An alternative suggestion for the Pliocene onset of major northern hemisphere glaciation based on the geochemical provenance of North Atlantic Ocean ice-rafted debris

The emergence of modern sea ice cover in the Arctic Ocean

“…These attributes are of particular significance to the current study, as it has previously been shown that ice marginal conditions in the gateway (Fram Strait) are mirrored, qualitatively, by the occurrence of IP 25 in marine sediments from the study region, and that sedimentary abundances of IP 25 are sensitive to changes in sea ice conditions 17,18 , thus permitting semi-quantitative reconstructions. As a result, the measurement of IP 25 in AAG sediments covering the last 2 Ma has been used to imply marginal sea ice conditions during the Pleistocene 19 . The new IP 25 record from the AAG shows that sea ice expanded from the Arctic Ocean to its modern limits for the first time ca.…”

“…The presence (absence) of IP 25 in Arctic marine sediments is especially sensitive to the past occurrence (absence) of sea ice 16 , while abundance variations are usually consistent with corresponding directional changes in sea ice cover 16 . These attributes are of particular significance to the current study, as it has previously been shown that ice marginal conditions in the gateway (Fram Strait) are mirrored, qualitatively, by the occurrence of IP 25 in marine sediments from the study region, and that sedimentary abundances of IP 25 are sensitive to changes in sea ice conditions 17,18 , thus permitting semi-quantitative reconstructions. As a result, the measurement of IP 25 in AAG sediments covering the last 2 Ma has been used to imply marginal sea ice conditions during the Pleistocene 19 .…”

“…1). In recent years, the analysis of the biomarker IP 25 ('Ice Proxy with 25 carbon atoms') 14 , a mono-unsaturated highly branched isoprenoid lipid biosynthesized by certain sea ice diatoms 15 , has become an established proxy method for the reconstruction of Arctic sea ice 16 . The presence (absence) of IP 25 in Arctic marine sediments is especially sensitive to the past occurrence (absence) of sea ice 16 , while abundance variations are usually consistent with corresponding directional changes in sea ice cover 16 .…”

“…In recent years, the analysis of the biomarker IP 25 ('Ice Proxy with 25 carbon atoms') 14 , a mono-unsaturated highly branched isoprenoid lipid biosynthesized by certain sea ice diatoms 15 , has become an established proxy method for the reconstruction of Arctic sea ice 16 . The presence (absence) of IP 25 in Arctic marine sediments is especially sensitive to the past occurrence (absence) of sea ice 16 , while abundance variations are usually consistent with corresponding directional changes in sea ice cover 16 . These attributes are of particular significance to the current study, as it has previously been shown that ice marginal conditions in the gateway (Fram Strait) are mirrored, qualitatively, by the occurrence of IP 25 in marine sediments from the study region, and that sedimentary abundances of IP 25 are sensitive to changes in sea ice conditions 17,18 , thus permitting semi-quantitative reconstructions.…”

Evolution of the early Antarctic ice ages

“…Deep-sea proxy records and sedimentological evidence from the Antarctic continental shelves indicate the expansion of continental-size ice sheets on Antarctica at the EOT (2,3), and sedimentary records from the western Ross Sea on the East Antarctic margin document large subsequent oscillations in ice sheet extent on astronomical time scales during the Oligo-Miocene (4). In contrast, large ice sheets did not develop in the high northern latitudes until the Late Pliocene (5). Thus, the Oligo-Miocene presents an opportunity to study the dynamics of a unipolar (Antarctic) icehouse climate state without the overprint of Northern Hemisphere ice sheets on benthic foraminiferal δ 18 O records.…”