Adminstration

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  • Preprint
    A comparison of filtration rates among pelagic tunicates using kinematic measurements
    ( 2009-11) Sutherland, Kelly R. ; Madin, Laurence P.
    Salps have higher filtration rates than most other holoplankton, and are capable of packaging and exporting primary production from surface waters. A method of kinematic analysis was employed to accurately measure salp feeding rates. The data were then used to explain how diverse body morphologies and swimming motions among species and lifecycle stages influence salp feeding performance. We selected five species, representing a range of morphologies and swimming styles, and used digitized outlines from video frames to measure body-shape change during a pulse cycle. Time-varying body volume was then calculated from the digitized salp outlines to estimate the amount of fluid passing through the filtering mesh. This non-invasive method produced higher feeding rates than other methods and revealed that body volume, pulse frequency and degree of contraction are important factors for determining volume filtered. Each species possessed a unique combination of these three characteristics that resulted in comparable filtration (range: 0.44 - 15.33 ml s-1) and normalized filtration rates (range: 0.21 – 1.27 s-1) across species. The convergence of different species with diverse morphologies on similar normalized filtration suggests a tendency towards a flow optimum.
  • Article
    The contribution of water radiolysis to marine sedimentary life
    (Nature Research, 2021-02-26) Sauvage, Justine ; Flinders, Ashton F. ; Spivack, Arthur J. ; Pockalny, Robert ; Dunlea, Ann G. ; Anderson, Chloe H. ; Smith, David C. ; Murray, Richard W. ; D'Hondt, Steven
    Water radiolysis continuously produces H2 and oxidized chemicals in wet sediment and rock. Radiolytic H2 has been identified as the primary electron donor (food) for microorganisms in continental aquifers kilometers below Earth’s surface. Radiolytic products may also be significant for sustaining life in subseafloor sediment and subsurface environments of other planets. However, the extent to which most subsurface ecosystems rely on radiolytic products has been poorly constrained, due to incomplete understanding of radiolytic chemical yields in natural environments. Here we show that all common marine sediment types catalyse radiolytic H2 production, amplifying yields by up to 27X relative to pure water. In electron equivalents, the global rate of radiolytic H2 production in marine sediment appears to be 1-2% of the global organic flux to the seafloor. However, most organic matter is consumed at or near the seafloor, whereas radiolytic H2 is produced at all sediment depths. Comparison of radiolytic H2 consumption rates to organic oxidation rates suggests that water radiolysis is the principal source of biologically accessible energy for microbial communities in marine sediment older than a few million years. Where water permeates similarly catalytic material on other worlds, life may also be sustained by water radiolysis.
  • Article
    Deep North Atlantic last glacial maximum salinity reconstruction
    (American Geophysical Union, 2021-04-24) Homola, Kira ; Spivack, Arthur J. ; Murray, Richard W. ; Pockalny, Robert ; D'Hondt, Steven ; Robinson, Rebecca
    We reconstruct deep water-mass salinities and spatial distributions in the western North Atlantic during the Last Glacial Maximum (LGM, 19–26 ka), a period when atmospheric CO2 was significantly lower than it is today. A reversal in the LGM Atlantic meridional bottom water salinity gradient has been hypothesized for several LGM water-mass reconstructions. Such a reversal has the potential to influence climate, ocean circulation, and atmospheric CO2 by increasing the thermal energy and carbon storage capacity of the deep ocean. To test this hypothesis, we reconstructed LGM bottom water salinity based on sedimentary porewater chloride profiles in a north-south transect of piston cores collected from the deep western North Atlantic. LGM bottom water salinity in the deep western North Atlantic determined by the density-based method is 3.41–3.99 ± 0.15% higher than modern values at these sites. This increase is consistent with: (a) the 3.6% global average salinity change expected from eustatic sea level rise, (b) a northward expansion of southern sourced deep water, (c) shoaling of northern sourced deep water, and (d) a reversal of the Atlantic's north-south deep water salinity gradient during the LGM.
