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JOURNAL  OF  CLIMATE

Volume  27

North  Sea  Storminess  from  a  Novel  Storm  Surge  Record  since  AD  1843*
Sönke  Dangendorf, +  Sylvin  Müller-Navarra, #  Jürgen  Jensen, +
Frederik  Schenk,®  Thomas  Wahl, &  and  Ralf  Weisse**
+  Research  Institute  for  Water  and  Environment,  University  of  Siegen,  Siegen,  Germany
*  German  Maritime  and  Hydrographic  Agency  (BSH),  Hamburg,  Germany
®  Institute  for  Coastal  Research,  Helmholtz  Zentrum  Geesthacht,  Geesthacht,  Germany,  and  Linné
Flow  Centre,  Department  of  Mechanics,  Royal  Institute  of  Technology,  Stockholm,  Sweden
&  College  of  Marine  Science,  University  of  South  Florida,  St.  Petersburg,  Florida,  and  Research
Centre  Siegen  (FoKoS),  University  of  Siegen,  Siegen,  Germany
**  Institute  for  Coastal  Research,  Helmholtz  Zentrum  Geesthacht,  Geesthacht,  Germany

(Manuscript  received  19  July  2013,  in  final  form  6  January  2014)
ABSTRACT
The  detection  of  potential  long-term  changes  in  historical  storm  statistics  and  storm  surges  plays  a  vitally
important  role  for  protecting  coastal  communities.  In  the  absence  of  long  homogeneous  wind  records,  the
authors  present  a  novel,  independent,  and  homogeneous  storm  surge  record  based  on  water  level  observations ­
  in  the  North  Sea  since  1843.  Storm  surges  are  characterized  by  considerable  interannual-to-decadal
variability  linked  to  large-scale  atmospheric  circulation  patterns.  Time  periods  of  increased  storm  surge  levels
prevailed  in  the  late  nineteenth  and  twentieth  centuries  without  any  evidence  for  significant  long-term  trends.
This  contradicts  with  recent  findings  based  on  reanalysis  data,  which  suggest  increasing  storminess  in  the
region  since  the  late  nineteenth  century.  The  authors  compare  the  wind  and  pressure  fields  from  the
Twentieth-Century  Reanalysis  (20CRv2)  with  the  storm  surge  record  by  applying  state-of-the-art  empirical
wind  surge  formulas.  The  comparison  reveals  that  the  reanalysis  is  a  valuable  tool  that  leads  to  good  results
over  the  past  100  yr;  previously  the  statistical  relationship  fails,  leaving  significantly  lower  values  in  the  upper
percentiles  of  the  predicted  surge  time  series.  These  low  values  lead  to  significant  upward  trends  over  the
entire  investigation  period,  which  are  in  turn  supported  by  neither  the  storm  surge  record  nor  an  independent
circulation  index  based  on  homogeneous  pressure  readings.  The  authors  therefore  suggest  that  these  differences ­
  are  related  to  higher  uncertainties  in  the  earlier  years  of  the  20CRv2  over  the  North  Sea  region.

1.  Introduction
Storm  surges  represent  a  serious  hazard  for  coastal
areas  and  are  expected  to  become  more  severe  in  a
warming  climate  (von  Storch  2014)  because  of  the  effects ­
  of  rising  mean  sea  level  (MSL;  Slangen  et  al.  2012)
and  potential  changes  in  regional  wind  fields  (Woth  et  al.
2006).  Global  MSL  has  risen  through  the  last  century
(e.g..  Church  and  White  2011)  and  is  expected  to  rise

*  Supplemental  information  related  to  this  paper  is  available  at
the  Journals  Online  website:  http://dx.doi.org/10.1175/JCLI-D-13-00427.S1.


Corresponding  author  address:  Sonke  Dangendorf,  Research
Institute  for  Water  and  Environment,  University  of  Siegen,  Paul-Bonatz-Str.
  9-11,  57076  Siegen,  Germany.
E-mail:  soenke.dangendorf@uni-siegen.de
DOI:  10.1175/JCLI-D-13-00427.1

also  through  the  twenty-first  century,  potentially  at  an
accelerated  rate  (e.g.,  Slangen  et  al.  2012),  shifting  the
entire  distribution  of  extreme  sea  levels  on  a  higher  base
level  (Hunter  2010).  MSL  changes  in  the  North  Sea  region ­
  were  recently  reviewed  by  Wahl  et  al.  (2013).  While
an  ongoing  sea  level  rise  is  evident,  changes  in  atmospheric ­
  circulation  and  storminess  are  presently  more
uncertain  (Weisse  and  von  Storch  2010,  and  references
therein).  This  is  partly  because  the  detection  of  past
changes  in  storminess  is  often  hampered  by  inhomogeneous
or  biased  wind  measurements  (e.g.,  Lindenberg  et  al.
2012).  Hence,  the  scientific  community  proceeded  to  the
evaluation  of  more  homogeneous  storminess  proxies,
which  have  been  observed  over  longer  time  periods.
Typical  examples  for  such  proxies  are  storm  indices
calculated  from  single  station  pressure  readings  (e.g..
Barring  and  von  Storch  2004;  Hanna  et  al.  2008),  high
annual  percentiles  of  geostrophic  winds  derived  through

©  2014  American  Meteorological  Society