Surging Seas Sea level rise analysis by Climate Central

Advancing Tools and Methods for Flexible Adaptation Pathways and Science Policy Integration


Journal: Annals of the New York Academy of Sciences
Publication Date: March 2019


Chapter 3 Introduction:

The New York City Panel on Climate Change (NPCC, 2015) sea level rise projections provide the current scientific basis for New York City scientific decision making and planning, as reflected in, for example, the City's Climate Resiliency Design Guidelines. However, since the IPCC (2013) and NPCC (2015) reports, recent observations show mounting glacier and ice sheet losses leading to rising sea levels. Furthermore, new developments in modeling interactions between oceans, atmosphere, and ice sheets suggest the possibility of a significantly higher global mean sea level rise (GMSLR) by 2100 than previously anticipated, particularly under elevated greenhouse gas emission scenarios.

Because of the potentially serious adverse consequences of soaring sea levels to people and infrastructure in low‐lying neighborhoods of New York City, we introduce a new high‐impact sea level rise scenario, Antarctic Rapid Ice Melt (ARIM), which includes the possibility of Antarctic Ice Sheet destabilization. An earlier “Rapid Ice Melt Scenario” (NPCC, 2010) assumed a late 21st century rate of high‐end sea level rise of ∼0.39–0.47 in. per decade, based on paleo‐sea level data after the last Ice Age. ARIM represents a new, physically plausible upper‐end, low probability (significantly less than 10% likelihood of occurring) scenario for the late 21st century, derived from improved modeling of ice sheet–ocean behavior to supplement the current (NPCC, 2015) sea level rise projections.

We briefly summarize key processes that control sea level rise on global to local scales, observed trends, and risks the city faces due to current and ongoing sea level rise. We also briefly recap the NPCC (2015) sea level rise projections for comparison with ARIM. To set the stage for ARIM, we review recent trends in land ice losses (Section 3.5) that reinforce the need to consider such an upper‐end scenario. A more detailed discussion of these trends and technical details of the ARIM scenario are provided in Appendix 3.A.

Chapter 4 Introduction:

Coastal flooding from storm surge is one of the most dangerous and damaging natural hazards that societies face. It was responsible for half of all hurricane‐related mortalities in the United States from 1963 to 2012, far more than any other factor (Rappaport, 2014). Coastal extreme water levels are increasing globally, mainly driven by rises in mean sea level (MSL; e.g., Marcos et al., 2015; Marcos and Woodworth, 2017; Menéndez and Woodworth, 2010). Sea level rise is also causing rapid increases in the annual number of shallow “nuisance floods” for low‐lying neighborhoods (e.g., Strauss et al., 2016; Sweet and Marra, 2014).

The objectives of this chapter are to review the latest knowledge on New York City flood risk from storms and tides, and to evaluate how climate change will affect this risk between now and the end of the century. Methods used by NPCC (2015) for assessing storm‐driven extreme floods are generally repeated here, including the use of the Federal Emergency Management Agency (FEMA, 2013) baseline flood hazards (e.g., the 100‐year flood1) and the methods for adding sea level rise and mapping the resulting hazard (Horton et al., 2015b; Patrick et al., 2015). New advancements include an innovative analysis of monthly tidal flooding based on a dynamic model, a broadened set of sea level rise scenarios supplemented with the Antarctic Rapid Ice Melt (ARIM) scenario (see Chapter 3), and sensitivity analyses that show how differing methods would affect our results. Wind is a primary factor for coastal storm surge, and a brief review is given in Appendix 4.A, with the latest scientific knowledge on what drives extreme wind events in the New York City area and how they may change in the future.




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