A Climate Model of the Deep (Neoproterozoic) Past
It has been commonly recognized that a series of global glaciation events occurred during the late Neoproterozoic Era (800 - 540 million years ago (Ma)). However, the extent of these glaciations continues to be hotly debated, namely whether the whole Earth was ice covered (ie. a “hard snowball”) or...
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ftcanadathes:oai:collectionscanada.gc.ca:OTU.1807/29792 2023-05-15T16:40:55+02:00 A Climate Model of the Deep (Neoproterozoic) Past Liu, Yonggang Peltier, William Richard 2011-06 http://hdl.handle.net/1807/29792 en_ca eng http://hdl.handle.net/1807/29792 Snowball Earth Neoproterozoic Paleoclimate Carbon cycle 0725 Thesis 2011 ftcanadathes 2014-02-09T00:43:16Z It has been commonly recognized that a series of global glaciation events occurred during the late Neoproterozoic Era (800 - 540 million years ago (Ma)). However, the extent of these glaciations continues to be hotly debated, namely whether the whole Earth was ice covered (ie. a “hard snowball”) or only the continents were fully ice covered but the oceans were not (“slushball/soft snowball”). Through a combination of climate modeling and carbon cycle modeling, I have investigated the plausibility of the “soft snowball” Earth hypothesis. It is demonstrated that the flow of land ice is critical to the formation of a “soft snowball”, such that low latitude land ice must be generated through ice transported from high latitudes. In order for a climate state of this kind to be realizable, continental fragments at low latitude must be well connected to those at high latitude, and the high latitude continents must be sufficiently extensive that a large ice sheet may initiate and subsequently flow to low latitude. It is found that these constraints are satisfied by the most accurate available continental reconstruction for both the initial Sturtian glaciation of the late Neoproterozoic and the subsequent Marinoan event. It is furthermore proposed that the alternative “hard snowball” hypothesis would have been prevented by a negative feedback due to the enhanced remineralization of dissolved organic carbon (DOC) in the ocean due to increased oxygen solubility in seawater at lower temperature. This process would release CO2 to the atmosphere, thus counteracting the initial climate cooling. I have also carried out detailed simulations in which an explicit model of the carbon cycle is coupled to the ice-sheet coupled climate model to investigate this feedback quantitatively. It is found that the remineralization of the DOC does indeed provide a strong negative feedback that counteracts climate cooling. The action of this feedback not only prevents the descent of the climate into a hard snowball state, but also enables the model to re-produce the δ13C carbon isotopic anomalies observed to accompany Neoproterozoic glacial events. The resistance of this carbon cycle coupled climate system to descent into a “hard snowball” state is further tested against stochastic perturbations, and shown to be robust in the presence of such influence. Thesis Ice Sheet Theses Canada/Thèses Canada (Library and Archives Canada) |
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Open Polar |
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Theses Canada/Thèses Canada (Library and Archives Canada) |
op_collection_id |
ftcanadathes |
language |
English |
topic |
Snowball Earth Neoproterozoic Paleoclimate Carbon cycle 0725 |
spellingShingle |
Snowball Earth Neoproterozoic Paleoclimate Carbon cycle 0725 Liu, Yonggang A Climate Model of the Deep (Neoproterozoic) Past |
topic_facet |
Snowball Earth Neoproterozoic Paleoclimate Carbon cycle 0725 |
description |
It has been commonly recognized that a series of global glaciation events occurred during the late Neoproterozoic Era (800 - 540 million years ago (Ma)). However, the extent of these glaciations continues to be hotly debated, namely whether the whole Earth was ice covered (ie. a “hard snowball”) or only the continents were fully ice covered but the oceans were not (“slushball/soft snowball”). Through a combination of climate modeling and carbon cycle modeling, I have investigated the plausibility of the “soft snowball” Earth hypothesis. It is demonstrated that the flow of land ice is critical to the formation of a “soft snowball”, such that low latitude land ice must be generated through ice transported from high latitudes. In order for a climate state of this kind to be realizable, continental fragments at low latitude must be well connected to those at high latitude, and the high latitude continents must be sufficiently extensive that a large ice sheet may initiate and subsequently flow to low latitude. It is found that these constraints are satisfied by the most accurate available continental reconstruction for both the initial Sturtian glaciation of the late Neoproterozoic and the subsequent Marinoan event. It is furthermore proposed that the alternative “hard snowball” hypothesis would have been prevented by a negative feedback due to the enhanced remineralization of dissolved organic carbon (DOC) in the ocean due to increased oxygen solubility in seawater at lower temperature. This process would release CO2 to the atmosphere, thus counteracting the initial climate cooling. I have also carried out detailed simulations in which an explicit model of the carbon cycle is coupled to the ice-sheet coupled climate model to investigate this feedback quantitatively. It is found that the remineralization of the DOC does indeed provide a strong negative feedback that counteracts climate cooling. The action of this feedback not only prevents the descent of the climate into a hard snowball state, but also enables the model to re-produce the δ13C carbon isotopic anomalies observed to accompany Neoproterozoic glacial events. The resistance of this carbon cycle coupled climate system to descent into a “hard snowball” state is further tested against stochastic perturbations, and shown to be robust in the presence of such influence. |
author2 |
Peltier, William Richard |
format |
Thesis |
author |
Liu, Yonggang |
author_facet |
Liu, Yonggang |
author_sort |
Liu, Yonggang |
title |
A Climate Model of the Deep (Neoproterozoic) Past |
title_short |
A Climate Model of the Deep (Neoproterozoic) Past |
title_full |
A Climate Model of the Deep (Neoproterozoic) Past |
title_fullStr |
A Climate Model of the Deep (Neoproterozoic) Past |
title_full_unstemmed |
A Climate Model of the Deep (Neoproterozoic) Past |
title_sort |
climate model of the deep (neoproterozoic) past |
publishDate |
2011 |
url |
http://hdl.handle.net/1807/29792 |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_relation |
http://hdl.handle.net/1807/29792 |
_version_ |
1766031345648140288 |