  • Article
    Designing the climate observing system of the future
    (John Wiley & Sons, 2018-01-23) Weatherhead, Elizabeth C. ; Wielicki, Bruce A. ; Ramaswamy, Venkatachalam ; Abbott, Mark ; Ackerman, Thomas P. ; Atlas, Robert ; Brasseur, Guy ; Bruhwiler, Lori ; Busalacchi, Antonio J. ; Butler, James H. ; Clack, Christopher T. M. ; Cooke, Roger ; Cucurull, Lidia ; Davis, Sean M. ; English, Jason M. ; Fahey, David W. ; Fine, Steven S. ; Lazo, Jeffrey K. ; Liang, Shunlin ; Loeb, Norman G. ; Rignot, Eric ; Soden, Brian ; Stanitski, Diane ; Stephens, Graeme ; Tapley, Byron D. ; Thompson, Anne M. ; Trenberth, Kevin E. ; Wuebbles, Donald
    Climate observations are needed to address a large range of important societal issues including sea level rise, droughts, floods, extreme heat events, food security, and freshwater availability in the coming decades. Past, targeted investments in specific climate questions have resulted in tremendous improvements in issues important to human health, security, and infrastructure. However, the current climate observing system was not planned in a comprehensive, focused manner required to adequately address the full range of climate needs. A potential approach to planning the observing system of the future is presented in this article. First, this article proposes that priority be given to the most critical needs as identified within the World Climate Research Program as Grand Challenges. These currently include seven important topics: melting ice and global consequences; clouds, circulation and climate sensitivity; carbon feedbacks in the climate system; understanding and predicting weather and climate extremes; water for the food baskets of the world; regional sea-level change and coastal impacts; and near-term climate prediction. For each Grand Challenge, observations are needed for long-term monitoring, process studies and forecasting capabilities. Second, objective evaluations of proposed observing systems, including satellites, ground-based and in situ observations as well as potentially new, unidentified observational approaches, can quantify the ability to address these climate priorities. And third, investments in effective climate observations will be economically important as they will offer a magnified return on investment that justifies a far greater development of observations to serve society's needs.
  • Article
    Evaluating knowledge to support climate action: A framework for sustained assessment. report of an independent advisory committee on applied climate assessment.
    (American Meteorological Society, 2019-05-21) Moss, Richard H. ; Avery, Susan K. ; Baja, Kristin ; Burkett, Maxine ; Chischilly, Ann Marie ; Dell, Janet ; Fleming, P. A. ; Geil, Kerrie L. ; Jacobs, Katharine L. ; Jones, Alan H. ; Knowlton, Kim ; Koh, Jay ; Lemos, Maria Carmen ; Melillo, Jerry M. ; Pandya, Rajul ; Richmond, Terese ; Scarlett, Lynn ; Snyder, Jared ; Stults, Melissa ; Waple, Anne ; Whitehead, Jessica ; Zarrilli, Daniel ; Ayyub, Bilal M. ; Fox, James ; Ganguly, Auroop ; Joppa, Lucas ; Julius, Susan ; Kirshen, Paul ; Kreutter, Rebecca ; McGovern, Amy ; Meyer, Ryan ; Neumann, James ; Solecki, William ; Smith, Joel ; Tissot, Philippe ; Yohe, Gary ; Zimmerman, Rae
    As states, cities, tribes, and private interests cope with climate damages and seek to increase preparedness and resilience, they will need to navigate myriad choices and options available to them. Making these choices in ways that identify pathways for climate action that support their development objectives will require constructive public dialogue, community participation, and flexible and ongoing access to science- and experience-based knowledge. In 2016, a Federal Advisory Committee (FAC) was convened to recommend how to conduct a sustained National Climate Assessment (NCA) to increase the relevance and usability of assessments for informing action. The FAC was disbanded in 2017, but members and additional experts reconvened to complete the report that is presented here. A key recommendation is establishing a new nonfederal “climate assessment consortium” to increase the role of state/local/tribal government and civil society in assessments. The expanded process would 1) focus on applied problems faced by practitioners, 2) organize sustained partnerships for collaborative learning across similar projects and case studies to identify effective tested practices, and 3) assess and improve knowledge-based methods for project implementation. Specific recommendations include evaluating climate models and data using user-defined metrics; improving benefit–cost assessment and supporting decision-making under uncertainty; and accelerating application of tools and methods such as citizen science, artificial intelligence, indicators, and geospatial analysis. The recommendations are the result of broad consultation and present an ambitious agenda for federal agencies, state/local/tribal jurisdictions, universities and the research sector, professional associations, nongovernmental and community-based organizations, and private-sector firms.
