Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins
The Snowball Earth bifurcation, or runaway ice-albedo feedback, is defined for particular boundary conditions by a critical CO 2 and a critical sea-ice cover (SI), both of which are essential for evaluating hypotheses related to Neoproterozoic glaciations. Previous work has shown that the Snowball E...
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ftdoajarticles:oai:doaj.org/article:aa77f627d8c64dbabdd97aeb92dce771 2023-05-15T18:16:07+02:00 Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins A. Voigt D. S. Abbot 2012-12-01T00:00:00Z https://doi.org/10.5194/cp-8-2079-2012 https://doaj.org/article/aa77f627d8c64dbabdd97aeb92dce771 EN eng Copernicus Publications http://www.clim-past.net/8/2079/2012/cp-8-2079-2012.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-8-2079-2012 1814-9324 1814-9332 https://doaj.org/article/aa77f627d8c64dbabdd97aeb92dce771 Climate of the Past, Vol 8, Iss 6, Pp 2079-2092 (2012) Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 article 2012 ftdoajarticles https://doi.org/10.5194/cp-8-2079-2012 2022-12-31T14:37:55Z The Snowball Earth bifurcation, or runaway ice-albedo feedback, is defined for particular boundary conditions by a critical CO 2 and a critical sea-ice cover (SI), both of which are essential for evaluating hypotheses related to Neoproterozoic glaciations. Previous work has shown that the Snowball Earth bifurcation, denoted as (CO 2 , SI) * , differs greatly among climate models. Here, we study the effect of bare sea-ice albedo, sea-ice dynamics and ocean heat transport on (CO 2 , SI) * in the atmosphere–ocean general circulation model ECHAM5/MPI-OM with Marinoan (~ 635 Ma) continents and solar insolation (94% of modern). In its standard setup, ECHAM5/MPI-OM initiates a~Snowball Earth much more easily than other climate models at (CO 2 , SI) * ≈ (500 ppm, 55%). Replacing the model's standard bare sea-ice albedo of 0.75 by a much lower value of 0.45, we find (CO 2 , SI) * ≈ (204 ppm, 70%). This is consistent with previous work and results from net evaporation and local melting near the sea-ice margin. When we additionally disable sea-ice dynamics, we find that the Snowball Earth bifurcation can be pushed even closer to the equator and occurs at a hundred times lower CO 2 : (CO 2 , SI) * ≈ (2 ppm, 85%). Therefore, the simulation of sea-ice dynamics in ECHAM5/MPI-OM is a dominant determinant of its high critical CO 2 for Snowball initiation relative to other models. Ocean heat transport has no effect on the critical sea-ice cover and only slightly decreases the critical CO 2 . For disabled sea-ice dynamics, the state with 85% sea-ice cover is stabilized by the Jormungand mechanism and shares characteristics with the Jormungand climate states. However, there is no indication of the Jormungand bifurcation and hysteresis in ECHAM5/MPI-OM. The state with 85% sea-ice cover therefore is a soft Snowball state rather than a true Jormungand state. Overall, our results demonstrate that differences in sea-ice dynamics schemes can be at least as important as differences in sea-ice albedo for causing the spread in climate ... Article in Journal/Newspaper Sea ice Directory of Open Access Journals: DOAJ Articles Climate of the Past 8 6 2079 2092 |
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Directory of Open Access Journals: DOAJ Articles |
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ftdoajarticles |
language |
English |
topic |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
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Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 A. Voigt D. S. Abbot Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins |
topic_facet |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
description |
The Snowball Earth bifurcation, or runaway ice-albedo feedback, is defined for particular boundary conditions by a critical CO 2 and a critical sea-ice cover (SI), both of which are essential for evaluating hypotheses related to Neoproterozoic glaciations. Previous work has shown that the Snowball Earth bifurcation, denoted as (CO 2 , SI) * , differs greatly among climate models. Here, we study the effect of bare sea-ice albedo, sea-ice dynamics and ocean heat transport on (CO 2 , SI) * in the atmosphere–ocean general circulation model ECHAM5/MPI-OM with Marinoan (~ 635 Ma) continents and solar insolation (94% of modern). In its standard setup, ECHAM5/MPI-OM initiates a~Snowball Earth much more easily than other climate models at (CO 2 , SI) * ≈ (500 ppm, 55%). Replacing the model's standard bare sea-ice albedo of 0.75 by a much lower value of 0.45, we find (CO 2 , SI) * ≈ (204 ppm, 70%). This is consistent with previous work and results from net evaporation and local melting near the sea-ice margin. When we additionally disable sea-ice dynamics, we find that the Snowball Earth bifurcation can be pushed even closer to the equator and occurs at a hundred times lower CO 2 : (CO 2 , SI) * ≈ (2 ppm, 85%). Therefore, the simulation of sea-ice dynamics in ECHAM5/MPI-OM is a dominant determinant of its high critical CO 2 for Snowball initiation relative to other models. Ocean heat transport has no effect on the critical sea-ice cover and only slightly decreases the critical CO 2 . For disabled sea-ice dynamics, the state with 85% sea-ice cover is stabilized by the Jormungand mechanism and shares characteristics with the Jormungand climate states. However, there is no indication of the Jormungand bifurcation and hysteresis in ECHAM5/MPI-OM. The state with 85% sea-ice cover therefore is a soft Snowball state rather than a true Jormungand state. Overall, our results demonstrate that differences in sea-ice dynamics schemes can be at least as important as differences in sea-ice albedo for causing the spread in climate ... |
format |
Article in Journal/Newspaper |
author |
A. Voigt D. S. Abbot |
author_facet |
A. Voigt D. S. Abbot |
author_sort |
A. Voigt |
title |
Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins |
title_short |
Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins |
title_full |
Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins |
title_fullStr |
Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins |
title_full_unstemmed |
Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins |
title_sort |
sea-ice dynamics strongly promote snowball earth initiation and destabilize tropical sea-ice margins |
publisher |
Copernicus Publications |
publishDate |
2012 |
url |
https://doi.org/10.5194/cp-8-2079-2012 https://doaj.org/article/aa77f627d8c64dbabdd97aeb92dce771 |
genre |
Sea ice |
genre_facet |
Sea ice |
op_source |
Climate of the Past, Vol 8, Iss 6, Pp 2079-2092 (2012) |
op_relation |
http://www.clim-past.net/8/2079/2012/cp-8-2079-2012.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-8-2079-2012 1814-9324 1814-9332 https://doaj.org/article/aa77f627d8c64dbabdd97aeb92dce771 |
op_doi |
https://doi.org/10.5194/cp-8-2079-2012 |
container_title |
Climate of the Past |
container_volume |
8 |
container_issue |
6 |
container_start_page |
2079 |
op_container_end_page |
2092 |
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1766189557734178816 |