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Abstract. The Greenland Ice Sheet has become the largest single frozen source of global sea level rise following a pronounced increase in meltwater runoff in recent decades. The pivotal role of anomalous anticyclonic circulation patterns in facilitating this increase has been widely documented; however, this change in atmospheric circulation has coincided with a rapidly warming Arctic. While amplified warming at high latitudes has undoubtedly contributed to trends in Greenland's mass loss, the contribution of this shift in background conditions relative to changes in regional circulation patterns has yet to be quantified. Here, we apply the pseudo-global warming method of dynamical downscaling to estimate the contribution of the change in the thermodynamic background state under global warming to observed Greenland Ice Sheet surface mass loss since the turn of the century. Our analysis demonstrates that, had the recent atmospheric dynamical forcing of the Greenland Ice Sheet occurred under a preindustrial setting, anomalous surface mass loss would have been reduced by over 62 % relative to observations. We show that the change in the thermodynamic environment under amplified Arctic warming has augmented melt of the ice sheet via longwave radiative effects accompanying an increase in atmospheric water vapor content. Furthermore, the thermodynamic contribution to surface mass loss over the exceptional melt years of 2012 and 2019 was less than half that of the long-term average, demonstrating a reduced influence during periods of strong synoptic-scale atmospheric forcing. 

Abstract Fluorination of tris(2,6‐dimethoxyphenyl)‐methylium ((DMP)₃C⁺) was achieved through the partial defluorination of the methyl 2,3,5,6‐tetrafluorobenzoate via nucleophilic aromatic substitution. Using the fluorinated^2F((DMP)₃C⁺) as a precursor, fluorinated tetramethoxy‐ and dimethoxyquin‐ acridinium salts (^2F4and^2F5respectively) and trioxo‐, azadioxo‐, and diazaoxo‐ triangulenium salts (^2F6,^2F7and^2F8respectively) were synthesized successfully in good to moderate yields. Fluorination induced significant red shifts in absorption (16 to 29 nm) and emission (13 to 41 nm) maxima, and increased electrophilicity as evidenced by lower reduction potentials. X‐ray structural analysis showed distinct packing patterns compared to the non‐fluorinated analogues, indicating the presence of molecular dipoles. 

Structural elements are widespread across genomes, but their complexity and role in repeatedly driving local adaptation remain unclear. In this work, we use phased genome assemblies to show that adaptive divergence in cryptic color pattern in a stick insect is repeatedly underlain by structural variation, but not a simple chromosomal inversion. We found that color pattern in populations of stick insects on two mountains is associated with translocations that have also been inverted. These translocations differ in size and origin on each mountain, but they overlap partially and involve some of the same gene regions. Moreover, this structural variation is subject to divergent selection and arose without introgression between species. Our results show how the origin of structural variation provides a mechanism for repeated bouts of adaptation. 

Abstract Throughout the halogen bonding literature, electron withdrawing groups are relied upon heavily for tuning the interaction strength between the halogen bond donor and acceptor; however, the interplay of electronic effects associated with various substituents is less of a focus. This work utilizes computational techniques to study the degree ofσ‐ andπ‐electron donating/accepting character of electron withdrawing groups in a prescribed set of halo‐alkyne, halo‐benzene, and halo‐ethynyl benzene halogen bond donors. We examine how these factors affect theσ‐hole magnitude of the donors as well as the binding strength of the corresponding complexes with an ammonia acceptor. Statistical analyses aid the interpretation of how these substituents influence the properties of the halogen bond donors and complexes, and show that the electron withdrawing groups that are bothσ‐ andπ‐electron accepting form the strongest halogen bond complexes. 

Sponges (phylum Porifera) possess biochemical, cellular, and physiological traits with valuable biotechnical applications. However, our ability to harness these natural innovations is limited by a classification system that does not fully reflect their evolutionary history. In this study, we uncover numerous cryptic species within the genus Halichondria that are morphologically indistinguishable from the well-known Ha. panicea. Many of these species have habitat preferences and geographic distributions that strongly suggest they have been dispersed by human activity. Most of these species are broadly sympatric with their closest relatives, and these overlapping distributions allow us to use patterns of DNA variation to infer reproductive isolation between clades in nature. With reproductively isolated species thus delineated, we can use DNA states as taxonomic characters to formally describe them. Though much remains to be learned about these newly discovered species, the natural “common gardens” of these sponges in California, New York, and other locations provide opportunities to test hypotheses about their diversification in future work.