  • Preprint
    Filtration of submicrometer particles by pelagic tunicates
    ( 2010-07) Sutherland, Kelly R. ; Madin, Laurence P. ; Stocker, Roman
    Salps are common in oceanic waters and have higher per individual filtration rates than any other zooplankton filter feeder. Though salps are centimeters in length, feeding via particle capture occurs on a fine, mucous mesh (fiber diameter d ~ 0.1 μm) at low velocity (U = 1.6 ± 0.6 cm s-1, mean ± SD) and is thus a low-Reynolds number (Re ~ 10-3) process. In contrast to the current view that particle encounter is dictated by simple sieving of particles larger than the mesh spacing, a low-Re mathematical model of encounter rates by the salp feeding apparatus for realistic oceanic particle size distributions shows that submicron particles, due to their higher abundances, are encountered at higher rates (particles per time) than larger particles. Data from feeding experiments with 0.5, 1 and 3 μm diameter polystyrene spheres corroborate these results. Though particles larger than 1 μm (e.g. flagellates, small diatoms) represent a larger carbon pool, smaller particles in the 0.1–1 μm range (e.g. bacteria, Prochlorococcus) may be more quickly digestible because they present more surface area, and we find that particles smaller than the mesh size (1.4 μm) can fully satisfy salp energetic needs. Furthermore, by packaging submicrometer particles into rapidly sinking fecal pellets, pelagic tunicates can substantially change particle size spectra and increase downward fluxes in the ocean.
  • Preprint
    Global Ocean Summit : a forum for institutional coordination of global ocean observations
    ( 2014-11) Cai, Wenju ; Avery, Susan K. ; Leinen, Margaret S. ; Lee, Kenneth ; Lin, Xiaopei ; Visbeck, Martin
    A sustainable global ocean observation system requires timely implementation of a global ocean observation framework. The recent Qingdao Global Ocean Summit offers an effective mechanism for a coherent institutional response to emerging scientific and societal drivers, and for promoting the capacity building in developing economies that is essential for increasing the value and broadening the funding base of the observation system.
  • Article
    Gravity wave characteristics in the mesopause region revealed from OH airglow imager observations over Northern Colorado
    (John Wiley & Sons, 2014-01-31) Tang, Yihuan ; Dou, Xiankang ; Li, Tao ; Nakamura, Takuji ; Xue, Xianghui ; Huang, Can ; Manson, Alan ; Meek, Chris ; Thorsen, Denise ; Avery, Susan K.
    Using 5 years of all-sky OH airglow imager data over Yucca Ridge Field Station, CO (40.7°N, 104.9°W), from September 2003 to September 2008, we extract and deduce quasi-monochromatic gravity wave (GW) characteristics in the mesopause region. The intrinsic periods are clustered between approximately 4 and 10 min, and many of them are unstable and evanescent. GW occurrence frequency exhibits a clear semiannual variation with equinoctial minima, which is likely related to the seasonal variation of background wind. The anomalous propagation direction in January 2006, with strong southward before major warming starting in 21 January and weak southward propagation afterward, was most likely affected by stratospheric sudden warming. The momentum fluxes show strongly anticorrelated with the tides, with ~180° out of phase in the zonal component. While in the meridional component, the easterly maximum occurred approximately 2–6 h after maximum easterly tidal wind. However, the anticorrelations are both weakest during the summer. The dissipating and breaking of small-scale and high-frequency GW's components could have a potential impact on the general circulation in the mesopause region.
  • Article
    Holocene bidirectional river system along the Kenya Rift and its influence on East African faunal exchange and diversity gradients
    (National Academy of Sciences, 2022-07-12) Dommain, René ; Riedl, Simon ; Olaka, Lydia A. ; de Menocal, Peter B. ; Deino, Alan L. ; Owen, R. Bernhart ; Muiruri, Veronica ; Müller, Johannes ; Potts, Richard ; Strecker, Manfred R.
