Constraints on the Late Saalian to early Middle Weichselian ice sheet of Eurasia from field data and rebound modelling

Abstract

Using glacial rebound models we have inverted observations of crustal rebound and shoreline locations to estimate the ice thickness for the major glaciations over northern Eurasia and to predict the palaeo‐topography from late MIS‐6 (the Late Saalian at c. 140 kyr BP) to MIS‐4e (early Middle Weichselian at c. 64 kyr BP). During the Late Saalian, the ice extended across northern Europe and Russia with a broad dome centred from the Kara Sea to Karelia that reached a maximum thickness of c. 4500 m and ice surface elevation of c. 3500 m above sea level. A secondary dome occurred over Finland with ice thickness and surface elevation of 4000 m and 3000 m, respectively. When ice retreat commenced, and before the onset of the warm phase of the early Eemian, extensive marine flooding occurred from the Atlantic to the Urals and, once the ice retreated from the Urals, to the Taymyr Peninsula. The Baltic‐White Sea connection is predicted to have closed at about 129 kyr BP, although large areas of arctic Russia remained submerged until the end of the Eemian. During the stadials (MIS‐5d, 5b, 4) the maximum ice was centred over the Kara‐Barents Seas with a thickness not exceeding c. 1200 m. Ice‐dammed lakes and the elevations of sills are predicted for the major glacial phases and used to test the ice models. Large lakes are predicted for west Siberia at the end of the Saalian and during MIS‐5d, 5b and 4, with the lake levels, margin locations and outlets depending inter alia on ice thickness and isostatic adjustment. During the Saalian and MIS‐5d, 5b these lakes overflowed through the Turgay pass into the Aral Sea, but during MIS‐4 the overflow is predicted to have occurred north of the Urals. West of the Urals the palaeo‐lake predictions are strongly controlled by whether the Kara Ice Sheet dammed the White Sea. If it did, then the lake levels are controlled by the topography of the Dvina basin with overflow directed into the Kama‐Volga river system. Comparisons of predicted with observed MIS‐5b lake levels of Komi Lake favour models in which the White Sea was in contact with the Barents Sea.

Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions

“…This requires validation by more complete assessments because it has ramifications for studies of potential ice-reduction processes that are being used to evaluate sea-level risk in our warming future. Lambeck et al (2006Lambeck et al ( , 2010Lambeck et al ( , 2017. Our study uses two databases, one on the coral sea-level markers (published in 2016), and the other on glaciomorphological evidence (this study).…”

“…A strong case exists for a small PGM NAIS, from a combination of climate and ice-sheet modelling (Colleoni et al, 2014Wekerle et al, 2016), GIA modelling (Potter and Lambeck, 2003;Lambeck et al, 2006Lambeck et al, , 2010Lambeck et al, , 2017Wainer et al, 2017), and North Atlantic IRD observations (Obrochta et al, 2014), in addition to our sea-level assessment (this study).…”

“…Assuming a PGM sea-level drop of 109 ± 14 m, a PGM EIS volume of 33e53 m SLE , and comparable Antarctic excess ice volume between the PGM and LGM (assuming~17 m SLE as an upper bound, based on geologically constrained glaciological modelling; Table 1), the inferred values imply a North American NAIS volume as small as 59 to 39 m SLE (±14 m SLE ), respectively. A caveat applies with respect to attribution of component contributions to the overall sea-level drop, namely that various indicators for the maximum EIS extent may represent different glacial advance phases at different locations Lambeck et al, 2006;Hughes et al, 2013;Colleoni et al, 2016) (Fig. 1).…”

“…1 help to constrain the maximum PGM ice-sheet area, but are not indicative of ice-sheet thickness (i.e., topography, volume). Instead, model inversion techniques with varying assumptions and input datasets (e.g., Peltier, 2004;Lambeck et al, 2006;Abe-Ouchi et al, 2015) are needed to provide dynamic ice histories with volume, extent, and topographic constraints (see Stokes et al, 2015 for an overview on modelling past ice sheets). Ice-sheet extent, form, and thickness result from interactions between glaciological and climatological factors on local, regional, and global scales.…”

North Sea palaeogeographical reconstructions for the last 1 Ma

“…Owing to the visco-elastic nature of GIA, part of the adjustment is direct, part is stepped-delayed (e.g. Peltier, 2004;Lambeck et al, 2006;Steffen & Wu, 2011). During each glaciation, the crust below the ice sheet is depressed by the weight of ice up to 3 km thick (Fig.…”