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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. 

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. 

Surrogate models are used to map input data to output data when the actual relationship between the two is unknown or computationally expensive to evaluate for several applications, including surface approximation and surrogate-based optimization. Many techniques have been developed for surrogate modeling; however, a systematic method for selecting suitable techniques for an application remains an open challenge. This work compares the performance of eight surrogate modeling techniques for approximating a surface over a set of simulated data. Using the comparison results, we constructed a Random Forest based tool to recommend the appropriate surrogate modeling technique for a given dataset using attributes calculated only from the available input and output values. The tool identifies the appropriate surrogate modeling techniques for surface approximation with an accuracy of 87% and a precision of 86%. Using the tool for surrogate model form selection enables computational time savings by avoiding expensive trial-and-error selection methods. 

The geosciences are one of the least diverse disciplines in the United States, despite the field's relevance to livelihoods and local and global economies. Bias, discrimination, and harassment present serious hurdles to diversifying the field. These behaviors persist due to historical structures of exclusion, severe power imbalances, unique challenges associated with geoscientist stereotypes, and a culture of impunity that tolerates exclusionary behaviors and marginalization of scholars from underserved groups. We summarize recent research on exclusionary behaviors that create hostile climates and contribute to persistent low retention of diverse groups in the geosciences and other science, technology, engineering, and mathematics (STEM) fields. We then discuss recent initiatives in the US by geoscience professional societies and organizations, including the National Science Foundation-supported ADVANCEGeo Partnership, to improve diversity, equity, and inclusion by improving workplace climate. Social networks and professional organizations can transform scientific culture through providing opportunities for mentorship and community building and counteracting professional isolation that can result from experiencing hostile behaviors, codifying ethical practice, and advocating for policy change. We conclude with a call for a reexamination of current institutional structures, processes, and practices for a transformational and equitable scientific enterprise. To be truly successful, cultural and behavioral changes need to be accompanied by reeducation about the historical political structures of academic institutions to start conversations about the real change that has to happen for a transformational and equitable scientific enterprise. 

Design and implementation of the first (asymmetric) Fe-catalyzed intra- and intermolecular difunctionalization of vinyl cyclopropanes (VCPs) with alkyl halides and aryl Grignard reagents has been realized via a mechanistically driven approach. Mechanistic studies support the diffusion of the alkyl radical intermediates out of the solvent cage to participate in an intra- or -intermolecular radical cascade with the VCP followed by re-entering the Fe radical cross-coupling cycle to undergo selective C(sp2)-C(sp3) bond formation. Overall, we provide new design principles for Fe-mediated radical processes and underscore the potential of using combined computations and experiments to accelerate the development of challenging transformations.