Field and remote sensing studies suggest that ice mélange influences glacier–fjord systems by exerting stresses on glacier termini and releasing large amounts of freshwater into fjords. The broader impacts of ice mélange over long timescales are unknown, in part due to a lack of suitable ice mélange flow models. Previous efforts have included modifying existing viscous ice shelf models, despite the fact that ice mélange is fundamentally a granular material, and running computationally expensive discrete element simulations. Here, we draw on laboratory studies of granular materials, which exhibit viscous flow when stresses greatly exceed the yield point, plug flow when the stresses approach the yield point, and exhibit stress transfer via force chains. By implementing the nonlocal granular fluidity rheology into a depth- and width-integrated stress balance equation, we produce a numerical model of ice mélange flow that is consistent with our understanding of well-packed granular materials and that is suitable for long-timescale simulations. For parallel-sided fjords, the model exhibits two possible steady-state solutions. When there is no calving of icebergs or melting of previously calved icebergs, the ice mélange is pushed down-fjord by the advancing glacier terminus, the velocity is constant along the length of the fjord, and the thickness profile is exponential. When calving and melting are included and treated as constants, the ice mélange evolves into another steady state in which its location is fixed relative to the fjord walls, the thickness profile is relatively steep, and the flow is extensional. For the latter case, the model predicts that the steady-state ice mélange buttressing force depends on the surface and basal melt rates through an inverse power-law relationship, decays roughly exponentially with both fjord width and gradient in fjord width, and increases with the iceberg calving flux. The buttressing force appears to increase with calving flux (i.e., glacier thickness) more rapidly than the force required to prevent the capsizing of full-glacier-thickness icebergs, suggesting that glaciers with high calving fluxes may be more strongly influenced by ice mélange than those with small fluxes.

Ceramides are a family of wax-like lipids that fall under the broader category of sphingolipids. A ceramide is composed of a sphingosine side chain coupled to a fatty acid via an amide linkage. Distinct from complex sphingolipids, the head of ceramide is a simple alcohol rather than a phosphate, phosphocholine, sugar, or more. The fatty acid chains of ceramide can also vary in chain length and degree of saturation. The degree of saturation may determine the biological activity of the ceramide species. Ceramides are highly abundant within the cell membrane of eukaryotic cells and are appreciated for their structural roles in these cells. Moreover, ceramides are well known for their biological activity including as regulators of apoptosis, senescence, the cell cycle, and differentiation. This review discusses pathways of ceramide, roles of ceramide in various diseases, targeting ceramide metabolism in the treatment of cancer, as well as ceramide-delivering nanotechnologies.

Acute myeloid leukemia (AML) is an aggressive, heterogeneous disease with genomic subtypes that are increasingly treated differently. There is a growing interest in going beyond mutations and cytogenetics to stratify AML. Recent work has combined proteomics,1 signaling,2,3 or immunophenotypes4 with integrated genomic-transcriptomic measurements to improve AML risk classifications.5 Although invaluable as resources, such approaches can neither extend retroactively to existing repositories nor prospectively to new AML cases lacking these data types. We sought to develop a more extensible approach involving sphingolipids (Figure 1A), a family of bioactive molecules implicated in AML pathogenesis and therapeutic resistance6,7 that differentially regulate cell proliferation,8 differentiation,9 autophagy,10 apoptosis,11 and immune cell activation.12 Sphingolipid abundances in AML vary heterogeneously and ratiometrically,13 prompting us to ask whether systematic sphingolipidomic profiling could meaningfully stratify patients with AML and common AML cell lines.

Runoff from rapidly melting mountain glaciers is a dominant source of riverine organic carbon in many high-latitude and high-elevation regions. Glacier dissolved organic carbon is highly bioavailable, and its composition likely reflects internal (e.g., autotrophic production) and external (i.e., atmospheric deposition) sources. However, the balance of these sources across Earth's glaciers is poorly understood, despite implications for the mineralization and assimilation of glacier organic carbon within recipient ecosystems. We assessed the molecular-level composition of dissolved organic matter from 136 mountain glacier outflows from 11 regions covering six continents using ultrahigh resolution 21 T mass spectrometry. We found substantial diversity in organic matter composition with coherent and predictable (80% accuracy) regional patterns. Employing stable and radiocarbon isotopic analyses, we demonstrate that these patterns are inherently linked to atmospheric deposition and in situ production. In remote regions like Greenland and New Zealand, the glacier organic matter pool appears to be dominated by in situ production. However, downwind of industrial centers (e.g., Alaska and Nepal), fossil fuel combustion byproducts likely underpin organic matter composition, resulting in older and more aromatic material being exported downstream. These findings highlight that the glacier carbon cycle is spatially distinct, with ramifications for predicting the dynamics and fate of glacier organic carbon concurrent with continued retreat and anthropogenic perturbation.

