Compilation  of  Summaries

21

tied  areas,  the  temperature  difference  between  the  warm  surface  layer  and  the
bottom  water  increased  by  approximately  2  К  compared  to  2009.  At  20-30  m,
the  surface  layer  thickness  was  considerably  lower  than  in  the  previous  year
and  the  maximum  gradients  in  the  thermocline  were  also  considerably  lower  at
1.5  К/m.  A  sharp  thermocline  was  only  to  be  found  on  the  55°  N  and  on  the
56°  N  sections  east  of  Dogger  Bank.  Due  to  the  lower  thickness  of  the  surface
layer,  the  cooler  bottom  water  could  cover  a  larger  volume,  meaning  that  the
entire  heat  content  of  the  North  Sea  declined  again  and  was  close  to  the
10-year  average.
The  vertically  mixed  ribbon  of  warm  water  parallel  to  the  continental  coast  continued ­
  to  cool  (approx.  1  K)  in  2011.  In  the  stratified  areas,  the  difference  between ­
  the  warm  surface  layer  and  the  bottom  water  decreased  from  10  К  to
8  К  with  respect  to  2010.  The  maximum  surface  layer  depth  was  40  m;  the
thermocline  gradients  were  between  0.5  and  2.5  К/m.  Compared  to  2010,  the
overall  heat  content  of  the  North  Sea  increased  slightly  and  exceeded  the
10-year  average  by  0.4  standard  deviations.
The  vertical  temperature  distribution  in  the  German  Bight  and  its  evolution
in  time  was  documented  using  data  from  the  station  “German  Bight”  of  the
BSH  Marine  Environmental  Monitoring  Network.  The  positive  anomaly  of  the
2007/2008  winter  minimum  with  a  deviation  of  approximately  2  К  as  a  result  of
the  heat  surplus  from  the  preceding  summer  and  autumn  months  was  one  of
the  dominant  signals  in  the  reporting  period.  The  winter  minima  came  closer  to
the  climatological  values  again  in  the  winter  of  2008/2009.  The  summer  maxima ­
  of  the  daily  averages  are  up  to  3  К  above  the  climatology.  The  stratification
was  particularly  pronounced  in  2010.  The  surface  and  bottom  temperature  differences ­
  measured  up  to  8  K,  while  the  seasonal  maximum  was  reached  in  the
surface  layer  approximately  6  weeks  before  that  of  the  bottom  layer.  The  pronounced ­
  stratification  was  caused  by  the  unusually  high  atmospheric  heat  inputs ­
  in  April  2010  and  the  following  summer.  In  2011,  the  summer’s  solar  radiation ­
  gains  were  significantly  lower  than  the  long-term  average.  This  led  to  a
lower  summer  maximum  and  a  weakly  developed  stratification.

Salinity  (Page  Seite  134  et  seq.)
In  summer  2008,  the  second-highest  total  salt  content  since  1999  was  recorded ­
  with  2004  at  maximum.  During  winter  2008  Atlantic  Water  (AW  S  >  35)
penetrated  from  the  northern  boundary  southwards  until  56°  N  in  the  bottom
and  surface  layer.  In  the  summer,  the  35  isohaline  in  the  bottom  layer  ran
roughly  along  the  57°  N  parallel  and  AW  with  S  >  35.35  penetrated  southwards
down  to  58°  N  in  a  broad  tongue  and  covered  a  considerably  larger  volume
than  during  the  previous  year.  At  the  surface,  the  area  with  AW  only  covered  the
area  north  of  57°  N  and  west  of  the  prime  meridian.
In  the  winter  of  2009,  the  AW  advanced  southwards  down  to  55°  N  in  the  entire
water  column.  At  the  same  time,  a  large,  lens-shaped  body  of  AW  was  located
in  the  inflow  area  of  the  Channel.  During  the  summer  period,  the  tongue  of  AW
reached  still  southwards  until  approximately  56°  N,  but  was  significantly  narrower ­
  at  the  surface  than  during  winter.  The  total  salt  content  decreased  slightly
in  comparison  to  the  previous  year.  In  2008  and  2009,  the  total  volume  of  water