Coasts Under Changing Climate Observations And Modeling

The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides policymakers with regular assessments of the scientific basis of human-induced climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the most comprehensive and up-to-date assessment of the observed and projected changes to the ocean and cryosphere and their associated impacts and risks, with a focus on resilience, risk management response options, and adaptation measures, considering both their potential and limitations. It brings together knowledge on physical and biogeochemical changes, the interplay with ecosystem changes, and the implications for human communities. It serves policymakers, decision makers, stakeholders, and all interested parties with unbiased, up-to-date, policy-relevant information. This title is also available as Open Access on Cambridge Core.

Tide gauges show that global sea level has risen about 7 inches during the 20th century, and recent satellite data show that the rate of sea-level rise is accelerating. As Earth warms, sea levels are rising mainly because ocean water expands as it warms; and water from melting glaciers and ice sheets is flowing into the ocean. Sea-level rise poses enormous risks to the valuable infrastructure, development, and wetlands that line much of the 1,600 mile shoreline of California, Oregon, and Washington. As those states seek to incorporate projections of sea-level rise into coastal planning, they asked the National Research Council to make independent projections of sea-level rise along their coasts for the years 2030, 2050, and 2100, taking into account regional factors that affect sea level. Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future explains that sea level along the U.S. west coast is affected by a number of factors. These include: climate patterns such as the El Niño, effects from the melting of modern and ancient ice sheets, and geologic processes, such as plate tectonics. Regional projections for California, Oregon, and Washington show a sharp distinction at Cape Mendocino in northern California. South of that point, sea-level rise is expected to be very close to global projections. However, projections are lower north of Cape Mendocino because the land is being pushed upward as the ocean plate moves under the continental plate along the Cascadia Subduction Zone. However, an earthquake magnitude 8 or larger, which occurs in the region every few hundred to 1,000 years, would cause the land to drop and sea level to suddenly rise.

Coastal oceans as highly productive components of the global ocean play crucial roles in global carbon cycle and climate change. The wide continental shelf off US east coast is a typical coastal environment that serves as a buffer zone between human activities and open oceans. This thesis investigates the dispersal pattern of Hudson River outflow in the New York Bight (NYB). It applies adjoint sensitivity, Incremental Strong Constraint 4D Variational Data Assimilation (IS4DVAR) and representer-based optimal observation to integrate coastal ocean modeling and observation capabilities. Firstly, analysis of a 2-year model simulation identifies three freshwater pathways: along (i) the New Jersey coast, (ii) the Long Island coast, and (iii) a Mid-shelf Pathway. It is shown that the New Jersey coast Pathway dominates winter months and the Mid-shelf Pathway summer months. It is also demonstrated that wind is the primary force for spreading freshwater into mid- and outer-shelf and presence of the Hudson Valley strengthens freshwater recirculation in the New York Apex area. Secondly, the Constituent-oriented Age and Residence time Theory is implemented to simulate the age and residence time of the Hudson River plume. Analysis shows strong seasonality of surface mean age and residence time consistent with seasonal variation of the circulation. Time series analysis shows that spatial and temporal variations of the time scales in NYB are largely buoyancy- and wind-driven. Thirdly, adjoint sensitivity analysis applied on the New Jersey inner shelf identifies water sources and quantitatively compares the contributions of different variables to a chosen oceanic process. Fourthly, IS4DVAR is used to assimilate observational data collected by all instrument types during spring 2006. It reduces the model-observation misfit by 60% and improves forecast of temperature, salinity and velocity. Finally, a representer-based optimal observation system is applied to identify the optimal sampling locations for predicting salt transport within the Hudson Shelf Valley. The system is then used to compare the influence area of existing observations. This work prototypes the integration of observation and modeling in a coastal environment and demonstrates the use of traditional and variational tools to reveal the physical processes in a shelf region.

