1. Abrupt Climate Change Paleoceanography Presentation 6/15/2015 By Beth Hart ?

2. Abrupt Climate Cycles Lockwood, J.G., 2001, Abrupt and sudden climatic transitions and fluctuations: a review, International Journal of Climatology, 21 : 1153-1179.

3. Abrupt Climate Cycles Ivanochko, T.S.,et al., 2005, Variations in tropical convection as an amplifier of global climate change at the millennial scale, Earth and Planetary Science Letters, 235 : 302-314.

4. The end of the present interglacial: how and when ? Broecker, W.S., 1998, The end of the present interglacial: how and when ?, Quaternary Science Reviews, 17: 689-694. Three Questions: 1.Were previous intervals of peak interglaciation terminated by abrupt climate change ? 2. How close are we to the end of the present interval of peak interglaciation ? 3. Will the ongoing buildup of greenhouse gases alter the natural sequence of events ?

5. Were previous intervals of peak interglaciation terminated by abrupt climate change ? Broecker, W.S., 1998, The end of the present interglacial: how and when ?, Quaternary Science Reviews, 17: 689-694. How do interglacials end?

6. Figure 14-20 (Ruddiman text)

7. Were previous intervals of peak interglaciation terminated by abrupt climate change ? Broecker, W.S., 1998, The end of the present interglacial: how and when ?, Quaternary Science Reviews, 17: 689-694. Decreased insolation No evidence of renewed ice growth

8. Were previous intervals of peak interglaciation terminated by abrupt climate change ? Broecker, W.S., 1998, The end of the present interglacial: how and when ?, Quaternary Science Reviews, 17: 689-694. Evidence of abrupt change: European pollen records (Woillard, 1978) N. pachyderma forminifera go “gang-buster” (McManus, 1996)

9. How close are we to the end of the present interval of peak interglaciation ? Broecker, W.S., 1998, The end of the present interglacial: how and when ?, Quaternary Science Reviews, 17: 689-694. Estimate the length of previous interglacials. 18 O records for benthic foraminifera Warmth lasted ~11kyr (one half precession cycle) Terminations occur at N.H. insolation peaks and last ~11kyr Length of present interglacial (11.5kyr – 17kyr) After Heinrich event #1 (17kyr) Beginning of Bölling warm interval (14.5kyr) Younger Dryas within glacial period (11.5kyr)

10. How close are we to the end of the present interval of peak interglaciation ? Lockwood, J.G., 2001, Abrupt and sudden climatic transitions and fluctuations: a review, International Journal of Climatology, 21 : 1153-1179.

11. How close are we to the end of the present interval of peak interglaciation ? Broecker, W.S., 1998, The end of the present interglacial: how and when ?, Quaternary Science Reviews, 17: 689-694. If analogous to Eemian: Ice cap growth should precede Sea level fall has not begun Interglacial will last more than several kyrs If analogous to stage 11: Driven by precession Interglacial much longer From Broecker and Stocker (2006)

12. How close are we to the end of the present interval of peak interglaciation ? From Ruddiman (2005)

13. Will the ongoing buildup of greenhouse gases alter the natural sequence of events ? Broecker, W.S., 1998, The end of the present interglacial: how and when ?, Quaternary Science Reviews, 17: 689-694. THC – potential mode for abrupt climate switch Weakened NADW formation during glacial periods Requires the addition of fresh water (change in density) in North Atlantic Interglacials end due to release of fresh water from melting of newly formed ice caps Ice growth prior to end of Eemian warm conditions

14. Will the ongoing buildup of greenhouse gases alter the natural sequence of events ? Figure 15-13 (Ruddiman text) Figure 15-20 (Ruddiman text)

15. Will the ongoing buildup of greenhouse gases alter the natural sequence of events ? Broecker, W.S., 1998, The end of the present interglacial: how and when ?, Quaternary Science Reviews, 17: 689-694. What about greenhouse gases ? Cause a premature transition from between modes Retard growth of ice sheets No new ice sheets => no fresh water to North Atlantic => no reorganization of THC Greenhouse gas buildup could be enough to trigger an alteration of THC

16. Conclusions Broecker, W.S., 1998, The end of the present interglacial: how and when ?, Quaternary Science Reviews, 17: 689-694. Where do we go from here ? 1.Monitor present-day deep water formation 2. Learn where and how deep water forms 3. Determine if THC reorganizations (induced by greenhouse gas) would cause climatic cooling AND…….

