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Abstract. Iceberg influence on diatom productivity has been observed for the present and suggested for the past, but direct seeding of the Southern Ocean during times of ice sheet collapse has never been directly demonstrated. Here we demonstrate enhanced diatom production and accumulation in the Amundsen Sea during a Mid-Pliocene interglacial that precisely coincides with pulses of ice-rafted debris (IRD) accumulation, and we infer a causal relation. International Ocean Discovery Program (IODP) Expedition 379 obtained continuous sediment records from the Amundsen Sea continental rise to document West Antarctic Ice Sheet (WAIS) history in an area currently experiencing the largest ice loss in Antarctica. Scanning electron microscopy (SEM) imagery of Mid-Pliocene interglacial sediments of Marine Isotope Stage (MIS) (GI-17, ∼ 3.9 Ma) documents distinct intervals of IRD-rich diatomite, whereas the overall diatom abundance and concentration of bloom species is relatively low in the absence of visible IRD. Sand- and granule-sized IRD grains are documented fully encased within diatomite laminae, with some displaying soft-sediment micro-deformation formed by grains falling into soft diatom ooze. IRD-rich diatomite layers are often characterized by nearly monospecific assemblages of the pelagic diatom Thalassiothrix antarctica, indicating very high primary productivity as IRD grains fell. Diatom-filled fecal pellets with clusters of barite grains are also documented within some of these laminae, further indicating direct mass sinking of diatom mats. Melting icebergs release soluble nutrients along with IRD; thus the coincidence of IRD and bloom species in Amundsen Sea sediments provides compelling evidence that iceberg discharge and melting directly initiates enhanced diatom productivity in the Southern Ocean. These results may contribute to interpreting past WAIS history by providing another proxy for potential collapse events. Furthermore, we suggest that ice sheet collapse may more broadly enhance Southern Ocean diatom production, which in itself can contribute to increased carbon export, potentially attenuating or countering the warming that may have triggered the collapse. 

An enormous reserve of information about the subglacial bedrock, tectonic and topographic evolution of Marie Byrd Land (MBL) exists within glaciomarine sediments of the Amundsen Sea shelf, slope and deep sea, and MBL marine shelf. Investigators of the NSF ICI-Hot and NSF Linchpin projects partnered with Arizona Laserchron Center to provide course-based undergraduate research experiences (CUREs) for from groups who do not ordinarily find access points to Antarctic science. Our courses enlist BIPOC and gender-expansive undergraduates in studies of ice-rafted debris (IRD) and bedrock samples, in order to impart skills, train in the use of research instrumentation, help students to develop confidence in their scientific abilities, and collaboratively address WAIS research questions at an early academic stage. CUREs afford benefits to graduate researchers and postdoctoral scientists, also, who join in as instructional faculty: CUREs allow GRs and PDs to engage in teaching that closely ties to their active research, yet provides practical experience to strengthen the academic portfolio (Cascella & Jez, 2018). Team members also develop art-science initiatives that engage students and community members who may not ordinarily engage with science, forging connections that make science relatable. Re-casting science topics through art centers personal connections and humanizes science, to promote understanding that goes beyond the purely analytical. Academic research shows that diverse undergraduates gain markedly from the convergence of art and science, and from involvement in collaborative research conducted within a CURE cohort, rather than as an individualized experience (e.g. Shanahan et al. 2022). The CUREs are offered as regular courses for credit, making access equitable via course enrollment. The course designation carries a legitimacy that is sought by students who balance academics with part-time employment. Course information is disseminated via STEM Bridge programs and/or an academic advising hub that reaches students from groups that are insufficiently represented within STEM and cryosphere science. CURE investigation of Amundsen Sea and WAIS problems is worthy objective because: 1) A variety of sample preparation, geochemical methods, and scientific best-practices can be imparted, while educating students about Antarctica’s geological configuration and role in the Earth climate system. 2) Individual projects that are narrowly defined can readily scaffold into collaborative science at the time of data synthesis and interpretation. 3) There is a high likelihood of scientific discovery that contributes to grant objectives. 4) Enrolled students will experience ambiguity and instrumentation setbacks alongside their faculty and instructors, and will likely have an opportunity to withstand/overcome challenges in a manner that trains students in complex problem solving and imparts resilience (St John et al., 2019). Based on our experiences, we consider CUREs as a means to create more inclusive and equitable spaces for learning to do research, and a basis for a broadening future WAIS community. Our groups have yet to assess student learning gains and STEM entry in a robust way, but we can report that two presenters at WAIS 2022 came from our 2021 CURE, and four polar science graduate researchers gained experience via CURE teaching. Data obtained by CURE students is contributing to our NSF projects’ aims to obtain isotope, age, and petrogenetic criteria with bearing on the subglacial bedrock geology, tectonic and landscape evolution, and ice sheet history of MBL. Cited and recommended works: Cascella & Jez, 2018, doi: 10.1021/acs.jchemed.7b00705 Gentile et al., 2017, doi: 10.17226/24622 Shanahan et al. 2022, https://www.cur.org/assets/1/23/01-01_TOC_SPUR_Winter21.pdf Shortlidge & Brownell, 2016, doi: 10.1128/jmbe.v17i3.1103 St. John et al. 2019, EOS, doi: 10.1029/2019EO127285.