1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland)

1. Information contained within this presentation is from a currently unpublished thesis, and should not be used or referenced without the expressed permission of the authors

2. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) Alex Wright & Dr. Orson van de Plassche

3. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) RELATIVE SEA-LEVEL: SEA-LEVEL VARIABILITY: with trends trends removed

4. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) NH TEMPERATURES:SEA-LEVEL VARIABILITY: Mann et al. (2003 trends removed

5. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) (BRIEF) TALK OUTLINE CONCEPT: Sea-level from salt-marshes METHODOLOGY: 5 Steps sea-level reconstruction, with examples (RESULTS & DISCUSSION) SUMMARY: Conclusions

6. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) CONCEPT: SALT-MARSHES • Coastal wetlands • Upper half tidal range (MTL-HHW)

7. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) CONCEPT: SALT-MARSHES AND SEA-LEVEL • Surface vertically accretes - maintain position with rising sea level • Sedimentary archive of palaeomarsh surfaces (PMS)

8. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) CONCEPT: VERTICAL DISTRIBUTION OF FORAMINIFERA • Tidal inundation - strong environmental gradient - vertical distribution flora / fauna (MHW) • Foraminifera occupy narrower vertical ranges • More precise indicators of PRESENT and PAST marsh surface height (MHW)

9. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY: 5 STEPS TO SEA-LEVEL RECONSTRUCTION 1) Height PMS’s formed (relative to PMHW) 2) Time the PMS’s formed 1) + 2) = Relative PMHW 3) Sediment compaction correction 4) Palaeotidal range correction + 3) + 4) = Relative PMTL 5) Detrend millennial scale relative sea level (GIA) + 5) = PMTL

10. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:1) Height PMS’s formed (relative to PMHW) • Establish contemporary vertical foraminifera distribution • Sample heights known (MHW) – TRANSFER FUNCTION foraminifera-surface height • QUANTITATIVE PMS height reconstruction from FOSSIL foraminifera

11. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:1) Height PMS’s formed (relative to PMHW) • Palaeo-record from core salt-marsh peat

12. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:1) Height PMS’s formed (relative to PMHW) • Every (other) cm - assumed PMS • Analyze for fossil foraminifera content

13. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:1) Height PMS’s formed (relative to PMHW) • TRANSFER FUNCTION - PMS heights (PMHW) • Variability from rate PMS accumulation or PMHW rise? • PMS accumulation rate - CHRONOLOGY!

14. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:2) Determine time at which PMS’S formed • Resample for datable PMS indicators • Last ~200 yrs date sediment - HIGH PRECISION • Remainder data 14C of organics – LOW PRECISION

15. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:2) Determine time at which PMS’S formed • PRECISION differences clear from age-PMS depth envelope • High resolution sampling CHECKS record completeness

16. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) RECONSTRUCTIONS:

17. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:2) Determine time at which PMS’S formed • CHALLENGE - Define within envelope PMS accumulation rate • EXAMPLE - 2 LINEAR rates

18. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:2) Determine time at which PMS’S formed • Illustrate importance…….

19. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY: COMBINE 1) + 2) = Relative PMHW • PMS accumulation rate - PMS height variability due to PMHW • Correct? Cannot resolve at this scale • Combined - PMS accumulation rate defines (MULTI-)CENTENNIAL VARIABILITY

20. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY: COMBINE 1) + 2) = Relative PMHW reconstruction • AGAIN - PMS accumulation rate defines (MULTI-)CENTENNIAL VARIABILITY • Last ~200 yrs high precision chronology - constrains PMS • Enables VALIDATION with instrumental records…..EXTENSION? (GEHRELS)

21. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) SUMMARY:

22. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:3) Sediment compaction correction • COMPACTION – (post-depositional process) alters original PMS elevation • CORRECTION APPLIED - LINEAR PMHW becomes CURVED decreasing trend • (NON-)CORRECTION – impacts MULTI CENTENNIAL TRENDS

23. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:3) Sediment compaction correction • CALCULATION? Comparison with basal reconstructed PMHW

24. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:4) Palaeotidal range correction, COMBINE 3) + 4) = Relative PMTL • Rising relative sea level - coastline morphology - tidal range changes • Solved with modeling - relative PMHW can infer relative PMTL

25. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) METHODOLOGY:5) Detrend (GIA), COMBINE 5) = PMTL • Reconstructed MTL once MILLENNIAL relative rise removed • Past 1500 yr due to GIA? (assuming no SL trend) • SCENARIO 1 / 2, extent to which SL is STABLE / RISING / FALLING • Preferably long BASAL series with model prediction

26. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) SUMMARY:

27. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) RESULTS / DISCUSSION: Summary assessment of reconstructions

28. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) RESULTS / DISCUSSION: Summary assessment of reconstructions • Falling SL trend? inc. ~1800 • High freq. variability • Falling SL trend & oscillation? inc. ~1900 • Falling SL trend? inc. ~1800 / ~1900 • inc. ~1900 • High freq. variability, inc. ~1700 / ~1900 • EROSION • EROSION • High freq. variability, inc. ~mid 1700 (PMS) / ~late 1800

29. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) SUMMARY: CONCLUSIONS 1) ARE RECONSTRUCTIONS COMPARABLE? • Once specific differences in technique/approach are taken into account 2) MULTI-CENTENNIAL SCALE VARIABILITY? • Dependant on the reconstructed PMS accumulation rates • Most reliable reconstructions display no coherence in terms of a discernable influence of MWP / LIA • Due to limitations of reconstruction?

30. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) SUMMARY: CONCLUSIONS 3) FALLING SEA LEVEL TREND LAST MILLENNIA? • Still open • Trends are the result of PMS rate, (non-)correction for compaction and detrending method • SOLVABLE? Extrapolation of multi-millennial scale trends (basal and GIA) independent of data for recent ~1000 yrs compared to high resolution basal trends, e.g. DONNELLY, 2004, for this period 4) RECENT INCREASE LAST CENTURY? • POSTER: Dr Roland Gehrels • High precision dating past ~200 years, helps resolve rates of sea level rise for the last century that are higher than the trend for the last 1500 years • Precise timing is problematic • Defining such rates in past 1500 years beyond resolution achievable with conversational AMS 14C dating techniques

31. 1500-yr-long sea-level reconstructions from North Carolina to Newfoundland (Iceland) ACKNOWLEDGEMENTS: Dr Orson van de Plassche Dr Roland Gehrels THANKS TO: Prof Kurt Lambeck UNESCO POSTERS: Wright & van de Plassche: Salt-marsh accumulation rates and relative sea-level changes during the past 1500 years for three sites along the east coast of North America Gehrels: Coupling instrumental and proxy records of recent sea-level change