Browsing by Author "Sluijs, Appy"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Assessing offsets between the δ13C of sedimentary components and the global exogenic carbon pool across early Paleogene carbon cycle perturbations
    (Wiley, 2012) Sluijs, Appy; Dickens, Gerald R.
    [1] Negative stable carbon isotope excursions (CIEs) across the Paleocene–Eocene thermal maximum (PETM; ~56 Ma) range between 2‰ and 7‰, even after discounting sections with truncated records. Individual carbon isotope records differ in shape and magnitude from variations in the global exogenic carbon cycle through changes in (1) the relative abundance of mixed components with different δ13C within a measured substrate, (2) isotope fractionation through physiological change, and (3) the isotope composition of the carbon source. All three factors likely influence many early Paleogene δ13C records, especially across the PETM and other hyperthermal events. We apply these concepts to late Paleocene–early Eocene (∼58–52 Ma) records from Lomonosov Ridge, Arctic Ocean. Linear regression analyses show correlations between the δ13C of total organic carbon (TOC) and two proxies for the relative contribution of terrestrial organic components to sediment TOC: the branched and isoprenoid tetraether index and palynomorphs. We use these correlations to subtract the terrestrial component from δ13CTOC and calculate marine organic matter δ13C. The results show that the magnitude of the CIE in δ13CTOC across the PETM is exaggerated relative to the magnitude of the CIE in δ13CMOM by ~3‰ due to increased contributions of terrestrial organic carbon during the event. Collectively, all carbon isotope records across the PETM and other major climate–carbon cycle perturbations in Earth's history are potentially biased through one or more of the above factors. Indeed, it is highly unlikely that any δ13C record shows the true shape and magnitude of the CIE for the global exogenic carbon cycle. For the PETM, we conclude that CIE in the exogenic carbon cycle is likely <4‰, but it will take additional analyses and modeling to obtain an accurate value for this CIE.
  • Thumbnail Image
    Item
    Large-Amplitude Variations in Carbon Cycling and Terrestrial Weathering during the Latest Paleocene and Earliest Eocene: The Record at Mead Stream, New Zealand
    (University of Chicago Press, 2012) Slotnick, Benjamin S.; Dickens, Gerald R.; Nicolo, Micah J.; Hollis, Christopher J.; Crampton, James S.; Zachos, James C.; Sluijs, Appy
    The late Paleocene to early Eocene was marked by major changes in Earth surface temperature and carbon cycling. This included at least two, and probably more, geologically brief (<200-k.yr.) intervals of extreme warming, the Paleocene-Eocene thermal maximum (PETM) and the Eocene thermal maximum-2 (ETM-2). The long-term rise in warmth and short-term “hyperthermal” events have been linked to massive injections of 13C-depleted carbon into the ocean-atmosphere system and intense global climate change. However, the causes, environmental impact, and relationships remain uncertain because detailed and coupled proxy records do not extend across the entire interval of interest; we are still recognizing the exact character of the hyperthermals and developing models to explain their occurrence. Here we present lithologic and carbon isotope records for a 200-m-thick sequence of latest Paleocene– earliest Eocene upper slope limestone exposed along Mead Stream, New Zealand. New carbon isotope and lithologic analyses combined with previous work on this expanded section shows that the PETM and ETM-2, the suspected H-2, I-1, I-2, and K/X hyperthermals, and several other horizons are marked by pronounced negative carbon isotope excursions and clay-rich horizons. Generally, the late Paleocene–early Eocene lithologic and δ¹³C records at Mead Stream are similar to records recovered from deep-sea sites, with an important exception: lows in δ¹³C and carbonate content consistently span intervals of relatively high sedimentation (terrigenous dilution) rather than intervals of relatively low sedimentation (carbonate dissolution). These findings indicate that, over ~6 m.yr., there was a series of short-termclimate perturbations, each characterized by massive input of carbon and greater continental weathering. The suspected link involves global warming, elevated greenhouse-gas concentrations, and enhanced seasonal precipitation.
  • Thumbnail Image
    Item
    The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database
    (Copernicus Publications, 2019) Hollis, Christopher J.; Dunkley Jones, Tom; Anagnostou, Eleni; Bijl, Peter K.; Cramwinckel, Margot J.; Cui, Ying; Dickens, Gerald R.; Edgar, Kirsty M.; Eley, Yvette; Evans, David; Foster, Gavin L.; Frieling, Joost; Inglis, Gordon N.; Kennedy, Elizabeth M.; Kozdon, Reinhard; Lauretano, Vittoria; Lear, Caroline H.; Littler, Kate; Lourens, Lucas; Meckler, A. Nele; Naafs, B. David A.; Pälike, Heiko; Pancost, Richard D.; Pearson, Paul N.; Röhl, Ursula; Royer, Dana L.; Salzmann, Ulrich; Schubert, Brian A.; Seebeck, Hannu; Sluijs, Appy; Speijer, Robert P.; Stassen, Peter; Tierney, Jessica; Tripati, Aradhna; Wade, Bridget; Westerhold, Thomas; Witkowski, Caitlyn; Zachos, James C.; Zhang, Yi Ge; Huber, Matthew; Lunt, Daniel J.
    The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that Earth's atmospheric CO2 concentrations exceeded 1000 ppm. Global mean temperatures were also substantially warmer than those of the present day. As such, the study of early Eocene climate provides insight into how a super-warm Earth system behaves and offers an opportunity to evaluate climate models under conditions of high greenhouse gas forcing. The Deep Time Model Intercomparison Project (DeepMIP) is a systematic model–model and model–data intercomparison of three early Paleogene time slices: latest Paleocene, Paleocene–Eocene thermal maximum (PETM) and early Eocene climatic optimum (EECO). A previous article outlined the model experimental design for climate model simulations. In this article, we outline the methodologies to be used for the compilation and analysis of climate proxy data, primarily proxies for temperature and CO2. This paper establishes the protocols for a concerted and coordinated effort to compile the climate proxy records across a wide geographic range. The resulting climate “atlas” will be used to constrain and evaluate climate models for the three selected time intervals and provide insights into the mechanisms that control these warm climate states. We provide version 0.1 of this database, in anticipation that this will be expanded in subsequent publications.