Assessing the local impacts of sea level rise

Transcription

1 Assessing the local impacts of sea level rise Ian Miller, Coastal Hazards Specialist Washington Sea Grant MRC Conference Port Townsend, WA 5 December 2014 With contributions from: Eric Grossman, USGS; Lara Whitely-Bender, CIG; Guillaume Mauger, CIG; Sascha Petersen, Adaptation International; Hansi Hals, Jamestown S Klallam Tribe; Cindy Jayne, NOPRCD; Kate Dean, NOPRCD; Heather Baron, WA DOE; Peter Ruggiero, OSU

2 Objectives Some SL observations from the inland waters and some general SL background Outline our process for scenario-based SLR planning for communities Critique our process as a way to highlight future research needs

3 We are already influenced by SLR Photo from Cliff Mass Weather Blog, courtesy of West Seattle Blog Seattle, 17 December 2012

4 Coastal Flooding is a game of probabilities Coincidence of a spring tide, with solar aphelion and lunar perigree Coinciding with a storm (low-pressure), that raises the NTR

5 In the near-term SLR changes the equation a bit every year Coincidence of a spring tide, with solar aphelion and lunar perigree MSL ~0.2 feet higher than in 1983 Nuisance Flooding Hours in Seattle, WA Coinciding with a storm (low-pressure), that raises the NTR Based on Sweet et al, 2014

6 Eustatic and Relative SLR Thermal Expansion Eustatic = sea level measured against a geocentric reference frame in other words not referenced against the land. This is really only directly measured by satellites. Ice Melt but not just any ice

7 Eustatic patterns Altimetry derived global sea level, (sealevel.colorado.edu)

8 Global Eustatic SLR Projections National Academies (2012) AR5 IPCC AR5 (2014) IPCC AR4 (2007) Adapted from National Academies of Science, 2012

9 Global Eustatic SLR Projections Current ice dynamics investigations suggest that this estimate may be too low AR5 Joughnin, et al. May 2014, Science Rignot, et al. May 2014, GRL IPCC AR5 (2014) IPCC AR4 (2007) Adapted from National Academies of Science, 2012

10 Relative SLR Relative sea level = level of the sea measured against the land. This is what tide gauges measure and what matters from a hazards standpoint Influenced by VERTICAL LAND MOVEMENT (VLM) Relative Sea Level = Eustatic Sea Level + VLM

11 From Mazotti et al RSL Patterns in the PNW are complex! Complexity due primarily to VLM which varies over VERY short spatial scales

12 These are the projections we usually get from international, national, or regional climate assessments This is what we want for community planning This is often unknown, assumed or generalized Relative Sea Level = Eustatic Sea Level + VLM

13 Community Process Outline the scenario-planning process, tools and methods And highlight some of the strengths and weaknesses of this approach

14 Regional SLR Projections Derived from the National Academies of Science 2012 report Primary components are steric sea level (modeled), land-based ice melt (extrapolations from estimates), and finger-printing (estimated) Sea Level Change (cm) PNW Regional Sea Level Projections w/o VLM A1B A1F1 Lower Uncertainty Bound Upper Uncertainty Bound Their regional estimate of vertical land movement is removed Years from 2000

15 Incorporate VLM Derived from tide gauge data combined with continuous GPS data The east-west pattern of uplift-tosubsidence is consistent with a subduction zone

16 Derive Local Projections Combine SLR projections with local rates of vertical land movement to generate a set of local, or relative sea level projections These can be mapped as a future MHHW line

17 Storm Impacts The 10 year return frequency interval water level (above MHHW) is added to each map to represent areas that are at risk for intermittent flooding

18 > 2060 Scenario-based planning

19 A brief list of limitations and Doesn t really express sea level probabilistically but it IS a probability game. assumptions Does not include geomorphic adjustment of the shoreline due to sea level change, wave energy changes or other climate-related shoreline impacts. In other words no erosion! We use current water level patterns to model future storm impacts, even though climate change MAY change storm patterns. From Baron, 2011

20 > 2060 Vulnerability Assessment From Critical Infrastructure Focus Group Workshop, Port Angeles, 14 November 2014

21 More so than regional, national or international assessments, these types of local climate change assessments seem to generate chatter 3-4 January 2014 Peninsula Daily News

