Reorganization and readvance of East Antarctic ice during the Holocene

How do grounding line fluctuations affect upstream ice? This is a fundamental question which we have attempted to illuminate using observations of geomorphology on the seafloor of the western Ross Sea. Subglacial and ice-marginal landforms tell us that East Antarctic ice flowed through the Transantarctic Mountains into the Ross Embayment during the Last Glacial Maximum (LGM) to occupy Drygalski, JOIDES, and Pennell troughs. Following the LGM, retreating ice unzipped through JOIDES and Pennell troughs to form a large embayment in the grounding line. This triggered drawdown and enhanced flux through the southern Drygalski outlet glaciers that drove a major reorganization of flow in Drygalski Trough from northward- to southward-flowing and caused ice to readvance about 50 kilometers through southern JOIDES Trough, delivering a significant volume of ice back to the ocean. Click on the image of the manuscript header to read more!

The images below show the configuration of the ice sheet embayment in JOIDES and Pennell Troughs, followed by the configuration of ice after the readvance of outlet glaciers through southern Drygalski Trough into southern JOIDES Trough.

Update on AGU 2017

Last month I presented a poster at the AGU Fall Meeting that summarizes my work so far on reconstructing the post-LGM deglacial history of the Ross Sea (read abstract here). Click the image to the right to view a full-resolution jpg of the poster!

AGU prep is underway

It’s that time of year again! Everyone is scrambling to get their posters completed and printed before leaving for AGU, resorting to begging the library staff to stay open just a few minutes later. Even though we know AGU happens at the same time every year, and have plenty of time to prepare, there is inevitably a throng of anxious geoscientists vying for a spot on the printing waiting list the night before getting on the plane.

Nevertheless, I am excited to present my work on the deglacial history of the Ross Sea!

 

 

Here is the abstract:

Marine evidence of a deconvolving Antarctic Ice Sheet during post-LGM retreat of the Ross Sea sector

1Lindsay O. Prothro, 2Yusuke Yokoyama, 1Lauren M. Simkins, 1John B. Anderson, 3Wojciech Majewski, 2Masako Yamane, 4Naohiko Ohkouchi

1Department of Earth, Environmental and Planetary Science, Rice University; 2Atmosphere and Ocean Research Institute, University of Tokyo; 3Department of Environmental Paleobiology, Polish Academy of Sciences; 4Department of Biogeochemistry, Japan Agency for Marine-Earth Science and Technology

Predictive models of ice sheet and sea level change are dependent on observational data of ice-sheet behavior for model testing and tuning. The geologic record contains a wealth of information about ice-sheet dynamics, with fewer logistical, spatial, and temporal limitations than are involved in data acquisition along contemporary ice margins. However, past ice-sheet behavior is still largely uncertain or contested due to issues with obtaining meaningful radiocarbon dates. We minimize bias from glacially-reworked carbon and limitations from unknown geomorphic context and uncertainty in sediment facies identification by using careful sedimentary analyses within a geomorphic framework, as well as selection of appropriate dating methods. Our study area, the Ross Sea sector of Antarctica, is the primary drainage outlet for ~25% of the continent’s grounded ice. During the Last Glacial Maximum, the low-profile, marine-based West Antarctic Ice Sheet (WAIS) and the steeper profile, largely land-based East Antarctic Ice Sheet (EAIS) converged in the Ross Sea to flow out to or near the continental shelf edge. Geomorphic and sedimentary data reveal that during their subsequent retreat to form the Ross Sea Embayment, the two ice sheets behaved differently, with the WAIS rapidly retreating tens of kilometers followed by extended pauses, while the EAIS retreated steadily, with shorter (decadal- to century-long) pauses. This behavior leads us to believe that the two ice sheets may have contributed diachronously to sea level. By acquiring accurate timing of grounding line retreat, we are able to calculate volumes of ice lost throughout deglaciation, as well as associated sea level contributions. In addition, we attempt to rectify the contradicting marine and terrestrial interpretations of retreat patterns from the Ross Sea continental shelf.

Time and location: Session C21E, Tuesday, 12 December 2017 08:00 – 12:20; New Orleans Ernest N. Memorial Convention Center – Poster Hall D-F, Poster #0319