Topics and trends in NSF ocean sciences awards

Author Posting. © The Oceanography Society, 2018. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Topics and trends in NSF ocean sciences awards. Oceanography 31(4), (2018): 164-170. doi:10.5670/oceanog.2018.404.The National Science Foundation Ocean Sciences Division (NSF-OCE) provides the majority of the support for ocean research in the United States. Knowledge of the trends in research and funding for NSF-OCE awards is important to investigators, academic institutions, policy analysts, and advocacy organizations. Here, we apply topic modeling to NSF-OCE award abstracts to uncover underlying research topics, examine the interrelationships between awards, and identify research and funding trends. The 20 topics identified by the model capture NSF-OCE’s 10 largest programs (~90% of awards) remarkably well and provide better resolution into research subjects. The distribution of awards in topic space shows how the different topics relate to each other based on their similarity and how awards transition from one topic to another. Awards have become more interdisciplinary over time, with increasing trends in 13 of the 20 topics (65%). Seven topics show a growing fraction of the number of awards while six topics have a declining share. Both the annual inflation-adjusted amount of money awarded and the fraction of the annual funding have been increasing over time in four of the 20 topics. Three other topics show a decline in both the annual amount awarded and the fraction of total annual funding. The identified topics can be grouped into three major themes: infrastructure, education, and science. After 2011, increases in the mean annual cost per project result in a relatively constant fraction of annual funding for infrastructure, despite a significant decline in the infrastructure fraction of awards. The information presented on research and funding trends is useful to scientists and academic institutions in planning and decision-making, while the metrics we employed can be used by NSF to quantify the effects of policy decisions.We thank T. Horner, B. Peucker-Ehrenbrink, K. Buesseler and M. Kurz for discussions and comments, the Woods Hole Oceanographic Institution Department of Marine Chemistry and Geochemistry for support, and A. Mix and three anonymous reviewers for their comments and suggestions. NSF deserves special credit for making its data publicly available

Gender differences in NSF ocean sciences awards

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lima, I.D., Rheuban, J.E. Gender differences in NSF ocean sciences awards. Oceanography 34(4), (2021), https://doi.org/10.5670/oceanog.2021.401.In this study, we examine how women’s representation in National Science Foundation Ocean Sciences (NSF-OCE) awards changed between 1987 and 2019 and how it varied across different programs, research topics, and award types. Women’s participation in NSF-OCE awards increased at a rate of approximately 0.6% per year from about 10% in 1987 to 30% in 2019, and the strong similarity between the temporal trends in the NSF-OCE awards and the academic workforce suggests that there was no gender bias in NSF funding throughout the 33-year study period. The programs, topics, and award types related to education showed the strongest growth, achieving and surpassing parity with men, while those related to the acquisition of shared instrumentation and equipment for research vessels had the lowest women’s representation and showed relatively little change over time. Despite being vastly outnumbered by men, women principal investigators (PIs) tended to do more collaborative work and had a more diversified “portfolio” of research and research-related activities than men. We also found no evidence of gender bias in the amount awarded to men and women PIs during the study period. These results show that, despite significant increases in women’s participation in oceanography over the past three decades, women have still not reached parity with men. Although there appears to be no gender bias in funding decisions or amount awarded, there are significant differences between women’s participation in specific research subject areas that may reflect overall systemic biases in oceanography and academia more broadly. These results highlight areas where further investment is needed to improve women’s representation

A three-dimensional, multinutrient, and size-structured ecosystem model for the North Atlantic

