The role of hydraulic conductivity in the Pine Island Glacier's subglacial water distribution.

Global climate warming leads to ever-increasing glacier mass loss. Pine Island Glacier in Antarctica is one of the largest contributors to global sea level rise (SLR). One of the biggest uncertainties in the assessment of glacier contribution to SLR at present are subglacial hydrology processes which are less well known than other ice dynamical processes. We use the Glacier Drainage System (GlaDS) model which couples both distributed and channelized components to simulate the basal hydrology of Pine Island Glacier with basal sliding and meltwater production taken from a full-Stokes Elmer/Ice model fitting observed surface velocities. We find ≈100 km long Rothlisberger channels up to 26 m in diameter extending up glacier from the grounding line along the main trunk of Pine Island Glacier delivering 51 m3 s-1 of fresh water to the grounding line. Channelization occurs at high water pressure because of high basal melt rates (maximum of 1 m a-1) caused by high rates of shear heating in regions with fast ice flow (>1000 m a-1). We simulate a shallow "swamp" of 0.8 m water depth where flow transitions from a distributed system into the channels. We performed a set of 38 sensitivity experiments varying sheet and channel conductivity over 4 orders of magnitude. We find a threshold behavior in distributed sheet conductivity above which basal water pressures are unaffected by changing channel conductivities. Our findings suggest a strong need to better understand controls on basal water conductivity through the distributed system. This issue is critical to improve model-based predictive capability for the Pine Island Glacier and, more generally, the Antarctic Ice Sheet.

Delayed Antarctic melt season reduces albedo feedback.

Antarctica's response to climate change varies greatly both spatially and temporally. Surface melting impacts mass balance and also lowers surface albedo. We use a 43-year record (from 1978 to 2020) of Antarctic snow melt seasons from space-borne microwave radiometers with a machine-learning algorithm to show that both the onset and the end of the melt season are being delayed. Granger-causality analysis shows that melt end is delayed due to increased heat flux from the ocean to the atmosphere at minimum sea-ice extent from warming oceans. Melt onset is Granger-caused primarily by the turbulent heat flux from ocean to atmosphere that is in turn driven by sea-ice variability. Delayed snowmelt season leads to a net decrease in the absorption of solar irradiance, as a delayed summer means that higher albedo occurs after the period of maximum solar radiation, which changes Antarctica's radiation balance more than sea-ice cover.

Feasibility of ice sheet conservation using seabed anchored curtains.

Sea level rise is expected to be rapid and extremely damaging to coastal communities and infrastructure, with unavoidable losses and coastal protection costs in the tens of billions per year. Retreat of the Thwaites and Pine Island Glaciers is likely already in an unstable regime as their oceanic fronts are ablated by deep intruding layers of relatively warm seawater. Warm water can be blocked from reaching the grounding line by thin flexible buoyant curtains anchored to the seabed. The consequent reduction in ice shelf melting could result in increased ice sheet buttressing as the shelf makes contact with seabed highs. Flexible curtains are less costly than solid artificial barriers, more robust against iceberg collisions, and easier to repair or remove in the event of unforeseen side effects. We illustrate the technical viability of this approach by considering curtain design concepts that should withstand oceanographic forces, and feasible methods of installation. Suitable materials are commonly available. Installation of a seabed curtain in temperate ocean waters would be entirely within the capabilities of existing offshore and deep ocean construction techniques. Installing in polar waters presents severe challenges from icebergs, harsh weather, and brief working seasons, which can however, be overcome with present-day technology. An 80 km long curtain installed in 600 m deep waters on alluvial sediments could help stabilize Pine Island and Thwaites glaciers over the next few centuries at much lower cost ($40-80 billion + $1-2 billion/yr maintenance) than the global coastline protection (∼$40 billion/yr) needed due to their collapse.

Implication of stratospheric aerosol geoengineering on compound precipitation and temperature extremes in Africa.

