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Abstract The Last Ice Area—located to the north of Greenland and the northern Canadian Arctic Archipelago—is expected to persist as the central Arctic Ocean becomes seasonally ice-free within a few decades. Projections of the Last Ice Area, however, have come from relatively low resolution Global Climate Models that do not resolve sea ice export through the waterways of the Canadian Arctic Archipelago and Nares Strait. Here we revisit Last Ice Area projections using high-resolution numerical simulations from the Community Earth System Model, which resolves these narrow waterways. Under a high-end forcing scenario, the sea ice of the Last Ice Area thins and becomes more mobile, resulting in a large export southward. Under this potentially worst-case scenario, sea ice of the Last Ice Area could disappear a little more than one decade after the central Arctic Ocean has reached seasonally ice-free conditions. This loss would have profound impacts on ice-obligate species. 

The ongoing opioid epidemic has been met with the inadequate use of data-informed approaches to respond to the crisis. Although data relevant to opioid and substance use do exist and have been utilized for research in the literature and practice, they have not been prepared for cross-sector coordination and for providing practical intelligence to inform policy planning directly. In this article, we share our views on how data can better serve the purposes of informing policy and planning to maximize population health and safety benefits. Based on our experience in advising state policymakers on developing settlement allocation strategies based on empirical data, we discuss several issues in the data, including coverage, specificity in drug types, time relevance, geographic units, and access, which may hinder data-informed policymaking. Following these discussions, we envision a coordinated data and policy framework as an ideal case to ensure access to meaningful and timely data and harness the full potential of the data to inform policy to combat the continuing epidemic. 

Abstract Fluid-mediated calcium metasomatism is often associated with strong silica mobility and the presence of chlorides in solution. To help quantify mass transfer at lower crustal and upper mantle conditions, we measured quartz solubility in H2O-CaCl2 solutions at 0.6–1.4 GPa, 600–900 °C, and salt concentrations to 50 mol%. Solubility was determined by weight loss of single-crystals using hydrothermal piston-cylinder methods. All experiments were conducted at salinity lower than salt saturation. Quartz solubility declines exponentially with added CaCl2 at all conditions investigated, with no evidence for complexing between silica and Ca. The decline in solubility is similar to that in H2O-CO2 but substantially greater than that in H2O-NaCl at the same pressure and temperature. At each temperature, quartz solubility at low salinity (XCaCl2 < 0.1) depends strongly on pressure, whereas at higher XCaCl2 it is nearly pressure independent. This behavior is consistent with a transition from an aqueous solvent to a molten salt near XCaCl2 ~0.1. The solubility data were used to develop a thermodynamic model of H2O-CaCl2 fluids. Assuming ideal molten-salt behavior and utilizing previous models for polymerization of hydrous silica, we derived values for the activity of H2O (aH2O), and for the CaCl2 dissociation factor (α), which may vary from 0 (fully associated) to 2 (fully dissociated). The model accurately reproduces our data along with those of previous work and implies that, at conditions of this study, CaCl2 is largely associated (<0.2) at H2O density <0.85 g/cm3. Dissociation rises isothermally with increasing density, reaching ~1.4 at 600 °C, 1.4 GPa. The variation in silica molality with aH2O in H2O-CaCl2 is nearly identical to that in H2O-CO2 solutions at 800 °C and 1.0 GPa, consistent with the absence of Ca-silicate complexing. The results suggest that the ionization state of the salt solution is an important determinant of aH2O, and that H2O-CaCl2 fluids exhibit nearly ideal molecular mixing over a wider range of conditions than implied by previous modeling. The new data help interpret natural examples of large-scale Ca-metasomatism in a wide range of lower crustal and upper mantle settings. 

We quantify changes in break‐up events of landfast ice in the transition from a perennial to a seasonal sea ice cover in the Arctic. A break‐up event is defined as a time when coastal sea ice concentration drops below 95% after a minimum period of 10 days of stable ice conditions. To this end we analyze output diagnostics from the Community Earth System Model (Version 1) – Large Ensemble from 1920 to 2080, focusing on six coastal communities of Alaska, Chukotka, and the Kamtchatka Peninsula: Utqiaġvik, Point Hope, Gambell, Novoye Chaplino, Sireniki, and Pakhachi. Model results generally agree with the satellite record with open water formation along the coastline associated with sustained offshore winds, although the sensitivity of CESM1‐LE is higher than that of observations due to the absence of a landfast ice parameterization in CESM1‐ LE. Specifically, we see a linear relationship between the magnitude of the opening and offshore surface wind stresses integrated over the 10 days prior to the opening event, (p‐value < 0.01). While the break‐up event frequency increases (5.53 × 10−5 events/day/year for Utqiagvik) in the 21st century due to the thin- ning, or weakening, of the landfast ice cover, the total number of winter break‐up events decreases due to a shortening of the winter season (mean of ‐5.3 days/decade). 

