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• Morée, Anne; Sun, Tianyi; Bretones, Anaïs; Straume, Eivind Olavson; Nisancioglu, Kerim Hestnes & Gebbie, Geoffrey (2021). Cancellation of the precessional cycle in δ18O records during the Early Pleistocene . Geophysical Research Letters. ISSN 0094-8276. doi: 10.1029/2020GL090035. Show summary

  The dominant pacing of glacial‐interglacial cycles in deep‐ocean δ18O records changed substantially during the Mid‐Pleistocene Transition. The precessional cycle (∼23 ky) is absent during the Early Pleistocene, which we show can be explained by cancellation of the hemispherically anti‐phased precessional cycle in the Early Pleistocene interior ocean. Such cancellation develops due to mixing of North Atlantic and Southern Ocean δ18O signals at depth, and shows characteristic spatial patterns. We explore the cancellation potential for different North Atlantic and Southern Ocean deep‐water source δ18O values using a tracer transport ocean model. Cancellation of precession occurs for all signal strengths and is widespread for a signal strength typical for the Early Pleistocene. Early Pleistocene precessional power is therefore likely incompletely archived in deep‐sea δ18O records, concealing the true periodicity of the glacial cycles in the two hemispheres.

• Straume, Eivind Olavson; Gaina, Carmen; Medvedev, Sergei & Nisancioglu, Kerim Hestnes (2020). Global Cenozoic Paleobathymetry with a focus on the Northern Hemisphere Oceanic Gateways. Gondwana Research. ISSN 1342-937X. 86, p. 126–143. doi: 10.1016/j.gr.2020.05.011. Full text in Research Archive
• Straume, Eivind Olavson; Gaina, Carmen; Medvedev, Sergei; Hochmuth, Karsten; Gohl, Karsten & Whittaker, Joanne M. [Show all 9 contributors for this article] (2019). GlobSed: Updated Total Sediment Thickness in the World's Oceans. Geochemistry Geophysics Geosystems. ISSN 1525-2027. 20(4), p. 1756–1772. doi: 10.1029/2018GC008115. Full text in Research Archive

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• Nisancioglu, Kerim Hestnes; Morée, Anne; Sun, Tianyi; Bretones, Anais Magali; Straume, Eivind Olavson & Gebbie, Geoffrey (2021). Cancellation of the precessional cycle in δ18O records during the Early Pleistocene. Show summary

  The dominant pacing of glacial‐interglacial cycles in deep‐ocean δ18O records changed substantially during the Mid‐Pleistocene Transition. The precessional cycle (∼23 ky) is absent during the Early Pleistocene, which we show can be explained by cancellation of the hemispherically anti‐phased precessional cycle in the Early Pleistocene interior ocean. Such cancellation develops due to mixing of North Atlantic and Southern Ocean δ18O signals at depth, and shows characteristic spatial patterns. We explore the cancellation potential for different North Atlantic and Southern Ocean deep‐water source δ18O values using a tracer transport ocean model. Cancellation of precession occurs for all signal strengths and is widespread for a signal strength typical for the Early Pleistocene. Early Pleistocene precessional power is therefore likely incompletely archived in deep‐sea δ18O records, concealing the true periodicity of the glacial cycles in the two hemispheres.

• Crameri, Fabio & Straume, Eivind Olavson (2019). Colour maps. [Internet]. A Slice of CEED.
• Morée, Anne; Sun, Tianyi; Bretones, Anaïs; Straume, Eivind Olavson; Nisancioglu, Kerim Hestnes & Gebbie, Geoffrey (2019). Cancellation of the precessional cycle in δ18O records during the Early Pleistocene. Show summary

  Deep-sea δ18O records show a pronounced difference in Milankovitch periodicity between the Early and Late Pleistocene. δ18O is interpreted as a proxy for ice sheet volume and temperature, which led to the conclusion that glacial-interglacial cycles considerably changed their rhythm during the mid-Pleistocene. This transition is referred to as the mid-Pleistocene Transition (MPT). Specifically, the precessional component of the Milankovitch cycles is absent in Early Pleistocene δ18O records, despite its continuous presence in solar insolation forcing to the ice sheets. Climate feedbacks involving (sea) ice, geological processes and carbon and nutrient cycling have been proposed as causes of this marked change. We however show that the absence of an Early Pleistocene precession signal in deep-sea δ18O records could be the result of destructive interference of the precessional cycle in the interior ocean. Such cancellation is caused by the anti-phasing of the precessional cycle between the North Atlantic and Southern Ocean deep-water sources (see Figure). We explore the potential for cancellation in the transient setup of the Total Matrix Intercomparison model for a wide range of source signal strengths. Our results show that cancellation can cause the absence of the precessional signal due to cancellation in the interior South-Atlantic, Indian and Pacific basins. Cancellation is especially widespread for a relative end-member contribution typical for the Early Pleistocene. We therefore conclude that the precessional component is likely incompletely archived in Early Pleistocene δ18O records, and appears as an actual change in Milankovitch periodicity across the MPT. Proxies not susceptible to cancellation of precession (such as those currently retrieved across the MPT from Antarctica) would be able to verify to what extent deep-sea δ18O correctly represents Pleistocene climate.

• Straume, Eivind Olavson; Morée, Anne; Nisancioglu, Kerim Hestnes & Gebbie, Geoffrey (2019). Orbital Forcing of Climate and the Mid-Pleistocene Transition . Show summary

  Climate archives, based on records of oxygen isotopes from marine sediments, show a pronounced change in the periodicity of the glacial cycles during the mid-Pleistocene (~1 million years ago). Before this time, and possibly from the initiation of major glaciations, the periodicity is dominated by the 41 kyr obliquity cycle of orbital insolation. However, in the past million years the ~21 and ~100 kyr cycles of precession and eccentricity have dominated the records of glacial cycles, and the records of atmospheric greenhouse gasses. This climate transition, the mid-Pleistocene Transition (MPT), is not fully understood. Nor are the dynamics of the glacial cycles. In this session we welcome contributions with perspectives on the MPT as well as the dynamics of the glacial cycles based on proxy records, theory and models. The topic is also timely in light of ongoing efforts to extract a continuous Antarctic ice core record spanning the MPT.

• Straume, Eivind Olavson; Gaina, Carmen & Medvedev, Sergei (2019). Cenozoic Paleobathymetry of the Northern Hemisphere Oceanic Gateways: Implications for Paleo-ocean Circulation and Climate.
• Straume, Eivind Olavson; Gaina, Carmen & Medvedev, Sergei (2019). Cenozoic paleobathymetry of the Atlantic-Arctic oceanic gateways: Iceland plume pulsations and implications on paleo-ocean circulation.
• Straume, Eivind Olavson; Gaina, Carmen; Gjermundsen, Ada; Lacasce, Joseph Henry; Klocker, Andreas & Nikurashin, Maxim (2018). Global Miocene paleobathymetry: implications for paleo-ocean circulation .
• Straume, Eivind Olavson (2018). Excursion, Diabasodden, Svalbard.
• Straume, Eivind Olavson (2017). Vulkanshow på Universitetsplassen i Oslo, i forbindelse med Forskningstorget 2017.
• Straume, Eivind Olavson (2017). Jordas oppbygning, og hvordan platetektonikk og vulkanisme kan forårsake klimaendringer.
• Straume, Eivind Olavson (2016). Plakat og formidling ved Forskningstorget 2016 .
• Straume, Eivind Olavson (2016). Jorda skifter ansikt: Tektonikk, vulkanisme og klimaendringer. Populærvitenskapelig foredrag i sammenheng med Ungforsk 2016.

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