Three Coupled Model Intercomparison Project 5 (CMIP5) models that simulated the G4 experiment of the Geoengineering Model Intercomparison Project (GeoMIP) were used to investigate the impact of stratospheric aerosol injection (SAI) on combined temperature and precipitation extremes in Africa that can have greater negative impacts on human and the environment than individual rainfall or temperature extremes. The examined compound extremes included the dry (Rwarm׀dry and Rcold׀dry) and wet (Rwarm׀wet and Rcold׀wet) modes assessed during the injection (SAI, 2050-2069) and post-injection (postSAI, 2070-2089) periods compared with the historical period (1986-2005). We found a significant projected change in the occurrence of both wet and dry modes during SAI and postSAI related to the historical period. The magnitude and sign of this change depend on the season and the geographical location. During the SAI and postSAI, the wet (Rwarm׀wet and Rcold׀wet) modes are projected to be significantly lower while the dry modes are noted to increase in a large part of African continent depending on the season and the geographical location and may consequently leads to an increase of the droughts prone areas. The termination effect is noted to reduce the occurrence of dry modes, which may reduce the potential negative effects of the injection after halting. As the effect may vary from one region to another and according to the season, it suggested assessing the key sector impacts of SAI. Thus, this change in dry modes due to SAI could affect all activities which depend on water resources such as water supply, agriculture and food production, energy demand, and production with adverse effects on health, security, and sustainable development, but this needs to be assessed and quantified at regional scales.

Potential health and economic impacts of shifting manufacturing from China to Indonesia or India.

The diversification or decoupling of production chains from China to alternative Asian countries such as India or Indonesia would impact the spatial distribution of anthropogenic emissions, with corresponding economic impacts due to mortality associated with particulate matter exposure. We evaluated these changes using the Community Earth System Model, the Integrated Exposure-Response (IER) model and Willingness To Pay (WTP) method. Significant effects on PM2.5 related mortality and economic cost for these deaths were seen in many East, Southeast and South Asian countries, particularly those immediately downwind of these three countries. Transferring all of export-related manufacturing to Indonesia resulted in significant mortality decreases in China and South Korea by 78k (5 per 100k) and 1k (2 per 100k) respectively, while Indonesia's mortality significantly increased (73.7k; 29 per 100k), as well as India, Pakistan and Nepal. When production was transferred to India, mortality rates in East Asia show similar changes to the Indonesian scenario, while mortalities in India increased dramatically (87.9k; 6 per 100k), and mortalities in many neighbors of India were also severely increased. Nevertheless, the economic costs for PM2.5 related mortality were much smaller than national GDP changes in China (0.9 % of GDP vs. 18.3 % of GDP), India (2.7 % of GDP vs. 84.3 % of GDP) or Indonesia (9.4 % of GDP vs. 337 % of GDP) due to shifting all of export-related production lines from China to India or Indonesia. Morally, part of the benefits of economic activity should be used to compensate the neighboring communities where mortality increases occur.

Single-cell imaging of T cell immunotherapy responses in vivo.

T cell immunotherapies have revolutionized treatment for a subset of cancers. Yet, a major hurdle has been the lack of facile and predicative preclinical animal models that permit dynamic visualization of T cell immune responses at single-cell resolution in vivo. Here, optically clear immunocompromised zebrafish were engrafted with fluorescent-labeled human cancers along with chimeric antigen receptor T (CAR T) cells, bispecific T cell engagers (BiTEs), and antibody peptide epitope conjugates (APECs), allowing real-time single-cell visualization of T cell-based immunotherapies in vivo. This work uncovered important differences in the kinetics of T cell infiltration, tumor cell engagement, and killing between these immunotherapies and established early endpoint analysis to predict therapy responses. We also established EGFR-targeted immunotherapies as a powerful approach to kill rhabdomyosarcoma muscle cancers, providing strong preclinical rationale for assessing a wider array of T cell immunotherapies in this disease.

The re-imagining of a framework for agricultural land use: A pathway for integrating agricultural practices into ecosystem services, planetary boundaries and sustainable development goals : This article belongs to Ambio's 50th Anniversary Collection. Theme: Agricultural land use.

This paper reflects on the legacy of the Ambio papers by Sombroek et al. (1993), Turner et al. (1994), and Brussaard et al. (1997) on the study of agricultural land use and its impacts on global carbon storage and nutrient dynamics. The papers were published at a time of transition in ecology that involved the integration of humans as components of ecosystems, the formulation of the ecosystem services, and emergence of sustainability science. The papers offered new frameworks to studying agricultural land use across multiple scales in a way that captured causality from interacting components of the system. Each paper argued for more comprehensive data sets; foreseeing the power of network-based science, the potential of molecular technologies to assess biodiversity, and advances in remote sensing. The papers have contributed both conceptual framings and methodological approaches to an ongoing movement to identify a pathway to study agricultural land use and environmental change that fit within the concepts of ecosystem services, planetary boundaries and sustainable development goals.

