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Abstract. A system of subglacial lakes drained on Thwaites Glacier from 2012–2014. To improve coverage for subsequent drainage events, we extended theelevation and ice-velocity time series on Thwaites Glacier through austral winter 2019. These new observations document a second drainage cycle in2017/18 and identified two new lake systems located in the western tributaries of Thwaites and Haynes glaciers. In situ and satellite velocityobservations show temporary < 3 % speed fluctuations associated with lake drainages. In agreement with previous studies, these observationssuggest that active subglacial hydrology has little influence on thinning and retreat of Thwaites Glacier on decadal to centennial timescales. 

Abstract. The Reference Elevation Model of Antarctica (REMA) is thefirst continental-scale digital elevation model (DEM) at a resolution ofless than 10&thinsp;m. REMA is created from stereophotogrammetry with submeterresolution optical, commercial satellite imagery. The higher spatial andradiometric resolutions of this imagery enable high-quality surfaceextraction over the low-contrast ice sheet surface. The DEMs are registeredto satellite radar and laser altimetry and are mosaicked to provide acontinuous surface covering nearly 95&thinsp;% the entire continent. The mosaicincludes an error estimate and a time stamp, enabling change measurement.Typical elevation errors are less than 1&thinsp;m, as validated by thecomparison to airborne laser altimetry. REMA provides a powerful newresource for Antarctic science and provides a proof of concept forgenerating accurate high-resolution repeat topography at continentalscales.

 

Abstract. Ocean-induced basal melting is directly and indirectly responsible for much of the Amundsen Sea Embayment ice loss in recent decades, but the total magnitude and spatiotemporal evolution of this melt is poorly constrained. To address this problem, we generated a record of high-resolution Digital Elevation Models (DEMs) for Pine Island Glacier (PIG) using commercial sub-meter satellite stereo imagery and integrated additional 2002&ndash;2015 DEM/altimetry data. We implemented a Lagrangian elevation change (Dh/Dt) framework to estimate ice shelf basal melt rates at 32&ndash;256-m resolution. We describe this methodology and consider basal melt rates and elevation change over the PIG shelf and lower catchment from 2008&ndash;2015. We document the evolution of Eulerian elevation change (dh/dt) and upstream propagation of thinning signals following the end of rapid grounding line retreat around 2010. Mean full-shelf basal melt rates for the 2008&ndash;2015 period were ~82&ndash;93&thinsp;Gt/yr, with ~&thinsp;200&ndash;250&thinsp;m/yr basal melt rates within large channels near the grounding line, ~&thinsp;10&ndash;30&thinsp;m/yr over the main shelf, and ~&thinsp;0&ndash;10&thinsp;m/yr over the North and South shelves, with the notable exception of a small area with rates of ~&thinsp;50&ndash;100&thinsp;m/yr near the grounding line of a fast-flowing tributary on the South shelf. The observed basal melt rates show excellent agreement with, and provide context for, in situ basal melt rate observations. We also document the relative melt rates for km-scale basal channels and keels at different locations on the shelf and consider implications for ocean circulation and heat content. These methods and results offer new indirect observations of ice-ocean interaction and constraints on the processes driving sub-shelf melting beneath vulnerable ice shelves in West Antarctica.

 

In flowering plants, cell–cell communication plays a key role in reproductive success, as both pollination and fertilization require pathways that regulate interactions between many different cell types. Some of the most critical of these interactions are those between the pollen tube (PT) and the embryo sac, which ensure the delivery of sperm cells required for double fertilization. Synergid cells function to attract thePTthrough secretion of small peptides and inPTreception via membrane‐bound proteins associated with the endomembrane system and the cell surface. While many synergid‐expressed components regulatingPTattraction and reception have been identified, few tools exist to study the localization of membrane‐bound proteins and the components of the endomembrane system in this cell type. In this study, we describe the localization and distribution of seven fluorescent markers that labelled components of the secretory pathway in synergid cells ofArabidopsis thaliana. These markers were used in co‐localization experiments to investigate the subcellular distribution of the twoPTreception componentsLORELEI, aGPI‐anchored surface protein, andNORTIA, aMILDEW RESISTANCE LOCUSO protein, both found within the endomembrane system of the synergid cell. These secretory markers are useful tools for both reproductive and cell biologists, enabling the analysis of membrane‐associated trafficking within a haploid cell actively involved in polar transport.