    East Africa is a global biodiversity hotspot and exhibits distinct longitudinal diversity gradients from west to east in freshwater fishes and forest mammals. The assembly of this exceptional biodiversity and the drivers behind diversity gradients remain poorly understood, with diversification often studied at local scales and less attention paid to biotic exchange between Afrotropical regions. Here, we reconstruct a river system that existed for several millennia along the now semiarid Kenya Rift Valley during the humid early Holocene and show how this river system influenced postglacial dispersal of fishes and mammals due to its dual role as a dispersal corridor and barrier. Using geomorphological, geochronological, isotopic, and fossil analyses and a synthesis of radiocarbon dates, we find that the overflow of Kenyan rift lakes between 12 and 8 ka before present formed a bidirectional river system consisting of a “Northern River” connected to the Nile Basin and a “Southern River,” a closed basin. The drainage divide between these rivers represented the only viable terrestrial dispersal corridor across the rift. The degree and duration of past hydrological connectivity between adjacent river basins determined spatial diversity gradients for East African fishes. Our reconstruction explains the isolated distribution of Nilotic fish species in modern Kenyan rift lakes, Guineo-Congolian mammal species in forests east of the Kenya Rift, and recent incipient vertebrate speciation and local endemism in this region. Climate-driven rearrangements of drainage networks unrelated to tectonic activity contributed significantly to the assembly of species diversity and modern faunas in the East African biodiversity hotspot.
  • Article
    How the oceanographic community created a National Oceanographic Partnership Program
    (Oceanography Society, 2009-06) Watkins, James D. ; Schaff, Terrence R. ; Spinrad, Richard W.
    On this tenth anniversary of the National Oceanographic Partnership Program, and as our nation embarks on a broad set of critical societal initiatives, it is valuable to review the accomplishments of the program, and reflect on conceptual origins of the ocean partnership idea and the process by which the program was conceived and established.
  • Article
    Hydroclimate variability in the equatorial western Indian Ocean for the last 250,000 years
    (American Geophysical Union, 2023-01-21) Windler, Grace ; Tierney, Jessica E. ; deMenocal, Peter B.
    Abstract Indian Ocean sea surface temperatures impact precipitation across the basin through coupled ocean-atmosphere responses to changes in climate. To understand the hydroclimate response over the western Indian Ocean and equatorial east Africa to different forcing mechanisms, we present four new proxy reconstructions from core VM19-193 (2.98°N, 51.47°E) that span the last 250 ky. Sub-surface water temperatures (Sub-T; TEX86) show strong precessional (23 ky) variability that is primarily influenced by maximum incoming solar radiation (insolation) during the Northern Hemisphere spring season, likely indicating that local insolation dominates the upper water column at this tropical location over time. Leaf waxes, on the other hand, reflect two different precipitation signals: δ13Cwax (in phase with boreal fall insolation) is likely reflecting vegetation changes in response to local rainfall over east Africa, whereas δDprecip (primarily driven by boreal summer insolation) represents changes in regional circulation associated with the summer monsoon. Glacial-interglacial changes in ocean temperatures support glacial shelf exposure over the Maritime Continent in the eastern Indian Ocean and the subsequent weakening of the Indian Walker Circulation as a mechanism driving 100 ky climate variability across the tropical Indo-Pacific. Additionally, the 100 ky spectral power in δDprecip supports a basin-wide weakening of summer monsoon circulation in response to glacial climates. Overall, the proxy records from VM19-193 indicate that both precession and glacial-interglacial cycles exert control over hydroclimate at this tropical location.
  • Preprint
    Impact of phytoplankton community size on a linked global ocean optical and ecosystem model
    ( 2011-01) Mouw, Colleen B. ; Yoder, James A. ; Doney, Scott C.