Mitigation of Arctic permafrost carbon loss through stratospheric aerosol geoengineering.

The Arctic is warming far faster than the global average, threatening the release of large amounts of carbon presently stored in frozen permafrost soils. Increasing Earth's albedo by the injection of sulfate aerosols into the stratosphere has been proposed as a way of offsetting some of the adverse effects of climate change. We examine this hypothesis in respect of permafrost carbon-climate feedbacks using the PInc-PanTher process model driven by seven earth system models running the Geoengineering Model Intercomparison Project (GeoMIP) G4 stratospheric aerosol injection scheme to reduce radiative forcing under the Representative Concentration Pathway (RCP) 4.5 scenario. Permafrost carbon released as CO2 is halved and as CH4 by 40% under G4 compared with RCP4.5. Economic losses avoided solely by the roughly 14 Pg carbon kept in permafrost soils amount to about US$ 8.4 trillion by 2070 compared with RCP4.5, and indigenous habits and lifestyles would be better conserved.

Visualizing Engrafted Human Cancer and Therapy Responses in Immunodeficient Zebrafish.

Xenograft cell transplantation into immunodeficient mice has become the gold standard for assessing pre-clinical efficacy of cancer drugs, yet direct visualization of single-cell phenotypes is difficult. Here, we report an optically-clear prkdc-/-, il2rga-/- zebrafish that lacks adaptive and natural killer immune cells, can engraft a wide array of human cancers at 37°C, and permits the dynamic visualization of single engrafted cells. For example, photoconversion cell-lineage tracing identified migratory and proliferative cell states in human rhabdomyosarcoma, a pediatric cancer of muscle. Additional experiments identified the preclinical efficacy of combination olaparib PARP inhibitor and temozolomide DNA-damaging agent as an effective therapy for rhabdomyosarcoma and visualized therapeutic responses using a four-color FUCCI cell-cycle fluorescent reporter. These experiments identified that combination treatment arrested rhabdomyosarcoma cells in the G2 cell cycle prior to induction of apoptosis. Finally, patient-derived xenografts could be engrafted into our model, opening new avenues for developing personalized therapeutic approaches in the future.

Dependence of the evolution of carbon dynamics in the northern permafrost region on the trajectory of climate change.

We conducted a model-based assessment of changes in permafrost area and carbon storage for simulations driven by RCP4.5 and RCP8.5 projections between 2010 and 2299 for the northern permafrost region. All models simulating carbon represented soil with depth, a critical structural feature needed to represent the permafrost carbon-climate feedback, but that is not a universal feature of all climate models. Between 2010 and 2299, simulations indicated losses of permafrost between 3 and 5 million km2 for the RCP4.5 climate and between 6 and 16 million km2 for the RCP8.5 climate. For the RCP4.5 projection, cumulative change in soil carbon varied between 66-Pg C (1015-g carbon) loss to 70-Pg C gain. For the RCP8.5 projection, losses in soil carbon varied between 74 and 652 Pg C (mean loss, 341 Pg C). For the RCP4.5 projection, gains in vegetation carbon were largely responsible for the overall projected net gains in ecosystem carbon by 2299 (8- to 244-Pg C gains). In contrast, for the RCP8.5 projection, gains in vegetation carbon were not great enough to compensate for the losses of carbon projected by four of the five models; changes in ecosystem carbon ranged from a 641-Pg C loss to a 167-Pg C gain (mean, 208-Pg C loss). The models indicate that substantial net losses of ecosystem carbon would not occur until after 2100. This assessment suggests that effective mitigation efforts during the remainder of this century could attenuate the negative consequences of the permafrost carbon-climate feedback.

Dissecting hematopoietic and renal cell heterogeneity in adult zebrafish at single-cell resolution using RNA sequencing.

Recent advances in single-cell, transcriptomic profiling have provided unprecedented access to investigate cell heterogeneity during tissue and organ development. In this study, we used massively parallel, single-cell RNA sequencing to define cell heterogeneity within the zebrafish kidney marrow, constructing a comprehensive molecular atlas of definitive hematopoiesis and functionally distinct renal cells found in adult zebrafish. Because our method analyzed blood and kidney cells in an unbiased manner, our approach was useful in characterizing immune-cell deficiencies within DNA-protein kinase catalytic subunit (prkdc), interleukin-2 receptor γ a (il2rga), and double-homozygous-mutant fish, identifying blood cell losses in T, B, and natural killer cells within specific genetic mutants. Our analysis also uncovered novel cell types, including two classes of natural killer immune cells, classically defined and erythroid-primed hematopoietic stem and progenitor cells, mucin-secreting kidney cells, and kidney stem/progenitor cells. In total, our work provides the first, comprehensive, single-cell, transcriptomic analysis of kidney and marrow cells in the adult zebrafish.

