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  • 1
    Publication Date: 2016-08-29
    Description: Comparing simulations of key warm periods in Earth history with contemporaneous geological proxy data is a useful approach for evaluating the ability of climate models to simulate warm, high-CO2 climates that are unprecedented in the more recent past. Here we use a global data set of confidence-assessed, proxy-based temperature estimates and biome reconstructions to assess the ability of eight models to simulate warm terrestrial climates of the Pliocene epoch. The Late Pliocene, 3.6–2.6 million years ago, is an accessible geological interval to understand climate processes of a warmer world. We show that model-predicted surface air temperatures reveal a substantial cold bias in the Northern Hemisphere. Particularly strong data–model mismatches in mean annual temperatures (up to 18 °C) exist in northern Russia. Our model sensitivity tests identify insufficient temporal constraints hampering the accurate configuration of model boundary conditions as an important factor impacting on data–model discrepancies. We conclude that to allow a more robust evaluation of the ability of present climate models to predict warm climates, future Pliocene data–model comparison studies should focus on orbitally defined time slices.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 2
    Publication Date: 2023-03-10
    Description: The global climate has been gradually cooling over the Cenozoic and is punctuated by the intensification of Northern Hemisphere Glaciation (NHG) from the latest Pliocene to earliest Pleistocene (∼3.1–2.5 millions of years ago, Ma). A decline of atmospheric CO2 is supposed as a prerequisite for the NHG, but the associated carbon-cycle processes remain elusive. Here we combine foraminiferal records of neodymium isotope and boron-calcium ratio, and simulations of an Earth system model, to investigate changes in the water-mass composition and carbonate-ion concentration of the deep Pacific Ocean during the NHG. Our proxy records have revealed a significant expansion of southern-sourced waters with increased respired carbon storage into the deep Pacific during the NHG. These changes may be explained by strengthened deep-water formation and biological-pump efficiency in the Southern Ocean due to Antarctic sea-ice growth, as suggested by our model experiments and evidence from the Sub-Antarctic region. These results provide key clues for quantifying the role of the dissolved inorganic carbon content of deep Pacific waters in modulating atmospheric CO2 during the NHG.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Location Call Number Limitation Availability
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