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      Snapshots of the Greenland ice sheet configuration in the Pliocene to early Pleistocene

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          Abstract

          The geometry of the ice sheets during the Pliocene to early Pleistocene is not well constrained. Here we apply an ice-flow model in the study of the Greenland ice sheet (GIS) during three extreme intervals of this period constrained by geological observations and climate reconstructions. We study the extent of the GIS during the Mid-Pliocene Warmth (3.3–3.0 Ma), its advance across the continental shelf during the late Pliocene to early Pleistocene glaciations (3.0–2.4 Ma) as implied by offshore geological studies, and the transition from glacial to interglacial conditions around 2.4 Ma as deduced from the deposits of the Kap København Formation, North Greenland. Our experiments show that no coherent ice sheet is likely to have existed in Greenland during the Mid-Pliocene Warmth and that only local ice caps may have been present in the coastal mountains of East Greenland. Our results illustrate the variability of the GIS during the Pliocene to early Pleistocene and underline the importance of including independent estimates of the GIS in studies of climate during this period. We conclude that the GIS did not exist throughout the Pliocene to early Pleistocene, and that it melted during interglacials even during the late Pliocene climate deterioration.

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          Ancient biomolecules from deep ice cores reveal a forested southern Greenland.

          It is difficult to obtain fossil data from the 10% of Earth's terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the basal sections of deep ice cores, enabling reconstructions of past flora and fauna. We show that high-altitude southern Greenland, currently lying below more than 2 kilometers of ice, was inhabited by a diverse array of conifer trees and insects within the past million years. The results provide direct evidence in support of a forested southern Greenland and suggest that many deep ice cores may contain genetic records of paleoenvironments in their basal sections.
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            Palaeo-ice streams

            C. Stokes (2001)
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              Increased seasonality through the Eocene to Oligocene transition in northern high latitudes.

              A profound global climate shift took place at the Eocene-Oligocene transition ( approximately 33.5 million years ago) when Cretaceous/early Palaeogene greenhouse conditions gave way to icehouse conditions. During this interval, changes in the Earth's orbit and a long-term drop in atmospheric carbon dioxide concentrations resulted in both the growth of Antarctic ice sheets to approximately their modern size and the appearance of Northern Hemisphere glacial ice. However, palaeoclimatic studies of this interval are contradictory: although some analyses indicate no major climatic changes, others imply cooler temperatures, increased seasonality and/or aridity. Climatic conditions in high northern latitudes over this interval are particularly poorly known. Here we present northern high-latitude terrestrial climate estimates for the Eocene to Oligocene interval, based on bioclimatic analysis of terrestrially derived spore and pollen assemblages preserved in marine sediments from the Norwegian-Greenland Sea. Our data indicate a cooling of approximately 5 degrees C in cold-month (winter) mean temperatures to 0-2 degrees C, and a concomitant increased seasonality before the Oi-1 glaciation event. These data indicate that a cooling component is indeed incorporated in the delta(18)O isotope shift across the Eocene-Oligocene transition. However, the relatively warm summer temperatures at that time mean that continental ice on East Greenland was probably restricted to alpine outlet glaciers.
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                Author and article information

                Journal
                applab
                Journal of Glaciology
                J. Glaciol.
                Cambridge University Press (CUP)
                0022-1430
                1727-5652
                2011
                September 8 2017
                : 57
                : 205
                : 871-880
                Article
                10.3189/002214311798043816
                5579006e-dbed-42e6-a758-fd1c2d890259
                © 2017
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