One million years of glaciation and denudation history in west Greenland

Abstract

The influence of major Quaternary climatic changes on growth and decay of the Greenland Ice Sheet, and associated erosional impact on the landscapes, is virtually unknown beyond the last deglaciation. Here we quantify exposure and denudation histories in west Greenland by applying a novel Markov-Chain Monte Carlo modelling approach to all available paired cosmogenic 10Be-26Al bedrock data from Greenland. We find that long-term denudation rates in west Greenland range from >50 m Myr−1 in low-lying areas to ∼2 m Myr−1 at high elevations, hereby quantifying systematic variations in denudation rate among different glacial landforms caused by variations in ice thickness across the landscape. We furthermore show that the present day ice-free areas only were ice covered ca. 45% of the past 1 million years, and even less at high-elevation sites, implying that the Greenland Ice Sheet for much of the time was of similar size or even smaller than today.

Evolution of the central West Greenland margin and the Nuussuaq Basin: Localised basin uplift along a stable continental margin proposed from thermochronological data

“…Bonow, Japsen, & Nielsen, ; Chalmers, ; Green, Japsen, Chalmers, Bonow, & Duddy, ; Lidmar‐Bergström, Ollier, & Sulebak, ; Riis, ; Rowberry, ); however, several recent studies have suggested other processes are the source of these features. Recent cosmogenic isotope studies from across West Greenland suggested the modern geomorphology is likely the result of glaciation, where warm‐based glaciers focus erosion along preglacial river valleys, forming deeply incised fjords and cold‐based glaciers limit erosion in highland areas, resulting in elevated low‐relief surfaces (Egholm et al., ; Strunk et al., ). These conclusions would imply the modern landscape of the SW margin is simply the result of glacial erosion of an elevated rift flank, balanced by the redistribution of sediments offshore.…”

“…The protracted nature of cooling suggests that little change has occurred within the erosion regime through the Mesozoic and Cenozoic and implies that uplift of the margin during rifting is the most likely source of the elevated topography. The modern geomorphology of the margin may likely be the result of the underlying Archaean/Proterozoic geology and glaciation in the region, the latter causing erosion at different rates dependent on elevation, effectively preserving much of the higher topography while differentially eroding the margin (Strunk et al, 2017; Figure 7). This interpretation is consistent with that of several continental margins in the North Atlantic realm (Hendriks & Andriessen, 2002;Johnson & Gallagher, 2000;McGregor, Nielsen, & Stephenson, 2014;McGregor, Nielsen, Stephenson, Petersen, & Macdonald, 2013;Nielsen et al, 2009;Pedersen, Nielsen, & Gallagher, 2012) and implies that the elevated topography of the southern margin is Mesozoic in age and not the result of Late Cenozoic tectonic uplift.…”

A large impact crater beneath Hiawatha Glacier in northwest Greenland

“…The crater's depth (320 ± 70 m) is muted compared to that predicted for a fresh, subaerial terrestrial crater of the same diameter (~800 m) (17,24), which could result from either fast erosion over a short period or slower erosion over a longer period. Reported fluvial and subglacial erosion rates span a range of~10 −5 to 10 −2 m year −1 (25)(26)(27)(28). An erosion rate at the upper end of that range implies a minimum period of~5 ka to erode the rim and central uplift and partially fill the crater floor to form the present morphology, assuming that ice has covered the crater for nearly all of its existence.…”

Physical Weathering Intensity Controls Bioavailable Primary Iron(II) Silicate Content in Major Global Dust Sources

“…Oven drying overnight up to at least 50°C has been shown not to impact Fe(II) silicate minerals in marine sediment cores (Shoenfelt et al, 2018). The sediment coming off of Greenland is physically weathered by the Greenland ice sheet (Strunk et al, 2017;Wimpenny et al, 2010) and is composed mostly of primary minerals including Fe(II) silicate minerals from the underlying Precambrian igneous and metamorphic bedrock (Petersen & Rasmussen, 1980).…”