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We perform Bayesian inference of the parameters of a time-dependent model of ice flow and calving at Helheim Glacier, East Greenland. We find that, while a time-independent calving parameterization can recover the mean observed terminus position, such a model is unable to recover sub-annual variability, even when forced with seasonally varying climate. To address this, we develop a simple stochastic model relating surface runoff rates and calving threshold. Again inferring model parameters from observations, we find that this parameterization is able to reproduce observations with respect to both mean position and characteristic temporal variability. This result demonstrates the importance of considering potential sub-annual controls on calving rates in numerical models, which may include variable undercutting rates or surface runoff-dependent surface crevasse propagation.

The utility of CRISPR in plants has remained limited by the dual difficulties of delivering the molecular machinery to target cells and the use of somatic cell techniques that require tissue culture-based de novo organogenesis. We developed 5-10 nm isodiametric polyplex nanoassemblies, comprising poly [2-(dimethylamino)ethylmethacrylate] PDMAEMA (PD) polycationic linear homopolymers and CRISPR/Cas9 ribonucleoproteins (RNPs), that enable endocytosis-driven RNP uptake into pollen grains. Pollen from wheat plants (genotype Gladius+Sr50), homozygous for monogenic Sr50-mediated resistance to stem rust (Puccinia graminis f. sp. tritici -Pgt), were incubated with RNP/PD nanoassemblies targeting the dominant, Sr50 rust resistance gene. The treated pollen grains were then used to fertilize Gladius+Sr50 florets and the resulting M1 plants were tested for loss of Sr50 function via rust resistance screens. The identification of fully susceptible M1 seedlings indicated that the Sr50 RNPs acted on both alleles, indicating they were transferred via the treated pollen to the zygote. The ability to readily deliver CRISPR RNPs to reproductive cells via biodegradable, polymeric nanocomplexes has significant implications for the efficiency of gene editing in plants.

The Greenland Ice Sheet (GIS) is losing mass at a high rate1. Given the short-term nature of the observational record, it is difficult to assess the historical importance of this mass-loss trend. Unlike records of greenhouse gas concentrations and global temperature, in which observations have been merged with palaeoclimate datasets, there are no comparably long records for rates of GIS mass change. Here we reveal unprecedented mass loss from the GIS this century, by placing contemporary and future rates of GIS mass loss within the context of the natural variability over the past 12,000 years. We force a high-resolution ice-sheet model with an ensemble of climate histories constrained by ice-core data2. Our simulation domain covers southwestern Greenland, the mass change of which is dominated by surface mass balance. The results agree favourably with an independent chronology of the history of the GIS margin3,4. The largest pre-industrial rates of mass loss (up to 6,000 billion tonnes per century) occurred in the early Holocene, and were similar to the contemporary (ad 2000–2018) rate of around 6,100 billion tonnes per century5. Simulations of future mass loss from southwestern GIS, based on Representative Concentration Pathway (RCP) scenarios corresponding to low (RCP2.6) and high (RCP8.5) greenhouse gas concentration trajectories6, predict mass loss of between 8,800 and 35,900 billion tonnes over the twenty-first century. These rates of GIS mass loss exceed the maximum rates over the past 12,000 years. Because rates of mass loss from the southwestern GIS scale linearly5 with the GIS as a whole, our results indicate, with high confidence, that the rate of mass loss from the GIS will exceed Holocene rates this century. Rates of ice-mass loss from southwestern Greenland this century will exceed the maximum rate over the past 12,000 years, and would not be the result of natural variation.

We investigate changing precipitation patterns in the Kangerlussuaq region of western central Greenland during the Holocene thermal maximum (HTM), using a new chronology of ice sheet terminus position through the Holocene and a novel inverse modeling approach based on the unscented transform (UT). The UT is applied to estimate changes in annual precipitation in order to reduce the misfit between modeled and observed terminus positions. We demonstrate the effectiveness of the UT for time-dependent data assimilation, highlighting its low computational cost and trivial parallel implementation. Our results indicate that Holocene warming coincided with elevated precipitation, without which modeled retreat in the Kangerlussuaq region is more rapid than suggested by observations. Less conclusive is whether high temperatures during the HTM were specifically associated with a transient increase in precipitation, as the results depend on the assumed temperature history. Our results highlight the important role that changing precipitation patterns had in controlling ice sheet extent during the Holocene.

