HR: 08:30h
AN: C11B-03 INVITED     [Abstracts]
TI: Far-Field Post-Glacial Sea-Level Geometries as a Probe of Antarctic Ice History
AU: * Mitrovica, J X
EM: jxm@physics.utoronto.ca
AF: University of Toronto, Department of Physics, 60. St. George Street, Toronto, ON M5S 1A7 Canada
AU: Bassett, S E
EM: s.e.bassett@durham.ac.uk
AF: University of Durham, Department of Earth Sciences, Durham, DH1 3LE United Kingdom
AU: Clark, P U
EM: clarkp@ucs.orst.edu
AF: Oregon State University, Department of Geosciences, Corvallis, OR 97331 United States
AU: Milne, G A
EM: g.a.milne@durham.ac.uk
AF: University of Durham, Department of Earth Sciences, Durham, DH1 3LE United Kingdom
AB: Sea-level observations in the far-field of the Late Pleistocene ice sheets are a sensitive probe of ice-age climate change. As an example, the high resolution Barbados record of sea-level rise during the last deglaciation reveals a highly non-uniform melt history, with relatively stable conditions punctuated by rapid meltwater events; the latter includes meltwater pulse (mwp) 1B at 11.5 cal kyr BP, in which sea level rose approximately 10 m, and the extraordinary mwp-1A event characterized by a 20-25 m sea-level rise beginning at 14.2 cal kyr BP. Despite the fundamental connection between these events and ice-age climate, several key issues remain highly contentious. For example, the specific ice sheets responsible for mwp-1A remain uncertain. Moreover, the existence of mwp-1B is questioned since a sea-level rise of similar timing and magnitude has not been identified in other far-field records. Finally, numerical models of glacial isostatic adjustment (GIA) in which preferred combinations of ice history and Earth structure have yielded good fits to the Barbados record show enigmatically large misfits to Lateglacial (14-9 cal kyr BP) data at other far-field sites (e.g, Tahiti, Huon Peninsula and Sunda Shelf). The large (order 30 m) discrepancies at Huon Peninsula and Tahiti have motivated suggestions that the habitation depth of some coral species and/or the tectonic corrections applied to the raw sea-level markers are uncertain. In this talk, I review our recent efforts to robustly answer these issues using the spatial geometry and temporal variability in far-field sea-level change as a diagnostic constraint on GIA inputs. We demonstrate that the similarity in the sea-level rise across the narrow mwp-1A time window at Barbados and Sunda Shelf rules out southern Laurentia as the sole source for the mwp-1A event. A series of other scenarios, including a substantial contribution from the Antarctic ice complex, are consistent with this comparison. A stronger constraint is provided by sea-level histories across the broader Lateglacial time window. In this case, we show that a GIA model characterized by both a high-viscosity lower mantle and a substantial contribution from Antarctica to mwp-1A resolves the previously noted far-field discrepancies. The exercise supports the veracity of the sea-level observations but not the existence of the mwp-1B event. Our results strengthen arguments that an early and rapid Antarctic deglaciation triggered a sequence of climatic events that ended the most recent glacial period of the current ice age.
DE: 0726 Ice sheets
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1641 Sea level change (1222, 1225, 4556)
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Cryosphere [C]
MN: Fall Meeting 2005