Planning for Annapolis Sea Level Rise and Future Extreme Water Levels

Transcription

1 Planning for Annapolis Sea Level Rise and Future Extreme Water Levels U.S. Naval Academy Sea Level Rise Advisory Council 31 October 2017 CAPT Emil Petruncio, USN (Ret.), PhD Associate Professor Gina Henderson Photo Credit:

2 The U.S. Naval Academy is a 338 acre National Historic Landmark. Photo: Forbes Images

3 The buildings, monuments, and traditions of the U.S. Naval Academy preserve and promote the core values of the Navy and Marine Corps: Honor, Courage, and Commitment.

4 Naval Academy Sea Level Rise Advisory Council Constituted in July 2015 by direction of the Superintendent of the Naval Academy Mission: Develop a Sea Level Adaptation Plan for the Superintendent on matters pertaining to flooding due to sea level rise and severe weather events in the Annapolis area. This plan, developed in coordination with the City of Annapolis, the State of Maryland and key federal agencies, will suggest a path forward for planning for the impacts of sea level rise on the Naval Academy through Specific focus: impacts to operational requirements of the Naval Academy, including the USNA lower yard, upper yard and the federal property on North Severn.

5 Elevation (Feet) Relative to MLLW 8 Annapolis Hourly Sea Level Data for 1933 and 2003 Referenced to Mean Lower Low Water Dashed line indicates level of minor flooding at Annapolis City Dock (2.38 ft above MLLW) 6 4 Cumulative Hours of Flooding minor moderate 1933: : Chesapeake Potomac Hurricane Hurricane Isabel Avg = 0.86 ft 1933 Avg = 0.11 ft -4 Both years featured major flooding events due to storm surge, but average sea level in 2003 was 0.75 feet (9 inches) higher than in 1933, resulting in broader areal flooding for extreme events and much more frequent occurrences of minor flooding. According to NOAA (Sweet and Park, 2014), the number of nuisance flood days for Annapolis has increased from 3 per year during to 34 per year during

6 Water Level Relative to MLLW (feet) Nuisance flooding events in Annapolis have increased significantly in the past several decades, and are more frequent during Mid-Spring to Mid-Autumn due to warmer surface waters and thermal expansion. Nuisance Flooding at USNA (MLLW ft) Nuisance Flooding at Annapolis City Dock (NWS Minor Threshold = MLLW ft) MHHW MHW MSL MLLW Annapolis Hourly Water Levels 15 April 15 October 2014

7 Recent Sea Level Studies 2012 NRC Report on MSLR Processes, NOAA Sea Level Rise Scenarios for National Climate Assessment (NCA) 2013 IPCC Assessment Report 5 (AR5), MD Update of 2008 Assessment, Updated USACE Guidance 2014 National Climate Assessment 2016 DoD-led, Multi-Agency Report on Regional Scenarios (Hall et al., 2016), UCS Report on 18 Military Installations, Military Expert Panel Report on SLR 2017 NOAA Global and Regional SLR Scenarios for the U.S.

8 Sea Level Relative to MSL in 1992 (ft) Relative Sea Level Rise Scenarios for Annapolis from Hall et al. (2016) and Sweet et al. (2017) with Annapolis Monthly Mean Sea Level Data for Extreme (2.5m) High (2.0m) Intermediate High (1.5m) Intermediate (1.0m) Intermediate Low (0.5m) Low (0.3m) High Emission Scenario with Max Contribution from Ice Sheets Moderate to High Emissions Low Emissions; Major Carbon Cuts and Carbon Removal The six Global Mean Sea Level (GMSL) scenarios in Sweet et al., 2017, identified by the height in meters in 2100 relative to MSL in 2000, span the range of scientifically plausible sea level rise scenarios. The shaded regions represent a central 80% probability range for each scenario. These curves have been adjusted to depict MSL relative to The five scenarios described in Hall et al., 2016 correspond to GMSL of 2.0m, 1.5m, 1.0m, 0.5m, and 0.2m relative to MSL in 1992, and are indicated by thick black lines Year Graphic by E.T. Petruncio

9 During the Holocene Epoch, the rate of sea level rise has varied between still stands and periods of rapid rise (several meters per century), resulting in submerged marine terraces. The rapid rates of sea level rise indicate that ice shelves can break up rapidly. MWP = Melt Water Pulse Graphics courtesy of Ocean Exploration Trust and Liu et al., 2004, Holocene development of the Yellow River s subaqueous delta, North Yellow Sea. Marine Geology, 209(1-4): 45-67

10 Feet Above Mean Sea Level Hall et al. (2016) Annapolis Sea Level Rise Scenarios Referenced to MSL for (MSL = 0 in 1992) Note: Increases in MSL may not be as smooth as depicted, especially for highest scenario (when most SLR would occur beyond 2070) Isabel Hospital Point, Dewey Field, Gate 1 Mid Store Lot, NW End Holloway Rd Waffle Lot Ramsay Rd, McNair Rd, City Dock An average high tide (Mean High Water) will add 0.47 ft to these values twice daily. For short range forecasts (2035 and earlier), interannual variability (+/- 4 inches) may be more significant than changes due to long term sea level rise.

