Abstract
The last deglaciation of the Laurentide Ice Sheet (LIS) was associated with major reorganisations in the ocean-climate system and its retreat also represents a valuable analogue for understanding the rates and mechanisms of ice sheet collapse. This paper reviews the characteristics of the LIS at its Last Glacial Maximum (LGM) and its subsequent deglaciation, with particular emphasis on the pattern and timing of ice margin recession and the driving mechanisms of retreat. The LIS initiated over the eastern Canadian Arctic ~116-110 ka (MIS 5d), but its growth towards the LGM was highly non-linear and punctuated by several episodes of expansion (~65 ka: MIS 4) and retreat (~50-40 ka: MIS 3). It attained its maximum position around 26-25 ka (MIS 2) and existed for several thousand years as an extensive ice sheet with major domes over Keewatin, Foxe Basin and northern Quebec/Labrador. It extended to the edge of the continental shelf at its marine margins and likely stored a sea-level equivalent of around 50 m and with a maximum ice surface ~3,000 m above present sea-level. Retreat from its maximum was triggered by an increase in boreal summer insolation, but areal shrinkage was initially slow and the net surface mass balance was positive, indicating that ice streams likely played an important role in reducing the ice sheet volume, if not its extent, via calving at marine margins. Between ~16 and ~13 ka, the ice sheet margin retreated more rapidly, particularly in the south and west, whereas the north and east underwent only minimal recession. The overall rate of retreat decreased during the Younger Dryas (YD), when several localised readvances occurred. Following the YD, the ice sheet retreated two to five times faster than previously, and this was primarily driven by enhanced surface melting while ice streams reduced in effectiveness. Final deglaciation of the Keewatin and Foxe Domes, left a remnant Labrador Dome that disappeared ~6.7 ka.
Highlights
The North American Laurentide Ice Sheet (LIS) was the largest ice sheet to grow and decay during the last glacial cycle, dominating Late Pleistocene fluctuations in global sea-level (Lambeck et al, 2014) and delivering the largest contribution to earlyHolocene sea level rise (Tarasov et al, 2012; Peltier, 2004)
Building on several major syntheses over the last few decades (Denton and Hughes, 1981; Dyke and Prest, 1987; Fulton, 1989; Dyke, 2004), this paper aims to provide an up-to-date review of the LIS at the global Last Glacial Maximum (gLGM) with an emphasis on the pattern and timing of its deglaciation and the mechanisms that led to its demise
Late Wisconsinan maximum (~25-24 ka), the LIS was a large multi-domed ice sheet with a southern margin that extended south of 40° in the Great Lakes region, with a western margin that was fully coalescent with the Cordilleran Ice Sheet, and with northern and eastern margins that extended to the edge of the continental shelf (Fig. 4)
Summary
The North American Laurentide Ice Sheet (LIS) was the largest ice sheet to grow and decay during the last glacial cycle, dominating Late Pleistocene fluctuations in global sea-level (Lambeck et al, 2014) and delivering the largest contribution to early. Knowledge of its deglaciation is required to understand the rates, magnitude and mechanisms of ice sheet decay and associated impacts on sea level Building on several major syntheses over the last few decades (Denton and Hughes, 1981; Dyke and Prest, 1987; Fulton, 1989; Dyke, 2004), this paper aims to provide an up-to-date review of the LIS at the gLGM with an emphasis on the pattern and timing of its deglaciation and the mechanisms that led to its demise. Where the original source used only radiocarbon ages (e.g. Dyke and Prest, 1987), they have been converted to calendar years using a mixed marine and Northern Hemisphere atmosphere calibration curve (Stuiver et al, 2017) and the original radiocarbon dates appear in parentheses (14C ka)
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