First CLISAP/KlimaCampus Workshop on Sea Level Variability and Change 27 May, 2013

1. Regional issues of changing storm surges and sea level - what is done at the Institute for Coastal Research @ HZG First CLISAP/KlimaCampus Workshop on Sea Level Variability and Change 27 May, 2013

2. Institute of Coastal Research @ HZG • The Institute of Coastal Research deals with the issue of long-term change of the geophysical coastal environment, mainly in the North Sea and Baltic Sea. • Long term = several decades, homogeneous qualityinto the past, mainly 1948 onwardsas projections into the future: until 2100 • Parameter: Sea level, storms, surges, waves, currents • Researchers: Ralf Weisse, Frauke Albrecht, Iris Grabemann, Lidia Gaslikova, Hans von Storch, Katja Worth (North Sea) and Iris Grossmann (Elbe)Eduardo Zorita, Birgit Hünicke (Baltic Sea) • In cooperation with BALTEX, TU Siegen, FSK Norderney, BAW, KLIFF, U Szczecin and others

3. North Sea • Usage of CoastDat data set, a downscaling effort, using a cascade of- NCEP/NCAR reanalysis (beginning in 1948), - CLM-atmospheric LAM (earlier REMO) forced with spectral nudging, - dynamical models of hydrodynamics and waves (with BAW)- empirical models for estimating local changes (Elbe) • Analysis of homogenized sea level data (in cooperation with U Siegen) • Discussion of significance of results of coastal defense planning with various stakeholders with responsibility for the North Sea coast; part of AKÜST-KLIFF assessment of different adaptation strategies to increasing extreme sea levels; operationalization in www.kuestenschutzbedarf.de by Norddeutsches Klimabüro • Usage of estimates for commercial applications, in particular planning for wind farming, shipping and other cases.

4. Mean and extreme sea level changes Temporal development of intra-seasonal 99%ile of high tide levels AFTER subtraction of annual mean high tide and mean annual high tide in Esbjerg (Denmark) and Den Helder (The Netherlands) until 1995. Sea level changes different at different locations, because of different drivers, and different dynamics.

5. Mean sea level changes in the German Bight RMSL from different methods • black – VM method (Wahl et al. 2011); green – EOF method (Albrecht et al. 2011) • Different methods yield comparable results after 1924 • For this time interval there is little difference between VM and EOF approach correlation 0.996; trends 1.64 mm/yr (VM) 1.74 mm/year (EOF)

6. Regionale Meeresspiegeltrends 37-jährige Trends des regionalen Meeresspiegels schwarz – VM Methode; grün – EOF Methode; rot – Cuxhaven • Beschleunigung des (globalen) Meeresspiegelanstiegs? • Verschiedene Methoden führen zu ähnlichen Ergebnissen • Gegenwärtige dekadische Trends sind relativ hoch • Aber nicht ungewöhnlich im Vergleich zu früheren Perioden (Albrecht et al. 2011)

7. Extreme sea level changes • Extreme sea levels increased over the past 100-150 years in the North Sea • Primarily as a result from a rise in mean sea level • Meteorologically induced components (waves, storm surges) show pronounced variation on time scales of years and decades but no substantial long-term trend • Variations in storm surge and wave climate consistent with those in storm activity over the North Sea Annual mean high water and linear trend 1843-2012 at Cuxhaven, Germany (bottom) and corresponding difference between annual 99-percentile and annual mean high water levels (top); In addition an 11-year running mean is shown in the upper panel.

8. The case of the Elbe and Hamburg

9. Storm surges in Hamburg in the past Differenceofmaximumheights in Hamburg and Cuxhaven Storm surges in Hamburg elevatedbecauseofmodifyingtheriver Elbe – bothcoastaldefenseandshippingchanneldeepening

10. Possible and plausible future changes in regional storm surge climate • Changes in extreme storm surge levels 2071-2100 ./. 1961-1990 • (Woth et al. 2006; Woth 2005)Here 99.5 percentile based on half hourly values; this compares to 99 percentiles derived from hourly valuesContour lines show 99.5 percentile storm surge residuals from respective control runs

11. Future changes in regional storm surge climate • A1B B2 1.Realisation 2.Realisation After Gaslikova et al. 2012

12. Projected changes in storm surges in the German Bight Maximum changes along the German Bight coast at the end of the 21st century

13. Summary of knowledge about change of storm surge heights (per 2009) See: GKSS, 2009 : Nordseesturmfluten im Klimawandel .GKSS Wissenschaftler fassen aktuellen Forschungsstand zusammen.

