The role of heterotrophic bacteria in iron-limited ocean ecosystems

NASA Astrophysics Data System (ADS)

Tortell, Philippe D.; Maldonado, Maria T.; Price, Nell M.

1996-09-01

IRON availability limits phytoplankton growth in large areas of the world's oceans1-3 and may influence the strength of the biological carbon pump4,5. Very little is known of the iron requirements of oceanic heterotrophic bacteria, which constitute up to 50% of the total particulate organic carbon in open ocean waters6,7 and are important in carbon cycling as remineralizers of dissolved organic matter and hence producers of CO2 (ref. 8). Here we report that oceanic bacteria contain more iron per biomass than phytoplankton. In the subarctic Pacific, they constitute a large fraction of biogenic iron and account for 20-45% of biological iron uptake. Bacterial iron quotas in the field are similar to those of iron-deficient laboratory cultures, which exhibit reduced elec-tron transport, slow growth, and low carbon growth efficiency. Heterotrophic bacteria therefore play a major role in the biogeo-chemical cycling of iron. In situ iron limitation of heterotrophic metabolism may have profound effects on carbon flux in the ocean.

Diazotrophic bacterioplankton in a coral reef lagoon: phylogeny, diel nitrogenase expression and response to phosphate enrichment.

PubMed

Hewson, Ian; Moisander, Pia H; Morrison, Amanda E; Zehr, Jonathan P

2007-05-01

We investigated diazotrophic bacterioplankton assemblage composition in the Heron Reef lagoon (Great Barrier Reef, Australia) using culture-independent techniques targeting the nifH fragment of the nitrogenase gene. Seawater was collected at 3 h intervals over a period of 72 h (i.e. over diel as well as tidal cycles). An incubation experiment was also conducted to assess the impact of phosphate (PO(4)3*) availability on nifH expression patterns. DNA-based nifH libraries contained primarily sequences that were most similar to nifH from sediment, microbial mat and surface-associated microorganisms, with a few sequences that clustered with typical open ocean phylotypes. In contrast to genomic DNA sequences, libraries prepared from gene transcripts (mRNA amplified by reverse transcription-polymerase chain reaction) were entirely cyanobacterial and contained phylotypes similar to those observed in open ocean plankton. The abundance of Trichodesmium and two uncultured cyanobacterial phylotypes from previous studies (group A and group B) were studied by quantitative-polymerase chain reaction in the lagoon samples. These were detected as transcripts, but were not detected in genomic DNA. The gene transcript abundance of these phylotypes demonstrated variability over several diel cycles. The PO(4)3* enrichment experiment had a clearer pattern of gene expression over diel cycles than the lagoon sampling, however PO(4)3* additions did not result in enhanced transcript abundance relative to control incubations. The results suggest that a number of diazotrophs in bacterioplankton of the reef lagoon may originate from sediment, coral or beachrock surfaces, sloughing into plankton with the flooding tide. The presence of typical open ocean phylotype transcripts in lagoon bacterioplankton may indicate that they are an important component of the N cycle of the coral reef.

First order sea-level cycles and supercontinent break up

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heller, P.L.; Angevine, C.L.

1985-01-01

The authors have developed a model that successfully predicts the approximate magnitude and timing of long term sea-level change without relying on short term increases in global spreading rates. The model involves the following key assumptions. (1) Ocean basins have two types of area/age distributions; Pacific ocean basins are rimmed by subduction zones and have triangular distributions; and Atlantic ocean basins which open at constant rates, have no subduction, and so have rectangular distributions. (2) The total area of the global ocean is constant so that the Pacific basin must close as the Atlantic opens. These assumptions approximate modern globalmore » ocean basin conditions. The model begins with supercontinent break up. As the Atlantic begins to open, the mean age of the global ocean decreases, the mean depth of the sea floor shallows, and sea level, therefore, rises. Once the Atlantic occupies more than 8 to 10% of the global ocean area, the mean age and depth of the ocean floor increases resulting in a sea-level fall. The model can be applied to the mid-Cretaceous sea-level high stand which followed break up of Pangea by 80 to 100 Ma. Based on average Atlantic opening rates, sea level rises to a peak of 44 m at 80 Ma after opening began and then falls by 84 m to the present. Thus the model is capable of explaining approximately half of the total magnitude of the post-mid-Cretaceous eustatic fall without invoking short-term changes in global spreading rates. In addition, the model predicts the observed time lag between supercontinent break up and sea-level high stand for both Mesozoic as well as early Paleozoic time.« less

Carbon and Nutrient Dynamics and Fluxes in the Northwest European Continental Shelf Sea

NASA Astrophysics Data System (ADS)

Humphreys, M. P.; Moore, M. M.; Achterberg, E. P.; Griffiths, A.; Smilenova, A.; Chowdhury, M. Z. H.; Kivimae, C.; Hartman, S. E.; Hopkins, J.; Woodward, M. S.

2016-02-01

Despite covering only about 5 % of the Earth's ocean surface area, shallow marginal seas support 15-20 % of global primary productivity, and are the key interface between the land and the open ocean. They are therefore of critical importance to marine biogeochemical cycles, and may have a significant role in ocean uptake and storage of anthropogenic carbon dioxide (CO2). However, their behaviour is significantly more complex than that of the open ocean, because of the greater heterogeneity of the underlying physical, chemical and biological processes acting upon them. Detailed case-studies of individual regions are therefore essential in order to accurately evaluate their net global influence. The Northwest European continental shelf, in particular the Celtic Sea, was the target of extensive hydrographic sampling from March 2014 to September 2015, as part of the UK Shelf Seas Biogeochemistry research programme (UK-SSB). Here, we use the UK-SSB carbonate chemistry and macronutrient measurements to describe the seasonal biogeochemical cycle in the Celtic Sea. The 100-200 m deep water column proceeds from vertically well mixed in winter to a strongly stratified two-layer structure over spring-summer. The associated seasonal cycle in near-surface biological activity removes dissolved inorganic carbon (DIC) and nutrients, some of which are then exported into the deeper layer. Calculating total inventories of the biogeochemical variables throughout the seasonal cycle, we determine seasonal net CO2 uptake and investigate whether non-Redfieldian macronutrient uptake and remineralisation processes occur. Combining these results with estimated water exchange across the shelf edge further allows us to quantify the strength of the `shelf pump' sink for atmospheric (and anthropogenic) CO2.

Testing the limits in a greenhouse ocean: Did low nitrogen availability limit marine productivity during the end-Triassic mass extinction?

NASA Astrophysics Data System (ADS)

Schoepfer, Shane D.; Algeo, Thomas J.; Ward, Peter D.; Williford, Kenneth H.; Haggart, James W.

2016-10-01

The end-Triassic mass extinction has been characterized as a 'greenhouse extinction', related to rapid atmospheric warming and associated changes in ocean circulation and oxygenation. The response of the marine nitrogen cycle to these oceanographic changes, and the extent to which mass extinction intervals represent a deviation in nitrogen cycling from other ice-free 'greenhouse' periods of Earth history, remain poorly understood. The well-studied Kennecott Point section in Haida Gwaii, British Columbia, Canada, was deposited in the open Panthalassic Ocean, and is used here as a test case to better understand changes in the nitrogen cycle and marine productivity from the pre-crisis greenhouse of the Rhaetian to the latest-Rhaetian crisis interval. We estimated marine productivity from the late Norian to the early Hettangian using TOC- and P-based paleoproductivity transform equations, and then compared these estimates to records of sedimentary nitrogen isotopes, redox-sensitive trace elements, and biomarker data. Major negative excursions in δ15N (to ≤ 0 ‰) correspond to periods of depressed marine productivity. During these episodes, the development of a stable pycnocline below the base of the photic zone suppressed vertical mixing and limited N availability in surface waters, leading to low productivity and increased nitrogen fixation, as well as ecological stresses in the photic zone. The subsequent shoaling of euxinic waters into the ocean surface layer was fatal for most Triassic marine fauna, although the introduction of regenerated NH4+ into the photic zone may have allowed phytoplankton productivity to recover. These results indicate that the open-ocean nitrogen cycle was influenced by climatic changes during the latest Triassic, despite having existed in a greenhouse state for over 50 million years previously, and that low N availability limited marine productivity for hundreds of thousands of years during the end-Triassic crisis.

Modeling anoxic aggregates in the ocean - implications for nitrogen, sulfur and trace metal cycling

NASA Astrophysics Data System (ADS)

Bianchi, D.; Weber, T. S.; Deutsch, C.

2016-02-01

Anoxic conditions are uncommon in the open ocean, and mostly confined to the cores of oxygen minimum zones (OMZs). When oxygen runs out, a suite of alternative electron acceptors are used, leading to denitrification and, rarely in open waters, sulfate reduction. Anoxic conditions have been shown to develop inside millimeter-scale organic particles and aggregates, establishing microscale gradients that could sustain diverse microbial communities along a sequence of redox niches. We develop a model of the biogeochemistry of anoxic aggregates that includes aerobic and anaerobic reactions in a diffusion-limited environment, and present analytical and numerical solutions for the conditions that allow denitrification and sulfate reduction inside aggregates. The model is applied to realistic size spectra of particles sinking through the water column, and used to estimate the potential for particle-bound denitrification and sulfate reduction in the global ocean. We show that anoxia inside aggregates may be common throughout low oxygen waters, extending the niche of denitrifying metabolisms beyond fully anoxic zones. In the OMZ cores, aggregates can sustain pockets of sulfate reduction in otherwise non-sulfidic waters, depending on ambient nitrate concentrations, particle respiration rates, and other factors. We further discuss the implications for nitrogen, sulfur and trace metal cycling in the ocean.

Opening Pandora's Box: The impact of open system modeling on interpretations of anoxia

NASA Astrophysics Data System (ADS)

Hotinski, Roberta M.; Kump, Lee R.; Najjar, Raymond G.

2000-06-01

The geologic record preserves evidence that vast regions of ancient oceans were once anoxic, with oxygen levels too low to sustain animal life. Because anoxic conditions have been postulated to foster deposition of petroleum source rocks and have been implicated as a kill mechanism in extinction events, the genesis of such anoxia has been an area of intense study. Most previous models of ocean oxygen cycling proposed, however, have either been qualitative or used closed-system approaches. We reexamine the question of anoxia in open-system box models in order to test the applicability of closed-system results over long timescales and find that open and closed-system modeling results may differ significantly on both short and long timescales. We also compare a scenario with basinwide diffuse upwelling (a three-box model) to a model with upwelling concentrated in the Southern Ocean (a four-box model). While a three-box modeling approach shows that only changes in high-latitude convective mixing rate and character of deepwater sources are likely to cause anoxia, four-box model experiments indicate that slowing of thermohaline circulation, a reduction in wind-driven upwelling, and changes in high-latitude export production may also cause dysoxia or anoxia in part of the deep ocean on long timescales. These results suggest that box models must capture the open-system and vertically stratified nature of the ocean to allow meaningful interpretations of long-lived episodes of anoxia.

Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL

NASA Technical Reports Server (NTRS)

Robbins, L. L.; Coble, P. G.; Clayton, T. D.; Cai, W. J.

2008-01-01

Despite their relatively small surface area, ocean margins may have a significant impact on global biogeochemical cycles and, potentially, the global air-sea fluxes of carbon dioxide. Margins are characterized by intense geochemical and biological processing of carbon and other elements and exchange large amounts of matter and energy with the open ocean. The area-specific rates of productivity, biogeochemical cycling, and organic/inorganic matter sequestration are high in coastal margins, with as much as half of the global integrated new production occurring over the continental shelves and slopes (Walsh, 1991; Doney and Hood, 2002; Jahnke, in press). However, the current lack of knowledge and understanding of biogeochemical processes occurring at the ocean margins has left them largely ignored in most of the previous global assessments of the oceanic carbon cycle (Doney and Hood, 2002). A major source of North American and global uncertainty is the Gulf of Mexico, a large semi-enclosed subtropical basin bordered by the United States, Mexico, and Cuba. Like many of the marginal oceans worldwide, the Gulf of Mexico remains largely unsampled and poorly characterized in terms of its air-sea exchange of carbon dioxide and other carbon fluxes. The goal of the workshop was to bring together researchers from multiple disciplines studying terrestrial, aquatic, and marine ecosystems to discuss the state of knowledge in carbon fluxes in the Gulf of Mexico, data gaps, and overarching questions in the Gulf of Mexico system. The discussions at the workshop were intended to stimulate integrated studies of marine and terrestrial biogeochemical cycles and associated ecosystems that will help to establish the role of the Gulf of Mexico in the carbon cycle and how it might evolve in the face of environmental change.

pyhector: A Python interface for the simple climate model Hector

DOE PAGES

Willner, Sven N.; Hartin, Corinne; Gieseke, Robert

2017-04-01

Here, pyhector is a Python interface for the simple climate model Hector (Hartin et al. 2015) developed in C++. Simple climate models like Hector can, for instance, be used in the analysis of scenarios within integrated assessment models like GCAM1, in the emulation of complex climate models, and in uncertainty analyses. Hector is an open-source, object oriented, simple global climate carbon cycle model. Its carbon cycle consists of a one pool atmosphere, three terrestrial pools which can be broken down into finer biomes or regions, and four carbon pools in the ocean component. The terrestrial carbon cycle includes primary productionmore » and respiration fluxes. The ocean carbon cycle circulates carbon via a simplified thermohaline circulation, calculating air-sea fluxes as well as the marine carbonate system. The model input is time series of greenhouse gas emissions; as example scenarios for these the Pyhector package contains the Representative Concentration Pathways (RCPs)2.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willner, Sven N.; Hartin, Corinne; Gieseke, Robert

Here, pyhector is a Python interface for the simple climate model Hector (Hartin et al. 2015) developed in C++. Simple climate models like Hector can, for instance, be used in the analysis of scenarios within integrated assessment models like GCAM1, in the emulation of complex climate models, and in uncertainty analyses. Hector is an open-source, object oriented, simple global climate carbon cycle model. Its carbon cycle consists of a one pool atmosphere, three terrestrial pools which can be broken down into finer biomes or regions, and four carbon pools in the ocean component. The terrestrial carbon cycle includes primary productionmore » and respiration fluxes. The ocean carbon cycle circulates carbon via a simplified thermohaline circulation, calculating air-sea fluxes as well as the marine carbonate system. The model input is time series of greenhouse gas emissions; as example scenarios for these the Pyhector package contains the Representative Concentration Pathways (RCPs)2.« less

Improving the Representation of Estuarine Processes in Earth System Models

NASA Astrophysics Data System (ADS)

Sun, Q.; Whitney, M. M.; Bryan, F.; Tseng, Y. H.

2016-12-01

The exchange of freshwater between the rivers and estuaries and the open ocean represents a unique form of scale-interaction in the climate system. The local variability in the terrestrial hydrologic cycle is integrated by rivers over potentially large drainage basins (up to semi-continental scales), and is then imposed on the coastal ocean at the scale of a river mouth. Appropriately treating riverine freshwater discharge into the oceans in Earth system models is a challenging problem. Commonly, the river runoff is discharged into the ocean models with zero salinity and arbitrarily distributed either horizontally or vertically over several grid cells. Those approaches entirely neglect estuarine physical processes that modify river inputs before they reach the open ocean. A physically based Estuary Box Model (EBM) is developed to parameterize the mixing processes in estuaries. The EBM has a two-layer structure representing the mixing processes driven by tides and shear flow within the estuaries. It predicts the magnitude of the mixing driven exchange flow, bringing saltier lower-layer shelf water into the estuary to mix with river water prior to discharge to the upper-layer open ocean. The EBM has been tested against observations and high-resolution three-dimensional simulations of the Columbia River estuary, showing excellent agreement in the predictions of the strength of the exchange flow and the salinity of the discharged water, including modulation with the spring-neap tidal cycle. The EBM is implemented globally at every river discharge point of the Community Earth System Model (CESM). In coupled ocean-sea ice experiments driven by CORE surface forcing, the sea surface salinity (SSS) in the coastal ocean is increased globally compared to the standard model, contributing to a decrease in coastal stratification. The SSS near the mouths of some of the largest rivers is decreased due to the reduction in the area over which riverine fresh water is discharged. The results from experiments with the fully coupled CESM are broadly consistent, supporting the inclusion of the parameterization in CESM version 2 to be released in late 2016.

Astronomical Constraints on the Duration of Early Jurassic Stages and Global Carbon Cycle and Climatic Perturbations

NASA Astrophysics Data System (ADS)

Ruhl, M.; Hesselbo, S. P.; Hinnov, L.; Jenkyns, H. C.; Storm, M.; Xu, W.; Riding, J. B.; Ullmann, C. V.

2015-12-01

The Early Jurassic (201.3 to 174.1 Ma) is bracketed by the end-Triassic mass extinction and global warming event, and the Toarcian-Aalenian shift to (global) icehouse conditions (McElwain et al., 1999; Hesselbo et al., 2002; Ruhl et al., 2011; Korte et al., in review). It is further marked by the early Toarcian Oceanic Anoxic Event (T-OAE), with possibly the largest exogenic carbon cycle perturbation of the Mesozoic and related perturbations in global geochemical cycles, climate and the environment, which are linked to large igneous province emplacement in the Karoo-Ferrar region (Jenkyns, 2010; Burgess et al., 2015). Furthermore, Early Jurassic continental rifting and the break-up of Pangaea and subsequent Early Jurassic opening of the Hispanic Corridor and Viking Strait respectively linked the equatorial Tethys Ocean to Eastern Panthalassa and the high-latitude Arctic Boreal realm. This initiated changes in (global) ocean currents and Earth's heat distribution and ultimately was followed by the opening of the proto-North Atlantic (Porter et al., 2013; Korte et al., in review). Here, we present high-resolution (sub-precession scale) elemental concentration data from the Mochras borehole (UK), which represents ~1300m of possibly the most complete and expanded lower Jurassic hemi-pelagic marine sedimentary archive known. We construct a floating ~9 Myr astronomical time-scale for the complete Early Jurassic Pliensbachian stage and biozones. Combined with radiometric and astrochronological constraints on early Jurassic stage boundaries, we construct a new Early Jurassic Time-Scale. With this we assess the duration and rate of change of early Jurassic global carbon cycle and climatic perturbations and we asses fundamental changes in the nature and expression of Early Jurassic long (100 - 1000 kyr) eccentricity cycles.

Reduced-Order Biogeochemical Flux Model for High-Resolution Multi-Scale Biophysical Simulations

NASA Astrophysics Data System (ADS)

Smith, Katherine; Hamlington, Peter; Pinardi, Nadia; Zavatarelli, Marco

2017-04-01

Biogeochemical tracers and their interactions with upper ocean physical processes such as submesoscale circulations and small-scale turbulence are critical for understanding the role of the ocean in the global carbon cycle. These interactions can cause small-scale spatial and temporal heterogeneity in tracer distributions that can, in turn, greatly affect carbon exchange rates between the atmosphere and interior ocean. For this reason, it is important to take into account small-scale biophysical interactions when modeling the global carbon cycle. However, explicitly resolving these interactions in an earth system model (ESM) is currently infeasible due to the enormous associated computational cost. As a result, understanding and subsequently parameterizing how these small-scale heterogeneous distributions develop and how they relate to larger resolved scales is critical for obtaining improved predictions of carbon exchange rates in ESMs. In order to address this need, we have developed the reduced-order, 17 state variable Biogeochemical Flux Model (BFM-17) that follows the chemical functional group approach, which allows for non-Redfield stoichiometric ratios and the exchange of matter through units of carbon, nitrate, and phosphate. This model captures the behavior of open-ocean biogeochemical systems without substantially increasing computational cost, thus allowing the model to be combined with computationally-intensive, fully three-dimensional, non-hydrostatic large eddy simulations (LES). In this talk, we couple BFM-17 with the Princeton Ocean Model and show good agreement between predicted monthly-averaged results and Bermuda testbed area field data (including the Bermuda-Atlantic Time-series Study and Bermuda Testbed Mooring). Through these tests, we demonstrate the capability of BFM-17 to accurately model open-ocean biochemistry. Additionally, we discuss the use of BFM-17 within a multi-scale LES framework and outline how this will further our understanding of turbulent biophysical interactions in the upper ocean.

Reduced-Order Biogeochemical Flux Model for High-Resolution Multi-Scale Biophysical Simulations

NASA Astrophysics Data System (ADS)

Smith, K.; Hamlington, P.; Pinardi, N.; Zavatarelli, M.; Milliff, R. F.

2016-12-01

Biogeochemical tracers and their interactions with upper ocean physical processes such as submesoscale circulations and small-scale turbulence are critical for understanding the role of the ocean in the global carbon cycle. These interactions can cause small-scale spatial and temporal heterogeneity in tracer distributions which can, in turn, greatly affect carbon exchange rates between the atmosphere and interior ocean. For this reason, it is important to take into account small-scale biophysical interactions when modeling the global carbon cycle. However, explicitly resolving these interactions in an earth system model (ESM) is currently infeasible due to the enormous associated computational cost. As a result, understanding and subsequently parametrizing how these small-scale heterogeneous distributions develop and how they relate to larger resolved scales is critical for obtaining improved predictions of carbon exchange rates in ESMs. In order to address this need, we have developed the reduced-order, 17 state variable Biogeochemical Flux Model (BFM-17). This model captures the behavior of open-ocean biogeochemical systems without substantially increasing computational cost, thus allowing the model to be combined with computationally-intensive, fully three-dimensional, non-hydrostatic large eddy simulations (LES). In this talk, we couple BFM-17 with the Princeton Ocean Model and show good agreement between predicted monthly-averaged results and Bermuda testbed area field data (including the Bermuda-Atlantic Time Series and Bermuda Testbed Mooring). Through these tests, we demonstrate the capability of BFM-17 to accurately model open-ocean biochemistry. Additionally, we discuss the use of BFM-17 within a multi-scale LES framework and outline how this will further our understanding of turbulent biophysical interactions in the upper ocean.

Deep winter convection and phytoplankton dynamics in the NW Mediterranean Sea under present climate and future (horizon 2030) scenarios.

PubMed

Macias, Diego; Garcia-Gorriz, Elisa; Stips, Adolf

2018-04-26

Deep water convection (DC) in winter is one of the major processes driving open-ocean primary productivity in the Northwestern Mediterranean Sea. DC is highly variable in time, depending on the specific conditions (stratification, circulation and ocean-atmosphere interactions) of each specific winter. This variability also drives the interannual oscillations of open-ocean primary productivity in this important region for many commercially-important fish species. We use a coupled model system to 1) understand to what extent DC impacts phytoplankton seasonality in the present-day and 2) to explore potential changes in future scenarios (~2030). Our model represents quite accurately the present-day characteristics of DC and its importance for open-ocean phytoplankton blooms. However, for the future scenarios the importance of deep nutrients in fertilizing the euphotic layer of the NW Mediterranean decreases. The model simulates changes in surface density and on the levels of kinetic energy that make mesoscale activity associated with horizontal currents to become a more important fertilization mechanism, inducing subsequently phenological changes in seasonal plankton cycles. Because of our focus on the open-sea, an exact quantification of the impact of those changes on the overall biological production of the NW Mediterranean cannot be made at the moment.

Projections of Ocean Acidification Under the U.N. Framework Convention of Climate Change Using a Reduced-Form Climate Carbon-Cycle Model

NASA Astrophysics Data System (ADS)

Hartin, C.

2016-02-01

Ocean chemistry is quickly changing in response to continued anthropogenic emissions of carbon to the atmosphere. Mean surface ocean pH has already decreased by 0.1 units relative to the preindustrial era. We use an open-source, simple climate and carbon cycle model ("Hector") to investigate future changes in ocean acidification (pH and calcium carbonate saturations) under the climate agreement from the United Nations Convention on Climate Change Conference (UNFCCC) of Parties in Paris 2015 (COP 21). Hector is a reduced-form, very fast-executing model that can emulate the global mean climate of the CMIP5 models, as well as the inorganic carbon cycle in the upper ocean, allowing us to investigate future changes in ocean acidification. We ran Hector under three different emissions trajectories, using a sensitivity analysis approach to quantify model uncertainty and capture a range of possible ocean acidification changes. The first trajectory is a business-as-usual scenario comparable to a Representative Concentration Pathway (RCP) 8.5, the second a scenario with the COP 21 commitments enacted, and the third an idealized scenario keeping global temperature change to 2°C, comparable to a RCP 2.6. Preliminary results suggest that under the COP 21 agreements ocean pH at 2100 will decrease by 0.2 units and surface saturations of aragonite (calcite) will decrease by 0.9 (1.4) units relative to 1850. Under the COP 21 agreement the world's oceans will be committed to a degree of ocean acidification, however, these changes may be within the range of natural variability evident in some paleo records.

The Marine Geochemistry of Iron and Iron Isotopes

DTIC Science & Technology

2004-09-01

suspension of sediments, and hydrothermal vents. A schematic of the Fe cycle in the open ocean is shown in Figure 1.1. Fe concentrations are highest near...than 2% of their coastal values 100 km from the California continental margin (JOHNSON et al., 1997). Hydrothermal input of Fe is believed to be...important only near its sources (mostly in the deep ocean) because most of the Fe from hydrothermal vents precipitates near the vents and ridge axis (DE

Aquarius and Remote Sensing of Sea Surface Salinity from Space

NASA Technical Reports Server (NTRS)

LeVine, David M.; Lagerloef, G. S. E.; Torrusio, S.

2012-01-01

Aquarius is an L-band radiometer and scatterometer instrument combination designed to map the salinity field at the surface of the ocean from space. The instrument is designed to provide global salinity maps on a monthly basis with a spatial resolution of 150 km and an accuracy of 0.2 psu. The science objective is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean. This data will promote understanding of ocean circulation and its role in the global water cycle and climate.

Natural variability of pCO2 and pH in the Atlantic and Pacific coastal margins of the U.S

NASA Astrophysics Data System (ADS)

Sutton, A. J.; Sabine, C. L.; Feely, R. A.; Newton, J.; Salisbury, J.; Vandemark, D. C.; Musielewicz, S. B.; Maenner-Jones, S.; Bott, R.; Lawrence-Slavas, N.

2011-12-01

The discovery that seawater chemistry is changing as a result of carbon dioxide (CO2) emissions, referred to as "ocean acidification", has prompted a large effort to understand how this changing chemistry will impact marine life. Changes in carbon chemistry have been documented in the open ocean; however, in dynamic coastal systems where many marine species live, ocean acidification and the natural biogeochemical variability that organisms are currently exposed to are poorly quantified. In 2010 we began equipping coastal moorings currently measuring pCO2 with pH and other biogeochemical sensors to measure ocean acidification parameters at 3 hour intervals in the surface water. Here we present the magnitude and diurnal to seasonal variability of pCO2 and pH during the first year of observations at 2 sites in the Atlantic and Pacific coastal margins of the U.S.: the Gulf of Maine and outer coast of Washington state. Both the magnitude and range of pCO2 and pH values were much greater at the coastal moorings compared to the open ocean mooring at Ocean Station Papa in the North Pacific and also varied between the two coastal mooring sites. We observed maximum pCO2 values in coastal waters exceeding predicted values for the open ocean at 2x pre-industrial CO2 levels. The range of pCO2 and pH values during this time series was approximately 4 times the range observed at open ocean mooring Papa (2007-2011 time series). In many cases, large variance was observed at short time scales, with values fluctuating more than 200 μatm pCO2 and 0.2 pH between 3-hour cycles. These types of observations are critical for understanding how ocean acidification will manifest in naturally dynamic coastal systems and for informing the experimental design of species response studies that aim to mimic carbon chemistry experienced by coastal marine organisms.

Patterns in stable isotope ratios of particulate material from the eastern US continental shelf

EPA Science Inventory

Stable isotope measurements of nitrogen and carbon (δ15N, δ13C) in estuarine, nearshore, and open ocean ecosystems are often utilized in order to characterize human influences, elucidate food web dynamics, or better understand nitrogen cycling. Reliable information a...

Ecosystem behavior at Bermuda Station [open quotes]S[close quotes] and ocean weather station [open quotes]India[close quotes]: A general circulation model and observational analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fasham, M.J.R.; Sarmiento, J.L.; Slater, R.D.

1993-06-01

One important theme of modern biological oceanography has been the attempt to develop models of how the marine ecosystem responds to variations in the physical forcing functions such as solar radiation and the wind field. The authors have addressed the problem by embedding simple ecosystem models into a seasonally forced three-dimensional general circulation model of the North Atlantic ocean. In this paper first, some of the underlying biological assumptions of the ecosystem model are presented, followed by an analysis of how well the model predicts the seasonal cycle of the biological variables at Bermuda Station s' and Ocean Weather Stationmore » India. The model gives a good overall fit to the observations but does not faithfully model the whole seasonal ecosystem model. 57 refs., 25 figs., 5 tabs.« less

Passive margin evolution, initiation of subduction and the Wilson cycle

NASA Astrophysics Data System (ADS)

Cloetingh, S. A. P. L.; Wortel, M. J. R.; Vlaar, N. J.

1984-10-01

We have constructed finite element models at various stages of passive margin evolution, in which we have incorporated the system of forces acting on the margin, depth-dependent rheological properties and lateral variations across the margin. We have studied the interrelations between age-dependent forces, geometry and rheology, to decipher their net effect on the state of stress at passive margins. Lithospheric flexure induced by sediment loading dominates the state of stress at passive margins. This study has shown that if after a short evolution of the margin (time span a few tens of million years) subduction has not yet started, continued aging of the passive margin alone does not result in conditions more favourable for transformation into an active margin. Although much geological evidence is available in support of the key role small ocean basins play in orogeny and ophiolite emplacement, evolutionary frameworks of the Wilson cycle usually are cast in terms of opening and closing of wide ocean basins. We propose a more limited role for large oceans in the Wilson cycle concept.

The oxygen minimum zone of the eastern South Pacific

NASA Astrophysics Data System (ADS)

Ulloa, Osvaldo; Pantoja, Silvio

2009-07-01

In spite of the fact that oxygen-deficient waters with ⩽20 μM of dissolved oxygen—known as oxygen minimum zones (OMZs)—occupy only ˜1% of the volume of the global ocean, they disproportionately affect global biogeochemical cycles, particularly the nitrogen cycle. The macrobiota diversity in OMZs is low, but the fauna that do inhabit these regions present special adaptations to the low-oxygen conditions. Conversely, microbial communities in the OMZ water column and sediments are abundant and phylogenetically and metabolically very diverse, and microbial processes occurring therein (e.g., denitrification, anammox, and organic matter degradation) are important for global marine biogeochemical cycles. In this introductory article, we present the collection of papers for the special volume on the OMZ of the eastern South Pacific, one of the three main open-ocean oxygen-deficient regions of the global ocean. These papers deal with aspects of regional oceanography, inorganic and organic geochemistry, ecology, and the biochemistry of micro and macro organisms—both in the plankton and in the sediments—and past changes in the fish scales preserved in the sediments bathed by OMZ waters.

Nutrient co-limited Trichodesmium as nitrogen source or sink in a future ocean.

PubMed

Walworth, Nathan G; Fu, Fei-Xue; Lee, Michael D; Cai, Xiaoni; Saito, Mak A; Webb, Eric A; Hutchins, David A

2017-11-27

Nitrogen-fixing (N 2 ) cyanobacteria provide bioavailable nitrogen to vast ocean regions but are in turn limited by iron (Fe) and/or phosphorus (P), which may force them to employ alternative nitrogen acquisition strategies. The adaptive responses of nitrogen-fixers to global-change drivers under nutrient-limited conditions could profoundly alter the current ocean nitrogen and carbon cycles. Here, we show that the globally-important N 2 -fixer Trichodesmium fundamentally shifts nitrogen metabolism towards organic-nitrogen scavenging following long-term high-CO 2 adaptation under iron and/or phosphorus (co)-limitation. Global shifts in transcripts and proteins under high CO 2 /Fe-limited and/or P-limited conditions include decreases in the N 2 -fixing nitrogenase enzyme, coupled with major increases in enzymes that oxidize trimethylamine (TMA). TMA is an abundant, biogeochemically-important organic nitrogen compound that supports rapid Trichodesmium growth while inhibiting N 2 fixation. In a future high-CO 2 ocean, this whole-cell energetic reallocation towards organic nitrogen scavenging and away from N 2 -fixation may reduce new-nitrogen inputs by Trichodesmium , while simultaneously depleting the scarce fixed-nitrogen supplies of nitrogen-limited open ocean ecosystems. Importance Trichodesmium is among the most biogeochemically-significant microorganisms in the ocean, since it supplies up to 50% of the new nitrogen supporting open ocean food webs. We used Trichodesmium cultures adapted to high CO 2 for 7 years followed by additional exposure to iron and/or phosphorus (co)-limitation. We show that 'future ocean' conditions of high CO 2 and concurrent nutrient limitation(s) fundamentally shift nitrogen metabolism away from nitrogen fixation, and instead towards upregulation of organic-nitrogen scavenging pathways. We show that Trichodesmium's responses to projected future ocean conditions include decreases in the nitrogen-fixing nitrogenase enzymes, coupled with major increases in enzymes that oxidize the abundant organic nitrogen source trimethylamine (TMA). Such a shift towards organic nitrogen uptake and away from nitrogen fixation may substantially reduce new-nitrogen inputs by Trichodesmium to the rest of the microbial community in the future high-CO 2 ocean, with potential global implications for ocean carbon and nitrogen cycling. Copyright © 2017 American Society for Microbiology.

Biogeochemical responses of the carbon cycle to natural and human perturbations: Past, present, and future

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ver, L.M.B.; Mackenzie, F.T.; Lerman, A.

In the past three centuries, human perturbations of the environment have affected the biogeochemical behavior of the global carbon cycle and that of the other three nutrient elements closely coupled to carbon: nitrogen, phosphorus, and sulfur. The partitioning of anthropogenic CO{sub 2} among its various sinks in the past, for the present, and for projections into the near future is controlled by the interactions of these four elemental cycles within the major environmental domains of the land, atmosphere, coastal oceanic zone, and open ocean. The authors analyze the past, present, and future behavior of the global carbon cycle using themore » Terrestrial-Ocean-aTmosphere Ecosystem Model (TOTEM), a unique process-based model of the four global coupled biogeochemical cycles of carbon, nitrogen, phosphorus, and sulfur. They find that during the past 300 yrs, anthropogenic CO{sub 2} was mainly stored in the atmosphere and in the open ocean. Human activities on land caused an enhanced loss of mass from the terrestrial organic matter reservoirs (phytomass and humus) mainly through deforestation and consequently increased humus remineralization, erosion, and transport to the coastal margins by rivers and runoff. Photosynthetic uptake by the terrestrial phytomass was enhanced owing to fertilization by increasing atmospheric CO{sub 2} concentrations and supported by nutrients remineralized from organic matter. TOTEM results indicate that through most of the past 300 yrs, the loss of C from deforestation and other land-use activities was greater than the gain from the enhanced photosynthetic uptake. Since pre-industrial time (since 1700), the net flux of CO{sub 2} from the coastal waters has decreased by 40%, from 0.20 Gt C/yr to 0.12 Gt C/yr. TOTEM analyses of atmospheric CO{sub 2} concentrations for the 21st century were based on the fossil-fuel emission projections of IPCC (business as usual scenario) and of the more restrictive UN 1997 Kyoto Protocol. By the mid-21st century, the projected atmospheric CO{sub 2} concentrations range from about 550 ppmv (TOTEM, based on IPCC projected emissions) to 510 ppmv (IPCC projection) and to 460 ppmv (TOTEM, based on the Kyoto Protocol reduced emissions).« less

An Analysis of Wilson Cycle Plate Margins

NASA Astrophysics Data System (ADS)

Buiter, S.; Torsvik, T. H.

2012-12-01

The Wilson Cycle theory that oceans close and open along the same suture is a powerful concept in analyses of ancient plate tectonics. It implies that collision zones are structures that are able to localize extensional deformation for long times after the collision has waned. However, some sutures are seemingly never reactivated and already Tuzo Wilson recognized that Atlantic break-up did not follow the precise line of previous junction. We have reviewed margin pairs around the Atlantic and Indian Oceans with the aim to evaluate the extent to which oceanic opening used former sutures, summarize delay times between collision and break-up, and analyze the role of mantle plumes in continental break-up. We aid our analyses with plate tectonic reconstructions using GPlates (www.gplates.org). Although at first sight opening of the North Atlantic Ocean largely seems to follow the Iapetus and Rheic sutures, a closer look reveals deviations. For example, Atlantic opening did not utilize the Iapetus suture in Great Britain and rather than opening along the younger Rheic suture north of Florida, break-up occurred along the older Pan-African structures south of Florida. We find that today's oceanic Charlie Gibbs Fracture Zone, between Ireland and Newfoundland, is aligned with the Iapetus suture. We speculate therefore that in this region the Iapetus suture was reactivated as a transform fault. As others before us, we find no correlation of suture and break-up age. Often continental break-up occurs some hundreds of Myrs after collision, but it may also take over 1000 Myr, as for example for Australia - Antarctica and Congo - São Francisco. This places serious constraints on potential collision zone weakening mechanisms. Several studies have pointed to a link between continental break-up and large-scale mantle upwellings. It is, however, much debated whether plumes use existing rifts as a pathway, or whether plumes play an active role in causing rifting. We find a positive correlation between break-up age and plume age, which we interpret to indicate that plumes can aid the factual continental break-up. However, plumes may have been guided towards the rift for margins that experienced a long rift history (e.g., Norway-Greenland), to then trigger the break-up. This could offer a partial reconciliation in the debate of a passive or active role for mantle plumes in continental break-up.

Placing an upper limit on cryptic marine sulphur cycling.

PubMed

Johnston, D T; Gill, B C; Masterson, A; Beirne, E; Casciotti, K L; Knapp, A N; Berelson, W

2014-09-25

A quantitative understanding of sources and sinks of fixed nitrogen in low-oxygen waters is required to explain the role of oxygen-minimum zones (OMZs) in controlling the fixed nitrogen inventory of the global ocean. Apparent imbalances in geochemical nitrogen budgets have spurred numerous studies to measure the contributions of heterotrophic and autotrophic N2-producing metabolisms (denitrification and anaerobic ammonia oxidation, respectively). Recently, 'cryptic' sulphur cycling was proposed as a partial solution to the fundamental biogeochemical problem of closing marine fixed-nitrogen budgets in intensely oxygen-deficient regions. The degree to which the cryptic sulphur cycle can fuel a loss of fixed nitrogen in the modern ocean requires the quantification of sulphur recycling in OMZ settings. Here we provide a new constraint for OMZ sulphate reduction based on isotopic profiles of oxygen ((18)O/(16)O) and sulphur ((33)S/(32)S, (34)S/(32)S) in seawater sulphate through oxygenated open-ocean and OMZ-bearing water columns. When coupled with observations and models of sulphate isotope dynamics and data-constrained model estimates of OMZ water-mass residence time, we find that previous estimates for sulphur-driven remineralization and loss of fixed nitrogen from the oceans are near the upper limit for what is possible given in situ sulphate isotope data.

Manifestation, Drivers, and Emergence of Open Ocean Deoxygenation.

PubMed

Levin, Lisa A

2018-01-03

Oxygen loss in the ocean, termed deoxygenation, is a major consequence of climate change and is exacerbated by other aspects of global change. An average global loss of 2% or more has been recorded in the open ocean over the past 50-100 years, but with greater oxygen declines in intermediate waters (100-600 m) of the North Pacific, the East Pacific, tropical waters, and the Southern Ocean. Although ocean warming contributions to oxygen declines through a reduction in oxygen solubility and stratification effects on ventilation are reasonably well understood, it has been a major challenge to identify drivers and modifying factors that explain different regional patterns, especially in the tropical oceans. Changes in respiration, circulation (including upwelling), nutrient inputs, and possibly methane release contribute to oxygen loss, often indirectly through stimulation of biological production and biological consumption. Microbes mediate many feedbacks in oxygen minimum zones that can either exacerbate or ameliorate deoxygenation via interacting nitrogen, sulfur, and carbon cycles. The paleo-record reflects drivers of and feedbacks to deoxygenation that have played out through the Phanerozoic on centennial, millennial, and hundred-million-year timescales. Natural oxygen variability has made it difficult to detect the emergence of a climate-forced signal of oxygen loss, but new modeling efforts now project emergence to occur in many areas in 15-25 years. Continued global deoxygenation is projected for the next 100 or more years under most emissions scenarios, but with regional heterogeneity. Notably, even small changes in oxygenation can have significant biological effects. New efforts to systematically observe oxygen changes throughout the open ocean are needed to help address gaps in understanding of ocean deoxygenation patterns and drivers.

Manifestation, Drivers, and Emergence of Open Ocean Deoxygenation

NASA Astrophysics Data System (ADS)

Levin, Lisa A.

2018-01-01

Oxygen loss in the ocean, termed deoxygenation, is a major consequence of climate change and is exacerbated by other aspects of global change. An average global loss of 2% or more has been recorded in the open ocean over the past 50-100 years, but with greater oxygen declines in intermediate waters (100-600 m) of the North Pacific, the East Pacific, tropical waters, and the Southern Ocean. Although ocean warming contributions to oxygen declines through a reduction in oxygen solubility and stratification effects on ventilation are reasonably well understood, it has been a major challenge to identify drivers and modifying factors that explain different regional patterns, especially in the tropical oceans. Changes in respiration, circulation (including upwelling), nutrient inputs, and possibly methane release contribute to oxygen loss, often indirectly through stimulation of biological production and biological consumption. Microbes mediate many feedbacks in oxygen minimum zones that can either exacerbate or ameliorate deoxygenation via interacting nitrogen, sulfur, and carbon cycles. The paleo-record reflects drivers of and feedbacks to deoxygenation that have played out through the Phanerozoic on centennial, millennial, and hundred-million-year timescales. Natural oxygen variability has made it difficult to detect the emergence of a climate-forced signal of oxygen loss, but new modeling efforts now project emergence to occur in many areas in 15-25 years. Continued global deoxygenation is projected for the next 100 or more years under most emissions scenarios, but with regional heterogeneity. Notably, even small changes in oxygenation can have significant biological effects. New efforts to systematically observe oxygen changes throughout the open ocean are needed to help address gaps in understanding of ocean deoxygenation patterns and drivers.

Biogenic barite preciptiation at micromolar ambient sulfate

NASA Astrophysics Data System (ADS)

Horner, T. J.; Pryer, H. V.; Nielsen, S.; Ricketts, R. D.

2016-12-01

Earth's early oceans were essentially devoid of sulfate, yet barium sulfate (barite) deposits are common to ancient sediments. Most explanations for this `barite paradox' overlook biogenic barite precipitation—the dominant vector of particulate barium cycling in modern seawater—as the ancient oceans were presumably strongly undersaturated with respect to barite. We tested whether biogenic barite could indeed precipitate at trace sulfate by examining the particulate multi-element and Ba-isotopic geochemistry of one of the largest trace-sulfate ecosystems on Earth: Lake Superior. Despite exceptional levels of barite undersaturation in Lake Superior, we find unambiguous evidence of biogenic barite precipitation that is correlated with the depths of greatest organic matter remineralization in the water column. The overall pattern of particulate barium cycling in Lake Superior is strikingly similar to that seen in the open ocean, supporting the critical role of particle-associated `microenvironments' that become rich in respired sulfate as protected sites of biogenic barite formation. Our observations offer a microbially-mediated mechanism for barite formation at micromolar ambient sulfate and thus also a potential resolution to the barite paradox in the ancient oceans.

Environmental Genomic Analysis of Stratified Microbial Communities and Climate Active Gases in the Subarctic Pacific Oxygen Minimum Zone

NASA Astrophysics Data System (ADS)

Wright, J.; Hallam, S.; Merzouk, A.; Tortell, P.

2008-12-01

Oxygen minimum zones (OMZs) are areas of low dissolved oxygen concentrations that play a major role in biogeochemical cycling within the world's oceans. They are major sinks for nitrogen and sources for the greenhouse gases carbon dioxide and nitrous oxide. Therefore, microbial mediated biological activity associated with these systems directly impacts ocean productivity and global climate balance. There is increasing evidence that ocean warming trends will decrease dissolved oxygen concentrations within the coastal and interior regions of the subarctic Pacific, causing an expansion of the hypoxic boundary layer. This expansion will have a direct effect on coastal benthic ecosystems and the productivity of marine fisheries due to habitat loss and changes in nutrient cycling. In order to understand the potential implications of these transitions, we are performing environmental genomic analyses of indigenous microbial communities found in coastal and open ocean OMZs in the subarctic Pacific Ocean in relation to dissolved gas and nutrient concentrations. In addition to identifying and describing the key microbial players and biochemical pathways contributing to carbon, nitrogen and sulfur metabolism within the subarctic Pacific Ocean, this work provides a solid comparative genomic foundation for understanding the biogeochemical processes at work in marine OMZs around the globe.

Characterisation of intact proteins in aquatic samples from the Florida Everglades

NASA Astrophysics Data System (ADS)

Jones, V.; Ruddell, C. J.; Wainwright, G.; Rees, H. H.; Jaffe, R.; Penkman, K. E. H.; Collins, C. J.; Wolff, G. A.

2003-04-01

Dissolved organic nitrogen (DON) is the largest reservoir of reduced nitrogen in the oceans. Limited knowledge of the molecular composition of DON hinders our understanding of its cycling. The need to comprehend the DON cycle is nowadays more imperative than ever, as there is evidence that concentrations of nitrate are decreasing, while concentrations of DON are increasing in the surface ocean, as an indirect effect of global warming and hence stratification of the water column (Karl et al., 2001). Proteins typically account for 5-10% of DON. Recently, it has been suggested that certain, bacterially-derived, proteins found in the ocean are not as labile as was originally thought (e.g. Tanoue et al., 1995) and may therefore form a crucial part of the long term DON cycle. Here, we have applied gel electrophoresis in combination with mass spectrometry and amino acid enantiomer (D/L) analysis, to characterise proteins from aquatic samples and consider their origin. Samples were collected in the Florida Everglades at locations selected to represent an array of ecosystems, ranging from marsh water to marine coastal environments. Application of gel electrophoresis in combination with mass spectrometry revealed that each sample had a complex and characteristic protein distribution. Some proteins were common to more than one site. The bacterial protein of 48 kDa, previously reported as ubiquitous in the open ocean (e.g. Tanoue et al., 1995), was only present at one sampling location strongly affected by offshore currents. Amino acid enantiomer (D/L) analysis revealed that the bacterial input to amino acid nitrogen was an order of magnitude smaller than that reported for open ocean samples (McCarthy et al., 1998), although a trend towards higher bacterial input was observed from freshwater to marine sampling locations. We suggest that this is due to the presence of additional sources of protein to the DON pool, such as the higher plant vegetation, in freshwater and coastal environments compared to the open ocean. References Karl, D., Bidigare, R.R., Letelier, R.M., 2001. Long-term changes in plankton community structure and productivity in the North Pacific Subtropical Gyre: The domain shift hypothesis. Deep-Sea Research II, 48: 1449-1470. McCarthy, M.D., Hedges, J.J. Benner, R., 1998. Major bacterial contribution to marine dissolved organic nitrogen. Science, 281: 231-234. Tanoue E., Sumie, N., Kamo, M., Tsurita, A, 1995. Bacterial membranes: Possible sources of major dissolved protein in seawater. Geochimica and Cosmochimica Acta, 59: 2643-2648

Exploring frontiers of the deep biosphere through scientific ocean drilling

NASA Astrophysics Data System (ADS)

Inagaki, F.; D'Hondt, S.; Hinrichs, K. U.

2015-12-01

Since the first deep biosphere-dedicated Ocean Drilling Program (ODP) Leg 201 using the US drill ship JOIDES Resolution in 2002, scientific ocean drilling has offered unique opportunities to expand our knowledge of the nature and extent of the deep biosphere. The latest estimate of the global subseafloor microbial biomass is ~1029cells, accounting for 4 Gt of carbon and ~1% of the Earth's total living biomass. The subseafloor microbial communities are evolutionarily diverse and their metabolic rates are extraordinarily slow. Nevertheless, accumulating activity most likely plays a significant role in elemental cycles over geological time. In 2010, during Integrated Ocean Drilling Program (IODP) Expedition 329, the JOIDES Resolutionexplored the deep biosphere in the open-ocean South Pacific Gyre—the largest oligotrophic province on our planet. During Expedition 329, relatively high concentrations of dissolved oxygen and significantly low biomass of microbial populations were observed in the entire sediment column, indicating that (i) there is no limit to life in open-ocean sediment and (ii) a significant amount of oxygen reaches through the sediment to the upper oceanic crust. This "deep aerobic biosphere" inhabits the sediment throughout up to ~37 percent of the world's oceans. The remaining ~63 percent of the oceans is comprised of higher productivity areas that contain the "deep anaerobic biosphere". In 2012, during IODP Expedition 337, the Japanese drill ship Chikyu explored coal-bearing sediments down to 2,466 meters below the seafloor off the Shimokita Peninsula, Japan. Geochemical and microbiological analyses consistently showed the occurrence of methane-producing communities associated with the coal beds. Cell concentrations in deep sediments were notably lower than those expected from the global regression line, implying that the bottom of the deep biosphere is approached in these beds. Taxonomic composition of the deep coal-bearing communities profoundly differs from those in shallower marine sediments and instead resembles organotrophic communities in forest soils. These findings suggest that the terrigenous microbial ecosystem has been partly retained from the original depositional setting over 20 million years and contributed to deep carbon cycling ever since.

Open cycle ocean thermal energy conversion system

DOEpatents

Wittig, J. Michael

1980-01-01

An improved open cycle ocean thermal energy conversion system including a flash evaporator for vaporizing relatively warm ocean surface water and an axial flow, elastic fluid turbine having a vertical shaft and axis of rotation. The warm ocean water is transmitted to the evaporator through a first prestressed concrete skirt-conduit structure circumferentially situated about the axis of rotation. The unflashed warm ocean water exits the evaporator through a second prestressed concrete skirt-conduit structure located circumferentially about and radially within the first skirt-conduit structure. The radially inner surface of the second skirt conduit structure constitutes a cylinder which functions as the turbine's outer casing and obviates the need for a conventional outer housing. The turbine includes a radially enlarged disc element attached to the shaft for supporting at least one axial row of radially directed blades through which the steam is expanded. A prestressed concrete inner casing structure of the turbine has upstream and downstream portions respectively situated upstream and downstream from the disc element. The radially outer surfaces of the inner casing portions and radially outer periphery of the axially interposed disc cooperatively form a downwardly radially inwardly tapered surface. An annular steam flowpath of increasing flow area in the downward axial direction is radially bounded by the inner and outer prestressed concrete casing structures. The inner casing portions each include a transversely situated prestressed concrete circular wall for rotatably supporting the turbine shaft and associated structure. The turbine blades are substantially radially coextensive with the steam flowpath and receive steam from the evaporator through an annular array of prestressed concrete stationary vanes which extend between the inner and outer casings to provide structural support therefor and impart a desired flow direction to the steam.

