Regional-scale abrupt Mid-Holocene ice sheet thinning in the western Ross Sea, Antarctica

Geology ◽  
2020 ◽  
Author(s):  
R.S. Jones ◽  
R.J. Whitmore ◽  
A.N. Mackintosh ◽  
K.P. Norton ◽  
S.R. Eaves ◽  
...  
Keyword(s):  
Ross Sea ◽  
Numerical Models ◽  
Regional Scale ◽  
Ice Sheet ◽  
Outlet Glacier ◽  
Bed Topography ◽  
Geological Past ◽  
External Driver ◽  
Regional Sea Level ◽  
Western Ross Sea

Outlet glaciers drain the majority of ice flow in the Antarctic ice sheet. Theory and numerical models indicate that local bed topography can play a key role in modulating outlet glacier response to climate warming, potentially resulting in delayed, asynchronous, or enhanced retreat. However, the period of modern observations is too short to assess whether local or regional controls dominate ice sheet response on time scales that are critical for understanding ice sheet mass loss over this century and beyond. The recent geological past allows for insight into such centennial-scale ice sheet behavior. We present a cosmogenic surface-exposure chronology from Mawson Glacier, adjacent to a region of the Ross Sea that underwent dynamic marine-based ice sheet retreat following the Last Glacial Maximum. Our data record at least 220 m of abrupt ice thinning between 7.5 and 4.5 ka, followed by more gradual thinning until the last millennium. The timing, rates, and magnitudes of thinning at Mawson Glacier are remarkably similar to that documented 100 km to the south at Mackay Glacier. Together, both outlet glaciers demonstrate that abrupt deglaciation occurred across a broad region in the Mid-Holocene. This happened despite the complex bed topography of the western Ross Sea and implies an overarching external driver of retreat. When compared to regional sea-level and ocean-temperature changes, our data indicate that ocean warming most likely drove grounding-line retreat and ice drawdown, which then accelerated as a result of marine ice sheet instability.

scholarly journals Supplemental Material: Regional-scale abrupt Mid-Holocene ice sheet thinning in the western Ross Sea, Antarctica

2020 ◽  
Author(s):  
Richard S. Jones ◽  
et al.
Keyword(s):  
Ross Sea ◽  
Regional Scale ◽  
Ice Sheet ◽  
Sample Information ◽  
Western Ross Sea

Supplemental table of sample information and detailed description of methods.<br>

scholarly journals Past ice-sheet behaviour: retreat scenarios and changing controls in the Ross Sea, Antarctica

2016 ◽  
Vol 10 (3) ◽  
pp. 1003-1020 ◽  
Author(s):  
Anna Ruth W. Halberstadt ◽  
Lauren M. Simkins ◽  
Sarah L. Greenwood ◽  
John B. Anderson
Keyword(s):  
High Resolution ◽  
Continental Shelf ◽  
Drainage Basin ◽  
Ross Sea ◽  
Numerical Models ◽  
Ice Sheet ◽  
Small Scale ◽  
Antarctic Ice Sheet ◽  
Grounding Line ◽  
Western Ross Sea

Abstract. Studying the history of ice-sheet behaviour in the Ross Sea, Antarctica's largest drainage basin can improve our understanding of patterns and controls on marine-based ice-sheet dynamics and provide constraints for numerical ice-sheet models. Newly collected high-resolution multibeam bathymetry data, combined with two decades of legacy multibeam and seismic data, are used to map glacial landforms and reconstruct palaeo ice-sheet drainage. During the Last Glacial Maximum, grounded ice reached the continental shelf edge in the eastern but not western Ross Sea. Recessional geomorphic features in the western Ross Sea indicate virtually continuous back-stepping of the ice-sheet grounding line. In the eastern Ross Sea, well-preserved linear features and a lack of small-scale recessional landforms signify rapid lift-off of grounded ice from the bed. Physiography exerted a first-order control on regional ice behaviour, while sea floor geology played an important subsidiary role. Previously published deglacial scenarios for Ross Sea are based on low-spatial-resolution marine data or terrestrial observations; however, this study uses high-resolution basin-wide geomorphology to constrain grounding-line retreat on the continental shelf. Our analysis of retreat patterns suggests that (1) retreat from the western Ross Sea was complex due to strong physiographic controls on ice-sheet drainage; (2) retreat was asynchronous across the Ross Sea and between troughs; (3) the eastern Ross Sea largely deglaciated prior to the western Ross Sea following the formation of a large grounding-line embayment over Whales Deep; and (4) our glacial geomorphic reconstruction converges with recent numerical models that call for significant and complex East Antarctic ice sheet and West Antarctic ice sheet contributions to the ice flow in the Ross Sea.

scholarly journals Supplemental Material: Regional-scale abrupt Mid-Holocene ice sheet thinning in the western Ross Sea, Antarctica

2020 ◽  
Author(s):  
Richard S. Jones ◽  
et al.
Keyword(s):  
Ross Sea ◽  
Regional Scale ◽  
Ice Sheet ◽  
Sample Information ◽  
Western Ross Sea

