Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, north-west Greenland

Hogan, Kelly; Mayer, Larry A.; Reilly, Brendan; Jennings, Anne E.; Stoner, J. S.; Nielsen, Tove; Andresen, Katrine Juul; Nørmark, Egon; Heirman, Katrien; Kamla, Elina; Jerram, Kevin; Stranne, Christian; Mix, Alan C

doi:10.5194/tc-14-261-2020

Cited by 25 publications

(28 citation statements)

References 110 publications

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“…The Petermann ice tongue has historically covered most of the Petermann Fjord, extending about 80 km from the grounding zone, but large calving events in 2010 and 2012 reduced it to its current length (Münchow, Padman, and Fricker 2014), opening the fjord to research from icebreaker Oden. The seafloor of the area is bathymetrically complex, with several basins formed by underlying bedrock topography and molded by confluent ice streams during previous glaciations (Jakobsson et al 2018;Hogan et al 2020;Figure 1b).…”

Section: Environmental Settingmentioning

confidence: 99%

Modern foraminiferal assemblages in northern Nares Strait, Petermann Fjord, and beneath Petermann ice tongue, NW Greenland

Jennings

Andrews

Reilly

et al. 2020

Arctic, Antarctic, and Alpine Research

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Calving events of Petermann Glacier, northwest Greenland, in 2010 and 2012 reduced the length of its ice tongue by c. 25 km, allowing exploration of newly uncovered seafloor during the Petermann 2015 Expedition. This article presents the results of foraminiferal analysis and environmental data from thirteen surface sediment samples in northern Nares Strait and Petermann Fjord, including beneath the modern ice tongue. This is the first study of living foraminifera beneath an arctic ice tongue and the first modern foraminiferal data from this area. Modern assemblages were studied to constrain species environmental preferences and to improve paleoenvironmental interpretations of foraminiferal assemblages. Sub-ice tongue assemblages differed greatly from those at all other sites, with very low faunal abundances and being dominated by agglutinated fauna, likely reflecting low food supply under the ice tongue. Fjord fauna were comprised of 80 percent or more calcareous species. Notably, Elphidium clavatum is absent beneath the ice tongue although it is dominant in the fjord. Increasing primary productivity associated with the transition to mobile sea ice, diminishing influence of the Petermann Glacier meltwater with distance from the grounding line, and increased influence of south-flowing currents in Nares Strait are the important controls on the faunal assemblages.

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Section: Environmental Settingmentioning

confidence: 99%

Modern foraminiferal assemblages in northern Nares Strait, Petermann Fjord, and beneath Petermann ice tongue, NW Greenland

Jennings

Andrews

Reilly

et al. 2020

Arctic, Antarctic, and Alpine Research

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“…Because we targeted bedrock locations that exhibited evidence of subglacial abrasion (i.e., striations, polish), rather than quarrying (Figure 2), we consider our erosional depths to represent abrasion depths. While it is likely that samples in erosional Group 1 represent abrasion, no sample plots between Groups 1 and 2 on Figure 1, and the apparent abrasion rates (erosion depths corrected for the duration of historical cover) implied by the erosional depths of Groups 2 (1.63 ± 0.56 mm yr -1 ) and 3 (6.24 ± 0.56 mm yr -1 ) exceed most estimates of subglacial erosion (which include both abrasion and quarrying) in Greenland (Hogan et al, 2020 and references therein) and as well as many estimates from the midlatitudes and polar regions (Cook et al, 2020; Figure 5). Thus, we find it unlikely that the Group 2 and 3 10 Be concentrations were solely achieved by rock abrasion.…”

Section: Centennial-scale Erosionmentioning

confidence: 93%

“…In east Greenland, sediment flux data yield a canonical Greenland erosion rate of 0.01-0.04 mm yr -1 (Andrews et al, 1994), which Cowton et al (2012) revised to 0.3 mm yr -1 after accounting for sediment entrained in iceberg mélange after Syvitski et al (1996). Suspended sediment and solute data from the Watson proglacial river near Kangerlussuaq in central-west Greenland constrain average subglacial erosion to 0.5 mm yr -1 for the years 2006-2016 (Hasholt et al, 2018), although individual years were perhaps as high as 4.5 mm yr -1 (Hogan et al, 2020). Furthermore, suspended sediment load from an individual glacier within the Watson River catchment yielded a higher erosion rate of 4.8 ± 2.6 mm yr -1 from 2009-2010 (Cowton et al, 2012).…”

