Session 4 - Climate Change Long-term Variations in Tidal Characteristics and Sea-Level in the Delaware Estuary Stephen Gill, Allison Allen, Carolyn Lindley, William Sweet, Chris Zervas NOAA/NOS Center for Operational Oceanographic Products and Services, Silver Spring, MD Session 4 - Climate Change

Long-term Variations in Tidal Characteristics and Sea-Level in the Delaware Estuary Outline Variations in monthly mean sea level Relative sea level trends Vertical land motion Analysis of Extremes Frequency and Duration of Inundation Coastal Storm Response Tidal datums and long-term changes in range of tide On-line Tools and Impact studies

Delaware Bay NOAA National Water Level Observation Network (NWLON) and PORTS Observing Systems

NOAA Sea Levels Online

Seasonal Variations in Monthly Mean Sea Level

Long-term Variability in Monthly Mean Sea Level

At present rate, relative sea level will rise 0 At present rate, relative sea level will rise 0.36m from 2010 to 2100 at Cape May

At present rate, relative sea level will rise 0 At present rate, relative sea level will rise 0.29m from 2010 to 2100 at Lewes

At present rate, relative sea level will rise 0 At present rate, relative sea level will rise 0.31m from 2010 to 2100 at Reedy Point

At present rate, relative sea level will rise 0 At present rate, relative sea level will rise 0.25m from 2010 to 2100 at Philadelphia

Global Sea Level Global sea level rise projections Comparison of latest peer-reviewed research on global sea level rise estimates Looking at all the research up to 2010, this bar graph is showing the scale of max and min estimates from the research Research is greater than IPCC reports IPCC says it’s research was conservative because they didn’t take the ice melts into account Not all research in the graph above takes ice melts into account – it’s a mix of approaches- some is empirical Main message: whatever projection you use, need to consider the approach and take it into account

Estimating the Vertical Land Motion Component from Tide Station Records Construct a “Regional” oceanographic composite from the tide stations in a region Subtract out the 1.7mm/yr 20’th century rate (IPCC2007) Regional Oceanographic Signal Estimated vertical land motion Estimated vertical land motion Estimated vertical land motion Estimated vertical land motion

Locations of NGS Continuously Operating Reference Systems (GPS-CORS) Direct measurements of vertical land motion can be obtained using continuous GPS observations. NGS is currently updating vertical velocities from the national CORS network which can be compared to the indirect estimation method in the previous slides.

Analysis of Extremes - Monthly Highest Observed Tides

Exceedance Probabilities Relative to Elevations of Tidal Datums

Exceedance Probability Curves with 95% Confidence Intervals Elevation relative to MHHW (meters) Log scale of recurrence interval (in years and percent)

Frequency and Duration of Inundation

Frequency and Duration of Inundation

Frequency and Duration of Inundation

Observed Tides during Coastal Storm Events - 2010

Observed Tides during Coastal Storm Events - 2010

Non-Tidal Effects of Coastal Storms

It takes 6. 4 hours for high tides and 8 It takes 6.4 hours for high tides and 8.1 hours for low tides to progress up river to reach Trenton from Lewes. The mean range of tide increases from 1.24m (4.1 ft) at Lewes to 2.49m (8.2 ft) at Trenton

The Delaware River had been dredged to a depth of 18 ft by the late 1800s. By the 1940s, the USACE had deepened the navigational channel from Philadelphia to the ocean to a depth of 40 ft. The channel upstream from Philadelphia was then dredged to 40 ft.

Tools for Assessing Impacts of Sea Level Rise http://csc-s-web-p.csc.noaa.gov/de_slr/

Tools for Assessing Impacts of Sea Level Rise

US DOT Impact Study This study was designed to produce high level estimates of the net effect of sea level rise and storm surge on the national transportation network. It was designed primarily to aid policy makers at the U.S. Department of Transportation by providing estimates of these effects as they relate to roads, rails, airports and ports. - Effect of sea level change on ports and transportation infrastructure http://climate.dot.gov/impacts-adaptations/pdf/entire.pdf

US DOT Impact Study The study applied existing predictions of global sea level rise from the Intergovernmental Panel on Climate Change’s (IPCC) Third and Fourth Assessment Reports The study constructed maps based on DEM’s using NOAA data for a MHHW surface and Highest Observed Water Levels (HOWL) to incorporate storm surge for various sea-level rise scenarios

