The rapidly-changing Thwaites Ice Shelf is crucial for understanding ice-shelf instability and its implications for sea-level rise from Antarctica. Fractures play a significant role in this region but are poorly characterized, especially regarding their vertical depth. To address this gap, we developed a robust workflow that adapts to surface topography complexities to characterize time-varying fracture vertical properties over Thwaites using ICESat-2 altimetry measurements. We derived seasonal flow velocities from Sentinel-1 data and analyzed climate reanalysis data to examine flow-fracture interactions in the context of oceanic and atmospheric changes. The results revealed distinct fracturing and flow patterns between the eastern and western sectors of the ice shelf. Significant fracturing was observed along the shear margin and near the grounding line in the eastern sector, correlating with flow speed increases exceeding 90% at shear zones. In contrast, the western glacier tongue exhibited a less progressive fracturing pattern, with an active fracture zone downstream of the historical grounding line and overall flow deceleration. This is likely due to the stabilizing effects of grounding-zone geometry, a subglacial sill, and increased coupling to the slower-moving eastern sector. Atmospheric and oceanic reanalysis data suggest that atmosphere-sea-ice-ocean interactions could destabilize an ice shelf through shallow oceanic warming. Warm winters, reduced sea ice, and favorable winds and ocean currents can cause shoaling of warm Circumpolar Deep Water, facilitating access of warm waters to thin, structurally vulnerable areas such as shear margins and basal channels. This intensifies fracturing and triggers damage-flow-acceleration feedback that could lead to eventual ice-shelf destabilization.

Microplastics have become ubiquitous in all reaches of the world. Due to their small size, low density, and environmental persistence, they are transported throughout the Earth's system. Despite its importance, little is known about microplastic transport and deposition, especially by snow particles, and most people are not aware of the extent of the problem. The PlastiX-Snow Citizen Science Project aims to fill these research and informational gaps using crowd-sourcing to achieve scientific research outputs, educational programming, and active outreach and engagement. We will initially measure the spatial distribution of snow deposited microplastics throughout a region in New York State and expand nationally using community partners. As trained partners, the Snow Ambassadors will inform the local community about microplastics, recruit participants, and assist in leading trainings. As nodes of the project, they will expand the reach to a large demographic of people across the country, including both life-long learners and school groups. Citizen scientists will collect, examine, and report the snow-deposited microplastics in their own backyard. The PlastiX-Snow team also will collect snowmelt samples from participants to robustly analyze the microplastics at Lamont-Doherty Earth Observatory. According to a National Academy of Sciences, a primary concern regarding citizen science projects is the lack of engagement and feedback to the participants of the program's findings. We specifically address these challenges by actively and continually engaging our participants and partners through direct and virtual public programming, classroom visits, media, newsletters, and an interactive website. PlastiX-Snow goals are to 1. Collect data for a deeper understanding of microplastics disseminated by snow, 2. Teach the public about the dangers of microplastics and potential solutions, 3. Engage communities, students, educators, and the public to participate in groundbreaking, relevant scientific research. We aim to shed light on the severity of microplastic pollution, build a bridge between the public and the scientific community, connect citizen scientists to their natural environment through field work, and encourage them to serve as environmental stewards and leaders in their own communities.

Projections of the sea level contribution from the Greenland and Antarctic ice sheets rely on atmospheric and oceanic drivers obtained from climate models. The Earth System Models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6) generally project greater future warming compared with the previous CMIP5 effort. Here we use four CMIP6 models and a selection of CMIP5 models to force multiple ice sheet models as part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We find that the projected sea level contribution at 2100 from the ice sheet model ensemble under the CMIP6 scenarios falls within the CMIP5 range for the Antarctic ice sheet but is significantly increased for Greenland. Warmer atmosphere in CMIP6 models results in higher Greenland mass loss due to surface melt. For Antarctica, CMIP6 forcing is similar to CMIP5 and mass gain from increased snowfall counteracts increased loss due to ocean warming.

Rapid retreat of the Larsen A and B ice shelves has provided important clues about the ice shelf destabilization processes. The Larsen C Ice Shelf, the largest remaining ice shelf on the Antarctic Peninsula, may also be vulnerable to future collapse in a warming climate. Here, we utilize multi-source satellite images collected over 1963–2020 to derive multidecadal time series of ice front, flow velocities, and critical rift features over Larsen C, with the aim of understanding the controls on its retreat. We complement these observations with modeling experiments using the Ice-sheet and Sea-level System Model to examine how front geometry conditions and mechanical weakening due to rifts affect ice shelf dynamics. Over the past six decades, Larsen C lost over 20% of its area, dominated by rift-induced tabular iceberg calving. The Bawden Ice Rise and Gipps Ice Rise are critical areas for rift formation, through their impact on the longitudinal deviatoric stress field. Mechanical weakening around Gipps Ice Rise is found to be a primary control on localized flow acceleration, leading to the propagation of two rifts that caused a major calving event in 2017. Capturing the time-varying effects of rifts on ice rigidity in ice shelf models is essential for making realistic predictions of ice shelf flow dynamics and instability. In the context of the Larsen A and Larsen B collapses, we infer a chronology of destabilization processes for embayment-confined ice shelves, which provides a useful framework for understanding the historical and future destabilization of Antarctic ice shelves.