Computer models of wildfires are an important tool for fire managers and scientists. However, fuel inputs to wildfire models can be difficult to represent with sufficient detail in a computationally efficient manner. Recent advances in fuel mapping with airborne and terrestrial laser scanning (LIDAR) techniques present new opportunities to capture variation in fuels within a tree canopy and on a landscape. In this paper, we develop a technique for building 3D representations of vegetation from point clouds created by Terrestrial Laser Scans (TLS). Our voxel based approach is capable of representing heterogeneous crown fuels as collections of fuel cells in modern 3D Computational Fluid Dynamics wildfire models such as FDS, QUIC-Fire, or FIRETEC. We evaluated the effectiveness of our technique at different fuel cell resolutions by using the DAKOTA optimization toolkit to compare simulated fire behavior in FDS with observed burn data collected during a series of experiments at the Missoula Fire Sciences Laboratory. The difference between simulated and observed fire behavior was quantified by taking the Root Mean Square Error between the observed and simulated mass curves over time. Our primary finding was that the point cloud derived fuel cells accurately describe observed fire behavior when evaluated over fuel moisture content and dry foliage mass. We also found that the global minimum RMSE persists across fuel cells at each resolution. However, the RMSE gradient increases with fuel cell size. This result implies that while both low and high resolution fuel cells are capable of accurately representing complex fuel distributions in 3D fire models, low resolution fuel cells are more sensitive to changes in fuel moisture content and dry foliage mass. The results of this paper offer fire managers and scientists responsible for simulating fire behavior guidelines for how best to translate LIDAR data to 3D fire models, and what fuel cell resolution can best capture accurate fire behavior. With these best practices in mind, fire managers will be able to generate improved fire behavior predictions for prescribed burns, forest thinning plans, and suppression activities.

The Greenland Ice Sheet (GIS) is losing mass at a high rate

The suspensor is a short-lived tissue critical for proper embryonic development in many higher plants. While the tissue was initially thought to simply suspend the embryo in the endosperm, it has been found through decades of research that it serves multiple important purposes. The suspensor has been found to be vital for proper embryo patterning and numerous studies have been undertaken into the complex transcriptional cross-talk between the suspensor and the embryo proper. Indeed, many suspensor mutants also display abnormalities in the embryo. The suspensor's role as a nutrient conduit has been shown using ultrastructural and histochemical techniques. Biochemical approaches have found that the suspensor is a centre of early embryonic hormone production in several species. The suspensor has also been frequently used as a model for programmed cell death as it shows signs of termination almost immediately upon developing. This review covers the essential functions of the suspensor throughout its short existence from multiple disciplines including structural, genetic and biochemical perspectives.

We investigate changing precipitation patterns in the Kangerlussuaq region of west central Greenland during the Holocene thermal maximum, using a new chronology of ice sheet terminus position through the Holocene and a novel inverse modeling approach based on the unscented transform (UT). The UT is applied to estimate changes in annual precipitation in order to reduce the misfit between modeled and observed terminus positions. We demonstrate the effectiveness of the UT for time-dependent data assimilation, highlighting its low computational cost and trivial parallel implementation. Our results indicate that Holocene warming coincided with elevated precipitation, without which modeled retreat in the Kangerlussuaq region is more rapid than suggested by observations. Less conclusive is if high temperatures during the HTM were specifically associated with a transient increase in precipitation, as the results depend on the assumed temperature history. The importance of precipitation in controlling ice sheet extent during the Holocene underscores the importance of Arctic sea ice loss and changing precipitation patterns on the future stability of the GrIS.

Subglacial hydrology plays a key role in many glaciological processes, including ice dynamics via the modulation of basal sliding. Owing to the lack of an overarching theory, however, a variety of model approximations exist to represent the subglacial drainage system. The Subglacial Hydrology Model Intercomparison Project (SHMIP) provides a set of synthetic experiments to compare existing and future models. We present the results from 13 participating models with a focus on effective pressure and discharge. For many applications (e.g. steady states and annual variations, low input scenarios) a simple model, such as an inefficient-system-only model, a flowline or lumped model, or a porous-layer model provides results comparable to those of more complex models. However, when studying short term (e.g. diurnal) variations of the water pressure, the use of a two-dimensional model incorporating physical representations of both efficient and inefficient drainage systems yields results that are significantly different from those of simpler models and should be preferentially applied. The results also emphasise the role of water storage in the response of water pressure to transient recharge. Finally, we find that the localisation of moulins has a limited impact except in regions of sparse moulin density.

Hogg and Bushell (1997) in their seminal piece Charter Dialogue, characterized the relationship between the courts and legislature as "conversation," one that contributes to a democratic dialogue. This was done in response to critics such as Mandel (1989) who criticized the judiciary for being activist and trying to exert supremacy over the legislature. Through an analysis of several Supreme Court of Canada (‘SCC’) cases, Hogg and Bushell (1997) were arguing that in cases where a law or its provisions were struck down for non-compliance with the Charter, the legislature would subsequently respond to the SCC with a follow-up piece of legislation that would pass constitutional muster and still serve its original purpose.What this paper attempts to do is apply Hogg and Bushell’s (1997) democratic dialogue theory to SCC cases involving warrantless electronic surveillance. As our lives become more dependent on technological innovations, so too does the state’s dependence on technology increase in order to conduct criminal investigations. The personal information that can be revealed through seemingly innocuous information such as electricity consumption records or thermal imaging can reveal intimate details about an individual’s life, and lead to criminal consequences which is particularly alarming for individuals’ privacy rights. Dialogue theory can offer valuable insight as to how privacy rights are being affected in relation to certain investigative technologies, and through an analysis of specific case law, I hope to demonstrate that democratic dialogue plays an active role in creating a balanced approach to warrantless electronic surveillance, and protecting individual’s privacy rights.