Pacific herring Clupea pallasii are a critical commercial and subsistence fish species and play a keystone role in the ecology and culture of the North Pacific. The annual herring spawn, in which mature herring migrate nearshore to deposit eggs along the coastline, is an important event linked to the migration of seabirds and marine mammals as well as a subsistence harvest for Alaska Natives and First Nations in British Columbia. Previous work has suggested that environmental variables and broad teleconnection indices play a role in the magnitude and phenology of spawning; however, the effects of these drivers have not been examined in the context of future climate scenarios. Here, we modeled variability in the timing of herring spawn across British Columbia and Southeast Alaska using survey data from 1951-2022. We created a model using Pacific teleconnection indices, sea surface temperature (SST), tidal height, and lagged data to predict spawn date anomalies (SDAs) across 9 spawning regions. SDAs were significantly affected by the Oceanic Niño Index, Pacific Decadal Oscillation, SST, and lagged SDAs. We then used this model to predict SDAs using projected SST from climate models and bootstrapped teleconnection data from 2025-2100. Future herring spawn timing trends earlier on average with warming SSTs, although the magnitude is relatively small, occurring 9 d earlier on average by 2100. This changing phenology, though small, varied by region and may have ecosystem-level ramifications and create timing mismatch for migratory species. However, our findings also reinforce the importance of other physical factors not measured in this study, such as photoperiod, which drive herring spawn timing.

Land and ocean ecosystems are strongly connected and mutually interactive. As climate changes and other anthropogenic stressors intensify, the complex pathways that link these systems will strengthen or weaken in ways that are currently beyond reliable prediction. In this review we offer a framework of land–ocean couplings and their role in shaping marine ecosystems in coastal temperate rainforest (CTR) ecoregions, where high freshwater and materials flux result in particularly strong land–ocean connections. Using the largest contiguous expanse of CTR on Earth—the Northeast Pacific CTR (NPCTR)—as a case study, we integrate current understanding of the spatial and temporal scales of interacting processes across the land–ocean continuum, and examine how these processes structure and are defining features of marine ecosystems from nearshore to offshore domains. We look ahead to the potential effects of climate and other anthropogenic changes on the coupled land–ocean meta-ecosystem. Finally, we review key data gaps and provide research recommendations for an integrated, transdisciplinary approach with the intent to guide future evaluations of and management recommendations for ongoing impacts to marine ecosystems of the NPCTR and other CTRs globally. In the light of extreme events including heatwaves, fire, and flooding, which are occurring almost annually, this integrative agenda is not only necessary but urgent.

Mountain environments with snow avalanche hazard cover about 6% of Earth’s land area and occur on all continents. Whereas human risks associated with avalanche hazard have been widely studied, little is known about how avalanche activity affects population dynamics in mountain wildlife. Globally, 32 species of mountain ungulates across 70 countries occupy avalanche-prone terrain. Avalanches comprise the leading cause of mortality in coastal Alaskan mountain goats (mean = 36%, range = 23 - 65%, depending on area), and disproportionately remove prime-aged individuals from populations. The implications of such rates and patterns of mortality on population growth rate are likely to be significant given the species’ low reproductive productivity, but further clarity is needed. To fill this knowledge gap, we developed a sex- and age-specific population modeling approach that integrates both reproduction and mortality to simulate the effects of avalanche-caused mortality on population growth rate across a range of empirically-observed states of avalanche-caused mortality (minimum, mean, maximum). Simulations were conducted to illustrate model functionality, and also provide insight about potential avalanche impacts on population demographic processes. For example, when severe avalanche years occur populations can experience significant additive mortality and declines (up to 15%). Due to low reproductive rates and slow life-history strategy of the species, such impacts can lead to long demographic recovery times (up to 11 years). From a species conservation perspective, such impacts are striking, and highlight the utility of employing a quantitative modeling approach to predict possible effects of avalanches on mountain ungulate population dynamics and viability. Our work explicitly builds upon recent findings about the importance of avalanches on mountain-adapted animal populations, and associated implications for the cultural and ecological communities that depend on them.