Endothelial Notch signalling limits angiogenesis via control of artery formation.

Angiogenic sprouting needs to be tightly controlled. It has been suggested that the Notch ligand dll4 expressed in leading tip cells restricts angiogenesis by activating Notch signalling in trailing stalk cells. Here, we show using live imaging in zebrafish that activation of Notch signalling is rather required in tip cells. Notch activation initially triggers expression of the chemokine receptor cxcr4a. This allows for proper tip cell migration and connection to the pre-existing arterial circulation, ultimately establishing functional arterial-venous blood flow patterns. Subsequently, Notch signalling reduces cxcr4a expression, thereby preventing excessive blood vessel growth. Finally, we find that Notch signalling is dispensable for limiting blood vessel growth during venous plexus formation that does not generate arteries. Together, these findings link the role of Notch signalling in limiting angiogenesis to its role during artery formation and provide a framework for our understanding of the mechanisms underlying blood vessel network expansion and maturation.

Simulated climate effects of desert irrigation geoengineering.

Geoengineering, the deliberate large-scale manipulation of earth's energy balance to counteract global warming, is an attractive proposition for sparsely populated deserts. We use the BNU and UVic Earth system models to simulate the effects of irrigating deserts under the RCP8.5 scenario. Previous studies focused on increasing desert albedo to reduce global warming; in contrast we examine how extending afforestation and ecological projects, that successfully improve regional environments, fair for geoengineering purposes. As expected desert irrigation allows vegetation to grow, with bare soil or grass gradually becoming shrub or tree covered, with increases in terrestrial carbon storage of 90.3 Pg C (UVic-ESCM) - 143.9 Pg C (BNU-ESM). Irrigating global deserts makes the land surface temperature decrease by 0.48 °C and land precipitation increase by 100 mm yr-1. In the irrigated areas, BNU-ESM simulates significant cooling of up to 4.2 °C owing to the increases in low cloud and latent heat which counteract the warming effect due to decreased surface albedo. Large volumes of water would be required to maintain global desert irrigation, equivalent 10 mm/year of global sea level (BNU-ESM) compensate for evapotranspiration losses. Differences in climate responses between the deserts prompt research into tailored albedo-irrigation schemes.

Coastal sea level rise with warming above 2 °C.

Two degrees of global warming above the preindustrial level is widely suggested as an appropriate threshold beyond which climate change risks become unacceptably high. This "2 °C" threshold is likely to be reached between 2040 and 2050 for both Representative Concentration Pathway (RCP) 8.5 and 4.5. Resulting sea level rises will not be globally uniform, due to ocean dynamical processes and changes in gravity associated with water mass redistribution. Here we provide probabilistic sea level rise projections for the global coastline with warming above the 2 °C goal. By 2040, with a 2 °C warming under the RCP8.5 scenario, more than 90% of coastal areas will experience sea level rise exceeding the global estimate of 0.2 m, with up to 0.4 m expected along the Atlantic coast of North America and Norway. With a 5 °C rise by 2100, sea level will rise rapidly, reaching 0.9 m (median), and 80% of the coastline will exceed the global sea level rise at the 95th percentile upper limit of 1.8 m. Under RCP8.5, by 2100, New York may expect rises of 1.09 m, Guangzhou may expect rises of 0.91 m, and Lagos may expect rises of 0.90 m, with the 95th percentile upper limit of 2.24 m, 1.93 m, and 1.92 m, respectively. The coastal communities of rapidly expanding cities in the developing world, and vulnerable tropical coastal ecosystems, will have a very limited time after midcentury to adapt to sea level rises unprecedented since the dawn of the Bronze Age.

Single-cell imaging of normal and malignant cell engraftment into optically clear prkdc-null SCID zebrafish.

