Global and regional sea level rise scenarios for the United States

This report provides regional sea-level rise scenarios and tools for coastal preparedness planning and risk management in the United States. It refines six global sea level rise scenarios (Low, Intermediate Low, Intermediate, Intermediate High, High, and Extreme) decade by decade. The report provides a range of possible scenarios and the authors concluded that evidence supports a “worst-case” global average sea-level rise of about 8.2 feet by 2100. Recent studies on Antarctic ice-sheet instability indicate that such rises may be more likely than once thought, the report says. The report also focuses on the frequency of moderate-level flooding that triggers a NOAA coastal/lakeshore flood warning of a serious risk to life and property. In general, the water level that triggers a warning is about 2.6 feet above the highest average tide and has a 20 percent chance of occuring each year. The scenarios are tailored to produce regional projections in areas including the U.S. Atlantic, the Gulf of Mexico and Pacific coasts, Alaska, Hawaii, the Caribbean and Pacific island territories. This document helps communities track a range of scenarios that they may fall under for each of the timeframes, and assess their risk of experiencing impacts under the scenario. The researchers scaled these scenarios down to a one-degree gridded resolution, or roughly 70 miles. This allows a coastal manager in Miami and one in Mobile, Alabama, using the same scenario to prepare for different outcomes.

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