11 College Creek Severn River Spa Creek

12 4 ft Above Mean Higher High Water (4.71 feet above MSL) (Mid Store Lot, Brownson Rd, 8 th Wing Lot, Gate 1 area) 2.5m: m: m: m: 2096 Dates at which MSL reaches this level for various scenarios Datum: Mean Higher High Water (.71 feet above MSL) Graphic courtesy of Climate Central

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14 Extreme Events Hurricane Isabel 19 Sep hours (5 inches) prior to peak water level

15 Inundation of the U.S. Naval Academy after Hurricane Isabel

16 6 ft Above Mean Higher High Water (6.71 feet above MSL) (Hurricane Isabel) 2.5m: m: m: 2096 Date at which MSL reaches this level for the highest scenario Datum: Mean Higher High Water (.71 feet above MSL) Graphic courtesy of Climate Central

17 Sea Level Relative to MSL in 1992 (ft) Annapolis Historical Sea Level, Scenario for a 1.0m rise in Global Mean Sea Level and Extreme Water Levels based on Hall et al., Extreme Water Levels (ft) for 1.0m GMSL Scenario (Hall et al., 2016) Flooding Event % / 5 Year % / 20 Year % / 50 Year % / 100 year 7 1% /100 Year % / 50 year Isabel 6 5 5% / 20 year 20% / 5 year Hospital Pt, Dewey Fld, Gate Adjustment for MHHW Midstore Lot Waffle Lot 2 Ramsay Rd, McNair Rd, City Dock Year

18 Summary Uncertainties in future Sea Level Rise (SLR) include climate forcings (cloud cover, aerosols, etc.), physical system response (Antarctic ice shelves and glaciers, etc.), and human behavior (future greenhouse gas emissions). We should deal with these uncertainties by considering a range of SLR scenarios and risk tolerances for various projects. Range of plausible SLR scenarios for Annapolis, relative to Mean Sea Level (MSL) (MSL = 0 in 1992): Hall et al. (2016) Sweet et al. (2017) ft ft ft ft Under a conservative SLR scenario (1m / 3.28 ft rise in Global MSL by 2100), nuisance flooding at USNA will occur daily during the summer months beginning around Flooding due to storm surge will be exacerbated by SLR. Most scenarios considered by Hall et al. (2016) show Hurricane Isabel-like water levels becoming a 1 in 20 year event by 2065 and a 1 in 5 year event by the end of the century. These projections are based on historical storm statistics, and assume no changes in storm frequency or intensity.

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20 Diving Deeper

21 The Northern Channel Islands were connected during the last glacial maximum, when sea level was approximately 120m lower. As sea level rose, wave action shaped marine terraces. San Miguel Santa Rosa Santa Cruz Marine Terraces Anacapa

22 Meters Meters Comparison of Mean Sea Level Trend in Annapolis Tide Gauge Data to Highest and Lowest Scenarios in Hall et al. (2016) As of 2015, the rate of sea level rise in Annapolis was / mm/yr m (2.6 ft) 0.2m (0.7 ft) 20 The lower bound for sea level rise scenarios should be based on historical trends dating back at least 50 years, as shorter record lengths (such as satellite altimetry measurements) may be affected by interannual / decadal variability. A plausible range of sea level rise in Annapolis by 2050 is from 0.2 m (0.7 ft) to 0.8m (2.6 ft), relative to Mean Sea Level for the current tidal epoch ( ) (Hall et al., 2016)

23 Based on Figure 5 from Alexander Nauels et al 2017 Environ. Res. Lett doi: / /aa92b6

24 Combined Sea Level Rise and Extreme Water Level Values (Hall et al., 2016) Base Unit: Feet, Referenced to Mean Sea Level (add 0.05 for NAVD88) These projections assume stationarity of historical storm statistics 20% / 5 Year Event 5% / 20 Year Event Scenario Lowest Low Medium High Highest Scenario Lowest Low Medium High Highest Scenario Lowest Low Medium High Highest % / 50 Year Event 1% / 100 Year Event Scenario Lowest Low Medium High Highest