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 18 (2004): GB3019, doi:10.1029/2003GB002146.We incorporate multinutrient and size-structured ecosystem dynamics into a three-dimensional ocean general circulation model for the North Atlantic. The model reproduces the magnitude and general spatial and temporal patterns in nutrients, chlorophyll and primary production seen in in situ (BATS, NABE, and OWSI) and satellite (SeaWiFS) data, showing substantial improvements over prior basin-scale simulations. Model skill is evaluated quantitatively against SeaWiFS data using a Taylor diagram approach. Model-data correlation R for the overall surface chlorophyll time-space distribution is ∼0.6, with comparable model and observed total variability. The agreement relative to satellite-based primary production is somewhat weaker (0.2 < R < 0.5). The simulations capture observed ecological characteristics, e.g., the dominance of picoplankton and episodic diatom blooms in the subtropics, nutrient-controlled plankton succession at higher latitudes, and associated seasonal/depth changes in new and regenerated production and particle export. In a sensitivity experiment that mimics behavior of simpler single-species models, removal of diatom silica limitation leads to major shifts in community structure and export and larger model-data errors similar to previous model studies. Model results also suggest that episodic diatom blooms at BATS may be related to interannual variations in the southward transport of nutrients, mainly SiO3, and plankton cells.Support for this work was provided by NASA SeaWiFS grant W-19,223 and NSF JGOFS SMP grant 0222033

Response of ocean phytoplankton community structure to climate change over the 21st century : partitioning the effects of nutrients, temperature and light

© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 7 (2010): 3941-3959, doi:10.5194/bg-7-3941-2010.The response of ocean phytoplankton community structure to climate change depends, among other factors, upon species competition for nutrients and light, as well as the increase in surface ocean temperature. We propose an analytical framework linking changes in nutrients, temperature and light with changes in phytoplankton growth rates, and we assess our theoretical considerations against model projections (1980–2100) from a global Earth System model. Our proposed "critical nutrient hypothesis" stipulates the existence of a critical nutrient threshold below (above) which a nutrient change will affect small phytoplankton biomass more (less) than diatom biomass, i.e. the phytoplankton with lower half-saturation coefficient K are influenced more strongly in low nutrient environments. This nutrient threshold broadly corresponds to 45° S and 45° N, poleward of which high vertical mixing and inefficient biology maintain higher surface nutrient concentrations and equatorward of which reduced vertical mixing and more efficient biology maintain lower surface nutrients. In the 45° S–45° N low nutrient region, decreases in limiting nutrients – associated with increased stratification under climate change – are predicted analytically to decrease more strongly the specific growth of small phytoplankton than the growth of diatoms. In high latitudes, the impact of nutrient decrease on phytoplankton biomass is more significant for diatoms than small phytoplankton, and contributes to diatom declines in the northern marginal sea ice and subpolar biomes. In the context of our model, climate driven increases in surface temperature and changes in light are predicted to have a stronger impact on small phytoplankton than on diatom biomass in all ocean domains. Our analytical predictions explain reasonably well the shifts in community structure under a modeled climate-warming scenario. Climate driven changes in nutrients, temperature and light have regionally varying and sometimes counterbalancing impacts on phytoplankton biomass and structure, with nutrients and temperature dominant in the 45° S–45° N band and light-temperature effects dominant in the marginal sea-ice and subpolar regions. As predicted, decreases in nutrients inside the 45° S–45° N "critical nutrient" band result in diatom biomass decreasing more than small phytoplankton biomass. Further stratification from global warming could result in geographical shifts in the "critical nutrient" threshold and additional changes in ecology.While at WHOI, I. Marinov was supported by National Science Foundation (NSF) Grant ATM06-28582. I. Lima and S. Doney were supported by the Center for Microbial Oceanography, Research, and Education (CMORE) an NSF Science and Technology Center (EF-0424599)