    We isolated the effect phytoplankton cell size has on varying remote sensing reflectance spectra (Rrs(λ)) in the presence of optically active constituents by using optical and radiative transfer models linked in an offline diagnostic calculation to a global biogeochemical/ecosystem/circulation model with explicit phytoplankton size classes. Two case studies were carried out, each with several scenarios to isolate the effects of chlorophyll concentration, phytoplankton cell size, and size-varying phytoplankton absorption on Rrs(λ). The goal of the study was to determine the relative contribution of phytoplankton cell size and chlorophyll to overall Rrs(λ) and to understand where a standard band ratio algorithm (OC4) may under/overestimate chlorophyll due to Rrs(λ) being significantly affected by phytoplankton size. Phytoplankton cell size was found to contribute secondarily to Rrs(λ) variability and to amplify or dampen the seasonal cycle in Rrs(λ), driven by chlorophyll. Size and chlorophyll were found to change in phase at low to mid-latitudes, but were anti-correlated or poorly correlated at high latitudes. Phytoplankton size effects increased model calculated Rrs(443) in the subtropical ocean during local spring through early fall months in both hemispheres and decreased Rrs(443) in the Northern Hemisphere high latitude regions during local summer to fall months. This study attempts to tease apart when/where variability about the OC4 relationship may be associated with cell size variability. The OC4 algorithm may underestimate [Chl] when the fraction of microplankton is elevated, which occurs in the model simulations during local spring/summer months at high latitudes in both hemispheres.
  • Working Paper
    Improving communication of climate change science to public audiences : early career ocean scientists and science interpreters engage with social scientists
    ( 2018-03-27) Yoder, James
    This manuscript describes a qualitative study based on the results of interviews with early career scientists (graduate students and postdocs) who participated as “science fellows” along with science interpreters for training led by social scientists as to how to discuss ocean and climate change issues with general audiences. Based on the interviews, the science fellows were generally enthusiastic and effective participants in the program, and the training gave them more confidence for discussing the effects of climate change on the ocean. In addition, and of equal importance, the science fellows generally believed that the training helped them organize their written and oral presentations of their own science for their professional colleagues and is a lasting benefit to their career development.
  • Article
    Is global ocean sprawl a cause of jellyfish blooms?
    (Ecological Society of America, 2012-09-07) Duarte, Carlos M. ; Pitt, Kylie A. ; Lucas, Cathy H. ; Purcell, Jennifer E. ; Uye, Shin-Ichi ; Robinson, Kelly L. ; Brotz, Lucas ; Decker, Mary Beth ; Sutherland, Kelly R. ; Malej, Alenka ; Madin, Laurence P. ; Mianzan, Hermes ; Gili, Josep-Maria ; Fuentes, Veronica ; Atienza, Dacha ; Pages, Francesc ; Breitburg, Denise L. ; Malek, Jennafer ; Graham, William M. ; Condon, Robert H.
    Jellyfish (Cnidaria, Scyphozoa) blooms appear to be increasing in both intensity and frequency in many coastal areas worldwide, due to multiple hypothesized anthropogenic stressors. Here, we propose that the proliferation of artificial structures – associated with (1) the exponential growth in shipping, aquaculture, and other coastal industries, and (2) coastal protection (collectively, “ocean sprawl”) – provides habitat for jellyfish polyps and may be an important driver of the global increase in jellyfish blooms. However, the habitat of the benthic polyps that commonly result in coastal jellyfish blooms has remained elusive, limiting our understanding of the drivers of these blooms. Support for the hypothesized role of ocean sprawl in promoting jellyfish blooms is provided by observations and experimental evidence demonstrating that jellyfish larvae settle in large numbers on artificial structures in coastal waters and develop into dense concentrations of jellyfish-producing polyps.
  • Article
    Land and deep-sea mining: the challenges of comparing biodiversity impacts
    (Springer, 2023-03-18) Katona, Steven ; Paulikas, Daina ; Ali, Saleem ; Clarke, Michael ; Ilves, Erika ; Lovejoy, Thomas E. ; Madin, Laurence P. ; Stone, Gregory S.
