Analysis  of  the  Ice  Model  Simulation  for  the  Gulf  of  Finland  In  2002/2003

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Analysis  of  the  Ice  Model  Simulation  for  the  Gulf  of  Finland  in
2002/2003
Ove  Pärn*,  Jari  Haapala+,
*  Systems  Institute  at  Tallinn  Technical  University,  Estonia,  Email  ove@sea.ee
+  Finnish  Institute  of  Marine  Research,  Finland,  Email  iari.haaDala@fimr.fi

Abstract
In  this  study  we  have  analysed  the  multi-category  sea-ice  model  (FIELMI)  results  in  order  to
examine  characteristics  of  deformation  in  Gulf  of  Finland.  We  investigated  how  the  increase  of
deformed  ice  is  related  to  wind  speed  and  direction  and  how  the  ice  conditions  varies  in  space
and  time.
Background
The  seasonal  ice  cover  is  of  great  importance  to  the  countries  surrounding  the  Baltic  Sea,  as
year-round  navigation  is  essential  for  the  national  economies  in  these  countries.  The  Gulf  of
Finland  is  an  important  corridor  for  Russian,  Finland  and  Estonian  shipping.  In  winter  vessels
must  navigate  through  the  ice,  in  normal  winter  at  last  150  nautical  miles  and  maximum  sailing
distance  to  the  ice-edge  was  400  nautical  mile  in  1961-1990  (Seina  2003).
The  first  ice  forms  on  the  Gulf  of  Finland  at  the  beginning  of  December  and  breaks  up  in  the
end  of  April.  The  thickness  of  undeformed  ice  in  the  Gulf  of  Finland  may  reach  0.8  m  in  the  fast
ice  but  in  the  pack  ice  region  the  thickness  of  level  ice  seldom  exceeds  0.5  m,  and  ice  ridges
are  typically  5-10  m  thick.
During  an  average  winter  the  whole  northern  Baltic  Sea  is  ice  covered.  Even  in  a  mild  winter  on
the  Gulf  of  Bothnia,  Gulf  of  Finland  and  Gulf  of  Riga  appears  the  ice.  Sea  ice  is  important
because  it  regulates  exchanges  of  heat  and  salinity  in  the  sea.  The  sea  ice  affects  both  human
activities  and  biological  habitats.
Deformation  of  sea  ice  is  a  key  process  determing  the  evolution  of  the  sea-ice  thickness
distribution.  Apparent  results  of  the  deformation  are  leads  and  ridges.  Recent  observations  of
the  thickness  by  Flans  (2004)  have  reveled  that  the  mean  ice  thickness  over  several  km 2 !!
could  be  2-3  meters  in  the  Gulf  of  Finland.  In  this  study  we  have  analysed  the  multi-category
sea-ice  model  (FIELMI)  results  in  order  to  examine  characteristics  of  deformation  in  the  Gulf  of
Finland,  and  have  investigated  how  the  increase  of  deformed  ice  is  related  to  wind  speed  and
direction  and  how  the  ice  conditions  varies  in  space  and  time.
Model  Description
The  FIELMI  model  is  a  multicategory  sea-ice  model  developed  originally  for  the  climate
research  (Flaapala  et  al.,  2005).  The  model  physics  and  numerics  are  same  both  in  operational
and  climate  simulations.  The  only  differences  are  in  the  horizontal  resolution  and  atmospheric