NASA-RioUCCRNTrainingPartnership:SeaLevelRise,UrbanHeatIslands,andWaterQuality

SEALEVELRISE—Part2:Futuresealevelandcoastalstormprojections

VivienGornitz andDanielBader

ColumbiaUniversity/NASAGoddardInstituteforSpaceStudies,Tuesday,November15,2016

HistoricalSeaLevelRiseinNYC

2Gornitz, V. Impacts of Sea Level Rise on Coastal Urban Areas

NewYorkCityPanelonClimateChange(NPCC2)§ AfterHurricaneSandy,MayorBloombergconvenedthesecondNewYorkCityPanelonClimateChange(NPCC2),January2013.

§ ClimateRiskInformation2013 providesclimatechangeprojectionsandfuturecoastalfloodriskmapsforNYC’sSpecialInitiativeforRebuildingandResiliency(SIRR).

§ BuildingtheKnowledgeBaseforClimateResiliency. NewYorkCityPanelonClimateChange2015Report.Finalreportincludeslatestfindings.§ AvailableonlineattheNewYorkAcademyofSciences

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Solidearth/gravitation/rotation“Fingerprint”

NYCsealevelchange

Steric/Dynamicoceanchanges

GlacialIsostaticAdjustment

LandWaterStorage

Glaciermassbalance

Icesheetmassbalance

ComponentsofSLRinNPCC2scenarios

Land water storage

Causes of Sea Level Change

Vertical land motions

Mass changes

Thermal expansion

Groundwater mining,impoundment in reservoirs,

runoff, deforestation,seepage into aquifersurban

Subsidence/uplift due toglacial isostatic adjustment,tectonics

Glaciers andice sheets

Ocean water

FingerprintingGravitational, Rotational,

Isostatic

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OverviewofNewNPCC2SeaLevelRiseandCoastalFloodMethodology

• CMIP5GCMsandIPCCRCPscenarios—oceaniccomponents:thermalexpansion(global)anddynamicseaheight(local)

• Updatedratesoficemasslossfromglaciers,smallicecaps,andicesheets(global)

• LatestGIAandgravitational/rotationalcorrections(local)• Landwaterstoragecontributionstosealevelrise(global)• CoupledsealevelriseandFEMAADCIRC/SWANmodelsimulationsoftropicalandextra-tropicalcyclonesfor100-yearfloodzones(local).

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Massredistributionfromicelosscreatesa“fingerprint”

§ AttheBattery:• 1mSLRequivalenticelossfromGreenland=~0.6mSLR• 1mSLRfromAntarctica=~1.2mSLR

740 J. X. Mitrovica et al.

Figure 7. Normalized sea level fingerprints computed using melt models(a) G-U, (b) G-V and (c) their difference (i.e. frame b minus a). The meltmodel G-V is shown in Fig. 6(b).

respectively) the amplitude of the difference is ∼0.4, or 40 per centof the eustatic value. Closer to, but outside Antarctica, the differenceexceeds the eustatic value, and within the melt zone the differencecan be over an order of magnitude greater than the eustatic value.

4 F I NA L R E M A R K S

We have presented a comparative analysis of the sea level finger-prints of rapid ice sheet melting computed using a number of nu-merical methods and based on earth models and sea level theoriesof varying complexity.

As an example, a comparison of a pseudo-spectral calculationof the sea level change in a global (i.e. no continent) ocean due torapid melting of the WAIS with an analytic solution demonstratedthat pseudo-spectral sea level solvers, which are the most commonalgorithms for computing deglaciation-induced sea level change,converge to the correct solution (Fig. 3). Furthermore, we were ableto reproduce to within ∼1 per cent accuracy peak values of the

Figure 8. Normalized sea level fingerprints computed using melt models(a) WA-U, (b) WA-V and (c) their difference (i.e. frame b minus a). Themelt model WA-V is shown in Fig. 6(a).

sea level fingerprint associated with uniform melting of the WAISpublished by Clark & Lingle (1977) for the case of a non-rotating,1-D elastic earth model with fixed, present-day ocean geometry anda Green’s function sea level solver (Fig. 1). The agreement wasevident in comparisons with solutions computed using a pseudo-spectral solver based on both a 1-D Love number formulation anda space-domain solver based on a 3-D finite volume code for pre-dicting the Earth’s elastic response to loading.

One of the most pressing applications of fingerprint studies isthe projection of future sea level changes following the collapse ofexisting reservoirs of ice. We have presented a detailed comparisonof two recent projections involving the potential collapse of theWAIS (Bamber et al. 2009; Mitrovica et al. 2009; Gomez et al.2010) which were based on rotating earth models with evolvingshoreline geometry. The projections by Mitrovica et al. (2009) andGomez et al. (2010) are characterized by a peak far field sea levelamplification relative to the eustatic trend of ∼37 per cent, whichis significantly higher than the 25 per cent amplification factor

C⃝ 2011 The Authors, GJI, 187, 729–742Geophysical Journal International C⃝ 2011 RAS

Greenland Antarctica6

• 24CMIP5GCMs(oceaniccomponents—thermalexpansion,dynamicoceanheight)

• 2IPCCRepresentativeConcentrationPathwayscenarios:RCP4.5andRCP8.5

• 10th,25th,75th,and90th percentilesfrommodel-baseddistribution,literaturesurvey,expertjudgment

• 1ormoregridboxespermodelcoverthestudyarea• Timeslices:2020s,2050s,2080s,2100(10-yearaveragescenteredondecadalmid-point)

