Ongoing Research
Recovering a 3-meter-long Kasten core aboard the RV/IB Nathaniel B. Palmer. The sediments inside hold important clues in understanding recent retreat of Antarctica’s most unstable glacier.
This work was conducted under the Thwaites Offshore Research (THOR; NSF PLR 1738942) initiative of the International Thwaites Glacier Collaboration (ITGC).
RECONSTRUCTING PRE-SATELLITE ERA MELTWATER DISCHARGE HISTORY FOR THWAITES GLACIER
The impact of subglacial meltwater expulsion on grounding-line and ice-shelf stability has been explored conceptually (Jenkins, 2011), through satellite observations (Le Brocq et al., 2013), and from bathymetry on deglaciated continental shelves (e.g., Simkins et al., 2017). Observations and models indicate active transmission of meltwater beneath the contemporary Thwaites Glacier (TG) in West Antarctica; yet, sedimentary archives were needed to determine whether meltwater drainage may have contributed to the rapid retreat observed at TG in recent decades.
Combining sedimentological, geochemical, and statistical analyses of five marine sediment cores, we find evidence that subglacial drainage is the primary mechanism for sediment delivery offshore of TG today. Computed tomography scans of cores reveal distinct drainage styles offshore eastern and western TG and suggest greater magnitudes of sediment-laden meltwater have been delivered to the ocean in recent centuries compared to the past several thousand years. These sedimentary archives suggest it is likely that subglacial drainage enhanced submarine melt along the grounding zone and amplified ice-shelf melt driven by oceanic processes, and these feedbacks should be considered in future projections of TG ice-marginal behavior.
For some fun #scicomm, see this Twitter thread - or, dive straight into the full (open access!) article here.
Using rhizons to extract sediment pore water from discrete core depths during the NBP20-02 expedition to the Amundsen Sea (Mar. 2020; Photo credit: Asmara Lehrmann).
INVESTIGATING OXYGEN & HYDROGEN STABLE ISOTOPES IN SEDIMENT POREWATER AS PROXY FOR WATER SOURCE
In seeking to quantify the magnitude and frequency of meltwater discharge, we test the hypothesis that periods of higher meltwater input can be recorded in waters stored in pore spaces of grounding-line proximal sediments.
Fresh, subglacial meltwater carries a dramatically different isotopic signature than does the mean ocean water of the Amundsen Sea. Evaluating variations in sediment porewater isotopic composition with geomorphic and sedimentologic analyses may aid in identifying paleo-grounding-line locations, and potentially reveal periods of intensive meltwater discharge.
Additionally, the incursion of warm, circumpolar deep water (CDW) onto the continental shelf is a primary driver of grounding line retreat in the Amundsen Sea sector of West Antarctica (Rignot et al., 2013; Jacobs et al., 2011); spatial and temporal differences in porewater isotope signatures may reflect current and past pathways of CDW to the ice shelf base.
Describing sediment cores at the Oregon State University Marine Geology Repository. The visual description is the first step before discrete sampling is carried out (Oct. 2019; Photo credit: Rebecca Totten).
EXPLORING GRAIN MICROMORPHOLOGY AS AN INDICATOR OF SUBGLACIAL HYDROLOGIC PROCESSES
Marine sediment archives offer a unique window into the subglacial environment and record evolution of subglacial drainage networks on longer timescales than can be achieved through, for example, ice-penetrating radar. Despite its widespread use in other sedimentary environments (e.g., van Hateren et al., 2020; Vos et al., 2014; Oakey et al., 2005), grain shape and surface microtexture are underused in glaciogenic sediment studies, including those that characterize meltwater plume deposits.
In this project I conduct a regional comparison of the grain-shape and micromorphology signatures of meltwater plume deposits and their source material (glacial till) produced by different glaciers, with the goals of improving future facies work and connecting grain-scale properties to subglacial plumbing and conditions at the ice-bed interface. In addition, this work will provide new insight into outstanding questions about the grain-size production and sorting processes observed in meltwater plume deposits.
I presented on this work at the 2022 American Geophysical Union Fall Meeting in Chicago, IL in the oral session C42B: Linking Glaciological Observations to Paleo Archives from Subglacial to Marine Environments. Read the abstract here!
Past Research
Presenting my master’s thesis work at the SCAR-PAIS Meeting (2017). I am proud to say I have since greatly improved my poster design skills.
My master’s thesis evaluated evidence for nascent glaciation in the Weddell Sea sector of Antarctica across the Eocene-Oligocene Transition (EOT, ca. 34 million years ago) by applying sedimentological and geochemical methods to sediment drill cores. The results of this work showed a cool, dry climate in this sector as early as 34.3 Mya as evidenced by consistently low chemical index of alteration values and notable contribution of glacial rock flour. These findings are consistent with shelf sediments from the Prydz Bay and Wilkes Land margins demonstrating significant terrestrial cooling across East Antarctica in the late Eocene.
Under the advisement of Dr. Sandra Passchier, I was awarded a travel grant that allowed me to present my thesis work at the SCAR-PAIS Meeting in Trieste, Italy (2017). The College of Arts and Sciences at Montclair State University lauded my thesis with the Recognition of Excellence in Graduating Masters Graduate Research (2018).
This work was recently expanded on and published in Paleoceanography and Paleoclimatology. To get a fuller picture of how Antarctic glaciation across the EOT impacted paleoceanographic dynamics in the Weddell Sea, read the article here!