Permafrost methane emission modeling Yanjiao Mi, Department of Hydrology and Geo-Environmental Sciences, Vrije Universiteit

Kytalyk,   Northeast   Siberia,   arc3c   tundra,   silt  and   clay   deposits,   ice-­‐rich,   'Yedoma’,   large  thaw   lakes   and   many   drained   lake   basins,  mean  annual  air  temperature    -­‐  14.3oC,  mean  July   temperature   9.5   oC,   annual   precipita3on  232  mm,  con3nuous  permafrost  

Test  site  Permafrost methane CH4: global warming potential of 62 based on 20 years time horizon

A considerable amount of organic carbon is stored in the upper permafrost layers

The positive temperature trend make permafrost a large carbon source

Permafrost 24% of the northern circumpolar region

Home to more than 4 million people

Sensitive to climate change (environment, resources, food…)

Tundra  emission Methane  emission  modeling:     Peatland-VU LPJ-WhyMe

Hydrological  modeling:     Flood plain Ground water position

Thaw  lake  emission Thaw  lake  model  

Max  frac3on  thawing  grid  cells  

thawing  cells  >  high  ice  cells  fthaw>fminthaw

Number  of  thawing  grid  cells  Nthaw  depends  on  fminthaw

Randomized  selec3on  of  Nthaw  highest  ice  content  cells  

Number  of  thawing  grid  cells  Nthaw  depends  on  fthaw

Select  all  cells  with  ice  content  I > Iminthaw

Lake  ini3a3on  

Thaw  cells  depending  on  ice  content  

no   yes  

July  temperature  anomaly  Tdiff,t

Precipita3on  anomaly  Pdiff,t

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fthaw = Tdiff , t ⋅ MT + Pdiff ⋅ Mp

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Li, j , t = Li, j , t−1 + Lnew, i, j , t

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Lnew, i, j , t = LMax ⋅ Ii, j, t

Ini3al    thaw  par3al  thawing   no  thaw  

Growth  of  ice  content  based  on  current  ice  content  and  mean  annual  air  temperature  

Thaw  >  threshold?  

Cell  is  added  to  to  lake  cells  

Expansion  rate:  summer  temperature,  precipita3on,  ice  content  

Cell  next  to  drainage  cell?  

Cell  added  to  drained  system  Ice  content  set  to  minimum  

Drainage  cell  with    Ice  content  >    frost  heave  limit?  

Cell  removed    from  drainage  system  

Cell  next  to  lake  cell?  

Dominant  wind  direc3on:  modify  thaw  threshold  

Isolated  land  cell  random  erosion  

Next  3me  step  

yes  no  

no  yes  

yes  

no  

yes   no  

yes  no  

Lake  expansion   Drainage  and  refreezing  

Thawed  frac3on  >  threshold  

yes  €

Tdiff , t > a, Pdiff , t > 0

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Lmax exp, t = b(Tdiff , t −a)+cPdiff , t

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Li, j , t = Lmax exp, t ⋅ Ii, j , t +Li, j , t−1

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d = cos(W +G) ⋅ L⋅ Fw

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Ld = (max(d) − d) /Fw + d

no  

Temporal  dynamics   Spa7al  pa8ern  

Modelled  thawed  and  drained  area:  Ini3al  peak  of  lake  area  followed  by  rapid  drainag,  thereaYer  oscilla3ons   Thaw  lake  area:  similar  to  terrain  inves3ga3on  

More  rapid  lake  development  with  high  lake  ini3a3on  rate  but  unrealis3c  morphology  

Thaw  lake  model  test  

       Integrated  100  years    Max  100  years                                                                          A2                  B1                A2                                B1  

Lake  area  frac7on  HadCM3      18.23±0.22  18.77±0.18  0.26±0.02  0.27±0.03  ECHAM5    17.23±0.22  18.01±0.27  0.24±0.03  0.25±0.04  NOAA  GFDL2.1                              16.55±0.13  15.66±0.08  0.25±0.03  0.25±0.02  CSIRO  Mk3.5                              16.17±0.20  16.75±0.25  0.24±0.03  0.25±0.03  NCAR      15.33±0.23  16.30±0.26  0.26±0.03  0.25±0.03  INMCM                                16.40±0.23  16.26±0.23  0.24±0.03  0.24±0.02

Implica7on  methane  emission  (gm-­‐2  yr-­‐1)  HadCM3      2.09±0.01  2.30±0.01  3.76±0.10  3.97±0.15  ECHAM5    1.88±0.01  2.09±0.02  3.34±0.15  3.55±0.20  NOAA  GFDL2.1                              1.88±0.01  1.67±0.01  3.55±0.15  3.55±0.10  CSIRO  Mk3.5                              1.67±0.01  1.88±0.01  3.34±0.15  3.55±0.15  NCAR      1.46±0.01  1.67±0.02  3.76±0.15  3.55±0.15  INMCM                                1.67±0.01  1.67±0.01  3.34±0.15  3.34±0.10

Thaw  lake  model  results  

Sensi7vity  experiments  

Experiments  with  6  climate  model  predic7ons  21th  century  SRES  A2  and  B1  scenarios  

Varying  temperature  and  precipita3on  output  of  the  climate  models  

Maximum  lake  area  ±  25%  

Most  models  result  in  decrease  of  lake  area    aYer  ±70  years  by  increased  lake  drainage  

Half  of  the  model  runs  predict  lower  lake  area  by  2100  

Small  temperature  and  precipita3on    increase  (NOAA  GFDL  model):  largest  cumula3ve  lake  area  

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Tann, t ≤ Tfreeze Iadd = (Imax − Ii, j, t )⋅ IgrowTann, t > Tfreeze Iadd = 0