    The term ‘biodiversity,’ while casually used in practice, is a complicated subject to measure, interpret, contextualize, and compare. Yet the possible advent of deep-sea mining in the mid-2020’s compels us to compare potential impacts of biodiversity loss across ecologically distant realms, a formidable task. Supplying the world’s green infrastructure is expected to lead to shortages of nickel, cobalt and other metals; meanwhile polymetallic nodules sitting atop the abyssal plains of the Clarion-Clipperton Zone (CCZ) of the Pacific Ocean contain billions of tons of nickel, cobalt, copper and manganese, enough to solve the supply issues. Implicit in society’s decision of whether to exploit this resource is a tradeoff of harm to biodiversity in the CCZ’s abyssal seafloor and its overlying water column, versus intensification of harm to rainforests and other terrestrial mining habitats. Here we frame the challenges of comparing biodiversity impacts across such different realms, spanning the gamut from normative to fundamental: ambiguities in definitions, lack of protocol standardization, physical challenges in measurement, difficulties to integrate measures among different taxonomic groups, profound differences between ecologically distant realms, contextual necessity to attribute value to mathematical index results, and constraints of current knowledge about species, ecosystems and system level impacts of biodiversity change. Quantitative biodiversity measures alone cannot rank one system above the other; measures must be supplemented with qualitative judgements of the tangible and intangible values of species and habitats to natural systems and to humans, along with consideration of other threats that they and we face.
  • Article
    Linking human well-being and jellyfish : ecosystem services, impacts, and societal responses
    (Ecological Society of America, 2014-11) Graham, William M. ; Gelcich, Stefan ; Robinson, Kelly L. ; Duarte, Carlos M. ; Brotz, Lucas ; Purcell, Jennifer E. ; Madin, Laurence P. ; Mianzan, Hermes ; Sutherland, Kelly R. ; Uye, Shin-Ichi ; Pitt, Kylie A. ; Lucas, Cathy H. ; Bogeberg, Molly ; Brodeur, Richard D. ; Condon, Robert H.
    Jellyfish are usually perceived as harmful to humans and are seen as “pests”. This negative perception has hindered knowledge regarding their value in terms of ecosystem services. As humans increasingly modify and interact with coastal ecosystems, it is important to evaluate the benefits and costs of jellyfish, given that jellyfish bloom size, frequency, duration, and extent are apparently increasing in some regions of the world. Here we explore those benefits and costs as categorized by regulating, supporting, cultural, and provisioning ecosystem services. A geographical perspective of human vulnerability to jellyfish over four categories of human well-being (health care, food, energy, and freshwater production) is also discussed in the context of thresholds and trade-offs to enable social adaptation. Whereas beneficial services provided by jellyfish likely scale linearly with biomass (perhaps peaking at a saturation point), non-linear thresholds exist for negative impacts to ecosystem services. We suggest that costly adaptive strategies will outpace the beneficial services if jellyfish populations continue to increase in the future.
  • Article
    Low-frequency orbital variations controlled climatic and environmental cycles, amplitudes, and trends in northeast Africa during the Plio-Pleistocene
    (Nature Research, 2023-10-09) Lupien, Rachel ; Uno, Kevin ; Rose, Cassaundra ; deRoberts, Nicole ; Hazan, Cole ; deMenocal, Peter B. ; Polissar, Pratigya J.
    The eastern Mediterranean sapropels, paced by insolation, provide a unique archive of African monsoon strength over the Late Neogene. However, the longer-term climate of this region lacks characterization within the context of changes in ice volume, sea surface temperature gradients, and terrestrial ecosystems. Here, we examine C28 n-alkanoic acid leaf wax hydrogen and carbon isotopes in sapropels, sourced from northeast Africa, along with vegetation-corrected precipitation isotopes, derived from astronomically dated sediment cores from ODP 160 Sites 966 and 967 since 4.5 million years ago. Despite sampling only wet-phase sapropels for African monsoon variability, we find a larger range in hydrogen isotopes than previously published data across wet-dry precession cycles, indicating the importance of long-term modulation of Green Sahara phases throughout the Neogene. An influence of orbital properties on regional monsoonal hydroclimate is observed, controlling up to 50% of total hydrogen isotope variance, but large changes outside of these typical frequencies account for at least 50% of the total variance. This secular trend may track changes in ice volume, tropical sea surface temperature, sea surface temperature gradients, or even lower-frequency orbital cycles. Long-term hydroclimate and environmental shifts provide new contexts for milestone events in northeast African hominin dispersal and evolution.