Coherent Sea Ice Variations in the Nordic Seas and Abrupt Greenland Climate Changes over Dansgaard-Oeschger Cycles

NASA Astrophysics Data System (ADS)

Sadatzki, H.; Berben, S.; Dokken, T.; Stein, R.; Fahl, K.; Jansen, E.

2016-12-01

Rapid changes in sea ice extent in the Nordic Seas may have played a crucial role in controlling the abruptness of ocean circulation and climate changes associated with Dansgaard-Oeschger (D-O) cycles during the last glacial (Li et al., 2010; Dokken et al., 2013). To investigate the role of sea ice for abrupt climate changes, we produced a sea ice record from the Norwegian Sea Core MD99-2284 at a temporal resolution approaching that of ice core records, covering four D-O cycles at ca. 32-41 ka. This record is based on the sea ice diatom biomarker IP25, open-water phytoplankton biomarker dinosterol and semi-quantitative phytoplankton-IP25 (PIP25) estimates. A detailed tephrochronology of MD99-2284 corroborates the tuning-based age model and independently constrains the GS9/GIS8 transition, allowing for direct comparison between our sediment and ice core records. For cold stadials we find extremely low fluxes of total organic carbon, dinosterol and IP25, which points to a general absence of open-water phytoplankton and ice algae production under a near-permanent sea ice cover. For the interstadials, in turn, all biomarker fluxes are strongly enhanced, reflecting a highly productive sea ice edge situation and implying largely open ocean conditions for the eastern Nordic Seas. As constrained by three tephra layers, we observe that the stadial-interstadial sea ice decline was rapid and may have induced a coeval abrupt northward shift in the Greenland precipitation moisture source as recorded in ice cores. The sea ice retreat also facilitated a massive heat release through deep convection in the previously stratified Nordic Seas, generating atmospheric warming of the D-O events. We thus conclude that rapid changes in sea ice extent in the Nordic Seas amplified oceanic reorganizations and were a key factor in controlling abrupt Greenland climate changes over D-O cycles. Dokken, T.M. et al., 2013. Paleoceanography 28, 491-502 Li, C. et al., 2010. Journ. Clim. 23, 5457-5475

The CARIACO Ocean Time-Series: two decades of oceanographic observations to understand linkages between biogeochemistry, ecology, and long-term environmental variability.

NASA Astrophysics Data System (ADS)

Lorenzoni, L.; Muller-Karger, F. E.; Rueda-Roa, D. T.; Thunell, R.; Scranton, M. I.; Taylor, G. T.; benitez-Nelson, C. R.; Montes, E.; Astor, Y. M.; Rojas, J.

2016-02-01

The CARIACO Ocean Time-Series project, located in the Cariaco Basin off the coast of Venezuela, seeks to understand relationships between hydrography, primary production, community composition, microbial activity, particle fluxes, and element cycling in the water column, and how variations in these processes are preserved in sediments accumulating in this anoxic basin. CARIACO uses autonomous and shipboard measurements to understand ecological and biogeochemical changes and how these relate to regional and global climatic/ocean variability. CARIACO is a model for national ocean observing programs in Central/South America, and has been developed as a community facility platform with open access to all data (http://imars.marine.usf.edu/cariaco). Research resulting from this program has contributed to knowledge about the decomposition and cycling of particles, the biological pump, and to our understanding of the ecology and oceanography of oxygen minimum zones. Despite this basin being anoxic below 250m, remineralization rates of organic matter are comparable to those in well oxygenated waters. A dynamic microbial community significantly influences carbon and nutrient biogeochemical cycling throughout the water column. Since 1995, declining particulate organic carbon fluxes have been measured throughout the water column using sediment traps, likely in response to declining Chl-a concentrations and smaller phytoplankton which have replaced the larger taxa over the past decade. This community shift appears to be caused by regional changes in the physical regime. CARIACO also recorded marked long-term changes in surface and deep DIC in response to a combination of factors including surface water warming. The observations of CARIACO highlight the importance of a sustained, holistic approach to studying biodiversity, ecology and the marine carbon cycle to predict potential impacts of climate change on the ocean's ecosystem services and carbon sequestration efficiency.

Seasonal-to-Interannual Variability in Antarctic Sea-Ice Dynamics, and Its Impact on Surface Fluxes and Water Mass Production

NASA Technical Reports Server (NTRS)

Drinkwater, Mark R.

1999-01-01

Strong seasonal and interannual signals in Antarctic bottom-water outflow remain unexplained yet are highly correlated with anomalies in net sea-ice growth in coastal polynyas. The mechanisms responsible for driving salination and replenishment and rejuvenation of the dense shelf "source" waters likely also generate pulses of bottom water outflow. The objective of this research is to investigate time-scales of variability in the dynamics of sea-ice in the Southern Ocean in order to determine the primary sites for production of dense shelf waters. We are using a merged satellite/buoy sea-ice motion data set for the period 1978-present day to compute the dynamics of opening and closing of coastal polynyas over the continental shelf. The Ocean Circulation and Climate Advanced Model (OCCAM) ocean general circulation model with coupled sea-ice dynamics is presently forced using National Center for Environmental Prediction (NCEP) data to simulate fluxes and the salination impact of the ocean shelf regions. This work is relevant in the context of measuring the influence of polar sea-ice dynamics upon polar ocean characteristics, and thereby upon global thermohaline ocean circulation. Interannual variability in simulated net freezing rate in the Southern Weddell Sea is shown for the period 1986-1993. There is a pronounced maximum of ice production in 1988 and minimum in 1991 in response to anomalies in equatorward meridional wind velocity. This follows a similar approximate 8-year interannual cycle in Sea Surface Temperature (SST) and satellite-derived ice-edge anomalies reported elsewhere as the "Antarctic Circumpolar Wave." The amplitude of interannual fluctuations in annual net ice production are about 40% of the mean value, implying significant interannual variance in brine rejection and upper ocean heat loss. Southward anomalies in wind stress induce negative anomalies in open water production, which are observed in passive microwave satellite images. Thus, cycles of enhanced poleward wind stress reduce ice growth by compacting the ice along the coastline and closing open water in leads and polynyas. Model simulations confirm that years of low ice production, such as 1991, coincide with years of lower than normal bottom water outflow. Future plans include the assimilation of satellite ice concentrations and ice drift dynamics to more accurately constrain boundary conditions in the model.

Aquarius: An Instrument to Monitor Sea Surface Salinity from Space

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Lagerloef, G. S .E.; Colomb, R.; Yueh, S.; Pellerano, F.

2007-01-01

Aquarius is a combined passive/active L-band microwave instrument that is being developed to map the salinity field at the surface of the ocean from space. The data will support studies of the coupling between ocean circulation, global water cycle, and climate. Aquarius is part of the Aquarius/SAC-D mission, which is a partnership between the U.S. (National Aeronautics and Space Administration) and Argentina (CONAE). The primary science objective of this mission is to monitor the seasonal and interannual variation of the large-scale features of the surface salinity field in the open ocean with a spatial resolution of 150 km and a retrieval accuracy of 0.2 psu globally on a monthly basis.

Local Atmospheric Response to an Open-Ocean Polynya in a High-Resolution Climate Model

DOE PAGES

Weijer, Wilbert; Veneziani, Milena; Stössel, Achim; ...

2017-03-01

For this scientific paper, we study the atmospheric response to an open-ocean polynya in the Southern Ocean by analyzing the results from an atmospheric and oceanic synoptic-scale resolving Community Earth System Model (CESM) simulation. While coarser-resolution versions of CESM generally do not produce open-ocean polynyas in the Southern Ocean, they do emerge and disappear on interannual timescales in the synoptic-scale simulation. This provides an ideal opportunity to study the polynya’s impact on the overlying and surrounding atmosphere. This has been pursued here by investigating the seasonal cycle of differences of surface and air-column variables between polynya and non-polynya years. Ourmore » results indicate significant local impacts on turbulent heat fluxes, precipitation, cloud characteristics, and radiative fluxes. In particular, we find that clouds over polynyas are optically thicker and higher than clouds over sea ice during non-polynya years. Although the lower albedo of polynyas significantly increases the net shortwave absorption, the enhanced cloud brightness tempers this increase by almost 50%. Also, in this model, enhanced longwave radiation emitted from the warmer surface of polynyas is balanced by stronger downwelling fluxes from the thicker cloud deck. Impacts are found to be sensitive to the synoptic wind direction. Strongest regional impacts are found when northeasterly winds cross the polynya and interact with katabatic winds. Finally, surface air pressure anomalies over the polynya are only found to be significant when cold, dry air masses strike over the polynya, i.e. in case of southerly winds.« less

Local Atmospheric Response to an Open-Ocean Polynya in a High-Resolution Climate Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weijer, Wilbert; Veneziani, Milena; Stössel, Achim

For this scientific paper, we study the atmospheric response to an open-ocean polynya in the Southern Ocean by analyzing the results from an atmospheric and oceanic synoptic-scale resolving Community Earth System Model (CESM) simulation. While coarser-resolution versions of CESM generally do not produce open-ocean polynyas in the Southern Ocean, they do emerge and disappear on interannual timescales in the synoptic-scale simulation. This provides an ideal opportunity to study the polynya’s impact on the overlying and surrounding atmosphere. This has been pursued here by investigating the seasonal cycle of differences of surface and air-column variables between polynya and non-polynya years. Ourmore » results indicate significant local impacts on turbulent heat fluxes, precipitation, cloud characteristics, and radiative fluxes. In particular, we find that clouds over polynyas are optically thicker and higher than clouds over sea ice during non-polynya years. Although the lower albedo of polynyas significantly increases the net shortwave absorption, the enhanced cloud brightness tempers this increase by almost 50%. Also, in this model, enhanced longwave radiation emitted from the warmer surface of polynyas is balanced by stronger downwelling fluxes from the thicker cloud deck. Impacts are found to be sensitive to the synoptic wind direction. Strongest regional impacts are found when northeasterly winds cross the polynya and interact with katabatic winds. Finally, surface air pressure anomalies over the polynya are only found to be significant when cold, dry air masses strike over the polynya, i.e. in case of southerly winds.« less

Earth 2075 (CO2) - can Ocean-Amplified Carbon Capture (oacc) Impart Atmospheric CO2-SINKING Ability to CCS Fossil Energy?

NASA Astrophysics Data System (ADS)

Fry, R.; Routh, M.; Chaudhuri, S.; Fry, S.; Ison, M.; Hughes, S.; Komor, C.; Klabunde, K.; Sethi, V.; Collins, D.; Polkinghorn, W.; Wroobel, B.; Hughes, J.; Gower, G.; Shkolnik, J.

2017-12-01

Previous attempts to capture atmospheric CO2 by algal blooming were stalled by ocean viruses, zooplankton feeding, and/or bacterial decomposition of surface blooms, re-releasing captured CO2 instead of exporting it to seafloor. CCS fossil energy coupling could bypass algal bloom limits—enabling capture of 10 GtC/yr atmospheric CO2 by selective emiliania huxleyi (EHUX) blooming in mid-latitude open oceans, far from coastal waters and polar seas. This could enable a 500 GtC drawdown, 350 ppm restoration by 2050, 280 ppm CO2 by 2075, and ocean pH 8.2. White EHUX blooms could also reflect sunlight back into outer space and seed extra ocean cloud cover, via DMS release, to raise albedo 1.8%—restoring preindustrial temperature (ΔT = 0°C) by 2030. Open oceans would avoid post-bloom anoxia, exclusively a coastal water phenomenon. The EHUX calcification reaction initially sources CO2, but net sinking prevails in follow-up equilibration reactions. Heavier-than-water EHUX sink captured CO2 to the sea floor before surface decomposition occurs. Seeding EHUX high on their nonlinear growth curve could accelerate short-cycle secondary open-ocean blooming—overwhelming mid-latitude viruses, zooplankton, and competition from other algae. Mid-latitude "ocean deserts" exhibit low viral, zooplankton, and bacterial counts. Thermocline prevents nutrient upwelling that would otherwise promote competing algae. Adding nitrogen nutrient would foster exclusive EHUX blooming. Elevated EHUX seed levels could arise from sealed, pH-buffered, floating, seed-production bioreactors infused with 10% CO2 from carbon feedstock supplied by inland CCS fossil power plants capturing 90% of emissions as liquid CO2. Deep-water SPAR platforms extract natural gas from beneath the sea floor. On-platform Haber and pH processing could convert extracted CH4 to buffered NH4+ nutrient, enabling ≥0.7 GtC/yr of bioreactor seed production and 10 GtC/yr of amplified secondary open-ocean CO2 capture—making CCS fossil energy 1400% carbon negative.

Will open ocean oxygen stress intensify under climate change?

NASA Astrophysics Data System (ADS)

Gnanadesikan, A.; Dunne, J. P.; John, J.

2011-07-01

Global warming is expected to reduce oxygen solubility and vertical exchange in the ocean, changes which would be expected to result in an increase in the volume of hypoxic waters. A simulation made with a full earth system model with dynamical atmosphere, ocean, sea ice and biogeochemical cycling shows that this holds true if the condition for hypoxia is set relatively high. However, the volume of the most hypoxic waters does not increase under global warming, as these waters actually become more oxygenated. We show that the rise in oxygen is associated with a drop in ventilation time. A term-by-term analysis within the least oxygenated waters shows an increased supply of oxygen due to lateral diffusion. compensating an increase in remineralization within these highly hypoxic waters. This lateral diffusive flux is the result of an increase of ventilation along the Chilean coast, as a drying of the region under global warming opens up a region of wintertime convection in our model.

Mangroves, a major source of dissolved organic carbon to the oceans

NASA Astrophysics Data System (ADS)

Dittmar, Thorsten; Hertkorn, Norbert; Kattner, Gerhard; Lara, RubéN. J.

2006-03-01

Organic matter, which is dissolved in low concentrations in the vast waters of the oceans, contains a total amount of carbon similar to atmospheric carbon dioxide. To understand global biogeochemical cycles, it is crucial to quantify the sources of marine dissolved organic carbon (DOC). We investigated the impact of mangroves, the dominant intertidal vegetation of the tropics, on marine DOC inventories. Stable carbon isotopes and proton nuclear magnetic resonance spectroscopy showed that mangroves are the main source of terrigenous DOC in the open ocean off northern Brazil. Sunlight efficiently destroyed aromatic molecules during transport offshore, removing about one third of mangrove-derived DOC. The remainder was refractory and may thus be distributed over the oceans. On a global scale, we estimate that mangroves account for >10% of the terrestrially derived, refractory DOC transported to the ocean, while they cover only <0.1% of the continents' surface.

Production of giant marine diatoms and their export at oceanic frontal zones: Implications for Si and C flux from stratified oceans

NASA Astrophysics Data System (ADS)

Kemp, A. E. S.; Pearce, R. B.; Grigorov, I.; Rance, J.; Lange, C. B.; Quilty, P.; Salter, I.

2006-12-01

From a synthesis of recent oceanic observations and paleo-data it is evident that certain species of giant diatoms including Rhizosolenia spp. Thalassiothrix spp. and Ethmodiscus rex may become concentrated at oceanic frontal zones and subsequently form episodes of mass flux to the sediment. Within the nutrient bearing waters advecting towards frontal boundaries, these species are generally not dominant, but they appear selectively segregated at fronts, and thus may dominate the export flux. Ancient Thalassiothrix diatom mat deposits in the eastern equatorial Pacific and beneath the Polar Front in the Southern Ocean record the highest open ocean sedimentation rates ever documented and represent vast sinks of silica and carbon. Several of the species involved are adapted to a stratified water column and may thrive in Deep Chlorophyll Maxima. Thus in oceanic regions and/or at times prone to enhanced surface water stratification (e.g., during meltwater pulses) they provide a mechanism for generating substantial biomass at depth and its subsequent export with concomitant implications for Si export and C drawdown. This ecology has important implications for ocean biogeochemical models suggesting that more than one diatom "functional type" should be used. In spite of the importance of these giant diatoms for biogeochemical cycling, their large size coupled with the constraints of conventional oceanographic survey schemes and techniques means that they are undersampled. An improved insight into these key species will be an important prerequisite for enhancing our understanding of marine biogeochemical cycling and for assessing the impacts of climate change on ocean export production.

Carbon Cycle in South China Sea: Flux, Controls and Global Implications

NASA Astrophysics Data System (ADS)

Dai, M.; Cao, Z.; Yang, W.; Guo, X.; Yin, Z.; Gan, J.

2016-12-01

The contemporary coastal ocean is generally seen as a significant CO2 sink of 0.2-0.4 Pg C/yr at the global scale. However, mechanistic understanding of the coastal ocean carbon cycle remains limited, leading to the unanswered question of why some coastal systems are sources while others are sinks of atmospheric CO2. As the largest marginal sea of Northern Pacific, the South China Sea (SCS) is a mini-ocean with wide shelves in both its southern and northern parts. Its northern shelf, which receives significant land inputs from the Pearl River, a world major river, can be categorized as a River-Dominated Margin (RioMar) during peak discharges, and is characterized as a CO2 sink to the atmosphere. The SCS basin is identified as an Ocean-Dominated Margin (OceMar) and a CO2 source. OceMar is characterized by exchange with the open ocean via a two-dimensional (at least) process, i.e., the horizontal intrusion of open ocean water and subsequent vertical mixing and upwelling. Depending on the different ratios of dissolved inorganic carbon (DIC) and nutrients from the source waters into the continental margins, the relative consumption or removal bwtween DIC and nutrients, when being transported into the euphotic zones where biogeochemical processes take over, determines the CO2 fluxes. Thus, excess DIC relative to nutrients existing in the upper layer will lead to CO2 degassing. The CO2 fluxes in both RioMars and OceMars can be quantified using a semi-analytical diagnostic approach by coupling the physical dynamics and biogeochemical processes. We extended our mechanistic studies in the SCS to other OceMars including the Caribbean Sea, the Arabian Sea, and the upwelling system off the Oregon-California coast, and RioMars including the East China Sea and Amazon River plume to demonstrate the global implications of our SCS carbon studies.

PhyLM: A Mission Design Concept for an Optical/Lidar Instrument to Measure Ocean Productivity and Aerosols from Space

NASA Technical Reports Server (NTRS)

Gervin, Janette C.; Behrenfeld, Michael; McClain, Charles R.; Spinhirne, James; Purves, Lloyd; Wood, H. John; Roberto, Michael R.

2004-01-01

The Physiology Lidar-Multispectral Mission (PhyLM) is intended to explore the complex ecosystems of our global oceans. New "inversion" methods and improved understanding of marine optics have opened the door to quantifying a range of critical ocean properties. This new information could revolutionize our understanding of global ocean processes, such as phytoplankton growth, harmful algal blooms, carbon fluxes between major pools and the productivity equation. The new science requires new measurements not addressed by currently planned space missions. PhyLM will combine active and advanced passive remote sensing technologies to quantify standing stocks and fluxes of climate-critical components of the Ocean carbon cycle to meet these science providing multispectral bands from the far UV through the near infrared (340 - 1250 nm) at a ground resolution of 250 m. Improved detectors, filters, mirrors, digitization and focal plane design will offer an overall higher-quality data product. The unprecedented accuracy and precision of the absolute water-leaving radiances will support inversion- based quantification of an expanded set of ocean carbon cycle components. The dual- wavelength (532 & 1064 nm) Nd:Yag Lidar will enhance the accuracy and precision of the passive data by providing aerosol profiles for atmospheric correction and coincident active measurements of backscattering. The Lidar will also examine dark-side fluorescence as an additional approach to quantifying phytoplankton biomass in highly productive regions.

Large-scale stress factors affecting coral reefs: open ocean sea surface temperature and surface seawater aragonite saturation over the next 400 years

NASA Astrophysics Data System (ADS)

Meissner, K. J.; Lippmann, T.; Sen Gupta, A.

2012-06-01

One-third of the world's coral reefs have disappeared over the last 30 years, and a further third is under threat today from various stress factors. The main global stress factors on coral reefs have been identified as changes in sea surface temperature (SST) and changes in surface seawater aragonite saturation (Ωarag). Here, we use a climate model of intermediate complexity, which includes an ocean general circulation model and a fully coupled carbon cycle, in conjunction with present-day observations of inter-annual SST variability to investigate three IPCC representative concentration pathways (RCP 3PD, RCP 4.5, and RCP 8.5), and their impact on the environmental stressors of coral reefs related to open ocean SST and open ocean Ωarag over the next 400 years. Our simulations show that for the RCP 4.5 and 8.5 scenarios, the threshold of 3.3 for zonal and annual mean Ωarag would be crossed in the first half of this century. By year 2030, 66-85% of the reef locations considered in this study would experience severe bleaching events at least once every 10 years. Regardless of the concentration pathway, virtually every reef considered in this study (>97%) would experience severe thermal stress by year 2050. In all our simulations, changes in surface seawater aragonite saturation lead changes in temperatures.

An original mode of symbiosis in open ocean plankton.

PubMed

Decelle, Johan; Probert, Ian; Bittner, Lucie; Desdevises, Yves; Colin, Sébastien; de Vargas, Colomban; Galí, Martí; Simó, Rafel; Not, Fabrice

2012-10-30

Symbiotic relationships are widespread in nature and are fundamental for ecosystem functioning and the evolution of biodiversity. In marine environments, photosymbiosis with microalgae is best known for sustaining benthic coral reef ecosystems. Despite the importance of oceanic microbiota in global ecology and biogeochemical cycles, symbioses are poorly characterized in open ocean plankton. Here, we describe a widespread symbiotic association between Acantharia biomineralizing microorganisms that are abundant grazers in plankton communities, and members of the haptophyte genus Phaeocystis that are cosmopolitan bloom-forming microalgae. Cophylogenetic analyses demonstrate that symbiont biogeography, rather than host taxonomy, is the main determinant of the association. Molecular dating places the origin of this photosymbiosis in the Jurassic (ca. 175 Mya), a period of accentuated marine oligotrophy. Measurements of intracellular dimethylated sulfur indicate that the host likely profits from antioxidant protection provided by the symbionts as an adaptation to life in transparent oligotrophic surface waters. In contrast to terrestrial and marine symbioses characterized to date, the symbiont reported in this association is extremely abundant and ecologically active in its free-living phase. In the vast and barren open ocean, partnership with photosymbionts that have extensive free-living populations is likely an advantageous strategy for hosts that rely on such interactions. Discovery of the Acantharia-Phaeocystis association contrasts with the widely held view that symbionts are specialized organisms that are rare and ecologically passive outside the host.

Single-cell genomics reveals co-metabolic interactions within uncultivated Marine Group A bacteria

NASA Astrophysics Data System (ADS)

Hawley, A. K.; Hallam, S. J.

2016-02-01

Marine Group A (MGA) bacteria represent a ubiquitous and abundant candidate phylum enriched in oxygen minimum zones (OMZs) and the deep ocean. Despite MGA prevalence little is known about their ecology and biogeochemistry. Here we chart the metabolic potential of 26 MGA single-cell amplified genomes sourced from different environments spanning ecothermodynamic gradients including open ocean waters, OMZs and methanogenic environments including a terephthalate-degrading bioreactor. Metagenomic contig recruitment to SAGs combined with tetra-nucleotide frequency distribution patterns resolved nine MGA population genome bins. All population genomes exhibited genomic streamlining with open ocean MGA being the most reduced. Different strategies for carbohydrate utilization, carbon fixation energy metabolism and respiratory pathways were identified between population genome bins, including various roles in the nitrogen and sulfur cycles. MGA inhabiting OMZ oxyclines encoded genes for partial denitrification with potential to feed into anammox and nitrification as well as a polysulfide reductase with a potential role in the cryptic sulfur cycle. MGA inhabiting anoxic waters, encoded NiFe hydrogenase and nitrous oxide reductase with the potential to complete partial denitrification pathways previously linked to sulfur oxidation in SUP05 bacteria. MGA from methanogenic environments encoded genes mediating cascading syntrophic interactions with fatty acid degraders and methanogens including reverse electron transport potential. The MGA phylum appears to have evolved alternative metabolic innovations adapting specific subgroups to occupy specific niches along ecothermodynamic gradients. Additionally, expression of MGA genes from different OMZ environments supports that these subgroups manifest an increasing propensity for co-metabolic interactions under energy limiting conditions that mandates a cooperative mode of existence with important implications for C, N and S cycling in marine ecosystems.

Southern Ocean Iron Experiment (SOFex)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coale, Kenneth H.

The Southern Ocean Iron Experiment (SOFeX) was an experiment decades in the planning. It's implementation was among the most complex ship operations that SIO has been involved in. The SOFeX field expedition was successful in creating and tracking two experimentally enriched areas of the Southern Ocean, one characterized by low silicic acid, one characterized by high silicic acid. Both experimental sites were replete with abundant nitrate. About 100 scientists were involved overall. The major findings of this study were significant in several ways: (1) The productivity of the southern ocean is limited by iron availability. (2) Carbon uptake and fluxmore » is therefore controlled by iron availability (3) In spite of low silicic acid, iron promotes non-silicious phytoplankton growth and the uptake of carbon dioxide. (4) The transport of fixed carbon from the surface layers proceeds with a C:N ratio that would indicate differential remineralization of nitrogen at shallow depths. (5) These finding have major implications for modeling of carbon export based on nitrate utilization. (6) The general results of the experiment indicate that, beyond other southern ocean enrichment experiments, iron inputs have a much wider impact of productivity and carbon cycling than previously demonstrated. Scientific presentations: Coale, K., Johnson, K, Buesseler, K., 2002. The SOFeX Group. Eos. Trans. AGU 83(47) OS11A-0199. Coale, K., Johnson, K. Buesseler, K., 2002. SOFeX: Southern Ocean Iron Experiments. Overview and Experimental Design. Eos. Trans. AGU 83 (47) OS22D-01. Buesseler, K.,et al. 2002. Does Iron Fertilization Enhance Carbon Sequestration? Particle flux results from the Southern Ocean Iron Experiment. Eos. Trans. AGU 83 (47), OS22D-09. Johnson, K. et al. 2002. Open Ocean Iron Fertilization Experiments From IronEx-I through SOFeX: What We Know and What We Still Need to Understand. Eos. Trans. AGU 83 (47), OS22D-12. Coale, K. H., 2003. Carbon and Nutrient Cycling During the Southern Ocean Iron Enrichment Experiments. Seattle, WA. Geological Society of America. Coale, K., 2003. Open Ocean Iron Enrichment Experiments: What they have told us, what they have not. American Society for Limnology and Oceanography and The Oceanography Society, Honolulu, February 2004. Coale, K., 2004. Recent Research from the Southern Ocean Iron Experiment (SOFeX), in Taking the Heat: What is the impact of ocean fertilization on climate and ocean ecology? Science of earth and sky. AAAS, February 12-16, Seattle, WA« less

Evolution of organic carbon burial in the Global Ocean during the Neogene

NASA Astrophysics Data System (ADS)

LI, Z.; Zhang, Y.

2017-12-01

Although only a small fraction of the organic carbon (OC) that rains from surface waters is eventually buried in the sediments, it is a process that controls the organic sub-cycle of the long-term carbon cycle, and the key for atmospheric O2, CO2 and nutrient cycling. Here we constrain the spatiotemporal variability of OC burial by quantifying the total organic carbon (TOC) mass accumulation rate (MAR) over the Neogene (23.0-2.6 Ma) by compiling the TOC, age model and sediment density data from sites retrieved by the Deep Sea Drilling Program, Ocean Drilling Program, and Integrated Ocean Drilling Program. We screened all available sites which yielded 80 sites with adequate data quality, covering all major ocean basins and sedimentary depositional environments. All age models are updated to the GTS 2012 timescale so the TOC MAR records from different sites are comparable. Preliminary results show a clear early Miocene peak of OC burial in many sites related to high sediment flux which might reflect the orogenic uplift and/or glacier erosion. Places that receive high influx of terrigenous inputs become "hotspots" for Neogene burial of OC. At "open ocean" sites, OC burial seems to be more impacted by marine productivity changes, with a pronounced increase during the middle Miocene "Monterey Formation" and late Miocene - early Pliocene "Biogenic Bloom". Upon the completion of the data collection, we will further explore the regional and global OC burial in the context of tectonic uplift, climate change and the evolution of primary producers and consumers during the last 23 million years of Earth history.

Extending the Precipitation Map Offshore Using Daily and 3-Hourly Combined Precipitation Estimates

NASA Technical Reports Server (NTRS)

Huffman, George J.; Adler, Robert F.; Bolvin, David T.; Curtis, Scott; Einaudi, Franco (Technical Monitor)

2001-01-01

One of the difficulties in studying landfalling extratropical cyclones along the Pacific Coast is the lack of antecedent data over the ocean, including precipitation. Recent research on combining various satellite-based precipitation estimates opens the possibility of realistic precipitation estimates on a global 1 deg. x 1 deg. latitude-longitude grid at the daily or even 3-hourly interval. The goal in this work is to provide quantitative precipitation estimates that correctly represent the precipitation- related variables in the hydrological cycle: surface accumulations (fresh-water flux into oceans), frequency and duration statistics, net latent heating, etc.

Sources of reactive nitrogen in marine aerosol over the Northwest Pacific Ocean in spring

NASA Astrophysics Data System (ADS)

Luo, Li; Kao, Shuh-Ji; Bao, Hongyan; Xiao, Huayun; Xiao, Hongwei; Yao, Xiaohong; Gao, Huiwang; Li, Jiawei; Lu, Yangyang

2018-05-01

Atmospheric deposition of long-range transport of anthropogenic reactive nitrogen (Nr, mainly comprised of NHx, NOy and water-soluble organic nitrogen, WSON) from continents may have profound impact on marine biogeochemistry. In addition, surface ocean dissolved organic nitrogen (DON) may also contribute to aerosol WSON in the overlying atmosphere. Despite the importance of off-continent dispersion and Nr interactions at the atmosphere-ocean boundary, our knowledge of the sources of various nitrogen species in the atmosphere over the open ocean remains limited due to insufficient observations. We conducted two cruises in the spring of 2014 and 2015 from the coast of China through the East China seas (ECSs, i.e. the Yellow Sea and East China Sea) to the open ocean (i.e. the Northwest Pacific Ocean, NWPO). Concentrations of water-soluble total nitrogen (WSTN), NO3- and NH4+, as well as the δ15N of WSTN and NO3- in marine aerosol, were measured during both cruises. In the spring of 2015, we also analysed the concentrations and δ15N of NO3- and the DON of surface seawater (SSW; at a depth of 5 m) along the cruise track. Aerosol NO3-, NH4+ and WSON decreased logarithmically (1-2 orders of magnitude) with distance from the shore, reflecting strong anthropogenic emission sources of NO3-, NH4+ and WSON in China. Average aerosol NO3- and NH4+ concentrations were significantly higher in 2014 (even in the remote NWOP) than in 2015 due to the stronger wind field in 2014, underscoring the role of the Asian winter monsoon in the seaward transport of anthropogenic NO3- and NH4+. However, the background aerosol WSON over the NWPO in 2015 (13.3 ± 8.5 nmol m-3) was similar to that in 2014 (12.2 ± 6.3 nmol m-3), suggesting an additional non-anthropogenic WSON source in the open ocean. Obviously, marine DON emissions should be considered in model and field assessments of net atmospheric WSON deposition in the open ocean. This study contributes information on parallel isotopic marine DON composition and aerosol Nr datasets, but more research is required to explore complex Nr sources and deposition processes in order to advance our understanding of anthropogenic influences on the marine nitrogen cycle and nitrogen exchange at land-ocean and atmosphere-ocean interfaces.

Investigating A Unique Open Ocean Geochemical Record Of the End Triassic Mass Extinction from Panthalassa

NASA Astrophysics Data System (ADS)

Marroquín, S. M.; Gill, B. C.; Them, T. R., II; Trabucho-Alexandre, J. P.; Aberhan, M.; Owens, J. D.; Gröcke, D. R.; Caruthers, A. H.

2017-12-01

The end-Triassic mass extinction ( 201 Ma) was a time of intense disturbance for marine communities. This event is estimated to have produced as much as a loss of 80% of known marine species. The protracted interval of elevated extinction rates is also characterized by a major carbon cycle perturbation and potentially widespread oxygen deficiency within the oceans. While the causes of extinction and environmental feedbacks are still debated it is hypothesized to have been triggered by massive volcanism associated with the Central Atlantic Magmatic Province flood basalts. However, our understanding of the Latest Triassic-Earliest Jurassic interval is limited due to the lack of well-preserved stratigraphic successions outside of the Tethys Ocean (present day Europe), with most of the records from epicontinental and marginal marine settings. To expand our understanding of this critical interval, our study seeks to document biological and environmental changes elsewhere. Specifically, we document and reconstruct these changes in the equatorial Panthalassan Ocean. We will present new data from a sedimentary succession preserved in the Wrangell Mountains of Alaska that spans the Late Triassic through Early Jurassic. The sedimentary succession represents a mixed carbonate-siliciclastic ramp that was deposited at tropical latitudes, adjacent to an island arc in the open Panthalassan Ocean. This succession affords a unique view of open marine conditions, and also holds the potential for excellent temporal control as it contains abundant ash layers throughout, as well as, key ammonite and bivalve fossil occurrences that provide biostratigraphic control. We will present an integrated geochemical and paleontological record from this site using several geochemical proxies (carbon, δ13Ccarb and % total organic carbon, sulfur, δ34S, as well as pyrite contents and iron speciation) along with ammonite and bivalve occurrence data to reconstruct the record of environmental and biological change within the open Panthalassan Ocean, and relate these data to existing marine records of the end-Triassic extinction.

Atlantic ocean surface waters buffer declining atmospheric concentrations of persistent organic pollutants.

PubMed

Nizzetto, Luca; Lohmann, Rainer; Gioia, Rosalinda; Dachs, Jordi; Jones, Kevin C

2010-09-15

Decreasing environmental concentrations of some persistent organic pollutants (POPs) have been observed at local or regional scales in continental areas after the implementation of international measures to curb primary emissions. A decline in primary atmospheric emissions can result in re-emissions of pollutants from the environmental capacitors (or secondary sources) such as soils and oceans. This may be part of the reason why concentrations of some POPs such as polychlorinated biphenyls (PCBs) have not declined significantly in the open oceanic areas, although re-emission of POPs from open ocean water has barely been documented. In contrast, results from this study show that several polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) have undergone a marked decline (2-3 orders of magnitude for some homologues) over a major portion of the remote oligotrophic Atlantic Ocean. The decline appears to be faster than that observed over continental areas, implicating an important role of oceanic geochemical controls on levels and cycling of some POPs. For several lower chlorinated PCDD/Fs, we observed re-emission from surface water back to the atmosphere. An assessment of the effectiveness of the main sink processes highlights the role of degradation in surface waters as potentially key to explaining the different behavior between PCDD/Fs and PCBs and controlling their overall residence time in the ocean/atmosphere system. This study provides experimental evidence that the ocean has a buffering capacity - dependent on individual chemicals - which moderates the rate at which the system will respond to an underlying change in continental emissions.

The Diurnal Cycle in TOGA-COARE: Regional Scale Model Simulations

NASA Technical Reports Server (NTRS)

Tao, W.-K.; Jia, Y.

1999-01-01

The diurnal variation of precipitation processes over the tropics is a well-known phenomenon and has been studied using surface rainfall data, radar reflectivity data, and satellite-derived cloudiness and precipitation. Recently, analyzed observations from Tropical Oceans and Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) in the tropical western Pacific ocean to study the relevant mechanisms producing diurnal variation of precipitation. They found that the diurnal Sea surface temperature (SST) cycle is important for afternoon showers in the undisturbed periods and diurnal radiative processes for nocturnal rainfall. Cloud resolving models (CRMS) have been used to determine the mechanisms associated with diurnal variation of precipitating processes. CRMs allow explicit cloud-radiation and air-sea interactive processes. However, CRMs can be only used for idealized simulations (i.e., no feedback between clouds and their embedded large-scale environments; cyclic lateral boundary conditions and idealized initial conditions). In this study, the Penn State/NCAR Mesoscale Model (MM5) with improved physics (i.e., cloud microphysics, radiation, land-soil-vegetation-surface processes, and TOGA COARE flux scheme) and a multiple level nesting technique (covers the TOGA COARE LSA/IFA with a 54 km grid and can nest down to 18, 6 and possibly even 2 km) will be adopted for studying the diurnal variations of rainfall. We will examine precipitation processes over open ocean and over land. We will also perform sensitivity tests to determine how the radiative forcing and diurnal SST cycle affects the development of convection.

The 1994 Arctic Ocean Section. The First Major Scientific Crossing of the Arctic Ocean,

DTIC Science & Technology

1996-09-01

contribute to the international effort to better understand the role of the Arctic Ocean in the global carbon cycle and climate change. Summar...Barium Distributions in the Arctic Ocean ? ........................ 32 Biology and the Carbon Cycle Cycling of Organic Carbon in the Central Arctic...of Heterotrophic Bacteria and Protists in the Arctic Ocean Carbon Cycle............. 40

Sulfate was a trace constituent of Archean seawater.

PubMed

Crowe, Sean A; Paris, Guillaume; Katsev, Sergei; Jones, CarriAyne; Kim, Sang-Tae; Zerkle, Aubrey L; Nomosatryo, Sulung; Fowle, David A; Adkins, Jess F; Sessions, Alex L; Farquhar, James; Canfield, Donald E

2014-11-07

In the low-oxygen Archean world (>2400 million years ago), seawater sulfate concentrations were much lower than today, yet open questions frustrate the translation of modern measurements of sulfur isotope fractionations into estimates of Archean seawater sulfate concentrations. In the water column of Lake Matano, Indonesia, a low-sulfate analog for the Archean ocean, we find large (>20 per mil) sulfur isotope fractionations between sulfate and sulfide, but the underlying sediment sulfides preserve a muted range of δ(34)S values. Using models informed by sulfur cycling in Lake Matano, we infer Archean seawater sulfate concentrations of less than 2.5 micromolar. At these low concentrations, marine sulfate residence times were likely 10(3) to 10(4) years, and sulfate scarcity would have shaped early global biogeochemical cycles, possibly restricting biological productivity in Archean oceans. Copyright © 2014, American Association for the Advancement of Science.

Iron fertilisation and century-scale effects of open ocean dissolution of olivine in a simulated CO2 removal experiment

NASA Astrophysics Data System (ADS)

Hauck, Judith; Köhler, Peter; Wolf-Gladrow, Dieter; Völker, Christoph

2016-02-01

Carbon dioxide removal (CDR) approaches are efforts to reduce the atmospheric CO2 concentration. Here we use a marine carbon cycle model to investigate the effects of one CDR technique: the open ocean dissolution of the iron-containing mineral olivine. We analyse the maximum CDR potential of an annual dissolution of 3 Pg olivine during the 21st century and focus on the role of the micro-nutrient iron for the biological carbon pump. Distributing the products of olivine dissolution (bicarbonate, silicic acid, iron) uniformly in the global surface ocean has a maximum CDR potential of 0.57 gC/g-olivine mainly due to the alkalinisation of the ocean, with a significant contribution from the fertilisation of phytoplankton with silicic acid and iron. The part of the CDR caused by ocean fertilisation is not permanent, while the CO2 sequestered by alkalinisation would be stored in the ocean as long as alkalinity is not removed from the system. For high CO2 emission scenarios the CDR potential due to the alkalinity input becomes more efficient over time with increasing ocean acidification. The alkalinity-induced CDR potential scales linearly with the amount of olivine, while the iron-induced CDR saturates at 113 PgC per century (on average ˜ 1.1 PgC yr-1) for an iron input rate of 2.3 Tg Fe yr-1 (1% of the iron contained in 3 Pg olivine). The additional iron-related CO2 uptake occurs in the Southern Ocean and in the iron-limited regions of the Pacific. Effects of this approach on surface ocean pH are small (\\lt 0.01).

Southern Ocean Bottom Water Characteristics in CMIP5 Models

NASA Astrophysics Data System (ADS)

Heuzé, Céline; Heywood, Karen; Stevens, David; Ridley, Jeff

2013-04-01

The depiction of Southern Ocean deep water properties and formation processes in climate models is an indicator of their capability to simulate future climate, heat and carbon uptake, and sea level rise. Southern Ocean potential temperature and density averaged over 1986-2005 from fifteen CMIP5 climate models are compared with an observed climatology, focusing on bottom water properties. The mean bottom properties are reasonably accurate for half of the models, but the other half may not yet have approached an equilibrium state. Eleven models create dense water on the Antarctic shelf, but it does not spill off and propagate northwards, alternatively mixing rapidly with less dense water. Instead most models create deep water by open ocean deep convection. Models with large deep convection areas are those with a strong seasonal cycle in sea ice. The most accurate bottom properties occur in models hosting deep convection in the Weddell and Ross gyres.

Cadmium cycling in the water column of the Kuroshio-Oyashio Extension region: Insights from dissolved and particulate isotopic composition

NASA Astrophysics Data System (ADS)

Yang, Shun-Chung; Zhang, Jing; Sohrin, Yoshiki; Ho, Tung-Yuan

2018-07-01

We measured dissolved and particulate Cd isotopic composition in the water column of a meridional transect across the Kuroshio-Oyashio Extension region in a Japanese GEOTRACES cruise to investigate the relative influence of physical and biogeochemical processes on Cd cycling in the Northwestern Pacific Ocean. Located at 30-50°N along 165°E, the transect across the extension region possesses dramatic hydrographic contrast. Cold surface water and a relatively narrow and shallow thermocline characterizes the Oyashio Extension region in contrast to a relatively warm and highly stratified surface water and thermocline in the Kuroshio Extension region. The contrasting hydrographic distinction at the study site provides us with an ideal platform to investigate the spatial variations of Cd isotope fractionation systems in the ocean. Particulate samples demonstrated biologically preferential uptake of light Cd isotopes, and the fractionation effect varied dramatically in the surface water of the two regions, with relatively large fractionation factors in the Oyashio region. Based on the relationship of dissolved Cd concentrations and isotopic composition, we found that a closed system fractionation model can reasonably explain the relationship in the Kuroshio region. However, using dissolved Cd isotopic data, either a closed system or steady-state open system fractionation model may explain the relationship in the surface water of the Oyashio region. Particulate δ114/110Cd data further supports that the surface water of the Oyashio region matches a steady-state open system model more closely. Contrary to the surface water, the distribution of potential density exhibits comparable patterns with Cd elemental and isotopic composition in the thermocline and deep water in the two extension regions, showing that physical processes are the dominant forcing controlling Cd cycling in the deep waters. The results demonstrate that Cd isotope fractionation can match either a closed or open system Rayleigh fractionation model, depending on the relative contribution of physical and biogeochemical processes on its cycling.

The Oceanic Cycle and Global Atmospheric Budget of Carbonyl Sulfide.

NASA Astrophysics Data System (ADS)

Weiss, Peter Scott

1995-01-01

A significant portion of stratospheric air chemistry is influenced by the existence of carbonyl sulfide (COS). This ubiquitous sulfur gas represents a major source of sulfur to the stratosphere where it is converted to sulfuric acid aerosol particles. Stratospheric aerosols are climatically important because they scatter incoming solar radiation back to space and are able to increase the catalytic destruction of ozone through gas phase reactions on particle surfaces. COS is primarily formed at the surface of the earth, in both marine and terrestrial environments, and is strongly linked to natural biological processes. However, many gaps in the understanding of the global COS cycle still exist, which has led to a global atmospheric budget that is out of balance by a factor of two or more, and a lack of understanding of how human activity has affected the cycling of this gas. The goal of this study was to focus on COS in the marine environment by investigating production/destruction mechanisms and recalculating the ocean-atmosphere flux. Analytical work was carried out using the electron capture sulfur detector (ECD-S) for gas chromatography. This system was optimized for COS so that air and seawater-equilibrated air samples could be directly injected without preconcentration. This research was carried out on two cruises aboard the NOAA ship Surveyor during long meridional transects between 55^circN and 70 ^circS along 140^circ W in the Pacific Ocean. The major findings of these research activities are: (1) Photoproduction of COS is at a maximum between 313 and 336 nm in natural sunlit waters. Tropical water surface and column production rates are 68 pM/day and 360 nmol/m^2/day, respectively. Antarctic surface and column production rates are 101 pM/day and 620 nmol/m^2/day, respectively. (2) Wide regions of the open ocean were found to be undersaturated with respect to atmospheric equilibrium of COS. The global open ocean sea-air flux of COS was found to be -0.032 (-0.010 to -0.054) which represents a very weak sink of atmospheric COS. (3) Daily COS concentration losses in surface waters were used to determine seawater lifetimes, which agreed to hydrolysis lifetimes to within 15%. (4) Atmospheric COS mixing ratios displayed <5% interhemispheric ratio. However, seasonal variation in the northern hemisphere may have been as high as 10%. (5) A simple steady-state model was developed to predict seasonal cycles of atmospheric COS.

New Carbon Source From Microbial Degradation of Pre-Production Resin Pellets from the North Pacific Gyre

NASA Astrophysics Data System (ADS)

Neal, A.; Mielke, R.; Stam, C. N.; Gonsior, M.; Tsapin, A. I.; Lee, G.; Leftwich, B.; Narayan, R.; Coleman, H.; Argyropoulos, N.; Sheavly, S. B.; Gorby, Y. A.

2011-12-01

Numerous pollutants are transported through the world's oceans that impact oceanic health. Diffuse sources include land-based runoff, atmospheric depositions, shipping industry wastes, and others. Synthetic polymer marine debris is a multi-faceted problem that includes interactions with environmental toxins, carbon cycling systems, ocean surface chemistry, fine minerals deposition, and nano-particles. The impact that synthetic polymer-microbe interactions have on carbon input into the open ocean is poorly understood. Here we demonstrate that both biotic and abiotic processes contribute to degradation of pre-production resin pellets (PRPs), in open ocean environments and new methodologies to determine carbon loss from this synthetic polymer debris. Our data shows that material degradation of environmental polyethylene PRPs can potentially deposit 13 mg/g to 65 mg/g of carbon per PRP into our marine environments. Environmental pre-production resin pellets were collected on the S/V Kaisei cruise in 2009 which covered over 3,000 nautical miles and sampled over 102,000 m3 of the first 15cm of the water column in the Subtropical Convergence Zone of the North Pacific Gyre. Environmental PRP degradation and the role microbial communities play in this was evaluated using a combination of Fourier transform infrared spectroscopy, environmental scanning electron microscopy, scanning transmission electron microscopy, X-ray microtomography, and ArcGIS mapping. More research is needed to understand the environmental impact of this new carbon source arising from synthetic polymers as they degrade in oceanic environments.

Nutrient control of phytoplankton photosynthesis in the western North Atlantic

NASA Technical Reports Server (NTRS)

Platt, Trevor; Sathyendranath, Shubha; Ulloa, Osvaldo; Harrison, William G.; Hoepffner, Nicolas; Goes, Joaquim

1992-01-01

Results from several years of oceanographic cruises are reported which show that the parameters of the photosynthesis-light curve of the flora of the North Sargasso Sea are remarkably constant in magnitude, except during the spring phytoplankton bloom when their magnitudes are noticeably higher. These results are interpreted as providing direct evidence for nutrient control of photosynthesis in the open ocean. The findings also reinforce the plausibility of using biogeochemical provinces to partition the ocean into manageable units for basin- or global-scale analysis. They show that seasonal changes in critical parameter should not be overlooked if robust carbon budgets are to be constructed, and illustrate the value of attacking the parameters that control the key fluxes, rather than the fluxes themselves, when investigating the ocean carbon cycle.

Novel lineages of Prochlorococcus and Synechococcus in the global oceans.

PubMed

Huang, Sijun; Wilhelm, Steven W; Harvey, H Rodger; Taylor, Karen; Jiao, Nianzhi; Chen, Feng

2012-02-01

Picocyanobacteria represented by Prochlorococcus and Synechococcus have an important role in oceanic carbon fixation and nutrient cycling. In this study, we compared the community composition of picocyanobacteria from diverse marine ecosystems ranging from estuary to open oceans, tropical to polar oceans and surface to deep water, based on the sequences of 16S-23S rRNA internal transcribed spacer (ITS). A total of 1339 ITS sequences recovered from 20 samples unveiled diverse and several previously unknown clades of Prochlorococcus and Synechococcus. Six high-light (HL)-adapted Prochlorococcus clades were identified, among which clade HLVI had not been described previously. Prochlorococcus clades HLIII, HLIV and HLV, detected in the Equatorial Pacific samples, could be related to the HNLC clades recently found in the high-nutrient, low-chlorophyll (HNLC), iron-depleted tropical oceans. At least four novel Synechococcus clades (out of six clades in total) in subcluster 5.3 were found in subtropical open oceans and the South China Sea. A niche partitioning with depth was observed in the Synechococcus subcluster 5.3. Members of Synechococcus subcluster 5.2 were dominant in the high-latitude waters (northern Bering Sea and Chukchi Sea), suggesting a possible cold-adaptation of some marine Synechococcus in this subcluster. A distinct shift of the picocyanobacterial community was observed from the Bering Sea to the Chukchi Sea, which reflected the change of water temperature. Our study demonstrates that oceanic systems contain a large pool of diverse picocyanobacteria, and further suggest that new genotypes or ecotypes of picocyanobacteria will continue to emerge, as microbial consortia are explored with advanced sequencing technology.