Thank you! Questions? Stephen.gill@noaa.gov 301-7132981 ext 139

Background Slides

Sea Level Change – Two Distinct Attributes Global Sea Level The average height of all the Earth's oceans Caused by the global change in the volume of water in the world‘s oceans in response to three climatological processes: Ocean mass change associated with long-term forcing of the ice ages Density changes from total salinity Heat content of the world‘s ocean, which recent literature suggests may be potentially accelerating due to global warming Relative Sea Level The local change in sea level relative to the elevation of the land at a specific point on the coast. Reminder: There is an important distinction between the global sea level trend and relative sea level trends (based on local sea level measurements), which must be understood in order to interpret changes to a coastline or particular location, and to properly apply the information. Global: "Global Sea Level Rise" refers to the increase currently observed in the average Global Sea Level Trend, which is primarily attributed to changes in ocean volume due to two factors: ice melt and thermal expansion. Relative Sea Level Trends reflect changes in local sea level over time and are typically the most critical sea level trend for many coastal applications, including coastal mapping, marine boundary delineation, coastal zone management, coastal engineering, sustainable habitat restoration design, and the general public enjoying their favorite beach. Relative sea level change is a combination of both global and local sea level change due to changes in estuarine and shelf hydrodynamics, regional oceanographic circulation patterns, hydrologic cycles (river flow) and local and/or regional vertical land motion (subsidence or uplift) Transition to what the science is telling us about global sea level

Global Sea Level The Global Mean Sea Level Trend From Tide Gauges & Altimetry Suggests an Acceleration Church et al., 2006 Satellite altimetry ~2.9 mm/yr 1993-present ~0.7 mm/yr, 1870-1935; then 1.8 mm/yr 1936-2001 Two primary causes of global sea level rise: Thermal expansion Addition of water volume (glaciers, ice sheets, etc) mm This slide depicts the global sea level trend with altimetry (over all 2.9mm rise, but large regional variation) This graph shoes what Church et al. is saying ; rates of slr accelerated after 1930 What the latest research is saying Tide gauges tend to agree with satellite altimetry at regional scales(so satellite altimetry tends to have credibility) Primary causes of global sea level rise are: 1) A steady increase in global atmospheric temperature creates an expansion of saline sea water (i.e., salt water) molecules (called thermal expansion), thereby increasing ocean volume. 2) Melting of glaciers and continental ice masses, such as the Greenland ice sheet, which are linked to changes in atmospheric temperature, can contribute significant amounts of freshwater input to the Earth's oceans

Global Sea Level - The Satellite Altimeter Record The overall global rate from multiple missions. Coverage from 60N to 60S from 1993 to present. There is a diversity of regional rates from satellite altimetry that go into the computation of the overall global rate.

Sea Level Rise Trends and Projections IPCC, 2001 IPCC, 2007 Need to change text on the slide What the climate projects are from the IPCC reports and latest research IPCC 2007 narrowed the uncertainty bounds: The Intergovernmental Panel on Climate Change (IPCC) Report estimates that the global sea level rise was approximately 1.7-1.8 millimeters per year (mm/yr) over the past century (IPCC, 2007), based on tide station measurements around the world, with projected increased trends in sea level in the 20th Century based on global climate models. The 2007 IPCC report projects that future sea-level rise will be slightly less than reported in the 2001 assessment (18 to 59 cm). Colored lines are various projections from the IPCC Third Assessment Report (TAR). The central sea-level rise estimate for the 2001 report was 48 cm. It is worth noting that the 2007 report makes no effort to consider potential contributions from accelerated ice melt in Greenland and Antarctica-due to a lack of a consensus regarding the ice mass balance trends and the ability to predict the behavior of Greenland and Antarctic ice masses. Because of this, the report has received criticism from several climate scientists including Jim Hansen. They advocate that in the absence of this information, the 2007 report may severely underestimate the potential sea-level changes that can be expected over the next century. In this figure, Stefan Rahmstorf uses an empirical argument to suggest that at the very least we must expect a sea-level rise on the order of 1 m over the next century. Transition to Graphical representation of comparisons (on next slide) www.ucar.edu The Intergovernmental Panel on Climate Change (IPCC) 2007 report projects a 18 to 59 cm sea level rise from a 1.1 and 6.4 °C temperature increase during the 21st century (this projection does not consider potential contributions from accelerated ice melt in Greenland and Antarctica).