COMMUNICATING SEA LEVEL RISE AND COASTAL FLOODING RISKS: THE CASE OF NEW YORK CITY (Invited Presentation)

The New York City Panel on Climate Change (NPCC), a group of academic and private-sector experts, provides the city with advice on future climate risks, including sea level rise (SLR) and coastal flooding, as summarized in reports published in 2010, 2015, and 2019. Close interactions between the NPCC, NYC government agencies, infrastructure managers, and local communities “co-generates” the information most relevant for stakeholder needs. Stakeholder feedbacks are integrated into research design and reports. NYC uses the NPCC 2015 SLR projections in flood hazard mapping and zoning.

The NPCC 2015 report projected a SLR of up to 1.47 m by the 2080s and up to 1.9 m by 2100 (90^th percentile) at the Battery, relative to 2000-2004. In light of increasing land ice mass losses and potential Antarctic Ice Sheet instabilities, NPCC 2019 introduces the Antarctic Rapid Ice Melt (ARIM) scenario, a new physically-plausible upper end, low probability SLR scenario for New York City. At high CO₂ emissions under ARIM, sea level could rise of up to 2.1 m by the 2080s and up to 2.9 m by 2100. ARIM 100-year flood return periods for the 2080s and 2100 (NPCC 2019) would shorten significantly relative to those at the 90^th percentile level (NPCC 2015). Low-lying neighborhoods, particularly surrounding Jamaica Bay, would experience monthly, and eventually daily tidal flooding under upper-end SLR projections by late century.

Guided by NPCC 2015 findings, NYC undertakes programs to strengthen coastal defenses tailored for specific neighborhood needs, which are designed to protect the city through at least mid-century. The city is exploring whether and how they can apply the ARIM scenarios. Given substantial economic and societal costs associated with high-end scenarios such as ARIM, especially by late century, such high-end scenarios should be considered in longer-term coastal risk management planning. Prior estimates of the full possible range of SLR, including ARIM-type scenarios, may help decision-makers meet these challenges.

NPCC members and City representatives presented findings to other engaged stakeholders, policy-makers, and NGOs at two major New York Academy of Sciences events, in 2010 and 2019, and to geoscientists at professional meetings, such as the GSA, AGU, AAG, and at Columbia University and City College of New York.