Sea Level Changes: Implications for the Coast

·I·G·C·I·

RICHARD WARRICKInternational Global Change Institute (IGCI)

University of Waikato

Major sources of uncertainty:• GHG emission rates GHG emission rates

(socio-economic and technological uncertainty)(socio-economic and technological uncertainty) • Climate sensitivity Climate sensitivity

(scientific modelling uncertainties)(scientific modelling uncertainties)

• Land ice response (additional uncertainty for sea level change)

FUTURE WARMING and SEA LEVEL RISE – how much ?

Average of models, All emission scenarios

Tem

pera

ture

Cha

nge

(deg

.C)

Global Temperature Change

(IPCC, 2001)

Future Projections

Average of models, All emission scenarios

All models, All emission scenarios

Tem

pera

ture

Cha

nge

(deg

.C)

Global Temperature Change

1.4 oC lowest scenario, low sensitivity

5.8 oC highest scenario, high sensitivity

(IPCC, 2001)

Future Projections

Global Sea-level Rise

(IPCC, 2001)

Average of models, All emission scenarios

All models, All emission scenarios

Sea-

leve

l Ris

e (m

etre

s)

All models, All emission scenarios, Land-ice uncertainty

Future Projections

8 cm lowest scenario, low sensitivity, low land-ice

88 cm highest scenario, high sensitivity, high land-ice

Global Sea-level Rise

(IPCC, 2001)

Average of models, All emission scenarios

All models, All emission scenarios

Sea-

leve

l Ris

e (m

etre

s)

All models, All emission scenarios, Land-ice uncertainty

Future Projections

Aspects of future change that are important for the coast• Sea level • Sea-surface temperature• Rainfall amounts, intensity• Changes in ENSO• Storm frequency and intensity• Storm surge risks• Wind and wave regimes

WARNING!!: PREDICTIONS OF REGIONAL-SCALE CHANGES ARE STILL VERY

UNCERTAIN

CoastCLIM: Modelling Shoreline Change

CoastCLIMModelling Change in Shoreline Position

dC/dt = (Ceq - C)/τ + Εs Shoreline Change

τ is τime (yrs)C is τhe shoreline posiτion (m) relaτive τo τhaτ of τ=0,Ceq is τhe equilibrium value of Cτ is τhe shoreline response τime (yrs)Εs is a sτochasτically-generaτed sτorm erosion facτor

Ceq = z l/(h+d) + S Bruun Rule

z is sea level change (m)l is τhe closure disτance (m)h is τhe depτh of maτerial exchange (m)d is τhe dune heighτ (m)S is long τerm accreτion (m)

dC/dt = (Ceq - C)/τ + Εs Shoreline Change

τ is τime (yrs)C is τhe shoreline posiτion (m) relaτive τo τhaτ of τ=0,Ceq is τhe equilibrium value of Cτ is τhe shoreline response τime (yrs)Εs is a sτochasτically-generaτed sτorm erosion facτor

Ceq = z l/(h+d) + S Bruun Rule

z is sea level change (m)l is τhe closure disτance (m)h is τhe depτh of maτerial exchange (m)d is τhe dune heighτ (m)S is long τerm accreτion (m)

CoastCLIMModelling Change in Shoreline Position

dC/dt = (Ceq - C)/τ + Εs Shoreline Change

τ is τime (yrs)C is τhe shoreline posiτion (m) relaτive τo τhaτ of τ=0,Ceq is τhe equilibrium value of Cτ is τhe shoreline response τime (yrs)Εs is a sτochasτically-generaτed sτorm erosion facτor

Ceq = z l/(h+d) + S Bruun Rule

z is sea level change (m)l is τhe closure disτance (m)h is τhe depτh of maτerial exchange (m)d is τhe dune heighτ (m)S is long τerm accreτion (m)

CoastCLIMModelling Change in Shoreline Position

dC/dt = (Ceq - C)/τ + Εs Shoreline Change

τ is τime (yrs)C is τhe shoreline posiτion (m) relaτive τo τhaτ of τ=0,Ceq is τhe equilibrium value of Cτ is τhe shoreline response τime (yrs)Εs is a sτochasτically-generaτed sτorm erosion facτor

Ceq = z l/(h+d) + S Bruun Rule

z is sea level change (m)l is τhe closure disτance (m)h is τhe depτh of maτerial exchange (m)d is τhe dune heighτ (m)S is long τerm accreτion (m)

·I·G·C·I·CoastCLIM Outputs

Shoreline Change1940-2100

Shoreline Change1940-2100

Shoreline Change1940-2100

Bay of Plenty Application

Shoreline in 2100

Present shoreline

Bay of Plenty Application

Shoreline in 2100

Present shoreline

DEMONSTRATION