Antarctic ice sheet evolution over the last glacial cycle: a data-constrained large-ensemble modelling approach

Briggs, Robert D. (2012) Antarctic ice sheet evolution over the last glacial cycle: a data-constrained large-ensemble modelling approach. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The Antarctic Ice Sheet (AIS) is an important component of the global climate system and has been identified as a major source of uncertainty to future sea level change. It is also one of the slowest components; much of the interior reacts on timescales greater than 10,000 years. To better understand the role Antarctica played in the global climate, the observed contemporaneous change, and to make predictions of its future behaviour, reconstructions of past ice sheet evolution are required. Furthermore, to interpret reconstructions with any degree of confidence, meaningful uncertainty estimates should be attributed. -- Glaciological modelling is an effective tool to generate continental-scale reconstructions over glacial cycles, but the models depend on parametrisations to account for the deficiencies (e.g., missing physics, poorly represented sub-grid processes, uncertain boundary conditions) inherent in any numerical model. These parameters, considered together, form a parameter-space from which sets of parameters can be sampled; each set corresponds to an ice sheet reconstruction. Previous modelling studies have relied upon a limited exploration of this space; furthermore few studies have employed the available observations to constrain the reconstructions. Large ( 0 ( 1000) member) ensemble analysis techniques have been effectively employed to explore the phase-space of models configured for other Quaternary ice sheets, but have yet to be applied to the AIS. -- This thesis documents a large-ensemble data-constrained study of the evolution of the AIS over the last glacial cycle. The contemporaneous glacial system model I use has been modified through the definition of 31 ensemble parameters that explore the uncertainty in t he ice-physics, the climate forcing, and the ice-ocean interaction. A database of constraint data with an associated evaluation methodology is used to compute probability distributions for ice sheet evolution. -- The reconstructions predict that the Last Glacial Maximum (LGM) in Antarctica occurred at ~24 ka BP, with deglaciation commencing after 8 ka BP, and that during the LGM the AIS contained 8.9 m equivalent sea level (mESL) in excess ice when compared to present day (with a 1σ upper and lower range of 5.8-12.2 mESL).

Item Type: Thesis (Doctoral (PhD))
URI: http://research.library.mun.ca/id/eprint/10210
Item ID: 10210
Additional Information: Includes bibliographical references.
Department(s): Science, Faculty of > Physics and Physical Oceanography
Date: 2012
Date Type: Submission
Library of Congress Subject Heading: Ice shelves--Antarctica--Mathematical models; Glacial climates--Mathematical models; Last Glacial Maximum--Antarctica; Set theory.

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