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Parts of the northwest Atlantic Ocean, including the Gulf of Maine, along the northeastern coast of the United States, are warming at a rate as much as four times faster than the global ocean, according to instrumental and satellite records. In addition to the longer-term temperature increases, the frequency and severity of marine heat waves have been increasing. Combined, the ecological impacts are numerous and concerning, yet our understanding of past climate in this region is incomplete due to sparse and short-duration instrumental records. Here we present annually resolved oxygen isotope records from the marine bivalve, Arctica islandica, from five locations ranging from Jonesport and Seguin Island in the Gulf of Maine to Long Island, New York, Cape May, New Jersey, and Ocean City, Maryland in the Mid-Atlantic Bight, a span of over 870 km along the Atlantic coast. Several of the isotope records span the last 100 years or more and all records show coherent, substantial warming since at least 1980 CE. The level of warming indicated in the shell oxygen isotopes is comparable to the 0.5 °C per decade (1980-2020 CE) warming also shown in the instrumental record of sea surface temperature from Boothbay Harbor along the central coast in the Gulf of Maine. These five spatially distant isotope records span different oceanographic conditions and dynamics, including water mass sources, yet they all indicate a substantial warming in recent decades, likely related to increased anthropogenic warming. Beyond reconstructing seawater temperature prior to instrumental records, a major goal of this work is to disentangle the global warming signal from these records to better understand the underlying ocean dynamics also influencing these records. 

Coastal systems can exhibit large variability in pH compared to open marine conditions, thus the impacts of ocean acidification (OA) on their resident calcifying organisms are potentially magnified. Further, our understanding of the natural baseline and variability of pH is spatially and temporally limited in coastal settings. In the few coastal locations that have been monitoring seawater pH, records are generally limited to <10 years and are thus unable to provide the full range of centennial to decadal natural variability. This is the case for the Gulf of Maine (northwestern Atlantic), a highly productive region of strategic importance to U.S. fisheries, that is facing multiple environmental stressors including rapid warming and threats from OA. Paleoceanographic proxy records are therefore much needed in this region to reconstruct past pH conditions beyond instrumental records. A clear candidate for this is the boron isotope (d11B) pH proxy provided the d11B sensitivity to pH in long-lived shallow water marine carbonates can be established. To this end, we grew juvenile and adult Arctica islandica (ocean quahog) in flowing seawater tanks for 20.5 weeks in controlled pH (7.4, 7.6, 7.8 or 8.0 (ambient) ± 0.02) and temperature (6, 9 or 12 ± 0.56 °C) conditions at Bowdoin College’s Schiller Coastal Studies Center, Harpswell, Maine (USA). The clams were stained twice with calcein and supplemented with food (Shellfish Diet) throughout the experiment to ensure suitable growth. New shell growth (average 67% increase in maximum shell height and 522% increase in buoyant weight across all treatments), constrained by calcein markings, were sampled for boron isotope analysis (d11B) to determine if shell d11B varied as a function of pH similar to many other calcifying organisms. The results of the culture experiment will yield whether or not Arctica islandica preserves seawater pH information in their shells. If so, the transfer function relating shell d11B to pH will be used to hindcast pH in the central coastal region of the Gulf of Maine during recent centuries. Alternatively, if the shell d11B signal is independent of ambient seawater pH, this may reveal the capacity of Arctica islandica to regulate internal calcifying fluid chemistry and their resilience to OA. 

Warming in recent decades in the North Atlantic Ocean has been heterogeneous, with locations along the northwestern Atlantic experiencing some of the largest and fastest warming in the last 100 years. This region is important for fisheries but has limited spatial and temporal hydrographic instrumental series extending beyond the past decades, especially along the coastal United States portion of the northwestern Atlantic, thus impacting our understanding of past climatic variability. To provide a longer temporal context for these changes, we constructed a continuous master shell growth chronology spanning the last two centuries and provided geochemical records from the Mid-Atlantic region using the long-lived marine bivalve Arctica islandica. Shells were collected on the outer shelf region off Ocean City, Maryland, in ~ 60 m water depth. This region is sensitive to large-scale North Atlantic Ocean dynamics, including the Atlantic Meridional Overturning Circulation (AMOC) and Gulf Stream eddies. Based on growth histories and shell oxygen isotopes, we provide evidence of hydrographic variability beyond the relatively short instrumental period and evaluate the likely causes for these changes. These data allow us to better characterize recent and past oceanographic changes in the Mid-Atlantic region, synthesize the new results with previously developed paleo-records in the northwestern Atlantic, and provide guidance for the management of fisheries in this region. 

The Gulf of Maine is a highly productive and economically important region in the northwestern Atlantic that has undergone rapid warming in recent decades and is susceptible to ocean acidification (OA). These stressors may have substantial impacts on local fisheries. Therefore, understanding the combined effects of warming and OA to commercially important shellfish is vital. To test responses to warming and OA, Mercenaria mercenaria (hard clam), Mya arenaria (soft-shell clam), Plactopectin magellanicus (sea scallop), and both juvenile and adult Arctica islandica (ocean quahog) were grown in flowing seawater tanks for 20.5 weeks in controlled pH (7.4, 7.6, 7.8 or 8.0 (ambient) ± 0.02) and temperature (6, 9 or 12 ± 0.56 °C) conditions at Bowdoin College’s Schiller Coastal Studies Center. The specimens’ diet was supplemented with high-quality food (Shellfish Diet) throughout the experiment. Temperature effects were a significant contributor in all shell growth metrics (maximum height, dry weight and buoyant weight) in all species except the height and dry weight of adult A. islandica. Additionally, pH effects were significant in the height of M. mercenaria and in the dry weight of juvenile A. islandica samples. Overall, mortality rates ranged from 1.5% in juvenile A. islandica to 24% in M. mercenaria, with results varying by species and treatment conditions. Additionally, differences in final shell condition were noted among the various treatments indicating that, although most of the organisms survived and grew, the elevated temperature and/or lower pH conditions might not have been ideal for thriving. Considering all results of growth and survival, the four species showed a differential response to the same warming and acidification conditions. As suggested by prior research, the availability of high-quality food may allow certain species to tolerate the future warming and/or OA conditions modeled in this experiment. Experimental results may reveal the species-specific resiliency of economically valuable shellfish to changing ocean conditions as well as guide future planning to safeguard regional ecosystems and fisheries. 

