Reconstruction of the Greenland ice sheet surface mass balance over 1900-2015 with the help of the regional climate MARv3.6 model

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Reconstruction of the Greenland ice sheet

surface mass balance over 1900-2015

with the help of the regional climate MAR model.

X. Fettweis

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_{, C. Agosta}

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_{, H. Gallée}

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1 University of Liège (Ulg), Belgium

2. LGGE, France

Vienna, 20.04.2016

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1. Reanalysis over present climate

ERA-40 (ECMWF) Correction of +1° applied at the MAR boundaries Correction of -1° applied at the MAR boundaries ERA-20C (ECMWF) JRA-55

NCEPv1 NCEPv2 20CRv2(NOAA) 20CRv2c

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1958-2001 1900-2010 1958-2015 1948-2015 1979-2015 ERA-Interim (ECMWF) 1979-2015 1870-2012 1850-2011 Inte rann ual Varia bility (C°)

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2. MAR over present climate

Differences with theDifferences with the ERA-Interim forced

ERA-Interim forced

MAR simulation (mmWE/yr)

Mean SMB (mm/yr) Mean SMB (mm/yr) MARv2 With out c orre ctio n With cor rect ion With out c orre ctio n With cor rect ion 20km

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3. Validation

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From PROMICE data set

Ice cores from Bales et al. (2009)

Bias RMSE Corr.

MAR-ERA 0.14 0.46 0.93 MAR-NCEP1 0.13 0.45 0.93 MAR-20CRv2c 0.14 0.49 0.91 MAR-ERA-20c 0.22 0.52 0.92

MAR vs 1862 SMB observations

over 1958-2010

Biais (mmWE/yr) Regression line

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Surf. pres. 3m-Temperature (°C)

Correlation Correlation Bias RMSE

ERA-Interim 0.99 0.96 -0.29 2.32 -0.65 2.38 NCEP-NCARv1 0.99 0.95 -0.04 2.47 -0.26 2.47 ERA-20C 0.99 0.95 -0.26 2.56 -0.26 2.64 ERA-20C nocorr 0.99 0.95 -1.04 2.76 -1.42 2.94 20CRv2 0.98 0.92 -0.42 3.09 -1.02 3.25 20CRv2c 0.98 0.93 -0.33 3.21 -0.76 3.05 Bias

(summer) (summer)rmse

Comparison with 14 AWSs from PROMICE

(daily measurements over 2008-2010)

3. Validation

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3. Validation

MAR GrIS temperature vs DMI based composite SW Greenland temperature

A nn ua l T em pe ra tu re ( °C ) JJ A T em p. ( °C ) Bad comparison Anomalies in respect to 1980-1999 DMI DMI 1900 1920 1940 1960 1980 2000 warm period of the 1930's Anomalies in respect to 1980-1999

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4. Time evolution

Diverging results ! Diverging results ! Warm period Warm period over Greenland over Greenland Heavier snowfall Heavier snowfall increasing increasing melt melt

Reference period 60-90: high SMB !!

stable stable stable stable 1900 1920 1940 1960 1980 2000 R u n -o ff S n o w fa ll G rI S S M B ( G T /y r) R u n -o ff S n o w fa ll G rI S S M B ( G T /y r)

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Reference period 1980-1999

… by assuming no change in ice dynamics ...

Impact on sea level from 1900 in respect to 1980-1999

4. Time evolution

S e a le ve l c h a n g e (m m ) S e a le ve l c h a n g e (m m )

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Conclusions:

●Good comparison of MAR vs observations + independence of used Good comparison of MAR vs observations + independence of used

reanalysis as forcing.

●Coherent results over 1930-2015. Improvements in reanalyses are needed Coherent results over 1930-2015. Improvements in reanalyses are needed

before 1930!

●GrIS SMB changes have contributed to a GrIS SMB changes have contributed to a see level risesee level rise of ~ 15mm. of ~ 15mm. ●1960-1990 is not a good choice for a reference period.1960-1990 is not a good choice for a reference period.

●Coupling with an ice sheet model to study changes in ice dynamicsCoupling with an ice sheet model to study changes in ice dynamics