Interannual and Decadal Changes in Salinity in the Oceanic Subtropical Gyres

NASA Astrophysics Data System (ADS)

Bulusu, Subrahmanyam

2017-04-01

There is evidence that the global water cycle has been undergoing an intensification over several decades as a response to increasing atmospheric temperatures, particularly in regions with skewed evaporation - precipitation (E-P) patterns such as the oceanic subtropical gyres. Moreover, observational data (rain gauges, etc.) are quite sparse over such areas due to the inaccessibility of open ocean regions. In this work, a comparison of observational and model simulations are conducted to highlight the potential applications of satellite derived salinity from NASA Aquarius Salinity mission, NASA Soil Moisture and Ocean Salinity (SMOS), and ESA's Soil Moisture Active Passive (SMAP). We explored spatial and temporal salinity changes (and trends) in surface and subsurface in the oceanic subtropical gyres using Argo floats salinity data, Simple Ocean Data Assimilation (SODA) reanalysis, Estimating the Circulations & Climate of the Ocean GECCO (German ECCO) model simulations, and Hybrid Coordinate Ocean Model (HYCOM). Our results based on SODA reanalysis reveals that a positive rising trend in sea surface salinity in the subtropical gyres emphasizing evidence for decadal intensification in the surface forcing in these regions. Zonal drift in the location of the salinity maximum of the south Pacific, north Atlantic, and south Indian regions implies a change in the mean near-surface currents responsible for advecting high salinity waters into the region. Also we found out that an overall salinity increase within the mixed layer, and a subsurface salinity decrease at depths greater than 200m in the global subtropical gyres over 61 years. We determine that freshwater fluxes at the air-sea interface are the primary drivers of the sea surface salinity (SSS) signature over these open ocean regions by quantifying the advective contribution within the surface layer. This was demonstrated through a mixed layer salinity budget in each subtropical gyre based on the vertically integrated advection and entrainment of salt. Our analysis of decadal variability of fluxes into and out of the gyres reveals little change in the strength of the mean currents through this region despite an increase in the annual export of salt in all subtropical gyres, with the meridional component dominating the zonal. This study reveals that the salt content of E-P maximum waters advected into the subtropical gyres is increasing over time. A combination of increasing direct evaporation over the regions with increasing remote evaporation over nearby E-P maxima is believed to be the main driver in increasing salinity of the subtropical oceans, suggesting an intensification of the global water cycle over decadal timescales.

Oceanic migration and spawning of anguillid eels.

PubMed

Tsukamoto, K

2009-06-01

Many aspects of the life histories of anguillid eels have been revealed in recent decades, but the spawning migrations of their silver eels in the open ocean still remains poorly understood. This paper overviews what is known about the migration and spawning of anguillid species in the ocean. The factors that determine exactly when anguillid eels will begin their migrations are not known, although environmental influences such as lunar cycle, rainfall and river discharge seem to affect their patterns of movement as they migrate towards the ocean. Once in the ocean on their way to the spawning area, silver eels probably migrate in the upper few hundred metres, while reproductive maturation continues. Although involvement of a magnetic sense or olfactory cues seems probable, how they navigate or what routes they take are still a matter of speculation. There are few landmarks in the open ocean to define their spawning areas, other than oceanographic or geological features such as oceanic fronts or seamounts in some cases. Spawning of silver eels in the ocean has never been observed, but artificially matured eels of several species have exhibited similar spawning behaviours in the laboratory. Recent collections of mature adults and newly spawned preleptocephali in the spawning area of the Japanese eel Anguilla japonica have shown that spawning occurs during new moon periods in the North Equatorial Current region near the West Mariana Ridge. These data, however, show that the latitude of the spawning events can change among months and years depending on oceanographic conditions. Changes in spawning location of this and other anguillid species may affect their larval transport and survival, and appear to have the potential to influence recruitment success. A greater understanding of the spawning migration and the choice of spawning locations by silver eels is needed to help conserve declining anguillid species.

"SPURS" in the North Atlantic Salinity Maximum

NASA Astrophysics Data System (ADS)

Schmitt, Raymond

2014-05-01

The North Atlantic Salinity Maximum is the world's saltiest open ocean salinity maximum and was the focus of the recent Salinity Processes Upper-ocean Regional Study (SPURS) program. SPURS was a joint venture between US, French, Irish, and Spanish investigators. Three US and two EU cruises were involved from August, 1012 - October, 2013 as well as surface moorings, glider, drifter and float deployments. Shipboard operations included underway meteorological and oceanic data, hydrographic surveys and turbulence profiling. The goal is to improve our understanding of how the salinity maximum is maintained and how it may be changing. It is formed by an excess of evaporation over precipitation and the wind-driven convergence of the subtropical gyre. Such salty areas are getting saltier with global warming (a record high SSS was observed in SPURS) and it is imperative to determine the relative roles of surface water fluxes and oceanic processes in such trends. The combination of accurate surface flux estimates with new assessments of vertical and horizontal mixing in the ocean will help elucidate the utility of ocean salinity in quantifying the changing global water cycle.

On the linkages between the global carbon-nitrogen-phosphorus cycles

NASA Astrophysics Data System (ADS)

Tanaka, Katsumasa; Mackenzie, Fred; Bouchez, Julien; Knutti, Reto

2013-04-01

State-of-the-art earth system models used for long-term climate projections are becoming ever more complex in terms of not only spatial resolution but also the number of processes. Biogeochemical processes are beginning to be incorporated into these models. The motivation of this study is to quantify how climate projections are influenced by biogeochemical feedbacks. In the climate modeling community, it is virtually accepted that climate-Carbon (C) cycle feedbacks accelerate the future warming (Cox et al. 2000; Friedlingstein et al. 2006). It has been demonstrated that the Nitrogen (N) cycle suppresses climate-C cycle feedbacks (Thornton et al. 2009). On the contrary, biogeochemical studies show that the coupled C-N-Phosphorus (P) cycles are intimately interlinked via biosphere and the N-P cycles amplify C cycle feedbacks (Ver et al. 1999). The question as to whether the N-P cycles enhance or attenuate C cycle feedbacks is debated and has a significant implication for projections of future climate. We delve into this problem by using the Terrestrial-Ocean-aTmosphere Ecosystem Model 3 (TOTEM3), a globally-aggregated C-N-P cycle box model. TOTEM3 is a process-based model that describes the biogeochemical reactions and physical transports involving these elements in the four domains of the Earth system: land, atmosphere, coastal ocean, and open ocean. TOTEM3 is a successor of earlier TOTEM models (Ver et al. 1999; Mackenzie et al. 2011). In our presentation, we provide an overview of fundamental features and behaviors of TOTEM3 such as the mass balance at the steady state and the relaxation time scales to various types of perturbation. We also show preliminary results to investigate how the N-P cycles influence the behavior of the C cycle. References Cox PM, Betts RA, Jones CD, Spall SA, Totterdell IJ (2000) Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature, 408, 184-187. Friedlingstein P, Cox P, Betts R, Bopp L, von Bloh W, Brovkin V, Cadule P, Doney S, Eby M, Fung I, Bala G, John J, Jones C, Joos F, Kato T, Kawamiya M, Knorr W, Lindsay K, Matthews HD, Raddatz T, Rayner P, Reick C, Roeckner E, Schnitzler KG, Schnur R, Strassmann K, Weaver AJ, Yoshikawa C, Zeng N (2006) Climate-Carbon Cycle Feedback Analysis: Results from the C4MIP Model Intercomparison. Journal of Climate, 19, 3337-3353. Mackenzie FT, De Carlo EH, Lerman A (2011) Coupled C, N, P, and O biogeochemical cycling at the land-ocean interface. In: Wolanski E, McLusky DS (eds) Treatise on Estuarine and Coastal Science, vol 5. Academic Press, Waltham, pp 317-342. Thornton PE, Doney SC, Lindsay K, Moore JK, Mahowald N, Randerson JT, Fung I, Lamarque JF, Feddema JJ, Lee YH (2009) Carbon-nitrogen interactions regulate climate-carbon cycle feedbacks: results from an atmosphere-ocean general circulation model. Biogeosciences, 6, 2099-2120. Ver LMB, Mackenzie FT, Lerman A (1999) Biogeochemical responses of the carbon cycle to natural and human perturbations: Past, present, and future. American Journal of Science, 299, 762-801.

Ocean Salinity Variance and the Global Water Cycle.

NASA Astrophysics Data System (ADS)

Schmitt, R. W.

2012-12-01

Ocean salinity variance is increasing and appears to be an indicator of rapid change in the global water cycle. While the small terrestrial water cycle does not reveal distinct trends, in part due to strong manipulation by civilization, the much larger oceanic water cycle seems to have an excellent proxy for its intensity in the contrasts in sea surface salinity (SSS). Change in the water cycle is arguably the most important challenge facing mankind. But how well do we understand the oceanic response? Does the ocean amplify SSS change to make it a hyper-sensitive indicator of change in the global water cycle? An overview of the research challenges to the oceanographic community for understanding the dominant component of the global water cycle is provided.

Organic nutrient chemistry and the marine microbiome

DOE Office of Scientific and Technical Information (OSTI.GOV)

Repeta, Daniel J.; Boiteau, Rene M.

Vast expanses of the ocean are characterized by extraordinarily low concentrations of nutrients but nevertheless support vibrant communities of marine microbes. In aggregate, these communities drive many of the important elemental cycles that sustain life on Earth. Microbial communities are organized to maximize nutrient and energy transfer between cells, and efficiently recycle organic carbon, nitrogen, phosphorus and trace metals. Energy and nutrient transfer occurs across a broad range of spatial scales. Large-sized marine algae and bacteria support epibiont communities that are physically in contact, exchanging nutrients and energy across cell membranes, while other communities that are physically far apart, relymore » on the horizontal mixing of ocean currents or the vertical pull of gravity to transfer nutrient and energy containing organic matter. Marine organic geochemists are making rapid progress in understanding the chemistry of the marine microbiome. These advances have benefited from parallel developments in analytical chemistry, microbial isolation and culture techniques, and advances in microbial genomics, transcriptomics, and proteomics. The combination of all three approaches has proven to be quite powerful. Here we highlight two aspects of the chemistry of organic phosphorus and trace metal cycling and the marine microbiome. In each study, advances in chemical analyses, microbial culture, and microbial genomics played key roles in understanding how microbial communities interact to facilitate nutrient cycling in the open ocean.« less

Declining oxygen in the global ocean and coastal waters.

PubMed

Breitburg, Denise; Levin, Lisa A; Oschlies, Andreas; Grégoire, Marilaure; Chavez, Francisco P; Conley, Daniel J; Garçon, Véronique; Gilbert, Denis; Gutiérrez, Dimitri; Isensee, Kirsten; Jacinto, Gil S; Limburg, Karin E; Montes, Ivonne; Naqvi, S W A; Pitcher, Grant C; Rabalais, Nancy N; Roman, Michael R; Rose, Kenneth A; Seibel, Brad A; Telszewski, Maciej; Yasuhara, Moriaki; Zhang, Jing

2018-01-05

Oxygen is fundamental to life. Not only is it essential for the survival of individual animals, but it regulates global cycles of major nutrients and carbon. The oxygen content of the open ocean and coastal waters has been declining for at least the past half-century, largely because of human activities that have increased global temperatures and nutrients discharged to coastal waters. These changes have accelerated consumption of oxygen by microbial respiration, reduced solubility of oxygen in water, and reduced the rate of oxygen resupply from the atmosphere to the ocean interior, with a wide range of biological and ecological consequences. Further research is needed to understand and predict long-term, global- and regional-scale oxygen changes and their effects on marine and estuarine fisheries and ecosystems. Copyright © 2018, American Association for the Advancement of Science.

Making sense of ocean biota: how evolution and biodiversity of land organisms differ from that of the plankton.

PubMed

Smetacek, Victor

2012-09-01

The oceans cover 70% of the planet's surface, and their planktonic inhabitants generate about half the global primary production, thereby playing a key role in modulating planetary climate via the carbon cycle. The ocean biota have been under scientific scrutiny for well over a century, and yet our understanding of the processes driving natural selection in the pelagic environment - the open water inhabited by drifting plankton and free-swimming nekton - is still quite vague. Because of the fundamental differences in the physical environment, pelagic ecosystems function differently from the familiar terrestrial ecosystems of which we are a part. Natural selection creates biodiversity but understanding how this quality control of random mutations operates in the oceans - which traits are selected for under what circumstances and by which environmental factors, whether bottom-up or top-down - is currently a major challenge. Rapid advances in genomics are providing information, particularly in the prokaryotic realm, pertaining not only to the biodiversity inventory but also functional groups. This essay is dedicated to the poorly understood tribes of planktonic protists (unicellular eukaryotes) that feed the ocean's animals and continue to run the elemental cycles of our planet. It is an attempt at developing a conceptually coherent framework to understand the course of evolution by natural selection in the plankton and contrast it with the better-known terrestrial realm. I argue that organism interactions, in particular co-evolution between predators and prey (the arms race), play a central role in driving evolution in the pelagic realm. Understanding the evolutionary forces shaping ocean biota is a prerequisite for harnessing plankton for human purposes and also for protecting the oceanic ecosystems currently under severe stress from anthropogenic pressures.

On the initiation of subduction zones

NASA Astrophysics Data System (ADS)

Cloetingh, Sierd; Wortel, Rinus; Vlaar, N. J.

1989-03-01

Analysis of the relation between intraplate stress fields and lithospheric rheology leads to greater insight into the role that initiation of subduction plays in the tectonic evolution of the lithosphere. Numerical model studies show that if after a short evolution of a passive margin (time span a few tens of million years) subduction has not yet started, continued aging of the passive margin alone does not result in conditions more favorable for transformation into an active margin. Although much geological evidence is available in supporting the key role small ocean basins play in orogeny and ophiolite emplacement, evolutionary frameworks of the Wilson cycle usually are cast in terms of opening and closing of wide ocean basins. We propose a more limited role for large oceans in the Wilson cycle concept. In general, initiation of subduction at passive margins requires the action of external plate-tectonic forces, which will be most effective for young passive margins prestressed by thick sedimentary loads. It is not clear how major subduction zones (such as those presently ringing the Pacific Basin) form but it is unlikely they form merely by aging of oceanic lithosphere. Conditions likely to exist in very young oceanic regions are quite favorable for the development of subduction zones, which might explain the lack of preservation of back-arc basins and marginal seas. Plate reorganizations probably occur predominantly by the formation of new spreading ridges, because stress relaxation in the lithosphere takes place much more efficiently through this process than through the formation of new subduction zones.

Iron, phytoplankton growth, and the carbon cycle.

PubMed

Street, Joseph H; Paytan, Adina

2005-01-01

Iron is an essential nutrient for all living organisms. Iron is required for the synthesis of chlorophyll and of several photosynthetic electron transport proteins and for the reduction of CO2, SO4(2-), and NO3(-) during the photosynthetic production of organic compounds. Iron concentrations in vast areas of the ocean are very low (<1 nM) due to the low solubility of iron in oxic seawater. Low iron concentrations have been shown to limit primary production rates, biomass accumulation, and ecosystem structure in a variety of open-ocean environments, including the equatorial Pacific, the subarctic Pacific and the Southern Ocean and even in some coastal areas. Oceanic primary production, the transfer of carbon dioxide into organic carbon by photosynthetic plankton (phytoplankton), is one process by which atmospheric CO2 can be transferred to the deep ocean and sequestered for long periods of time. Accordingly, iron limitation of primary producers likely plays a major role in the global carbon cycle. It has been suggested that variations in oceanic primary productivity, spurred by changes in the deposition of iron in atmospheric dust, control atmospheric CO2 concentrations, and hence global climate, over glacial-interglacial timescales. A contemporary application of this "iron hypothesis" promotes the large-scale iron fertilization of ocean regions as a means of enhancing the ability of the ocean to store anthropogenic CO2 and mitigate 21st century climate change. Recent in situ iron enrichment experiments in the HNLC regions, however, cast doubt on the efficacy and advisability of iron fertilization schemes. The experiments have confirmed the role of iron in regulating primary productivity, but resulted in only small carbon export fluxes to the depths necessary for long-term sequestration. Above all, these experiments and other studies of iron biogeochemistry over the last two decades have begun to illustrate the great complexity of the ocean system. Attempts to engineer this system are likely to provoke a similarly complex, unpredictable response.

Carbon Processing in Aquatic Critical Zones: A Source-to-Sink Perspective

NASA Astrophysics Data System (ADS)

Bianchi, T. S.

2017-12-01

The majority of organic carbon (OC) in the global ocean is buried in the coastal margin. In particular, river delta and non-deltaic shelf regions bury an estimated 114 Tg C year-1 and 70 Tg C year-1, respectively, with only ca. 6 Tg C year-1 buried in the open ocean. While there has long standing general agreement that continental selves represent the largest sink of both terrestrial (OCterr) and marine (OCmari) OC in the global ocean, our understanding of the spatial and temporal complexity of this region continues to evolve. For example, fjords are now more recognized as "hotspots"of carbon burial with recent estimates suggesting fjord surface area-normalized OC burial rates are at least five times greater than other marine systems and one hundred times greater than the entire ocean average. Here, I will compare and contrast some of the key molecular biomarkers that have been used to date to track OC across different depositional environments (e.g., large river deltas and fjords) and explore how margin-type, residence time of transport, reservoir dams, redox, priming effects, and molecular stability, impact the utility of using different biomarkers in coastal OC cycling. Finally, I will focus on important critical zones within the aquatic continuum from land-to-sea and examine how more attention is needed better understand OC cycling in these new dynamic interfaces in the Anthropocene.

Atmospheric Concentrations of Persistent Organic Pollutants in the Southern Ocean

NASA Astrophysics Data System (ADS)

Vlahos, P.; Edson, J.; Cifuentes, A.; McGillis, W. R.; Zappa, C.

2008-12-01

Long-range transport of persistent organic pollutant (POPs) is a global concern. Remote regions such as the Southern Ocean are greatly under-sampled though critical components in understanding POPs cycling. Over 20 high-volume air samples were collected in the Southern Ocean aboard the RV Brown during the GASEX III experiment between Mar 05 to April 9 2008. The relatively stationary platform (51S,38W) enabled the collection of a unique atmospheric time series at this open ocean station. Air sampling was also conducted across transects from Punto Arenas, Chile and to Montevideo, Uruguay. Samples were collected using glass sleeves packed with poly-urethane foam plugs and C-18 resin in order to collect target organic pollutants (per-fluorinated compounds, currently and historically used pesticides) in this under-sampled region. Here we present POPs concentrations and trends over the sampled period and compare variations with air parcel back trajectories to establish potential origins of their long-range transport.

Evolution of the Arctic-North Atlantic and the Western Tethys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ziegler, P.A.

1988-01-01

This volume provides an overview of the late Paleozoic to recent geological evolution of the continents and shelves bordering the North Atlantic Ocean, the Norwegian-Greenland Sea, the Arctic Ocean, and the Mediterranean Sea. The evolution of these seas has been the subject of many studies and compilations, which discuss the evolution of oceanic basins on the basis of their magnetic sea-floor anomalies. The volume presented combines this information with geological data from the adjacent shelf and onshore areas. It retraces the evolution of sedimentary basins developed during the rifting phases that preceded the opening of these oceans and highlights themore » scope of the associated intra-plate phenomena. The author presents a reconstruction of the late Paleozoic and early Mesozoic development of Europe, northernmost Africa and northeastern North America-Greenland and discusses the different orogenic cycles that accompanied the stepwise assembly of Pangea and the early rifting phases heralding its break-up.« less

Autonomous Observational Platforms for Ocean Studies: Operation, Advantages of Sensor Technology and Data Management

NASA Astrophysics Data System (ADS)

Atamanchuk, D.; Lai, J.; Vining, M.; Kehoe, D.; Siddall, G.; Send, U.; Wallace, D.

2016-02-01

Ocean Science and Technology research group (CERC.OCEAN) at Dalhousie University focuses on new approaches in design and development of autonomous platforms to study biogeochemical and ecological changes in the world's oceans. The principal research regions included the Labrador Sea, the Northwest Atlantic between Halifax and Bermuda, and the coastal areas of Atlantic Canada. The need for improved constraints on the ocean's present and future carbon cycle is of high relevance for the Northwest Atlantic, which is recognized as a largest sink of carbon dioxide(CO2) through air-sea exchange and subsequent transport to deeper layers of the global ocean. With the use of novel sensor technology integrated into the designed platforms we are achieving a superior spatial and temporal resolution of observations. SeaCycler - a surface piercing mooring - was designed to endure year-long measurements in harsh conditions of the open ocean, like Labrador Sea, while making daily profiles of the upper 150m of the water column. Significant research efforts within CERC.OCEAN are dedicated for improving sensors' data outcome. This includes testing, calibration of the sensors, QC and postprocessing to assure reliable and trustworthy measurements. Examples and implication of the data from SeaCycler, and other platforms including buoys, and automonous Volunteer Observing Ship (VOS) flow-through system will be presented.

500 kyr of Indian Ocean Walker Circulation Variability Using Foraminiferal Mg/Ca and Stable Isotopes

NASA Astrophysics Data System (ADS)

Groeneveld, J.; Mohtadi, M.; Lückge, A.; Pätzold, J.

2017-12-01

The tropical Indian Ocean is a key location for paleoclimate research affected by different oceanographic and atmospheric processes. Annual climate variations are strongly controlled by the Indian and Asian Monsoon characterized by bi-annually reversing trade winds. Inter-annual climate variations in the Walker circulation are caused by the Indian Ocean Dipole and El Niño-Southern Oscillation resulting in either heavy flooding or severe droughts like for example the famine of 2011 in eastern Africa. Oceanographically the tropical western Indian Ocean receives water masses from the Indonesian Gateway area, sub-Antarctic waters that upwell south of the equator, and the outflow waters from the highly saline Red Sea. On the other hand, the tropical western Indian Ocean is a major source for providing water masses to the Agulhas Current system. Although the eastern Indian Ocean has been studied extensively, the tropical western Indian Ocean is still lacking in high quality climate-archives that have the potential to provide important information to understand how the ocean and atmospheric zonal circulation have changed in the past, and possibly will change in the future. Until now there were no long sediment cores available covering several glacial-interglacial cycles in the tropical western Indian Ocean. Core GeoB 12613-1, recovered during RV Meteor Cruise M75/2 east of the island of Pemba off Tanzania, provides an open-ocean core with well-preserved sediments covering the last five glacial-interglacial cycles ( 500 kyr). Mg/Ca and stable isotopes on both surface- and thermocline dwelling foraminifera have been performed to test how changes in sea water temperatures and relative sea water salinity were coupled on orbital time scales. The results are compared with similar records generated for the tropical eastern Indian Ocean in core SO139-74KL off Sumatra. Water column stratification on both sides of the Indian Ocean and the cross-basin gradients in sea water temperature and relative salinity varied both on millennial and orbital time scales implying changes in the Walker circulation.

Global Patterns of Bacterial Beta-Diversity in Seafloor and Seawater Ecosystems

PubMed Central

Zinger, Lucie; Amaral-Zettler, Linda A.; Fuhrman, Jed A.; Horner-Devine, M. Claire; Huse, Susan M.; Welch, David B. Mark; Martiny, Jennifer B. H.; Sogin, Mitchell; Boetius, Antje; Ramette, Alban

2011-01-01

Background Marine microbial communities have been essential contributors to global biomass, nutrient cycling, and biodiversity since the early history of Earth, but so far their community distribution patterns remain unknown in most marine ecosystems. Methodology/Principal Findings The synthesis of 9.6 million bacterial V6-rRNA amplicons for 509 samples that span the global ocean's surface to the deep-sea floor shows that pelagic and benthic communities greatly differ, at all taxonomic levels, and share <10% bacterial types defined at 3% sequence similarity level. Surface and deep water, coastal and open ocean, and anoxic and oxic ecosystems host distinct communities that reflect productivity, land influences and other environmental constraints such as oxygen availability. The high variability of bacterial community composition specific to vent and coastal ecosystems reflects the heterogeneity and dynamic nature of these habitats. Both pelagic and benthic bacterial community distributions correlate with surface water productivity, reflecting the coupling between both realms by particle export. Also, differences in physical mixing may play a fundamental role in the distribution patterns of marine bacteria, as benthic communities showed a higher dissimilarity with increasing distance than pelagic communities. Conclusions/Significance This first synthesis of global bacterial distribution across different ecosystems of the World's oceans shows remarkable horizontal and vertical large-scale patterns in bacterial communities. This opens interesting perspectives for the definition of biogeographical biomes for bacteria of ocean waters and the seabed. PMID:21931760

Radon and radium in the ice-covered Arctic Ocean, and what they reveal about gas exchange in the sea ice zone.

NASA Astrophysics Data System (ADS)

Loose, B.; Kelly, R. P.; Bigdeli, A.; Moran, S. B.

2014-12-01

The polar sea ice zones are regions of high primary productivity and interior water mass formation. Consequently, the seasonal sea ice cycle appears important to both the solubility and biological carbon pumps. To estimate net CO2 transfer in the sea ice zone, we require accurate estimates of the air-sea gas transfer velocity. In the open ocean, the gas transfer velocity is driven by wind, waves and bubbles - all of which are strongly altered by the presence of sea ice, making it difficult to translate open ocean estimates of gas transfer to the ice zone. In this study, we present profiles of 222Rn and 226Ra throughout the mixed-layer and euphotic zone. Profiles were collected spanning a range of sea ice cover conditions from 40 to 100%. The profiles of Rn/Ra can be used to estimate the gas transfer velocity, but the 3.8 day half-life of 222Rn implies that mixed layer radon will have a memory of the past ~20 days of gas exchange forcing, which may include a range of sea ice cover conditions. Here, we compare individual estimates of the gas transfer velocity to the turbulent forcing conditions constrained from shipboard and regional reanalysis data to more appropriately capture the time history upper ocean Rn/Ra.

Propagation of Intra-Seasonal Tropical Oscillations (PISTON)

NASA Astrophysics Data System (ADS)

Moum, J. N.

2017-12-01

During monsoon season over the South China Sea and Philippines, weather varies on the subseasonal time scale. Disturbances of the "boreal summer intraseasonal oscillation" (BSISO) move north and east across the region over periods of weeks. These disturbances are strongly conditioned by the complex geography of the region. The diurnal cycle in convection over islands and adjacent coastal seas is strong. Air-sea interaction is modulated by ocean stratification and local circulation patterns that are themselves complex and diurnally varying. The multiple pathways and space-time scales in the regional ocean-atmosphere-land system make prediction on subseasonal to seasonal time scales challenging. The PISTON field campaign targets the west coast of Luzon in August/September 2018. It includes ship-based, moored and land-based measurements, a significant modeling effort and coordinates with the Philippine SALICA program (Sea Air Land Interactions in the Context of Archipelagos) and the aircraft-based, NASA-funded CAMP2EX campaign (Cloud and Aerosol Monsoonal Processes-Philippines Experiment). The diurnal cycle and its interaction with the BSISO are primary targets for PISTON. Key questions are: how heat is stored and released in the upper ocean on intraseasonal time scales; how that heat storage interacts with atmospheric convection; and what role it plays in BSISO maintenance and propagation. Key processes include land-sea breezes, orographic influence on convection, river discharge to coastal oceans, gravity waves, diurnal warm layers, internal tides, and a buoyancy-driven northward coastal current. As intraseasonal disturbances approach the region, the presence of islands, with their low surface heat capacity, mountains, inhomogeneous distribution of urban/vegetation/soil, and strong diurnal cycle disrupts the air-sea heat exchange that sustains the BSISO over the ocean, confounding prediction models in which these processes are inadequately represented. Along with upscale influences, PISTON seeks to advance our understanding of how large scale atmospheric circulation variability over the South China Sea, related to the monsoon, BSISO, and convectively coupled waves, modifies the local diurnal cycle, synoptic systems, and air sea interaction in coastal regions and nearby open seas.

Distributions and Changes of Carbonate Parameters Along the U.S. East Coast

NASA Astrophysics Data System (ADS)

Xu, Y. Y.; Cai, W. J.; Wanninkhof, R. H.; Salisbury, J., II

2017-12-01

On top of anthropogenic climate change, upwelling, eutrophication, river discharge, and interactions with the open ocean have affected carbonate chemistry in coastal waters. In this study, we present the large-scale variations of carbonate parameters along the U.S. east coast using in situ observations obtained during an East Coast Ocean Acidification (ECOA) cruise in summer 2015. Compare with previous large-scale cruises along the east coast, the ECOA cruise increases spatial coverage in the Gulf of Marine region and has more offshore stations for a better understanding of carbon dynamics in coastal waters and their interactions with open ocean waters. Our results show that the spatial distribution of water mass properties set up the large-scale advection of salt and heat and the distribution of total alkalinity (TA). However, dissolved inorganic carbon (DIC) shows a distinct pattern. Coastal water pH displays high variability in the Gulf of Maine and the Mid-Atlantic Bight (MAB). But it is relatively homogeneous in the South Atlantic Bight (SAB). In contrast, the distribution of aragonite saturation state (Ω) has an increase pattern from north to south similar to those of TA, SST, and SSS. A mechanistic discussion will be presented to understand the controls on Ω in eastern coastal waters. A comparison with previous cruises also suggests very different changes of pH and Ω in the MAB and SAB. Preliminary analysis suggests an overall increase in surface pH and Ω in the MAB. In contrast, pH and Ω in the SAB surface waters decrease over the past two decades. This work serves as a platform for the monitoring of large-scale carbon cycling in the U.S. east coast. It is also important to identify the physical and biogeochemical processes that affect these distributions and changes over time for a better understanding of carbon cycling and ocean acidification in coastal waters.

Coastal Carbon Dynamics as a New Chapter in SOCCR2: Tidal Wetlands and Estuaries

NASA Astrophysics Data System (ADS)

Windham-Myers, L.; Megonigal, P.; Cai, W. J.; Hopkinson, C.; Wang, A. Z.; Andersson, A. J.; Hinson, A.; Lagomasino, D.; Peteet, D. M.; Giri, C. P.; Howard, J.; Tang, J.; Crosswell, J.; Martin Hernandez-Ayon, J. M.; Dunton, K. H.; Kroeger, K. D.; Paulsen, M. L.; Allison, M. A.; Siedlecki, S. A.; Alin, S. R.; Hu, X.; Tzortziou, M.; Najjar, R.; Schafer, K. V.; Watson, E.; Pidgeon, E.

2016-12-01

Estuaries and tidal wetlands have been identified as distinct landscape elements for carbon cycling, worthy of a chapter in the pending State of the Carbon Cycle Report - version 2. Despite relatively small aerial coverage compared to other subsystems, tidal wetlands and estuaries have the greatest influence on carbon dynamics of any coastal ocean subsystem. As conduits that filter all material passing between land and the sea, they also exhibit the highest transfer rates of CO2 with the atmosphere of any of the coastal ocean subsystems. Carbon dynamics in estuaries and wetlands are constantly changing, reflecting geomorphic and ecological responses to long and short-term perturbations in external drivers such as sea-level rise, climate change, nutrient loading and land-use change. The influence of these drivers are profound in coastal systems, often more so than in inland wetlands or open ocean environments, and thus require distinct attention to patterns and processes associated with coastal ecosystem functioning, including carbon sequestration services in tidal wetland soils. This new chapter focusses on data sources available in North America to: (1) assess the current state of carbon stocks and fluxes in coastal settings, (2) document understanding of drivers associated with significant fluxes and stocks, and (3) synthesize carbon dynamics from a global context to regional perspectives (East, West, Gulf and high-latitude coastlines). Insights from remote sensing, in situ field data, and numerical models have advanced our ability to monitor and project carbon cycling in this dynamic and narrow fringe at the land-ocean interface. This synthetic chapter will address how these advances can help in decision making, as well as address remaining gaps in our knowledge and monitoring capabilities for these diverse and productive habitats.

A 600-ka Arctic sea-ice record from Mendeleev Ridge based on ostracodes

USGS Publications Warehouse

Cronin, Thomas M.; Polyak, L.V.; Reed, D.; Kandiano, E. S.; Marzen, R. E.; Council, E. A.

2013-01-01

Arctic paleoceanography and sea-ice history were reconstructed from epipelagic and benthic ostracodes from a sediment core (HLY0503-06JPC, 800 m water depth) located on the Mendeleev Ridge, Western Arctic Ocean. The calcareous microfaunal record (ostracodes and foraminifers) covers several glacial/interglacial cycles back to estimated Marine Isotope Stage 13 (MIS 13, ∼500 ka) with an average sedimentation rate of ∼0.5 cm/ka for most of the stratigraphy (MIS 5–13). Results based on ostracode assemblages and an unusual planktic foraminiferal assemblage in MIS 11 dominated by a temperate-water species Turborotalita egelida show that extreme interglacial warmth, high surface ocean productivity, and possibly open ocean convection characterized MIS 11 and MIS 13 (∼400 and 500 ka, respectively). A major shift in western Arctic Ocean environments toward perennial sea ice occurred after MIS 11 based on the distribution of an ice-dwelling ostracode Acetabulastoma arcticum. Spectral analyses of the ostracode assemblages indicate sea ice and mid-depth ocean circulation in western Arctic Ocean varied primarily at precessional (∼22 ka) and obliquity (∼40 ka) frequencies.

NASA/GSFC Research Activities for the Global Ocean Carbon Cycle: A Prospectus for the 21st Century

NASA Technical Reports Server (NTRS)

Gregg, W. W.; Behrenfield, M. J.; Hoge, F. E.; Esaias, W. E.; Huang, N. E.; Long, S. R.; McClain, C. R.

2000-01-01

There are increasing concerns that anthropogenic inputs of carbon dioxide into the Earth system have the potential for climate change. In response to these concerns, the GSFC Laboratory for Hydrospheric Processes has formed the Ocean Carbon Science Team (OCST) to contribute to greater understanding of the global ocean carbon cycle. The overall goals of the OCST are to: 1) detect changes in biological components of the ocean carbon cycle through remote sensing of biooptical properties, 2) refine understanding of ocean carbon uptake and sequestration through application of basic research results, new satellite algorithms, and improved model parameterizations, 3) develop and implement new sensors providing critical missing environmental information related to the oceanic carbon cycle and the flux of CO2 across the air-sea interface. The specific objectives of the OCST are to: 1) establish a 20-year time series of ocean color, 2) develop new remote sensing technologies, 3) validate ocean remote sensing observations, 4) conduct ocean carbon cycle scientific investigations directly related to remote sensing data, emphasizing physiological, empirical and coupled physical/biological models, satellite algorithm development and improvement, and analysis of satellite data sets. These research and mission objectives are intended to improve our understanding of global ocean carbon cycling and contribute to national goals by maximizing the use of remote sensing data.

Aquatic sources and sinks for nitrous oxide

NASA Technical Reports Server (NTRS)

Elkins, J. W.; Wofsy, S. C.; Mcelroy, M. B.; Kaplan, W. A.; Kolb, C. E.

1978-01-01

Data are presented which suggest the complexity of the aquatic nitrogen cycle as it affects N2O. The data are from studies made in the central and south-east tropical regions of the Pacific Ocean and in Chesapeake Bay. The data indicate that oxidation of ammonium and amino nitrogen and nitrification form the principle source for marine N2O. It is estimated that the yearly global yield for oceanic N2O is less than about 10 to the 7th power tons. The consumption of atmospheric N2O by the open ocean has not been evidenced, although data from the south-east tropical Pacific and Chesapeake Bay show the consumption of dissolved N2O in low-oxygen conditions. Preliminary observations have also indicated the consumption of atmospheric N2O by aquatic systems such as freshwater pond and a tidal saltmarsh.

Barium bioaccumulation by bacterial biofilms and implications for Ba cycling and use of Ba proxies.

PubMed

Martinez-Ruiz, Francisca; Jroundi, Fadwa; Paytan, Adina; Guerra-Tschuschke, Isabel; Abad, María Del Mar; González-Muñoz, María Teresa

2018-04-24

Ba proxies have been broadly used to reconstruct past oceanic export production. However, the precise mechanisms underlying barite precipitation in undersaturated seawater are not known. The link between bacterial production and particulate Ba in the ocean suggests that bacteria may play a role. Here we show that under experimental conditions marine bacterial biofilms, particularly extracellular polymeric substances (EPS), are capable of bioaccumulating Ba, providing adequate conditions for barite precipitation. An amorphous P-rich phase is formed at the initial stages of Ba bioaccumulation, which evolves into barite crystals. This supports that in high productivity regions where large amounts of organic matter are subjected to bacterial degradation, the abundant EPS would serve to bind the necessary Ba and form nucleation sites leading to barite precipitation. This also provides new insights into barite precipitation and opens an exciting field to explore the role of EPS in mineral precipitation in the ocean.

Anticipated Improvements to Net Surface Freshwater Fluxes from GPM

NASA Technical Reports Server (NTRS)

Smith, Eric A.

2005-01-01

Evaporation and precipitation over the oceans play very important roles in the global water cycle, upper-ocean heat budget, ocean dynamics, and coupled ocean-atmosphere dynamics. In the conventional representation of the terrestrial water cycle, the assumed role of the oceans is to act as near-infinite reservoirs of water with the main drivers of the water cycle being land- atmosphere interactions in which excess precipitation (P) over evaporation (E) is returned to the oceans as surface runoff and baseflow. Whereas this perspective is valid for short space and time scales -- fundamental principles, available observed estimates, and results from models indicate that the oceans play a far more important role in the large-scale water cycle at seasonal and longer timescales. Approximately 70-80% of the total global evaporation and precipitation occurs over oceans. Moreover, latent heat release into the atmosphere over the oceans is the major heat source driving global atmospheric circulations, with the moisture transported by circulations from oceans to continents being the major source of water precipitating over land. Notably, the major impediment in understanding and modeling the oceans role in the global water cycle is the lack of reliable net surface freshwater flux estimates (E - P fluxes) at the salient spatial and temporal resolutions, i.e., consistent coupled weekly to monthly E - P gridded datasets.

Temperature, productivity and sediment characteristics as drivers of seasonal and spatial variations of dissolved methane in the near-shore coastal areas (Belgian coastal zone, North Sea)

NASA Astrophysics Data System (ADS)

Borges, Alberto V.; Speeckaert, Gaëlle; Champenois, Willy; Scranton, Mary I.; Gypens, Nathalie

2017-04-01

The open ocean is a modest source of CH4 to the atmosphere compared to other natural and anthropogenic CH4 emissions. Coastal regions are more intense sources of CH4 to the atmosphere than open oceanic waters, in particular estuarine zones. The CH4 emission to the atmosphere from coastal areas is sustained by riverine inputs and methanogenesis in the sediments due to high organic matter (OM) deposition. Additionally, natural gas seeps are sources of CH4 to bottom waters leading to high dissolved CH4 concentrations in bottom waters (from tenths of nmol L-1 up to several µmol L-1). We report a data set of dissolved CH4 concentrations obtained at nine fixed stations in the Belgian coastal zone (Southern North Sea), during one yearly cycle, with a bi-monthly frequency in spring, and a monthly frequency during the rest of the year. This is a coastal area with multiple possible sources of CH4 such as from rivers and gassy sediments, and where intense phytoplankton blooms are dominated by the high dimethylsulfoniopropionate (DMSP) producing micro-algae Phaeocystis globosa, leading to DMSP and dimethylsulfide (DMS) concentrations. Furthermore, the BCZ is a site of important OM sedimentation and accumulation unlike the rest of the North Sea. Spatial variations of dissolved CH4 concentrations were very marked with a minimum yearly average of 9 nmol L-1 in one of the most off-shore stations and maximum yearly average of 139 nmol L-1 at one of the most near-shore stations. The spatial variations of dissolved CH4 concentrations were related to the organic matter (OM) content of sediments, although the highest concentrations seemed to also be related to inputs of CH4 from gassy sediments associated to submerged peat. In the near-shore stations with fine sand or muddy sediments with a high OM content, the seasonal cycle of dissolved CH4 concentration closely followed the seasonal cycle of water temperature, suggesting the control of methanogenesis by temperature in these OM replete sediments. In the off-shore stations with permeable sediments with a low OM content, the seasonal cycle of dissolved CH4 concentration showed a yearly peak following the chlorophyll-a spring peak. This suggests that in these OM poor sediments, methanogenesis depended on the delivery to the sediments of freshly produced OM. In both types of sediments, the seasonal cycle of dissolved CH4 concentrations was unrelated the seasonal cycles of DMS, and DMSP, despite the fact that these quantities were very high during the spring Phaeocystis globosa bloom. This suggests that in this shallow coastal environment CH4 production is overwhelmingly related to benthic processes and unrelated to DMS(P) transformations in the water column as recently suggested in several open ocean regions. The annual average CH4 emission was 41 mmol m-2 yr-1 in the most near-shore stations ( 4 km from the coast) and 10 mmol m-2 yr-1 in the most off-shore stations ( 23 km from the coast), 410-100 times higher than the average value in the open ocean (0.1 mmol m-2 yr-1). The strong control of CH4 concentrations by sediment OM content and by temperature suggests that marine coastal CH4 emissions, in particular shallow coastal areas, should respond in future to eutrophication and warming of climate. This is confirmed by the comparison of CH4 concentrations at five stations obtained in March in years 1990 and 2016, showing a decreasing trend consistent with alleviation of eutrophication in the area.

Seasonal and Interannual Fast-Ice Variability from MODIS Surface-Temperature Anomalies, and its Link to External Forcings in Atka Bay, Antarctica

NASA Astrophysics Data System (ADS)

Paul, S.; Hoppmann, M.; Willmes, S.; Heinemann, G.

2016-12-01

Around Antarctica, sea ice is regularly attached to coastal features. These regions of mostly seasonal fast ice interact with the atmosphere, ocean and coastal ecosystem in a variety of ways. The growth and breakup cycles may depend on different factors, such as water- and air temperatures, wind conditions, tides, ocean swell, the passage of icebergs and the presence of nearby polynyas. However, a detailed understanding about the interaction between these factors and the fast-ice cycle is missing. In order to better understand the linkages between general fast-ice evolution and external forcing factors, we present results from an observational case study performed on the seasonal fast-ice cover of Atka Bay, eastern Weddell Sea. The ice conditions in this region are critical for the supply of the German wintering station Neumayer III. Moreover, the fast ice at Atka Bay hosts a unique ecosystem based on the presence of a sub-ice platelet layer and a large emperor penguin colony. While some qualitative characterizations on the seasonal fast-ice cycle in this region exist, no proper quantification was carried out to date. The backbone of this work is a new algorithm, which yields the first continuous time series of open-water fractions from Moderate-Resolution Imaging Spectroradiometer (MODIS) surface temperatures. The open-water fractions are derived from a range of running multi-day median temperature composites, utilizing the thermal footprint of warm open water and thin ice in contrast to cold pack-ice/ice-shelf areas. This unique, and manually validated dataset allows us to monitor changes in fast-ice extent on a near daily basis, for a period of 14 years (2002-2015). In a second step, we combine these results with iceberg observations, data from the meteorological observatory, and auxiliary satellite data in order to identify the main factors governing fast-ice formation and break-up.

Implications of sea-ice biogeochemistry for oceanic production and emissions of dimethyl sulfide in the Arctic

NASA Astrophysics Data System (ADS)

Hayashida, Hakase; Steiner, Nadja; Monahan, Adam; Galindo, Virginie; Lizotte, Martine; Levasseur, Maurice

2017-06-01

Sea ice represents an additional oceanic source of the climatically active gas dimethyl sulfide (DMS) for the Arctic atmosphere. To what extent this source contributes to the dynamics of summertime Arctic clouds is, however, not known due to scarcity of field measurements. In this study, we developed a coupled sea ice-ocean ecosystem-sulfur cycle model to investigate the potential impact of bottom-ice DMS and its precursor dimethylsulfoniopropionate (DMSP) on the oceanic production and emissions of DMS in the Arctic. The results of the 1-D model simulation were compared with field data collected during May and June of 2010 in Resolute Passage. Our results reproduced the accumulation of DMS and DMSP in the bottom ice during the development of an ice algal bloom. The release of these sulfur species took place predominantly during the earlier phase of the melt period, resulting in an increase of DMS and DMSP in the underlying water column prior to the onset of an under-ice phytoplankton bloom. Production and removal rates of processes considered in the model are analyzed to identify the processes dominating the budgets of DMS and DMSP both in the bottom ice and the underlying water column. When openings in the ice were taken into account, the simulated sea-air DMS flux during the melt period was dominated by episodic spikes of up to 8.1 µmol m-2 d-1. Further model simulations were conducted to assess the effects of the incorporation of sea-ice biogeochemistry on DMS production and emissions, as well as the sensitivity of our results to changes of uncertain model parameters of the sea-ice sulfur cycle. The results highlight the importance of taking into account both the sea-ice sulfur cycle and ecosystem in the flux estimates of oceanic DMS near the ice margins and identify key uncertainties in processes and rates that should be better constrained by new observations.

Open oceanic productivity changes at mid-latitudes during interglacials and its relation to the Atlantic Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

Nave, Silvia; Lebreiro, S.; Kissel, C.; Guihou, A.; Figueiredo, M. O.; Silva, T. P.; Michel, E.; Cortijo, E.; Labeyrie, L.; Voelker, A.

2010-05-01

Variations in the interactions between marine ecosystems, thermohaline circulation, external forcing and atmospheric greenhouse gases concentrations are not yet fully represented in detailed models of the glacial-interglacial transitions. Most of the research on past productivity changes has been focused so far on high-productivity areas such as upwelling areas (i.e. equatorial or coastal upwelling areas) even though those regions appraise only a little part of the ocean. Accordingly, the importance of oceanic productivity changes over glacial/interglacial cycles should be better known, as it may also play an important role on the loss of photosynthetically generated carbon as a central mechanism in the global carbon cycle. Its understanding will help quantifying the parameters needed to run comprehensive climate models, and subsequently help to better predict climate change for the near future. A high-resolution study of oceanic productivity, bottom water flow speed, surface and deep-water mass, bottom water ventilation, and terrestrial input changes during two interglacials (Holocene and Marine Isotope Stage [MIS] 5), at an open ocean site approximately 300 km west off Portugal [IMAGES core MD01-2446: 39°03'N, 12°37'W, 3547 m water depth] was conducted within the AMOCINT project (ESF-EUROCORES programme, 06-EuroMARC-FP-008). Even though siliceous productivity is expectedly low for oceanic regions, it shows a robust and consistent pattern with increased values during cold phases of MIS 5, and during the glacial stages 4 and 6 suggesting higher nutrient availability, during these periods. The same pattern is observed for MIS2 and the last deglaciation. The opal record is fully supported by the organic carbon content and to the estimated productivity using foraminifera based FA20 and SIMMAX.28 transfer functions for a near location. The benthic δ13C record suggests less North Atlantic Deep Water (NADW) coincident with periods of higher productivity. The grain-size variations and magnetic properties, suggests stronger/faster bottom currents during cold phases, in agreement with a stronger component of Antarctic sourced Bottom Water (AABW) at the Eastern Atlantic Margin. The probable enhancement of AABW during these periods may also account for a higher preservation of siliceous biogenic particles at the ocean floor sediment/water interface. Given that MD01-2446 is placed far from the continent, productivity records should mainly reflect local conditions. Still, we should not fully discard the preservation of punctual influence of coastal processes derived from upwelling filament plumes at the Estremadura Plateau. Lebreiro et al., 1997 [Paleoceanography, 12, 718-727] reported for a near location, the dominance of pre-upwelling and post-upwelling related foraminifera species during MIS 6 implying less intense or persistent upwelling during MIS 6 than MIS 4. On the contrary, opal and organic carbon data reveals a clear increase in productivity also during MIS 6, reinforcing the idea that productivity variations are likely related to open ocean conditions and therefore, nutrients availability associated to the Atlantic Meridional Oceanic Circulation.

Open cycle ocean thermal energy conversion system structure

DOEpatents

Wittig, J. Michael

1980-01-01

A generally mushroom-shaped, open cycle OTEC system and distilled water producer which has a skirt-conduit structure extending from the enlarged portion of the mushroom to the ocean. The enlarged part of the mushroom houses a toroidal casing flash evaporator which produces steam which expands through a vertical rotor turbine, partially situated in the center of the blossom portion and partially situated in the mushroom's stem portion. Upon expansion through the turbine, the motive steam enters a shell and tube condenser annularly disposed about the rotor axis and axially situated beneath the turbine in the stem portion. Relatively warm ocean water is circulated up through the radially outer skirt-conduit structure entering the evaporator through a radially outer portion thereof, flashing a portion thereof into motive steam, and draining the unflashed portion from the evaporator through a radially inner skirt-conduit structure. Relatively cold cooling water enters the annular condenser through the radially inner edge and travels radially outwardly into a channel situated along the radially outer edge of the condenser. The channel is also included in the radially inner skirt-conduit structure. The cooling water is segregated from the potable, motive steam condensate which can be used for human consumption or other processes requiring high purity water. The expansion energy of the motive steam is partially converted into rotational mechanical energy of the turbine rotor when the steam is expanded through the shaft attached blades. Such mechanical energy drives a generator also included in the enlarged mushroom portion for producing electrical energy. Such power generation equipment arrangement provides a compact power system from which additional benefits may be obtained by fabricating the enclosing equipment, housings and component casings from low density materials, such as prestressed concrete, to permit those casings and housings to also function as a floating support vessel.

Global decadal climate variability driven by Southern Ocean convection

NASA Astrophysics Data System (ADS)

Marinov, I.; Cabre, A.

2016-02-01

Here we suggest a set of new "teleconnections" by which the Southern Ocean (SO) can induce anomalies in the tropical oceans and atmosphere. A 5000-year long control simulation in a coupled atmosphere-ocean model (CM2Mc, a low-resolution GFDL model) shows a natural, highly regular multi-decadal oscillation between periods of SO open sea convection and non-convective periods. This process happens naturally, with different frequencies and durations of convection across the majority of CMIP5 under preindustrial forcing (deLavergne et al., 2014). In our model, oscillations in Weddell Sea convection drive multidecadal variability in SO and global SSTs, as well as SO heat storage, with convective decades warm due to the heat released from the Circumpolar Deep Water and non-convective decades cold due to subsurface heat storage. Convective pulses drive local SST and sea ice variations south of 60S, immediately triggering changes in the Ferrell and Hadley cells, atmospheric energy budget and cross-equatorial heat exchange, ultimately influencing the position of the Intertropical Convergence Zone and rain patterns in the tropics. Additionally, the SO convection pulse is propagated to the tropics and the North Atlantic MOC via oceanic pathways on relatively fast (decadal) timescales, in agreement with recent observational constraints. Open sea convection is the major mode of Antarctic Bottom Water (AABW) formation in the CMIP5 models. Future improvements in the representation of shelf convection and sea-ice interaction in the SO are a clear necessity. These model improvements should render the AABW representation more realistic, and might influence (a) the connectivity of the SO with the rest of the planet, as described above and (b) the oceanic and global carbon cycle, of which the AABW is a fundamental conduit.

The Western South Atlantic Ocean in a High-CO2 World: Current Measurement Capabilities and Perspectives.