The association between student motivation and learning, and changes in motivation across a course, were evaluated for students enrolled in one-semester foundation-level inorganic chemistry courses at multiple postsecondary institutions across the United States. The Academic Motivation Scale for Chemistry (AMS-Chemistry) and the Foundations of Inorganic Chemistry American Chemical Society Exam (i.e., a content knowledge measure) were used in this study. Evidence of validity, reliability, and longitudinal measurement invariance for data obtained from the AMS-Chemistry instrument with this population were found using methodologies appropriate for ordinal, non-parametric data. Positive and significant associations between intrinsic motivation measures and academic performance corroborate theoretical and empirical investigations; however, a lack of pre/post changes in motivation suggest that motivation may be less malleable in courses primarily populated by chemistry majors. Implications for inorganic chemistry instructors include paths for incorporating engaging pedagogies known to promote intrinsic motivation and methods for incorporating affect measures into assessment practices. Implications for researchers include a need for more work that disaggregates chemistry majors when evaluating relationships between affect and learning, and when making pre/post comparisons. Additionally, this work provides an example of how to implement more appropriate methods for treating data in studies using Likert-type responses and nested data. 

Warming in the North Atlantic Ocean has been heterogeneous in recent decades, with locations along the eastern United States seaboard (northwestern Atlantic) seeing some of the largest and fastest warming in the last 100 years. In order to provide a longer temporal context for these changes, we are in the process of developing several master shell growth chronologies and associated geochemical records from theMid-Atlantic coast using the shells of the long-lived marine bivalve Arctica islandica. Based on the shell collection locations (shelf regions offOcean City, Maryland in ~ 61 m water depth and Long Island, New York in ~47 m water depth) and shell geochemistry measurements, we will be able to better ascertain hydrographic spatial and temporal variability of subtropical Atlantic water moving northward through time. These findings will be integrated with similar sclerochronology datasets previously published from the Gulf of Maine region and several others from theMid-Atlantic region that are currently being constructed. Collectively, this network of sclerochronology records will allow us to better characterize changes in the northwestern Atlantic and provide hydrographic insights beyond the relatively short instrumental record and evaluate potential dynamical forcings through time. 

Classical turning surfaces of Kohn–Sham potentials separate classically allowed regions (CARs) from classically forbidden regions (CFRs). They are useful for understanding many chemical properties of molecules but need not exist in solids, where the density never decays to zero. At equilibrium geometries, we find that CFRs are absent in perfect metals, rare in covalent semiconductors at equilibrium, but common in ionic and molecular crystals. In all materials, CFRs appear or grow as the internuclear distances are uniformly expanded. They can also appear at a monovacancy in a metal. Calculations with several approximate density functionals and codes confirm these behaviors. A classical picture of conduction suggests that CARs should be connected in metals, and disconnected in wide-gap insulators, and is confirmed in the limits of extreme compression and expansion. Surprisingly, many semiconductors have no CFR at equilibrium, a key finding for density functional construction. Nonetheless, a strong correlation with insulating behavior can still be inferred. Moreover, equilibrium bond lengths for all cases can be estimated from the bond type and the sum of the classical turning radii of the free atoms or ions.

 

Abstract. Basic statistical metrics such as autocorrelations and across-region lagcorrelations of sea ice variations provide benchmarks for the assessments offorecast skill achieved by other methods such as more sophisticatedstatistical formulations, numerical models, and heuristic approaches. In thisstudy we use observational data to evaluate the contribution of the trend tothe skill of persistence-based statistical forecasts of monthly and seasonalice extent on the pan-Arctic and regional scales. We focus on the BeaufortSea for which the Barnett Severity Index provides a metric of historicalvariations in ice conditions over the summer shipping season. The varianceabout the trend line differs little among various methods of detrending(piecewise linear, quadratic, cubic, exponential). Application of thepiecewise linear trend calculation indicates an acceleration of the winterand summer trends during the 1990s. Persistence-based statistical forecastsof the Barnett Severity Index as well as September pan-Arctic ice extent showsignificant statistical skill out to several seasons when the data includethe trend. However, this apparent skill largely vanishes when the data aredetrended. In only a few regions does September ice extent correlatesignificantly with antecedent ice anomalies in the same region more than 2months earlier. The springtime “predictability barrier” in regionalforecasts based on persistence of ice extent anomalies is not reduced by theinclusion of several decades of pre-satellite data. No region showssignificant correlation with the detrended September pan-Arctic ice extent atlead times greater than a month or two; the concurrent correlations arestrongest with the East Siberian Sea. The Beaufort Sea's ice extent as farback as July explains about 20 % of the variance of the Barnett SeverityIndex, which is primarily a September metric. The Chukchi Sea is the onlyother region showing a significant association with the Barnett SeverityIndex, although only at a lead time of a month or two.