22 Conclusions and Next Steps: There is a need for localizing climate change science, which is inherently global, to better support community adaptation we currently follow a scenario-based methodology roughly analogous to NOAA s guidance The outcomes were good in that the tools developed helped the JSKT incorporate SLR into their planning processes But there are ways to improve these sort of community-scale assessments given better information and techniques Better info on VLM Better approaches for dealing with sea level variability Better data and projections for shoreline change Ian Miller, PhD Coastal Hazards Specialist immiller@u.washington.edu

23 Where I am heading: Probabilistic Approach

24 Integrated Assessment From Baron, 2011

25 What is sea level? The sea changes elevation (measured against some datum) on a variety of time-scales

26 What is sea level rise (or fall)? The long-term (multiple decades at least) change in the level of the sea measured relative to some arbitrary feature or datum

27 What is sea level rise (or fall)? Sea level patterns not linear?

28 What is sea level rise (or fall)? Sea Level is not clean, which can make SLR hard to detect and interpret

29 It gets nerdier from here

30 What we are working on now: Improving estimates of VLM Using tide gauge data should provide a very robust estimate of the movement of coastal stations against each other

31 Implications of these new estimates VLM estimate for Seattle = -1.2±0.2 mm/yr Relative Sea Level VLM = Eustatic Sea Level 1.97±0.16 mm/yr 1.2± 0.2 mm/yr = 0.9± 0.2 mm/yr

32 Implications of these new estimates VLM estimate for Seattle = -1.2±0.2 mm/yr Relative Sea Level VLM = Eustatic Sea Level 1.97±0.16 mm/yr 1.2± 0.2 mm/yr = 0.9± 0.2 mm/yr Global estimate is 1.7 mm/yr?

33 Where I am hoping to head: Approaches that deal with variability The PNW is insanely variable and its not always easy to deal with. A smooth curve is NOT the way sea level works around here

34 Satellite Radar Interferometry. Finnegan et al Tide Gauge, levelling and gps combined. Komar et al 2012 Need Better VLM Data

35 Incorporate Shoreline Change Courtesy of Randy Johnson, Jamestown S Klallam Tribe

36 Probabilistic Approach

37 Integrated Assessment From Baron, 2011

38 Clarify VLM Discrepancies Re-levelling Verdonck, 2006 Short GPS (~5 years) Mazotti and others, 2006 Longer GPS (>10 years for many stations) PANGA, 2014

39 Data reliant approaches

40 Step 1 Identify Community Priorities (both vulnerabilities and geographies

41 From tide gauge and monument re-levelling (~100 yr record). Verdonck, 2006

42 GPS-based vertical land movement records ~5.5 years Mazotti et al 2008

43 Levelling with correction for bias. Burgette 2009

44 Tide Gauge, levelling and gps combined. Komar et al 2012

45 Mitchell et al Levelling,Tide gauge, assumed ASLR

46 What is sea level rise (or fall)? From NOAA s Tides and Currents web page The long-term (multiple decades at least) change in the level of the sea measured relative to some datum

47 Relative SLR Relative sea level = level of the sea measured against the land. This is what tide gauges measure and what matters from a hazards standpoint Influenced by VERTICAL LAND MOVEMENT (VLM) Both Very Hard to Measure Relative Sea Level = Eustatic Sea Level + VLM

48 Incorporate VLM Usually not on the coast Short records and large uncertainties There are discrepancies

49 Justification for not including the B1 scenario: Contemporary comparisons between emissions scenarios and global sea level rise A Satellite Altimetry A1F1 A1B Tide Gauges B1 From Rhamstorf et al, Comparing climate projections to observations up to 2011

50 A brief list of limitations and assumptions We are learning more and more about eustatic SLR projections of magnitude and regional variability changes over time Likewise, VLM estimates are maturing Doesn t include sea level variability, or express sea level probabilistically but it IS a probability game. Does not include geomorphic adjustment of the shoreline due to sea level change, wave energy changes or other climate-related shoreline impacts. In other words no erosion! Sea level rise may change tidal patterns slightly not included here We use current water level patterns to model future storm impacts, even though climate change MAY change storm patterns.

51 SLR changes the equation a bit every year 29 November 2014 Coincidence of a spring tide, with solar aphelion and lunar perigree Photo by Dr. Melissa Poe, WSG MSL ~0.2 feet higher than in 1983 Coinciding with a storm (low-pressure), that raises the NTR