  • Article
    Marine sedimentary records of chemical weathering evolution in the western Himalaya since 17 Ma
    (Geological Society of America, 2021-03-24) Zhou, Peng ; Ireland, Thomas ; Murray, Richard W. ; Clift, Peter D.
    The Indus Fan derives sediment from the western Himalaya and Karakoram. Sediment from International Ocean Discovery Program drill sites in the eastern part of the fan coupled with data from an industrial well near the river mouth allow the weathering history of the region since ca. 16 Ma to be reconstructed. Clay minerals, bulk sediment geochemistry, and magnetic susceptibility were used to constrain degrees of chemical alteration. Diffuse reflectance spectroscopy was used to measure the abundance of moisture-sensitive minerals hematite and goethite. Indus Fan sediment is more weathered than Bengal Fan material, probably reflecting slow transport, despite the drier climate, which slows chemical weathering rates. Some chemical weathering proxies, such as K/Si or kaolinite/(illite + chlorite), show no temporal evolution, but illite crystallinity and the chemical index of alteration do have statistically measurable decreases over long time periods. Using these proxies, we suggest that sediment alteration was moderate and then increased from 13 to 11 Ma, remained high until 9 Ma, and then reduced from that time until 6 Ma in the context of reduced physical erosion during a time of increasing aridity as tracked by hematite/goethite values. The poorly defined reducing trend in weathering intensity is not clearly linked to global cooling and at least partly reflects regional climate change. Since 6 Ma, weathering has been weak but variable since a final reduction in alteration state after 3.5 Ma that correlates with the onset of Northern Hemispheric glaciation. Reduced or stable chemical weathering at a time of falling sedimentation rates is not consistent with models for Cenozoic global climate change that invoke greater Himalayan weathering fluxes drawing down atmospheric CO2 but are in accord with the idea of greater surface reactivity to weathering.
  • Working Paper
    A modern coastal ocean observing system using data from advanced satellite and in situ sensors – an example
    (NSF/Ocean Research Coordination Network, 2015-06-01) Yoder, James A. ; Davis, Curtiss O. ; Dierssen, Heidi M. ; Muller-Karger, Frank E. ; Mahadevan, Amala ; Pearlman, Jay ; Sosik, Heidi M.
    This report is intended to illustrate and provide recommendations for how ocean observing systems of the next decade could focus on coastal environments using combined satellite and in situ measurements. Until recently, space-based observations have had surface footprints typically spanning hundreds of meters to kilometers. These provide excellent synoptic views for a wide variety of ocean characteristics. In situ observations are instead generally point or linear measurements. The interrelation between space-based and in-situ observations can be challenging. Both are necessary and as sensors and platforms evolve during the next decade, the trend to facilitate interfacing space and in-situ observations must continue and be expanded. In this report, we use coastal observation and analyses to illustrate an observing system concept that combines in situ and satellite observing technologies with numerical models to quantify subseasonal time scale transport of freshwater and its constituents from terrestrial water storage bodies across and along continental shelves, as well as the impacts on some key biological/biogeochemical properties of coastal waters.
  • Article
    A moving target : matching graduate education with available careers for ocean scientists
    (The Oceanography Society, 2016-03) Briscoe, Melbourne G. ; Glickson, Deborah A. ; Roberts, Susan ; Spinrad, Richard W. ; Yoder, James A.
    The objective of this paper is to look at past assessments and available data to examine the match (or mismatch) between university curricula and programs available to graduate students in the ocean sciences and the career possibilities available to those students. We conclude there is a need for fundamental change in how we educate graduate students in the ocean sciences. The change should accommodate the interests of students as well as the needs of a changing society; the change should not be constrained by the traditions or resource challenges of the graduate institutions themselves. The limited data we have been able to obtain from schools and employers are consistent with this view: desirable careers for ocean scientists are moving rapidly toward interdisciplinary, collaborative, societally relevant activities, away from traditional academic-research/professorial jobs, but the training available to the students is not keeping pace. We offer some suggestions to mitigate the mismatch. Most importantly, although anecdotes and “gut feelings” abound, the quantitative data backing our conclusions and suggestions are very sparse and barely compelling; we urge better data collection to support curricular revision, perhaps with the involvement of professional societies.