Climate change and North Sea storm surge extremes - an

ensemble study (PRUDENCE)

Katja Woth & Hans von StorchInstitute for Coastal Research

GKSS Research Center

Geesthacht, Germany

Institute for Coastal ResearchGKSS, Germany

• Assessing ongoing change of coastal climate.• Deriving scenarios of plausible, possible futures

of coastal climates.• Special emphasis on wind-related aspects, i.e.,

wind force, storm surges and ocean waves.• Special emphasis on North Sea and Baltic Sea.• Participant in HIPOCAS, PRUDENCE and

ENSEMBLES.

NCEP Globale Reanalysen ( 210 km x 210 km )1958 - 2002

WAM sig. Wellenhöhe und Richtung 21.02.1993 12 UTC

BAW - TELEMAC 2DWasserstand und

barotrope Strömung 21.02.1993 12 UTC

Auflösung zwischen etwa 100 m und 5km

Auflösung etwa 5 x 5 km

Auflösung etwa 50 x 50 km

REMO Windgeschwindigkeit und Richtung 21.02.1993 12 UTC

HIPOCAS:Für Rekonstruktionen verwendete ModellketteGebiet hier: Nordsee und östlicher Nordatlantik

Climate risk assessments done with these models

• Reconstruction of past and ongoing state and change

• PCPnP futures(PCPnP = plausible, consistent, possible but not necessarily probable = scenarios)

Not assimilated into NCEP (Ionic Sea)

Comparison of wind speed statistics with in-situ data: RCM is skillful in describing marine wind statistics

External Forcing – Future Scenarios

EU-Project PRUDENCE (Prediction of Regional scenarios and Uncertainties for Defining EuropeaN Climate change

risks and Effects)

Impact scenarios

today

scenario

GCM

today

scenario

RCMs

scaleglobal local

ImpactImpactmodelmodel

Storm SurgeModel forthe North Sea:

- TRIM 3D

RegionalClimate Models:

- CLM- REMO- HIRHAM- RCAO

Global Climate Model

(HadAM3) IPCC A2

SRES Scenario

(1961-1990 / 2071-2100)

RCAO HIRHAM

CLM REMO5

A2 - CTL: changes in 99 % - iles of wind speed (6 hourly, DJF): west wind sector selected (247.5 to 292.5 deg)

Projections for the future / surge Projections for the future / surge meteorological forcing: HIRHAM / RCAmeteorological forcing: HIRHAM / RCA

Differences in inter-annual percentiles of surge / A2 - CTL: HIRHAM

Differences in inter-annual percentiles of surge / A2 - CTL: RCA

Mean change of winter 95%ile surge levels

Near coastal model cells

SREs emission scenarios: Impact on global sea level

IPC

C, 2

001

According to scenario A2 and the specific set of GCM / RCMs, water level may rise in extreme situations by as much as

40 cm + 30 cm = 70 cm

along the German North Sea coast.

Conclusions• Dynamical models have been demonstrated to be a

useful tool to describe the statistics, and changes thereof, of wind-related phenomena in coastal seas – wind force, storm surge, coastal currents and ocean waves.

• An ensemble of regionalizations, derived from one global A2 scenario, results in rather similar changes of regional wind over the North sea and the associated change of surge levels.

• Along the German North Sea coast, water levels may rise by up to 70 cm - of which 40 cm are due to mean sea level rise and 30 cm to different storm patterns.