PubMed

Kerr, Rodrigo; da Cunha, Letícia C; Kikuchi, Ruy K P; Horta, Paulo A; Ito, Rosane G; Müller, Marius N; Orselli, Iole B M; Lencina-Avila, Jannine M; de Orte, Manoela R; Sordo, Laura; Pinheiro, Bárbara R; Bonou, Frédéric K; Schubert, Nadine; Bergstrom, Ellie; Copertino, Margareth S

2016-03-01

An international multi-disciplinary group of 24 researchers met to discuss ocean acidification (OA) during the Brazilian OA Network/Surface Ocean-Lower Atmosphere Study (BrOA/SOLAS) Workshop. Fifteen members of the BrOA Network (www.broa.furg.br) authored this review. The group concluded that identifying and evaluating the regional effects of OA is impossible without understanding the natural variability of seawater carbonate systems in marine ecosystems through a series of long-term observations. Here, we show that the western South Atlantic Ocean (WSAO) lacks appropriate observations for determining regional OA effects, including the effects of OA on key sensitive Brazilian ecosystems in this area. The impacts of OA likely affect marine life in coastal and oceanic ecosystems, with further social and economic consequences for Brazil and neighboring countries. Thus, we present (i) the diversity of coastal and open ocean ecosystems in the WSAO and emphasize their roles in the marine carbon cycle and biodiversity and their vulnerabilities to OA effects; (ii) ongoing observational, experimental, and modeling efforts that investigate OA in the WSAO; and (iii) highlights of the knowledge gaps, infrastructure deficiencies, and OA-related issues in the WSAO. Finally, this review outlines long-term actions that should be taken to manage marine ecosystems in this vast and unexplored ocean region.

Processes Driving Natural Acidification of Western Pacific Coral Reef Waters

NASA Astrophysics Data System (ADS)

Shamberger, K. E.; Cohen, A. L.; Golbuu, Y.; McCorkle, D. C.; Lentz, S. J.; Barkley, H. C.

2013-12-01

Rising levels of atmospheric carbon dioxide (CO2) are acidifying the oceans, reducing seawater pH, aragonite saturation state (Ωar) and the availability of carbonate ions (CO32-) that calcifying organisms use to build coral reefs. Today's most extensive reef ecosystems are located where open ocean CO32- concentration ([CO32-]) and Ωar exceed 200 μmol kg-1 and 3.3, respectively. However, high rates of biogeochemical cycling and long residence times of water can result in carbonate chemistry conditions within coral reef systems that differ greatly from those of nearby open ocean waters. In the Palauan archipelago, water moving across the reef platform is altered by both biological and hydrographic processes that combine to produce seawater pH, Ωar, [CO32-] significantly lower than that of open ocean source water. Just inshore of the barrier reefs, average Ωar values are 0.2 to 0.3 and pH values are 0.02 to 0.03 lower than they are offshore, declining further as water moves across the back reef, lagoon and into the meandering bays and inlets that characterize the Rock Islands. In the Rock Island bays, coral communities inhabit seawater with average Ωar values of 2.7 or less, and as low as 1.9. Levels of Ωar as low as these are not predicted to occur in the western tropical Pacific open ocean until near the end of the century. Calcification by coral reef organisms is the principal biological process responsible for lowering Ωar and pH, accounting for 68 - 99 % of the difference in Ωar between offshore source water and reef water at our sites. However, in the Rock Island bays where Ωar is lowest, CO2 production by net respiration contributes between 17 - 30 % of the difference in Ωar between offshore source water and reef water. Furthermore, the residence time of seawater in the Rock Island bays is much longer than at the well flushed exposed sites, enabling calcification and respiration to drive Ωar to very low levels despite lower net ecosystem calcification rates in the Rock Island bays than on the barrier reef.

Open-Ocean and Coastal Properties of Recent Major Tsunamis

NASA Astrophysics Data System (ADS)

Rabinovich, A.; Thomson, R.; Zaytsev, O.

2017-12-01

The properties of six major tsunamis during the period 2009-2015 (2009 Samoa; 2010 Chile; 2011 Tohoku; 2012 Haida Gwaii; 2014 and 2015 Chile) were thoroughly examined using coastal data from British Columbia, the U.S. West Coast and Mexico, and offshore open-ocean DART and NEPTUNE stations. Based on joint spectral analyses of the tsunamis and background noise, we have developed a method to suppress the influence of local topography and to use coastal observations to determine the underlying spectra of tsunami waves in the deep ocean. The "reconstructed" open-ocean tsunami spectra were found to be in close agreement with the actual tsunami spectra evaluated from the analysis of directly measured open-ocean tsunami records. We have further used the spectral estimates to parameterize tsunamis based on their integral open-ocean spectral characteristics. Three key parameters are introduced to describe individual tsunami events: (1) Integral open-ocean energy; (2) Amplification factor (increase of the mean coastal tsunami variance relative to the open-ocean variance); and (3) Tsunami colour, the frequency composition of the open-ocean tsunami waves. In particular, we found that the strongest tsunamis, associated with large source areas (the 2010 Chile and 2011 Tohoku) are "reddish" (indicating the dominance of low-frequency motions), while small-source events (the 2009 Samoa and 2012 Haida Gwaii) are "bluish" (indicating strong prevalence of high-frequency motions).

Arctic Deep Water Ferromanganese-Oxide Deposits Reflect the Unique Characteristics of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Hein, James R.; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe J.; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah R.; Till, Claire P.

2017-11-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, and HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits. The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ˜15 Myr ago.

Arctic deep-water ferromanganese-oxide deposits reflect the unique characteristics of the Arctic Ocean

USGS Publications Warehouse

Hein, James; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah; Till, Claire P.

2017-01-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits.The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ∼15 Myr ago.

50 CFR 648.15 - Facilitation of enforcement.

Code of Federal Regulations, 2011 CFR

2011-10-01

... surfclam and ocean quahog vessel owners and operators. (1) Surfclam and ocean quahog open access permitted vessels. Vessel owners or operators issued an open access surfclam or ocean quahog open access permit for.../or an Open Access Herring Permit that fished with midwater trawl gear pursuant to § 648.80(d). Such...

Atmospheric Nitrogen Deposition to the Oceans: Observation- and Model-Based Estimates

NASA Astrophysics Data System (ADS)

Baker, Alex; Altieri, Katye; Okin, Greg; Dentener, Frank; Uematsu, Mitsuo; Kanakidou, Maria; Sarin, Manmohan; Duce, Robert; Galloway, Jim; Keene, Bill; Singh, Arvind; Zamora, Lauren; Lamarque, Jean-Francois; Hsu, Shih-Chieh

2014-05-01

The reactive nitrogen (Nr) burden of the atmosphere has been increased by a factor of 3-4 by anthropogenic activity since the industrial revolution. This has led to large increases in the deposition of nitrate and ammonium to the surface waters of the open ocean, particularly downwind of major human population centres, such as those in North America, Europe and Southeast Asia. In oligotrophic waters, this deposition has the potential to significantly impact marine productivity and the global carbon cycle. Global-scale understanding of N deposition to the oceans is reliant on our ability to produce effective models of reactive nitrogen emission, atmospheric chemistry, transport and deposition (including deposition to the land surface). The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) recently completed a multi-model analysis of global N deposition, including comparisons to wet deposition observations from three regional networks in North America, Europe and Southeast Asia (Lamarque et al., Atmos. Chem. Phys., 13, 7977-8018, 2013). No similar datasets exist which would allow observation - model comparisons of wet deposition for the open oceans, because long-term wet deposition records are available for only a handful of remote island sites and rain collection over the open ocean itself is very difficult. In this work we attempt instead to use ~2600 observations of aerosol nitrate and ammonium concentrations, acquired chiefly from sampling aboard ships in the period 1995 - 2012, to assess the ACCMIP N deposition fields over the remote ocean. This database is non-uniformly distributed in time and space. We selected four ocean regions (the eastern North Atlantic, the South Atlantic, the northern Indian Ocean and northwest Pacific) where we considered the density and distribution of observational data is sufficient to provide effective comparison to the model ensemble. Two of these regions are adjacent to the land networks used in the ACCMIP comparison, while the others are far removed from land regions for which the model output has been rigorously compared to observational data. Here we will present calculated dry deposition fluxes of nitrate and ammonium from average observed concentrations in these regions, using deposition velocities of 0.9 cm/s and 0.1 cm/s respectively, and the results of a comparison of these fluxes to the ACCMIP model ensemble product. Uncertainties in the comparison and potential sources of bias between the observations and model will be discussed.

Dissolved organic carbon export and internal cycling in small, headwater lakes

USGS Publications Warehouse

Stets, Edward G.; Striegl, Robert G.; Aiken, George R.

2010-01-01

Carbon (C) cycling in freshwater lakes is intense but poorly integrated into our current understanding of overall C transport from the land to the oceans. We quantified dissolved organic carbon export (DOCX) and compared it with modeled gross DOC mineralization (DOCR) to determine whether hydrologic or within-lake processes dominated DOC cycling in a small headwaters watershed in Minnesota, USA. We also used DOC optical properties to gather information about DOC sources. We then compared our results to a data set of approximately 1500 lakes in the Eastern USA (Eastern Lake Survey, ELS, data set) to place our results in context of lakes more broadly. In the open-basin lakes in our watershed (n = 5), DOCX ranged from 60 to 183 g C m−2 lake area yr−1, whereas DOCR ranged from 15 to 21 g C m−2 lake area yr−1, emphasizing that lateral DOC fluxes dominated. DOCX calculated in our study watershed clustered near the 75th percentile of open-basin lakes in the ELS data set, suggesting that these results were not unusual. In contrast, DOCX in closed-basin lakes (n = 2) was approximately 5 g C m−2 lake area yr−1, whereas DOCR was 37 to 42 g C m−2 lake area yr−1, suggesting that internal C cycling dominated. In the ELS data set, median DOCX was 32 and 12 g C m−2 yr−1 in open-basin and closed-basin lakes, respectively. Although not as high as what was observed in our study watershed, DOCX is an important component of lake C flux more generally, particularly in open-basin lakes.

Glacial-interglacial vegetation dynamics in South Eastern Africa coupled to sea surface temperature variations in the Western Indian Ocean

NASA Astrophysics Data System (ADS)

Dupont, L. M.; Caley, T.; Kim, J.-H.; Castañeda, I.; Malaizé, B.; Giraudeau, J.

2011-11-01

Glacial-interglacial fluctuations in the vegetation of South Africa might elucidate the climate system at the edge of the tropics between the Indian and Atlantic Oceans. However, vegetation records covering a full glacial cycle have only been published from the eastern South Atlantic. We present a pollen record of the marine core MD96-2048 retrieved by the Marion Dufresne from the Indian Ocean ∼120 km south of the Limpopo River mouth. The sedimentation at the site is slow and continuous. The upper 6 m (spanning the past 342 Ka) have been analysed for pollen and spores at millennial resolution. The terrestrial pollen assemblages indicate that during interglacials, the vegetation of eastern South Africa and southern Mozambique largely consisted of evergreen and deciduous forests. During glacials open mountainous scrubland dominated. Montane forest with Podocarpus extended during humid periods was favoured by strong local insolation. Correlation with the sea surface temperature record of the same core indicates that the extension of mountainous scrubland primarily depends on sea surface temperatures of the Agulhas Current. Our record corroborates terrestrial evidence of the extension of open mountainous scrubland (including fynbos-like species of the high-altitude Grassland biome) for the last glacial as well as for other glacial periods of the past 300 Ka.

Motile behaviour of the free-living planktonic ciliate Zoothamnium pelagicum (Ciliophora, Peritrichia).

PubMed

Gómez, Fernando

2017-06-01

Zoothamnium pelagicum is the only free-floating species among ∼1000 peritrich ciliates that develops its complete life cycle in the open ocean. In the NW Mediterranean Sea, Z. pelagicum was usually associated with ectobiotic bacteria, while in the South Atlantic Ocean was sometimes fouled by the diatom Licmophora. Each colony constituted a radial branch that joined at its base with other colonies to form a lens-shaped pseudocolony of up to 400 zooids. The cilia beat slowly, propelling the expanded pseudocolony in the direction of the concave face. Contraction was triggered by external stimuli (threat) or occurred spontaneously. Frame-by-frame analyses of high-speed camera sequences revealed that during contraction the pseudocolony reduced its diameter 70-75% in 3-3.2ms with peak velocity up to 350mms -1 . The contraction induced a forward jump of 1-2mm that attained a peak speed of 110mms -1 (∼250pseudocolony lengthss -1 ) in 5ms after onset. This medusa-like locomotion at low Reynolds numbers allowed the pseudocolony to exploit new patches of food resources, as well as to escape from predators. Zoothamnium pelagicum has been able to proliferate in the oligotrophic open ocean, while its sessile counterparts are restricted to eutrophic environments. Copyright © 2017 Elsevier GmbH. All rights reserved.

Ocean deoxygenation in a warming world.

PubMed

Keeling, Ralph E; Körtzinger, Arne; Gruber, Nicolas

2010-01-01

Ocean warming and increased stratification of the upper ocean caused by global climate change will likely lead to declines in dissolved O2 in the ocean interior (ocean deoxygenation) with implications for ocean productivity, nutrient cycling, carbon cycling, and marine habitat. Ocean models predict declines of 1 to 7% in the global ocean O2 inventory over the next century, with declines continuing for a thousand years or more into the future. An important consequence may be an expansion in the area and volume of so-called oxygen minimum zones, where O2 levels are too low to support many macrofauna and profound changes in biogeochemical cycling occur. Significant deoxygenation has occurred over the past 50 years in the North Pacific and tropical oceans, suggesting larger changes are looming. The potential for larger O2 declines in the future suggests the need for an improved observing system for tracking ocean 02 changes.

Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008

USGS Publications Warehouse

Robbins, L.L.; Coble, P.G.; Clayton, T.D.; Cai, W.J.

2009-01-01

Despite their relatively small surface area, ocean margins may have a significant impact on global biogeochemical cycles and, potentially, the global air-sea fluxes of carbon dioxide. Margins are characterized by intense geochemical and biological processing of carbon and other elements and exchange large amounts of matter and energy with the open ocean. The area-specific rates of productivity, biogeochemical cycling, and organic/inorganic matter sequestration are high in coastal margins, with as much as half of the global integrated new production occurring over the continental shelves and slopes (Walsh, 1991; Doney and Hood, 2002; Jahnke, in press). However, the current lack of knowledge and understanding of biogeochemical processes occurring at the ocean margins has left them largely ignored in most of the previous global assessments of the oceanic carbon cycle (Doney and Hood, 2002). A major source of North American and global uncertainty is the Gulf of Mexico, a large semi-enclosed subtropical basin bordered by the United States, Mexico, and Cuba. Like many of the marginal oceans worldwide, the Gulf of Mexico remains largely unsampled and poorly characterized in terms of its air-sea exchange of carbon dioxide and other carbon fluxes. In May 2008, the Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico was held in St. Petersburg, FL, to address the information gaps of carbon fluxes associated with the Gulf of Mexico and to offer recommendations to guide future research. The meeting was attended by over 90 participants from over 50 U.S. and Mexican institutions and agencies. The Ocean Carbon and Biogeochemistry program (OCB; http://www.us-ocb.org/) sponsored this workshop with support from the National Science Foundation, the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the U.S. Geological Survey, and the University of South Florida. The goal of the workshop was to bring together researchers from multiple disciplines studying terrestrial, aquatic, and marine ecosystems to discuss the state of knowledge in carbon fluxes in the Gulf of Mexico, data gaps, and overarching questions in the Gulf of Mexico system. The discussions at the workshop were intended to stimulate integrated studies of marine and terrestrial biogeochemical cycles and associated ecosystems that will help to establish the role of the Gulf of Mexico in the carbon cycle and how it might evolve in the face of environmental change. The information derived from the plenary sessions, questions, and recommendations formulated by the participants will drive future research projects. Further discussion of carbon dynamics is needed to address scales of variability, the infrastructure required for study, and the modeling framework for cross-system integration. During the workshop, participants discussed and provided a number of priorities and recommendations, which are listed on p. 2 of the report. Participants recognized that the key to understanding the Gulf of Mexico system requires international collaboration with scientists from countries adjacent to the Gulf of Mexico. Improved collaboration across existing research community boundaries will be critical and should be encouraged by the funding agencies.

Enhanced chemical weathering as a geoengineering strategy to reduce atmospheric carbon dioxide, supply nutrients, and mitigate ocean acidification

NASA Astrophysics Data System (ADS)

Hartmann, Jens; West, A. Joshua; Renforth, Phil; Köhler, Peter; De La Rocha, Christina L.; Wolf-Gladrow, Dieter A.; Dürr, Hans H.; Scheffran, Jürgen

2013-04-01

weathering is an integral part of both the rock and carbon cycles and is being affected by changes in land use, particularly as a result of agricultural practices such as tilling, mineral fertilization, or liming to adjust soil pH. These human activities have already altered the terrestrial chemical cycles and land-ocean flux of major elements, although the extent remains difficult to quantify. When deployed on a grand scale, Enhanced Weathering (a form of mineral fertilization), the application of finely ground minerals over the land surface, could be used to remove CO2 from the atmosphere. The release of cations during the dissolution of such silicate minerals would convert dissolved CO2 to bicarbonate, increasing the alkalinity and pH of natural waters. Some products of mineral dissolution would precipitate in soils or be taken up by ecosystems, but a significant portion would be transported to the coastal zone and the open ocean, where the increase in alkalinity would partially counteract "ocean acidification" associated with the current marked increase in atmospheric CO2. Other elements released during this mineral dissolution, like Si, P, or K, could stimulate biological productivity, further helping to remove CO2 from the atmosphere. On land, the terrestrial carbon pool would likely increase in response to Enhanced Weathering in areas where ecosystem growth rates are currently limited by one of the nutrients that would be released during mineral dissolution. In the ocean, the biological carbon pumps (which export organic matter and CaCO3 to the deep ocean) may be altered by the resulting influx of nutrients and alkalinity to the ocean. This review merges current interdisciplinary knowledge about Enhanced Weathering, the processes involved, and the applicability as well as some of the consequences and risks of applying the method.

Southern Ocean phytoplankton turnover in response to stepwise Antarctic cooling over the past 15 million years

PubMed Central

Crampton, James S.; Cody, Rosie D.; Levy, Richard; Harwood, David; McKay, Robert; Naish, Tim R.

2016-01-01

It is not clear how Southern Ocean phytoplankton communities, which form the base of the marine food web and are a crucial element of the carbon cycle, respond to major environmental disturbance. Here, we use a new model ensemble reconstruction of diatom speciation and extinction rates to examine phytoplankton response to climate change in the southern high latitudes over the past 15 My. We identify five major episodes of species turnover (origination rate plus extinction rate) that were coincident with times of cooling in southern high-latitude climate, Antarctic ice sheet growth across the continental shelves, and associated seasonal sea-ice expansion across the Southern Ocean. We infer that past plankton turnover occurred when a warmer-than-present climate was terminated by a major period of glaciation that resulted in loss of open-ocean habitat south of the polar front, driving non-ice adapted diatoms to regional or global extinction. These findings suggest, therefore, that Southern Ocean phytoplankton communities tolerate “baseline” variability on glacial–interglacial timescales but are sensitive to large-scale changes in mean climate state driven by a combination of long-period variations in orbital forcing and atmospheric carbon dioxide perturbations. PMID:27274061

Southern Ocean phytoplankton turnover in response to stepwise Antarctic cooling over the past 15 million years

NASA Astrophysics Data System (ADS)

Crampton, James S.; Cody, Rosie D.; Levy, Richard; Harwood, David; McKay, Robert; Naish, Tim R.

2016-06-01

It is not clear how Southern Ocean phytoplankton communities, which form the base of the marine food web and are a crucial element of the carbon cycle, respond to major environmental disturbance. Here, we use a new model ensemble reconstruction of diatom speciation and extinction rates to examine phytoplankton response to climate change in the southern high latitudes over the past 15 My. We identify five major episodes of species turnover (origination rate plus extinction rate) that were coincident with times of cooling in southern high-latitude climate, Antarctic ice sheet growth across the continental shelves, and associated seasonal sea-ice expansion across the Southern Ocean. We infer that past plankton turnover occurred when a warmer-than-present climate was terminated by a major period of glaciation that resulted in loss of open-ocean habitat south of the polar front, driving non-ice adapted diatoms to regional or global extinction. These findings suggest, therefore, that Southern Ocean phytoplankton communities tolerate “baseline” variability on glacial-interglacial timescales but are sensitive to large-scale changes in mean climate state driven by a combination of long-period variations in orbital forcing and atmospheric carbon dioxide perturbations.

Characterising the short-term sensitivity of Californian intertidal community calcification to ocean acidification

NASA Astrophysics Data System (ADS)

Kwiatkowski, Lester; Caldeira, Ken

2015-04-01

Anthropogenic emissions of CO2 and invasion of part of this CO2 into the oceans results in a decrease in seawater pH and a lowering of the calcium carbonate saturation state. The historic and projected decrease of the calcium carbonate saturation state of seawater has the potential to compromise the ability of many marine calcifying organisms to form their calcium carbonate shells or skeletons and is likely to have significant ocean ecosystem impacts over the 21st Century. In laboratory manipulations temperate calcifying organisms have been shown to exhibit reduced calcification as a result of CO2 addition. However, very few experiments have observed how calcification in temperate systems responds to natural variations in seawater carbonate chemistry. We assess the community level sensitivity of Californian tidal pool calcification rates to variability in the calcium carbonate saturation state. Our tidal pool study sites at Bodega Bay in Northern California experience extreme variation in low tide carbonate saturation state due to photosynthetic activity and the time at which the pools are isolated from the open ocean. During our study period, we observed aragonite saturation levels ranging from 0.5 to 9. Photosynthetic activity is largely dependent on temperature and photosynthetic active radiation which vary on a diurnal timescale whereas the time at which pools are isolated from open seawater, and thus the amount by which tide pool carbonate chemistry differs from that of open ocean waters, is largely a consequence of tidal period which varies on a lunar cycle. Because there are substantial uncorrelated components of light, temperature, and seawater carbonate chemistry in our data, one can separate the influence of carbonate saturation state on calcification from the influence of temperature and PAR. This provides an opportunity to characterise the short-timescale sensitivity of tidal pool calcification rates to changes in carbonate saturation state. We show that on such timescales community level rates of daytime calcification are not strongly influenced by variability in carbonate saturation state. This suggests that these intertidal communities may be more resilient to projected ocean acidification than previously thought, although extending this work to consider longer timescales would be required to more firmly support this hypothesis.

Photoreduction of Terrigenous Fe-Humic Substances Leads to Bioavailable Iron in Oceans.

PubMed

Blazevic, Amir; Orlowska, Ewelina; Kandioller, Wolfgang; Jirsa, Franz; Keppler, Bernhard K; Tafili-Kryeziu, Myrvete; Linert, Wolfgang; Krachler, Rudolf F; Krachler, Regina; Rompel, Annette

2016-05-23

Humic substances (HS) are important iron chelators responsible for the transport of iron from freshwater systems to the open sea, where iron is essential for marine organisms. Evidence suggests that iron complexed to HS comprises the bulk of the iron ligand pool in near-coastal waters and shelf seas. River-derived HS have been investigated to study their transport to, and dwell in oceanic waters. A library of iron model compounds and river-derived Fe-HS samples were probed in a combined X-ray absorption spectroscopy (XAS) and valence-to-core X-ray emission spectroscopy (VtC-XES) study at the Fe K-edge. The analyses performed revealed that iron complexation in HS samples is only dependent on oxygen-containing HS functional groups, such as carboxyl and phenol. The photoreduction mechanism of Fe III -HS in oceanic conditions into bioavailable aquatic Fe II forms, highlights the importance of river-derived HS as an iron source for marine organisms. Consequently, such mechanisms are a vital component of the upper-ocean iron biogeochemistry cycle.

Climate change, pink salmon, and the nexus between bottom-up and top-down forcing in the subarctic Pacific Ocean and Bering Sea.

PubMed

Springer, Alan M; van Vliet, Gus B

2014-05-06

Climate change in the last century was associated with spectacular growth of many wild Pacific salmon stocks in the North Pacific Ocean and Bering Sea, apparently through bottom-up forcing linking meteorology to ocean physics, water temperature, and plankton production. One species in particular, pink salmon, became so numerous by the 1990s that they began to dominate other species of salmon for prey resources and to exert top-down control in the open ocean ecosystem. Information from long-term monitoring of seabirds in the Aleutian Islands and Bering Sea reveals that the sphere of influence of pink salmon is much larger than previously known. Seabirds, pink salmon, other species of salmon, and by extension other higher-order predators, are tightly linked ecologically and must be included in international management and conservation policies for sustaining all species that compete for common, finite resource pools. These data further emphasize that the unique 2-y cycle in abundance of pink salmon drives interannual shifts between two alternate states of a complex marine ecosystem.

A Modern Operating System for Near-real-time Environmental Observatories

NASA Astrophysics Data System (ADS)

Orcutt, John; Vernon, Frank

2014-05-01

The NSF Ocean Observatory Initiative (OOI) provided an opportunity for expanding the capabilities for managing open, near-real-time (latencies of seconds) data from ocean observatories. The sensors deployed in this system largely return data from seafloor, cabled fiber optic cables as well as satellite telemetry. Bandwidth demands range from high-definition movies to the transmission of data via Iridium satellite. The extended Internet also provides an opportunity to not only return data, but to also control the sensors and platforms that comprise the observatory. The data themselves are openly available to any users. In order to provide heightened network security and overall reliability, the connections to and from the sensors/platforms are managed without Layer 3 of the Internet, but instead rely upon message passing using an open protocol termed Advanced Queuing Messaging Protocol (AMQP). The highest bandwidths in the system are in the Regional Scale Network (RSN) off Oregon and Washington and on the continent with highly reliable network connections between observatory components at 10 Gbps. The maintenance of metadata and life cycle histories of sensors and platforms is critical for providing data provenance over the years. The integrated cyberinfrastructure is best thought of as an operating system for the observatory - like the data, the software is also open and can be readily applied to new observatories, for example, in the rapidly evolving Arctic.

Authigenic carbonate precipitation at the end-Guadalupian (Middle Permian) in China: Implications for the carbon cycle in ancient anoxic oceans

NASA Astrophysics Data System (ADS)

Saitoh, Masafumi; Ueno, Yuichiro; Isozaki, Yukio; Shibuya, Takazo; Yao, Jianxin; Ji, Zhansheng; Shozugawa, Katsumi; Matsuo, Motoyuki; Yoshida, Naohiro

2015-12-01

Carbonate precipitation is a major process in the global carbon cycle. It was recently proposed that authigenic carbonate (carbonate precipitated in situ at the sediment-water interface and/or within the sediment) played a major role in the carbon cycle throughout Earth's history. The carbon isotopic composition of authigenic carbonates in ancient oceans have been assumed to be significantly lower than that of dissolved inorganic carbon (DIC) in seawater, as is observed in the modern oceans. However, the δ13Ccarb values of authigenic carbonates in the past has not been analyzed in detail. Here, we report authigenic carbonates in the uppermost Guadalupian (Middle Permian) rocks at Chaotian, Sichuan, South China. Monocrystalline calcite crystals <20 mm long are common in the black mudstone/chert sequence that was deposited on a relatively deep anoxic slope/basin along the continental margin. Textures of the crystals indicate in situ precipitation on the seafloor and/or within the sediments. The calcite precipitation corresponds stratigraphically with denitrification and sulfate reduction in the anoxic deep-water mass, as indicated by previously reported nitrogen and sulfur isotope records, respectively. Relatively high δ13Ccarb values of the authigenic carbonates (largely -1 ‰) compared with those of organic matter in the rocks (ca. -26 ‰) suggest that the main carbon source of the carbonates was DIC in the water column. The calcite crystals precipitated in an open system with respect to carbonate, possibly near the sediment-water interface rather than deep within the sediments. The δ13Ccarb values of the carbonates were close to the δ13CDIC value of seawater due to mixing of 13C-depleted remineralized organic carbon (that was released into the water column by the water-mass anaerobic respiration) with the large DIC pool in the oceans. Our results imply that δ13Ccarb values of authigenic carbonates in the anoxic oceans might have been systematically different from the values in the oxic oceans in Earth's history, controlled by the depth of the redoxcline in the water column and sediments. If our model is correct, authigenic carbonates with relatively high δ13Ccarb values in the ancient anoxic oceans may have had a less substantial influence on the bulk δ13Ccarb values in geologic records than has been previously suggested.

Global distribution of naturally occurring marine hypoxia on continental margins

NASA Astrophysics Data System (ADS)

Helly, John J.; Levin, Lisa A.

2004-09-01

Hypoxia in the ocean influences biogeochemical cycling of elements, the distribution of marine species and the economic well being of many coastal countries. Previous delineations of hypoxic environments focus on those in enclosed seas where hypoxia may be exacerbated by anthropogenically induced eutrophication. Permanently hypoxic water masses in the open ocean, referred to as oxygen minimum zones, impinge on a much larger seafloor surface area along continental margins of the eastern Pacific, Indian and western Atlantic Oceans. We provide the first global quantification of naturally hypoxic continental margin floor by determining upper and lower oxygen minimum zone depth boundaries from hydrographic data and computing the area between the isobaths using seafloor topography. This approach reveals that there are over one million km 2 of permanently hypoxic shelf and bathyal sea floor, where dissolved oxygen is <0.5 ml l -1; over half (59%) occurs in the northern Indian Ocean. We also document strong variation in the intensity, vertical position and thickness of the OMZ as a function of latitude in the eastern Pacific Ocean and as a function of longitude in the northern Indian Ocean. Seafloor OMZs are regions of low biodiversity and are inhospitable to most commercially valuable marine resources, but support a fascinating array of protozoan and metazoan adaptations to hypoxic conditions.

Global Modeling Study of the Bioavailable Atmospheric Iron Supply to the Global Ocean

NASA Astrophysics Data System (ADS)

Myriokefalitakis, S.; Krol, M. C.; van Noije, T.; Le Sager, P.

2017-12-01

Atmospheric deposition of trace constituents acts as a nutrient source to the open ocean and affect marine ecosystem. Dust is known as a major source of nutrients to the global ocean, but only a fraction of these nutrients is released in a bioavailable form that can be assimilated by the marine biota. Iron (Fe) is a key micronutrient that significantly modulates gross primary production in the High-Nutrient-Low-Chlorophyll (HNLC) oceans, where macronutrients like nitrate are abundant, but primary production is limited by Fe scarcity. The global atmospheric Fe cycle is here parameterized in the state-of-the-art global Earth System Model EC-Earth. The model takes into account the primary emissions of both insoluble and soluble Fe forms, associated with mineral dust and combustion aerosols. The impact of atmospheric acidity and organic ligands on mineral dissolution processes, is parameterized based on updated experimental and theoretical findings. Model results are also evaluated against available observations. Overall, the link between the labile Fe atmospheric deposition and atmospheric composition changes is here demonstrated and quantified. This work has been financed by the Marie-Curie H2020-MSCA-IF-2015 grant (ID 705652) ODEON (Online DEposition over OceaNs; modeling the effect of air pollution on ocean bio-geochemistry in an Earth System Model).

Terrestrial and marine perspectives on modeling organic matter degradation pathways.

PubMed

Burd, Adrian B; Frey, Serita; Cabre, Anna; Ito, Takamitsu; Levine, Naomi M; Lønborg, Christian; Long, Matthew; Mauritz, Marguerite; Thomas, R Quinn; Stephens, Brandon M; Vanwalleghem, Tom; Zeng, Ning

2016-01-01

Organic matter (OM) plays a major role in both terrestrial and oceanic biogeochemical cycles. The amount of carbon stored in these systems is far greater than that of carbon dioxide (CO2 ) in the atmosphere, and annual fluxes of CO2 from these pools to the atmosphere exceed those from fossil fuel combustion. Understanding the processes that determine the fate of detrital material is important for predicting the effects that climate change will have on feedbacks to the global carbon cycle. However, Earth System Models (ESMs) typically utilize very simple formulations of processes affecting the mineralization and storage of detrital OM. Recent changes in our view of the nature of this material and the factors controlling its transformation have yet to find their way into models. In this review, we highlight the current understanding of the role and cycling of detrital OM in terrestrial and marine systems and examine how this pool of material is represented in ESMs. We include a discussion of the different mineralization pathways available as organic matter moves from soils, through inland waters to coastal systems and ultimately into open ocean environments. We argue that there is strong commonality between aspects of OM transformation in both terrestrial and marine systems and that our respective scientific communities would benefit from closer collaboration. © 2015 John Wiley & Sons Ltd.

Evaluating the Impact of Changes in Oceanic Dissolved Oxygen on Marine Nitrous Oxide

NASA Astrophysics Data System (ADS)

Suntharalingam, Parvadha; Buitenhuis, Erik; Schmidtko, Sunke; Andrews, Oliver; LeQuere, Corinne

2013-04-01

Emissions of the greenhouse gas nitrous-oxide (N2O) from oceanic oxygen minimum zones (OMZs) in the Equatorial Pacific and Northwest Indian Ocean are believed to provide a significant portion of the global oceanic flux to the atmosphere. Mechanisms of marine N2O production and consumption in these regions display significant sensitivity to ambient oxygen, with high yields at low oxygen levels (O2 < 50 micromol/L), and N2O depletion via denitrification in anoxic zones. These OMZ regions display large gradients in sub-surface N2O, and high rates of N2O turnover that far exceed those observed in the open ocean. Recent studies have suggested that possible expansion of oceanic OMZs in a warming climate, could lead to significant changes in N2O emissions from these zones. In this analysis we employ a global ocean biogeochemistry model (NEMO-PlankTOM), which includes representation of the marine N2O cycle, to explore the impact of changes in dissolved oxygen on the ocean-atmosphere N2O flux. We focus on the period 1960-2000, and evaluate the impact of estimated changes in ocean oxygen from two alternative sources : (a) the observationally-based upper-ocean oxygen distributions and trends of Stramma et al. [2012]; (b) simulated oxygen distributions and temporal variations from a set of CMIP5 Earth System models. We will inter-compare the oceanic N2O estimates derived from these alternative scenarios of ocean de-oxygenation. We will also discuss the implications of our results for the ability to reliably predict changes in N2O emissions under potential expansion of oceanic OMZs, particularly in view of the recently noted discrepancies between observed and modeled trends in oceanic oxygen by Stramma et al. [2012].

Oceanic crustal carbon cycle drives 26-million-year atmospheric carbon dioxide periodicities.

PubMed

Müller, R Dietmar; Dutkiewicz, Adriana

2018-02-01

Atmospheric carbon dioxide (CO 2 ) data for the last 420 million years (My) show long-term fluctuations related to supercontinent cycles as well as shorter cycles at 26 to 32 My whose origin is unknown. Periodicities of 26 to 30 My occur in diverse geological phenomena including mass extinctions, flood basalt volcanism, ocean anoxic events, deposition of massive evaporites, sequence boundaries, and orogenic events and have previously been linked to an extraterrestrial mechanism. The vast oceanic crustal carbon reservoir is an alternative potential driving force of climate fluctuations at these time scales, with hydrothermal crustal carbon uptake occurring mostly in young crust with a strong dependence on ocean bottom water temperature. We combine a global plate model and oceanic paleo-age grids with estimates of paleo-ocean bottom water temperatures to track the evolution of the oceanic crustal carbon reservoir over the past 230 My. We show that seafloor spreading rates as well as the storage, subduction, and emission of oceanic crustal and mantle CO 2 fluctuate with a period of 26 My. A connection with seafloor spreading rates and equivalent cycles in subduction zone rollback suggests that these periodicities are driven by the dynamics of subduction zone migration. The oceanic crust-mantle carbon cycle is thus a previously overlooked mechanism that connects plate tectonic pulsing with fluctuations in atmospheric carbon and surface environments.

Oceanic crustal carbon cycle drives 26-million-year atmospheric carbon dioxide periodicities

PubMed Central

Müller, R. Dietmar; Dutkiewicz, Adriana

2018-01-01

Atmospheric carbon dioxide (CO2) data for the last 420 million years (My) show long-term fluctuations related to supercontinent cycles as well as shorter cycles at 26 to 32 My whose origin is unknown. Periodicities of 26 to 30 My occur in diverse geological phenomena including mass extinctions, flood basalt volcanism, ocean anoxic events, deposition of massive evaporites, sequence boundaries, and orogenic events and have previously been linked to an extraterrestrial mechanism. The vast oceanic crustal carbon reservoir is an alternative potential driving force of climate fluctuations at these time scales, with hydrothermal crustal carbon uptake occurring mostly in young crust with a strong dependence on ocean bottom water temperature. We combine a global plate model and oceanic paleo-age grids with estimates of paleo-ocean bottom water temperatures to track the evolution of the oceanic crustal carbon reservoir over the past 230 My. We show that seafloor spreading rates as well as the storage, subduction, and emission of oceanic crustal and mantle CO2 fluctuate with a period of 26 My. A connection with seafloor spreading rates and equivalent cycles in subduction zone rollback suggests that these periodicities are driven by the dynamics of subduction zone migration. The oceanic crust-mantle carbon cycle is thus a previously overlooked mechanism that connects plate tectonic pulsing with fluctuations in atmospheric carbon and surface environments. PMID:29457135

Evaporative fractionation of marine water isotopes in the Arctic Ocean help understand a changing Arctic water cycle

NASA Astrophysics Data System (ADS)

Klein, E. S.; Welker, J. M.

2017-12-01

Most of the global hydrologic cycle occurs in oceanic waters. This oceanic derived moisture is critical to the precipitation and evapotranspiration regimes that influence terrestrial Earth systems. Thus understanding oceanic water processes has important global implications for our knowledge of modern and past hydrologic cycles. As they are influenced by environmental variables such as sea surface temperature and atmospheric humidity, water isotope ratios (e.g., δ18O, δ2H) can help understand the patterns driving the water cycle. However, our knowledge of marine isotopes is relatively limited. In particular, the fractionation of water isotopes during evaporation of oceanic water, essentially the start of the hydrologic cycle, is largely based on theoretical relationships derived from spatially and temporally limited data sets. This constrained understanding of oceanic evaporation fractionation patterns is especially pronounced in the rapidly changing Arctic Ocean. These changes are associated with reduced sea ice coverage, which is increasing the amount of local Artic Ocean sourced moisture in atmospheric and terrestrial systems and amplifying the Arctic hydrologic cycle. Here we present new data revealing the nuances of evaporative fractionation of Arctic Ocean water isotopes with the first collection of continuous, contemporaneous sea water and vapor isotopes. These data, collected in situ aboard the icebreaker Healy, show that the difference between actual ocean vapor isotope values and vapor values estimated by the closure equation increases progressively with latitude (especially beyond 70°) and varies between δ18O and δ2H. These differences are likely due to more isotopic mixing in the troposphere and/or closure equation assumptions inapplicable to Arctic regions. Moreover, we find: 1) a positive relationship between fractionation magnitude and latitude; and 2) the influence of evaporative fractionation from environmental variables such as wind and relative humidity reverses with the presence of sea ice. These new data increase our understanding of the patterns and processes governing past, present, and future changes to the Arctic hydrologic cycle.

Salinity Remote Sensing and the Study of the Global Water Cycle

NASA Technical Reports Server (NTRS)

Lagerloef, G. S. E.; LeVine, David M.; Chao, Y.; Colomb, F. Raul; Font, J.

2007-01-01

The SMOS and AquariusISAC-D satellite missions will begin a new era to map the global sea surface salinity (SSS) field and its variability from space within the next twothree years. They will provide critical data needed to study the interactions between the ocean circulation, global water cycle and climate. Key scientific issues to address are (1) mapping large expanses of the ocean where conventional SSS data do not yet exist, (2) understanding the seasonal and interannual SSS variations and the link to precipitation, evaporation and sea-ice patterns, (3) links between SSS and variations in the oceanic overturning circulation, (4) air-sea coupling processes in the tropics that influence El Nino, and (4) closing the marine freshwater budget. There is a growing body of oceanographic evidence in the form of salinity trends that portend significant changes in the hydrologic cycle. Over the past several decades, highlatitude oceans have become fresher while the subtropical oceans have become saltier. This change is slowly spreading into the subsurface ocean layers and may be affecting the strength of the ocean's therrnohaline overturning circulation. Salinity is directly linked to the ocean dynamics through the density distribution, and provides an important signature of the global water cycle. The distribution and variation of oceanic salinity is therefore attracting increasing scientific attention due to the relationship to the global water cycle and its influence on circulation, mixing, and climate processes. The oceans dominate the water cycle by providing 86% of global surface evaporation (E) and receiving 78% of global precipitation (P). Regional differences in E-P, land runoff, and the melting or freezing of ice affect the salinity of surface water. Direct observations of E-P over the ocean have large uncertainty, with discrepancies between the various state-of-the-art precipitation analyses of a factor of two or more in many regions. Quantifying the climatic influence of the oceanic water cycle requires more accurately resolving the net air-sea water flux. Measuring global SSS trends on seasonal to interannual timescales by satellite is fundamental to this problem because the SSS trends represent detectable time-integrated signals of the variable marine hydrological cycle. Satellite measurements, coupled with an array of in situ observations, will provide global synoptic SSS fields for the first time history. These data will provide a strong constraint on climate models and data assimilation efforts, which must properly represent the freshwater budget in terms of E-P, ocean advection and surface layer mixing in order to accurately simulate the true ocean state. The SSS fields will allow us to quantify the covariability between the SSS and the strong seasonal E-P cycle in the tropics and high latitudes. Field measurement campaigns to exploit satellite and in situ measurements to close the seasonal E-P cycle over an ocean region are being considered. Lastly the satellite systems will monitor and trace the large long-lived SSS anomalies from year to year that have the potential to influence El Nino and the large scale ocean circulation.

Monitoring and Predicting the Export and Fate of Global Ocean Net Primary Production: The EXPORTS Field Program

NASA Astrophysics Data System (ADS)

Exports Science Definition Team

2016-04-01

Ocean ecosystems play a critical role in the Earth's carbon cycle and its quantification on global scales remains one of the greatest challenges in global ocean biogeochemistry. The goal of the EXport Processes in the Ocean from Remote Sensing (EXPORTS) science plan is to develop a predictive understanding of the export and fate of global ocean primary production and its implications for the Earth's carbon cycle in present and future climates. NASA's satellite ocean-color data record has revolutionized our understanding of global marine systems. EXPORTS is designed to advance the utility of NASA ocean color assets to predict how changes in ocean primary production will impact the global carbon cycle. EXPORTS will create a predictive understanding of both the export of organic carbon from the euphotic zone and its fate in the underlying "twilight zone" (depths of 500 m or more) where variable fractions of exported organic carbon are respired back to CO2. Ultimately, it is the sequestration of deep organic carbon transport that defines the impact of ocean biota on atmospheric CO2 levels and hence climate. EXPORTS will generate a new, detailed understanding of ocean carbon transport processes and pathways linking upper ocean phytoplankton processes to the export and fate of organic matter in the underlying twilight zone using a combination of field campaigns, remote sensing and numerical modeling. The overarching objective for EXPORTS is to ensure the success of future satellite missions by establishing mechanistic relationships between remotely sensed signals and carbon cycle processes. Through a process-oriented approach, EXPORTS will foster new insights on ocean carbon cycling that will maximize its societal relevance and be a key component in the U.S. investment to understand Earth as an integrated system.

Autonomous observing platform CO2 data shed new light on the Southern Ocean carbon cycle

NASA Astrophysics Data System (ADS)

Olsen, Are

2017-06-01

While the number of surface ocean CO2 partial pressure (pCO2) measurements has soared the recent decades, the Southern Ocean remains undersampled. Williams et al. (2017, https://doi.org/10.1002/2016GB005541) now present pCO2 estimates based on data from pH-sensor equipped Bio-Argo floats, which have been measuring in the Southern Ocean since 2014. The authors demonstrate the utility of these data for understanding the carbon cycle in this region, which has a large influence on the distribution of CO2 between the ocean and atmosphere. Biogeochemical sensors deployed on autonomous platforms hold the potential to shape our view of the ocean carbon cycle in the coming decades.

A high-resolution time-depth view of dimethylsulphide cycling in the surface sea

PubMed Central

Royer, S.-J.; Galí, M.; Mahajan, A. S.; Ross, O. N.; Pérez, G. L.; Saltzman, E. S.; Simó, R.

2016-01-01

Emission of the trace gas dimethylsulphide (DMS) from the ocean influences the chemical and optical properties of the atmosphere, and the olfactory landscape for foraging marine birds, turtles and mammals. DMS concentration has been seen to vary across seasons and latitudes with plankton taxonomy and activity, and following the seascape of ocean’s physics. However, whether and how does it vary at the time scales of meteorology and day-night cycles is largely unknown. Here we used high-resolution measurements over time and depth within coherent water patches in the open sea to show that DMS concentration responded rapidly but resiliently to mesoscale meteorological perturbation. Further, it varied over diel cycles in conjunction with rhythmic photobiological indicators in phytoplankton. Combining data and modelling, we show that sunlight switches and tunes the balance between net biological production and abiotic losses. This is an outstanding example of how biological diel rhythms affect biogeochemical processes. PMID:27578300

A high-resolution time-depth view of dimethylsulphide cycling in the surface sea

NASA Astrophysics Data System (ADS)

Royer, S.-J.; Galí, M.; Mahajan, A. S.; Ross, O. N.; Pérez, G. L.; Saltzman, E. S.; Simó, R.

2016-08-01

Emission of the trace gas dimethylsulphide (DMS) from the ocean influences the chemical and optical properties of the atmosphere, and the olfactory landscape for foraging marine birds, turtles and mammals. DMS concentration has been seen to vary across seasons and latitudes with plankton taxonomy and activity, and following the seascape of ocean’s physics. However, whether and how does it vary at the time scales of meteorology and day-night cycles is largely unknown. Here we used high-resolution measurements over time and depth within coherent water patches in the open sea to show that DMS concentration responded rapidly but resiliently to mesoscale meteorological perturbation. Further, it varied over diel cycles in conjunction with rhythmic photobiological indicators in phytoplankton. Combining data and modelling, we show that sunlight switches and tunes the balance between net biological production and abiotic losses. This is an outstanding example of how biological diel rhythms affect biogeochemical processes.

Open-cycle OTEC system performance analysis. [Claude cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewandowski, A.A.; Olson, D.A.; Johnson, D.H.

1980-10-01

An algorithm developed to calculate the performance of Claude-Cycle ocean thermal energy conversion (OTEC) systems is described. The algorithm treats each component of the system separately and then interfaces them to form a complete system, allowing a component to be changed without changing the rest of the algorithm. Two components that are subject to change are the evaporator and condenser. For this study we developed mathematical models of a channel-flow evaporator and both a horizontal jet and spray director contact condenser. The algorithm was then programmed to run on SERI's CDC 7600 computer and used to calculate the effect onmore » performance of deaerating the warm and cold water streams before entering the evaporator and condenser, respectively. This study indicates that there is no advantage to removing air from these streams compared with removing the air from the condenser.« less

Particulate sulfur-containing lipids: Production and cycling from the epipelagic to the abyssopelagic zone

NASA Astrophysics Data System (ADS)

Gašparović, Blaženka; Penezić, Abra; Frka, Sanja; Kazazić, Saša; Lampitt, Richard S.; Holguin, F. Omar; Sudasinghe, Nilusha; Schaub, Tanner

2018-04-01

There are major gaps in our understanding of the distribution and role of lipids in the open ocean especially with regard to sulfur-containing lipids (S-lipids). Here, we employ a powerful analytical approach based on high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to elucidate depth-related S-lipid production and molecular transformations in suspended particulate matter from the Northeast Atlantic Ocean in this depth range. We show that within the open-ocean environment S-lipids contribute up to 4.2% of the particulate organic carbon, and that up to 95% of these compounds have elemental compositions that do not match those found in the Nature Lipidomics Gateway database (termed "novel"). Among the remaining 5% of lipids that match the database, we find that sulphoquinovosyldiacylglycerol (SQDG) are efficiently removed while sinking through the mesopelagic zone. The relative abundance of other assigned lipids (sulphoquinovosylmonoacylglycerol (SQMG), sulfite and sulfate lipids, Vitamin D2 and D3 derivatives, and sphingolipids) did not change substantially with depth. The novel S-lipids, represented by hundreds of distinct elemental compositions (160-300 molecules at any one depth), contribute increasingly to the lipid and particulate organic matter pools with increased depth. Depth-related transformations cause (i) incomplete degradation/transformation of unsaturated S-lipids which leads to the depth-related accumulation of the refractory saturated compounds with reduced molecular weight (average 455 Da) and (ii) formation of highly unsaturated S-lipids (average abyssopelagic molecular double bond equivalents, DBE=7.8) with lower molecular weight (average 567 Da) than surface S-lipids (average 592 Da). A depth-related increase in molecular oxygen content is observed for all novel S-lipids and indicates that oxidation has a significant role in their transformation while (bio)hydrogenation possibly impacts the formation of saturated compounds. The instrumentation approach applied here represents a step change in our comprehension of marine S-lipid diversity and the potential role of these compounds in the oceanic carbon cycle. We describe a very much higher number of compounds than previously reported, albeit at the level of elemental composition and fold-change quantitation with depth, rather than isomeric confirmation and absolute quantitation of individual lipids. We emphasize that saturated S-lipids have the potential to transfer carbon from the upper ocean to depth and hence are significant vectors for carbon sequestration.

Seasonality in ocean microbial communities.

PubMed

Giovannoni, Stephen J; Vergin, Kevin L

2012-02-10

Ocean warming occurs every year in seasonal cycles that can help us to understand long-term responses of plankton to climate change. Rhythmic seasonal patterns of microbial community turnover are revealed when high-resolution measurements of microbial plankton diversity are applied to samples collected in lengthy time series. Seasonal cycles in microbial plankton are complex, but the expansion of fixed ocean stations monitoring long-term change and the development of automated instrumentation are providing the time-series data needed to understand how these cycles vary across broad geographical scales. By accumulating data and using predictive modeling, we gain insights into changes that will occur as the ocean surface continues to warm and as the extent and duration of ocean stratification increase. These developments will enable marine scientists to predict changes in geochemical cycles mediated by microbial communities and to gauge their broader impacts.

Mercury Biogeochemical Cycling in the Ocean and Policy Implications

PubMed Central

Mason, Robert P.; Choi, Anna L.; Fitzgerald, William F.; Hammerschmidt, Chad R.; Lamborg, Carl H.; Soerensen, Anne L.; Sunderland, Elsie M.