Section: Modeled Orbital-and Centennial-scale Erosion Ratesmentioning

confidence: 99%

Centennial- and orbital-scale erosion beneath the Greenland Ice Sheet

Balter-Kennedy¹,

Young²,

Briner³

et al. 2021

Preprint

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Erosion beneath glaciers and ice sheets is a fundamental Earth-surface process dictating landscape development, which in turn influences ice-flow dynamics and the climate sensitivity of ice masses. The rate at which subglacial erosion takes place, however, is notoriously difficult to observe because it occurs beneath modern glaciers in a largely inaccessible environment. Here, we present 1) cosmogenic-nuclide measurements from bedrock surfaces with well constrained exposure and burial histories fronting Jakobshavn Isbræ in western Greenland to constrain centennial-scale erosion rates, and 2) a new method combining cosmogenic nuclide measurements in a shallow bedrock core with cosmogenic-nuclide modelling to constrain orbital-scale erosion rates across the same landscape. Twenty-six 10Be measurements in surficial bedrock constrain the erosion rate during historical times to 0.4–0.8 mm yr-1. Seventeen 10Be measurements in a 4-m-long bedrock core corroborate this centennial-scale erosion rate, and reveal that 10Be concentrations below ~2 m depth are greater than what is predicted by an idealized production-rate depth profile. We utilize this excess 10Be at depth to constrain orbital-scale erosion rates at Jakobshavn Isbræ to 0.1–0.3 mm yr-1. The broad similarity between centennial- and orbital-scale erosion rates suggests that subglacial erosion rates have remained relatively uniform throughout the Pleistocene at Jakobshavn Isbræ.

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“…This basement surface could either be sedimentary bedrock, or highly lithified sedimentary units like till. Hogan et al (2020) illustrated that in Petermann Fjord, lower frequency air gun seismic data was required to differentiate bedrock from more lithified sediments and till. The unsplit sediment cores were allowed to equilibrate to room temperature (~20 o C) and logged shipboard on a Geotek multi-sensor core logger (MSCL).…”

Section: Marine Sediment Coresmentioning

confidence: 99%

The Holocene dynamics of Ryder Glacier and ice tongue in north Greenland

O’Regan¹,

Cronin²,

Reilly³

et al. 2021

Preprint

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Abstract. The northern sector of the Greenland ice sheet is considered to be particularly susceptible to ice mass loss arising from increased glacier discharge in the coming decades. However, the past extent and dynamics of outlet glaciers in this region, and hence their vulnerability to climate change, are poorly documented. In the summer of 2019, the Swedish icebreaker Oden entered the previously unchartered waters of Sherard Osborn Fjord, where Ryder Glacier drains approximately 2 % of Greenland's ice sheet into the Lincoln Sea. Here we reconstruct the Holocene dynamics of Ryder Glacier and its ice tongue by combining radiocarbon dating with sedimentary facies analyses along a 45 km transect of marine sediment cores collected between the modern ice tongue margin and the mouth of the fjord. The results illustrate that Ryder Glacier retreated from a grounded position at the fjord mouth during the Early Holocene (>10.7 ± 0.4 cal ka BP) and receded more than 120 km to the end of Sherard Osborn Fjord by the Middle Holocene (6.3 ± 0.3 cal ka BP), likely becoming completely land-based. A re-advance of Ryder Glacier occurred in the Late Holocene, becoming marine-based around 3.9 ± 0.4 cal ka BP. An ice tongue, similar in extent to its current position was established in the Late Holocene (between 3.6 ± 0.4 and 2.9 ± 0.4 cal ka BP) and extended to its maximum historical position near the fjord mouth around 0.9 ± 0.3 cal ka BP. Laminated, clast-poor sediments were deposited during the entire retreat and regrowth phases, suggesting the persistence of an ice tongue that only collapsed when the glacier retreated behind a prominent topographic high at the landward end of the fjord. Sherard Osborn Fjord narrows inland, is constrained by steep-sided cliffs, contains a number of bathymetric pinning points that also shield the modern ice tongue and grounding zone from warm Atlantic waters, and has a shallowing inland sub-ice topography. These features are conducive to glacier stability and can explain the persistence of Ryder’s ice tongue while the glacier remained marine-based. However, the physiography of the fjord did not halt the dramatic retreat of Ryder Glacier under the relatively mild changes in climate forcing during the Holocene. Presently, Ryder Glacier is grounded more than 40 km seaward of its inferred position during the Middle Holocene, highlighting the potential for substantial retreat in response to ongoing climate change.

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Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, north-west Greenland

Cited by 25 publications

References 110 publications

Modern foraminiferal assemblages in northern Nares Strait, Petermann Fjord, and beneath Petermann ice tongue, NW Greenland

Modern foraminiferal assemblages in northern Nares Strait, Petermann Fjord, and beneath Petermann ice tongue, NW Greenland

Centennial- and orbital-scale erosion beneath the Greenland Ice Sheet

The Holocene dynamics of Ryder Glacier and ice tongue in north Greenland

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