17. We’re still in an interglacial cycle! (Even in Ohio) Surprised, anyone ? Broecker, W.S., 1998, The end of the present interglacial: how and when ?, Quaternary Science Reviews, 17: 689-694.

18. Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in Europe: a chronicle of a changing chronology, Quaternary Science Reviews, 22: 763-768. Timing and duration of Last Interglacial conditions in Europe: a chronicle of a changing chronology 1.The Last Interglacial 2. Current interpretation 3. Remaining issues Figure 15-6c (Ruddiman text)

19. Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in Europe: a chronicle of a changing chronology, Quaternary Science Reviews, 22: 763-768. The Last Interglacial: Why study the Last Interglacial ? Most recent period with similar interglacial conditions Minimal anthropogenic effects Uncertainties Lack precise absolute timescales and stratigraphic markers Correlation of terrestrial evidence with changes in ice volume and sea level Timing and response of environment to the end of interglacial periods

20. Figure 15-8 (Ruddiman text)

21. Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in Europe: a chronicle of a changing chronology, Quaternary Science Reviews, 22: 763-768. The Last Interglacial: The First Steps: Shackleton (1969) – Eemian equivalent to MIS 5e Last Interglacial lasts ½ precessional cycle (not ½ eccentricity cycle) Agreed with Muller (1974) terrestrial evidence from Germany Involved annual laminations and extrapolation of sedimentation rates No absolute dates Assumption of synchronous boundaries Marine timescales assigned to terrestrial records

22. Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in Europe: a chronicle of a changing chronology, Quaternary Science Reviews, 22: 763-768. The Last Interglacial: Piecing it together: Many scientists attempted to correlate marine timescales to terrestrial records. Terrestrial interglacial period extended into MIS 5d Evidence provided a range of times for Last Interglacial duration (11kyr – 23kyr) Neither upper nor lower boundaries were coincident between marine and terrestrial records Diachroneity between northern and southern European terrestrial records

23. Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in Europe: a chronicle of a changing chronology, Quaternary Science Reviews, 22: 763-768. Current Interpretation: 128ka – sea level at present height 127ka – peak insolation 126ka – full interglacial 120ka – decrease of temperatures due to orbital changes; sea-ice and tundra expand ~Increased albedo~ 115ka – end interglacial in northern Europe 110ka – end interglacial in southern Europe

24. Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in Europe: a chronicle of a changing chronology, Quaternary Science Reviews, 22: 763-768. Remaining Issues: Timing and nature of Heinrich event 11 Deglaciation complete by 128ka What is the cause of postulated ice- rafting event at 127ka ? Replication of marine patterns with other margins Is there a lagged SST and arboreal response everywhere ? Is response geographically dependent ? Large diachroneity in Europe When does glaciation begin in intermediate areas ?

26. Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in Europe: a chronicle of a changing chronology, Quaternary Science Reviews, 22: 763-768. The Last Interglacial: Piecing it together: Tzedakis, et al., 1997 Glacial-to-interglacial transitions used as tie points Transitions represent rapid events Vegetation response without significant delay Interglacial endpoints not fixed Lacked evidence of abrupt elimination of vegetation Created effect of terrestrial interglacials extending after marine glacial conditions began Observed that forest (terrestrial interglacial) period extended into MID 5d (marine stadial period)

27. Tzedakis, C., 2003, Timing and duration of Last Interglacial conditions in Europe: a chronicle of a changing chronology, Quaternary Science Reviews, 22: 763-768. The Last Interglacial: Piecing it together: Kukla, et al., 1997 Grande Pile pollen record with fixed beginning of Last Interglacial (MIS 6/5) and Pleniglacial (MIS 5/4) Inferred duration of Last Interglacial (23 kyr) Terrestrial interglacial extends into MIS 5d and concludes with major IRD MIS 5e to 5d transition occurs before IRD and polar foraminifera N. pachyderma (McManus, et al., 1994)