3582 
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 observa 
tions 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 dif 
ferences 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 ef 
fects 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 re 
gion were recently reviewed by Wahl et al. (2013). While 
an ongoing sea level rise is evident, changes in atmo 
spheric 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