North Atlantic Wave Heights 2070-2100 · 2019-09-27 · North Atlantic wave height climate towards...

North Atlantic wave height climate towards the end of the21st century

Øyvind Breivik, Ole Johan Aarnes and Magnar Reistad

RCP85-HISTORIC: annualmean

-10

-8

-6

-4

-2

0

2

4

6

8

10

[%]

Ø Breivik et al (MET Norway) North Atlantic Wave Heights 2070-2100 26 September 2018 1 / 14

Outline of presentation

CMIP5 climate projectionsExperiment setupWave model setupTrends in mean and upper percentilesChanges in extremesConclusions and further work


Motivation

CMIP5 models in general do not incorporate wave models, but there is aclear need for estimates of how the wave climate may change in the future

for existing petroleum installations

future offshore wind and wave installations... and because it is a scientific question that needs to be answered


Motivation


for existing petroleum installationsfuture offshore wind and wave installations

... and because it is a scientific question that needs to be answered


Motivation


for existing petroleum installationsfuture offshore wind and wave installations... and because it is a scientific question that needs to be answered


CMIP5 scenarios

RCP4.5 (Representative Concentration Pathway to 4.5 W/m2

radiative forcing)

RCP8.5 (8.5 W/m2 radiative forcing)

Source: Wikipedia (Creative Commons Licence)


CMIP5 scenarios

RCP4.5 (Representative Concentration Pathway to 4.5 W/m2

radiative forcing)RCP8.5 (8.5 W/m2 radiative forcing)

Source: Wikipedia (Creative Commons Licence)


CMIP5 models

Model Res (lon/lat) Hist # Future #GFDL-CM3 2.5◦ ×2.0◦ 1970-1999 1 2071-2100 1EC-Earth 1.125◦ ×1.125◦ 1971-2000 3 2071-2100 3MRI-CGCM3 1.125◦ ×1.125◦ 1971-2000 2 2071-2100 1MIROC5 1.4◦ ×1.4◦ 1971-1999 5 2070-2099 3IPSL-CM5A-MR 2.5◦ ×1.25◦ 1971-1999 3 2071-2099 1HadGEM2-ES 1.875◦ ×1.25◦ 1970-1999 1 2081-2099 1


Wave model integrations

The WAM wave model was set up on a domain with 50 km spatialresolution, covering the North Atlantic. Wave fields are output with3-hourly temporal resolution.The wind forcing was interpolated from CMIP5 10-m wind fieldsIce cover was changed once a month based on CMIP5 iceconcentration


Assessing the historical runs

The wave model integrations were compared against the NORA10hindcast archive (Reistad et al, 2011).


Standardising climate projections against historical runsCMIP5 models yield widely different historical wave climate both in termsof bias and activity (variance).

In order to compare their future wave climate, the wave model projectionshad to be standardised against their historical counterparts

H(Hist,RCP)s,annual −HHist

s,annual

std(HHists,annual)

. (1)


Comparison of historical runs against a hindcast


Standardised annual mean, RCP4.5 and RCP8.5


-10

-8

-6

-4

-2

0

2

4

6

8

10

[%]


-10

-8

-6

-4

-2

0

2

4

6

8

10

[%]

-10 -5 0

Historic standardized

-10

-8

-6

-4

-2

0

2

4

Fu

ture

sta

nd

ard

ize

d

QQ-annualmean: HIST vs FUTURE

RCP45

RCP45 - mean

RCP85

RCP85 - mean

Quantile-quantile distribution of annual mean for a location in the NorthAtlantic (right panel) reveals that RCP8.5 has larger variance thanRCP4.5, but lower overall mean. Both have higher variance than thehistorical climate (x -axis).


Standardised annual 99 percentiles, RCP4.5 and RCP8.5

RCP45-HISTORIC: annualp99

-10

-8

-6

-4

-2

0

2

4

6

8

10

[%]

RCP85-HISTORIC: annualp99

-10

-8

-6

-4

-2

0

2

4

6

8

10

[%]

-5 0 5


-8

-6

-4

-2

0

2

4

6

Fu

ture

sta

nd

ard

ized

QQ-annualp99: HIST vs FUTURE

RCP45

RCP45 - mean

RCP85

RCP85 - mean

This tendency is also seen towards the upper percentiles (see right panel),but their overall mean is now more similar.


Standardised annual maxima, RCP4.5 and RCP8.5

RCP45-HISTORIC: annualmax

-10

-8

-6

-4

-2

0

2

4

6

8

10

[%]

RCP85-HISTORIC: annualmax

-10

-8

-6

-4

-2

0

2

4

6

8

10

[%]

-5 0 5


-5

0

5

Fu

ture

sta

nd

ard

ized

QQ-annualmax: HIST vs FUTURE

RCP45

RCP45 - mean

RCP85

RCP85 - mean

The annual maxima are quite similar for RCP4.5 and RCP8.5, but bothexhibit larger variance than the historical annual maxima.


Conclusions

1 Annual mean wave height appears to decrease toward the end of thecentury in the North Atlantic, and more so for RCP8.5 than forRCP4.5

2 Upper percentiles decrease less, suggesting that the variance increaseswhile the mean goes down

3 All models show increased wave heights in the Norwegian Sea due toreceding winter ice cover


Open questions

1 Are we moving toward a future wind and wave climate with highervariance but lower mean values in the extratropics?

2 Can we continue to justify running climate GCMs without a wavemodel component?

3 Will the inclusion of a wave model modify the results appreciably?4 In particular, can the extremes be affected by an active wave model?

References:Aarnes, O. J., M. Reistad, Ø. Breivik, E. Bitner-Gregersen, L. I. Eide, O. Gramstad, A. K. Magnusson, B. Natvig and E.Vanem, 2017. Projected changes in significant wave height towards the end of the 21st century: Northeast Atlantic, JGeophys Res: Oceans, 122, pp 3394-3403, doi:10.1002/2016JC012521Aarnes, O. J., Ø. Breivik, and M. Reistad, 2012: Wave Extremes in the Northeast Atlantic. J Climate, 25, 1529–1543,doi:10/bvbr7kAarnes, O. J., S. Abdalla, J.-R. Bidlot, and Ø. Breivik, 2015: Marine wind and wave height trends at differentERA-Interim forecast ranges. J Climate, 28, 819–837, doi:10.1175/JCLI-D-14-00470.1.Breivik, Ø., O. J. Aarnes, J.-R. Bidlot, A. Carrasco, and Ø. Saetra, 2013: Wave Extremes in the Northeast Atlanticfrom Ensemble Forecasts. J Climate, 26, 7525–7540, doi:10/mpf.Reistad, M., Ø. Breivik, H. Haakenstad, O. J. Aarnes, B. R. Furevik, and J.-R. Bidlot, 2011: A high-resolution hindcastof wind and waves for the North Sea, the Norwegian Sea, and the Barents Sea. J Geophys Res, 116, 18 pp, C05 019,doi:10/fmnr2m


North Atlantic Wave Heights 2070-2100 · 2019-09-27 · North Atlantic wave height climate towards...

Documents

Transcript of North Atlantic Wave Heights 2070-2100 · 2019-09-27 · North Atlantic wave height climate towards...