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You searched for +publisher:"University of Victoria" +contributor:("Monahan, A."). Showing records 1 – 2 of 2 total matches.

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University of Victoria

1. Mueller, Bennit L. Attribution of Arctic sea ice decline from 1953 to 2012 to influences from natural, greenhouse-gas and anthropogenic aerosol forcing.

Degree: School of Earth and Ocean Sciences, 2016, University of Victoria

By the end of 2016 surveillance and reconnaissance satellites will have been monitoring Arctic-wide sea ice conditions for decades. Situated at the boundary between atmosphere and ocean, Arctic sea ice retreat has been one of the most conspicuous indication of climate change, especially in the two most recent decades. The 2001 annual minimum extent of Arctic sea ice marks the last year above the 1981  – 2012 long-term average extent. Ever since then only lower than average Arctic sea ice has been observed at the end of each summer's melt season. For more than a century climate scientists have postulated that the darkening of the Arctic due to retreating sea ice and therefore more exposed open ocean would be the consequence of global warming. In the first decade of the 2000s the human influence on that warming in the Arctic was indeed detected in observations and attributed to increasing atmospheric greenhouse-gas concentrations. In this study we direct our attention to a potential offsetting effect from other anthropogenic (OANT) forcing agents, mainly aerosols, that has potentially out masked a fraction of greenhouse-gas induced warming by a combined cooling effect. We acknowledge that multiple sources of uncertainty exist in our method, in particular in the observed records of Arctic sea ice and corresponding simulations from climate models. No formal detection and attribution (DA) analysis has yet been carried out to try to detect the combined cooling effect from aerosols in observations of Arctic sea ice extent. We use three publicly available observational data sets of Arctic sea ice and climate simulations from eight models of the Coupled Model Intercomparison Project Phase 5 (CMIP5). In our detection and attribution study observations are regressed on model-derived climate response pattern, or fingerprints, under all known historical (ALL), greenhouse-gas only (GHG) and known natural-only (NAT) forcing factors using an optimal fingerprinting method. We estimate regression coefficients (scaling factors) for each forcing group that scale the fingerprints to best match the observed record. From the scaled ALL, GHG and NAT fingerprints we calculate the relative contribution of the observed sea ice decline attributable to OANT forcing agent. Based on our DA results we show that the simulated climate response patterns to changes in GHG, OANT and NAT forcing are detected in the observed records of September Arctic sea ice extent for the 1953 to 2012 period. Advisors/Committee Members: Gillett, N. P. (supervisor), Monahan, A. (supervisor).

Subjects/Keywords: detection and attribution; Arctic; sea ice; climate change; CMIP5

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APA (6th Edition):

Mueller, B. L. (2016). Attribution of Arctic sea ice decline from 1953 to 2012 to influences from natural, greenhouse-gas and anthropogenic aerosol forcing. (Masters Thesis). University of Victoria. Retrieved from http://hdl.handle.net/1828/7669

Chicago Manual of Style (16th Edition):

Mueller, Bennit L. “Attribution of Arctic sea ice decline from 1953 to 2012 to influences from natural, greenhouse-gas and anthropogenic aerosol forcing.” 2016. Masters Thesis, University of Victoria. Accessed April 05, 2020. http://hdl.handle.net/1828/7669.

MLA Handbook (7th Edition):

Mueller, Bennit L. “Attribution of Arctic sea ice decline from 1953 to 2012 to influences from natural, greenhouse-gas and anthropogenic aerosol forcing.” 2016. Web. 05 Apr 2020.

Vancouver:

Mueller BL. Attribution of Arctic sea ice decline from 1953 to 2012 to influences from natural, greenhouse-gas and anthropogenic aerosol forcing. [Internet] [Masters thesis]. University of Victoria; 2016. [cited 2020 Apr 05]. Available from: http://hdl.handle.net/1828/7669.

Council of Science Editors:

Mueller BL. Attribution of Arctic sea ice decline from 1953 to 2012 to influences from natural, greenhouse-gas and anthropogenic aerosol forcing. [Masters Thesis]. University of Victoria; 2016. Available from: http://hdl.handle.net/1828/7669


University of Victoria

2. Godlovitch, Daniel. Idealised models of sea ice thickness dynamics.

Degree: School of Earth and Ocean Sciences, 2013, University of Victoria

Thickness distributions of sea ice (g(h)) display a ubiquitous exponential decay (’tail’) in ice above approximately 2 meters thick. This work uses idealised models to examine the root causes of the exponential tail of the sea ice thickness distribution. The ice of thickness greater than 2 meters is formed through the fracture and piling of ice caused by interactions between floes, driven by winds and currents. The material properties of sea ice are complex and mathematical descriptions of the relationship between force and deformation of a floe are still a topic of study. Smoluchowski Coagulation Models (SCMs) are used to develop an abstract representation of redistribution dynamics. SCMs describe populations whose members of fixed size combine at size-dependent rates. SCMs naturally produce exponential or quasi-exponential distributions. An SCM coupled with a thermodynamic component produces qualitatively realistic g(h) under a wide range of conditions. Using the abstract representation of redistribution dynamics from SCMs, a model developed from physical processes specific to sea ice is introduced. Redistribution events occur at rates dependent on the change in potential energy. This model is demonstrated to produce qualitatively realistic g(h). Sensitivity analysis shows that primary model sensitivities are to the relative strengths of the dynamic and thermodynamic components of the model; and to the relative occurrence of ice ridging, shearing and rafting. The exact relationship between the rate of redistribution events and the energy they consume is shown to be of lesser importance. We conclude that the exponential tail of g(h) is a mathematical consequence of the coagulative nature of the ice thickness redistribution process, rather than the material properties of sea ice. These model results suggest the strongest controls on the form of the tail are the relative strengths of thermodynamic and dynamic action, and the relative occurrence of ice ridging, shearing and rafting. Advisors/Committee Members: Monahan, A. (supervisor), Flato, G. (supervisor).

Subjects/Keywords: sea ice; ice thickness; climate change

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Godlovitch, D. (2013). Idealised models of sea ice thickness dynamics. (Thesis). University of Victoria. Retrieved from http://hdl.handle.net/1828/4923

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Godlovitch, Daniel. “Idealised models of sea ice thickness dynamics.” 2013. Thesis, University of Victoria. Accessed April 05, 2020. http://hdl.handle.net/1828/4923.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Godlovitch, Daniel. “Idealised models of sea ice thickness dynamics.” 2013. Web. 05 Apr 2020.

Vancouver:

Godlovitch D. Idealised models of sea ice thickness dynamics. [Internet] [Thesis]. University of Victoria; 2013. [cited 2020 Apr 05]. Available from: http://hdl.handle.net/1828/4923.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Godlovitch D. Idealised models of sea ice thickness dynamics. [Thesis]. University of Victoria; 2013. Available from: http://hdl.handle.net/1828/4923

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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