Ice Streams of the Laurentide Ice Sheet

Winsborrow, Monica; Clark, Chris D.; Stokes, Chris R.

doi:10.7202/013142ar

Cited by 70 publications

(36 citation statements)

References 51 publications

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“…Such a configuration does not appear to contradict the relatively sparse proxy data available in this region (28), and is glaciologically consistent. Furthermore, the existence of a persistent ice stream through the Hudson Strait, as simulated here, is supported by geological evidence and modeling (29,30).…”

Section: Significancesupporting

confidence: 48%

Iceberg discharges of the last glacial period driven by oceanic circulation changes

Álvarez-Solas

Robinson

Montoya

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Proxy data reveal the existence of episodes of increased deposition of ice-rafted detritus in the North Atlantic Ocean during the last glacial period interpreted as massive iceberg discharges from the Laurentide Ice Sheet. Although these have long been attributed to self-sustained ice sheet oscillations, growing evidence of the crucial role that the ocean plays both for past and future behavior of the cryosphere suggests a climatic control of these ice surges. Here, we present simulations of the last glacial period carried out with a hybrid ice sheet-ice shelf model forced by an oceanic warming index derived from proxy data that accounts for the impact of past ocean circulation changes on ocean temperatures. The model generates a time series of iceberg discharge that closely agrees with ice-rafted debris records over the past 80 ka, indicating that oceanic circulation variations were responsible for the enigmatic ice purges of the last ice age.glacial climate variability | climate modeling | abrupt changes C ompared with the present interglacial period, the last glacial period (LGP) (∼110-10 ka before the present), and almost certainly previous ones (1), were characterized by substantial climatic variability on millennial timescales. This variability is mainly manifested in two types of events. Dansgaard-Oeschger (D/O) events are most notable in Greenland ice core records and involve decadal-scale warming of more than 10 K (interstadials) followed by slow cooling lasting several centuries and a final more rapid fall to cold background (stadial) conditions (2). Heinrich (H) events consist of massive iceberg discharges from the Laurentide Ice Sheet at intervals of ∼7 ka during peak glacial conditions throughout the LGP (3). Both D/O and H events are associated with widespread centennial-to millennial-scale climatic changes, including a synchronous temperature response over the North Atlantic and an antiphase temperature relationship over Antarctica and most of the Southern Ocean, as revealed by a wealth of deep-sea sediments, ice core, and terrestrial records (4). The Atlantic meridional overturning circulation (AMOC) is thought to play a central role in these abrupt glacial climatic changes. Although the paleoceanographic evidence on this link is scarce and mostly restricted to a few highresolution deep-sea sediment records of the last deglaciation (5, 6), both modeling studies and reconstructions provide strong support for the hypothesis that D/O events were caused by reorganizations of the AMOC (7,8). H events, identified as enhanced ice-rafted detritus (IRD) in North Atlantic deep-sea sediments (3, 9), occur during climatic minima of the Northern Hemisphere. They have classically been attributed to internal oscillations of the Laurentide (10) and assumed to lead to important disruptions of the Atlantic Ocean circulation (11). However, paleoclimate data have revealed that most H events likely occurred about a thousand years after North Atlantic Deep Water (NADW) formation had already slowed down or largely coll...

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Section: Significancesupporting

confidence: 48%

Iceberg discharges of the last glacial period driven by oceanic circulation changes

Álvarez-Solas

Robinson

Montoya

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…We have here chosen to base our synthesis primarily on previous spatial reconstructions (Dredge and Thorleifson, 1987;Clague, 1989;Clark et al, 1993;Kleman et al, 1997Kleman et al, , 2010Lundqvist, 2004;Svendsen et al, 2004;Mangerud, 2004;Winsborrow et al, 2004;Lambeck et al, 2006) that cover this time interval. A full consideration of primary morphological and stratigraphic data is offered in several of the key source publications.…”