Cell transplantation into immunodeficient mice has revolutionized our understanding of regeneration, stem cell self-renewal, and cancer; yet models for direct imaging of engrafted cells has been limited. Here, we characterize zebrafish with mutations in recombination activating gene 2 (rag2), DNA-dependent protein kinase (prkdc), and janus kinase 3 (jak3). Histology, RNA sequencing, and single-cell transcriptional profiling of blood showed that rag2 hypomorphic mutant zebrafish lack T cells, whereas prkdc deficiency results in loss of mature T and B cells and jak3 in T and putative Natural Killer cells. Although all mutant lines engraft fluorescently labeled normal and malignant cells, only the prkdc mutant fish reproduced as homozygotes and also survived injury after cell transplantation. Engraftment into optically clear casper, prkdc-mutant zebrafish facilitated dynamic live cell imaging of muscle regeneration, repopulation of muscle stem cells within their endogenous niche, and muscle fiber fusion at single-cell resolution. Serial imaging approaches also uncovered stochasticity in fluorescently labeled leukemia regrowth after competitive cell transplantation into prkdc mutant fish, providing refined models to assess clonal dominance and progression in the zebrafish. Our experiments provide an optimized and facile transplantation model, the casper, prkdc mutant zebrafish, for efficient engraftment and direct visualization of fluorescently labeled normal and malignant cells at single-cell resolution.

T Cell Immune Deficiency in zap70 Mutant Zebrafish.

ZAP70 [zeta-chain (TCR)-associated protein kinase, 70-kDa], is required for T cell activation. ZAP70 deficiencies in humans and null mutations in mice lead to severe combined immune deficiency. Here, we describe a zap70 loss-of-function mutation in zebrafish (zap70 y442 ) that was created using transcription activator-like effector nucleases (TALENs). In contrast to what has been reported for morphant zebrafish, zap70 y442 homozygous mutant zebrafish displayed normal development of blood and lymphatic vasculature. Hematopoietic cell development was also largely unaffected in mutant larvae. However, mutant fish had reduced lck:GFP + thymic T cells by 5 days postfertilization that persisted into adult stages. Morphological analysis, RNA sequencing, and single-cell gene expression profiling of whole kidney marrow cells of adult fish revealed complete loss of mature T cells in zap70 y442 mutant animals. T cell immune deficiency was confirmed through transplantation of unmatched normal and malignant donor cells into zap70 y442 mutant zebrafish, with T cell loss being sufficient for robust allogeneic cell engraftment. zap70 mutant zebrafish show remarkable conservation of immune cell dysfunction as found in mice and humans and will serve as a valuable model to study zap70 immune deficiency.

China's Land-Use Changes during the Past 300 Years: A Historical Perspective.

Understanding the processes of historical land-use change is crucial to the research of global environmental sustainability. Here we examine and attempt to disentangle the evolutionary interactions between land-use change and its underlying causes through a historical lens. We compiled and synthesized historical land-use change and various biophysical, political, socioeconomic, and technical datasets, from the Qing dynasty to modern China. The analysis reveals a clear transition period between the 1950s and the 1980s. Before the 1950s, cropland expanded while forested land diminished, which was also accompanied by increasing population; after the 1980s land-use change exhibited new characteristics: changes in cropland, and decoupling of forest from population as a result of agricultural intensification and globalization. Chinese political policies also played an important and complex role, especially during the 1950s-1980s transition periods. Overall, climate change plays an indirect but fundamental role in the dynamics of land use via a series of various cascading effects such as shrinking agricultural production proceeding to population collapse and outbreaks of war. The expected continuation of agricultural intensification this century should be able to support increasing domestic demand for richer diets, but may not be compatible with long-term environmental sustainability.

Weighting and indirect effects identify keystone species in food webs.

Species extinctions are accelerating globally, yet the mechanisms that maintain local biodiversity remain poorly understood. The extinction of species that feed on or are fed on by many others (i.e. 'hubs') has traditionally been thought to cause the greatest threat of further biodiversity loss. Very little attention has been paid to the strength of those feeding links (i.e. link weight) and the prevalence of indirect interactions. Here, we used a dynamical model based on empirical energy budget data to assess changes in ecosystem stability after simulating the loss of species according to various extinction scenarios. Link weight and/or indirect effects had stronger effects on food-web stability than the simple removal of 'hubs', demonstrating that both quantitative fluxes and species dissipating their effects across many links should be of great concern in biodiversity conservation, and the potential for 'hubs' to act as keystone species may have been exaggerated to date.