albedo
; atmospheric general circulation model
; carbon dioxide
; climate oscillation
; concentration (composition)
; geological record
; glacial-interglacial cycle
; glaciation
; glacier advance
; ice cover
; ice sheet
; orbital forcing
; oxygen isotope
; paleolatitude
; Proterozoic
; sedimentology
; sulfur isotope
; threshold
; warming
; Arctic
; Svalbard
; Svalbard and Jan Mayen
英文摘要:
Two global glaciations occurred during the Neoproterozoic. Snowball Earth theory posits that these were terminated after millions of years of frigidity when initial warming from rising atmospheric CO2concentrations was amplified by the reduction of ice cover and hence a reduction in planetary albedo. This scenario implies that most of the geological record of ice cover was deposited in a brief period of melt-back. However, deposits in low palaeo-latitudes show evidence of glacial-interglacial cycles. Here we analyse the sedimentology and oxygen and sulphur isotopic signatures of Marinoan Snowball glaciation deposits from Svalbard, in the Norwegian High Arctic. The deposits preserve a record of oscillations in glacier extent and hydrologic conditions under uniformly high atmospheric CO2concentrations. We use simulations from a coupled three-dimensional ice sheet and atmospheric general circulation model to show that such oscillations can be explained by orbital forcing in the late stages of a Snowball glaciation. The simulations suggest that while atmospheric CO2concentrations were rising, but not yet at the threshold required for complete melt-back, the ice sheets would have been sensitive to orbital forcing. We conclude that a similar dynamic can potentially explain the complex successions observed at other localities.
Department of Geology, University Centre in Svalbard (UNIS), Longyearbyen, Norway; School of Geography and Geosciences, University of St.Andrews, St.Andrews, United Kingdom; Institut de Physique du Globe de Paris, Paris, France; Department of Geology and Geophysics, E235 Howe-Russell Complex, Louisiana State University, Baton Rouge, LA, United States; Laboratoire des Sciences du Climat et de l'Environnement, CNRS-CEA, Gif-sur-Yvette, France; School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom; Institute of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, United Kingdom; Natural Resource Management, Environmental Geology, New Mexico Highlands University, Las Vegas, NM, United States; Lancaster Environment Centre, University of Lancaster, Lancaster, United Kingdom; CASP, West Building, 181A Huntingdon Road, Cambridge, United Kingdom
Recommended Citation:
Benn D.I.,Le Hir G.,Bao H.,et al. Orbitally forced ice sheet fluctuations during the Marinoan Snowball Earth glaciation[J]. Nature Geoscience,2015-01-01,8(9)