MIS-11: A Super-Interglacial with enhanced North Atlantic Deep Water Circulation
Final Report Abstract
The goal of the research project was to better understand the strength and structure of the Atlantic Meridional Overturning Circulation (AMOC) during the "superinterglacial" MIS-11, and to test effects of future climate warming and partial melting of the Greenland Ice Sheet (GIS). The underlying observation was a persistent, 30 ka long, unique Nd isotopic composition of ODP core 1063 at the deep Bermuda Rise. A spatial and temporal survey of deep-water Nd isotopic compositions throughout the Atlantic was designed to prove, or reject, the uniqueness of this observation. For this purpose, cores with well-dated climate states MIS-12 to MIS-11 were chosen. An approximate millennial time resolution was the goal to gain insight into the synchronicity of events. A total of 6 cores were examined from 59°N to 30°S, covering a water depth of 2180 to 4400 m. About 220 Nd isotope measurements yielded a total range of 10ε units (-6.9 to -17), with a strong north-south gradient (from non-radiogenic to radiogenic) Nd isotopes, similar to today. However, the most radiogenic values occur in regions of the presentday Iceland-Scotland Overflow Water (ISOW), which carry radiogenic Nd from the Icelandic volcanic rocks. As a consequence, a strong east-west isotope gradient also exists from the Labrador Sea to the Mid-Atlantic Ridge. In addition, we reassessed the chronology of the sediment cores studied and evaluated literature data. In MIS-12, the Nd isotope of the deep Atlantic resembles that of the Last Glacial Maximum. Therefore, the equatorial and subtropical South Atlantic was likely influenced by a smaller fraction of southern source water (SSW), whereas the deep North Atlantic has persistent influences of northern source water (NSW). Deep water formation, as indicated by a decrease in North Atlantic Nd isotope ratios, began very early, while the climate was starting to warm. Non-conservative aspects of the Nd cycle remain elusive. The occurrence of ISOW appears to be an important fingerprint of such early Arctic deep water formation. Fewer radiogenic Nd values are observed during the persistently warm climate in MIS-11 than in the Holocene, but ODP core 1063 remains an observational singularity. Thus, again non-conservative aspects of a less radiogenic influence or Nd releases from the partially melted GIS may be driving these observations. Alternatively, even stronger Labrador Sea deep water formation may be the cause. The persistently active AMOC during MIS-11 is unaffected by the mass loss of the GIS. Rates of up to 0.8 m sea level equivalent per millennium occurred, but these are lower than present-day maximum estimates for humaninduced climate change.
Publications
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Atlantic-wide deep circulation patterns during MIS 11. International Conference on Paleoceanography, Sydney, Australia [Poster]
Link, J.M. & Frank, N.
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Atlantic-wide deep circulation patterns during MIS 11. Joint IODP/ICDP Meeting, Cologne, Germany [Poster]
Link, J.M. & Frank, N.
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Constraining the Variability of the Atlantic Meridional Overturning Circulation During the Holocene. Geophysical Research Letters, 46(20), 11338-11346.
Lippold, Jörg; Pöppelmeier, Frerk; Süfke, Finn; Gutjahr, Marcus; Goepfert, Tyler J.; Blaser, Patrick; Friedrich, Oliver; Link, Jasmin M.; Wacker, Lukas; Rheinberger, Stefan & Jaccard, Samuel L.
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Influence of Ocean Circulation and Benthic Exchange on Deep Northwest Atlantic Nd Isotope Records During the Past 30, 000 Years. Geochemistry, Geophysics, Geosystems, 20(9), 4457-4469.
Pöppelmeier, F.; Blaser, P.; Gutjahr, M.; Süfke, F.; Thornalley, D. J. R.; Grützner, J.; Jakob, K. A.; Link, J. M.; Szidat, S. & Lippold, J.
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Stable Atlantic Meridional Overturning Circulation during the Holocene. International Conference on Paleoceanography, Sydney, Australia [Poster]
Lippold, J.; Pöppelmeier, F.; Süfke, F.; Gutjahr, M.; Goepfert, T.J.; Blaser, P.; Friedrich, O.; Link, J.M.; Wacker, L.; Rheinberger, S. & Jaccard, S.L.
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Deep water circulation patterns in the Atlantic during MISs 12-11. American Geophysical Union (AGU).
Link, Jasmin M. & Frank, Norbert
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PhD Thesis: “Atlantic Deep Circulation During Marine Isotope Stage 11 and the Last One Million Years Inferred From Neodymium Isotopes”, Heidelberg University
Jasmin M. Link
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Deep-ocean circulation in the North Atlantic during the Plio-Pleistocene intensification of Northern Hemisphere Glaciation (~2.65–2.4 Ma). Marine Micropaleontology, 165(c(2021, 5)), 101998.
Jakob, Kim A.; Pross, Jörg; Link, Jasmin M.; Blaser, Patrick; Hauge Braaten, Anna & Friedrich, Oliver
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Persistent Iceland-Scotland Overflow Water formation during MIS 11. International Conference on Paleoceanography, Bergen, Norway [Poster]
Link, J.M. & Frank, N.