Abstract. Free-drift estimates of sea ice motion are necessary to produce a seamless observational record combining buoy and satellite-derived sea ice motionvectors. We develop a new parameterization for the free drift of sea ice based on wind forcing, wind turning angle, sea ice state variables(thickness and concentration), and estimates of the ocean currents. Given the fact that the spatial distribution of the wind–ice–ocean transfercoefficient has a similar structure to that of the spatial distribution of sea ice thickness, we take the standard free-drift equation and introducea wind–ice–ocean transfer coefficient that scales linearly with ice thickness. Results show a mean bias error of −0.5 cm s−1(low-speed bias) and a root-mean-square error of 5.1 cm s−1, considering daily buoy drift data as truth. This represents a 35 %reduction of the error on drift speed compared to the free-drift estimates used in the Polar Pathfinder dataset (Tschudi et al., 2019b). Thethickness-dependent transfer coefficient provides an improved seasonality and long-term trend of the sea ice drift speed, with a minimum (maximum)drift speed in May (October), compared to July (January) for the constant transfer coefficient parameterizations which simply follow the peak inmean surface wind stresses. Over the 1979–2019 period, the trend in sea ice drift in this new model is +0.45 cm s−1 per decadecompared with +0.39 cm s−1 per decade from the buoy observations, whereas there is essentially no trend in a free-driftparameterization with a constant transfer coefficient (−0.09 cm s−1 per decade) or the Polar Pathfinder free-drift input data(−0.01 cm s−1 per decade). The optimal wind turning angle obtained from a least-squares fitting is 25∘, resulting in a meanerror and a root-mean-square error of +3 and 42∘ on the direction of the drift, respectively. The ocean current estimates obtained from theminimization procedure resolve key large-scale features such as the Beaufort Gyre and Transpolar Drift Stream and are in good agreement with oceanstate estimates from the ECCO, GLORYS, and PIOMAS ice–ocean reanalyses, as well as geostrophic currents from dynamical ocean topography, with aroot-mean-square difference of 2.4, 2.9, 2.6, and 3.8 cm s−1, respectively. Finally, a repeat of the analysis on two sub-sections of thetime series (pre- and post-2000) clearly shows the acceleration of the Beaufort Gyre (particularly along the Alaskan coastline) and an expansion ofthe gyre in the post-2000s, concurrent with a thinning of the sea ice cover and the observed acceleration of the ice drift speed and oceancurrents. This new dataset is publicly available for complementing merged observation-based sea ice drift datasets that include satellite and buoydrift records. 

Abstract Sea ice will persist longer in the Last Ice Area (LIA), north of Canada and Greenland, than elsewhere in the Arctic. We combine earth system model ensembles with a sea‐ice tracking utility (SITU) to explore sources of sea ice (the “ice shed”) to the LIA under two scenarios: continued high warming (HW) rates and low warming (LW) rates (mean global warming below ca. 2°C) through the 21st century. Until mid‐century, the two scenarios yield similar results: the primary ice source shifts from the Russian continental shelves to the central Arctic, mobility increases, and mean ice age in the LIA drops from about 7 years to less than one. After about 2050, sea ice stabilizes in the LW scenario, but continues to decline in the HW scenario until LIA sea ice is nearly entirely seasonal and locally formed. Sea ice pathways through the ice shed determine LIA ice conditions and transport of material, including biota, sediments, and pollutants (spilled oil and industrial or agricultural contaminants have been identified as potential hazards). This study demonstrates that global warming has a dramatic impact on the sources, pathways and ages of ice entering the LIA. Therefore, we suggest that maintaining ice quality and preserving ice‐obligate ecologies in the LIA, including the Tuvaijuittuq Marine Protected Area north of Nunavut, Canada, will require international governance. The SITU system used in this study is publicly available as an online utility to support researchers, policy analysts, and educators interested in past and future sea ice sources and trajectories. 


Research consistently shows that children who have opportunities to actively investigate natural settings and engage in problem-based learning greatly benefit from the experiences. They gain skills, interests, knowledge, aspirations, and motivation to learn more. But how can we provide these rich opportunities in densely populated urban areas where resources and access to natural areas are limited? This project will develop and test a model of curriculum and community enterprise to address that issue within the nation's largest urban school system. Middle school students will study New York harbor and the extensive watershed that empties into it, and they will conduct field research in support of restoring native oyster habitats. The project builds on the existing Billion Oyster Project, and will be implemented by a broad partnership of institutions and community resources, including Pace University, the New York City Department of Education, the Columbia University Lamont-Doherty Earth Observatory, the New York Academy of Sciences, the New York Harbor Foundation, the New York Aquarium, and others.
The project focuses on an important concept in the geological, environmental, and biological sciences that typically receives inadequate attention in schools: watersheds. This project builds on and extends the Billion Oyster Project of the New York Harbor School. The project model includes five interrelated components: A teacher education curriculum, a student learning curriculum, a digital platform for project resources, an aquarium exhibit, and an afterschool STEM mentoring program. It targets middle-school students in low-income neighborhoods with high populations of English language learners and students from groups underrepresented in STEM fields and education pathways. The project will directly involve over forty schools, eighty teachers, and 8,640 students over a period of three years. A quasi-experimental, mixed-methods research plan will be used to assess the individual and collective effectiveness of the five project components. Regression analyses will be used to identify effective program aspects and assess the individual effectiveness of participation in various combinations of the five program components. Social network mapping will be used to further asses the overall "curriculum plus community" model. 

Abstract. Tritium and helium isotope data provide key information on oceancirculation, ventilation, and mixing, as well as the rates of biogeochemicalprocesses and deep-ocean hydrothermal processes. We present here globaloceanic datasets of tritium and helium isotope measurements made by numerousresearchers and laboratories over a period exceeding 60 years. The dataset'sDOI is https://doi.org/10.25921/c1sn-9631, and the data are available athttps://www.nodc.noaa.gov/ocads/data/0176626.xml (last access: 15 March2019) or alternatelyhttp://odv.awi.de/data/ocean/jenkins-tritium-helium-data-compilation/(last access: 13 March 2019) and includes approximately 60 000 valid tritiummeasurements, 63 000 valid helium isotope determinations, 57 000 dissolvedhelium concentrations, and 34 000 dissolved neon concentrations. Somequality control has been applied in that questionable data have been flaggedand clearly compromised data excluded entirely. Appropriate metadata havebeen included, including geographic location, date, and sample depth. Whenavailable, we include water temperature, salinity, and dissolved oxygen. Dataquality flags and data originator information (including methodology) arealso included. This paper provides an introduction to the dataset along withsome discussion of its broader qualities and graphics.