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18. Hünicke, 2012 Maps in the Internet highly misleading …

19. Baltic Sea 300 300 200 200 100 100 0 0 -100 -100 -200 -200 -300 -300 1800 1850 1900 1950 2000 1800 1850 1900 1950 2000 STOCKHOLM 300 200 KRONSTADT 100 300 0 200 SWINOUJSCIE KOLOBRZEG -100 100 0 -200 -100 -300 1800 1850 1900 1950 2000 -200 -300 1800 1850 1900 1950 2000 Hünicke, 2012 Winter (DJF) Anomalien Ekman (2003) Zeitserien beinhalten Trend verursacht durch post-glaziale Landhebung und evtl eustatischen Meeresspiegeländerungen Bogdanov et al. (2000) PSMSL* (2005) PSMSL*, TU Dresden (2005) * Permanent Service for Mean Sea Level (Woodworth and Player, 2003)

20. Glacial isostatic vertical movement To get the relative sea level change, the crustal movement has to be subtracted. Tis movement is in the Baltic Sea region very strong as a response of the melting of the earlier ice sheets. 9 5 0 -1 mm/year Rosentau et al., 2007 Hünicke, 2012

21. Gauge series -detrended 300 300 200 200 100 100 0 0 -100 -100 -200 -200 -300 -300 1800 1850 1900 1950 2000 1800 1850 1900 1950 2000 STOCKHOLM 300 300 200 200 KRONSTADT 100 100 0 0 SWINOUJSCIE KOLOBRZEG -100 -100 -200 -200 -300 -300 1800 1850 1900 1950 2000 1800 1850 1900 1950 2000 Hünicke, 2012 Winter (DJF) Anomalien Ekman (2003) Trend wird als linear angenommen und durch subtrahieren des linearen Langzeit-Trends von jeder Wasserstands-Zeitserie abgezogen Bogdanov et al. (2000) PSMSL* (2005) PSMSL*, TU Dresden (2005) * Permanent Service for Mean Sea Level (Woodworth and Player, 2003) 3. Datensätze

22. SL SLP SLP + precipitation SLP+ precip+temp mm Stockholm Stockholm Stockholm 80 60 40 20 0 -20 -40 -60 RE: 0.57 RE: 0.48 RE: 0.81 -80 Warnemünde Warnemünde Warnemünde 80 60 40 20 0 -20 -40 -60 RE: 0.56 RE: 0.11 RE: 0.67 -80 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 1900 1920 1940 1960 1980 2000 Recorded sea level after subtraction of linear trendEstimated trends, using SLP „ + precipitation „ + „ + temperature Variations of relative sea level in DJF Observations and estimates by regression RE – relative error invalidation period (1900-1950) Hünicke, 2012

23. Summary for Baltic Sea • The observational record discloses clear long-term variations, mostly uniform in the Baltic Sea Basin during the 20th century. • The atmospheric circulation has a significant influence on the variations of sea level in the Baltic Sea. The NAO is an important contributor, but only part of the forcing. • Additionally, precipitation and temperature variations relate to variations of regional sea level, in particular in summer. • Determination of long-term trends beyond glacio-isostastic rebound is difficult to achieve, as the space-time pattern of the rebound is qualitatively similar to the expected climate change signal. • Work done by Birgit Hünicke. Hünicke, 2012

24. Overall summary • The Institute of Coastal Research is engaged in describing geophysical change of the environment in the North Sea and Baltic Sea regions. • Efforts are underway to build homogeneous data sets (CoastDat) describing this past and current change, as well as possible and plausible changes in the future (next 100 years; climate) • Efforts are underway to determine the most plausible mix of drivers behind tehse changes. • The results are brought into the science-stakehodler interaction of HZG and CLiSAP. • About 10 people involved in the ongoing work, which is associated both with CLiSAP as well as the HGF-programme PACES with AWI.