Significant sea level rise is expected for the foreseeable future, but the physical science of sea level rise and related climatic changes remains incomplete, making specific projections highly uncertain at this time. Moreover, place-specific social and ecological understanding of vulnerability and adaptation potential in coastal regions is severely lacking. Decision makers and other stakeholders should assume that changing scientific understanding as well as environmental and societal conditions will require considerable policy flexibility and make for potentially difficult tradeoffs. Thus, an adaptive risk management approach is indicated (see Box 3.1 and NRC, 2010b). Key research advances that would assist in improving both understanding and decision making include the following:
Reduce the scientific uncertainties associated with land-ice changes. Comprehensive, simultaneous, and sustained measurements of ice mass and volume changes and ice velocities are needed, along with measurements of ice thickness and bed conditions, both to quantify the current contributions of ice sheets to sea level rise and to constrain and inform ice sheet model development for future assessments. These measurements, which include satellite, aircraft, and in situ observations, need to overlap for several decades in order to enable the unambiguous isolation of ice melt, ice dynamics, snow accumulation, and thermal expansion. Equally important are investments in improving ice sheet process models that capture ice dynamics as well as interactions with the ocean and the ice bed. Efforts are already under way to improve modeling capabilities in these critical areas, but fully coupled ice-ocean-land models will ultimately be needed to reliably assess ice sheet stability, and considerable work remains to develop and validate such models—especially given the relatively small number of qualified researchers currently working in this area. Sustained observations and analysis programs are also needed for improving understanding and projections of glaciers and ice caps. Finally, additional paleoclimate data from ice cores, corals, and ocean sediments would be valuable for testing models and improving our understanding of the impacts of sea level rise.
Improve understanding of ocean dynamics and regional rates of sea level rise. Direct, long-term monitoring of sea level and related oceanographic properties via tide gauges, ocean altimetry measurements from satellites, and an expanded network of in situ measurements of temperature and salinity through the full depth of the ocean water column are needed to quantify the rate and spatial variability of sea level change and to understand the ocean dynamics that control global and local rates of sea level rise. A better understanding of the dependence of ocean heat uptake on vertical mixing and the abrupt change in polar reflectivity that will follow the loss of summer sea ice in the Arctic are some of the most critical improvements needed in ocean and Earth system models. In addition, oceanographic, geodetic, and coastal models are needed to predict the rate and spatial dynamics of ocean thermal expansion, sea level rise, and coastal inundation. The need for regionally specific information creates additional challenges. For example, coastal inundation models require better bathymetric data in the coastal seas, improved elevation data on land, the inclusion of wave and spillover effects, better data on precipitation rates and stream flows, ways of dealing with storm-driven sediment transport, and the ability to include the effects of built structures on coastal wind stress patterns.
Develop tools and approaches for understanding and predicting the vulnerability to, and impacts of, sea level rise on coastal ecosystems and coastal infrastructure, as well as for translating this understanding into decision-relevant information. The impacts of sea level rise on wetlands, coral reefs, marine fisheries, and estuarine bays and rivers need to be evaluated in concert with the impacts associated with increasing levels of CO2 in the atmosphere and oceans, increasing nutrient inputs from land, and changes in use or management (see also Chapter 9). Likewise, the impacts of sea level rise on infrastructure, including ports, roads, cities, dikes, levees, and freshwater aquifers and storage facilities, should take into account potential shifts in storm patterns, rainfall rates, and other climate changes (see also Chapters 12 and 13). Improved valuation of nonmarket values, and development of decision-support tools to assess the trade-offs between physical, ecological, and social impacts and response options (see below) are needed to inform coastal management decisions that require long lead times.
Expand the ability to identify and assess vulnerable coastal regions and populations and to develop and assess adaptation strategies to reduce their vulnerability. With sea level rise acting in combination with other physical, social, and economic stressors, the ability to assess the social-ecological vulnerability of coastal regions, improve society's adaptive response options (through technological, economic, and land use changes), and identify constraints to adaptation (including legal, social, political, infrastructure-related, and economic issues) are all critical research needs (see also Chapter 4). This area of research has received very little attention to date, leaving many U.S. coastal communities without adequate place-specific information to inform their adaptation decisions.
Develop decision-support capabilities for all levels of governance. Methods for identifying preferences and weighing alternative adaptive responses will be needed as environmental and social conditions change over time. Frameworks and approaches need to be developed for the evaluation of market and nonmarket values of affected assets and habitats; of the economic costs and other consequences of different response options to sea level rise on both highly developed and less developed shorelines; and of the social and environmental feasibility of different adaptation options (including technological, economic, physical, ecological, social, or legal options) for different coastlines. This will require improved information of the kinds listed above, as well as financial and technical resources that enable decision makers to engage in adaptation planning and actions.
Build capacity. There is a significant shortage of expertise to conduct place-based vulnerability and adaptation needs assessments in coastal regions of the United States (as well as in other sectors and regions, as discussed in Chapter 4), making it extremely challenging to meet the rapidly increasing demand for such information by decision makers. Thus, a strong emphasis on training and capacity building is needed to generate human resources that can produce and also use the information essential for effective adaptation planning along U.S. coasts.
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