Section: Methodsmentioning

confidence: 99%

Pre-LGM Northern Hemisphere ice sheet topography

et al. 2013

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Abstract. We here reconstruct the paleotopography of Northern Hemisphere ice sheets during the glacial maxima of marine isotope stages (MIS) 5b and 4.We employ a combined approach, blending geologically based reconstruction and numerical modeling, to arrive at probable ice sheet extents and topographies for each of these two time slices. For a physically based 3-D calculation based on geologically derived 2-D constraints, we use the University of Maine Ice Sheet Model (UMISM) to calculate ice sheet thickness and topography. The approach and ice sheet modeling strategy is designed to provide robust data sets of sufficient resolution for atmospheric circulation experiments for these previously elusive time periods. Two tunable parameters, a temperature scaling function applied to a spliced Vostok-GRIP record, and spatial adjustment of the climatic pole position, were employed iteratively to achieve a good fit to geological constraints where such were available. The model credibly reproduces the first-order pattern of size and location of geologically indicated ice sheets during marine isotope stages (MIS) 5b (86.2 kyr model age) and 4 (64 kyr model age). From the interglacial state of two north-south obstacles to atmospheric circulation (Rocky Mountains and Greenland), by MIS 5b the emergence of combined Quebec-central Arctic and Scandinavian-Barents-Kara ice sheets had increased the number of such highland obstacles to four. The number of major ice sheets remained constant through MIS 4, but the merging of the Cordilleran and the proto-Laurentide Ice Sheet produced a single continent-wide North American ice sheet at the LGM.

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“…Moreover, the development of geomorphological criteria to identify palaeo-ice streams (Kleman & Borgström, 1996;Stokes & Clark, 1999) has led to a major growth in the number of hypothesised ice streams (De Angelis & Kleman, 2005Ross, Campbell, Parent, & Adams, 2009;Ross, Lajeunesse, & Kosar, 2011;Shaw et al, 2006;Stokes, Clark, & Storrar, 2009). Winsborrow et al (2004) also provided an inventory and supporting evidence for each of the hypothesised ice streams within the LIS. More recently, new remote sensing products and digital elevation models have permitted the glacial landform mapping at a regional and ice sheet scale (Atkinson, Utting, & Pawley, 2014;Brown, Stokes, & O'Cofaigh, 2011;De Angelis, 2007a;Shaw, Sharpe, & Harris, 2010;Storrar & Stokes, 2007;Trommelen & Ross, 2010), augmenting the Glacial Map of Canada (Prest, Grant, & Rampton, 1968).…”

Section: A Brief Review Of Previous Workmentioning

confidence: 99%

“…Sharpe, 1988;). The largest ice sheet to grow and disappear was the North American Laurentide Ice Sheet (LIS; Figure 1) for which numerous palaeo-ice streams have been hypothesised (see reviews in Patterson, 1998;Winsborrow, Clark, & Stokes, 2004). Here, we present a new and updated map of palaeo-ice streams in the LIS (including the Innuitian Ice Sheet), building on earlier syntheses (Patterson, 1998;Winsborrow et al, 2004) and updated to include more recent publications and new mapping at the ice sheet scale.…”

Section: Introductionmentioning

confidence: 99%

Ice streams in the Laurentide Ice Sheet: a new mapping inventory

et al. 2014

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Rapidly flowing ice streams dominate the drainage of continental ice sheets and are a key component of their mass balance. Due to their potential impact on sea level, their activity in the Antarctic and Greenland Ice Sheets has undergone detailed scrutiny in recent decades. However, these observations only cover a fraction of their 'life-span' and the subglacial processes that facilitate their rapid flow are very difficult to observe. To circumvent these problems, numerous workers have highlighted the potential of investigating palaeo-ice streams tracks, preserved in the landform and sedimentary record of former ice sheets. As such, it is becoming increasingly important to know where and when palaeo-ice streams operated. In this paper, we present a new map of ice streams in the North American Laurentide Ice Sheet (LIS; including the Innuitian Ice Sheet), which was the largest of the ephemeral Pleistocene ice sheets and where numerous ice streams have been identified. We compile previously published evidence of ice stream activity and complement it with new mapping to generate the most complete and consistent mapping inventory to date. The map depicts close to three times as many ice streams (117 in total) compared to previous inventories, and categorises them according to the evidence they left behind, with some locations more speculative than others. The map considerably refines our understanding of LIS dynamics, but there is a clear requirement for improved dating of ice stream activity.

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Ice Streams of the Laurentide Ice Sheet

Cited by 70 publications

References 51 publications

Iceberg discharges of the last glacial period driven by oceanic circulation changes

Iceberg discharges of the last glacial period driven by oceanic circulation changes

Pre-LGM Northern Hemisphere ice sheet topography

Ice streams in the Laurentide Ice Sheet: a new mapping inventory

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