Supplemental table of sample information and detailed description of methods.<br>

scholarly journals Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topography

2020 ◽  
Vol 61 (81) ◽  
pp. 46-57 ◽  
Author(s):  
Oliver T. Bartlett ◽  
Steven J. Palmer ◽  
Dustin M. Schroeder ◽  
Emma J. MacKie ◽  
Timothy T. Barrows ◽  
...  
Keyword(s):  
Measurement Errors ◽  
Survey Design ◽  
Ice Sheet ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Ice Dynamics ◽  
Outlet Glacier ◽  
Bed Topography ◽  
Novel Approach

AbstractAirborne radio-echo sounding (RES) surveys are widely used to measure ice-sheet bed topography. Measuring bed topography as accurately and widely as possible is of critical importance to modelling ice dynamics and hence to constraining better future ice response to climate change. Measurement accuracy of RES surveys is influenced both by the geometry of bed topography and the survey design. Here we develop a novel approach for simulating RES surveys over glaciated terrain, to quantify the sensitivity of derived bed elevation to topographic geometry. Furthermore, we investigate how measurement errors influence the quantification of glacial valley geometry. We find a negative bias across RES measurements, where off-nadir return measurement error is typically −1.8 ± 11.6 m. Topographic highlands are under-measured an order of magnitude more than lowlands. Consequently, valley depth and cross-sectional area are largely under-estimated. While overall estimates of ice thickness are likely too high, we find large glacier valley cross-sectional area to be under-estimated by −2.8 ± 18.1%. Therefore, estimates of ice flux through large outlet glaciers are likely too low when this effect is not taken into account. Additionally, bed mismeasurements potentially impact our appreciation of outlet-glacier stability.

The local Last Glacial Maximum in McMurdo Sound, Antarctica: Implications for ice-sheet behavior in the Ross Sea Embayment

2019 ◽  
Vol 132 (1-2) ◽  
pp. 31-47 ◽  
Author(s):  
Andrew J. Christ ◽  
Paul R. Bierman
Keyword(s):  
Last Glacial Maximum ◽  
Ross Sea ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Significant Advance ◽  
Ice Flow ◽  
Mcmurdo Sound ◽  
Last Glacial ◽  
Transantarctic Mountains ◽  
Western Ross Sea

AbstractDuring the Last Glacial Maximum (LGM), a grounded ice sheet filled the Ross Sea Embayment in Antarctica and deposited glacial sediments on volcanic islands and peninsulas in McMurdo Sound and coastal regions of the Transantarctic Mountains. The flow geometry and retreat history of this ice are debated, with contrasting views yielding divergent implications for the interaction between and stability of the East and West Antarctic ice sheets during late Quaternary time. Here, we present terrestrial geomorphologic evidence and reconstruct former ice-marginal environments, ice sheet elevations, and ice-flow directions in McMurdo Sound. Fossil algae in ice-marginal sediments provide a coherent radiocarbon chronology of maximum ice extent and deglaciation. We integrate these data with marine records to reconstruct grounded ice dynamics in McMurdo Sound and the western Ross Sea. The combined data set suggests ice flow toward the Transantarctic Mountains in McMurdo Sound during peak glaciation, with thick, grounded ice at or near its maximum position between 19.6 and 12.3 ka. Persistent grounded ice in McMurdo Sound and across the western Ross Sea after Meltwater Pulse 1a (14.0–14.5 ka) suggests that this sector of Antarctica did not significantly contribute to this rapid sea-level rise event. Our data show no significant advance of locally derived ice from the Transantarctic Mountains into McMurdo Sound during the local LGM.

scholarly journals Mid-Holocene thinning of David Glacier, Antarctica: Chronology and Controls

2020 ◽  
Author(s):  
Jamey Stutz ◽  
Andrew Mackintosh ◽  
Kevin Norton ◽  
Ross Whitmore ◽  
Carlo Baroni ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Flow Line ◽  
Ice Sheet ◽  
Outlet Glacier ◽  
Exposure Dating ◽  
Ice Surface ◽  
Geological Past ◽  
Climate Interactions ◽  
Glacier Flow ◽  
Exposure Ages

