The North American Late Wisconsin ice sheet and mantle viscosity from glacial rebound analyses

摘要: Abstract Observations of sea level and crustal response to glacial loading cycles provide constraints on the mantle rheology function, E, as well ice load, I, with latter being largely free from a-priori glaciological or climate assumptions appropriate, therefore, for testing any such hypotheses. This paper presents new results both continental-mantle E I Late Wisconsin sheet, using geological evidence relative sea-level change (rsl) tilting palaeo-lake shorelines, complemented loose observations present-day radial displacement across North America. The focus is near within former maximum margins resulting earth representative sub-continental conditions. inversion information has limited resolution simple three-layer models, characterized by depth-averaged effective lithospheric thickness (H) upper- lower-mantle viscosities (ηum ηum respectively) adequately describe yielding parameters (earth model E-6) H = 102 (85–120) km, ηum = 5.1 × 1020 (3.5–7.5)x1020, ηlm = 1.3 × 1022 (0.8–2.8)x1022 where numbers in parenthesis are 95% confidence limits. details one exception, not strongly dependent rheological this range. exception lower viscosity that remains correlated magnitude scaling sheet: a link broken introducing effects Earth's rotation dynamic flattening. difference between continental comparable estimate (1–2.5)x1020 ocean statistically significant. Shoreline gradient Glacial Lakes McConnell, Agassiz, Algonquin Ojibway strong interior sheet (LW-6) multiple domes at least ∼17–18 ka onwards. earlier periods constrained global volume considerations. two principal over southern Nunavut (the Keewatin Dome) Quebec-Labrador, ≥3500 m thickness, separated an ridge some 1500 m than domes, requirement imposed information. Over western Canada gradients east Cordilleras partly shoreline data Lake McConnell (as lateglacial dome) indicate ice-free corridor Laurentian Cordilleran components unlikely have existed before ∼13ka. Reconstructions lakes consistent locations timing observational four major lake systems likely drainage routes identified. evolution LW-6 ice-volume expressed equivalent level, rapid decrease ∼15 14.5 ka, corresponding Bolling-Allerod period, main retreat along margin, further contributions through St Lawrence River valley northern straits gulfs, but Hudson Strait rsl point late removal (after 10 ka). contribution rise small,