1. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 1 SOES 6047 Global Climate Cycles L18: Research Themes: Sea level variations and orbital forcing ๏ Dr. Heiko Pälike ๏ heiko@noc.soton.ac.uk heiko@noc.soton.ac.uk ๏ Ext. 23638, Rm. 164/34 ๏ Dr. Heiko Pälike ๏ heiko@noc.soton.ac.uk heiko@noc.soton.ac.uk ๏ Ext. 23638, Rm. 164/34

2. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 2 Last “themes” lecture: ๏ The Cenozoic Greenhouse-Doubthouse-Icehouse transitions ๏ The Cenozoic showed an extreme wealth of different climatic transitions, some of them very dramatic ๏ Overall, a general cooling trend from the earliest Cenozoic to today ๏ PETM: ๏ Ocean CCD was greatly impacted by the PETM transient event. ๏ CCD shoaled rapidly and synchronously by 2 km ๏ Ocean carbonate chemistry and  13 C recovered within ~110 ka! ๏ Removal of CO 2 from atmosphere accomplished through weathering of silicate rocks - oversaturated ocean after event due to excess weathering. ๏ E/O transition ๏ Increase in benthic δ18O of 1‰ ๏ Occurred within two steps of <40 ka each. (much faster than previously thought!) ๏ Antarctic IRD deposition, 70m sea level drop ๏ Dramatic 1000m fall in CCD ๏ The Cenozoic Greenhouse-Doubthouse-Icehouse transitions ๏ The Cenozoic showed an extreme wealth of different climatic transitions, some of them very dramatic ๏ Overall, a general cooling trend from the earliest Cenozoic to today ๏ PETM: ๏ Ocean CCD was greatly impacted by the PETM transient event. ๏ CCD shoaled rapidly and synchronously by 2 km ๏ Ocean carbonate chemistry and  13 C recovered within ~110 ka! ๏ Removal of CO 2 from atmosphere accomplished through weathering of silicate rocks - oversaturated ocean after event due to excess weathering. ๏ E/O transition ๏ Increase in benthic δ18O of 1‰ ๏ Occurred within two steps of <40 ka each. (much faster than previously thought!) ๏ Antarctic IRD deposition, 70m sea level drop ๏ Dramatic 1000m fall in CCD

3. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 3 Objectives & learning outcomes ๏ consider the various methods that have been used to re- construct eustatic sea-level change during the Cenozoic ๏ coral records ๏ seismic records from passive margins ๏ indirect d18O records of ice-volume change ๏ appreciated the timing of sea-level change as controlled by orbital dynamics ๏ focus on Oligocene “Oi-” and Miocene “Mi-” events ๏ consider the various methods that have been used to re- construct eustatic sea-level change during the Cenozoic ๏ coral records ๏ seismic records from passive margins ๏ indirect d18O records of ice-volume change ๏ appreciated the timing of sea-level change as controlled by orbital dynamics ๏ focus on Oligocene “Oi-” and Miocene “Mi-” events

4. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 4 Lecture outline ๏ Overview and Introduction ๏ Combining Haq/Vail type sea-level reconstructions with paired benthic-planktonic observations of d18O ๏ The records of Miller et al. that proposed a series of glacio- eustatic sea-level events during the Miocene and Oligocene ๏ Link between Mi-1 glacio-eustatic event and orbital forcing ๏ Discovery of large sea-level variations throughout the Oligocene, and forced by astronomical forcing ๏ Overview and Introduction ๏ Combining Haq/Vail type sea-level reconstructions with paired benthic-planktonic observations of d18O ๏ The records of Miller et al. that proposed a series of glacio- eustatic sea-level events during the Miocene and Oligocene ๏ Link between Mi-1 glacio-eustatic event and orbital forcing ๏ Discovery of large sea-level variations throughout the Oligocene, and forced by astronomical forcing

5. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 5 Billups, K. & Schrag, D. P. (2002), ‘Paleotemperatures and ice volume of the past 27 Myr revisited with paired Mg/Ca and 18O/16O measurementes on benthic foraminifera’, Paleoceanography 17, art. no. 1003. Browning, J. V., Miller, K. G., & Pak, D. K. (1996), ‘Global implications of lower to middle Eocene sequence boundaries on the New Jersey coastal plain; the icehouse cometh. ’, Geology 24, 639–642. Christie-Blick, N., Mountain, G. S., & Miller, K. G., ‘Seismic stratigraphic record of sea-level change’, Sea-Level Change, Geophysics Study Committee, ed. (National Academy Press, Washington, D. C., 1990), 116–150. Coxall, H. K., et al. (2005), ‘Rapid stepwise onset of Antarctic glaciation and deeper calcite compensation in the Pacific Ocean’, Nature 433, 53–57. Fairbanks, R. G. (1989), ‘A 17,000-year glacio-eustatic sea-level record: Influence of glacial melting rates on the Younger Dryas Event and deep-ocean circulation’, Nature 342, 637– 642. Fairbanks, R. G. & Matthews, R. K. (1978), ‘The marine oxygen isotope record in Pleistocene coral, Barbados, West Indies’, Quat. Res. 10, 181–196. Haq, B. U., Hardenbol, J., & Vail, P. R. (1987), ‘Chronology of fluctuating sea levels since the Triassic (250 million years ago to present’, Science 235, 1156–1167. Kominz, M. A. & Pekar, S. F. (2001), ‘Oligocene eustasy from two-dimensional sequence stratigraphic backstripping’, Geol. Soc. Am. Bull. 113, 291–304. Lear, C. H., Elderfield, H., & Wilson, P. A. (2000), ‘Cenozoic deep-sea temperatures and global ice volumes from MgCa in benthic foraminiferal calcite’, Science 287, 269–272. Lear, C. H., et al. (2004), ‘Late Eocene to early Miocene ice sheet dynamics and the global carbon cycle’, Paleoceanography 19, PA4015. Miller, K. G., ‘Middle Eocene to Oligocene stabe isotopes, climate and deep-water history: The terminal Eocene event? ’, Eocene-Oligocene Climatic and Biotic Evolution, D. R. Prothero & W. A. Berggren, eds. (Princeton University Press, Princeton, NJ, USA, 1992), 160–177. Miller, K. G. & Fairbanks, R. G., ‘Oligocene to Miocene carbon isotope cycles and abyssal circulation changes’, The carbon cycle and atmospheric CO ; natural variations Archean to present., T. Sundquist Eric & S. Broecker Wallace, eds. (AGU, Washington, DC, U.S.A., 1985), Geophys. Monogr., vol. 32, 469–486. Miller, K. G., Fairbanks, R. G., & Mountain, G. S. (1987), ‘Tertiary oxygen isotope synthesis, sealevel history, and continental margin erosion’, Paleoceanography 2, 1–19. Miller, K. G., Wright, J. D., & Fairbanks, R. G. (1991), ‘Unlocking the Ice House – Oligocene-Miocene oxygen isotopes, eustasy, and margin erosion’, J. Geophys. Res. - Sol. Earth & Planets 96, 6829–6848. Miller, K. G., et al. (1996), ‘Drilling and dating New Jersey Oligocene-Miocene sequences: ice volume, global sea level, and Exxon records’, Science 271, 1092–1095. Miller, K. G., et al. (1998), ‘Cenozoic global sea level, sequences, and the New Jersey transect: Results from coastal plain and continental slope drilling’, Rev. Geophys. 36, 569–601. Miller, K. G., Kominz, M. A., Browning, J. V., Wright, J.D., Mountain, G.S., Katz, M.E., Sugarman, P. J., Cramer, B.S., Christie-Blick, N., Pekar, S.F., The Phanerozoic record of global sea-level change, Science, 312, 1293-1298, 2005.Pekar, S. & Miller, K. G. (1996), ‘New Jersey Oligocene “Icehouse” sequences (ODP Leg 150X) correlated with global and Exxon eustatic records’, Geology 24, 567–570. Pekar, S. F., Miller, K. G., & Kominz, M. A. (2000), ‘Reconstructing the stratal geometry of latest Eocene to Oligocene sequences in New Jersey: resolving a patchwork distribution into a clear pattern of progradation’, Sed. Geol. 134, 93–109. Pekar, S. F., et al. (2001), ‘Evaluating the stratigraphic response to eustasy from Oligocene strata in New Jersey’, Geology 29, 55–58. Pekar, S. F., et al. (2002), ‘Calibration between eustatic estimates from backstripping and oxygen isotopic records for the Oligocene’, Geology 30, 903–906. Vail, P. R., et al., ‘Seismic stratigraphy and global changes of sea level’, Seismic Stratigraphy–Applications to Hydrocarbon Exploration, C. E. Payton, ed. (1977), Amer. Assoc. Petr. Geol. Mem., vol. 26, 49–212. Wade, B. S. & Pälike, H. (2004), ‘Oligocene climate dynamics’, Paleoceanography 19, PA4019. Wright, J. D. & Miller, K. G., ‘Miocene stable isotope stratigraphy, Site 747, Kerguelen Plateau’, Proc. ODP, Sci. Res., J. A. Barron & B. Larsen, eds. (Ocean Drilling Program, College Station, TX, U.S.A., 1992), vol. 120, 855–866. Wright, J. D., Miller, K. G., & Fairbanks, R. G. (1992), ‘Early and middle Micocene stable isotopes: Implications for deepwater circulation and climate’, Paleoceanography 7, 357–389. Zachos, J. C., Quinn, T. M., & Salamy, K. A. (1996), ‘High resolution ( years) deep-sea foraminiferal stable isotope records of the Eocene-Oligocene climate transition’, Paleoceanography 11, 251–266. Zachos, J. C., et al. (2001), ‘Climate response to orbital forcing across the Oligocene-Miocene Boundary’, Science 292, 274–278. Zachos, J. C., et al. (2001), ‘Trends, rhythms, and aberrations in global climate 65 Ma to present’, Science 292, 686–693. Some references

6. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 6 Introduction ๏ There is a long-standing challenge to understand global (eustatic) sea level changes and their effects on the stratigraphic (and climatic) record ๏ Eustatic sea level change is related to either ๏ mass re-distribution of water in the oceans (ice-volume) ๏ change in basin volume (spreading rates) ๏ Oxygen isotope measurements of deep-sea foraminifera proved a proxy of global sea level changes caused by the waxing and waning of continental ice sheets. ๏ BUT: the d18O record is a function of temperature, local salinity and temperature, and thus glacio-eustasy can only be estimated by assuming a thermal history ๏ Hence, it is necessary to calibrate this proxy record with a more direct method ๏ In the past, this involved looking at seismic records from passive margins, looking at corals, or comparing benthic and planktonic d18O records ๏ There is a long-standing challenge to understand global (eustatic) sea level changes and their effects on the stratigraphic (and climatic) record ๏ Eustatic sea level change is related to either ๏ mass re-distribution of water in the oceans (ice-volume) ๏ change in basin volume (spreading rates) ๏ Oxygen isotope measurements of deep-sea foraminifera proved a proxy of global sea level changes caused by the waxing and waning of continental ice sheets. ๏ BUT: the d18O record is a function of temperature, local salinity and temperature, and thus glacio-eustasy can only be estimated by assuming a thermal history ๏ Hence, it is necessary to calibrate this proxy record with a more direct method ๏ In the past, this involved looking at seismic records from passive margins, looking at corals, or comparing benthic and planktonic d18O records

7. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 7 ๏ Thompson & Goldstein (2005) produced very well dated sea- level record from globally distributed coral measurements ๏ coral records are very powerful but limited in how far back in time records exist. ๏ local effects also play a role ๏ Thompson & Goldstein (2005) produced very well dated sea- level record from globally distributed coral measurements ๏ coral records are very powerful but limited in how far back in time records exist. ๏ local effects also play a role Coral sea-level records From: Lambeck, K, Chappell, J., (2001) Sea level Change through the Last Glacial Cycle. Science, v. 292, no. 5517, p. 679-686. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses requires the prior written permission from AAAS.Lambeck, K, Chappell, J., (2001) Sea level Change through the Last Glacial Cycle. Science, v. 292, no. 5517, p. 679-686. Courtesy of Paige Gill (Florida Keys National Marine Sanctuary, NOAA) From: Henderson, G.M., (2005) Coral Clues to Rapid Sea-Level Change. Science, v. 308, no. 5720, p. 361-362. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses requires the prior written permission from AAAS.Henderson, G.M., (2005) Coral Clues to Rapid Sea-Level Change. Science, v. 308, no. 5720, p. 361-362.

8. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 8 Seismic records from continental passive margins ๏ It has been postulated that the rate of sea level change (rather than absolute sea level) determines the stratigraphic record of regressions, high-stands, and transgressions ๏ Margin record extremely long, but complicate by tectonics (subsidence & uplift) and changes in sediment supply ๏ Sea level falls and tectonic changes produce discrete, unconformity-bounded units on continental margins known as sequences, and sequences are the fundamental building blocks of the stratigraphic record. ๏ In the 1970’s, oil company researchers invented a new clever method in using seismic reflection profiles to identify sequences, and to produce eustatic estimates from stratigraphic records (Vail et al., 1977; Haq et al., 1987) ๏ It has been postulated that the rate of sea level change (rather than absolute sea level) determines the stratigraphic record of regressions, high-stands, and transgressions ๏ Margin record extremely long, but complicate by tectonics (subsidence & uplift) and changes in sediment supply ๏ Sea level falls and tectonic changes produce discrete, unconformity-bounded units on continental margins known as sequences, and sequences are the fundamental building blocks of the stratigraphic record. ๏ In the 1970’s, oil company researchers invented a new clever method in using seismic reflection profiles to identify sequences, and to produce eustatic estimates from stratigraphic records (Vail et al., 1977; Haq et al., 1987)

9. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 9 Seismic records from continental passive margins ๏ The seismic eustatic sea-level curves remained controversial, because the fundamental methods used to create these curves were questioned (Christie-Blick et al., 1990) ๏ main criticism: Haq curve assembled from many basins around the world, with different subsidence histories and (poor?) biostrati- graphic age control ๏ Haq defined 1st, 2nd and 3rd order sequences ๏ The seismic eustatic sea-level curves remained controversial, because the fundamental methods used to create these curves were questioned (Christie-Blick et al., 1990) ๏ main criticism: Haq curve assembled from many basins around the world, with different subsidence histories and (poor?) biostrati- graphic age control ๏ Haq defined 1st, 2nd and 3rd order sequences Courtesy: http://commons.wikimedia.org/wiki/File:Phanerozoic_Sea_Level.png.http://commons.wikimedia.org/wiki/File:Phanerozoic_Sea_Level.png Courtesy: http://commons.wikimedia.org/wiki/File:Phanerozoic_Sea_Level.png.http://commons.wikimedia.org/wiki/File:Phanerozoic_Sea_Level.png

10. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 10 ๏ Miller et al. convinced ODP that it would be worthwhile to test sea-level estimates by drilling a single set of continental margin deposits at New Jersey (ODP Legs 150, 150X (onshore)) ๏ single basin record avoids some of the problems with multi- basin study of Haq-type curves ๏ also allowed comparison with d18O data from foraminifera ๏ Miller et al. convinced ODP that it would be worthwhile to test sea-level estimates by drilling a single set of continental margin deposits at New Jersey (ODP Legs 150, 150X (onshore)) ๏ single basin record avoids some of the problems with multi- basin study of Haq-type curves ๏ also allowed comparison with d18O data from foraminifera Testing the sea-level curves Reproduced by permission of American Geophysical Union: Miller, K.G., Mountain, G.S., Browning, J.V., Kominz, M., Sugarman, P.J., Christ ie-Blick, N., Katz, M. E., and Wright, J.D.,‘Cenozoic global sea level, sequences, and the New Jersey transect: Results from coastal plain and continental slope drilling’, Rev. Geophys. v. 36, p. 569–601. 1998. Copyright [1998] American Geophysical Union.

11. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 11 ๏ Miller et al. convinced ODP that it would be worthwhile to test sea-level estimates by drilling a single set of continental margin deposits at New Jersey (ODP Legs 150, 150X (onshore)) ๏ single basin record avoids some of the problems with multi- basin study of Haq-type curves ๏ also allowed comparison with d18O data from foraminifera ๏ Miller et al. convinced ODP that it would be worthwhile to test sea-level estimates by drilling a single set of continental margin deposits at New Jersey (ODP Legs 150, 150X (onshore)) ๏ single basin record avoids some of the problems with multi- basin study of Haq-type curves ๏ also allowed comparison with d18O data from foraminifera Testing the sea-level curves Reproduced by permission of American Geophysical Union: Miller, K.G., Mountain, G.S., Browning, J.V., Kominz, M., Sugarman, P.J., Christ ie-Blick, N., Katz, M. E., and Wright, J.D.,‘Cenozoic global sea level, sequences, and the New Jersey transect: Results from coastal plain and continental slope drilling’, Rev. Geophys. v. 36, p. 569–601. 1998. Copyright [1998] American Geophysical Union.

12. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 12 Stable isotopes and ice-volume ๏ revisiting the Pleistocene ๏ Late Pleistocene d18O records constrain ice volume (glacio- eustatic) changes by measuring absolute sea-level variations with coral observations ๏ Calibration of Fairbanks & Matthews (1978) 0.11‰ / 10m eustatic sea-level ๏ hence: ca. 1.3‰ of total 1.75‰ in foram isotope shift from LGM to today is attributable to global sea-water d18O (=sea-level) changes, hence global waters were ca. 2°C cooler during LGM ๏ revisiting the Pleistocene ๏ Late Pleistocene d18O records constrain ice volume (glacio- eustatic) changes by measuring absolute sea-level variations with coral observations ๏ Calibration of Fairbanks & Matthews (1978) 0.11‰ / 10m eustatic sea-level ๏ hence: ca. 1.3‰ of total 1.75‰ in foram isotope shift from LGM to today is attributable to global sea-water d18O (=sea-level) changes, hence global waters were ca. 2°C cooler during LGM

13. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 13 Stable isotopes and ice-volume ๏ different technique: ๏ use paired benthic and planktonic d18O changes ๏ planktonic record from low-latitudes (non-upwelling), ๏ assume that concomitant change due to global sea-level signal, not temperature ๏ Covariance between benthic and western equatorial Pacific planktonic foraminiferal d18O records was 1.2-1.3‰ from the LGM to today (Shackleton & Opdyke, 1973). ๏ predicts sea-level difference of 109-118m (Fairbanks & Matthews, 1978), relatively close to the coral record ๏ different technique: ๏ use paired benthic and planktonic d18O changes ๏ planktonic record from low-latitudes (non-upwelling), ๏ assume that concomitant change due to global sea-level signal, not temperature ๏ Covariance between benthic and western equatorial Pacific planktonic foraminiferal d18O records was 1.2-1.3‰ from the LGM to today (Shackleton & Opdyke, 1973). ๏ predicts sea-level difference of 109-118m (Fairbanks & Matthews, 1978), relatively close to the coral record Tertiary equatorial planktonic records Reproduced by permission of American Geophysical Union: Miller, K.G., Wright, J.D., Fairbanks, R.G., Unlocking the Ice House: Oligocene-Miocene Oxygen Isotopes, Eustasy, and Margin Erosion J. Geophys. Res., v. 96, no. B4, p. 6829–6848. 6 August 1990. Copyright [1991] American Geophysical Union.

14. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 14 ๏ From very low resolution benthic foraminiferal records, Kenneth Miller et al. (several papers), described, and named, a series of glacial events during the Oligocene and Miocene ๏ These events were given names following the Oi-1, Oi-2 etc. convention for the Oligocene, and Mi-1, Mi-2 etc. for the Miocene. ๏ From very low resolution benthic foraminiferal records, Kenneth Miller et al. (several papers), described, and named, a series of glacial events during the Oligocene and Miocene ๏ These events were given names following the Oi-1, Oi-2 etc. convention for the Oligocene, and Mi-1, Mi-2 etc. for the Miocene. Miller Oi- and Mi- glaciation events Micocene oxygen isotope stratigraphy and magnetostratigraphy for the Eastern North Atlantic Site 608 and western North Altantic Site 563 Reproduced by permission of American Geophysical Union: Miller, K.G., Wright, J.D., Fairbanks, R.G., Unlocking the Ice House: Oligocene-Miocene Oxygen Isotopes, Eustasy, and Margin Erosion J. Geophys. Res., v. 96, no. B4, p. 6829–6848. 6 August 1990. Copyright [1991] American Geophysical Union.

15. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 15 ๏ From very low resolution benthic foraminiferal records, Kenneth Miller et al. (several papers), described, and named, a series of glacial events during the Oligocene and Miocene ๏ These events were given names following the Oi-1, Oi-2 etc. convention for the Oligocene, and Mi-1, Mi-2 etc. for the Miocene. ๏ From very low resolution benthic foraminiferal records, Kenneth Miller et al. (several papers), described, and named, a series of glacial events during the Oligocene and Miocene ๏ These events were given names following the Oi-1, Oi-2 etc. convention for the Oligocene, and Mi-1, Mi-2 etc. for the Miocene. Miller Oi- and Mi- glaciation events Reproduced with permission of GSA: Pekar, S.F., Christie-Blick, N., Kominz, M.A., Miller., K.G., (2002) Calibration between eustatic estimates from backstripping and oxygen isotopic records for the Oligocene. Geology, v. 30, no. 10, p. 903-906.

16. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 16 ๏ meanwhile, Zachos and co-workers, developed, for the first time, a whole series of much more high-resolution d18O & d13C curves from single sites, partly following this naming scheme ๏ BUT: also introduce differently labeled Oi-1a and Oi-1b events that are different to the ones from Miller! ๏ A Mess! ๏ meanwhile, Zachos and co-workers, developed, for the first time, a whole series of much more high-resolution d18O & d13C curves from single sites, partly following this naming scheme ๏ BUT: also introduce differently labeled Oi-1a and Oi-1b events that are different to the ones from Miller! ๏ A Mess! Miller Oi- and Mi- glaciation events Reproduced by permission of American Geophysical Union: Zachos, J.C., Quinn, T.M., & Salamy, K.A. ‘High resolution ( years) deep-sea foraminiferal stable isotope records of the Eocene-Oligocene climate transition’, Paleoceanography, v. 11, p. 251–266, 21 February 1996. Copyright [1996] American Geophysical Union. Reproduced by permission of American Geophysical Union: Zachos, J.C., Quinn, T.M., & Salamy, K.A. ‘High resolution ( years) deep-sea foraminiferal stable isotope records of the Eocene-Oligocene climate transition’, Paleoceanography, v. 11, p. 251–266, 21 February 1996. Copyright [1996] American Geophysical Union.

17. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 17 ๏ Zachos et al. isotope curve from Ceara Rise for the first time characterises the events around Mi-1 (Zachos et al., Science 2001b), and conclude that Mi-1 involves significant additional ice-volume on Antarctica, partially controlled by orbital variations (low obliquity & eccentricity) ๏ Question: Does this hold up for other Mi- and Oi- events? ๏ Zachos et al. isotope curve from Ceara Rise for the first time characterises the events around Mi-1 (Zachos et al., Science 2001b), and conclude that Mi-1 involves significant additional ice-volume on Antarctica, partially controlled by orbital variations (low obliquity & eccentricity) ๏ Question: Does this hold up for other Mi- and Oi- events? Miller Oi- and Mi- glaciation events Reproduced by permission of American Geophysical Union: Zachos, J.C., Quinn, T.M., & Salamy, K.A. ‘High resolution ( years) deep-sea foraminiferal stable isotope records of the Eocene-Oligocene climate transition’, Paleoceanography, v. 11, p. 251–266, 21 February 1996. Copyright [1996] American Geophysical Union. Reproduced by permission of American Geophysical Union: Zachos, J.C., Quinn, T.M., & Salamy, K.A. ‘High resolution ( years) deep-sea foraminiferal stable isotope records of the Eocene-Oligocene climate transition’, Paleoceanography, v. 11, p. 251–266, 21 February 1996. Copyright [1996] American Geophysical Union.

18. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 18 Sideline: paired Mg/Ca and d18OO ๏ meanwhile, a new method of estimating temperatures using the Mg/Ca proxy appeared (Lear et al, 2000). ๏ Billups and Schrag (2002) used paired Mg/Ca and d18O data to elucidate what contribution sea-level made at the various Mi- glacial events ๏ meanwhile, a new method of estimating temperatures using the Mg/Ca proxy appeared (Lear et al, 2000). ๏ Billups and Schrag (2002) used paired Mg/Ca and d18O data to elucidate what contribution sea-level made at the various Mi- glacial events Reproduced by permission of American Geophysical Union: Billups, K. & Schrag, D.P., ‘Paleotemperatures and ice volume of the past 27 Myr revisited with paired Mg/Ca and 18O/16O measurementes on benthic foraminifera’, Paleoceanography, v. 17, no. 1003. 29 January 2002. Copyright [2002] American Geophysical Union.

19. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 19 ๏ Zachos et al. isotope curve from Ceara Rise for the first time characterises the events around Mi-1 (Zachos et al., Science 2001b), and conclude that Mi-1 involves significant additional ice-volume on Antarctica, partially controlled by orbital variations (low obliquity & eccentricity) ๏ Question: Does this hold up for other Mi- and Oi- events? ๏ Zachos et al. isotope curve from Ceara Rise for the first time characterises the events around Mi-1 (Zachos et al., Science 2001b), and conclude that Mi-1 involves significant additional ice-volume on Antarctica, partially controlled by orbital variations (low obliquity & eccentricity) ๏ Question: Does this hold up for other Mi- and Oi- events? Miller Oi- and Mi- glaciation events Reproduced by permission of American Geophysical Union: Zachos, J.C., Quinn, T.M., & Salamy, K.A. ‘High resolution ( years) deep-sea foraminiferal stable isotope records of the Eocene-Oligocene climate transition’, Paleoceanography, v. 11, p. 251–266, 21 February 1996. Copyright [1996] American Geophysical Union. Reproduced by permission of American Geophysical Union: Zachos, J.C., Quinn, T.M., & Salamy, K.A. ‘High resolution ( years) deep-sea foraminiferal stable isotope records of the Eocene-Oligocene climate transition’, Paleoceanography, v. 11, p. 251–266, 21 February 1996. Copyright [1996] American Geophysical Union.

20. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 20 medium resolution Oligocene ๏ Lear et al. (2004) established low resolution stable isotope (and Mg/Ca) record for Site 1218, using orbital age model. ๏ shows previously identified glacial events Oi-1 and Mi-1 ๏ but remaining Oi- events do not really stand out here ๏ Lear et al. (2004) established low resolution stable isotope (and Mg/Ca) record for Site 1218, using orbital age model. ๏ shows previously identified glacial events Oi-1 and Mi-1 ๏ but remaining Oi- events do not really stand out here Mi-1 Reproduced by permission of American Geophysical Union: Lear, C.H., Rosenthal, Y., Coxall, H.K., Wilson, P.A.,(2004), ‘Late Eocene to early Miocene ice sheet dynamics and the global carbon cycle’, Paleoceanography, v. 19, no 4, 11 pp. 13 November 2004.Copyright [2004] American Geophysical Union.

21. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 21 Benthic stable isotopes ๏ High-resolution (<6kyr) data set shows distinct variability of δ18O & δ13C at astronomical frequencies Reproduced by permission of American Geophysical Union: Wade, B.S., Pälike, H.,Oligocene climate dynamics, Paleoceanography, v. 19, p. 353-387. 8 December 2004. Copyright [2004] American Geophysical Union.

22. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 22 Benthic stable isotopes ๏ High-resolution (<6kyr) data set shows distinct variability of δ18O & δ13C at astronomical frequencies ๏ compares with rescaled Zachos et al. (2001) composite ๏ High-resolution (<6kyr) data set shows distinct variability of δ18O & δ13C at astronomical frequencies ๏ compares with rescaled Zachos et al. (2001) composite Reproduced by permission of American Geophysical Union: Wade, B.S., Pälike, H.,Oligocene climate dynamics, Paleoceanography, v. 19, p. 353-387. 8 December 2004. Copyright [2004] American Geophysical Union.

23. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 23 Benthic stable isotopes ๏ show distinct imprint of ๏ ~1.2 Myr obliquity in δ18O ๏ “Oi” events are really multiple events ๏ show distinct imprint of ๏ ~1.2 Myr obliquity in δ18O ๏ “Oi” events are really multiple events Reproduced by permission of American Geophysical Union: Wade, B.S., Pälike, H.,Oligocene climate dynamics, Paleoceanography, v. 19, p. 353-387. 8 December 2004. Copyright [2004] American Geophysical Union.

24. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 24 Benthic stable isotopes ๏ show distinct imprint of ~405 kyr eccentricity in δ13C ๏ allows new 405 kyr cycle based event nomenclature ๏ show distinct imprint of ~405 kyr eccentricity in δ13C ๏ allows new 405 kyr cycle based event nomenclature Reproduced by permission of American Geophysical Union: Wade, B.S., Pälike, H.,Oligocene climate dynamics, Paleoceanography, v. 19, p. 353-387. 8 December 2004. Copyright [2004] American Geophysical Union.

25. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 25 Planktic stable isotopes ๏ Observed benthic-planktic isotope gradients ๏ carbon isotopes also show glacial cycles ๏ specific planktic events not apparent in benthic record ๏ Observed benthic-planktic isotope gradients ๏ carbon isotopes also show glacial cycles ๏ specific planktic events not apparent in benthic record Reproduced by permission of American Geophysical Union: Wade, B.S., Pälike, H.,Oligocene climate dynamics, Paleoceanography, v. 19, p. 353-387. 8 December 2004. Copyright [2004] American Geophysical Union.

26. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 26 Sea-level (co-varying benthic-planktic) ๏ assume simultaneous variations in benthic and planktic δ 18 O reflect global seawater changes ๏ get 50-70m sea-level fluctuations during Oligocene ๏ assume simultaneous variations in benthic and planktic δ 18 O reflect global seawater changes ๏ get 50-70m sea-level fluctuations during Oligocene Reproduced by permission of American Geophysical Union: Wade, B.S., Pälike, H.,Oligocene climate dynamics, Paleoceanography, v. 19, p. 353-387. 8 December 2004. Copyright [2004] American Geophysical Union.

27. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 27 New results from hi-res records ๏ From same high-resolution paired benthic-planktonic Oligocene data set can apply old method of Fairbanks & Matthews: ๏ observe simultaneous changes between d18O in benthic and planktonic foraminifera of about 60 meters during the Oligocene! ๏ From same high-resolution paired benthic-planktonic Oligocene data set can apply old method of Fairbanks & Matthews: ๏ observe simultaneous changes between d18O in benthic and planktonic foraminifera of about 60 meters during the Oligocene! Reproduced by permission of American Geophysical Union: Wade, B.S., Pälike, H.,Oligocene climate dynamics, Paleoceanography, v. 19, p. 353-387. 8 December 2004. Copyright [2004] American Geophysical Union.

28. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 28 ๏ work that is currently in progress again shows that almost all of the Oligocene and early Miocene glacial events (=sea-level variations) are related to astronomical “nodes” of low obliquity, and 400 kyr eccentricity cycle work in progress: From: Pälike, H., Norris, R.D., Herrle, J.O., Wilson, P.A., Coxall, H.K., Lear, C.H., Shackleton, N.J., Tripati, A.K., Wade, B.S., (2006) The Heartbeat of the Oligocene Climate System. Science, v. 314, p. 1894- 1898. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses requires the prior written permission from AAAS.Pälike, H., Norris, R.D., Herrle, J.O., Wilson, P.A., Coxall, H.K., Lear, C.H., Shackleton, N.J., Tripati, A.K., Wade, B.S., (2006) The Heartbeat of the Oligocene Climate System. Science, v. 314, p. 1894- 1898.

29. L18 Themes: Sea level variations & orbital forcing SOES6047 - Global Climate Cycles 29 Key point summary ๏ The geological history is characterised by frequent glacial events ๏ new records show that for the Oligocene these were significant (~60m in sea-level change), and periodically re- occurring ๏ previously identified oxygen isotope extremes (the Mi- and Oi- events) have been shown to consist of multiple events, driven at least partly by astronomical variations ๏ Glacio-eustatic sea-level events appear to be more readily achieved during times of low obliquity variations ๏ When obliquity is low, they are paced by 400 kyr cycles ๏ What is the mechanism that connects the orbital evolution with the inception of glacial cycles? cold summers ? ๏ link between sea-level curves of Haq et al. and high- resolution d18O records? Maybe ๏ The geological history is characterised by frequent glacial events ๏ new records show that for the Oligocene these were significant (~60m in sea-level change), and periodically re- occurring ๏ previously identified oxygen isotope extremes (the Mi- and Oi- events) have been shown to consist of multiple events, driven at least partly by astronomical variations ๏ Glacio-eustatic sea-level events appear to be more readily achieved during times of low obliquity variations ๏ When obliquity is low, they are paced by 400 kyr cycles ๏ What is the mechanism that connects the orbital evolution with the inception of glacial cycles? cold summers ? ๏ link between sea-level curves of Haq et al. and high- resolution d18O records? Maybe

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