Abstract. Quantitative satellite observations provide a comprehensive assessment of ice sheet mass loss over the last four decades, but limited insights into long-term drivers of ice sheet change. Geological records can extend the observational record and aid our understanding of ice sheet–climate interactions. Here we present the first millennial-scale reconstruction of David Glacier, the largest East Antarctic outlet glacier in Victoria Land. We use surface exposure dating of glacial erratics deposited on nunataks to reconstruct changes in ice surface elevation through time. We then use numerical modelling experiments to determine the drivers of glacial thinning. Thinning profiles derived from 45 10Be and 3He surface exposure ages show that David Glacier experienced rapid thinning up to 2 m/yr during the mid-Holocene (~ 6,500 years ago). Thinning stabilised at 6 kyr, suggesting initial formation of the Drygalski Ice Tongue at this time. Our work, along with terrestrial cosmogenic nuclide records from adjacent glaciers, shows simultaneous glacier thinning in this sector of the Transantarctic Mountains occurred ~ 3 kyr after the retreat of marine-based grounded ice in the western Ross Embayment. The timing and rapidity of the reconstructed thinning at David Glacier is similar to reconstructions in the Amundsen and Weddell embayments. In order to identify the potential causes of these rapid changes along the David Glacier, we use a glacier flow line model designed for calving glaciers and compare modelled results against our geological data. We show that glacier thinning and marine-based grounding line retreat is initiated by interactions between enhanced sub-ice shelf melting and reduced lateral buttressing, leading to Marine Ice Sheet Instability. Such rapid glacier thinning events are not captured in continental or sector-scale numerical modelling reconstructions for this period. Together, our chronology and modelling suggest a ~ 2,000-year period of dynamic thinning in the recent geological past.

Delayed maximum and recession of an East Antarctic outlet glacier

Geology ◽  
2020 ◽  
Vol 48 (6) ◽  
pp. 630-634
Author(s):  
Courtney King ◽  
Brenda Hall ◽  
Trevor Hillebrand ◽  
John Stone
Keyword(s):  
Ross Sea ◽  
Ice Sheet ◽  
Outlet Glacier ◽  
Broad Agreement ◽  
Last Glaciation ◽  
Radiocarbon Data ◽  
Global Sea Level ◽  
The Antarctic ◽  
Exposure Ages ◽  
Terrestrial Data

Abstract During the last glaciation, East Antarctic outlet glaciers contributed to a grounded ice sheet in the Ross Embayment. The timing of maximum ice extent, as well as of subsequent deglaciation of these outlets, has implications for the behavior of the Antarctic Ice Sheet (AIS) and its impact on global sea level. We present 45 radiocarbon ages of lacustrine cyanobacteria from the Lake Wellman region alongside Hatherton Glacier, which are the first terrestrial data to both record advance of an Antarctic glacier to its maximum position as well as document a high-resolution chronology of subsequent retreat. Seventeen new exposure ages are widely scattered, but the youngest four are in broad agreement with the radiocarbon data. Hatherton Glacier slowly thickened from 13,000 to 9500 yr B.P. and then thinned steadily until at least ca. 2800 yr B.P. Our work affords evidence of both a delayed maximum and recession of an East Antarctic outlet glacier compared to the global Last Glacial Maximum (LGM) and supports growing evidence of a time-transgressive local LGM within the Ross Sea sector of the ice sheet. Both observations are consistent with the idea that the timing of outlet glacier expansion and timing of recession are controlled by the balance between dynamic thinning from ocean forcing and increased accumulation due to atmospheric warming.

scholarly journals Mid-Holocene thinning of David Glacier, Antarctica: chronology and controls

2021 ◽  
Vol 15 (12) ◽  
pp. 5447-5471
Author(s):  
Jamey Stutz ◽  
Andrew Mackintosh ◽  
Kevin Norton ◽  
Ross Whitmore ◽  
Carlo Baroni ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Catchment Scale ◽  
Peak Period ◽  
Outlet Glacier ◽  
Geological Past ◽  
Victoria Land ◽  
Exposure Ages

Abstract. Quantitative satellite observations only provide an assessment of ice sheet mass loss over the last four decades. To assess long-term drivers of ice sheet change, geological records are needed. Here we present the first millennial-scale reconstruction of David Glacier, the largest East Antarctic outlet glacier in Victoria Land. To reconstruct changes in ice thickness, we use surface exposure ages of glacial erratics deposited on nunataks adjacent to fast-flowing sections of David Glacier. We then use numerical modelling experiments to determine the drivers of glacial thinning. Thinning profiles derived from 45 10Be and 3He surface exposure ages show David Glacier experienced rapid thinning of up to 2 m/yr during the mid-Holocene (∼ 6.5 ka). Thinning slowed at 6 ka, suggesting the initial formation of the Drygalski Ice Tongue at this time. Our work, along with ice thinning records from adjacent glaciers, shows simultaneous glacier thinning in this sector of the Transantarctic Mountains occurred 4–7 kyr after the peak period of ice thinning indicated in a suite of published ice sheet models. The timing and rapidity of the reconstructed thinning at David Glacier is similar to reconstructions in the Amundsen and Weddell embayments. To identify the drivers of glacier thinning along the David Glacier, we use a glacier flowline model designed for calving glaciers and compare modelled results against our geological data. We show that glacier thinning and marine-based grounding-line retreat are controlled by either enhanced sub-ice-shelf melting, reduced lateral buttressing or a combination of the two, leading to marine ice sheet instability. Such rapid glacier thinning events during the mid-Holocene are not fully captured in continental- or catchment-scale numerical modelling reconstructions. Together, our chronology and modelling identify and constrain the drivers of a ∼ 2000-year period of dynamic glacier thinning in the recent geological past.

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