Climate change and sediment budgets? Jaak Monbaliu Albin Ullmann

2 Content sediment budget – relevant parameters climate and climate change downscaling: link climate model parameter(s) to impact variables conclusion & further work

3 Sediment budget Natural variability Anthropogenic influence –Coastal safety -> beach nourishment –Aggregate extraction –Dredging / dumping –Construction –....

4 Parameters affecting sediment budgets imposed by nature: –tidal currents –storms -> waves and surges –water depth –sediment composition –.... anthropogenic: – tidal currents – nourishment – D/D – extraction – water depth –...

5 SLRSWHWDIR?? nourishmentHHL? extractionHHL? D/DLLL? Parameters affecting sediment budgets (*) (*) as indication only H : high impact L : low impact

6 Climate Change Scenario A2 : Min. : mm/an Max. : mm/an Scenario B2 : Min. : + 1 mm/an Max. : mm/an Scenario A1b : Min. : mm/an Max. : mm/an IPCC st century mean sea-level rise

7 Climate climate = statistics of weather weather = state of the atmosphere at a particular time “Climate is what you expect, weather is what you get.” quoted from Andreas Sterl, SEAMOCS meeting Malta 2009

8 Climate: downscaling linking weather regimes to events downscaling: statistical model(s) using the downscale model(s) for future predictions

9 Climate: weather regimes 5 weather regimes can summarize the atmospheric circulation over the Northern Atlantic and Europe ZO: « zonal » EA: « East Atlantic » GA: « Greenland Above » BL: « Blocking » AR: « Atlantic Ridge » Mean SLP for each weather regime for the period

10 Mean SLP for daily surge at Oostende > 50 cm ( ) Mean SLP for daily maximum wave height at Westhinder > 2.5 m ( ) deep low pressure system over the Baltic Sea + reinforced Azores high ▼ highest surges and highest waves Belgian coast weather regimes ↕ surges & waves

11 Correlation between daily surge height at Oostende and daily SLP field ( ) Correlation between daily maximum wave height at Westhinder and daily SLP field ( ) At daily time scale, surge and wave height along the Belgian coast are both correlated with sea-level pressure over the Baltic Sea surges and waves: daily variability

12 statistical model surge height = Function_1 (P atm, Baltic, ΔP atm, Baltic-Azores ) wave height = Function_2 (P atm, Baltic, ΔP atm, Baltic-Azores )

13 statistical model regression model + correlation coefficient including gradient information does not improve correlation but... Observed Vs simulated daily surge height. (a) Regression with the daily SLP averaged over the Baltic Sea as predictor. (b) Regression with both daily SLP averaged over the Baltic Sea and the daily value of the pressure gardient between the Baltic and the Azores as predictors R = 0.61

14 R = 0.76 σ obs = 14.2 cm σ sim = 14.8 cm R = 0.72 σ obs = 50.0 cm σ sim = 47.3 cm Monthly 90th percentile of daily wave-height anomaly observed at Westhinder (blue line) and hindcast with the linear statistical model (red line) for the period Monthly 90th percentile of daily surge observed at Oostende (blue line) and hindcast with the linear statistical model (red line) for the period

15 Increase in wintertime P99 of daily maximum sea-level = + 3 mm/yr Increase in wintertime P99 of daily surge = + 1 mm/yr Increase in MSL = + 2 mm/yr (Van den Eynde et al., 2007, CLIMAR annual scientific report) + trend in sea-level and surge

16 MSL rise= mostly link with thermal expension of Seas and Oceans… Wintertime SLP rise over Azores = Increase in the wintertime Northeast- Southwest pressure gradient increase in sea-level and surge …and increase in surge height

17 prediction for the future Essence ensemble dataset: A1B scenario Meteo-France dataset: A2 and B2 scenario

18 yearly 90 th percentile of sea surge for the period for ESSENCE dataset A1b SRES scenario (thin line: mean of ensemble ; full line: 30-year low pass filtered ; grey shading: yearly mean variability in ensemble +/- σ surge-height variability 21 st century

19 yearly 90th percentile of sea surges for the period for A2 (full line) and B2 (dashed line) SRES scenario. surge-height variability 21 st century

20 Conclusion downscaling possible for (some) driving parameters sediment budget from this dataset and climate models !! –no significant changes in surge and wave heights –natural variability within the system is substantial –SLR will be dominant natural factor for changes in the sediment budget

21 Further work link surge / wave /.... to sediment budgets in a robust way for long term and natural variability estimates