2012-01-01

Anthropogenic activities have enriched mercury in the biosphere by at least a factor of three, leading to increases in total mercury (Hg) in the surface ocean. However, the impacts on ocean fish and associated trends in human exposure as a result of such changes are less clear. Here we review our understanding of global mass budgets for both inorganic and methylated Hg species in ocean seawater. We consider external inputs from atmospheric deposition and rivers as well as internal production of monomethylmercury (CH3Hg) and dimethylmercury ((CH3)2Hg). Impacts of large-scale ocean circulation and vertical transport processes on Hg distribution throughout the water column and how this influences bioaccumulation into ocean food chains are also discussed. Our analysis suggests that while atmospheric deposition is the main source of inorganic Hg to open ocean systems, most of the CH3Hg accumulating in ocean fish is derived from in situ production within the upper waters (<1000 m). An analysis of the available data suggests that concentrations in the various ocean basins are changing at different rates due to differences in atmospheric loading and that the deeper waters of the oceans are responding slowly to changes in atmospheric Hg inputs. Most biological exposures occur in the upper ocean and therefore should respond over years to decades to changes in atmospheric mercury inputs achieved by regulatory control strategies. Migratory pelagic fish such as tuna and swordfish are an important component of CH3Hg exposure for many human populations and therefore any reduction in anthropogenic releases of Hg and associated deposition to the ocean will result in a decline in human exposure and risk. PMID:22559948

Mercury biogeochemical cycling in the ocean and policy implications.

PubMed

Mason, Robert P; Choi, Anna L; Fitzgerald, William F; Hammerschmidt, Chad R; Lamborg, Carl H; Soerensen, Anne L; Sunderland, Elsie M

2012-11-01

Anthropogenic activities have enriched mercury in the biosphere by at least a factor of three, leading to increases in total mercury (Hg) in the surface ocean. However, the impacts on ocean fish and associated trends in human exposure as a result of such changes are less clear. Here we review our understanding of global mass budgets for both inorganic and methylated Hg species in ocean seawater. We consider external inputs from atmospheric deposition and rivers as well as internal production of monomethylmercury (CH₃Hg) and dimethylmercury ((CH₃)₂Hg). Impacts of large-scale ocean circulation and vertical transport processes on Hg distribution throughout the water column and how this influences bioaccumulation into ocean food chains are also discussed. Our analysis suggests that while atmospheric deposition is the main source of inorganic Hg to open ocean systems, most of the CH₃Hg accumulating in ocean fish is derived from in situ production within the upper waters (<1000 m). An analysis of the available data suggests that concentrations in the various ocean basins are changing at different rates due to differences in atmospheric loading and that the deeper waters of the oceans are responding slowly to changes in atmospheric Hg inputs. Most biological exposures occur in the upper ocean and therefore should respond over years to decades to changes in atmospheric mercury inputs achieved by regulatory control strategies. Migratory pelagic fish such as tuna and swordfish are an important component of CH₃Hg exposure for many human populations and therefore any reduction in anthropogenic releases of Hg and associated deposition to the ocean will result in a decline in human exposure and risk. Copyright © 2012 Elsevier Inc. All rights reserved.

Surface Ocean-Lower Atmosphere Studies: SOLAS

NASA Astrophysics Data System (ADS)

Wanninkhof, R.; Dickerson, R.; Barber, R.; Capone, D. G.; Duce, R.; Erickson, D.; Keene, W. C.; Lenschow, D.; Matrai, P. A.; McGillis, W.; McGillicuddy, D.; Penner, J.; Pszenny, A.

2002-05-01

The US Surface Ocean - Lower Atmosphere Study (US SOLAS) is a component of an international program (SOLAS) with an overall goal: to achieve a quantitative understanding of the key biogeochemical-physical interactions between the ocean and atmosphere, and of how this coupled system affects and is affected by climateand environmental change. There is increasing evidence that the biogeochemical cycles containing the building blocks of life such as carbon, nitrogen, and sulfur have been perturbed. These changes result in appreciable impacts and feedbacks in the SOLA region. The exact nature of the impacts and feedbacks are poorly constrained because of sparse observations, in particular relating to the connectivity and interrelationships between the major biogeochemical cycles and their interaction with physical forcing. It is in these areas that the research and the interdisciplinary research approaches advocated in US SOLAS will provide high returns. The research in US SOLAS will be heavily focused on process studies of the natural variability of key processes, anthropogenic perturbation of the processes, and the positive and negative feedbacks the processes will have on the biogeochemical cycles in the SOLA region. A major objective is to integrate the process study findings with the results from large-scale observations and with small and large- scale modeling and remote sensing efforts to improve our mechanistic understanding of large scale biogeochemical and physical phenomena and feedbacks. US SOLAS held an open workshop in May 2001 to lay the groundwork for the SOLAS program in the United States. Resulting highlights and issues will be summarized around 4 major themes: (1) Boundary-layer Physics, (2) Dynamics of long-lived climate relevant compounds, (3) Dynamics of short-lived climate relevant compounds, and (4) Atmospheric effects on marine biogeochemical processes. Comprehensive reports from the working groups of U.S. SOLAS, and the international science plan which served as overall guidance, can be found at We will explore possible dedicated, interdisciplinary ocean-atmosphere projects as examples of the critical interconnectivity of atmospheric, interfacial, and upper ocean processes to study phenomena of critical importance in understanding the earth's system.

A Sedimentary Carbon Inventory for a Scottish Sea Loch

NASA Astrophysics Data System (ADS)

Smeaton, Craig; Austin, William; Davies, Althea; Baltzer, Agnes

2015-04-01

Coastal oceans are sites of biogeochemical cycling, as terrestrial, atmospheric, and marine carbon cycles interact. Important processes that affect the carbon cycle in the coastal ocean include upwelling, river input, air-sea gas exchange, primary production, respiration, sediment burial, export, and sea-ice dynamics. The magnitude and variability of many carbon fluxes are accordingly much higher in coastal oceans than in open ocean environments. Having high-quality observations of carbon stocks and fluxes in the coastal environment is important both for understanding coastal ocean carbon balance and for reconciling continent-scale carbon budgets. Despite the ecological, biological, and economic importance of coastal oceans, the magnitude and variability of many of the coastal carbon stocks are poorly quantified in most regions in comparison to terrestrial and deep ocean carbon stocks. The first stage in understanding the carbon dynamics in coastal waters is to quantify the existing carbon stocks. The coastal sediment potentially holds a significant volume of carbon; yet there has been no comprehensive attempt to quantitatively determine the volume of carbon held in those coastal sediments as echoed by Bauer et al., (2013) "the diverse sources and sinks of carbon and their complex interactions in these waters remain poorly understood". We set out to create the first sedimentary carbon inventory for a sea loch (fjord); through a combination of geophysics and biogeochemistry. Two key questions must be answered to achieve this goal; how much sediment is held within the loch and what percentage of that sediment carbon? The restrictive geomorphology of sea lochs (fjords) provides the perfect area to develop this methodology and answer these fundamental questions. Loch Sunart the longest of the Scottish sea lochs is our initial test site due to existing geophysical data being available for analysis. Here we discuss the development of the joint geophysics and biogeochemical methodology and how it was applied to Loch Sunart. The methodology was applied to seismic geophysics data collected in 2009 (Baltzer et al. 2010,) and data compiled through biogeochemical analysis of sediment cores collected from Loch Sunart. Through the combination of these datasets we have undertaken calculations to quantify the total sediment mass and the percentage of carbon contained in that sediment. Through this work we have created the first holistic sedimentary carbon inventory for a sea loch; which is the first step to tackling the larger questions around coastal carbon. Baltzer, A, Bates, R, Mokeddem, Z, Clet-Pellerin, M, Walter-Simonnet, A-V, Bonnot-Courtois, C and Austin, WEN 2010, Using seismic facies and pollen analyses to evaluate climatically driven change in a Scottish sea loch (fjord) over the last 20 ka, Geological Society, London, Special Publications, 344, (1), pp. 355-369. Bauer, JE, Cai, W-J, Raymond, P a, Bianchi, TS, Hopkinson, CS and Regnier, P a G 2013, The changing carbon cycle of the coastal ocean., Nature, 504, (7478), pp. 61-70.

Trends in ocean colour and chlorophyll concentration from 1889 to 2000, worldwide.

PubMed

Wernand, Marcel R; van der Woerd, Hendrik J; Gieskes, Winfried W C

2013-01-01

Marine primary productivity is an important agent in the global cycling of carbon dioxide, a major 'greenhouse gas', and variations in the concentration of the ocean's phytoplankton biomass can therefore explain trends in the global carbon budget. Since the launch of satellite-mounted sensors globe-wide monitoring of chlorophyll, a phytoplankton biomass proxy, became feasible. Just as satellites, the Forel-Ule (FU) scale record (a hardly explored database of ocean colour) has covered all seas and oceans--but already since 1889. We provide evidence that changes of ocean surface chlorophyll can be reconstructed with confidence from this record. The EcoLight radiative transfer numerical model indicates that the FU index is closely related to chlorophyll concentrations in open ocean regions. The most complete FU record is that of the North Atlantic in terms of coverage over space and in time; this dataset has been used to test the validity of colour changes that can be translated to chlorophyll. The FU and FU-derived chlorophyll data were analysed for monotonously increasing or decreasing trends with the non-parametric Mann-Kendall test, a method to establish the presence of a consistent trend. Our analysis has not revealed a globe-wide trend of increase or decrease in chlorophyll concentration during the past century; ocean regions have apparently responded differentially to changes in meteorological, hydrological and biological conditions at the surface, including potential long-term trends related to global warming. Since 1889, chlorophyll concentrations have decreased in the Indian Ocean and in the Pacific; increased in the Atlantic Ocean, the Mediterranean, the Chinese Sea, and in the seas west and north-west of Japan. This suggests that explanations of chlorophyll changes over long periods should focus on hydrographical and biological characteristics typical of single ocean regions, not on those of 'the' ocean.

Physical climatology of Indonesian maritime continent: An outline to comprehend observational studies

NASA Astrophysics Data System (ADS)

Yamanaka, Manabu D.

2016-09-01

The Indonesian maritime continent (IMC) is a miniature of our land-sea coexisting planet Earth. Firstly, without interior activity, the Earth becomes an even-surfaced "aqua-planet" with both atmosphere and ocean flowing almost zonally, and solar differential heating generates (global thermal tides and) Hadley's meridional circulations with the inter-tropical convergence zone (ITCZ) along the equator as observed actually over the open (Indian and Pacific) oceans on the both sides of the IMC. The ITCZ involves intraseasonal variations or super cloud clusters moving eastward with hierarchical substructures moving also westward. Secondly, the lands and seas over the actual Earth have been keeping the area ratio of 3:7 (similar to that of islands and inland/surrounding seas in the IMC), but their displacements have produced the IMC near the equator, which turns equatorial Pacific easterly ocean current northward (Kuroshio) and reflects equatorial oceanic waves that affect coupled ocean-atmosphere interannual variations such as ENSO and IOD, or displacements of Walker's zonal circulations. Thirdly, because the IMC consists of many large/small islands with very long coastlines, many narrow straits control the global (Pacific to Indian) ocean circulation, and the land-sea heat capacity contrasts along the coastlines generate the world's largest rainfall with diurnal cycles (sea-land breeze circulations). The diurnal cycles are dominant even in the rainy season (austral summer in Jawa and Bali), because rainfall-induced sprinkler-like land cooling reverses the trans-coastal temperature gradient before sunrise, and subsequent clear sky on land until around noon provides solar heating dependent on season. These processes lead to rapid land/hydrosphere-atmosphere water exchange, local air pollutant washout, and transequatorial boreal winter monsoon (cold surge). In El Niño years, for example, the cooler sea-surface temperature suppresses the morning coastal-sea rainfall, and induces often serious smog diffused from land over the IMC. Lastly, high-resolution observations/models covering both over islands and seas are necessary. A radar-profiler network (HARIMAU) has been constructed during FY2005-09, and capacity building on radar operations and buoy manufacturing has been promoted during FY2009-13 by Japan-Indonesia collaboration projects, which are taken over by an Indonesian national center (MCCOE) established in November 2013. Through these projects, variabilities of local circulations and precipitations with diurnal cycles have been recognized as important targets both in science and application.

Annual Cycle of Surface Longwave Radiation

NASA Technical Reports Server (NTRS)

Mlynczak, Pamela E.; Smith, G. Louis; Wilber, Anne C.; Stackhouse, Paul W.

2011-01-01

The annual cycles of upward and downward longwave fluxes at the Earth s surface are investigated by use of the NASA/GEWEX Surface Radiation Budget Data Set. Because of the immense difference between the heat capacity of land and ocean, the surface of Earth is partitioned into these two categories. Principal component analysis is used to quantify the annual cycles. Over land, the first principal component describes over 95% of the variance of the annual cycle of the upward and downward longwave fluxes. Over ocean the first term describes more than 87% of these annual cycles. Empirical orthogonal functions show the corresponding geographical distributions of these cycles. Phase plane diagrams of the annual cycles of upward longwave fluxes as a function of net shortwave flux show the thermal inertia of land and ocean.

In situ imaging reveals the biomass of giant protists in the global ocean.

PubMed

Biard, Tristan; Stemmann, Lars; Picheral, Marc; Mayot, Nicolas; Vandromme, Pieter; Hauss, Helena; Gorsky, Gabriel; Guidi, Lionel; Kiko, Rainer; Not, Fabrice

2016-04-28

Planktonic organisms play crucial roles in oceanic food webs and global biogeochemical cycles. Most of our knowledge about the ecological impact of large zooplankton stems from research on abundant and robust crustaceans, and in particular copepods. A number of the other organisms that comprise planktonic communities are fragile, and therefore hard to sample and quantify, meaning that their abundances and effects on oceanic ecosystems are poorly understood. Here, using data from a worldwide in situ imaging survey of plankton larger than 600 μm, we show that a substantial part of the biomass of this size fraction consists of giant protists belonging to the Rhizaria, a super-group of mostly fragile unicellular marine organisms that includes the taxa Phaeodaria and Radiolaria (for example, orders Collodaria and Acantharia). Globally, we estimate that rhizarians in the top 200 m of world oceans represent a standing stock of 0.089 Pg carbon, equivalent to 5.2% of the total oceanic biota carbon reservoir. In the vast oligotrophic intertropical open oceans, rhizarian biomass is estimated to be equivalent to that of all other mesozooplankton (plankton in the size range 0.2-20 mm). The photosymbiotic association of many rhizarians with microalgae may be an important factor in explaining their distribution. The previously overlooked importance of these giant protists across the widest ecosystem on the planet changes our understanding of marine planktonic ecosystems.

Open-ocean fish reveal an omnidirectional solution to camouflage in polarized environments.

PubMed

Brady, Parrish C; Gilerson, Alexander A; Kattawar, George W; Sullivan, James M; Twardowski, Michael S; Dierssen, Heidi M; Gao, Meng; Travis, Kort; Etheredge, Robert Ian; Tonizzo, Alberto; Ibrahim, Amir; Carrizo, Carlos; Gu, Yalong; Russell, Brandon J; Mislinski, Kathryn; Zhao, Shulei; Cummings, Molly E

2015-11-20

Despite appearing featureless to our eyes, the open ocean is a highly variable environment for polarization-sensitive viewers. Dynamic visual backgrounds coupled with predator encounters from all possible directions make this habitat one of the most challenging for camouflage. We tested open-ocean crypsis in nature by collecting more than 1500 videopolarimetry measurements from live fish from distinct habitats under a variety of viewing conditions. Open-ocean fish species exhibited camouflage that was superior to that of both nearshore fish and mirrorlike surfaces, with significantly higher crypsis at angles associated with predator detection and pursuit. Histological measurements revealed that specific arrangements of reflective guanine platelets in the fish's skin produce angle-dependent polarization modifications for polarocrypsis in the open ocean, suggesting a mechanism for natural selection to shape reflectance properties in this complex environment. Copyright © 2015, American Association for the Advancement of Science.

Ozone nighttime recovery in the marine boundary layer: Measurement and simulation of the ozone diurnal cycle at Reunion Island

NASA Astrophysics Data System (ADS)

Bremaud, P. J.; Taupin, F.; Thompson, A. M.; Chaumerliac, N.

1998-02-01

We describe the diurnal cycle of ozone in the marine boundary layer measured at Reunion Island (21°S, 55°E) in the western part of the Indian Ocean in August-September 1995. Results from a box chemistry model are compared with ozone measurements at Reunion Island. We focus on the peak-to-peak amplitude of ozone concentration, since our measurements show a variation of about 4 parts per billion by volume, which is close to the value obtained by Johnson et al. [1990] during the Soviet-American Gases and Aerosols (SAGA) 1987 Indian Ocean cruise. Different dynamical mechanisms are examined in order to reproduce such a variation. We conclude that the most important one is the exchange between the ozone-rich free troposphere and the ozone-poor boundary layer. This exchange is supposed to be more important during the night than during the day, allowing ozone nighttime recovery. This is the key point of the observed diurnal cycle, since daytime ozone photochemistry is well described by the model. Then we assume an entrainment velocity equal to 1 mm s-1 during the day and 14 mm s-1 during the night to closely match our measurements. Topography influences, together with clouds, are presumed to be responsible for this difference between nighttime and daytime entrainment velocities of free tropospheric air into the boundary layer at Reunion Island. Over the open ocean the difference of the turbulent flux of sensible heat between the day and the night explains the strong ozone nighttime recovery observed by us and by Johnson et al. [1990].

Phosphogenesis in the 2460 and 2728 million-year-old banded iron formations as evidence for biological cycling of phosphate in the early biosphere

PubMed Central

Li, Yi-Liang; Sun, Si; Chan, Lung S

2013-01-01

The banded iron formation deposited during the first 2 billion years of Earth's history holds the key to understanding the interplay between the geosphere and the early biosphere at large geological timescales. The earliest ore-scale phosphorite depositions formed almost at ∼2.0–2.2 billion years ago bear evidence for the earliest bloom of aerobic life. The cycling of nutrient phosphorus and how it constrained primary productivity in the anaerobic world of Archean–Palaeoproterozoic eons are still open questions. The controversy centers about whether the precipitation of ultrafine ferric oxyhydroxide due to the microbial Fe(II) oxidation in oceans earlier than 1.9 billion years substantially sequestrated phosphate, and whether this process significantly limited the primary productivity of the early biosphere. In this study, we report apatite radial flowers of a few micrometers in the 2728 million-year-old Abitibi banded iron formation and the 2460 million-year-old Kuruman banded iron formation and their similarities to those in the 535 million-year-old Lower Cambrian phosphorite. The lithology of the 535 Million-year-old phosphorite as a biosignature bears abundant biomarkers that reveal the possible similar biogeochemical cycling of phosphorus in the Later Archean and Palaeoproterozoic oceans. These apatite radial flowers represent the primary precipitation of phosphate derived from the phytoplankton blooms in the euphotic zones of Neoarchean and Palaoeproterozoic oceans. The unbiased distributions of the apatite radial flowers within sub-millimeter bands do not support the idea of an Archean Crisis of Phosphate. This is the first report of the microbial mediated mineralization of phosphorus before the Great Oxidation Event when the whole biosphere was still dominated by anaerobic microorganisms. PMID:23404127

Phosphogenesis in the 2460 and 2728 million-year-old banded iron formations as evidence for biological cycling of phosphate in the early biosphere.

PubMed

Li, Yi-Liang; Sun, Si; Chan, Lung S

2012-01-01

The banded iron formation deposited during the first 2 billion years of Earth's history holds the key to understanding the interplay between the geosphere and the early biosphere at large geological timescales. The earliest ore-scale phosphorite depositions formed almost at ∼2.0-2.2 billion years ago bear evidence for the earliest bloom of aerobic life. The cycling of nutrient phosphorus and how it constrained primary productivity in the anaerobic world of Archean-Palaeoproterozoic eons are still open questions. The controversy centers about whether the precipitation of ultrafine ferric oxyhydroxide due to the microbial Fe(II) oxidation in oceans earlier than 1.9 billion years substantially sequestrated phosphate, and whether this process significantly limited the primary productivity of the early biosphere. In this study, we report apatite radial flowers of a few micrometers in the 2728 million-year-old Abitibi banded iron formation and the 2460 million-year-old Kuruman banded iron formation and their similarities to those in the 535 million-year-old Lower Cambrian phosphorite. The lithology of the 535 Million-year-old phosphorite as a biosignature bears abundant biomarkers that reveal the possible similar biogeochemical cycling of phosphorus in the Later Archean and Palaeoproterozoic oceans. These apatite radial flowers represent the primary precipitation of phosphate derived from the phytoplankton blooms in the euphotic zones of Neoarchean and Palaoeproterozoic oceans. The unbiased distributions of the apatite radial flowers within sub-millimeter bands do not support the idea of an Archean Crisis of Phosphate. This is the first report of the microbial mediated mineralization of phosphorus before the Great Oxidation Event when the whole biosphere was still dominated by anaerobic microorganisms.

Air-sea exchange of gaseous mercury in the East China Sea.

PubMed

Wang, Chunjie; Ci, Zhijia; Wang, Zhangwei; Zhang, Xiaoshan

2016-05-01

Two oceanographic cruises were carried out in the East China Sea (ECS) during the summer and fall of 2013. The main objectives of this study are to identify the spatial-temporal distributions of gaseous elemental mercury (GEM) in air and dissolved gaseous mercury (DGM) in surface seawater, and then to estimate the Hg(0) flux. The GEM concentration was lower in summer (1.61 ± 0.32 ng m(-3)) than in fall (2.20 ± 0.58 ng m(-3)). The back-trajectory analysis revealed that the air masses with high GEM levels during fall largely originated from the land, while the air masses with low GEM levels during summer primarily originated from ocean. The spatial distribution patterns of total Hg (THg), fluorescence, and turbidity were consistent with the pattern of DGM with high levels in the nearshore area and low levels in the open sea. Additionally, the levels of percentage of DGM to THg (%DGM) were higher in the open sea than in the nearshore area, which was consistent with the previous studies. The THg concentration in fall was higher (1.47 ± 0.51 ng l(-1)) than those of other open oceans. The DGM concentration (60.1 ± 17.6 pg l(-1)) and Hg(0) flux (4.6 ± 3.6 ng m(-2) h(-1)) in summer were higher than those in fall (DGM: 49.6 ± 12.5 pg l(-1) and Hg(0) flux: 3.6 ± 2.8 ng m(-2) h(-1)). The emission flux of Hg(0) from the ECS was estimated to be 27.6 tons yr(-1), accounting for ∼0.98% of the global Hg oceanic evasion though the ECS only accounts for ∼0.21% of global ocean area, indicating that the ECS plays an important role in the oceanic Hg cycle. Copyright © 2016 Elsevier Ltd. All rights reserved.

Slab Ocean El Niño atmospheric feedbacks in Coupled Climate Models and its relationship to the Recharge Oscillator

NASA Astrophysics Data System (ADS)

Bayr, Tobias; Wengel, Christian; Latif, Mojib

2016-04-01

Dommenget (2010) found that El Niño-like variability, termed Slab Ocean El Niño, can exist in the absence of ocean dynamics and is driven by the interaction of the atmospheric surface heat fluxes and the heat content of the upper ocean. Further, Dommenget et al. (2014) report the Slab Ocean El Niño is not an artefact of the ECHAM5-AGCM coupled to a slab ocean model. In fact, atmospheric feedbacks crucial to the Slab Ocean El Niño can also be found in many state-of-the-art coupled climate models participating in CMIP3 and CMIP5, so that ENSO in many CMIP models can be understood as a mixed recharge oscillator/Slab Ocean El Niño mode. Here we show further analysis of the Slab Ocean El Niño atmospheric feedbacks in coupled models. The BCCR_CM2.0 climate model from the CMIP3 data base, which has a very large equatorial cold bias, has an El Niño that is mostly driven by Slab Ocean El Niño atmospheric feedbacks and is used as an example to describe Slab Ocean El Niño atmospheric feedbacks in a coupled model. In the BCCR_CM2.0, the ENSO-related variability in the 20°C isotherm (Z20), a measure of upper ocean heat content, is decoupled from the first mode of the seasonal cycle-related variability, while the two are coupled in observations, with ENSO being phase-locked to the seasonal cycle. Further analysis of the seasonal cycle in Z20 using SODA Ocean Reanalysis reveals two different regimes in the seasonal cycle along the equator: The first regime, to which ENSO is phase-locked, extends over the west and central equatorial Pacific and is driven by subsurface ocean dynamics. The second regime, extending in observations only over the cold tongue region, is driven by the seasonal cycle at the sea surface and is shifted by roughly six months relative to the first regime. In a series of experiments with the Kiel Climate Model (KCM) with different mean states due to tuning in the convection parameters, we can show that the strength of the equatorial cold bias and the coupling strength between the seasonal cycle of Z20 and ENSO are anti-correlated, i.e. a strong equatorial cold bias suppresses recharge oscillator dynamics and enhances Slab Ocean El Niño atmospheric feedbacks, supporting the results from the BCCR_CM2.0. This can be explained as with a stronger cold bias the second regime of the seasonal cycle in Z20, which extends in observations only over the small cold tongue region, expands westward and becomes more important, so that it decouples ENSO from the seasonal cycle in Z20. This has implications for some major characteristics of the ENSO like the propagation of SST anomalies, the phase locking of SST to the seasonal cycle, or the nonlinearity of ENSO. Dommenget, D., 2010: The slab ocean El Niño. Geophys. Res. Lett., 37, L20701, doi:10.1029/2010GL044888. - - , S. Haase, T. Bayr, and C. Frauen, 2014: Analysis of the Slab Ocean El Niño atmospheric feedbacks in observed and simulated ENSO dynamics. Clim. Dyn., doi:10.1007/s00382-014-2057-0.

FixO3: Advancement towards Open Ocean Observatory Data Management Harmonisation

NASA Astrophysics Data System (ADS)

Behnken, Andree; Pagnani, Maureen; Huber, Robert; Lampitt, Richard

2015-04-01

Since 2002 there has been a sustained effort, supported as European framework projects, to harmonise both the technology and the data management of Open Ocean fixed observatories run by European nations. FixO3 started in September 2013, and for 3 more years will coordinate the convergence of data management best practice across a constellation of moorings in the Atlantic, in both hemispheres, and in the Mediterranean. To ensure the continued existence of these unique sources of oceanographic data as sustained observatories it is vital to improve access to the data collected, both in terms of methods of presentation, real-time availability, long-term archiving and quality assurance. The data management component of FixO3 improves access to marine observatory data by harmonising data management standards, formats and workflows covering the complete life cycle of data from real time data acquisition to long-term archiving. Legal and data policy aspects have been examined and discussed to identify transnational barriers to open-access to marine observatory data. As a result, a harmonised FixO3 data policy was drafted, which provides a formal basis for data exchange between FixO3 infrastructures, and also enables open access to data for the general public. FixO3 interacts with other European infrastructures such as EMODnet, SeaDataNet, PANGAEA, and especially aims to harmonise efforts with OceanSites and MyOcean. The project landing page (www.fixo3.eu) offers detailed information about every observatory as well as data visualisations and direct downloads. In addition to this, metadata for all FixO3 - relevant data are available from the searchable FixO3 metadata catalogue, which is also accessible from the project web page. This catalogue is hosted by PANGAEA and receives updates in regular intervals. The FixO3 Standards & Services registry ties in with the GEOSS Components and Services Registry (CSR) and provides additional observatory information. The data management efforts are central to FixO3. As a result of the procedural and technological harmonisation efforts undertaken in the project, the FixO3 network of observatories is accumulating unique, quality controlled data sets that will develop into a legacy repository of openly accessible oceanographic data.

Future ocean hypercapnia driven by anthropogenic amplification of the natural CO2 cycle

NASA Astrophysics Data System (ADS)

McNeil, B.

2016-02-01

Elevated carbon dioxide concentrations in seawater (hypercapnia) can induce neurological, physiological and behavioural deficiencies in marine animals. Prediction of the onset and evolution of hypercapnia in the ocean requires a good understanding of annual oceanic carbon dioxide variability, but relevant global observational data are sparse. Here we diagnose global ocean patterns of monthly carbon variability based on observations that allow us to examine the evolution of surface ocean CO2 levels over the entire annual cycle under increasing atmospheric CO2 concentrations. We find that some oceanic regions undergo an up to 10-fold amplification of the natural cycle of CO2 by 2100, if atmospheric carbon dioxide concentrations continue to rise throughout this century (RCP8.5). Projections from a suite of Earth System Climate Models are broadly consistent with the findings from our data based approach. Our predicted amplification in the annual CO2 cycle displays distinct global patterns that may expose major fisheries in the Southern, Pacific and North Atlantic Oceans to high CO2 events many decades earlier than expected from average atmospheric CO2 concentrations. We suggest that these ocean 'CO2 hotspots' evolve as a combination of the strong seasonal dynamics of CO2 and the long-term effective storage of anthropogenic CO2 that lowers the buffer capacity in those regions, causing a non-linear CO2 amplification over the annual cycle. The onset of ocean hypercapnia events (pCO2 >1000 µatm) is forecast for atmospheric CO2 concentrations that exceed 650 ppm, with hypercapnia spreading to up to one half of the surface ocean by the year 2100 under a high-emissions scenario (RCP8.5) with potential implications for fisheries over the coming century.

Seasonality of coastal zone scanner phytoplankton pigment in the offshore oceans

NASA Technical Reports Server (NTRS)

Banse, K.; English, D. C.

1994-01-01

The NASA Global Ocean Data Set of plant pigment concentrations in the upper euphotic zone is evaluated for diserning geographical and temporal patterns of seasonality in the open sea. Monthly medians of pigment concentrations for all available years are generated for fields of approximately 77,000 sq km. For the climatological year, highest and lowest medians, month of occurence of the highest median, ratio of highest to lowest medians, and absolute range between the highest and lowest medians are mapped ocean-wide between 62.5 deg N and 62.5 deg S. Seasonal cycles are depicted for 48 sites. In much of the offshore ocean, seasonality of pigment is inferred to be driven almost equally by the interaction of the abiotic environment with phytoplankton physiology and the loss of cells from grazing. Special emphasis among natural domains or provinces is given to the Subantarctic water ring, with no seasonality in its low chlorophyll concentrations in spite of strong environmental forcing, and the narrow Transition Zones, a few degrees of latitude on the equatorial sides of the Subtropical Convergences of the southern hemisphere and their homologs in the northern hemisphere, which have late winter blooms caused by nutrient injection into the upper layers.

A 3D parameterization of nutrients atmospheric deposition to the global ocean

NASA Astrophysics Data System (ADS)

Myriokefalitakis, S.; Nenes, A.; Baker, A. R.; Mihalopoulos, N.; Kanakidou, M.

2016-12-01

Atmospheric deposition of trace constituents, both of natural and anthropogenic origin, can act as a nutrient source into the open ocean and affect marine ecosystem functioning and subsequently the exchange of CO2 between the atmosphere and the global ocean. Dust is known as a major source of nutrients (such as iron and phosphorus) to the global ocean, but only a fraction of these nutrients is released in soluble form that can be assimilated by the ecosystems. The global atmospheric iron (Fe) and phosphorus (P) cycles are here parameterized in a global 3-D chemical transport model. Both primary emissions of total and soluble Fe and P associated with dust and combustion processes are taken into account. The impact of atmospheric acidity on nutrient solubility is parameterised based on experimental findings and model results are evaluated by comparison with available observations. The effect of air-quality changes on soluble nutrient deposition is studied by performing sensitivity simulations using preindustrial, present and future emission scenarios. The link between the soluble Fe and P atmospheric deposition and anthropogenic sources is also investigated. Overall, the response of the chemical composition of nutrient-containing aerosols to environmental changes is demonstrated and quantified.

Effects of the diurnal cycle in solar radiation on the tropical Indian Ocean mixed layer variability during wintertime Madden-Julian Oscillations

NASA Astrophysics Data System (ADS)

Li, Yuanlong; Han, Weiqing; Shinoda, Toshiaki; Wang, Chunzai; Lien, Ren-Chieh; Moum, James N.; Wang, Jih-Wang

2013-10-01

The effects of solar radiation diurnal cycle on intraseasonal mixed layer variability in the tropical Indian Ocean during boreal wintertime Madden-Julian Oscillation (MJO) events are examined using the HYbrid Coordinate Ocean Model. Two parallel experiments, the main run and the experimental run, are performed for the period of 2005-2011 with daily atmospheric forcing except that an idealized hourly shortwave radiation diurnal cycle is included in the main run. The results show that the diurnal cycle of solar radiation generally warms the Indian Ocean sea surface temperature (SST) north of 10°S, particularly during the calm phase of the MJO when sea surface wind is weak, mixed layer is thin, and the SST diurnal cycle amplitude (dSST) is large. The diurnal cycle enhances the MJO-forced intraseasonal SST variability by about 20% in key regions like the Seychelles-Chagos Thermocline Ridge (SCTR; 55°-70°E, 12°-4°S) and the central equatorial Indian Ocean (CEIO; 65°-95°E, 3°S-3°N) primarily through nonlinear rectification. The model also well reproduced the upper-ocean variations monitored by the CINDY/DYNAMO field campaign between September-November 2011. During this period, dSST reaches 0.7°C in the CEIO region, and intraseasonal SST variability is significantly amplified. In the SCTR region where mean easterly winds are strong during this period, diurnal SST variation and its impact on intraseasonal ocean variability are much weaker. In both regions, the diurnal cycle also has a large impact on the upward surface turbulent heat flux QT and induces diurnal variation of QT with a peak-to-peak difference of O(10 W m-2).

A 3D parameterization of iron atmospheric deposition to the global ocean

NASA Astrophysics Data System (ADS)

Myriokefalitakis, Stelios; Krol, Maarten C.; van Noije, Twan P. C.; Le Sager, Philippe

2017-04-01

Atmospheric deposition of trace constituents, both of natural and anthropogenic origin, can act as a nutrient source into the open ocean and affect marine ecosystem functioning and subsequently the exchange of CO2 between the atmosphere and the global ocean. Dust is known as a major source of nutrients to the global ocean, but only a fraction of these nutrients is released in soluble form that can be assimilated by the ecosystems. Iron (Fe) is a key micronutrient that significantly modulates gross primary production in High-Nutrient-Low-Chlorophyll (HNLC) oceans, where macronutrients like nitrate are abundant but primary production is limited by Fe scarcity. The global atmospheric Fe cycle is here parameterized in the state-of-the-art global Earth System Model EC-Earth. The model takes into account the primary emissions of both insoluble and soluble Fe, associated with dusts and combustion processes. The impact of atmospheric acidity on mineral solubility is parameterized based on updated experimental and theoretical findings, and model results are evaluated against available observations. The link between the soluble Fe atmospheric deposition and anthropogenic sources is also investigated. Overall, the response of the chemical composition of nutrient containing aerosols to atmospheric composition changes is demonstrated and quantified. This work has been financed by the Marie-Curie H2020-MSCA-IF-2015 grant (ID 705652) ODEON (Online DEposition over OceaNs: Modeling the effect of air pollution on ocean bio-geochemistry in an Earth System Model).

Operational experience of the OC-OTEC experiments at NELH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Link, H

1989-02-01

The Solar Energy Research Institute, under funding and program direction from the US Department of Energy, has been operating a small-scale test apparatus to investigate key components of open- cycle ocean thermal energy conversion (OC-OTEC). The apparatus started operations in October 1987 and continues to provide valuable information on heat-and mass-transfer processes in evaporators and condensers, gas sorption processes as seawater is depressurized and repressurized, and control and instrumentation characteristics of open-cycle systems. Although other test facilities have been used to study some of these interactions, this is the largest apparatus of its kind to use seawater since Georges Claude`smore » efforts in 1926. The information obtained from experiments conducted in this apparatus is being used to design a larger scale experiment in which a positive net power production is expected to be demonstrated for the first time with OC-OTEC. This paper describes the apparatus, the major tests conducted during its first 18 months of operation, and the experience gained in OC-OTEC system operation. 13 refs., 8 figs.« less

The Jormungand Global Climate State and Implications for the Neoproterozoic Snowball Paradox (Invited)

NASA Astrophysics Data System (ADS)

Abbot, D. S.; Voigt, A.; Koll, D.; Pierrehumbert, R. T.

2010-12-01

We present a previously undescribed global climate state, the Jormungand state, that is nearly ice-covered with a narrow (~10-15 degrees of latitude) strip of open ocean near the equator. This state is sustained by internal dynamics of the hydrological cycle and the cryosphere. There is a new bifurcation in global climate climate associated with the Jormungand state that leads to significant hysteresis. We investigate the Jormungand state in a coupled ocean-atmosphere GCM, in multiple atmospheric GCMs coupled to a mixed layer ocean run in an idealized configuration, and we make a simple modification to the Budyko-Sellers model so that it produces Jormungand states. We suggest that the Jormungand state may be a better model for the Neoproterozoic glaciations (~635 Ma and ~715 Ma) than either the hard Snowball or the Slushball models. A Jormungand state would have a large enough region of open ocean near the equator to explain the micropaleontological and molecular clock evidence that photosynthetic eukaryotes thrived both before and immediately after the Neoproterozoic episodes. Additionally, since there is significant hysteresis associated with the Jormungand state, it can explain the cap carbonate sequences, the oxygen isotopic evidence that suggests high CO2 values, and the various evidence that suggests lifetimes for the glaciations of 1 Myrs or more. Since there is not significant hysteresis associated with the Slushball model, the Slushball model cannot explain these observations. Finally, we note that although the Slushball and Jormungand models share the characteristic of open ocean in the tropics, the Jormungand state is produced by entirely different physics, is entered through a new bifurcation in global climate, and is associated with significant hysteresis. Bifurcation diagram of global climate in the CAM global climate model, run with no continents, a 50 m mixed layer with no ocean heat transport, an eccentricity of zero, and annually and diurnally-varying insolation with a solar constant of 94% of present value. Red diamonds denote simulations initiated from ice-free conditions, blue circles denote simulations initiated from the Jormungand state, and green squares denote simulations initiated from the Snowball state. The black curve shows model equilibria, with dotted unstable solution branches (separatrices) and bifurcations drawn schematically.

Plastic debris in the open ocean

PubMed Central

Cózar, Andrés; Echevarría, Fidel; González-Gordillo, J. Ignacio; Irigoien, Xabier; Úbeda, Bárbara; Hernández-León, Santiago; Palma, Álvaro T.; Navarro, Sandra; García-de-Lomas, Juan; Ruiz, Andrea; Fernández-de-Puelles, María L.; Duarte, Carlos M.

2014-01-01

There is a rising concern regarding the accumulation of floating plastic debris in the open ocean. However, the magnitude and the fate of this pollution are still open questions. Using data from the Malaspina 2010 circumnavigation, regional surveys, and previously published reports, we show a worldwide distribution of plastic on the surface of the open ocean, mostly accumulating in the convergence zones of each of the five subtropical gyres with comparable density. However, the global load of plastic on the open ocean surface was estimated to be on the order of tens of thousands of tons, far less than expected. Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered. Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean. PMID:24982135

Plastic debris in the open ocean.

PubMed

Cózar, Andrés; Echevarría, Fidel; González-Gordillo, J Ignacio; Irigoien, Xabier; Ubeda, Bárbara; Hernández-León, Santiago; Palma, Alvaro T; Navarro, Sandra; García-de-Lomas, Juan; Ruiz, Andrea; Fernández-de-Puelles, María L; Duarte, Carlos M

2014-07-15

There is a rising concern regarding the accumulation of floating plastic debris in the open ocean. However, the magnitude and the fate of this pollution are still open questions. Using data from the Malaspina 2010 circumnavigation, regional surveys, and previously published reports, we show a worldwide distribution of plastic on the surface of the open ocean, mostly accumulating in the convergence zones of each of the five subtropical gyres with comparable density. However, the global load of plastic on the open ocean surface was estimated to be on the order of tens of thousands of tons, far less than expected. Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered. Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean.

Detecting Global Hydrological Cycle Intensification in Sea Surface Salinity

NASA Astrophysics Data System (ADS)

Poague, J.; Stine, A.

2016-12-01

Global warming is expected to intensify the global hydrological cycle, but significant regional differences exist in the predicted response. The proposed zonal mean thermodynamic response is enhanced horizontal moisture transport associated with increased saturation vapor pressure, which in turn drives additional net precipitation in the tropics and at high latitudes and additional net evaporation in the subtropics. Sea surface salinity (SSS) anomalies are forced from above by changes in evaporation minus precipitation (E-P) and thus will respond to changes in the global hydrological cycle, opening the possibility of using historical SSS anomalies to diagnose the response of the hydrological cycle to warming. We estimate zonal mean SSS trends in the Atlantic and Pacific ocean basins from 1955-2015 to test whether historical changes in the global hydrological cycle are consistent with a primarily thermodynamic response. Motivated by this observation, we calculate the sensitivity of basin zonal-mean SSS anomalies to sea surface temperature (SST) forcing as a function of timescale to diagnose and estimate the signal-to-noise ratio of the purely thermodynamic signal as a function of timescale. High-frequency variability in SSS anomalies is likely to be influenced by variability in atmospheric circulation, complicating the attribution of the link between basin zonal-mean SSS anomalies and global SST anomalies. We therefore estimate the basin zonal mean SSS anomaly response to the major modes of large-scale dynamic variability. We find a strong correlation between detrended zonal-mean SSS anomalies and the Pacific-North American index (R=0.71,P<0.01) in the Pacific Ocean. We interpret the relationship between zonal mean SSS anomalies and temperature in terms of the relative contribution of thermodynamic and dynamic processes.

Non-Rayleigh control of upper-ocean Cd isotope fractionation in the western South Atlantic

NASA Astrophysics Data System (ADS)

Xie, Ruifang C.; Galer, Stephen J. G.; Abouchami, Wafa; Rijkenberg, Micha J. A.; de Baar, Hein J. W.; De Jong, Jeroen; Andreae, Meinrat O.

2017-08-01

We present seawater Cd isotopic compositions in five depth profiles and a continuous surface water transect, from 50°S to the Equator, in the western South Atlantic, sampled during GEOTRACES cruise 74JC057 (GA02 section, Leg 3), and investigate the mechanisms governing Cd isotope cycling in the upper and deep ocean. The depth profiles generally display high ε 112 / 110Cd at the surface and decrease with increasing depth toward values typical of Antarctic Bottom Water (AABW). However, at stations north of the Subantarctic Front, the decrease in ε 112 / 110Cd is interrupted by a shift to values intermediate between those of surface and bottom waters, which occurs at depths occupied by North Atlantic Deep Water (NADW). This pattern is associated with variations in Cd concentration from low surface values to a maximum at mid-depths and is attributed to preferential utilization of light Cd by phytoplankton in the surface ocean. Our new results show that in this region Cd-deficient waters do not display the extreme, highly fractionated ε 112 / 110Cd reported in some earlier studies from other oceanic regions. Instead, in the surface and subsurface southwest (SW) Atlantic, when [Cd] drops below 0.1 nmol kg-1, ε 112 / 110Cd are relatively homogeneous and cluster around a value of +3.7, in agreement with the mean value of 3.8 ± 3.3 (2SD, n = 164) obtained from a statistical evaluation of the global ocean Cd isotope dataset. We suggest that Cd-deficient surface waters may acquire their Cd isotope signature via sorption of Cd onto organic ligands, colloids or bacterial/picoplankton extracellular functional groups. Alternatively, we show that an open system, steady-state model is in good accord with the observed Cd isotope systematics in the upper ocean north of the Southern Ocean. The distribution of ε 112 / 110Cd in intermediate and deep waters is consistent with the water mass distribution, with the north-south variations reflecting changes in the mixing proportion of NADW and either AABW or AAIW depending on the depth. Overall, the SW Atlantic Cd isotope dataset demonstrates that the large-scale ocean circulation exerts the primary control on ε 112 / 110Cd cycling in the global deep ocean.

Barrier island breach evolution: Alongshore transport and bay-ocean pressure gradient interactions

USGS Publications Warehouse

Safak, Ilgar; Warner, John C.; List, Jeffrey

2016-01-01

Physical processes controlling repeated openings and closures of a barrier island breach between a bay and the open ocean are studied using aerial photographs and atmospheric and hydrodynamic observations. The breach site is located on Pea Island along the Outer Banks, separating Pamlico Sound from the Atlantic Ocean. Wind direction was a major control on the pressure gradients between the bay and the ocean to drive flows that initiate or maintain the breach opening. Alongshore sediment flux was found to be a major contributor to breach closure. During the analysis period from 2011 to 2016, three hurricanes had major impacts on the breach. First, Hurricane Irene opened the breach with wind-driven flow from bay to ocean in August 2011. Hurricane Sandy in October 2012 quadrupled the channel width from pressure gradient flows due to water levels that were first higher on the ocean side and then higher on the bay side. The breach closed sometime in Spring 2013, most likely due to an event associated with strong alongshore sediment flux but minimal ocean-bay pressure gradients. Then, in July 2014, Hurricane Arthur briefly opened the breach again from the bay side, in a similar fashion to Irene. In summary, opening and closure of breaches are shown to follow a dynamic and episodic balance between along-channel pressure gradient driven flows and alongshore sediment fluxes.

The origin of neap-spring tidal cycles

USGS Publications Warehouse

Kvale, E.P.

2006-01-01

The origin of oceanic tides is a basic concept taught in most introductory college-level sedimentology/geology, oceanography, and astronomy courses. Tides are typically explained in the context of the equilibrium tidal theory model. Yet this model does not take into account real tides in many parts of the world. Not only does the equilibrium tidal model fail to explicate amphidromic circulation, it also does not explain diurnal tides in low latitude positions. It likewise fails to explain the existence of tide-dominated areas where neap-spring cycles are synchronized with the 27.32-day orbital cycle of the Moon (tropical month), rather than with the more familiar 29.52-day cycle of lunar phases (synodic month). Both types of neap-spring cycles can be recognized in the rock record. A complete explanation of the origin of tides should include a discussion of dynamic tidal theory. In the dynamic tidal model, tides resulting from the motions of the Moon in its orbit around the Earth and the Earth in its orbit around the Sun are modeled as products of the combined effects of a series of phantom satellites. The movement of each of these satellites, relative to the Earth's equator, creates its own tidal wave that moves around an amphidromic point. Each of these waves is referred to as a tidal constituent. The geometries of the ocean basins determine which of these constituents are amplified. Thus, the tide-raising potential for any locality on Earth can be conceptualized as the result of a series of tidal constituents specific to that region. A better understanding of tidal cycles opens up remarkable opportunities for research on tidal deposits with implications for, among other things, a more complete understanding of the tidal dynamics responsible for sediment transport and deposition, changes in Earth-Moon distance through time, and the possible influences tidal cycles may exert on organisms. ?? 2006 Elsevier B.V. All rights reserved.

A multidisciplinary glider survey of an open ocean dead-zone eddy

NASA Astrophysics Data System (ADS)

Karstensen, Johannes; Schütte, Florian; Pietri, Alice; Krahmann, Gerd; Fiedler, Björn; Löscher, Carolin; Grundle, Damian; Hauss, Helena; Körtzinger, Arne; Testor, Pierre; Viera, Nuno

2016-04-01

The physical (temperature, salinity) and biogeochemical (oxygen, nitrate, chlorophyll fluorescence, turbidity) structure of an anticyclonic modewater eddy, hosting an open ocean dead zone, is investigated using observational data sampled in high temporal and spatial resolution with autonomous gliders in March and April 2014. The core of the eddy is identified in the glider data as a volume of fresher (on isopycnals) water in the depth range from the mixed layer base (about 70m) to about 200m depth. The width is about 80km. The core aligns well with the 40 μmolkg-1 oxygen contour. From two surveys about 1 month apart, changes in the minimal oxygen concentrations (below 5μmolkg-1) are observed that indicate that small scale processes are in operation. Several scales of coherent variability of physical and biogeochemical variable are identified - from a few meters to the mesoscale. One of the gliders carried an autonomous Nitrate (N) sensor and the data is used to analyse the possible nitrogen pathways within the eddy. Also the highest N is accompanied by lowest oxygen concentrations, the AOU:N ratio reveals a preferred oxygen cycling per N.

Marine turtles use geomagnetic cues during open-sea homing.

PubMed

Luschi, Paolo; Benhamou, Simon; Girard, Charlotte; Ciccione, Stephane; Roos, David; Sudre, Joël; Benvenuti, Silvano

2007-01-23

Marine turtles are renowned long-distance navigators, able to reach remote targets in the oceanic environment; yet the sensory cues and navigational mechanisms they employ remain unclear [1, 3]. Recent arena experiments indicated an involvement of magnetic cues in juvenile turtles' homing ability after simulated displacements [4, 5], but the actual role of geomagnetic information in guiding turtles navigating in their natural environment has remained beyond the reach of experimental investigations. In the present experiment, twenty satellite-tracked green turtles (Chelonia mydas) were transported to four open-sea release sites 100-120 km from their nesting beach on Mayotte island in the Mozambique Channel; 13 of them had magnets attached to their head either during the outward journey or during the homing trip. All but one turtle safely returned to Mayotte to complete their egg-laying cycle, albeit with indirect routes, and showed a general inability to take into account the deflecting action of ocean currents as estimated through remote-sensing oceanographic measurements [7]. Magnetically treated turtles displayed a significant lengthening of their homing paths with respect to controls, either when treated during transportation or when treated during homing. These findings represent the first field evidence for the involvement of geomagnetic cues in sea-turtle navigation.

Longitudinal Biases in the Seychelles Dome Simulated by 34 Ocean-Atmosphere Coupled General Circulation Models

NASA Astrophysics Data System (ADS)

Nagura, M.; Sasaki, W.; Tozuka, T.; Luo, J.; Behera, S. K.; Yamagata, T.

2012-12-01

The upwelling dome of the southern tropical Indian Ocean is examined by using simulated results from 34 ocean-atmosphere coupled general circulation models (CGCMs) including those from the phase five of the Coupled Model Intercomparison Project (CMIP5). Among the current set of the 34 CGCMs, 12 models erroneously produce the upwelling dome in the eastern half of the basin while the observed Seychelles Dome is located in the southwestern tropical Indian Ocean (Figure 1). The annual mean Ekman pumping velocity is almost zero in the southern off-equatorial region in these models. This is in contrast with the observations that show Ekman upwelling as the cause of the Seychelles Dome. In the models that produce the dome in the eastern basin, the easterly biases are prominent along the equator in boreal summer and fall that cause shallow thermocline biases along the Java and Sumatra coasts via Kelvin wave dynamics and result in a spurious upwelling dome there. In addition, these models tend to overestimate (underestimate) the magnitude of annual (semiannual) cycle of thermocline depth variability in the dome region, which is another consequence of the easterly wind biases in boreal summer-fall. Compared to the CMIP3 models (Yokoi et al. 2009), the CMIP5 models are even worse in simulating the dome longitudes and magnitudes of annual and semiannual cycles of thermocline depth variability in the dome region. Considering the increasing need to understand regional impacts of climate modes, these results may give serious caveats to interpretation of model results and help in further model developments.; Figure 1: The longitudes of the shallowest annual-mean D20 in 5°S-12°S. The open and filled circles are for the observations and the CGCMs, respectively.

