| Title | Dynamics of the North American Ice Sheet Complex during its inception and build-up to the Last Glacial Maximum |
| |
| Author | Stokes, C R; Tarasov, L; Dyke, A S |
| Source | Quaternary Science Reviews vol. 50, 2012 p. 86-104, https://doi.org/10.1016/j.quascirev.2012.07.009  Open Access |
| Image |  |
| Year | 2012 |
| Alt Series | Earth Sciences Sector, Contribution Series 20120396 |
| Publisher | Elsevier BV |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | British Columbia; Alberta; Saskatchewan; Manitoba; Ontario; Quebec; New Brunswick; Nova Scotia; Prince Edward Island; Newfoundland and Labrador; Northwest Territories; Yukon; Nunavut; Canada |
| NTS | 1; 2; 3; 10; 11; 12; 13; 14; 15; 16; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 52; 53; 54; 55; 56; 57; 58; 59; 62; 63; 64; 65;
66; 67; 68; 69; 72; 73; 74; 75; 76; 77; 78; 79; 82; 83; 84; 85; 86; 87; 88; 89; 92; 93; 94; 95; 96; 97; 98; 99; 102; 103; 104; 105; 106; 107; 114O; 114P; 115; 116; 117; 120; 340; 560 |
| Lat/Long WENS | -141.0000 -50.0000 90.0000 41.7500 |
| Subjects | surficial geology/geomorphology; Nature and Environment; glacial history; deglaciation; ice sheets; models; modelling; Laurentide Deglaciation; Laurentide Ice Sheet; Cenozoic; Quaternary |
| Illustrations | location maps; plots; graphs |
| Program | Climate Change Geoscience |
| Released | 2012 09 01 |
| Abstract | The North American Ice Sheet Complex played a major role in global sea level fluctuations during the Late Quaternary but our knowledge of its dynamics is based mostly on its demise from the Last Glacial
Maximum (LGM), a period characterised by non-linear behaviour in the form of punctuated ice margin recession, episodic ice streaming and major shifts in the location of ice divides. In comparison, knowledge of the pre-LGM ice complex is poorly
constrained, largely because of the fragmentary nature of the evidence relating to ice sheet build-up. In this paper, we explore the inception and growth of ice (120 e20 ka) using a glacial systems model which has been calibrated against a large and
diverse set of data relating to the deglacial interval. We make use of calibration data prior to the LGM but its scarcity introduces greater uncertainty, which is partly alleviated by our large ensemble analysis. Results suggest that, following the
last interglaciation (Oxygen Isotope Stage: OIS 5e), the ice complex initiated over the north-eastern Canadian Arctic and in the Cordillera within a few thousand years. It then underwent rapid growth to an OIS 5 maximum at w110 ka (5d) and covered
w70% of the area occupied by the LGM ice cover (although only 30% by volume). An OIS 5 minimum is modelled at w80 ka (5a), before a second phase of rapid growth at the start of OIS 4, which culminated in a large ice complex at w65 ka (almost as large
as at the LGM). Subsequent deglaciation was rapid (maximum modelled sea level contribution of >16 cm per century) and resulted in an OIS 3 minimum between ca 55e60 ka. Thereafter, the ice complex grew towards its LGM configuration, interrupted by
several phases of successively less significant mass loss. Our results support and extend previous inferences based on geological evidence and reinforce the notion of a highly dynamic pre-LGM ice complex (e.g. with episodes of +-10 s m of eustatic
sea level equivalent in <5 ka). Consistent with previous modelling, the fraction of warm-based ice increases towards the LGM from <20 to >50%, but even the thin OIS 5 ice sheets exhibit fast flow features (several 1000 m a-1) in major topographic
troughs. Notwithstanding the severe limitations imposed by the use of the 'shallow-ice approximation', we note that most fast flow-features generated prior to the LGM correspond to the location of 'known' ice streams during deglaciation, i.e. in
major topographic troughs and over soft sediments at the southern and western margins. Moreover, the modelled flux of these 'ice streams' (sensu lato), appears to be non-linearly scaled to ice sheet volume, i.e. there is no evidence that decay phases
were associated with significantly increased ice stream activity. This hypothesis requires testing using a model with higher-order physics and future modelling would also benefit from additional pre-LGM constraints (e.g. dated ice free/margin
positions) to help reduce and quantify uncertainties. |
| GEOSCAN ID | 292221 |
|
|