The ocean is an integral component of the Earth's climate system. It covers about 70% of the Earth's surface and acts as its primary reservoir of heat and carbon, absorbing over 90% of the surplus heat and about 30% of the carbon dioxide associated with human activities, and receiving close to 100% of fresh water lost from land ice. With the accumulation of greenhouse gases in the atmosphere, notably carbon dioxide from fossil fuel combustion, the Earth's climate is now changing more rapidly than at any time since the advent of human societies. Society will increasingly face complex decisions about how to mitigate the adverse impacts of climate change such as droughts, sea-level rise, ocean acidification, species loss, changes to growing seasons, and stronger and possibly more frequent storms. Observations play a foundational role in documenting the state and variability of components of the climate system and facilitating climate prediction and scenario development. Regular and consistent collection of ocean observations over decades to centuries would monitor the Earth's main reservoirs of heat, carbon dioxide, and water and provides a critical record of long-term change and variability over multiple time scales. Sustained high-quality observations are also needed to test and improve climate models, which provide insights into the future climate system. Sustaining Ocean Observations to Understand Future Changes in Earth's Climate considers processes for identifying priority ocean observations that will improve understanding of the Earth's climate processes, and the challenges associated with sustaining these observations over long timeframes.

Low-lying coastal areas are susceptible to multiple flooding pathways from seawater, groundwater, and stormwater sources. Focusing on Imperial Beach California, USA, this research studies the vulnerability of coastal stormwater and wastewater systems to compound impacts of changing climate [i.e., Sea-Level Rise (SLR), groundwater shoaling, and precipitation intensification], the capability of decentralized water infrastructure in flood mitigation, and their adoptability by the community. After presenting the background information and research goals in Chapter 1, Chapter 2 evaluates compound flooding of the stormdrain system under a changing climate. Here, the obtained results for current and high sea-level conditions are presented (SLR = 0 and 2 m). The result illustrates that seawater may intrude into 2/3 of the stormdrain system length by a 2 m rise in current sea level. SLR consequences can be exacerbated by GroundWater Infiltration (GWI) such that the flooding volume may increase six-fold with 0.25% porosity systemwide and impact areas kilometers away from the coastline. Chapter 3 shows that defect flows currently increase hydraulic loading on the sewer system by 21% and 49% in dry- and wet-weather conditions, respectively. These numbers can be elevated to 84% and 120% at SLR = 2 m placing ~ $3 M cost on the system every year. The excess hydraulic loading also increases the potential of sanitary sewer overflows (i.e., exposing the community and environment to raw sewage pollution). Finally, by involving structural, hydrological, and hydraulic criteria, a holistic approach is presented to prioritize sewer rehabilitation. Chapter 4 first analyzes a social survey, whose results show that homeowners are more likely to adopt decentralized infrastructure. In addition, gardeners with the intention of reducing water usage in their yards can be targeted as the most prevalent adopters. Moreover, appropriate outreach activities are essential for enhancing public awareness in areas at the future risk of flooding. The engineering model outputs reveal that for a system with 0.25% porosity working under SLR = 0 m and a 1-year rainfall, the flood volume may decrease 56%-99% after implementing an RB system and adding an RG system. Although the RB system implementation can reduce the flood volume only by 24% at future conditions (SLR = 2 m and 25% increase in rainfall intensity), this value can be improved to 77% by adding an RG system. Additionally, the value of harvested rainwater over the lifetime of the RB system is estimated to be $60+ M while its cost will be $4- M. The RG system is also estimated to cost $15 M and occupy 2.4% of the city area.

Understanding Sea-Level Rise and Variability identifies the major impacts of sea-level rise, presents up-to-date assessments of past sea-level change, thoroughly explores all of the factors contributing to sea-level rise, and explores how sea-level extreme events might change. It identifies what is known in each area and what research and observations are required to reduce the uncertainties in our understanding of sea-level rise so that more reliable future projections can be made. A synthesis of findings provides a concise summary of past, present and future sea-level rise and its impacts on society. Key Features: Book includes contributions from a range of international sea level experts Multidisciplinary Four color throughout Describes the limits of our understanding of this crucial issue as well as pointing to directions for future research The book is for everyone interested in sea-level rise and its impacts, including policy makers, research funders, scientists, students, coastal managers and engineers. Additional resources for this book can be found at: http://www.wiley.com/go/church/sealevel.