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6. Seafloor geomorphology of the Wrigley Gulf shelf, Amundsen Sea, West Antarctica, reveals two different phases of glaciation

Author

Lee, Jae Il, Hillenbrand, Claus-Dieter, Wellner, Julia S., Kim, Hyoung Jun, Rhee, Hyun Hee, Yoo, Kyu-Cheul, Kim, Sunghan, Lee, Min Kyung, Lee, Jae Il, Hillenbrand, Claus-Dieter, Wellner, Julia S., Kim, Hyoung Jun, Rhee, Hyun Hee, Yoo, Kyu-Cheul, Kim, Sunghan, and Lee, Min Kyung

Abstract

Knowledge of the behaviour of marine-based ice sheets during times of climatic warming, such as the last deglaciation, provides important information to understand how ice sheets respond to external forcing. We analysed swath bathymetric and acoustic sub-bottom profiler data from Wrigley Gulf on the western Amundsen Sea shelf, West Antarctica, to identify glacial features and reconstruct past changes in the extent of the West Antarctic Ice Sheet (WAIS) and ice flow directions. Glacial bedforms mapped within a bathymetric cross-shelf trough include features showing cross-cutting and overprinting relationship and indicate changes in ice-flow orientation. Here, we distinguish at least two phases of different ice-flow patterns on the Wrigley Gulf shelf. During the earlier phase, seaward ice stream flow on the inner shelf was deflected towards the east due to the existence of an ice dome on the middle-outer continental shelf. Retreat of grounded ice towards the centre of this dome is indicated by the asymmetric cross profile of recessional moraines mapped on the middle shelf. The later glaciation phase was characterized by fast, NNW-directed ice flow across the shelf along a broad front and subsequent stepwise landward retreat, which is evident from the common occurrence and orientation of mega-scale glaciation lineations and grounding zone wedges on the middle-inner shelf. It is uncertain whether the two phases of glaciation recorded on the seafloor occurred during the last and penultimate glacial periods or at different times of the last glaciation. Reliable chronological constraints from sediment cores and additional geomorphological information are needed to understand the cause of the changes in WAIS dynamics reflected by the two ice-flow phases.

Published
2024

7. Drastic changes in Depositional Environments at the Ross Sea Continental Margin since the Mid-Pleistocene: More evidence for West Antarctic Ice Sheet collapse.

Author

Dash, Chinmay, Seong, Yeong Bae, Singh, Ajay Kumar, Lee, Min Kyung, Lee, Jae Il, Yoo, Kyu-Cheul, Rhee, Hyun Hee, and Yu, Byung Yong

Abstract

This study investigates a sediment core (RS15-LC47) from the Ross Sea continental rise to elucidate the sea-ice interaction and resulting paleodepositional changes over the past 800 ka. By integrating whole-core Magnetic Susceptibility (MS), sediment biogenic components (TOC, CaCO3, and biogenic silica), sedimentological features, and the isotopic ratio of authigenic beryllium (10Be/9Be)reac, we unravel the paleoenvironmental changes and their influence on the sedimentary processes. The lower segment of the investigated interval (750–550 ka) exhibits distinct lithological characteristics, including parallel and cross laminations, along with millimeter-scale faults, suggestive of contourite depositional processes. This section also displays irregular trends in MS values due to poorly sorted sediments, characteristics feature of sediment slumping. The lowest (10Be/9Be)reac ratio in this interval suggests reduced Circumpolar Deep Water (CDW) inflow due to strengthened Antarctic Slope Current (ASC). Although the Total Organic Carbon (TOC) is highest in this interval, high Carbon-to-Nitrogen (C/N) ratio and low Barium excess (Baex) suggests reduced marine productivity due to increased terrestrial input likely from advancing ice sheets. Following the Mid-Pleistocene Transition (MPT), MS values remain consistently low until MIS 8 (~250 ka) and (10Be/9Be)reac relatively increases, indicating persistent lukewarm condition. We hypothesize this timeframe favorable for ice-shelf disintegration and possible collapse of the West Antarctic Ice Sheet (WAIS). Between 550 and 250 ka, TOC/TN levels resemble those observed in the euphotic layer of the Ross Sea, with relatively higher Baex and TOC, indicating higher productivity during an extended lukewarm condition. During the late Pleistocene (> 250 ka), coarser grain size and IRD-rich layers suggest strengthening of bottom currents. The upwelling of CDW facilitated a drastic increase in the (10Be/9Be)reac ratio during the late Pleistocene. OpalMAR and TOC % exhibit positive trends with (10Be/9Be)reac during the late Pleistocene interglacials, suggesting increased productivity during warmer periods. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Asynchronous glacial dynamics of Last Glacial Maximum mountain glaciers in the Ikh Bogd Massif, Gobi Altai mountain range, southwestern Mongolia: aspect control on glacier mass balance

Author

Khandsuren, Purevmaa, Seong, Yeong Bae, Rhee, Hyun Hee, Lee, Cho-Hee, Sarikaya, Mehmet Akif, Oh, Jeong-Sik, Sandag, Khadbaatar, and Yu, Byung Yong

Abstract

Mountain glacier mass balance is affected by factors other than climate, such as topography, slope, and aspect. In midlatitude high-mountain regions, the north–south aspect contrast can cause significant changes in insolation and melt, resulting in local asynchrony in glacial dynamics. This study documents the asynchronous response of two paleoglaciers in southwestern Mongolia to the local topoclimatic factors using 10Be exposure age dating and 2D ice surface modeling. 10Be surface exposure age dating revealed that the Ikh Artsan south-facing valley glacier culminated (MIA1) at 20.1 ± 0.7 ka, coinciding with the global Last Glacial Maximum (gLGM). In contrast, the north-facing Jargalant paleoglacier (MJ1) culminated at 17.2 ± 1.5 ka, around Heinrich Stadial 1 and during the post-gLGM Northern Hemisphere warming. Our temperature-index melt model predicts that ablation will be substantially lower on the north-facing slope, as it is exposed to less solar radiation and cooler temperatures than the south-facing slope. The 2D ice surface modeling also revealed that the south-facing Ikh Artsan Glacier abruptly retreated from its maximum extent at 20 ka, but the Jargalant Glacier on the shaded slope consistently advanced and thickened due to reduced melt until 17 ka. The timing of the modeled glacier culmination is consistent within ± 1σ of the 10Be exposure age results. Extremely old ages ranging from 636.2 to 35.9 ka were measured for the inner moraines in the Jargalant cirque (MJ2–MJ4), suggesting a problem with inheritance from boulders eroded from the summit plateau.

Published
2023

15. Mid-Holocene thinning of David Glacier, Antarctica: Chronology and Controls

Author

Stutz, Jamey, primary, Mackintosh, Andrew, additional, Norton, Kevin, additional, Whitmore, Ross, additional, Baroni, Carlo, additional, Jamieson, Stewart S. R., additional, Jones, R. Selwyn, additional, Balco, Greg, additional, Salvatore, Maria Cristina, additional, Casale, Stefano, additional, Lee, Jae Il, additional, Seong, Yeong Bae, additional, Rhee, Hyun Hee, additional, McKay, Robert, additional, Vargo, Lauren J., additional, Lowry, Daniel, additional, Spector, Perry, additional, Cristl, Marcus, additional, Ivy Ochs, Susan, additional, Di Nicola, Luigia, additional, Iarossi, Maria, additional, Stuart, Finlay, additional, and Woodruff, Tom, additional

Published
2020
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