The ocean mixed layer under Southern Ocean sea-ice: Seasonal cycle and forcing

NASA Astrophysics Data System (ADS)

Pellichero, Violaine; Sallée, Jean-Baptiste; Schmidtko, Sunke; Roquet, Fabien; Charrassin, Jean-Benoît

2017-02-01

The oceanic mixed layer is the gateway for the exchanges between the atmosphere and the ocean; in this layer, all hydrographic ocean properties are set for months to millennia. A vast area of the Southern Ocean is seasonally capped by sea-ice, which alters the characteristics of the ocean mixed layer. The interaction between the ocean mixed layer and sea-ice plays a key role for water mass transformation, the carbon cycle, sea-ice dynamics, and ultimately for the climate as a whole. However, the structure and characteristics of the under-ice mixed layer are poorly understood due to the sparseness of in situ observations and measurements. In this study, we combine distinct sources of observations to overcome this lack in our understanding of the polar regions. Working with elephant seal-derived, ship-based, and Argo float observations, we describe the seasonal cycle of the ocean mixed-layer characteristics and stability of the ocean mixed layer over the Southern Ocean and specifically under sea-ice. Mixed-layer heat and freshwater budgets are used to investigate the main forcing mechanisms of the mixed-layer seasonal cycle. The seasonal variability of sea surface salinity and temperature are primarily driven by surface processes, dominated by sea-ice freshwater flux for the salt budget and by air-sea flux for the heat budget. Ekman advection, vertical diffusivity, and vertical entrainment play only secondary roles. Our results suggest that changes in regional sea-ice distribution and annual duration, as currently observed, widely affect the buoyancy budget of the underlying mixed layer, and impact large-scale water mass formation and transformation with far reaching consequences for ocean ventilation.

The Great Chilean Tsunamis of 2010, 2014 and 2015 on the Coast and Offshore of Mexico: Comparative Features Based on Open-Ocean Energy Parameterization

NASA Astrophysics Data System (ADS)

Rabinovich, A.; Zaytsev, O.; Thomson, R.

2016-12-01

The three recent great earthquakes offshore of Chile on 27 February 2010 (Maule, Mw 8.8), 1 April 2014 (Iquique, Mw 8.2) and 16 September 2015 (Illapel, Mw 8.3) generated major trans-oceanic tsunamis that spread throughout the entire Pacific Ocean and were measured by numerous coastal tide gauges and open-ocean DART stations. Statistical and spectral analyses of the tsunami waves from the three events recorded on the Pacific coast of Mexico enabled us to compare the events and to identify coastal "hot spots", regions with maximum tsunami risk. Based on joint spectral analyses of tsunamis and background noise, we have developed a method for reconstructing the "true" tsunami spectra in the deep ocean. The "reconstructed" open-ocean tsunami spectra are in excellent agreement with the actual tsunami spectra evaluated from direct analysis of the DART records offshore of Mexico. We have further used the spectral estimates to parameterize the energy of the three Chilean tsunamis based on the total open-ocean tsunami energy and frequency content of the individual events.

Assessing the role of solar radiation in heating, photosynthesis, and photo-oxidation in upper Arctic Ocean waters via autonomous buoys

NASA Astrophysics Data System (ADS)

Hill, V. J.; Steele, M.; Light, B.

2016-02-01

As part of the Arctic Observing Network, a new ice-tethered buoy has been developed for monitoring the role of sunlight in regulating ocean temperature, phytoplankton growth, and carbon cycling. A 20 or 50 m string (depending on local bathymetry) supports sensors both within and below the ice for the hourly measurement of downwelling irradiance, temperature, Chlorophyll a, light backscattering, and dissolved organic material (DOM). Two buoys were deployed in March 2014 and two in March 2015. Because the buoys are engineered to survive melting out of first year ice, they have successfully provided complete seasonal records of water column warming, phytoplankton abundance and photo-oxidation patterns in the Pacific Arctic Region. The data collected will be used to determine whether reduced ice extent and thinner ice are driving increases in under ice warming, accelerating bottom ice ablation, increasing available photosynthetic radiation to support large under ice blooms, and to quantify photo-oxidation of the DOM pool. Observations so far have revealed strong under ice daily warming as high as ±0.5 °C driven by local solar radiation. Water column absorption was dominated by colored dissolved organic material which served to trap solar radiation in the upper water column. Chlorophyll concentrations observed in June and July indicated high phytoplankton abundance beneath the ice. Light intensity at this time was not sufficient to support growth rates high enough to produce the 8 to 10 mg m-3 of chlorophyll observed. We hypothesize that phytoplankton were advected under the ice from the ice edge. However, once there phytoplankton were able to sustain low growth rates leading to nutrient limitation before open water status was reached. Strong daily cycles of photo-oxidation have also been observed in the late summer that indicate the fast cycling of highly labile DOM in the open waters of the Pacific Arctic Region.

Variations of the Organic Matter Composition in the Sea Surface Microlayer: A Comparison between Open Ocean, Coastal, and Upwelling Sites Off the Peruvian Coast

PubMed Central

Zäncker, Birthe; Bracher, Astrid; Röttgers, Rüdiger; Engel, Anja

2017-01-01

The sea surface microlayer (SML) is the thin boundary layer between the ocean and the atmosphere, making it important for air-sea exchange processes. However, little is known about what controls organic matter composition in the SML. In particular, there are only few studies available on the differences of the SML of various oceanic systems. Here, we compared the organic matter and neuston species composition in the SML and the underlying water (ULW) at 11 stations with varying distance from the coast in the Peruvian upwelling regime, a system with high emissions of climate relevant trace gases, such as N2O and CO2. In the open ocean, organic carbon, and amino acids were highly enriched in the SML compared to the ULW. The enrichment decreased at the coastal stations and vanished in the upwelling regime. At the same time, the degradation of organic matter increased from the open ocean to the upwelling stations. This suggests that in the open ocean, upward transport processes or new production of organic matter within the SML are faster than degradation processes. Phytoplankton was generally not enriched in the SML, one group though, the Trichodesmium-like TrL (possibly containing Trichodesmium), were enriched in the open ocean but not in the upwelling region indicating that they find a favorable habitat in the open ocean SML. Our data show that the SML is a distinct habitat; its composition is more similar among different systems than between SML and ULW of a single station. Generally the enrichment of organic matter is assumed to be reduced when encountering low primary production and high wind speeds. However, our study shows the highest enrichments of organic matter in the open ocean which had the lowest primary production and the highest wind speeds. PMID:29375483

Variations of the Organic Matter Composition in the Sea Surface Microlayer: A Comparison between Open Ocean, Coastal, and Upwelling Sites Off the Peruvian Coast.

PubMed

Zäncker, Birthe; Bracher, Astrid; Röttgers, Rüdiger; Engel, Anja

2017-01-01

The sea surface microlayer (SML) is the thin boundary layer between the ocean and the atmosphere, making it important for air-sea exchange processes. However, little is known about what controls organic matter composition in the SML. In particular, there are only few studies available on the differences of the SML of various oceanic systems. Here, we compared the organic matter and neuston species composition in the SML and the underlying water (ULW) at 11 stations with varying distance from the coast in the Peruvian upwelling regime, a system with high emissions of climate relevant trace gases, such as N 2 O and CO 2 . In the open ocean, organic carbon, and amino acids were highly enriched in the SML compared to the ULW. The enrichment decreased at the coastal stations and vanished in the upwelling regime. At the same time, the degradation of organic matter increased from the open ocean to the upwelling stations. This suggests that in the open ocean, upward transport processes or new production of organic matter within the SML are faster than degradation processes. Phytoplankton was generally not enriched in the SML, one group though, the Trichodesmium -like TrL (possibly containing Trichodesmium ), were enriched in the open ocean but not in the upwelling region indicating that they find a favorable habitat in the open ocean SML. Our data show that the SML is a distinct habitat; its composition is more similar among different systems than between SML and ULW of a single station. Generally the enrichment of organic matter is assumed to be reduced when encountering low primary production and high wind speeds. However, our study shows the highest enrichments of organic matter in the open ocean which had the lowest primary production and the highest wind speeds.

Sea Surface Salinity and Wind Retrieval Algorithm Using Combined Passive-Active L-Band Microwave Data

NASA Technical Reports Server (NTRS)

Yueh, Simon H.; Chaubell, Mario J.

2011-01-01

Aquarius is a combined passive/active L-band microwave instrument developed to map the salinity field at the surface of the ocean from space. The data will support studies of the coupling between ocean circulation, the global water cycle, and climate. The primary science objective of this mission is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean with a spatial resolution of 150 kilometers and a retrieval accuracy of 0.2 practical salinity units globally on a monthly basis. The measurement principle is based on the response of the L-band (1.413 gigahertz) sea surface brightness temperatures (T (sub B)) to sea surface salinity. To achieve the required 0.2 practical salinity units accuracy, the impact of sea surface roughness (e.g. wind-generated ripples and waves) along with several factors on the observed brightness temperature has to be corrected to better than a few tenths of a degree Kelvin. To the end, Aquarius includes a scatterometer to help correct for this surface roughness effect.

Non-migratory breeding by isolated green sea turtles (Chelonia mydas) in the Indian Ocean: biological and conservation implications.

PubMed

Whiting, Scott D; Murray, Wendy; Macrae, Ismail; Thorn, Robert; Chongkin, Mohammad; Koch, Andrea U

2008-04-01

Green sea turtles (Chelonia mydas) are renowned for their long-distance migrations but have less fame for short-distance migrations or non-migratory behavior. We present satellite telemetric evidence from Cocos (Keeling) Islands, Indian Ocean for the first predominantly non-migratory green sea turtle (C. mydas) population. The mean migration distance from the nesting beach to the foraging grounds was 35.5 km with a maximum mean transit time of 3.4 days. The behavior of this population has major implications for our general understanding of green turtle behavior and their life cycle and for conservation. Firstly, these results indicate a level of juvenile or adult non-breeding homing behavior from the open ocean to foraging grounds adjacent to their natal nesting beach. Secondly, a non-migratory breeding phase reduces the consumption of reproductive energy utilized, potentially resulting in higher fecundity for this population. Thirdly, the close proximity of the nesting and foraging habitats allows for uniformity in management and conservation strategies rarely possible for wide-ranging green turtle populations.

Non-migratory breeding by isolated green sea turtles ( Chelonia mydas) in the Indian Ocean: biological and conservation implications

NASA Astrophysics Data System (ADS)

Whiting, Scott D.; Murray, Wendy; Macrae, Ismail; Thorn, Robert; Chongkin, Mohammad; Koch, Andrea U.

2008-04-01

Green sea turtles ( Chelonia mydas) are renowned for their long-distance migrations but have less fame for short-distance migrations or non-migratory behavior. We present satellite telemetric evidence from Cocos (Keeling) Islands, Indian Ocean for the first predominantly non-migratory green sea turtle ( C. mydas) population. The mean migration distance from the nesting beach to the foraging grounds was 35.5 km with a maximum mean transit time of 3.4 days. The behavior of this population has major implications for our general understanding of green turtle behavior and their life cycle and for conservation. Firstly, these results indicate a level of juvenile or adult non-breeding homing behavior from the open ocean to foraging grounds adjacent to their natal nesting beach. Secondly, a non-migratory breeding phase reduces the consumption of reproductive energy utilized, potentially resulting in higher fecundity for this population. Thirdly, the close proximity of the nesting and foraging habitats allows for uniformity in management and conservation strategies rarely possible for wide-ranging green turtle populations.

Possible Sea Ice Impacts on Oceanic Deep Convection

NASA Technical Reports Server (NTRS)

Parkinson, C. L.

1984-01-01

Many regions of the world ocean known or suspected to have deep convection are sea-ice covered for at least a portion of the annual cycle. As this suggests that sea ice might have some impact on generating or maintaining this phenomenon, several mechanisms by which sea ice could exert an influence are presented in the following paragraphs. Sea ice formation could be a direct causal factor in deep convection by providing the surface density increase necessary to initiate the convective overturning. As sea ice forms, either by ice accretion or by in situ ice formation in open water or in lead areas between ice floes, salt is rejected to the underlying water. This increases the water salinity, thereby increasing water density in the mixed layer under the ice. A sufficient increase in density will lead to mixing with deeper waters, and perhaps to deep convection or even bottom water formation. Observations are needed to establish whether this process is actually occurring; it is most likely in regions with extensive ice formation and a relatively unstable oceanic density structure.

Rewiring Host Lipid Metabolism by Large Viruses Determines the Fate of Emiliania huxleyi, a Bloom-Forming Alga in the Ocean[C][W][OPEN

PubMed Central

Rosenwasser, Shilo; Mausz, Michaela A.; Schatz, Daniella; Sheyn, Uri; Malitsky, Sergey; Aharoni, Asaph; Weinstock, Eyal; Tzfadia, Oren; Ben-Dor, Shifra; Feldmesser, Ester; Pohnert, Georg; Vardi, Assaf

2014-01-01

Marine viruses are major ecological and evolutionary drivers of microbial food webs regulating the fate of carbon in the ocean. We combined transcriptomic and metabolomic analyses to explore the cellular pathways mediating the interaction between the bloom-forming coccolithophore Emiliania huxleyi and its specific coccolithoviruses (E. huxleyi virus [EhV]). We show that EhV induces profound transcriptome remodeling targeted toward fatty acid synthesis to support viral assembly. A metabolic shift toward production of viral-derived sphingolipids was detected during infection and coincided with downregulation of host de novo sphingolipid genes and induction of the viral-encoded homologous pathway. The depletion of host-specific sterols during lytic infection and their detection in purified virions revealed their novel role in viral life cycle. We identify an essential function of the mevalonate-isoprenoid branch of sterol biosynthesis during infection and propose its downregulation as an antiviral mechanism. We demonstrate how viral replication depends on the hijacking of host lipid metabolism during the chemical “arms race” in the ocean. PMID:24920329

Carbon Dioxide Cycling And The Climate of Ancient Earth

NASA Technical Reports Server (NTRS)

Zahnle, Kevin; Sleep, Norman H.; DeVincenzi, Donald (Technical Monitor)

2001-01-01

The continental cycle of silicate weathering and metamorphism dynamically buffers atmospheric CO2 and climate. Feedback is provided by the strong temperature dependence of silicate weathering. Here we argue that hydrothermal alteration of oceanic basalts also dynamically buffers CO2. The oceanic cycle links with the mantle via subduction and the midocean ridges. Feedback is provided by the dependence of carbonatization on dissolved carbonates in seawater. Unlike the continental cycle, the oceanic cycle has no thermostat. Currently the continental cycle is more important, but earlier in Earth's history, especially if heat flow were higher than it is now, more vigorous plate tectonics would have made the oceanic cycle dominant. We find that CO2 greenhouses thick enough to defeat the faint early sun are implausible and that, if no other greenhouse gases are invoked, very cold climates are expected for much of the Proterozoic and the Archean. We echo current fashion and favor biogenic methane as the chief supplement to CO2. Fast weathering and probable subduction of abundant impact ejecta would have reduced CO2 levels still further in the Hadean. Despite its name, the Hadean would have been the coldest era in the history of the Earth.

Carbon Dioxide Cycling and the Climate of Ancient Earth

NASA Technical Reports Server (NTRS)

Zahnle, Kevin; Sleep, Norman H.

2001-01-01

The continental cycle of silicate weathering and metamorphism dynamically buffers atmospheric CO2 and climate. Feedback is provided by the strong temperature dependence of silicate weathering. Here we argue that hydrothermal alteration of oceanic basalts also dynamically buffers CO2. The oceanic cycle links with the mantle via subduction and the midocean ridges. Feedback is provided by the dependence of carbonatization on dissolved carbonates in seawater. Unlike the continental cycle, the oceanic cycle has no thermostat. Currently the continental cycle is more important, but earlier in Earth's history, especially if heat flow were higher than it is now, more vigorous plate tectonics would have made the oceanic cycle dominant. We find that CO2 greenhouses thick enough to defeat the faint early Sun are implausible and that, if no other greenhouse gases are invoked, very cold climates are expected for much of the Proterozoic and the Archean. We echo current fashion and favor biogenic methane as the chief supplement to CO2. Fast weathering and probable subduction of abundant impact ejecta would have reduced CO2 levels still further in the Hadean. Despite its name, the Hadean would have been the coldest era in the history of the Earth.

The Atlantic Meridional Overturning Circulation and Abrupt Climate Change.

PubMed

Lynch-Stieglitz, Jean

2017-01-03

Abrupt changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for circulation changes over the shortest events leaves open the possibility of other driving mechanisms for millennial-scale climate variability.

A compendium of geochemical information from the Saanich Inlet water column

NASA Astrophysics Data System (ADS)

Torres-Beltrán, Mónica; Hawley, Alyse K.; Capelle, David; Zaikova, Elena; Walsh, David A.; Mueller, Andreas; Scofield, Melanie; Payne, Chris; Pakhomova, Larysa; Kheirandish, Sam; Finke, Jan; Bhatia, Maya; Shevchuk, Olena; Gies, Esther A.; Fairley, Diane; Michiels, Céline; Suttle, Curtis A.; Whitney, Frank; Crowe, Sean A.; Tortell, Philippe D.; Hallam, Steven J.

2017-10-01

Extensive and expanding oxygen minimum zones (OMZs) exist at variable depths in coastal and open ocean waters. As oxygen levels decline, nutrients and energy are increasingly diverted away from higher trophic levels into microbial community metabolism, resulting in fixed nitrogen loss and production of climate active trace gases including nitrous oxide and methane. While ocean deoxygenation has been reported on a global scale, our understanding of OMZ biology and geochemistry is limited by a lack of time-resolved data sets. Here, we present a historical dataset of oxygen concentrations spanning fifty years and nine years of monthly geochemical time series observations in Saanich Inlet, a seasonally anoxic fjord on the coast of Vancouver Island, British Columbia, Canada that undergoes recurring changes in water column oxygenation status. This compendium provides a unique geochemical framework for evaluating long-term trends in biogeochemical cycling in OMZ waters.

Investigating the impact of diurnal cycle of SST on the intraseasonal and climate variability

NASA Astrophysics Data System (ADS)

Tseng, W. L.; Hsu, H. H.; Chang, C. W. J.; Keenlyside, N. S.; Lan, Y. Y.; Tsuang, B. J.; Tu, C. Y.

2016-12-01

The diurnal cycle is a prominent feature of our climate system and the most familiar example of externally forced variability. Despite this it remains poorly simulated in state-of-the-art climate models. A particular problem is the diurnal cycle in sea surface temperature (SST), which is a key variable in air-sea heat flux exchange. In most models the diurnal cycle in SST is not well resolved, due to insufficient vertical resolution in the upper ocean mixed-layer and insufficiently frequent ocean-atmosphere coupling. Here, we coupled a 1-dimensional ocean model (SIT) to two atmospheric general circulation model (ECHAM5 and CAM5). In particular, we focus on improving the representations of the diurnal cycle in SST in a climate model, and investigate the role of the diurnal cycle in climate and intraseasonal variability.

Decoupling of Iron and Phosphate in the Global Ocean

NASA Technical Reports Server (NTRS)

Parekh, Payal

2003-01-01

Iron is an essential micronutrient for marine phytoplankton, limiting their growth in high nutrient, low chlorophyll regions of the ocean. I use a hierarchy of ocean circulation and biogeochemistry models to understand controls on global iron distribution. I formulate a mechanistic model of iron cycling which includes scavenging onto sinking particles and complexation with an organic ligand. The iron cycle is coupled to a phosphorus cycling model. Iron's aeolian source is prescribed. In the context of a highly idealized multi-box model scheme, the model can be brought into consistency with the relatively sparse ocean observations of iron in the oceans. This biogeochemical scheme is also implemented in a coarse resolution ocean general circulation model. This model also successfully reproduces the broad regional patterns of iron and phosphorus. In particular, the high macronutrient concentrations of the Southern Ocean result from iron limitation in the model. Due to the potential ability of iron to change the efficiency of the carbon pump in the remote Southern Ocean, I study Southern Ocean surface phosphate response to increased aeolian dust flux. My box model and GCM results suggest that a global ten fold increase in dust flux can support a phosphate drawdown of 0.25-0.5 micromolar.

Multi-property modeling of ocean basin carbon fluxes

NASA Technical Reports Server (NTRS)

Volk, Tyler

1988-01-01

The objectives of this project were to elucidate the causal mechanisms in some of the most important features of the global ocean/atomsphere carbon system. These included the interaction of physical and biological processes in the seasonal cycle of surface water pCo2, and links between productivity, surface chlorophyll, and the carbon cycle that would aid global modeling efforts. In addition, several other areas of critical scientific interest involving links between the marine biosphere and the global carbon cycle were successfully pursued; specifically, a possible relation between phytoplankton emitted DMS and climate, and a relation between the location of calcium carbonate burial in the ocean and metamorphic source fluxes of CO2 to the atmosphere. Six published papers covering the following topics are summarized: (1) Mass extinctions, atmospheric sulphur and climatic warming at the K/T boundary; (2) Sensitivity of climate and atmospheric CO2 to deep-ocean and shallow-ocean carbonate burial; (3) Controls on CO2 sources and sinks in the earthscale surface ocean; (4) pre-anthropogenic, earthscale patterns of delta pCO2 between ocean and atmosphere; (5) Effect on atmospheric CO2 from seasonal variations in the high latitude ocean; and (6) Limitations or relating ocean surface chlorophyll to productivity.

Comparative genomics reveals surprising divergence of two closely related strains of uncultivated UCYN-A cyanobacteria.

PubMed

Bombar, Deniz; Heller, Philip; Sanchez-Baracaldo, Patricia; Carter, Brandon J; Zehr, Jonathan P

2014-12-01

Marine planktonic cyanobacteria capable of fixing molecular nitrogen (termed 'diazotrophs') are key in biogeochemical cycling, and the nitrogen fixed is one of the major external sources of nitrogen to the open ocean. Candidatus Atelocyanobacterium thalassa (UCYN-A) is a diazotrophic cyanobacterium known for its widespread geographic distribution in tropical and subtropical oligotrophic oceans, unusually reduced genome and symbiosis with a single-celled prymnesiophyte alga. Recently a novel strain of this organism was also detected in coastal waters sampled from the Scripps Institute of Oceanography pier. We analyzed the metagenome of this UCYN-A2 population by concentrating cells by flow cytometry. Phylogenomic analysis provided strong bootstrap support for the monophyly of UCYN-A (here called UCYN-A1) and UCYN-A2 within the marine Crocosphaera sp. and Cyanothece sp. clade. UCYN-A2 shares 1159 of the 1200 UCYN-A1 protein-coding genes (96.6%) with high synteny, yet the average amino-acid sequence identity between these orthologs is only 86%. UCYN-A2 lacks the same major pathways and proteins that are absent in UCYN-A1, suggesting that both strains can be grouped at the same functional and ecological level. Our results suggest that UCYN-A1 and UCYN-A2 had a common ancestor and diverged after genome reduction. These two variants may reflect adaptation of the host to different niches, which could be coastal and open ocean habitats.

Towards the impact of eddies on the response of the global ocean circulation to Southern Ocean gateway opening

NASA Astrophysics Data System (ADS)

Viebahn, Jan; von der Heydt, Anna S.; Dijkstra, Henk A.

2014-05-01

During the past 65 Million (Ma) years, Earth's climate has undergone a major change from warm 'greenhouse' to colder 'icehouse' conditions with extensive ice sheets in the polar regions of both hemispheres. The Eocene-Oligocene (~34 Ma) and Oligocene-Miocene (~23 Ma) boundaries reflect major transitions in Cenozoic global climate change. Proposed mechanisms of these transitions include reorganization of ocean circulation due to critical gateway opening/deepening, changes in atmospheric CO2-concentration, and feedback mechanisms related to land-ice formation. A long-standing hypothesis is that the formation of the Antarctic Circumpolar Current due to opening/deepening of Southern Ocean gateways led to glaciation of the Antarctic continent. However, while this hypothesis remains controversial, its assessment via coupled climate model simulations depends crucially on the spatial resolution in the ocean component. More precisely, only high-resolution modeling of the turbulent ocean circulation is capable of adequately describing reorganizations in the ocean flow field and related changes in turbulent heat transport. In this study, for the first time results of a high-resolution (0.1° horizontally) realistic global ocean model simulation with a closed Drake Passage are presented. Changes in global ocean temperatures, heat transport, and ocean circulation (e.g., Meridional Overturning Circulation and Antarctic Coastal Current) are established by comparison with an open Drake Passage high-resolution reference simulation. Finally, corresponding low-resolution simulations are also analyzed. The results highlight the essential impact of the ocean eddy field in palaeoclimatic change.

Infragravity waves in the deep ocean: An upward revision

NASA Astrophysics Data System (ADS)

Aucan, J.; Ardhuin, F.

2013-07-01

Ocean infragravity waves are surface gravity waves with periods of several minutes and corresponding wavelengths of up to tens of kilometers. When propagating freely in the deep ocean, these waves are typically small, several centimeters at most, so they have been seldom studied. In the context of future wide-swath altimetry missions, these waves need to be better quantified as they have wavelengths that will be resolved by such instruments. Here, we analyze the global climatology and variability of infragravity waves in the deep ocean using data from over 40 open ocean locations, with depths larger than 2000 m. We show that typical infragravity wave heights are higher than previously estimated, with winter-averaged values up to 11 mm off the U.S. West Coast, and typically less than 6 mm in the tropics. The mid to high latitudes exhibit a strong seasonal cycle consistent with the local variability of the wind-waves, while the tropical Pacific has a higher energy level during the Austral winter that does not correlate well with the local wind-waves, suggesting a remote source for the recorded infragravity waves. These infragravity wave energies are expected to be a significant contribution to the error budget for possible measurements of sea level associated to sub-mesoscale currents at horizontal scales around 10 km. Hence, a global numerical model of infragravity waves will likely be necessary for the analysis of the planned Surface Water Ocean Topography mission.

Post-Palaeozoic evolution of weathered landsurfaces in Uganda by tectonically controlled deep weathering and stripping

NASA Astrophysics Data System (ADS)

Taylor, R. G.; Howard, K. W. F.

1998-11-01

A model for the evolution of weathered landsurfaces in Uganda is developed using available geotectonic, climatic, sedimentological and chronological data. The model demonstrates the pivotal role of tectonic uplift in inducing cycles of stripping, and tectonic quiescence for cycles of deep weathering. It is able to account for the development of key landforms, such as inselbergs and duricrust-capped plateaux, which previous hypotheses of landscape evolution that are based on climatic or eustatic controls are unable to explain. Development of the Ugandan landscape is traced back to the Permian. Following late Palaeozoic glaciation, a trend towards warmer and more humid climates through the Mesozoic enabled deep weathering of the Jurassic/mid-Cretaceous surface in Uganda during a period of prolonged tectonic quiescence. Uplift associated with the opening South Atlantic Ocean terminated this cycle and instigated a cycle of stripping between the mid-Cretaceous and early Miocene. Deep weathering on the succeeding Miocene to recent (African) surface has occurred from Miocene to present but has been interrupted in the areas adjacent to the western rift where development of a new drainage base level has prompted cycles of stripping in the Miocene and Pleistocene.

Eighty-five million years of Pacific Ocean gyre ecosystem structure: long-term stability marked by punctuated change.

PubMed

Sibert, Elizabeth; Norris, Richard; Cuevas, Jose; Graves, Lana

2016-05-25

While the history of taxonomic diversification in open ocean lineages of ray-finned fish and elasmobranchs is increasingly known, the evolution of their roles within the open ocean ecosystem remains poorly understood. To assess the relative importance of these groups through time, we measured the accumulation rate of microfossil fish teeth and elasmobranch dermal denticles (ichthyoliths) in deep-sea sediment cores from the North and South Pacific gyres over the past 85 million years (Myr). We find three distinct and stable open ocean ecosystem structures, each defined by the relative and absolute abundance of elasmobranch and ray-finned fish remains. The Cretaceous Ocean (pre-66 Ma) was characterized by abundant elasmobranch denticles, but low abundances of fish teeth. The Palaeogene Ocean (66-20 Ma), initiated by the Cretaceous/Palaeogene mass extinction, had nearly four times the abundance of fish teeth compared with elasmobranch denticles. This Palaeogene Ocean structure remained stable during the Eocene greenhouse (50 Ma) and the Eocene-Oligocene glaciation (34 Ma), despite large changes in the overall accumulation of both groups during those intervals, suggesting that climate change is not a primary driver of ecosystem structure. Dermal denticles virtually disappeared from open ocean ichthyolith assemblages approximately 20 Ma, while fish tooth accumulation increased dramatically in variability, marking the beginning of the Modern Ocean. Together, these results suggest that open ocean fish community structure is stable on long timescales, independent of total production and climate change. The timing of the abrupt transitions between these states suggests that the transitions may be due to interactions with other, non-preserved pelagic consumer groups. © 2016 The Author(s).

Eighty-five million years of Pacific Ocean gyre ecosystem structure: long-term stability marked by punctuated change

PubMed Central

Norris, Richard; Cuevas, Jose; Graves, Lana

2016-01-01

While the history of taxonomic diversification in open ocean lineages of ray-finned fish and elasmobranchs is increasingly known, the evolution of their roles within the open ocean ecosystem remains poorly understood. To assess the relative importance of these groups through time, we measured the accumulation rate of microfossil fish teeth and elasmobranch dermal denticles (ichthyoliths) in deep-sea sediment cores from the North and South Pacific gyres over the past 85 million years (Myr). We find three distinct and stable open ocean ecosystem structures, each defined by the relative and absolute abundance of elasmobranch and ray-finned fish remains. The Cretaceous Ocean (pre-66 Ma) was characterized by abundant elasmobranch denticles, but low abundances of fish teeth. The Palaeogene Ocean (66–20 Ma), initiated by the Cretaceous/Palaeogene mass extinction, had nearly four times the abundance of fish teeth compared with elasmobranch denticles. This Palaeogene Ocean structure remained stable during the Eocene greenhouse (50 Ma) and the Eocene–Oligocene glaciation (34 Ma), despite large changes in the overall accumulation of both groups during those intervals, suggesting that climate change is not a primary driver of ecosystem structure. Dermal denticles virtually disappeared from open ocean ichthyolith assemblages approximately 20 Ma, while fish tooth accumulation increased dramatically in variability, marking the beginning of the Modern Ocean. Together, these results suggest that open ocean fish community structure is stable on long timescales, independent of total production and climate change. The timing of the abrupt transitions between these states suggests that the transitions may be due to interactions with other, non-preserved pelagic consumer groups. PMID:27194702

Is There a Tectonically Driven Supertidal Cycle?

NASA Astrophysics Data System (ADS)

Green, J. A. M.; Molloy, J. L.; Davies, H. S.; Duarte, J. C.

2018-04-01

Earth is 180 Myr into the current supercontinent cycle, and the next supercontinent is predicted to form in 250 Myr. The continuous changes in continental configuration can move the ocean between resonant states, and the semidiurnal tides are currently large compared to the past 252 Myr due to tidal resonance in the Atlantic. This leads to the hypothesis that there is a "supertidal" cycle linked to the supercontinent cycle. Here this is tested using new tectonic predictions for the next 250 Myr as bathymetry in a numerical tidal model. The simulations support the following hypothesis: a new tidal resonance will appear 150 Myr from now, followed by a decreasing tide as the supercontinent forms 100 Myr later. This affects the dissipation of tidal energy in the oceans, with consequences for the evolution of the Earth-Moon system, ocean circulation and climate, and implications for the ocean's capacity of hosting and evolving life.

Nitrogen and Oxygen Isotopic Studies of the Marine Nitrogen Cycle

NASA Astrophysics Data System (ADS)

Casciotti, Karen L.

2016-01-01

The marine nitrogen cycle is a complex web of microbially mediated reactions that control the inventory, distribution, and speciation of nitrogen in the marine environment. Because nitrogen is a major nutrient that is required by all life, its availability can control biological productivity and ecosystem structure in both surface and deep-ocean communities. Stable isotopes of nitrogen and oxygen in nitrate and nitrite have provided new insights into the rates and distributions of marine nitrogen cycle processes, especially when analyzed in combination with numerical simulations of ocean circulation and biogeochemistry. This review highlights the insights gained from dual-isotope studies applied at regional to global scales and their incorporation into oceanic biogeochemical models. These studies represent significant new advances in the use of isotopic measurements to understand the modern nitrogen cycle, with implications for the study of past ocean productivity, oxygenation, and nutrient status.

Software framework for prognostic health monitoring of ocean-based power generation

NASA Astrophysics Data System (ADS)

Bowren, Mark

On August 5, 2010 the U.S. Department of Energy (DOE) has designated the Center for Ocean Energy Technology (COET) at Florida Atlantic University (FAU) as a national center for ocean energy research and development of prototypes for open-ocean power generation. Maintenance on ocean-based machinery can be very costly. To avoid unnecessary maintenance it is necessary to monitor the condition of each machine in order to predict problems. This kind of prognostic health monitoring (PHM) requires a condition-based maintenance (CBM) system that supports diagnostic and prognostic analysis of large amounts of data. Research in this field led to the creation of ISO13374 and the development of a standard open-architecture for machine condition monitoring. This thesis explores an implementation of such a system for ocean-based machinery using this framework and current open-standard technologies.

Dynamic Topography and Sea Level Anomalies of the Southern Ocean: Variability and Teleconnections

NASA Astrophysics Data System (ADS)

Armitage, Thomas W. K.; Kwok, Ron; Thompson, Andrew F.; Cunningham, Glenn

2018-01-01

This study combines sea surface height (SSH) estimates of the ice-covered Southern Ocean with conventional open-ocean SSH estimates from CryoSat-2 to produce monthly composites of dynamic ocean topography (DOT) and sea level anomaly (SLA) on a 50 km grid spanning 2011-2016. This data set reveals the full Southern Ocean SSH seasonal cycle for the first time; there is an antiphase relationship between sea level on the Antarctic continental shelf and the deeper basins, with coastal SSH highest in autumn and lowest in spring. As a result of this pattern of seasonal SSH variability, the barotropic component of the Antarctic Slope Current (ASC) has speeds that are regionally up to twice as fast in the autumn. Month-to-month circulation variability of the Ross and Weddell Gyres is strongly influenced by the local wind field, and is correlated with the local wind curl (Ross: -0.58; Weddell: -0.67). SSH variability is linked to both the Southern Oscillation and the Southern Annular Mode, dominant modes of southern hemisphere climate variability. In particular, during the strong 2015-2016 El Niño, a sustained negative coastal SLA of up to -6 cm, implying a weakening of the ASC, was observed in the Pacific sector of the Southern Ocean. The ability to examine sea level variability in the seasonally ice-covered regions of the Southern Ocean—climatically important regions with an acute sparsity of data—makes this new merged sea level record of particular interest to the Southern Ocean oceanography and glaciology communities.

On the seasonal variability of the Canary Current and the Atlantic Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

Vélez-Belchí, Pedro; Pérez-Hernández, M. Dolores; Casanova-Masjoan, María.; Cana, Luis; Hernández-Guerra, Alonso

2017-06-01

The Atlantic Meridional Overturning Circulation (AMOC) is continually monitored along 26°N by the RAPID-MOCHA array. Measurements from this array show a 6.7 Sv seasonal cycle for the AMOC, with a 5.9 Sv contribution from the upper mid-ocean. Recent studies argue that the dynamics of the eastern Atlantic is the main driver for this seasonal cycle; specifically, Rossby waves excited south of the Canary Islands. Using inverse modeling, hydrographic, mooring, and altimetry data, we describe the seasonal cycle of the ocean mass transport around the Canary Islands and at the eastern boundary, under the influence of the African slope, where eastern component of the RAPID-MOCHA array is situated. We find a seasonal cycle of -4.1 ± 0.5 Sv for the oceanic region of the Canary Current, and +3.7 ± 0.4 Sv at the eastern boundary. This seasonal cycle along the eastern boundary is in agreement with the seasonal cycle of the AMOC that requires the lowest contribution to the transport in the upper mid-ocean to occur in fall. However, we demonstrate that the linear Rossby wave model used previously to explain the seasonal cycle of the AMOC is not robust, since it is extremely sensitive to the choice of the zonal range of the wind stress curl and produces the same results with a Rossby wave speed of zero. We demonstrate that the seasonal cycle of the eastern boundary is due to the recirculation of the Canary Current and to the seasonal cycle of the poleward flow that characterizes the eastern boundaries of the oceans.

Estimating the Cross-Shelf Export of Riverine Materials: Part 2. Estimates of Global Freshwater and Nutrient Export

NASA Astrophysics Data System (ADS)

Izett, Jonathan G.; Fennel, Katja

2018-02-01

Rivers deliver large amounts of fresh water, nutrients, and other terrestrially derived materials to the coastal ocean. Where inputs accumulate on the shelf, harmful effects such as hypoxia and eutrophication can result. In contrast, where export to the open ocean is efficient riverine inputs contribute to global biogeochemical budgets. Assessing the fate of riverine inputs is difficult on a global scale. Global ocean models are generally too coarse to resolve the relatively small scale features of river plumes. High-resolution regional models have been developed for individual river plume systems, but it is impractical to apply this approach globally to all rivers. Recently, generalized parameterizations have been proposed to estimate the export of riverine fresh water to the open ocean (Izett & Fennel, 2018, https://doi.org/10.1002/2017GB005667; Sharples et al., 2017, https://doi.org/10.1002/2016GB005483). Here the relationships of Izett and Fennel, https://doi.org/10.1002/2017GB005667 are used to derive global estimates of open-ocean export of fresh water and dissolved inorganic silicate, dissolved organic carbon, and dissolved organic and inorganic phosphorus and nitrogen. We estimate that only 15-53% of riverine fresh water reaches the open ocean directly in river plumes; nutrient export is even less efficient because of processing on continental shelves. Due to geographic differences in riverine nutrient delivery, dissolved silicate is the most efficiently exported to the open ocean (7-56.7%), while dissolved inorganic nitrogen is the least efficiently exported (2.8-44.3%). These results are consistent with previous estimates and provide a simple way to parameterize export to the open ocean in global models.

High evolutionary potential of marine zooplankton

PubMed Central

Peijnenburg, Katja T C A; Goetze, Erica

2013-01-01

Abstract Open ocean zooplankton often have been viewed as slowly evolving species that have limited capacity to respond adaptively to changing ocean conditions. Hence, attention has focused on the ecological responses of zooplankton to current global change, including range shifts and changing phenology. Here, we argue that zooplankton also are well poised for evolutionary responses to global change. We present theoretical arguments that suggest plankton species may respond rapidly to selection on mildly beneficial mutations due to exceptionally large population size, and consider the circumstantial evidence that supports our inference that selection may be particularly important for these species. We also review all primary population genetic studies of open ocean zooplankton and show that genetic isolation can be achieved at the scale of gyre systems in open ocean habitats (100s to 1000s of km). Furthermore, population genetic structure often varies across planktonic taxa, and appears to be linked to the particular ecological requirements of the organism. In combination, these characteristics should facilitate adaptive evolution to distinct oceanographic habitats in the plankton. We conclude that marine zooplankton may be capable of rapid evolutionary as well as ecological responses to changing ocean conditions, and discuss the implications of this view. We further suggest two priority areas for future research to test our hypothesis of high evolutionary potential in open ocean zooplankton, which will require (1) assessing how pervasive selection is in driving population divergence and (2) rigorously quantifying the spatial and temporal scales of population differentiation in the open ocean. Recent attention has focused on the ecological responses of open ocean zooplankton to current global change, including range shifts and changing phenology. Here, we argue that marine zooplankton also are well poised for evolutionary responses to global change. PMID:24567838

Future ocean hypercapnia driven by anthropogenic amplification of the natural CO2 cycle.

PubMed

McNeil, Ben I; Sasse, Tristan P

2016-01-21

High carbon dioxide (CO2) concentrations in sea-water (ocean hypercapnia) can induce neurological, physiological and behavioural deficiencies in marine animals. Prediction of the onset and evolution of hypercapnia in the ocean requires a good understanding of annual variations in oceanic CO2 concentration, but there is a lack of relevant global observational data. Here we identify global ocean patterns of monthly variability in carbon concentration using observations that allow us to examine the evolution of surface-ocean CO2 levels over the entire annual cycle under increasing atmospheric CO2 concentrations. We predict that the present-day amplitude of the natural oscillations in oceanic CO2 concentration will be amplified by up to tenfold in some regions by 2100, if atmospheric CO2 concentrations continue to rise throughout this century (according to the RCP8.5 scenario of the Intergovernmental Panel on Climate Change). The findings from our data are broadly consistent with projections from Earth system climate models. Our predicted amplification of the annual CO2 cycle displays distinct global patterns that may expose major fisheries in the Southern, Pacific and North Atlantic oceans to hypercapnia many decades earlier than is expected from average atmospheric CO2 concentrations. We suggest that these ocean 'CO2 hotspots' evolve as a combination of the strong seasonal dynamics of CO2 concentration and the long-term effective storage of anthropogenic CO2 in the oceans that lowers the buffer capacity in these regions, causing a nonlinear amplification of CO2 concentration over the annual cycle. The onset of ocean hypercapnia (when the partial pressure of CO2 in sea-water exceeds 1,000 micro-atmospheres) is forecast for atmospheric CO2 concentrations that exceed 650 parts per million, with hypercapnia expected in up to half the surface ocean by 2100, assuming a high-emissions scenario (RCP8.5). Such extensive ocean hypercapnia has detrimental implications for fisheries during the twenty-first century.

Future ocean hypercapnia driven by anthropogenic amplification of the natural CO2 cycle

NASA Astrophysics Data System (ADS)

McNeil, Ben I.; Sasse, Tristan P.

2016-01-01

High carbon dioxide (CO2) concentrations in sea-water (ocean hypercapnia) can induce neurological, physiological and behavioural deficiencies in marine animals. Prediction of the onset and evolution of hypercapnia in the ocean requires a good understanding of annual variations in oceanic CO2 concentration, but there is a lack of relevant global observational data. Here we identify global ocean patterns of monthly variability in carbon concentration using observations that allow us to examine the evolution of surface-ocean CO2 levels over the entire annual cycle under increasing atmospheric CO2 concentrations. We predict that the present-day amplitude of the natural oscillations in oceanic CO2 concentration will be amplified by up to tenfold in some regions by 2100, if atmospheric CO2 concentrations continue to rise throughout this century (according to the RCP8.5 scenario of the Intergovernmental Panel on Climate Change). The findings from our data are broadly consistent with projections from Earth system climate models. Our predicted amplification of the annual CO2 cycle displays distinct global patterns that may expose major fisheries in the Southern, Pacific and North Atlantic oceans to hypercapnia many decades earlier than is expected from average atmospheric CO2 concentrations. We suggest that these ocean ‘CO2 hotspots’ evolve as a combination of the strong seasonal dynamics of CO2 concentration and the long-term effective storage of anthropogenic CO2 in the oceans that lowers the buffer capacity in these regions, causing a nonlinear amplification of CO2 concentration over the annual cycle. The onset of ocean hypercapnia (when the partial pressure of CO2 in sea-water exceeds 1,000 micro-atmospheres) is forecast for atmospheric CO2 concentrations that exceed 650 parts per million, with hypercapnia expected in up to half the surface ocean by 2100, assuming a high-emissions scenario (RCP8.5). Such extensive ocean hypercapnia has detrimental implications for fisheries during the twenty-first century.

Vertical Redistribution of Ocean Salt Content

NASA Astrophysics Data System (ADS)

Liang, X.; Liu, C.; Ponte, R. M.; Piecuch, C. G.

2017-12-01

Ocean salinity is an important proxy for change and variability in the global water cycle. Multi-decadal trends have been observed in both surface and subsurface salinity in the past decades, and are usually attributed to the change in air-sea freshwater flux. Although air-sea freshwater flux, a major component of the global water cycle, certainly contributes to the change in surface and upper ocean salinity, the salt redistribution inside the ocean can affect the surface and upper ocean salinity as well. Also, the mechanisms controlling the surface and upper ocean salinity changes likely depend on timescales. Here we examined the ocean salinity changes as well as the contribution of the vertical redistribution of salt with a 20-year dynamically consistent and data-constrained ocean state estimate (ECCO: Estimating Circulation and Climate of the Ocean). A decrease in the spatial mean upper ocean salinity and an upward salt flux inside the ocean were observed. These findings indicate that over 1992-2011, surface freshwater fluxes contribute to the decrease in spatial mean upper ocean salinity and are partly compensated by the vertical redistribution of salt inside the ocean. Between advection and diffusion, the two major processes determining the vertical exchange of salt, the advective term at different depths shows a downward transport, while the diffusive term is the dominant upward transport contributor. These results suggest that the salt transport in the ocean interior should be considered in interpreting the observed surface and upper ocean salinity changes, as well as inferring information about the changes in the global water cycle.

Paleodust variability since the Last Glacial Maximum and implications for iron inputs to the ocean

NASA Astrophysics Data System (ADS)

Albani, S.; Mahowald, N. M.; Murphy, L. N.; Raiswell, R.; Moore, J. K.; Anderson, R. F.; McGee, D.; Bradtmiller, L. I.; Delmonte, B.; Hesse, P. P.; Mayewski, P. A.

2016-04-01

Changing climate conditions affect dust emissions and the global dust cycle, which in turn affects climate and biogeochemistry. In this study we use observationally constrained model reconstructions of the global dust cycle since the Last Glacial Maximum, combined with different simplified assumptions of atmospheric and sea ice processing of dust-borne iron, to provide estimates of soluble iron deposition to the oceans. For different climate conditions, we discuss uncertainties in model-based estimates of atmospheric processing and dust deposition to key oceanic regions, highlighting the large degree of uncertainty of this important variable for ocean biogeochemistry and the global carbon cycle. We also show the role of sea ice acting as a time buffer and processing agent, which results in a delayed and pulse-like soluble iron release into the ocean during the melting season, with monthly peaks up to ~17 Gg/month released into the Southern Oceans during the Last Glacial Maximum (LGM).

Turbulence Scaling Comparisons in the Ocean Surface Boundary Layer

NASA Astrophysics Data System (ADS)

Esters, L.; Breivik, Ø.; Landwehr, S.; ten Doeschate, A.; Sutherland, G.; Christensen, K. H.; Bidlot, J.-R.; Ward, B.

2018-03-01

Direct observations of the dissipation rate of turbulent kinetic energy, ɛ, under open ocean conditions are limited. Consequently, our understanding of what chiefly controls dissipation in the open ocean, and its functional form with depth, is poorly constrained. In this study, we report direct open ocean measurements of ɛ from the Air-Sea Interaction Profiler (ASIP) collected during five different cruises in the Atlantic Ocean. We then combine these data with ocean-atmosphere flux measurements and wave information in order to evaluate existing turbulence scaling theories under a diverse set of open ocean conditions. Our results do not support the presence of a "breaking" or a "transition layer," which has been previously suggested. Instead, ɛ decays as |z|-1.29 over the depth interval, which was previously defined as "transition layer," and as |z|-1.15 over the mixing layer. This depth dependency does not significantly vary between nonbreaking or breaking wave conditions. A scaling relationship based on the friction velocity, the wave age, and the significant wave height describes the observations best for daytime conditions. For conditions during which convection is important, it is necessary to take buoyancy forcing into account.

Astronomical constraints on the duration of the Early Jurassic Pliensbachian Stage and global climatic fluctuations

NASA Astrophysics Data System (ADS)

Ruhl, Micha; Hesselbo, Stephen P.; Hinnov, Linda; Jenkyns, Hugh C.; Xu, Weimu; Riding, James B.; Storm, Marisa; Minisini, Daniel; Ullmann, Clemens V.; Leng, Melanie J.

2016-12-01

The Early Jurassic was marked by multiple periods of major global climatic and palaeoceanographic change, biotic turnover and perturbed global geochemical cycles, commonly linked to large igneous province volcanism. This epoch was also characterised by the initial break-up of the super-continent Pangaea and the opening and formation of shallow-marine basins and ocean gateways, the timing of which are poorly constrained. Here, we show that the Pliensbachian Stage and the Sinemurian-Pliensbachian global carbon-cycle perturbation (marked by a negative shift in δ13 C of 2- 4 ‰), have respective durations of ∼8.7 and ∼2 Myr. We astronomically tune the floating Pliensbachian time scale to the 405 Kyr eccentricity solution (La2010d), and propose a revised Early Jurassic time scale with a significantly shortened Sinemurian Stage duration of 6.9 ± 0.4 Myr. When calibrated against the new time scale, the existing Pliensbachian seawater 87Sr/86Sr record shows relatively stable values during the first ∼2 Myr of the Pliensbachian, superimposed on the long-term Early Jurassic decline in 87Sr/86Sr. This plateau in 87Sr/86Sr values coincides with the Sinemurian-Pliensbachian boundary carbon-cycle perturbation. It is possibly linked to a late phase of Central Atlantic Magmatic Province (CAMP) volcanism that induced enhanced global weathering of continental crustal materials, leading to an elevated radiogenic strontium flux to the global ocean.

Climate, carbon cycling, and deep-ocean ecosystems.

PubMed

Smith, K L; Ruhl, H A; Bett, B J; Billett, D S M; Lampitt, R S; Kaufmann, R S

2009-11-17

Climate variation affects surface ocean processes and the production of organic carbon, which ultimately comprises the primary food supply to the deep-sea ecosystems that occupy approximately 60% of the Earth's surface. Warming trends in atmospheric and upper ocean temperatures, attributed to anthropogenic influence, have occurred over the past four decades. Changes in upper ocean temperature influence stratification and can affect the availability of nutrients for phytoplankton production. Global warming has been predicted to intensify stratification and reduce vertical mixing. Research also suggests that such reduced mixing will enhance variability in primary production and carbon export flux to the deep sea. The dependence of deep-sea communities on surface water production has raised important questions about how climate change will affect carbon cycling and deep-ocean ecosystem function. Recently, unprecedented time-series studies conducted over the past two decades in the North Pacific and the North Atlantic at >4,000-m depth have revealed unexpectedly large changes in deep-ocean ecosystems significantly correlated to climate-driven changes in the surface ocean that can impact the global carbon cycle. Climate-driven variation affects oceanic communities from surface waters to the much-overlooked deep sea and will have impacts on the global carbon cycle. Data from these two widely separated areas of the deep ocean provide compelling evidence that changes in climate can readily influence deep-sea processes. However, the limited geographic coverage of these existing time-series studies stresses the importance of developing a more global effort to monitor deep-sea ecosystems under modern conditions of rapidly changing climate.