Dynamics of particulate organic carbon flux in a global ocean model

© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 11 (2014): 1177-1198, doi:10.5194/bg-11-1177-2014.The sinking of particulate organic carbon (POC) is a key component of the ocean carbon cycle and plays an important role in the global climate system. However, the processes controlling the fraction of primary production that is exported from the euphotic zone (export ratio) and how much of it survives respiration in the mesopelagic to be sequestered in the deep ocean (transfer efficiency) are not well understood. In this study, we use a three-dimensional, coupled physical–biogeochemical model (CCSM–BEC; Community Climate System Model–ocean Biogeochemical Elemental Cycle) to investigate the processes controlling the export of particulate organic matter from the euphotic zone and its flux to depth. We also compare model results with sediment trap data and other parameterizations of POC flux to depth to evaluate model skill and gain further insight into the causes of error and uncertainty in POC flux estimates. In the model, export ratios are mainly a function of diatom relative abundance and temperature while absolute fluxes and transfer efficiency are driven by mineral ballast composition of sinking material. The temperature dependence of the POC remineralization length scale is modulated by denitrification under low O2 concentrations and lithogenic (dust) fluxes. Lithogenic material is an important control of transfer efficiency in the model, but its effect is restricted to regions of strong atmospheric dust deposition. In the remaining regions, CaCO3 content of exported material is the main factor affecting transfer efficiency. The fact that mineral ballast composition is inextricably linked to plankton community structure results in correlations between export ratios and ballast minerals fluxes (opal and CaCO3), and transfer efficiency and diatom relative abundance that do not necessarily reflect ballast or direct ecosystem effects, respectively. This suggests that it might be difficult to differentiate between ecosystem and ballast effects in observations. The model's skill in reproducing sediment trap observations is equal to or better than that of other parameterizations. However, the sparseness and relatively large uncertainties of sediment trap data makes it difficult to accurately evaluate the skill of the model and other parameterizations. More POC flux observations, over a wider range of ecological regimes, are necessary to thoroughly evaluate and test model results and better understand the processes controlling POC flux to depth in the ocean.Support for this work was provided by WHOI Ocean and Climate Change Institute and NSF grants OCE-0960880 and AGS-1048827

Impact of variable air-sea O2 and CO2 fluxes on atmospheric potential oxygen (APO) and land-ocean carbon sink partitioning

© 2008 Author(s). This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 5 (2008): 875-899, doi:10.5194/bg-5-875-2008A three dimensional, time-evolving field of atmospheric potential oxygen (APO ~O2/N2+CO2) was estimated using surface O2, N2 and CO2 fluxes from the WHOI ocean ecosystem model to force the MATCH atmospheric transport model. Land and fossil carbon fluxes were also run in MATCH and translated into O2 tracers using assumed O2:CO2 stoichiometries. The modeled seasonal cycles in APO agree well with the observed cycles at 13 global monitoring stations, with agreement helped by including oceanic CO2 in the APO calculation. The modeled latitudinal gradient in APO is strongly influenced by seasonal rectifier effects in atmospheric transport. An analysis of the APO-vs.-CO2 mass-balance method for partitioning land and ocean carbon sinks was performed in the controlled context of the MATCH simulation, in which the true surface carbon and oxygen fluxes were known exactly. This analysis suggests uncertainty of up to ±0.2 PgC in the inferred sinks due to variability associated with sparse atmospheric sampling. It also shows that interannual variability in oceanic O2 fluxes can cause large errors in the sink partitioning when the method is applied over short timescales. However, when decadal or longer averages are used, the variability in the oceanic O2 flux is relatively small, allowing carbon sinks to be partitioned to within a standard deviation of 0.1 Pg C/yr of the true values, provided one has an accurate estimate of long-term mean O2 outgassing.We acknowledge the support of NASA grant NNG05GG30G and NSF grant ATM0628472

Reply to a comment by Stephen M. Chiswell on: “Annual cycles of ecological disturbance and recovery underlying the subarctic Atlantic spring plankton bloom” by M. J. Behrenfeld et al. (2013)

Author Posting. © American Geophysical Union, [year]. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 27 (2013): 1294–1296, doi:10.1002/2013GB004720.2014-06-1

Annual cycles of ecological disturbance and recovery underlying the subarctic Atlantic spring plankton bloom

