation on the Texas coast from 2009 to 2011. Hypoxic events occurred from late May to late October lasting from hours to weeks. Hypoxia formation was either the result of salinity stratification, associated with the freshening of surface waters by the advection of Mississippi-Atchafalaya River freshwater westward or the wind- and current-driven upcoast or downcoast flow of Brazos River discharge. Records from 2010 and 2011 showed the variability and frequency of stratification development differs on the north and south Texas shelf. Multivariate linear model results showed contributing factors on the north Texas shelf vary annually and that primary factors for hypoxia development are near-surface current speeds and salinity-driven stratification. Interpolation models resulted in three size categories for hypoxia area: small (100 - 1,000 km2), moderate (1,001 - 3,000 km2), and large (3,001+ km2). Moderate years include 2002, 2004, and 2007 and a large year was 2008. There was no increase in hypoxic area from years 2002 to 2011, but years 2007 and 2008 resulted in a hypoxic area over 5,000 km2, which is the federally mandated hypoxia reduction target for the northwestern Gulf of Mexico. Geostatistical interpolators represent and predict the structure and spatial extent of the hypoxic area on the Texas shelf by accounting for the anisotropy of physical processes on the Texas shelf. Geostatistical interpolation models are preferred to deterministic models for developing and improving federal hypoxia monitoring and mitigation strategies on the northwestern Gulf of Mexico shelf. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/149543

Ocean Modeling in an Eddying Regime

Ocean Modeling in an Eddying Regime PDF

Author: Matthew W. Hecht

Publisher: John Wiley & Sons

Published: 2013-04-30

Total Pages: 654

ISBN-13: 1118671996

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Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 177. This monograph is the first to survey progress in realistic simulation in a strongly eddying regime made possible by recent increases in computational capability. Its contributors comprise the leading researchers in this important and constantly evolving field. Divided into three parts Oceanographic Processes and Regimes: Fundamental Questions Ocean Dynamics and State: From Regional to Global Scale, and Modeling at the Mesoscale: State of the Art and Future Directions The volume details important advances in physical oceanography based on eddy resolving ocean modeling. It captures the state of the art and discusses issues that ocean modelers must consider in order to effectively contribute to advancing current knowledge, from subtleties of the underlying fluid dynamical equations to meaningful comparison with oceanographic observations and leading-edge model development. It summarizes many of the important results which have emerged from ocean modeling in an eddying regime, for those interested broadly in the physical science. More technical topics are intended to address the concerns of those actively working in the field.

Eutrophication in Coastal Ecosystems

Eutrophication in Coastal Ecosystems PDF

Author: Jesper H. Andersen

Publisher: Springer

Published: 2012-03-14

Total Pages: 264

ISBN-13: 9789400730366

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Coastal eutrophication has been and still remains an important issue for the scientific community. Despite many efforts to mitigate coastal eutrophication, the problems associated with eutrophication are still far from being solved. This book focusses on the most recent scientific results in relation to specific eutrophication issues, e.g. definition(s) and causes; nutrient loads, cycling and limitation; reference conditions, primary effects and secondary effects; trend reversal (oligotrophication), as well as links to other pressures (climate change and top/down control). It also focusses on monitoring and modelling of coastal eutrophication, and adaptive and science-based nutrient management strategies. The book is based on selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, held 20-23 June 2006 in Nyborg, Denmark.

Hypoxia in the Northern Gulf of Mexico

Hypoxia in the Northern Gulf of Mexico PDF

Author: Virginia H. Dale

Publisher: Springer Science & Business Media

Published: 2010-04-12

Total Pages: 334

ISBN-13: 0387896864

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Since 1985, scientists have been documenting a hypoxic zone in the Gulf of Mexico each year. The hypoxic zone, an area of low dissolved oxygen that cannot s- port marine life, generally manifests itself in the spring. Since marine species either die or ee the hypoxic zone, the spread of hypoxia reduces the available habitat for marine species, which are important for the ecosystem as well as commercial and recreational shing in the Gulf. Since 2001, the hypoxic zone has averaged 2 1 16,500 km during its peak summer months , an area slightly larger than the state 2 2 of Connecticut, and ranged from a low of 8,500 km to a high of 22,000 km . To address the hypoxia problem, the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force (or Task Force) was formed to bring together represen- tives from federal agencies, states, and tribes to consider options for responding to hypoxia. The Task Force asked the White House Of ce of Science and Technology Policy to conduct a scienti c assessment of the causes and consequences of Gulf hypoxia through its Committee on Environment and Natural Resources (CENR).

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