Pelagic Nitrogen Cycle Observations In The Arctic Ocean - How Might They Change In Response To Ocean Acidification?

NASA Astrophysics Data System (ADS)

Clark, D. R.; Rees, A.; Brown, I.; Al-Moosawi, L.; Cripps, G.

2016-02-01

Phytoplankton forms the base of marine food webs by assimilating nutrients and generating biomass that supports higher trophic levels. Conversely, marine heterotrophs degrade organic matter produced by phytoplankton and recycle nutrients, maintaining food web integrity. We investigated the assimilation and regeneration of dissolved inorganic nitrogen (DIN) at stations located in the Arctic Ocean. In addition, we measured the concentration of nitrous oxide, a by-product of N-regeneration (specifically nitrification) and a climatically active gas. Measurements demonstrated the simultaneous regeneration and assimilation of ammonium, nitrite and nitrate at open ocean, ice-edge and within-ice locations. Ammonium was regenerated and assimilated within the range 0.2-4.5 nmol·L-1·h-1 and 0.5-24.8 nmol·L-1·h-1 respectively. Nitrite was regenerated and assimilated within the range 0.1-9.2 nmol·L-1·h-1 and 0.0-6.9 nmol·L-1·h-1 respectively. Nitrate was regenerated and assimilated within the range 0.3-372.7 nmol·L-1·h-1 and 0.1-48.3 nmol·L-1·h-1 respectively. Results indicated that the ice-edge was associated with enhanced DIN assimilation. The concentration of nitrous oxide (<100m) averaged 11.8±2.2 nmol·L-1, which was approximately 15% higher than measured in the European shelf seas and most likely related only to temperature. In separate experiments, the influence of ocean acidification (OA) upon nitrogen cycle processes was investigated. The carbonate system of photic zone seawater (depth <10m) was modified to achieve a range of PCO2 concentrations using bioassay experiments. Preliminary results indicated that NH4+ oxidation and the concentration of nitrous oxide did not respond in a clear or consistent way to OA treatments. In contrast, the regeneration of NH4+ increased in response to elevated PCO2. The bacterial degradation of organic matter may be enhanced in the Arctic Ocean in response to OA, potentially modifying DIN pool composition and concentration in the future.

Modelling of Soluble Iron Formation, Transport and Deposition to the North Pacific Ocean, Role of Anthropogenic Pollutants.

NASA Astrophysics Data System (ADS)

Solmon, F.; Chuang, P.; Meskhidze, N.

2006-12-01

Soluble iron deposited via atmospheric processes represents an important nutrient for open ocean ecosystems, which might influence phytoplancton productivity and atmospheric carbon uptake. Atmospheric deposition of mineral dust is known to be the essential supply of iron to the ocean. However, most of the iron contained in mineral particles is unsoluble, whereas only the soluble fraction of the iron is thought to be effectively bio-available. There is still a great deal of uncertainties in the estimation of this fraction and the representation of iron solubilisation processes in the atmosphere. In this scope, we present a modeling study aiming at better representing such processes. In particular, we focus on the different roles of anthropogenic chemical compounds in the atmospheric iron cycle and deposition. These roles are of two orders : (i) the acidification of mineral particles by anthropogenic compounds influencing the solubilisation of the iron transported and (ii) the direct emission, transport and deposition of iron emitted by anthropogenic activities. For this study, we implement a set of specific mechanisms in the global chemistry transport model GEOS- CHEM. Our study focuses on the East Asia - North pacific outflow, a region where interactions between dust and pollution are particularly likely to occur and where the ocean ecosystem is known to be iron limited.

Caribbean Oceans: Utilizing NASA Earth Observations to Detect, Monitor, and Respond to Unprecedented Levels of Sargassum in the Caribbean Sea

NASA Technical Reports Server (NTRS)

Ped, Jordan; Scaduto, Erica; Accorsi, Emma; Torres-Perez, Juan (Editor)

2016-01-01

In 2011 and 2015, the nations of the Caribbean Sea were overwhelmed by the unprecedented quantity of Sargassum that washed ashore. This issue prompted international discussion to better understand the origins, distribution, and movement of Sargassum, a free-floating brown macro alga with ecological, environmental, and commercial importance. In the open ocean, Sargassum mats serve a vital ecological function. However, when large quantities appear onshore without warning, Sargassum threatens local tourist industries and nearshore ecosystems within the Caribbean. As part of the international response, this project investigated the proliferation of this macro alga within the Caribbean Sea from 2003-2015, and used NASA Earth observations to detect and model Sargassum growth across the region. The Caribbean Oceans team calculated the Floating Algal Index (FAI) using Terra Moderate Resolution Imaging Spectroradiometer (MODIS) data, and compared the FAI to various oceanic variables to determine the ideal pelagic environment for Sargassum growth. The project also examined the annual spread of Sargassum throughout the region by using Earth Trends Modeler (ETM) in Clark Labs' TerrSet software. As part of the international effort to better understand the life cycle of Sargassum in the Caribbean, the results of this project will help local economies promote sustainable management practices in the region.

Biological production in the Indian Ocean upwelling zones - Part 1: refined estimation via the use of a variable compensation depth in ocean carbon models

NASA Astrophysics Data System (ADS)

Geethalekshmi Sreeush, Mohanan; Valsala, Vinu; Pentakota, Sreenivas; Venkata Siva Rama Prasad, Koneru; Murtugudde, Raghu

2018-04-01

Biological modelling approach adopted by the Ocean Carbon-Cycle Model Intercomparison Project (OCMIP-II) provided amazingly simple but surprisingly accurate rendition of the annual mean carbon cycle for the global ocean. Nonetheless, OCMIP models are known to have seasonal biases which are typically attributed to their bulk parameterisation of compensation depth. Utilising the criteria of surface Chl a-based attenuation of solar radiation and the minimum solar radiation required for production, we have proposed a new parameterisation for a spatially and temporally varying compensation depth which captures the seasonality in the production zone reasonably well. This new parameterisation is shown to improve the seasonality of CO2 fluxes, surface ocean pCO2, biological export and new production in the major upwelling zones of the Indian Ocean. The seasonally varying compensation depth enriches the nutrient concentration in the upper ocean yielding more faithful biological exports which in turn leads to accurate seasonality in the carbon cycle. The export production strengthens by ˜ 70 % over the western Arabian Sea during the monsoon period and achieves a good balance between export and new production in the model. This underscores the importance of having a seasonal balance in the model export and new productions for a better representation of the seasonality of the carbon cycle over upwelling regions. The study also implies that both the biological and solubility pumps play an important role in the Indian Ocean upwelling zones.

SeaWiFS technical report series. Volume 1: An overview of SeaWiFS and ocean color

NASA Technical Reports Server (NTRS)

Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor); Esaias, Wayne E.; Feldman, Gene C.; Gregg, Watson W.; Mcclain, Charles R.

1992-01-01

The purpose of this series of technical reports is to provide current documentation of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Project activities, instrument performance, algorithms, and operations. This documentation is necessary to ensure that critical information related to the quality and calibration of the satellite data is available to the scientific community. SeaWiFS will bring to the ocean community a welcomed and improved renewal of the ocean color remote sensing capability lost when the Nimbus-7 Coastal Zone Color Scanner (CZCS) ceased operating in 1986. The goal of SeaWiFS, scheduled to be launched in August 1993, is to examine oceanic factors that affect global change. Because of the role of phytoplankton in the global carbon cycle, data obtained from SeaWiFS will be used to assess the ocean's role in this cycle, as well as other biogeochemical cycles. SeaWiFS data will be used to help elucidate the magnitude and variability of the annual cycle of primary production by marine phytoplankton and to determine the distribution and timing of spring blooms. The observations will help to visualize the dynamics of ocean and costal currents, the physics of mixing, and the relationships between ocean physics and large-scale patterns of productivity. The data will help fill the gap in ocean biological observations between those of the CZCS and the upcoming Moderate Resolution Imaging Spectrometer (MODIS) on the Earth Observing System-A (EOS-A) satellite.

Climate and CO2 coupling in the early Cenozoic Greenhouse

NASA Astrophysics Data System (ADS)

Rae, J. W. B.; Greenop, R.; Kaminski, M.; Sexton, P. F.; Foster, G. L.; Greene, S. E.; Littley, E.; Kirtland Turner, S.; Ridgwell, A.

2017-12-01

The early Cenozoic is a time of climatic extremes: hyperthermals pepper the transition from extreme global warmth to the start of Cenozoic cooling, with these evolving climate regimes accompanied by major changes in ocean chemistry and biota. The exogenic carbon cycle, and ocean-atmospheric CO2 in particular, is thought to have played a key role in these climatic changes, but the carbon chemistry of the early Cenozoic ocean remains poorly constrained. Here we present new boron isotope data from benthic foraminifera, which can be used to constrain relative changes in ocean pH. These are coupled with modelling experiments performed with the cGenie Earth system model to provide new constraints on the carbon cycle and carbonate system of the early Cenozoic. While our benthic boron isotope data do not readily provide a record of surface ocean CO2 , they do place constraints on the whole ocean-atmosphere carbonate system, alongside changes in ocean circulation and biogeochemistry, and also have relatively robust calcite tests and small `vital effects'. During the late Paleocene ascent to peak greenhouse conditions and the middle Eocene descent towards the icehouse, our boron isotope data show close coupling with benthic δ18O, demonstrating a clear link between CO2 and climate. However within the early Eocene our boron isotope data reveal more dynamic changes in deep ocean pH, which may be linked to changes in ocean circulation. Overall, our data demonstrate the ability of CO2 to regulate the climate system across varying boundary conditions, and the influence of both the long-term carbon cycle and shorter-term ocean biogeochemical cycling on Earth's climate.

Freshwater and its role in the Arctic Marine System: Sources, disposition, storage, export, and physical and biogeochemical consequences in the Arctic and global oceans

NASA Astrophysics Data System (ADS)

Carmack, E. C.; Yamamoto-Kawai, M.; Haine, T. W. N.; Bacon, S.; Bluhm, B. A.; Lique, C.; Melling, H.; Polyakov, I. V.; Straneo, F.; Timmermans, M.-L.; Williams, W. J.

2016-03-01

The Arctic Ocean is a fundamental node in the global hydrological cycle and the ocean's thermohaline circulation. We here assess the system's key functions and processes: (1) the delivery of fresh and low-salinity waters to the Arctic Ocean by river inflow, net precipitation, distillation during the freeze/thaw cycle, and Pacific Ocean inflows; (2) the disposition (e.g., sources, pathways, and storage) of freshwater components within the Arctic Ocean; and (3) the release and export of freshwater components into the bordering convective domains of the North Atlantic. We then examine physical, chemical, or biological processes which are influenced or constrained by the local quantities and geochemical qualities of freshwater; these include stratification and vertical mixing, ocean heat flux, nutrient supply, primary production, ocean acidification, and biogeochemical cycling. Internal to the Arctic the joint effects of sea ice decline and hydrological cycle intensification have strengthened coupling between the ocean and the atmosphere (e.g., wind and ice drift stresses, solar radiation, and heat and moisture exchange), the bordering drainage basins (e.g., river discharge, sediment transport, and erosion), and terrestrial ecosystems (e.g., Arctic greening, dissolved and particulate carbon loading, and altered phenology of biotic components). External to the Arctic freshwater export acts as both a constraint to and a necessary ingredient for deep convection in the bordering subarctic gyres and thus affects the global thermohaline circulation. Geochemical fingerprints attained within the Arctic Ocean are likewise exported into the neighboring subarctic systems and beyond. Finally, we discuss observed and modeled functions and changes in this system on seasonal, annual, and decadal time scales and discuss mechanisms that link the marine system to atmospheric, terrestrial, and cryospheric systems.

Impact of resolving the diurnal cycle in an ocean-atmosphere GCM. Part 2: A diurnally coupled CGCM

NASA Astrophysics Data System (ADS)

Bernie, D. J.; Guilyardi, E.; Madec, G.; Slingo, J. M.; Woolnough, S. J.; Cole, J.

2008-12-01

Coupled ocean atmosphere general circulation models (GCM) are typically coupled once every 24 h, excluding the diurnal cycle from the upper ocean. Previous studies attempting to examine the role of the diurnal cycle of the upper ocean and particularly of diurnal SST variability have used models unable to resolve the processes of interest. In part 1 of this study a high vertical resolution ocean GCM configuration with modified physics was developed that could resolve the diurnal cycle in the upper ocean. In this study it is coupled every 3 h to atmospheric GCM to examine the sensitivity of the mean climate simulation and aspects of its variability to the inclusion of diurnal ocean-atmosphere coupling. The inclusion of the diurnal cycle leads to a tropics wide increase in mean sea surface temperature (SST), with the strongest signal being across the equatorial Pacific where the warming increases from 0.2°C in the central and western Pacific to over 0.3°C in the eastern equatorial Pacific. Much of this warming is shown to be a direct consequence of the rectification of daily mean SST by the diurnal variability of SST. The warming of the equatorial Pacific leads to a redistribution of precipitation from the Inter tropical convergence zone (ITCZ) toward the equator. In the western Pacific there is an increase in precipitation between Papa new guinea and 170°E of up to 1.2 mm/day, improving the simulation compared to climatology. Pacific sub tropical cells are increased in strength by about 10%, in line with results of part 1 of this study, due to the modification of the exchange of momentum between the equatorially divergent Ekman currents and the geostropic convergence at depth, effectively increasing the dynamical response of the tropical Pacific to zonal wind stresses. During the spring relaxation of the Pacific trade winds, a large diurnal cycle of SST increases the seasonal warming of the equatorial Pacific. When the trade winds then re-intensify, the increase in the dynamical response of the ocean leads to a stronger equatorial upwelling. These two processes both lead to stronger seasonal basin scale feedbacks in the coupled system, increasing the strength of the seasonal cycle of the tropical Pacific sector by around 10%. This means that the diurnal cycle in the upper ocean plays a part in the coupled feedbacks between ocean and atmosphere that maintain the basic state and the timing of the seasonal cycle of SST and trade winds in the tropical Pacific. The Madden-Julian Oscillation (MJO) is examined by use of a large scale MJO index, lag correlations and composites of events. The inclusion of the diurnal cycle leads to a reduction in overall MJO activity. Precipitation composites show that the MJO is stronger and more coherent when the diurnal cycle of coupling is resolved, with the propagation and different phases being far more distinct both locally and to larger lead times across the tropical Indo-Pacific. Part one of this study showed that that diurnal variability of SST is modulated by the MJO and therefore increases the intraseasonal SST response to the different phases of the MJO. Precipitation-based composites of SST variability confirm this increase in the coupled simulations. It is argued that including this has increased the thermodynamical coupling of the ocean and atmosphere on the timescale of the MJO (20-100 days), accounting for the improvement in the MJO strength and coherency seen in composites of precipitation and SST. These results show that the diurnal cycle of ocean-atmosphere interaction has profound impact on a range of up-scale variability in the tropical climate and as such, it is an important feature of the modelled climate system which is currently either neglected or poorly resolved in state of the art coupled models.

The biological carbon pump in the ocean: Reviewing model representations and its feedbacks on climate perturbations.

NASA Astrophysics Data System (ADS)

Hülse, Dominik; Arndt, Sandra; Ridgwell, Andy; Wilson, Jamie

2016-04-01

The ocean-sediment system, as the biggest carbon reservoir in the Earth's carbon cycle, plays a crucial role in regulating atmospheric carbon dioxide concentrations and climate. Therefore, it is essential to constrain the importance of marine carbon cycle feedbacks on global warming and ocean acidification. Arguably, the most important single component of the ocean's carbon cycle is the so-called "biological carbon pump". It transports carbon that is fixed in the light-flooded surface layer of the ocean to the deep ocean and the surface sediment, where it is degraded/dissolved or finally buried in the deep sediments. Over the past decade, progress has been made in understanding different factors that control the efficiency of the biological carbon pump and their feedbacks on the global carbon cycle and climate (i.e. ballasting = ocean acidification feedback; temperature dependant organic matter degradation = global warming feedback; organic matter sulphurisation = anoxia/euxinia feedback). Nevertheless, many uncertainties concerning the interplay of these processes and/or their relative significance remain. In addition, current Earth System Models tend to employ empirical and static parameterisations of the biological pump. As these parametric representations are derived from a limited set of present-day observations, their ability to represent carbon cycle feedbacks under changing climate conditions is limited. The aim of my research is to combine past carbon cycling information with a spatially resolved global biogeochemical model to constrain the functioning of the biological pump and to base its mathematical representation on a more mechanistic approach. Here, I will discuss important aspects that control the efficiency of the ocean's biological carbon pump, review how these processes of first order importance are mathematically represented in existing Earth system Models of Intermediate Complexity (EMIC) and distinguish different approaches to approximate biogeochemical processes in the sediments. The performance of the respective mathematical representations in constraining the importance of carbon pump feedbacks on marine biogeochemical dynamics is then compared and evaluated under different extreme climate scenarios (e.g. OAE2, Eocene) using the Earth system model 'GENIE' and proxy records. The compiled mathematical descriptions and the model results underline the lack of a complete and mechanistic framework to represent the short-term carbon cycle in most EMICs which seriously limits the ability of these models to constrain the response of the ocean's carbon cycle to past and in particular future climate change. In conclusion, this presentation will critically evaluate the approaches currently used in marine biogeochemical modelling and outline key research directions concerning model development in the future.

Oceanic dispersion of Fukushima-derived Cs-137 in the coastal, offshore, and open oceans simulated by multiple oceanic general circulation models

NASA Astrophysics Data System (ADS)

Kawamura, H.; Furuno, A.; Kobayashi, T.; In, T.; Nakayama, T.; Ishikawa, Y.; Miyazawa, Y.; Usui, N.

2017-12-01

To understand the concentration and amount of Fukushima-derived Cs-137 in the ocean, this study simulates the oceanic dispersion of Cs-137 by an oceanic dispersion model SEA-GEARN-FDM developed at Japan Atomic Energy Agency (JAEA) and multiple oceanic general circulation models. The Cs-137 deposition amounts at the sea surface were used as the source term in oceanic dispersion simulations, which were estimated by atmospheric dispersion simulations with a Worldwide version of System for Prediction of Environmental Emergency Dose Information version II (WSPEEDI-II) developed at JAEA. The direct release from the Fukushima Daiichi Nuclear Power Plant into the ocean based on in situ Cs-137 measurements was used as the other source term in oceanic dispersion simulations. The simulated air Cs-137 concentrations qualitatively replicated those measured around the North Pacific. The accumulated Cs-137 ground deposition amount in the eastern Japanese Islands was consistent with that estimated by aircraft measurements. The oceanic dispersion simulations relatively well reproduced the measured Cs-137 concentrations in the coastal and offshore oceans during the first few months after the Fukushima disaster, and in the open ocean during the first year post-disaster. It was suggested that Cs-137 dispersed along the coast in the north-south direction during the first few months post-disaster, and were subsequently dispersed offshore by the Kuroshio Current and Kuroshio Extension. Mesoscale eddies accompanied by the Kuroshio Current and Kuroshio Extension played an important role in dilution of Cs-137. The Cs-137 amounts were quantified in the coastal, offshore, and open oceans during the first year post-disaster. It was demonstrated that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layer in the North Pacific.

Observations of Ocean Primary Productivity Using MODIS

NASA Technical Reports Server (NTRS)

Esaias, Wayne E.; Abbott, Mark R.; Koblinsky, Chester J. (Technical Monitor)

2001-01-01

Measuring the magnitude and variability of oceanic net primary productivity (NPP) represents a key advancement toward our understanding of the dynamics of marine ecosystems and the role of the ocean in the global carbon cycle. MODIS observations make two new contributions in addition to continuing the bio-optical time series begun with Orbview-2's SeaWiFS sensor. First, MODIS provides weekly estimates of global ocean net primary productivity on weekly and annual time periods, and annual empirical estimates of carbon export production. Second, MODIS provides additional insight into the spatial and temporal variations in photosynthetic efficiency through the direct measurements of solar-stimulated chlorophyll fluorescence. The two different weekly productivity indexes (first developed by Behrenfeld & Falkowski and by Yoder, Ryan and Howard) are used to derive daily productivity as a function of chlorophyll biomass, incident daily surface irradiance, temperature, euphotic depth, and mixed layer depth. Comparisons between these two estimates using both SeaWiFS and MODIS data show significant model differences in spatial distribution after allowance for the different integration depths. Both estimates are strongly dependence on the accuracy of the chlorophyll determination. In addition, an empirical approach is taken on annual scales to estimate global NPP and export production. Estimates of solar stimulated fluorescence efficiency from chlorophyll have been shown to be inversely related to photosynthetic efficiency by Abbott and co-workers. MODIS provides the first global estimates of oceanic chlorophyll fluorescence, providing an important proof of concept. MODIS observations are revealing spatial patterns of fluorescence efficiency which show expected variations with phytoplankton photo-physiological parameters as measured during in-situ surveys. This has opened the way for research into utilizing this information to improve our understanding of oceanic NPP variability. Deriving the ocean bio-optical properties places severe demands on instrument performance (especially band to band precision) and atmospheric correction. Improvements in MODIS instrument characterization and calibration over the first 16 mission months have greatly improved the accuracy of the chlorophyll input fields and FLH, and therefore the estimates of NPP and fluorescence efficiency. Annual estimates now show the oceanic NPP accounts for 40-50% of the global total NPP, with significant interannual variations related to large scale ocean processes. Spatial variations in ocean NPP, and exported production, have significant effects on exchange of CO2 between the ocean and atmosphere. Further work is underway to improve both the primary productivity model functions, and to refine our understanding of the relationships between fluorescence efficiency and NPP estimates. We expect that the MODIS instruments will prove extremely useful in assessing the time dependencies of oceanic carbon uptake and effects of iron enrichment, within the global carbon cycle.

Energy Conversion Alternatives Study (ECAS), General Electric Phase 1. Volume 2: Advanced energy conversion systems. Part 1: Open-cycle gas turbines

NASA Technical Reports Server (NTRS)

Brown, D. H.; Corman, J. C.

1976-01-01

Ten energy conversion systems are defined and analyzed in terms of efficiency. These include: open-cycle gas turbine recuperative; open-cycle gas turbine; closed-cycle gas turbine; supercritical CO2 cycle; advanced steam cycle; liquid metal topping cycle; open-cycle MHD; closed-cycle inert gas MHD; closed-cycle liquid metal MHD; and fuel cells. Results are presented.

The ocean mixed layer under Southern Ocean sea-ice: seasonal cycle and forcing.

NASA Astrophysics Data System (ADS)

Violaine, P.; Sallee, J. B.; Schmidtko, S.; Roquet, F.; Charrassin, J. B.

2016-02-01

The mixed-layer at the surface of the ocean is the gateway for all exchanges between air and sea. A vast area of the Southern Ocean is however seasonally capped by sea-ice, which alters this gateway and the characteristic the ocean mixed-layer. The interaction between the ocean mixed-layer and sea-ice plays a key role for water-mass formation and circulation, carbon cycle, sea-ice dynamics, and ultimately for the climate as a whole. However, the structure and characteristics of the mixed layer, as well as the processes responsible for its evolution, are poorly understood due to the lack of in-situ observations and measurements. We urgently need to better understand the forcing and the characteristics of the ocean mixed-layer under sea-ice if we are to understand and predict the world's climate. In this study, we combine a range of distinct sources of observation to overcome this lack in our understanding of the Polar Regions. Working on Elephant Seal-derived data as well as ship-based observations and Argo float data, we describe the seasonal cycle of the characteristics and stability of the ocean mixed layer over the entire Southern Ocean (South of 40°S), and specifically under sea-ice. Mixed-layer budgets of heat and freshwater are used to investigate the main forcings of the mixed-layer seasonal cycle. The seasonal variability of sea surface salinity and temperature are primarily driven by surface processes, dominated by sea-ice freshwater flux for the salt budget, and by air-sea flux for the heat budget. Ekman advection, vertical diffusivity and vertical entrainment play only secondary role.Our results suggest that changes in regional sea-ice distribution or sea-ice seasonal cycle duration, as currently observed, would widely affect the buoyancy budget of the underlying mixed-layer, and impacts large-scale water-mass formation and transformation.

Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide

PubMed Central

Wernand, Marcel R.; van der Woerd, Hendrik J.; Gieskes, Winfried W. C.

2013-01-01

Marine primary productivity is an important agent in the global cycling of carbon dioxide, a major ‘greenhouse gas’, and variations in the concentration of the ocean's phytoplankton biomass can therefore explain trends in the global carbon budget. Since the launch of satellite-mounted sensors globe-wide monitoring of chlorophyll, a phytoplankton biomass proxy, became feasible. Just as satellites, the Forel-Ule (FU) scale record (a hardly explored database of ocean colour) has covered all seas and oceans – but already since 1889. We provide evidence that changes of ocean surface chlorophyll can be reconstructed with confidence from this record. The EcoLight radiative transfer numerical model indicates that the FU index is closely related to chlorophyll concentrations in open ocean regions. The most complete FU record is that of the North Atlantic in terms of coverage over space and in time; this dataset has been used to test the validity of colour changes that can be translated to chlorophyll. The FU and FU-derived chlorophyll data were analysed for monotonously increasing or decreasing trends with the non-parametric Mann-Kendall test, a method to establish the presence of a consistent trend. Our analysis has not revealed a globe-wide trend of increase or decrease in chlorophyll concentration during the past century; ocean regions have apparently responded differentially to changes in meteorological, hydrological and biological conditions at the surface, including potential long-term trends related to global warming. Since 1889, chlorophyll concentrations have decreased in the Indian Ocean and in the Pacific; increased in the Atlantic Ocean, the Mediterranean, the Chinese Sea, and in the seas west and north-west of Japan. This suggests that explanations of chlorophyll changes over long periods should focus on hydrographical and biological characteristics typical of single ocean regions, not on those of ‘the’ ocean. PMID:23776435

Wilson study cycles: Research relative to ocean geodynamic cycles

NASA Technical Reports Server (NTRS)

Kidd, W. S. F.

1985-01-01

The effects of conversion of Atlantic (rifted) margins to convergent plate boundaries; oceanic plateaus at subduction zones; continental collision and tectonic escape; southern Africa rifts; and global hot spot distribution on long term development of the continental lithosphere were studied.

Sensitivity of Calibration Gains to Ocean Color Processing in Coastal and Open Waters Using Ensembles Members for NPP-VIIRS

DTIC Science & Technology

2014-07-01

a different impact on spectral normalized water leaving radiances and the derived ocean color products (inherent optical properties, chlorophyll ). We...leaving radiances and the derived ocean color products (inherent optical properties, chlorophyll ). We evaluated the influence of gains from open and...34gain" on ocean color products. These products include the spectral Remote Sensing Reflectance (RRS), chlorophyll concentration, and Inherent Optical

LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model

NASA Astrophysics Data System (ADS)

Zeebe, R. E.

2011-06-01

The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

50 CFR 648.15 - Facilitation of enforcement.

Code of Federal Regulations, 2010 CFR

2010-10-01

... ocean quahog open access permitted vessels. Vessel owners or operators issued an open access surfclam or ocean quahog open access permit for fishing in the ITQ Program, as specified at § 648.70, are required... limited access permitted vessels. Beginning January 1, 2009, vessel owners or operators issued a limited...

Role of the Indonesian Throughflow in controlling regional mean climate and rainfall variability

NASA Astrophysics Data System (ADS)

England, Matthew H.; Santoso, Agus; Phipps, Steven; Ummenhofer, Caroline

2017-04-01

The role of the Indonesian Throughflow (ITF) in controlling regional mean climate and rainfall is examined using a coupled ocean-atmosphere general circulation model. Experiments employing both a closed and open ITF are equilibrated to steady state and then 200 years of natural climatic variability is assessed within each model run, with a particular focus on the Indian Ocean region. Opening of the ITF results in a mean Pacific-to-Indian throughflow of 21 Sv (1 Sv = 106 m3 sec-1), which advects warm west Pacific waters into the east Indian Ocean. This warm signature is propagated westward by the mean ocean flow, however it never reaches the west Indian Ocean, as an ocean-atmosphere feedback in the tropics generates a weakened trade wind field that is reminiscent of the negative phase of the Indian Ocean Dipole (IOD). This is in marked contrast to the Indian Ocean response to an open ITF when examined in ocean-only model experiments; which sees a strengthening of both the Indian Ocean South Equatorial Current and the Agulhas Current. The coupled feedback in contrast leads to cooler conditions over the west Indian Ocean, and an anomalous zonal atmospheric pressure gradient that enhances the advection of warm moist air toward south Asia and Australia. This leaves the African continent significantly drier, and much of Australia and southern Asia significantly wetter, in response to the opening of the ITF. Given the substantial interannual variability that the ITF exhibits in the present-day climate system, and the restriction of the ITF gateway in past climate eras, this could have important implications for understanding past and present regional rainfall patterns around the Indian Ocean and over neighbouring land-masses.

Factors controlling the photochemical degradation of methylmercury in coastal and oceanic waters

PubMed Central

DiMento, Brian P.; Mason, Robert P.

2018-01-01

Many studies have recognized abiotic photochemical degradation as an important sink of methylmercury (CH3Hg) in sunlit surface waters, but the rate-controlling factors remain poorly understood. The overall objective of this study was to improve our understanding of the relative importance of photochemical reactions in the degradation of CH3Hg in surface waters across a variety of marine ecosystems by extending the range of water types studied. Experiments were conducted using surface water collected from coastal sites in Delaware, New Jersey, Connecticut, and Maine, as well as offshore sites on the New England continental shelf break, the equatorial Pacific, and the Arctic Ocean. Filtered water amended with additional CH3Hg at environmentally relevant concentrations was allowed to equilibrate with natural ligands before being exposed to natural sunlight. Water quality parameters – salinity, dissolved organic carbon, and nitrate – were measured, and specific UV absorbance was calculated as a proxy for dissolved aromatic carbon content. Degradation rate constants (0.87–1.67 day−1) varied by a factor of two across all water types tested despite varying characteristics, and did not correlate with initial CH3Hg concentrations or other environmental parameters. The rate constants in terms of cumulative photon flux values were comparable to, but at the high end of, the range of values reported in other studies. Further experiments investigating the controlling parameters of the reaction observed little effect of nitrate and chloride, and potential for bromide involvement. The HydroLight radiative transfer model was used to compute solar irradiance with depth in three representative water bodies – coastal wetland, estuary, and open ocean – allowing for the determination of water column integrated rates. Methylmercury loss per year due to photodegradation was also modeled across a range of latitudes from the Arctic to the Equator in the three model water types, resulting in an estimated global demethylation rate of 25.3 Mmol yr−1. The loss of CH3Hg was greatest in the open ocean due to increased penetration of all wavelengths, especially the UV portion of the spectrum which has a greater ability to degrade CH3Hg. Overall, this study provides additional insights and information to better constrain the importance of photochemical degradation in the cycling of CH3Hg in marine surface waters and its transport from coastal waters to the open ocean. PMID:29515285

How much riverine nutrients do shelf seas allow into the open ocean?

NASA Astrophysics Data System (ADS)

Sharples, J.; Fennel, K.; Jickells, T. D.

2016-02-01

Globally rivers deliver 35 Tg of dissolved N and 2 Tg of dissolved P into the coastal zone each year. Investigating the effects of this nutrient supply on the open ocean generally takes one of two approaches: either all or none of the nutrients are assumed to enter the open ocean. Here we use some general assumptions on the behaviour of river plumes on the shelf to arrive at an estimate of the proportions of dissolved N and P that are processed on the shelf, and thus the amount of riverine nutrient that enters the open ocean. Using the Global NEWS database of 6000 rivers we assume that discharges to the shelf are initially constrained within coastal buoyancy currents of width 2 internal Rossby radii. This width is compared to the local shelf width for each river. For plume widths greater than the shelf width riverine nutrients are assumed to be transported over the shelf edge within the plume. For plume widths less than the shelf width we assume that exchange with the open ocean is controlled by physical processes at the shelf break. For each river an estimate of the residence time of riverine water is made, based on the transport or exchange rate and the shelf volume. Empirical relationships between residence time and the proportion of supplied N and P that is retained on the shelf are then used to estimate the amount of dissolved N and P that escapes to the open ocean. The results suggest that 25% of dissolved N and 20% of dissolved P are processed in shelf seas, with the rest exported to the open ocean. There is a latitudinal pattern, with tropical rivers delivering more nutrients to the open ocean. This is partially a result of the high discharges of some tropical rivers, but a key issue is our assumption of the internal Rossby radius governing plume width. A range of values for transport rates within plumes and exchange rates across the shelf break are used to assess the sensitivity of these results, which appear to be robust.

Dynamics of upwelling annual cycle in the equatorial Atlantic Ocean

NASA Astrophysics Data System (ADS)

Wang, Li-Chiao; Jin, Fei-Fei; Wu, Chau-Ron; Hsu, Huang-Hsiung

2017-04-01

The annual upwelling is an important component of the equatorial Atlantic annual cycle. A simple theory is proposed using the framework of Zebiak-Cane (ZC) ocean model for insights into the dynamics of the upwelling annual cycle. It is demonstrated that in the Atlantic equatorial region this upwelling is dominated by Ekman processing in the west, whereas in the east it is primarily owing to shoaling and deepening of the thermocline resulting from equatorial mass meridional recharge/discharge and zonal redistribution processes associated with wind-driven equatorial ocean waves. This wind-driven wave upwelling plays an important role in the development of the annual cycle in the sea surface temperature of the cold tongue in the eastern equatorial Atlantic.

Cosmogenic 32P and 33P in the Atmosphere and Oligotrophic Ocean and Applications to the Study of Phosphorus Cycling

DTIC Science & Technology

1993-02-01

Ed.) , pp53-82. Poet, S.E., Moore H.E., and EA. Martell, 1972. Lead- 210 , bismuth 210 and polonium 210 in the atmosphere: accurate ratio measurement...in the ocean food web. The residence time of P in macrozooplankton was estimated to range from 40 to 60 days. A grazing rate of macrozooplankton of...cycles in the upper ocean remains a central issue for a com- 3 plete understanding of the biological pump and its effect on the deep ocean. There is

LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model v2.0.4

NASA Astrophysics Data System (ADS)

Zeebe, R. E.

2012-01-01

The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. LOSCAR's configuration of ocean geometry is flexible and allows for easy switching between modern and paleo-versions. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

Spin-Up and Tuning of the Global Carbon Cycle Model Inside the GISS ModelE2 GCM

NASA Technical Reports Server (NTRS)

Aleinov, Igor; Kiang, Nancy Y.; Romanou, Anastasia

2015-01-01

Planetary carbon cycle involves multiple phenomena, acting at variety of temporal and spacial scales. The typical times range from minutes for leaf stomata physiology to centuries for passive soil carbon pools and deep ocean layers. So, finding a satisfactory equilibrium state becomes a challenging and computationally expensive task. Here we present the spin-up processes for different configurations of the GISS Carbon Cycle model from the model forced with MODIS observed Leaf Area Index (LAI) and prescribed ocean to the prognostic LAI and to the model fully coupled to the dynamic ocean and ocean biology. We investigate the time it takes the model to reach the equilibrium and discuss the ways to speed up this process. NASA Goddard Institute for Space Studies General Circulation Model (GISS ModelE2) is currently equipped with all major algorithms necessary for the simulation of the Global Carbon Cycle. The terrestrial part is presented by Ent Terrestrial Biosphere Model (Ent TBM), which includes leaf biophysics, prognostic phenology and soil biogeochemistry module (based on Carnegie-Ames-Stanford model). The ocean part is based on the NASA Ocean Biogeochemistry Model (NOBM). The transport of atmospheric CO2 is performed by the atmospheric part of ModelE2, which employs quadratic upstream algorithm for this purpose.

Assimilating Satellite SST Observations into a Diurnal Cycle Model

NASA Astrophysics Data System (ADS)

Pimentel, S.; Haines, K.; Nichols, N. K.

2006-12-01

The wealth of satellite sea surface temperature (SST) data now available opens the possibility of large improvements in SST estimation. However the use of such data is not straight forward; a major difficulty in assimilating satellite observations is that they represent a near surface temperature, whereas in ocean models the top level represents the temperature at a greater depth. During the day, under favourable conditions of clear skies and calm winds, the near surface temperature is often seen to have a diurnal cycle that is picked up in satellite observations. Current ocean models do not have the vertical or temporal resolution to adequately represent this daytime warming. The usual approach is to discard daytime observations as they are considered diurnally `corrupted'. A new assimilation technique is developed here that assimilates observations into a diurnal cycle model. The diurnal cycle of SSTs are modelled using a 1-D mixed layer model with fine near surface resolution and 6 hourly forcing from NWP analyses. The accuracy of the SST estimates are hampered by uncertainties in the forcing data. The extent of diurnal SST warming at a particular location and time is predominately governed by a non-linear response to cloud cover and sea surface wind speeds which greatly affect the air-sea fluxes. The method proposed here combines infrared and microwave SST satellite observations in order to derive corrections to the cloud cover and wind speed values over the day. By adjusting the forcing, SST estimation and air-sea fluxes should be improved and are at least more consistent with each other. This new technique for assimilating SST data can be considered a tool for producing more accurate diurnal warming estimates.

pyhector: A Python interface for the simple climate model Hector

DOE Office of Scientific and Technical Information (OSTI.GOV)

N Willner, Sven; Hartin, Corinne; Gieseke, Robert

2017-04-01

Pyhector is a Python interface for the simple climate model Hector (Hartin et al. 2015) developed in C++. Simple climate models like Hector can, for instance, be used in the analysis of scenarios within integrated assessment models like GCAM1, in the emulation of complex climate models, and in uncertainty analyses. Hector is an open-source, object oriented, simple global climate carbon cycle model. Its carbon cycle consists of a one pool atmosphere, three terrestrial pools which can be broken down into finer biomes or regions, and four carbon pools in the ocean component. The terrestrial carbon cycle includes primary production andmore » respiration fluxes. The ocean carbon cycle circulates carbon via a simplified thermohaline circulation, calculating air-sea fluxes as well as the marine carbonate system (Hartin et al. 2016). The model input is time series of greenhouse gas emissions; as example scenarios for these the Pyhector package contains the Representative Concentration Pathways (RCPs)2. These were developed to cover the range of baseline and mitigation emissions scenarios and are widely used in climate change research and model intercomparison projects. Using DataFrames from the Python library Pandas (McKinney 2010) as a data structure for the scenarios simplifies generating and adapting scenarios. Other parameters of the Hector model can easily be modified when running the model. Pyhector can be installed using pip from the Python Package Index.3 Source code and issue tracker are available in Pyhector's GitHub repository4. Documentation is provided through Readthedocs5. Usage examples are also contained in the repository as a Jupyter Notebook (Pérez and Granger 2007; Kluyver et al. 2016). Courtesy of the Mybinder project6, the example Notebook can also be executed and modified without installing Pyhector locally.« less

Facies characterization and sequential evolution of an ancient offshore dunefield in a semi-enclosed sea: Neuquén Basin, Argentina

NASA Astrophysics Data System (ADS)

Veiga, Gonzalo D.; Schwarz, Ernesto

2017-08-01

This study analyses a 30-m-thick, sand-dominated succession intercalated between offshore mudstones in the Lower Cretaceous record of the Neuquén Basin, Argentina, defining facies associated with unidirectional currents as sand dunes (simple and compound), rippled sand sheets and heterolithic sheets. These facies associations are related to the development of an offshore, forward-accreting dunefield developed as a response to the onset of a tidal-transport system. The reported stratigraphic record results from the combination of the gradual downcurrent decrease of the current speed together with the long-term climbing of the entire system. Maximum amplification of the tidal effect associated with incoming oceanic tides to this epicontinental sea would develop at the time of more efficient connection between the basin and the open ocean. Thus, the onset of the offshore tidal system approximately corresponds to the time of maximum flooding conditions (or immediately after). The short-term evolution of the tidal-transport system is more complex and characterized by the vertical stacking of small-scale cycles defined by the alternation of episodes of construction and destruction of the dunefield. The development of these cycles could be the response to changes in tidal current speed and transport capacity.

Strangelove Ocean and Deposition of Unusual Shallow-Water Carbonates After the End-Permian Mass Extinction

NASA Technical Reports Server (NTRS)

Rampino, Michael R.; Caldeira, Ken

2003-01-01

The severe mass extinction of marine and terrestrial organisms at the end of the Permian Period (approx. 251 Ma) was accompanied by a rapid negative excursion of approx. 3 to 4 per mil in the carbon-isotope ratio of the global surface oceans and atmosphere that persisted for some 500,000 into the Early Triassic. Simulations with an ocean-atmosphere/carbon-cycle model suggest that the isotope excursion can be explained by collapse of ocean primary productivity (a Strangelove Ocean) and changes in the delivery and cycling of carbon in the ocean and on land. Model results also suggest that perturbations of the global carbon cycle resulting from the extinctions led to short-term fluctuations in atmospheric pCO2 and ocean carbonate deposition, and to a long-term (>1 Ma) decrease in sedimentary burial of organic carbon in the Triassic. Deposition of calcium carbonate is a major sink of river-derived ocean alkalinity and for CO2 from the ocean/atmosphere system. The end of the Permian was marked by extinction of most calcium carbonate secreting organisms. Therefore, the reduction of carbonate accumulation made the oceans vulnerable to a build-up of alkalinity and related fluctuations in atmospheric CO2. Our model results suggest that an increase in ocean carbonate-ion concentration should cause increased carbonate accumulation rates in shallow-water settings. After the end-Permian extinctions, early Triassic shallow-water sediments show an abundance of abiogenic and microbial carbonates that removed CaCO3 from the ocean and may have prevented a full 'ocean-alkalinity crisis' from developing.

Drake passage and central american seaway controls on the distribution of the oceanic carbon reservoir

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fyke, Jeremy G.; D'Orgeville, Marc; Weaver, Andrew J.

2015-05-01

A coupled carbon/climate model is used to explore the impact of Drake Passage opening and Central American Seaway closure on the distribution of carbon in the global oceans. We find that gateway evolution likely played an important role in setting the modern day distribution of oceanic dissolved inorganic carbon (DIC), which is currently characterized by relatively low concentrations in the Atlantic ocean, and high concentrations in the Southern, Indian, and Pacific oceans. In agreement with previous studies, we find a closed Drake Passage in the presence of an open Central American Seaway results in suppressed Atlantic meridional overturning and enhancedmore » southern hemispheric deep convection. Opening of the Drake Passage triggers Antarctic Circumpolar Current flow and a weak Atlantic meridional overturning circulation (AMOC). Subsequent Central American Seaway closure reinforces the AMOC while also stagnating equatorial Pacific subsurface waters. These gateway-derived oceanographic changes are reflected in large shifts to the global distribution of DIC. An initially closed Drake Passage results in high DIC concentrations in the Atlantic and Arctic oceans, and lower DIC concentrations in the Pacific/Indian/Southern oceans. Opening Drake Passage reverses this gradient by lowering mid-depth Atlantic and Arctic DIC concentrations and raising deep Pacific/Indian/Southern Ocean DIC concentrations. Central American Seaway closure further reinforces this trend through additional Atlantic mid-depth DIC decreases, as well as Pacific mid-depth DIC concentration increases, with the net effect being a transition to a modern distribution of oceanic DIC.« less

Antarctic glaciation caused ocean circulation changes at the Eocene-Oligocene transition

NASA Astrophysics Data System (ADS)

Goldner, A.; Herold, N.; Huber, M.

2014-07-01

Two main hypotheses compete to explain global cooling and the abrupt growth of the Antarctic ice sheet across the Eocene-Oligocene transition about 34 million years ago: thermal isolation of Antarctica due to southern ocean gateway opening, and declining atmospheric CO2 (refs 5, 6). Increases in ocean thermal stratification and circulation in proxies across the Eocene-Oligocene transition have been interpreted as a unique signature of gateway opening, but at present both mechanisms remain possible. Here, using a coupled ocean-atmosphere model, we show that the rise of Antarctic glaciation, rather than altered palaeogeography, is best able to explain the observed oceanographic changes. We find that growth of the Antarctic ice sheet caused enhanced northward transport of Antarctic intermediate water and invigorated the formation of Antarctic bottom water, fundamentally reorganizing ocean circulation. Conversely, gateway openings had much less impact on ocean thermal stratification and circulation. Our results support available evidence that CO2 drawdown--not gateway opening--caused Antarctic ice sheet growth, and further show that these feedbacks in turn altered ocean circulation. The precise timing and rate of glaciation, and thus its impacts on ocean circulation, reflect the balance between potentially positive feedbacks (increases in sea ice extent and enhanced primary productivity) and negative feedbacks (stronger southward heat transport and localized high-latitude warming). The Antarctic ice sheet had a complex, dynamic role in ocean circulation and heat fluxes during its initiation, and these processes are likely to operate in the future.

Antarctic glaciation caused ocean circulation changes at the Eocene-Oligocene transition.

PubMed

Goldner, A; Herold, N; Huber, M

2014-07-31

Two main hypotheses compete to explain global cooling and the abrupt growth of the Antarctic ice sheet across the Eocene-Oligocene transition about 34 million years ago: thermal isolation of Antarctica due to southern ocean gateway opening, and declining atmospheric CO2 (refs 5, 6). Increases in ocean thermal stratification and circulation in proxies across the Eocene-Oligocene transition have been interpreted as a unique signature of gateway opening, but at present both mechanisms remain possible. Here, using a coupled ocean-atmosphere model, we show that the rise of Antarctic glaciation, rather than altered palaeogeography, is best able to explain the observed oceanographic changes. We find that growth of the Antarctic ice sheet caused enhanced northward transport of Antarctic intermediate water and invigorated the formation of Antarctic bottom water, fundamentally reorganizing ocean circulation. Conversely, gateway openings had much less impact on ocean thermal stratification and circulation. Our results support available evidence that CO2 drawdown--not gateway opening--caused Antarctic ice sheet growth, and further show that these feedbacks in turn altered ocean circulation. The precise timing and rate of glaciation, and thus its impacts on ocean circulation, reflect the balance between potentially positive feedbacks (increases in sea ice extent and enhanced primary productivity) and negative feedbacks (stronger southward heat transport and localized high-latitude warming). The Antarctic ice sheet had a complex, dynamic role in ocean circulation and heat fluxes during its initiation, and these processes are likely to operate in the future.

78 FR 69395 - Meeting of the Ocean Research Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-19

...: Department of the Navy, DoD. ACTION: Notice of Open Meeting. SUMMARY: The Ocean Research Advisory Panel will hold a regularly scheduled meeting. The meeting will be open to the public. Members of the public who..., Arlington, VA 22203- 1995, telephone 703-696-4532. SUPPLEMENTARY INFORMATION: This notice of open meeting is...

78 FR 57371 - Meeting of the Ocean Research Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-18

...: Department of the Navy, DoD. ACTION: Notice of open meeting. SUMMARY: The Ocean Research Advisory Panel will hold a regularly scheduled meeting. The meeting will be open to the public. DATES: The meeting will be..., VA 22203- 1995, telephone 703-696-4532. SUPPLEMENTARY INFORMATION: This notice of open meeting is...

How Reducing was the Late Devonian Ocean? The Role of Extensive Expansion of Anoxia in Marine Biogeochemical Cycles of Redox Sensitive Metals.

NASA Astrophysics Data System (ADS)

Sahoo, S. K.; Jin, H.

2017-12-01

The evolution of Earth's biogeochemical cycles is intimately linked to the oxygenation of the oceans and atmosphere. The Late Devonian is no exception as its characterized with mass extinction and severe euxinia. Here we use concentrations of Molybdenum (Mo), Vanadium (V), Uranium (U) and Chromium (Cr) in organic rich black shales from the Lower Bakken Formation of the Williston Basin, to explore the relationship between extensive anoxia vs. euxinia and it's relation with massive release of oxygen in the ocean atmosphere system. XRF data from 4 core across the basin shows that modern ocean style Mo, U and Cr enrichments are observed throughout the Lower Bakken Formation, yet V is not enriched until later part of the formation. Given the coupling between redox-sensitive-trace element cycles and ocean redox, various models for Late Devonian ocean chemistry imply different effects on the biogeochemical cycling of major and trace nutrients. Here, we examine the differing redox behavior of molybdenum and vanadium under an extreme anoxia and relatively low extent of euxinia. The model suggests that Late Devonian was perhaps extensively anoxic- 40-50% compared to modern seafloor area, and a very little euxinia. Mo enrichments extend up to 500 p.p.m. throughout the section, representative of a modern reducing ocean. However, coeval low V enrichments only support towards anoxia, where anoxia is a source of V, and a sink for Mo. Our model suggests that the oceanic V reservoir is extremely sensitive to perturbations in the extent of anoxic condition, particularly during post glacial times.

Ocean Bottom Pressure Seasonal Cycles and Decadal Trends from GRACE Release-05: Ocean Circulation Implications

NASA Astrophysics Data System (ADS)

Johnson, G. C.; Chambers, D. P.

2013-12-01

Ocean mass variations are important for diagnosing sea level budgets, the hydrological cycle and global energy budget, as well as ocean circulation variability. Here seasonal cycles and decadal trends of ocean mass from January 2003 to December 2012, both global and regional, are analyzed using GRACE Release 05 data. The trend of global flux of mass into the ocean approaches 2 cm decade-1 in equivalent sea level rise. Regional trends are of similar magnitude, with the North Pacific, South Atlantic, and South Indian oceans generally gaining mass and other regions losing mass. These trends suggest a spin-down of the North Pacific western boundary current extension and the Antarctic Circumpolar Current in the South Atlantic and South Indian oceans. The global average seasonal cycle of ocean mass is about 1 cm in amplitude, with a maximum in early October and volume fluxes in and out of the ocean reaching 0.5 Sv (1 Sv = 1 × 106 m3 s-1) when integrated over the area analyzed here. Regional patterns of seasonal ocean mass change have typical amplitudes of 1-4 cm, and include maxima in the subtropics and minima in the subpolar regions in hemispheric winters. The subtropical mass gains and subpolar mass losses in the winter spin up both subtropical and subpolar gyres, hence the western boundary current extensions. Seasonal variations in these currents are order 10 Sv, but since the associated depth-averaged current variations are only order 0.1 cm s-1, they would be difficult to detect using in situ oceanographic instruments. a) Amplitude (colors, in cm) and b) phase (colors, in months of the year) of an annual harmonic fit to monthly GRACE Release 05 CSR 500 km smoothed maps (concurrently with a trend and the semiannual harmonic). The 97.5% confidence interval for difference from zero is also indicated (solid black line). Data within 300 km of coastlines are not considered.

