Ice-dammed lake and ice-margin evolution during the Holocene in the Kangerlussuaq area of west Greenland

Abstract

There is a lack of detailed information on the Holocene evolution of the west Greenland ice margin, not least because it was farther inland than at present and thus at present is covered by ice. Suggestions have been put forward, both of relatively quick ice-margin retreat and of relatively stable ice-margin positions. This study presents the first exploitation of sediments from an ice-dammed basin. Sediment that is rich in organic material records a period of time sufficient for vegetation to thrive; thus, without a lake and with a distal and diminished ice mass relative to the present. In contrast, sediment composed of suspension-settling deposits and with drop stones records an ice-dammed lake and a proximal calving ice-margin. Overall, we evidence relatively coarse-grained glacifluvial sedimentation predominantly from an ice-marginal delta and/ or a proglacial, braided river soon after the early Holocene deglaciation of this area. Subsequent mid-Holocene aeolian activity deposited leaves, some vegetation (roots) developed in the basin, and ponding of water formed organic-rich "gyttja" sediments and thin layers of peat. The lake then became ice marginal, and ice advances are interpreted to have occurred at approximately 4000 cal. yr BP, and between 2776 ± 26 cal. yr BP and 2440 ± 45 cal. yr BP. The Little Ice Age icemargin advance at Russell Glacier apparently reached its maximum extent after 147 ± 39 cal. yr BP, whereas at Isunnguata Sermia the maximum could have been as early as 245 ± 26 cal. yr BP. Given that ice-marginal lakes are becoming globally ubiquitous, improved resolution and new geological data on lake and ice-margin dynamics and interactions, such as ice-dammed lake-basin sediments, will be important for numerical models for assessing past and future ice-mass evolution.

Left High and Dry: Deglaciation of Dogger Bank, North Sea, Recorded in Proglacial Lake Evolution

“…The study highlights the unusual juxtaposition of a lakefill preserved perched on a topographic high (Figure 11). This phenomenon is recognized in hard-bedrock substrate settings in Greenland and Antarctica (Björck et al, 1996;Briner et al, 2010;Nedbalová et al, 2013;Carrivick et al, 2018), but not in soft sediment settings. Previous studies of proglacial lakes in the palaeo-record have identified lakes that are partially preserved in the stratigraphy in a present-day terrestrial setting, such as Glacial Lake Agassiz (Teller et al, 2002) or ice-marginal lakes of the Scandinavian Ice Sheet in northwest Russia (Lyså et al, 2011).…”

Maximum Southwest Greenland Ice Sheet Recession in the Early Holocene

“…In the Kangerlussuaq region, geophysical surveys reveal that sub‐icesheet permafrost, which can only form when an area is deglaciated, extends just ~2 km inland of the GrIS terminus near Issunguata Sermia (Ruskeeniemi et al, ). Ice‐dammed basin sediments near the Russell Glacier further constrain the timing of restricted ice extent to a relatively narrow window between ~6.8 and 4.2 ka (Carrivick et al, ). Thus, the collective evidence suggests that land‐based southwest GrIS margins experienced a major slowdown in retreat rates after ~7 ka.…”

Chemical weathering in a moraine at the ice sheet margin at Kangerlussuaq, western Greenland

“…The study area, and an unknown area now under the ice sheet, was thus covered by abundant vegetation during maybe as long as several thousand years (Van Tatenhove, van der Meer, and Koster 1996). The moraines at this site have been dated to the Little Ice Age; that is, approximately 1450 to 1850 A.D. (Forman et al 2007;Young and Briner 2015;Carrivick et al 2018;Levy et al 2018).…”