• Sealevelriserelativetobaseperiod2000-2004

NewYorkCityPanelonClimateChange,ClimateRiskInformation2013;BuildingtheClimateBaseforClimateResiliency2015 www.nyc.gov/planyc,www.nyc.gov/resiliency,www.ccrun.org,www.cunysustainablecities.org,www.nyas.org/Publications/Annals/

ClimateModelsandEmissionsScenarios

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TreatmentofUncertainty

§ NPCC2uncertaintydistributionsarebasedonrangesofclimatemodeloutputsandliterature-derivedlikelihoodsfordifferentfuturegreenhousegasemissionscenarios

§ Model-basedresultsmaynotencompassthefullrangeofpossiblefutureoutcomes

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Idealizedmodel-basedoutputdistributionfor2050ssealevelriserelativetothe2000-2004baseperiod.Basedon24globalclimatemodelsand2representativeconcentrationspathways.The10th,25th,75th,and90thpercentilesofthedistributionareillustrated.

NPCC, 2015

NewYorkCitySeaLevelRiseProjections(NPCC,2015)

Observedandprojectedsealevelrise,NewYorkCity

Sealevelriseprojectionsbycomponent,2080s(NPCC,2015)

Component Low-estimate MiddleRange High-estimate

LocalOceanHeight+Global

ThermalExpansion

15.4cm 18.1to37.0cm 50.7cm

TotalIceloss(withfingerprint) 7.6cm 14.6to46.7cm 79.0cm

---- GreenlandIce

Sheet

7.6cm 8.8to14.2cm 18.5cm

----WestAntarcticIce

Sheet

2.5cm 3.4to12.9cm 27.1cm

---- EastAntarcticIce

Sheet

-4.5cm -2.9to5.8cm 14.1cm

----GlaciersandIce

Caps

6.6cm 10.6to19.7cm 23.7cm

LandSubsidence 10.5cm 10.5to10.5cm 10.5cm

LandWaterStorage 0.04cm 1.6to5cm 6.5cm

TotalSeaLevelRise 33.5cm 44.7to99.2cm 146.7cm

2080s

Sealevelriseprojectionsbycomponent,2100(Koppetal.,2014)

RCP4.5 2100 0.06--0.15 m (GIC) (5%--95%)0.01—0.10 m (GIS)-0.09—0.38 m (AIS)-0.02—0.63 m (all ice)0.01—0.70 m (all ocean)0.02—0.08 m (LWS)0.12—0.15 m (GIA/tect.)

Total SLR 0.35—1.23 m

RCP8.5 2100 0.09—0.19 m (GIC) (5%--95%)0.02—0.17 m (GIS)-0.12—0.38 m (AIS)-0.01—0.74 m (all ice)0.05—0.98 m (all ocean)

0.02-0.08 m (LWS)0.12—0.15 m (GIA/tect.)

Total SLR 0.44—1.54 m

HistoricalStormsinNewYorkCityArea

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NPCC2CoastalFloodHeightsandRecurrencePeriods

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Annual Likelihood(1%Chance)ofToday’s100-yearflood

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Coastalfloodingisverylikelytoincreaseinfrequency,extent,andheightasaresultofincreasedsealevels

Annual chance of 100-year flood (1%)

Low estimate (10th

percentile)

Middle range (25th to 75th

percentile)

High estimate (90th

percentile) 2020s 1.1% 1.1 – 1.4% 1.5%

2050s 1.4% 1.6 – 2.4% 3.6%

2080s 1.7% 2.0 – 5.4% 12.7%

NPCC2FutureCoastalFloodRiskMaps

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FloodReturnCurves:ComparisonBetweenStaticvsHydrodynamicFloodingMethods

• “FEMA-style”floodhazardassessmentswithsealevelrise—staticvshydrodynamicmodeling

• 100-year,500-yearfloodheights;returnperiods

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Battery

Howard Beach

Midland Beach

IncreasingNewYorkCity’sCoastalResilience

• NewLIDARmappingtoidentifyhighriskflood-proneareas• Incorporatesealevelrisedatainto FEMA’snew100-yearfloodmaps• Adaptexistingstormemergencypreparationstoclimatechange• Improvecoastaldefenses:strengthenandraiseseawalls;buildmoredikes,levees,floodgates

• Raiselandelevation,strengthenbuildingcodes,avoidnewconstructioninflood-proneareas

• Create“softedges” todampenwaveandtideenergy– re-plantnativevegetation;reduceland-seaslope

• Createseriesofparksalongwaterfrontasbufferzones• Restoreorconstructnewwetlandsandoffshorereefs• Widenbeaches,rebuildandre-vegetatebeachdunes.

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‘Hard’CoastalDefenses

20Source: Gornitz (2013); Rising Seas Fig. 8.11

HurricaneIreneovertopsseawall,BatteryParkCity,lowerManhattan

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SeawallconstructioninQueensfollowingHurricaneSandy

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Creatingasoftedgeshoreline,BrooklynBridgePark,NewYorkCity

Source:DepartmentofCityPlanning,CityofNewYorkCity,2011. 23

BrooklynBridgePark,NewYorkCity

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PlannedBermandPark,LowerEastSideofManhattan

BermandSeawall,WestSide,Manhattan

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SaltMarshRestoration,JamaicaBay

27Source: Galvin Brothers, Inc. http://chl.erdc.usace.mil/Articles/7/5/4/JamaicaBay.Grasses.jpg