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 27 (2013): 526–540, doi:10.1002/gbc.20050.Satellite measurements allow global assessments of phytoplankton concentrations and, from observed temporal changes in biomass, direct access to net biomass accumulation rates (r). For the subarctic Atlantic basin, analysis of annual cycles in r reveals that initiation of the annual blooming phase does not occur in spring after stratification surpasses a critical threshold but rather occurs in early winter when growth conditions for phytoplankton are deteriorating. This finding has been confirmed with in situ profiling float data. The objective of the current study was to test whether satellite-based annual cycles in r are reproduced by the Biogeochemical Element Cycling–Community Climate System Model and, if so, to use the additional ecosystem properties resolved by the model to better understand factors controlling phytoplankton blooms. We find that the model gives a similar early onset time for the blooming phase, that this initiation is largely due to the physical disruption of phytoplankton-grazer interactions during mixed layer deepening, and that parallel increases in phytoplankton-specific division and loss rates during spring maintain the subtle disruption in food web equilibrium that ultimately yields the spring bloom climax. The link between winter mixing and bloom dynamics is illustrated by contrasting annual plankton cycles between regions with deeper and shallower mixing. We show that maximum water column inventories of phytoplankton vary in proportion to maximum winter mixing depth, implying that future reductions in winter mixing may dampen plankton cycles in the subarctic Atlantic. We propose that ecosystem disturbance-recovery sequences are a unifying property of global ocean plankton blooms.This work was supported by the National Aeronautics and Space Administration, Ocean Biology and Biogeochemistry Program (grants NNX10AT70G, NNX09AK30G, NNX08AK70G, NNX07AL80G, and NNX08AP36A) and the Center for Microbial Oceanography Research and Education (C-MORE; grant EF-0424599), a National Science Foundation-supported Science and Technology Center

Data-based assessment of environmental controls on global marine nitrogen fixation

© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 11 (2014): 691-708, doi:10.5194/bg-11-691-2014.There are a number of hypotheses concerning the environmental controls on marine nitrogen fixation (NF). Most of these hypotheses have not been assessed against direct measurements on the global scale. In this study, we use ~ 500 depth-integrated field measurements of NF covering the Pacific and Atlantic oceans to test whether the spatial variance of these measurements can be explained by the commonly hypothesized environmental controls, including measurement-based surface solar radiation, mixed layer depth, average solar radiation in the mixed layer, sea surface temperature, wind speed, surface nitrate and phosphate concentrations, surface excess phosphate (P*) concentration and subsurface minimum dissolved oxygen (in upper 500 m), as well as model-based P* convergence and atmospheric dust deposition. By conducting simple linear regression and stepwise multiple linear regression (MLR) analyses, surface solar radiation (or sea surface temperature) and subsurface minimum dissolved oxygen are identified as the predictors that explain the most spatial variance in the observed NF data, although it is unclear why the observed NF decreases when the level of subsurface minimum dissolved oxygen is higher than ~ 150 μM. Dust deposition and wind speed do not appear to influence the spatial patterns of NF on global scale. The weak correlation between the observed NF and the P* convergence and concentrations suggests that the available data currently remain insufficient to fully support the hypothesis that spatial variability in denitrification is the principal control on spatial variability in marine NF. By applying the MLR-derived equation, we estimate the global-integrated NF at 74 (error range 51–110) Tg N yr−1 in the open ocean, acknowledging that it could be substantially higher as the 15N2-assimilation method used by most of the field samples underestimates NF. More field NF samples in the Pacific and Indian oceans, particularly in the oxygen minimum zones, are needed to reduce uncertainties in our conclusion.This project was supported by the NSF Center for Microbial Oceanography: Research and Education (C-MORE) (EF-0424599), an NSF Emerging Topics in Biogeochemical Cycles grant (ETBC, AGS-1020594), and the Gordon and Betty Moore Foundation

Modeling deep ocean shipping noise in varying acidity conditions

Author Posting. © Acoustical Society of America, 2010. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 128 (2010): EL130–EL136, doi:10.1121/1.3402284.Possible future changes of ambient shipping noise at 0.1–1 kHz in the North Pacific caused by changing seawater chemistry conditions are analyzed with a simplified propagation model. Probable decreases of pH would cause meaningful reduction of the sound absorption coefficient in near-surface ocean water for these frequencies. The results show that a few decibels of increase may occur in 100 years in some very quiet areas very far from noise sources, with small effects closer to noise sources. The use of ray physics allows sound energy attenuated via volume absorption and by the seafloor to be compared.This work was supported by the Ocean Acoustics Program at the U.S. Office of Naval Research, Code 321, including an ONR Postdoctoral Fellowship award to the first author