WaveWave drivendriven -levelsea-level anomalyanomaly atat MidwayMidway AtollAtoll

RonRon HoekeHoeke CSIROCSIRO SeaSea LevelLevel andand CoastsCoasts

JeromeJerome AucanAucan LaboratoireLaboratoire d'Etudesd'Etudes enen GéophysiqueGéophysique etet OcéanographieOcéanographie SpatialeSpatiale (LEGOS),(LEGOS), IRDIRD

MarkMark MerrifieldMerrifield SOESTSOEST –– UniversityUniversity ofof HawaiiHawaii

Funding:Funding: ••NOAANOAA CRCPCRCP ••JIMARJIMAR –– UniversityUniversity ofof HawaiiHawaii ••AustralianAustralian InstituteInstitute ofof MarineMarine ScienceScience

(AIMS)(AIMS)

••CSIROCSIRO SeaSea LevelLevel andand CoastsCoasts ((AusAID)AusAID) photo: Scott Smithers

WaveWave set-upset-up atat PacificPacific atollsatolls andand islandsislands

“..the power of the breaking waves is utilized to maintain a water level just inside the surf zone about 1.5 ft above .”

Munk and Sargent (1948) Adjustment of Bikini to waves, Transactions, Am. . Union, 29(6), 855-860.

Wave set-up may be “as much as 20% of the incident .”

Tait, R. J. (1972) Wave Set-Up on Coral Reefs, J. Geophys. Res., 77(12). WaveWave set-upset-up atat PacificPacific atollsatolls andand islandsislands

Steep-sloped : /: Wave dissipation Wave dissipation close farther offshore to / edge

Smaller waves Larger waves Larger storm surge Smaller storm surge

Graber et al. (2006) Coastal forecasts and storm surge predictions for tropical cyclones: A timely partnership program, , 19(1), 130–141. PacificPacific wavewave climateclimate

Hoeke et al. (2011) J. Geophys. Res., 116(C4), C04018. WaveWave set-upset-up inundationinundation eventsevents

Nov. 28, 1979 Pohnpei Majuro Dec. 8, 2008

Fiji T imes,May 21, 2011 Takuu Dec. 10, 2008

Caldwell,Vitousek, Aucan (2009), Frequency and Duration of Coinciding High Surf and along the North Shore of Oahu, Hawaii, 1981-2007, J. Coastal Res., 25(3). WaveWave set-upset-up inundationinundation eventsevents

*Wave hindcast data provided by Mark Hemer (CSIRO) **Taku’u water level data provided by John Hunter (U. Tas) WaveWave drivendriven sea-levelsea-level anomalyanomaly atat MidwayMidway AtollAtoll WaveWave drivendriven sea-levelsea-level anomalyanomaly atat MidwayMidway AtollAtoll WaveWave drivendriven sea-levelsea-level anomalyanomaly atat MidwayMidway AtollAtoll WaveWave drivendriven sea-levelsea-level anomalyanomaly atat MidwayMidway AtollAtoll

Multi-variate ENSO Index (MEI) Wolter and Timlin (1998)

NDJFM North Pacific Anomalies Index (NPI) Trenberth and Hurrell (1994) CoupledCoupled numericalnumerical wave/flowwave/flow modelmodel

SWAN Wave Model: phase-averaged solution of the discrete spectral balance of wave action density Delft3D Circulation Model: finite - difference coupled wave/flow numerical solution to Navier- Stokes equations (non-steady, incompressible, continuity, hydrostatic)

Bathymetry: NOAA Technical Memorandum NESDIS NGDC-33 InIn situsitu observationsobservations

WTR/WW3

WTR/WW3

1 R ADP T 2 ADP W R T ADP W

ADP

ADP ADP

ADP CoupledCoupled numericalnumerical wave/flowwave/flow modelmodel CoupledCoupled numericalnumerical wave/flowwave/flow modelmodel CoupledCoupled numericalnumerical wave/flowwave/flow modelmodel

2 (xm  xo ) Model Skill  2 ( xm  xo  xo  xo ) WaveWave drivendriven sea-levelsea-level anomalyanomaly atat MidwayMidway Atoll:Atoll: ConclusionsConclusions

Midway Atoll’s tidal gauge record presents a unique dataset to examine .

A proxy record of north Pacific storm activity back to 1947?

Water level ( gauge) data + numerical modeling is needed to help better understand and predict inundation events at reefs and islands in the Pacific and Indian WaveWave drivendriven sea-levelsea-level anomalyanomaly atat MidwayMidway Atoll:Atoll: FutureFuture WorkWork

Explore wave height -> reef rim depth -> reef channels -> wave setup relationship (implications for extreme events and )

Figure 7a: Gourlay and Colleter (2005) Wave-generated flow on coral reefs--an analysis for two- dimensional horizontal reef-tops with steep faces, , 52(4), 353-387.

Apply model to other Pacific Atolls (Funafuti, Tuvalu and Majuro, Marshall Islands) [email protected]