Deoxygenation alters bacterial diversity and community composition in the ocean's largest oxygen minimum zone.

PubMed

Beman, J Michael; Carolan, Molly T

2013-01-01

Oceanic oxygen minimum zones (OMZs) have a central role in biogeochemical cycles and are expanding as a consequence of climate change, yet how deoxygenation will affect the microbial communities that control these cycles is unclear. Here we sample across dissolved oxygen gradients in the oceans' largest OMZ and show that bacterial richness displays a unimodal pattern with decreasing dissolved oxygen, reaching maximum values on the edge of the OMZ and decreasing within it. Rare groups on the OMZ margin are abundant at lower dissolved oxygen concentrations, including sulphur-cycling Chromatiales, for which 16S rRNA was amplified from extracted RNA. Microbial species distribution models accurately replicate community patterns based on multivariate environmental data, demonstrate likely changes in distributions and diversity in the eastern tropical North Pacific Ocean, and highlight the sensitivity of key bacterial groups to deoxygenation. Through these mechanisms, OMZ expansion may alter microbial composition, competition, diversity and function, all of which have implications for biogeochemical cycling in OMZs.

Dissolved Platinum Concentrations in Coastal Seawater: Boso to Sanriku Areas, Japan.

PubMed

Mashio, Asami Suzuki; Obata, Hajime; Gamo, Toshitaka

2017-08-01

Platinum, one of the rarest elements in the earth's crust, is now widely used in a range of products, such as catalytic converters in automobiles and anticancer drugs. Increasing use and dispersal of platinum has the potential to affect aquatic environments. Platinum concentrations in open ocean seawater have been found to be very low (approximately 0.2 pmol/L); however, Pt distributions and biogeochemical cycles in coastal areas are unknown. In this study, we investigated Pt concentrations in coastal waters between the Boso and Sanriku areas, Japan, after the 2011 tsunami. We determined sub-picomolar levels of dissolved Pt using isotope-dilution Inductively coupled plasma mass spectrometry after column preconcentration with an anion exchange resin. Dissolved Pt concentrations were found to be in the range 0.20-1.5 pmol/L, with the highest concentration in bottom water of the Boso coastal area, and at stations close to Tokyo Bay. Assuming thermodynamical equilibrium, Pt was determined to be present in the form PtCl 5 (OH) 2- , even in low-oxygen coastal waters. Vertical profiles indicated Pt levels increased toward seafloors near coastal stations and were similar to those of the open ocean at trench stations. High concentrations of dissolved Pt are thought to be derived from coastal sediments.

Horizontal variability of the marine boundary layer structure upwind of San Nicolas Island during FIRE, 1987

NASA Technical Reports Server (NTRS)

Jensen, Douglas R.

1990-01-01

During the months of June and July 1987, the Marine Stratocumulus Intensive Field Observation Experiment of First ISCCP Regional Experiment (FIRE) was conducted in the Southern California offshore area in the vicinity of San Nicolas Island (SNI). The Naval Ocean Systems Center (NOSC) airborne platform was utilized during FIRE to investigate the upwind low level horizontal variability of the marine boundary layer structure to determine the representativeness of SNI-based measurements to upwind open ocean conditions. The NOSC airborne meteorological platform made three flights during FIRE, two during clear sky conditions (19 and 23 July), and one during two stratus conditions (15 July). The boundary layer structure variations associated with the stratus clouds of 15 July 1987 are discussed. Profiles of air temperature (AT) and relative humidity (RH) taken 'at' and 'upwind' of SNI do show differences between the so-called open ocean conditions and those taken near the island. However, the observed difference cannot be uniquely identified to island effects, especially since the upwind fluctuations of AT and RH bound the SNI measurements. Total optical depths measures at SNI do not appear to be greatly affected by any surface based aerosol effects created by the island and could therefore realistically represent open ocean conditions. However, if one were to use the SNI aerosol measurements to predict ship to ship EO propagation conditions, significant errors could be introduced due to the increased number of surface aerosols observed near SNI which may not be, and were not, characteristic of open ocean conditions. Sea surface temperature measurements taken at the island will not, in general, represent those upwind open ocean conditions. Also, since CTT's varied appreciably along the upwind radials, measurements of CTT over the island may not be representative of actual open ocean CTT's.

Global surface-based cloud observation for ISCCP

NASA Technical Reports Server (NTRS)

1994-01-01

Visual observations of cloud cover are hindered at night due to inadequate illumination of the clouds. This usually leads to an underestimation of the average cloud cover at night, especially for the amounts of middle and high clouds, in climatologies on surface observations. The diurnal cycles of cloud amounts, if based on all the surface observations, are therefore in error, but they can be obtained more accurately if the nighttime observations are screened to select those made under sufficient moonlight. Ten years of nighttime weather observations from the northern hemisphere in December were classified according to the illuminance of moonlight or twilight on the cloud tops, and a threshold level of illuminance was determined, above which the clouds are apparently detected adequately. This threshold corresponds to light from a full moon at an elevation angle of 6 degrees or from a partial moon at higher elevation, or twilight from the sun less than 9 degrees below the horizon. It permits the use of about 38% of the observations made with the sun below the horizon. The computed diurnal cycles of total cloud cover are altered considerably when this moonlight criterion is imposed. Maximum cloud cover over much of the ocean is now found to be at night or in the morning, whereas computations obtained without benefit of the moonlight criterion, as in our published atlases, showed the time of maximum to be noon or early afternoon in many regions. Cloud cover is greater at night than during the day over the open oceans far from the continents, particularly in summer. However, near noon maxima are still evident in the coastal regions, so that the global annual average oceanic cloud cover is still slightly greater during the day than at night, by 0.3%. Over land, where daytime maxima are still obtained but with reduced amplitude, average cloud cover is 3.3% greater during the daytime. The diurnal cycles of total cloud cover we obtain are compared with those of ISCCP for a few regions; they are generally in better agreement if the moonlight criterion is imposed on the surface observations. Using the moonlight criterion, we have analyzed ten years (1982-1991) of surface weather observations over land and ocean, worldwide, for total cloud cover and for the frequency of occurrence of clear sky, fog and precipitation The global average cloud cover (average of day and night) is about 2% higher if we impose the moonlight criterion than if we use all observations. The difference is greater in winter than in summer, because of the fewer hours of darkness in the summer. The amplitude of the annual cycle of total cloud cover over the Arctic Ocean and at the South Pole is diminished by a few percent when the moonlight criterion is imposed. The average cloud cover for 1982-1991 is found to be 55% for northern hemisphere land, 53% for southern hemisphere land, 66% for northern hemisphere ocean, and 70% for southern hemisphere ocean, giving a global average of 64%. The global average for daytime is 64.6% for nighttime 63.3%.

The cycling of iron, zinc and cadmium in the North East Pacific Ocean - Insights from stable isotopes

NASA Astrophysics Data System (ADS)

Conway, Tim M.; John, Seth G.

2015-09-01

Dissolved stable isotope ratios of the transition metals provide useful information, both for understanding the cycling of these bioactive trace elements through the oceans, and tracing their marine sources and sinks. Here, we present seawater dissolved Fe, Zn and Cd concentration and stable isotope ratio (δ56Fe, δ66Zn, and δ114Cd) profiles from two stations in the Pacific Ocean, the SAFe Station (30°N 140°W) in the subtropical North East Pacific from the GEOTRACES IC2 cruise, and the marginal San Pedro Basin (33.8°N 118.4°W) within the South California Bight. These data represent, to our knowledge, the first full-water column profiles for δ66Zn and δ56Fe from the open-ocean North Pacific, and the first observations of dissolved δ66Zn and δ114Cd in a low-oxygen marginal basin. At the SAFe station, δ56Fe is isotopically lighter throughout the water column (-0.6 to +0.1‰, relative to IRRM-014) compared to the North Atlantic, suggesting significant differences in Fe sources or Fe cycling between these two ocean basins. A broad minimum in δ56Fe associated with the North Pacific oxygen minimum zone (OMZ; <75 μmol kg-1 dissolved oxygen; ∼550-2000 m depth) is consistent with reductive sediments along the California margin being an important source of dissolved Fe to the North Pacific. Other processes which may influence δ56Fe at SAFe include biological cycling in the upper ocean, and input of Fe from hydrothermal vents and oxic sediments below the OMZ. Zn and Cd concentration profiles at both stations broadly match the distribution of the macronutrients silicate and phosphate, respectively. At SAFe, δ114Cd increases towards the surface, reflecting the biological preference for assimilation of lighter Cd isotopes, while negative Cd∗ (-0.12) associated with low oxygen waters supports the recently proposed hypothesis of water-column CdS precipitation. In contrast to δ114Cd, δ66Zn at SAFe decreases towards the surface ocean, perhaps due to scavenging of isotopically heavy Zn, while at intermediate depths δ66Zn provides further evidence of a mid-depth dissolved δ66Zn maximum. We suggest this may be a global feature of Zn biogeochemistry related to either regeneration of heavy adsorbed Zn, or to ZnS formation and removal within the water column. Data from San Pedro shows that anoxic sediments can be a source of isotopically light Zn to the water column (δ66Zn of ∼-0.3‰ relative to JMC Lyon), though evidence of this signal is not observed being transported to SAFe. Within North Pacific Intermediate Water at SAFe (NPIW; ∼500 m) elevated Cd∗ and Zn∗ and a focused minimum in δ56Fe suggest possible transport of Fe, Zn, and Cd over thousands of km from subpolar waters, meaning that NPIW may have a strong influence on the subsurface distribution of trace metals throughout the North Pacific.

Optimizing and Enhancing the Integrated Atlantic Ocean Observing System to enhance the societal, scientific and economic benefit

NASA Astrophysics Data System (ADS)

Reitz, Anja; Karstensen, Johannes; Visbeck, Martin; AtlantOS Consortium, the

2017-04-01

Atlantic Ocean observation is currently undertaken through loosely-coordinated, in-situ observing networks, satellite observations and data management arrangements of heterogeneous international, national and regional design to support science and a wide range of information products. Thus there is tremendous opportunity to develop the systems towards a fully integrated Atlantic Ocean Observing System consistent with the recently developed 'Framework of Ocean Observing'. The vision of AtlantOS is to improve and innovate Atlantic Ocean observing by establishing an international, more sustainable, more efficient, more integrated, and fit-for-purpose system. Hence, the EU Horizon 2020 project AtlantOS with its 62 partners from 18 countries (European and international) and several members will have a long-lasting and sustainable contribution to the societal, economic and scientific benefit by supporting the full cycle of the integrated ocean observation value chain from requirements via data gathering and observation, product generation, information, prediction, dissemination and stakeholder dialogue towards information and product provision. The benefits will be delivered by improving the value for money, extent, completeness, quality and ease of access to Atlantic Ocean data required by industries, product supplying agencies, scientist and citizens. The overarching target of the AtlantOS initiative is to deliver an advanced framework for the development of an integrated Atlantic Ocean Observing System that goes beyond the state-of -the-art, and leaves a legacy of sustainability after the life of the project. The legacy will derive from the following aims: i) to improve international collaboration in the design, implementation and benefit sharing of ocean observing, ii) to promote engagement and innovation in all aspects of ocean observing, iii) to facilitate free and open access to ocean data and information, iv) to enable and disseminate methods of achieving quality and authority of ocean information, v) to strengthen the Global Ocean Observing System (GOOS), the Blue Planet initiative within the Group on Earth Observations (GEO) and to sustain the Copernicus Marine Environment Monitoring Service and its applications and vi) to contribute to the aims of the Galway Statement on Atlantic Ocean Cooperation.

Upper Ocean Measurements from Profiling Floats in the Arabian Sea During NASCar

DTIC Science & Technology

2015-09-30

top-level goals] OBJECTIVES The work proposed here is designed to examine the seasonal evolution of the upper ocean in the northern Arabian...Sea over several seasonal cycles, with the specific objectives of (1) Documenting the spatial variations in the seasonal cycle of the upper ocean...circulation of the Arabian Sea and the seasonal and spatial evolution of the surface mixed layer, and would be used in conjunction with HYCOM model

Accelerated warming of the Southern Ocean and its impacts on the hydrological cycle and sea ice.

PubMed

Liu, Jiping; Curry, Judith A

2010-08-24

The observed sea surface temperature in the Southern Ocean shows a substantial warming trend for the second half of the 20th century. Associated with the warming, there has been an enhanced atmospheric hydrological cycle in the Southern Ocean that results in an increase of the Antarctic sea ice for the past three decades through the reduced upward ocean heat transport and increased snowfall. The simulated sea surface temperature variability from two global coupled climate models for the second half of the 20th century is dominated by natural internal variability associated with the Antarctic Oscillation, suggesting that the models' internal variability is too strong, leading to a response to anthropogenic forcing that is too weak. With increased loading of greenhouse gases in the atmosphere through the 21st century, the models show an accelerated warming in the Southern Ocean, and indicate that anthropogenic forcing exceeds natural internal variability. The increased heating from below (ocean) and above (atmosphere) and increased liquid precipitation associated with the enhanced hydrological cycle results in a projected decline of the Antarctic sea ice.

Modern Deep-sea Sponges as Recorders of Bottom Water Silicon Isotopes

NASA Astrophysics Data System (ADS)

Hendry, K. R.; Georg, R. B.; Rickaby, R. E.; Robinson, L. F.; Halliday, A. N.

2008-12-01

Major zones of opal accumulation in the world oceans have experienced geographical shifts during the Cenozoic coincident with times of transition in oceanic circulation and climate. The global marine silica cycle is likely to respond to various large-scale changes including the distillation of Si and other nutrients in ocean basins; weathering and continental inputs; and biological productivity in surface waters. These processes could potentially be distinguished by their impact on the isotopic composition of dissolved silica in the world oceans. Although diatoms dominate uptake of silica in surface waters, box-modelling (de la Rocha and Bickle, 2005) suggests that sponges spicules have a greater potential to reflect whole ocean changes in the silica cycle, by recording deep-water silicon isotopes. Here, we introduce a new calibration study of modern deep- sea sponges collected on a transect cruise across the Drake Passage, in the Southern Ocean, from a range of depths and seawater silicic acid concentrations. Sponges were collected by benthic trawling, and dried immediately. The spicules were later isolated from cellular material and cleaned for surface contaminants, before dissolution and analysis by NuPlasma HR MC-ICP-MS in medium resolution mode. We discuss our preliminary data, the extent to which inter and intraspecies variations reflect environmental conditions, and the implications for palaeoreconstructions of the marine silicon cycle. de la Rocha, C. and M. Bickle (2005). Sensitivity of silicon isotopes to whole-ocean changes in the silica cycle. Marine Geology 217, 267-282.

Report nixes Geritol fix for global warming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, L.

1991-09-27

Several years ago John Martin of the Moss Landing Marine Laboratory in California suggested a quick fix to the greenhouse problem: dump iron into the Southern Ocean near Antarctica. That, he said, would trigger a massive bloom of the ocean's microscopic plants, which in turn would suck carbon dioxide out of the atmosphere and help reduce global warming. His idea ignited a firestorm of controversy that rages on today. While the idea quickly won supporters - including some prominent members of the National Academy of Sciences - much of the oceanographic community was incensed, arguing that you don't tinker withmore » a perfectly health ecosystem to clean up humanity's mess. Now the American Society of Limnology and Oceanography (ASLO) has a report that represents the views of much of the oceanographic community. In the report, released in late summer, ASLO trounces the idea of fertilizing the oceans with iron as a greenhouse fix, as expected. But in an unexpected twist, the society endorses a small-scale experiment in which iron would be added to the open ocean. The idea isn't to engineer the oceans, but to test the hypothesis that might answer one of the longstanding puzzles in biological oceanography: why do the phytoplankton of the Southern Ocean, as well as those in parts of the subarctic and equatorial Pacific, grow so poorly, even though the waters are rich in nutrients such as phosphorus and nitrogen The answer could shed light not only on how the food web operates, but on the global carbon cycle as well.« less

Mercury in the atmosphere, snow and melt water ponds in the North Atlantic Ocean during Arctic summer.

PubMed

Aspmo, Katrine; Temme, Christian; Berg, Torunn; Ferrari, Christophe; Gauchard, L Pierre-Alexis; Fain, Xavier; Wibetoe, Grethe

2006-07-01

Atmospheric mercury speciation measurements were performed during a 10 week Arctic summer expedition in the North Atlantic Ocean onboard the German research vessel RV Polarstern between June 15 and August 29, 2004. This expedition covered large areas of the North Atlantic and Arctic Oceans between latitudes 54 degrees N and 85 degrees N and longitudes 16 degrees W and 16 degrees E. Gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and mercury associated with particles (Hg-P) were measured during this study. In addition, total mercury in surface snow and meltwater ponds located on sea ice floes was measured. GEM showed a homogeneous distribution over the open North Atlantic Ocean (median 1.53 +/- 0.12 ng/m3), which is in contrast to the higher concentrations of GEM observed over sea ice (median 1.82 +/- 0.24 ng/m3). It is hypothesized that this results from either (re-) emission of mercury contained in snow and ice surfaces that was previously deposited during atmospheric mercury depletion events (AMDE) in the spring or evasion from the ocean due to increased reduction potential at high latitudes during Arctic summer. Measured concentrations of total mercury in surface snow and meltwater ponds were low (all samples <10 ng/L), indicating that marginal accumulation of mercury occurs in these environmental compartments. Results also reveal low concentrations of RGM and Hg-P without a significant diurnal variability. These results indicate that the production and deposition of these reactive mercury species do not significantly contribute to the atmospheric mercury cycle in the North Atlantic Ocean during the Arctic summer.

Modest net autotrophy in the oligotrophic ocean

NASA Astrophysics Data System (ADS)

Letscher, Robert T.; Moore, J. Keith

2017-04-01

The metabolic state of the oligotrophic subtropical ocean has long been debated. Net community production (NCP) represents the balance of autotrophic carbon fixation with heterotrophic respiration. Many in vitro NCP estimates based on oxygen incubation methods and the corresponding scaling relationships used to predict the ecosystem metabolic balance have suggested the ocean gyres to be net heterotrophic; however, all in situ NCP methods find net autotrophy. Reconciling net heterotrophy requires significant allochthonous inputs of organic carbon to the oligotrophic gyres to sustain a preponderance of respiration over in situ production. Here we use the first global ecosystem-ocean circulation model that contains representation of the three allochthonous carbon sources to the open ocean, to show that the five oligotrophic gyres exhibit modest net autotrophy throughout the seasonal cycle. Annually integrated rates of NCP vary in the range 1.5-2.2 mol O2 m-2 yr-1 across the five gyre systems; however, seasonal NCP rates are as low as 1 ± 0.5 mmol O2 m-2 d-1 for the North Atlantic. Volumetric NCP rates are heterotrophic below the 10% light level; however, they become net autotrophic when integrated over the euphotic zone. Observational uncertainties when measuring these modest autotrophic NCP rates as well as the metabolic diversity encountered across space and time complicate the scaling up of in vitro measurements to the ecosystem scale and may partially explain the previous reports of net heterotrophy. The oligotrophic ocean is autotrophic at present; however, it could shift toward seasonal heterotrophy in the future as rising temperatures stimulate respiration.

Year-Round Pack Ice in the Weddell Sea, Antarctica: Response and Sensitivity to Atmospheric and Oceanic Forcing

NASA Technical Reports Server (NTRS)

Geiger, Cathleen A.; Ackley, Stephen F.; Hibler, William D., III

1997-01-01

Using a dynamic-thermodynamic numerical sea-ice model, external oceanic and atmospheric forcings on sea ice in the Weddell Sea are examined to identify physical processes associated with the seasonal cycle of pack ice, and to identify further the parameters that coupled models need to consider in predicting the response of the pack ice to climate and ocean-circulation changes. In agreement with earlier studies, the primary influence on the winter ice-edge maximum extent is air temperature. Ocean heat flux has more impact on the minimum-ice-edge extent and in reducing pack-ice thickness, especially in the eastern-Weddell Sea. Low relative humidity enhances ice growth in thin ice and open-water regions, producing a more realistic ice edge along the coastal areas of the western-Weddell Sea where dry continental air has an impact. The modeled extent of the Weddell summer pack is equally sensitive to ocean heat flux and atmospheric relative humidity variations with the more dynamic responses being from the atmosphere. Since the atmospheric regime in the eastern Weddell is dominated by marine intrusions from lower latitudes, with high humidity already, it is unlikely that either the moisture trans- port could be further raised or that it could be significantly lowered because of its distance from the continent (the lower humidity source). Ocean heat-transport variability is shown to lead to overall ice thinning in the model response and is a known feature of the actual system, as evidenced by the occurrence of the Weddell Polynya in the mid 1970s.

El Nino-southern oscillation related fluctuations of the marine carbon cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winguth, A.M.E.; Heimann, M.; Kurz, K.D.

The yearly increase in global atmospheric carbon dioxide concentration is not constant, fluctuating around a mean growth rate. Some previous work has been done looking at the relationship of CO2 fluctuations with the El Nino-Southern Oscillation (ENSO) events in the Pacific. This paper describes the response of the three-dimensional ocean circulation model (Hamburg LSG) coupled on-line with a oceanic carbon cycle model (HAMOCC-3) to realistic wind and air temperature field anomalies. The focus is the marine carbon cycle and the interannual variations of carbon fluxes between ocean and atmosphere during the strong El Nino of 1982/83. 53 refs., 14 figs.

Warming up, turning sour, losing breath: ocean biogeochemistry under global change.

PubMed

Gruber, Nicolas

2011-05-28

In the coming decades and centuries, the ocean's biogeochemical cycles and ecosystems will become increasingly stressed by at least three independent factors. Rising temperatures, ocean acidification and ocean deoxygenation will cause substantial changes in the physical, chemical and biological environment, which will then affect the ocean's biogeochemical cycles and ecosystems in ways that we are only beginning to fathom. Ocean warming will not only affect organisms and biogeochemical cycles directly, but will also increase upper ocean stratification. The changes in the ocean's carbonate chemistry induced by the uptake of anthropogenic carbon dioxide (CO(2)) (i.e. ocean acidification) will probably affect many organisms and processes, although in ways that are currently not well understood. Ocean deoxygenation, i.e. the loss of dissolved oxygen (O(2)) from the ocean, is bound to occur in a warming and more stratified ocean, causing stress to macro-organisms that critically depend on sufficient levels of oxygen. These three stressors-warming, acidification and deoxygenation-will tend to operate globally, although with distinct regional differences. The impacts of ocean acidification tend to be strongest in the high latitudes, whereas the low-oxygen regions of the low latitudes are most vulnerable to ocean deoxygenation. Specific regions, such as the eastern boundary upwelling systems, will be strongly affected by all three stressors, making them potential hotspots for change. Of additional concern are synergistic effects, such as ocean acidification-induced changes in the type and magnitude of the organic matter exported to the ocean's interior, which then might cause substantial changes in the oxygen concentration there. Ocean warming, acidification and deoxygenation are essentially irreversible on centennial time scales, i.e. once these changes have occurred, it will take centuries for the ocean to recover. With the emission of CO(2) being the primary driver behind all three stressors, the primary mitigation strategy is to reduce these emissions. © 2011 The Royal Society

Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind-Wave Coupling

DTIC Science & Technology

2015-09-30

Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind- Wave Coupling Peter S. Guest (NPS Technical Contact) Naval...surface fluxes and ocean waves in coupled models in the Beaufort and Chukchi Seas. 2. Understand the physics of heat and mass transfer from the ocean...to the atmosphere. 3. Improve forecasting of waves on the open ocean and in the marginal ice zone. 2 OBJECTIVES 1. Quantifying the open-ocean

Enhanced open ocean storage of CO2 from shelf sea pumping.

PubMed

Thomas, Helmuth; Bozec, Yann; Elkalay, Khalid; de Baar, Hein J W

2004-05-14

Seasonal field observations show that the North Sea, a Northern European shelf sea, is highly efficient in pumping carbon dioxide from the atmosphere to the North Atlantic Ocean. The bottom topography-controlled stratification separates production and respiration processes in the North Sea, causing a carbon dioxide increase in the subsurface layer that is ultimately exported to the North Atlantic Ocean. Globally extrapolated, the net uptake of carbon dioxide by coastal and marginal seas is about 20% of the world ocean's uptake of anthropogenic carbon dioxide, thus enhancing substantially the open ocean carbon dioxide storage.

Vertical mercury distributions in the oceans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gill, G.A.; Fitzgerald, W.F.

1988-06-01

The vertical distribution of mercury (Hg) was determined at coastal and open ocean sites in the northwest Atlantic and Pacific Oceans. Reliable and diagnostic Hg distribution were obtained, permitting major processes governing the marine biogeochemistry of Hg to be identified. The northwest Atlantic near Bermuda showed surface water Hg concentrations near 4 pM, a maximum of 10 pM within the main thermocline, and concentrations less than or equal to surface water values below the depth of the maximum. The maximum appears to result from lateral transport of Hg enriched waters from higher latitudes. In the central North Pacific, surface watersmore » (to 940 m) were slightly elevated (1.9 {plus minus} 0.7 pM) compared to deeper waters (1.4 {plus minus} 0.4 pM), but on thermocline Hg maximum was observed. At similar depths, Hg concentrations near Bermuda were elevated compared to the central North Pacific Ocean. The authors hypothesize that the source of this Hg comes from diagenetic reactions in oxic margin sediments, releasing dissolved Hg to overlying water. Geochemical steady-state box modeling arguments predict a relatively short ({approximately}350 years) mean residence time for Hg in the oceans, demonstrating the reactive nature of Hg in seawater and precluding significant involvement in nutrient-type recycling. Mercury's distributional features and reactive nature suggest that interaction of Hg with settling particulate matter and margin sediments play important roles in regulating oceanic Hg concentrations. Oceanic Hg distributions are governed by an external cycling process, in which water column distributions reflect a rapid competition between the magnitude of the input source and the intensity of the (water column) removal process.« less

Comparisons between the characteristics of ichthyofaunas in nearshore waters of five estuaries with varying degrees of connectivity with the ocean

NASA Astrophysics Data System (ADS)

Hoeksema, S. D.; Chuwen, B. M.; Potter, I. C.

2009-10-01

The characteristics of the fish faunas in nearshore, shallow (<1.2 m) waters of the basins of estuaries along the same coastline, but which were open to the ocean for varying periods, have been determined and compared. The fish faunas of the permanently-open Oyster Harbour, the seasonally-open Broke, Irwin and Wilson inlets and the normally-closed Wellstead Estuary on the south coast of Western Australia were sampled by seine net seasonally for 2 years. Irrespective of the frequency and duration that the estuary mouth was open, the ichthyofauna of each estuary was numerically dominated by three atherinid species and three gobiid species (92.9-99.7%), each of which completes its life cycle within these estuaries. The ichthyofaunal compositions of each estuary differed significantly, however, from that of each other estuary. These differences were largely attributable to the relative abundances of the above six species varying between estuaries, which, in turn, reflected differences in such factors as estuary mouth status, macrophyte cover and salinity. For example, Favonigobius lateralis and Leptatherina presbyteroides, which are also represented by marine populations, were most abundant in the permanently-open estuary (Oyster Harbour), which, in terms of substrate and salinity, most closely resembled the nearshore marine environment. In contrast, Leptatherina wallacei made its greatest contribution in the only estuary to exhibit a protracted period of greatly reduced salinities, which is consistent with its distribution in permanently-open estuaries on the lower west coast of Australia, while Atherinosoma elongata and Pseudogobius olorum were particularly numerous in estuaries containing dense stands of the seagrass Ruppia megacarpa. Marine species made the greatest contribution to species richness in the permanently-open estuary and least in the normally-closed estuary. Species richness was greatest in summer and least in winter in each estuary, but differed markedly between years only in Wilson Inlet. Density of fishes was greatest in the most eutrophic estuary (Wellstead Estuary) and least in the most oligotrophic estuary (Broke Inlet) and only underwent marked seasonal variations in Wilson Inlet and Wellstead Estuary, in which densities fell to their minima in winter. Ichthyofaunal composition varied between years in the Broke and Wilson inlets and Wellstead Estuary, in which there was little or no connection with the ocean in one of those years. Species composition underwent progressive seasonal changes throughout the year in Wellstead Estuary, due to the abundance of certain species peaking at different times of the year.

Sensitivity of open-water ice growth and ice concentration evolution in a coupled atmosphere-ocean-sea ice model

NASA Astrophysics Data System (ADS)

Shi, Xiaoxu; Lohmann, Gerrit

2017-09-01

A coupled atmosphere-ocean-sea ice model is applied to investigate to what degree the area-thickness distribution of new ice formed in open water affects the ice and ocean properties. Two sensitivity experiments are performed which modify the horizontal-to-vertical aspect ratio of open-water ice growth. The resulting changes in the Arctic sea-ice concentration strongly affect the surface albedo, the ocean heat release to the atmosphere, and the sea-ice production. The changes are further amplified through a positive feedback mechanism among the Arctic sea ice, the Atlantic Meridional Overturning Circulation (AMOC), and the surface air temperature in the Arctic, as the Fram Strait sea ice import influences the freshwater budget in the North Atlantic Ocean. Anomalies in sea-ice transport lead to changes in sea surface properties of the North Atlantic and the strength of AMOC. For the Southern Ocean, the most pronounced change is a warming along the Antarctic Circumpolar Current (ACC), owing to the interhemispheric bipolar seasaw linked to AMOC weakening. Another insight of this study lies on the improvement of our climate model. The ocean component FESOM is a newly developed ocean-sea ice model with an unstructured mesh and multi-resolution. We find that the subpolar sea-ice boundary in the Northern Hemisphere can be improved by tuning the process of open-water ice growth, which strongly influences the sea ice concentration in the marginal ice zone, the North Atlantic circulation, salinity and Arctic sea ice volume. Since the distribution of new ice on open water relies on many uncertain parameters and the knowledge of the detailed processes is currently too crude, it is a challenge to implement the processes realistically into models. Based on our sensitivity experiments, we conclude a pronounced uncertainty related to open-water sea ice growth which could significantly affect the climate system sensitivity.

Seasonal controls of the short term variability of pCO2 at the Scotian Shelf

NASA Astrophysics Data System (ADS)

Thomas, H.; Craig, S.; Greenan, B. J. W.; Burt, W.; Herndl, G. J.; Higginson, S.; Salt, L.; Shadwick, E. H.; Urrego-Blanco, J.

2012-04-01

Much of the surface ocean carbon cycle variability can be attributed to the availability of sunlight, through processes such as heat fluxes or photosynthesis, which regulate the ocean carbon cycle over a wide range of time scales. The critical processes occurring on timescales of a day or less, however, have undergone few investigations, and most of those have been limited to a time span of several days to months, or exceptionally, for longer periods. Optical methods have helped to infer short-term biological variability, however lacking corresponding investigations of oceanic CO2 system. Here, we employ high-frequency CO2 system and optical observations covering the full seasonal cycle on the Scotian Shelf, Northwestern Atlantic Ocean, in order to unravel daily periodicity of the surface ocean carbon cycle and its effects on annual budgets. We show that significant daily periodicity occurs only if the water column is sufficiently stable as observed during seasonal warming. During that time biological CO2 drawdown, or net community production (NCP), is delayed for several hours relative to the daylight cycle due the daily build-up of essential Chlorophyll a, to cell physiology and to grazing effects, all restricting or hindering photosynthesis in the early morning hours. NCP collapses in summer by more than 90%, when the mixed layer depth reaches the seasonal minimum, which eventually makes the observed daily periodicity of the CO2 system vanish.

Accomplishments of Aquarius: NASA's first global Sea Surface Salinity Mission: a review of the technical findings to date

NASA Astrophysics Data System (ADS)

Sen, Amit

2014-10-01

Launched 10 June 2011, the NASA's Aquarius instrument onboard the Argentine built and managed Satélite de Aplicaciones Científicas (SAC-D) has been tirelessly observing the open oceans, confirming and adding new knowledge to the not so vast measured records of our Earth's global oceans. This paper reviews the data collected over the last 3 years, it's findings, challenges and future work that is at hand for the sleepless oceanographers, hydrologists and climate scientists. Although routine data is being collected, a snapshot is presented from almost 3-years of flawless operations showing new discoveries and possibilities of lot more in the future. Repetitive calibration and validation of measurements from Aquarius continue together with comparison of the data to the existing array of Argo temperature/salinity profiling floats, measurements from the recent Salinity Processes in the Upper Ocean Regional Study (SPURS) in-situ experiment and research, and to the data collected from the European Soil Moisture Ocean Salinity (SMOS) mission. This all aids in the optimization of computer model functions to improve the basic understanding of the water cycle over the oceans and its ties to climate. The Aquarius mission operations team also has been tweaking and optimizing algorithms, reprocessing data as needed, and producing salinity movies that has never been seen before. A brief overview of the accomplishments, technical findings to date will be covered in this paper.

Overview of Sea-Ice Properties, Distribution and Temporal Variations, for Application to Ice-Atmosphere Chemical Processes.

NASA Astrophysics Data System (ADS)

Moritz, R. E.

2005-12-01

The properties, distribution and temporal variation of sea-ice are reviewed for application to problems of ice-atmosphere chemical processes. Typical vertical structure of sea-ice is presented for different ice types, including young ice, first-year ice and multi-year ice, emphasizing factors relevant to surface chemistry and gas exchange. Time average annual cycles of large scale variables are presented, including ice concentration, ice extent, ice thickness and ice age. Spatial and temporal variability of these large scale quantities is considered on time scales of 1-50 years, emphasizing recent and projected changes in the Arctic pack ice. The amount and time evolution of open water and thin ice are important factors that influence ocean-ice-atmosphere chemical processes. Observations and modeling of the sea-ice thickness distribution function are presented to characterize the range of variability in open water and thin ice.

Deciphering ocean carbon in a changing world

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moran, Mary Ann; Kujawinski, Elizabeth B.; Stubbins, Aron

Dissolved organic matter (DOM) in the oceans is one of the largest pools of reduced carbon on Earth, comparable in size to the atmospheric CO 2 reservoir. The cycling of DOM over short and long time scales has profound impacts on the quantity of carbon sequestered in the oceans and the foundations of the food webs that support ocean life. At the heart of this cycle lie molecular-level relationships between the individual molecules in DOM and the members of the ocean microbiome that produce and consume them. In the past, these connections have defied clear definition and study because bothmore » DOM and microbial communities consist of many thousands of individual components. Emerging tools in analytical chemistry, microbiology and informatics are breaking down the barriers to a fuller appreciation of these connections. Furthermore, we highlight questions that are being addressed using this new toolkit and consider how these advances are transforming our understanding of some of the most important reactions of the marine carbon cycle.« less

Deciphering ocean carbon in a changing world

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moran, Mary Ann; Kujawinski, Elizabeth B.; Stubbins, Aron

2016-03-07

Dissolved organic matter (DOM) in the oceans is one of the largest pools of reduced carbon on Earth, comparable in size to the atmospheric CO2 reservoir. The cycling of DOM over short and long time scales has profound impacts on the quantity of carbon sequestered in the oceans and the foundations of the food webs that support ocean life. At the heart of this cycle lie molecular-level relationships between the individual molecules in DOM and the members of the ocean microbiome that produce and consume them. In the past, these connections have defied clear definition and study because both DOMmore » and microbial communities consist of many thousands of individual components. Emerging tools in analytical chemistry, microbiology and informatics are breaking down the barriers to a fuller appreciation of these connections. Here we highlight questions that are being addressed using this new toolkit and consider how these advances are transforming our understanding of some of the most important reactions of the marine carbon cycle.« less

Deciphering ocean carbon in a changing world

DOE PAGES

Moran, Mary Ann; Kujawinski, Elizabeth B.; Stubbins, Aron; ...

2016-03-07

Dissolved organic matter (DOM) in the oceans is one of the largest pools of reduced carbon on Earth, comparable in size to the atmospheric CO 2 reservoir. The cycling of DOM over short and long time scales has profound impacts on the quantity of carbon sequestered in the oceans and the foundations of the food webs that support ocean life. At the heart of this cycle lie molecular-level relationships between the individual molecules in DOM and the members of the ocean microbiome that produce and consume them. In the past, these connections have defied clear definition and study because bothmore » DOM and microbial communities consist of many thousands of individual components. Emerging tools in analytical chemistry, microbiology and informatics are breaking down the barriers to a fuller appreciation of these connections. Furthermore, we highlight questions that are being addressed using this new toolkit and consider how these advances are transforming our understanding of some of the most important reactions of the marine carbon cycle.« less

Assessing recent air-sea freshwater flux changes using a surface temperature-salinity space framework

NASA Astrophysics Data System (ADS)

Grist, Jeremy P.; Josey, Simon A.; Zika, Jan D.; Evans, Dafydd Gwyn; Skliris, Nikolaos

2016-12-01

A novel assessment of recent changes in air-sea freshwater fluxes has been conducted using a surface temperature-salinity framework applied to four atmospheric reanalyses. Viewed in the T-S space of the ocean surface, the complex pattern of the longitude-latitude space mean global Precipitation minus Evaporation (PME) reduces to three distinct regions. The analysis is conducted for the period 1979-2007 for which there is most evidence for a broadening of the (atmospheric) tropical belt. All four of the reanalyses display an increase in strength of the water cycle. The range of increase is between 2% and 30% over the period analyzed, with an average of 14%. Considering the average across the reanalyses, the water cycle changes are dominated by changes in tropical as opposed to mid-high latitude precipitation. The increases in the water cycle strength, are consistent in sign, but larger than in a 1% greenhouse gas run of the HadGEM3 climate model. In the model a shift of the precipitation/evaporation cells to higher temperatures is more evident, due to the much stronger global warming signal. The observed changes in freshwater fluxes appear to be reflected in changes in the T-S distribution of the Global Ocean. Specifically, across the diverse range of atmospheric reanalyses considered here, there was an acceleration of the hydrological cycle during 1979-2007 which led to a broadening of the ocean's salinity distribution. Finally, although the reanalyses indicate that the warm temperature tropical precipitation dominated water cycle change, ocean observations suggest that ocean processes redistributed the freshening to lower ocean temperatures.

Merging Ocean Color Data from Multiple Missions. Chapter 12

NASA Technical Reports Server (NTRS)

Gregg, Watson W.

2001-01-01

Oceanic phytoplankton may play an important role in the cycling of carbon on the Earth, through the uptake of carbon dioxide in the process of photosynthesis. Although they are ubiquitous in the global oceans, their abundances and dynamics are difficult to estimate, primarily due to the vast spatial extent of the oceans and the short time scales over which their abundances can change. Consequently, the effects of oceanic phytoplankton on biogeochemical cycling, climate change, and fisheries are not well known. In response to the potential importance of phytoplankton in the global carbon cycle and the lack of comprehensive data, the National Aeronautics and Space Administration (NASA) and the international community have established high priority satellite missions designed to acquire and produce high quality ocean color data. Seven of the missions are routine global observational missions: the Ocean Color and Temperature Sensor (OCTS), the Polarization and Directionality of the Earth's Reflectances sensor (POLDER), Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Moderate Resolution Imaging Spectrometer-AM (MODIS-AM), Medium Resolution Imaging Spectrometer (MERIS), Global Imager (GLI), and MODIS-PM. In addition, there are several other missions capable of providing ocean color data on smaller scales. Most of these missions contain the spectral band complement considered necessary to derive oceanic pigment concentrations (i.e., phytoplankton abundance) and other related parameters. Many contain additional bands that can provide important ancillary information about the optical and biological state of the oceans. Any individual ocean color mission is limited in ocean coverage due to sun glint and clouds. For example, one of the first proposed missions, the SeaWiFS, can provide about 45% coverage of the global ocean in four days and only about 15% in one day.

Episodic inputs of atmospheric nitrogen to the Sargasso Sea: Contributions to new production and phytoplankton blooms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michaels, A.F.; Johnson, R.J.; Siegel, D.A.

1993-06-01

This paper compares a recent atmospheric wet deposition record (including all measurable daily rainfall events between October 1988 and June 1991) with concurrent measurements of nitrogen cycling and biomass at the U.S. Joint Global Ocean Flux Study Bermuda Atlantic Time Series Study station. The two data sets, among the most complete synoptic records of atmospheric nitrogen deposition and ocean nitrogen cycling, provide an opportunity to directly assess the importance of nitrogen deposition in the ocean. The results indicate that individual nitrogen wet deposition events are usually small compared to the ambient nitrogen cycle and that only under sustained calm conditionsmore » following large deposition events will nitrogen deposition processes be an important signal for the understanding of ocean biochemistry. 46 refs., 7 figs.« less

Evidence from Ocean Drilling Program Leg 149 mafic igneous rocks for oceanic crust in the Iberia Abyssal Plain ocean-continent transition zone

NASA Astrophysics Data System (ADS)

Seifert, Karl E.; Chang, Cheng-Wen; Brunotte, Dale A.

1997-04-01

Leg 149 of the Ocean Drilling Program explored the ocean-continent transition (OCT) on the Iberia Abyssal Plain and its role in the opening of the Atlantic Ocean approximately 130 Ma. Mafic igneous rocks recovered from Holes 899B and 900A have Mid-Ocean Ridge Basalt (MORB) trace element and isotopic characteristics indicating that a spreading center was active during the opening of the Iberia Abyssal Plain OCT. The Hole 899B weathered basalt and diabase clasts have transitional to enriched MORB rare earth element characteristics, and the Hole 900A metamorphosed gabbros have MORB initial epsilon Nd values between +6 and +11. During the opening event the Iberia Abyssal Plain OCT is envisioned to have resembled the central and northern parts of the present Red Sea with localized spreading centers and magma chambers producing localized patches of MORB mafic rocks. The lack of a normal ocean floor magnetic anomaly pattern in the Iberia Abyssal Plain means that a continuous spreading center similar to that observed in the present southern Red Sea was not formed before spreading ceased in the Iberia Abyssal Plain OCT and jumped to the present Mid-Atlantic Ridge.

Changes in water mass exchange between the NW shelf areas and the North Atlantic and their impact on nutrient/carbon cycling

NASA Astrophysics Data System (ADS)

Gröger, Matthias; Maier-Reimer, Ernst; Mikolajewicz, Uwe; Segschneider, Joachim; Sein, Dimitry

2010-05-01

Despite their comparatively small extension on a global scale, shelf areas are of interest for several economic reasons and climatic processes related to nutrient cycling, sea food supply, and biological productivity. Moreover, they constitute an important interface for nutrients, pollutants and freshwater on their pathway from the continents to the open ocean. This modelling study aims to investigate the spatial and temporal variability of water mass exchange between the North Atlantic and the NW European shelf and their impact on nutrient/carbon cycling and biological productivity. For this, a new modeling approach has been set up which bridges the gap between pure shelf models where water mass transports across the model domain too strongly depend on the formulation of open boundaries and global models suffering under their too coarse resolution in shelf regions. The new model consists of the global ocean and carbon cycle model MPIOM/HAMOCC with strongly increased resolution in the North Sea and the North Atlantic coupled to the regional atmosphere model REMO. The model takes the full luni-solar tides into account. It includes further a 12 layer sediment module with the relevant pore water chemistry. The main focus lies on the governing mechanisms of water mass exchange across the shelf break and the imprint on shelf biogeochemistry. For this, artificial tracers with a prescribed decay rate have been implemented to distinguish waters arriving from polar and shelf regions and those that originate from the tropics. Experiments were carried out for the years 1948 - 2007. The relationship to larger scale circulation patterns like the position and variability of the subtropical and subpolar gyres is analyzed. The water mass exchange is analyzed with respect to the nutrient concentration and productivity on the European shelf areas. The implementation of tides leads to an enhanced vertical mixing which causes lower sea surface temperatures compared to simulations without tidal forcing. The simulated tidal currents exceed velocities of 30cm per second in the near bottom layer which leads to a strong resuspension of sediment particles. These effects are most pronounced along narrow and shallow topographic structures like e.g. the English Channel. Experiments with artificial tracers show that the composition of water column changes along with the induced climate warming.

Open science resources for the discovery and analysis of Tara Oceans data

PubMed Central

Pesant, Stéphane; Not, Fabrice; Picheral, Marc; Kandels-Lewis, Stefanie; Le Bescot, Noan; Gorsky, Gabriel; Iudicone, Daniele; Karsenti, Eric; Speich, Sabrina; Troublé, Romain; Dimier, Céline; Searson, Sarah; Acinas, Silvia G.; Bork, Peer; Boss, Emmanuel; Bowler, Chris; Vargas, Colomban De; Follows, Michael; Gorsky, Gabriel; Grimsley, Nigel; Hingamp, Pascal; Iudicone, Daniele; Jaillon, Olivier; Kandels-Lewis, Stefanie; Karp-Boss, Lee; Karsenti, Eric; Krzic, Uros; Not, Fabrice; Ogata, Hiroyuki; Pesant, Stéphane; Raes, Jeroen; Reynaud, Emmanuel G.; Sardet, Christian; Sieracki, Mike; Speich, Sabrina; Stemmann, Lars; Sullivan, Matthew B.; Sunagawa, Shinichi; Velayoudon, Didier; Weissenbach, Jean; Wincker, Patrick

2015-01-01

The Tara Oceans expedition (2009–2013) sampled contrasting ecosystems of the world oceans, collecting environmental data and plankton, from viruses to metazoans, for later analysis using modern sequencing and state-of-the-art imaging technologies. It surveyed 210 ecosystems in 20 biogeographic provinces, collecting over 35,000 samples of seawater and plankton. The interpretation of such an extensive collection of samples in their ecological context requires means to explore, assess and access raw and validated data sets. To address this challenge, the Tara Oceans Consortium offers open science resources, including the use of open access archives for nucleotides (ENA) and for environmental, biogeochemical, taxonomic and morphological data (PANGAEA), and the development of on line discovery tools and collaborative annotation tools for sequences and images. Here, we present an overview of Tara Oceans Data, and we provide detailed registries (data sets) of all campaigns (from port-to-port), stations and sampling events. PMID:26029378

Open science resources for the discovery and analysis of Tara Oceans data

NASA Astrophysics Data System (ADS)

2015-05-01

The Tara Oceans expedition (2009-2013) sampled contrasting ecosystems of the world oceans, collecting environmental data and plankton, from viruses to metazoans, for later analysis using modern sequencing and state-of-the-art imaging technologies. It surveyed 210 ecosystems in 20 biogeographic provinces, collecting over 35,000 samples of seawater and plankton. The interpretation of such an extensive collection of samples in their ecological context requires means to explore, assess and access raw and validated data sets. To address this challenge, the Tara Oceans Consortium offers open science resources, including the use of open access archives for nucleotides (ENA) and for environmental, biogeochemical, taxonomic and morphological data (PANGAEA), and the development of on line discovery tools and collaborative annotation tools for sequences and images. Here, we present an overview of Tara Oceans Data, and we provide detailed registries (data sets) of all campaigns (from port-to-port), stations and sampling events.

Open science resources for the discovery and analysis of Tara Oceans data.

PubMed

Pesant, Stéphane; Not, Fabrice; Picheral, Marc; Kandels-Lewis, Stefanie; Le Bescot, Noan; Gorsky, Gabriel; Iudicone, Daniele; Karsenti, Eric; Speich, Sabrina; Troublé, Romain; Dimier, Céline; Searson, Sarah

2015-01-01

The Tara Oceans expedition (2009-2013) sampled contrasting ecosystems of the world oceans, collecting environmental data and plankton, from viruses to metazoans, for later analysis using modern sequencing and state-of-the-art imaging technologies. It surveyed 210 ecosystems in 20 biogeographic provinces, collecting over 35,000 samples of seawater and plankton. The interpretation of such an extensive collection of samples in their ecological context requires means to explore, assess and access raw and validated data sets. To address this challenge, the Tara Oceans Consortium offers open science resources, including the use of open access archives for nucleotides (ENA) and for environmental, biogeochemical, taxonomic and morphological data (PANGAEA), and the development of on line discovery tools and collaborative annotation tools for sequences and images. Here, we present an overview of Tara Oceans Data, and we provide detailed registries (data sets) of all campaigns (from port-to-port), stations and sampling events.

Unsteady seasons in the sea

NASA Astrophysics Data System (ADS)

Hauck, Judith

2018-01-01

Ocean uptake of CO2 slows the rate of anthropogenic climate change but comes at the cost of ocean acidification. Observations now show that the seasonal cycle of CO2 in the ocean also changes, leading to earlier occurrence of detrimental conditions for ocean biota.

Southern Ocean dust-climate coupling over the past four million years.

PubMed

Martínez-Garcia, Alfredo; Rosell-Melé, Antoni; Jaccard, Samuel L; Geibert, Walter; Sigman, Daniel M; Haug, Gerald H

2011-08-03

Dust has the potential to modify global climate by influencing the radiative balance of the atmosphere and by supplying iron and other essential limiting micronutrients to the ocean. Indeed, dust supply to the Southern Ocean increases during ice ages, and 'iron fertilization' of the subantarctic zone may have contributed up to 40 parts per million by volume (p.p.m.v.) of the decrease (80-100 p.p.m.v.) in atmospheric carbon dioxide observed during late Pleistocene glacial cycles. So far, however, the magnitude of Southern Ocean dust deposition in earlier times and its role in the development and evolution of Pleistocene glacial cycles have remained unclear. Here we report a high-resolution record of dust and iron supply to the Southern Ocean over the past four million years, derived from the analysis of marine sediments from ODP Site 1090, located in the Atlantic sector of the subantarctic zone. The close correspondence of our dust and iron deposition records with Antarctic ice core reconstructions of dust flux covering the past 800,000 years (refs 8, 9) indicates that both of these archives record large-scale deposition changes that should apply to most of the Southern Ocean, validating previous interpretations of the ice core data. The extension of the record beyond the interval covered by the Antarctic ice cores reveals that, in contrast to the relatively gradual intensification of glacial cycles over the past three million years, Southern Ocean dust and iron flux rose sharply at the Mid-Pleistocene climatic transition around 1.25 million years ago. This finding complements previous observations over late Pleistocene glacial cycles, providing new evidence of a tight connection between high dust input to the Southern Ocean and the emergence of the deep glaciations that characterize the past one million years of Earth history.

Seasonality of mercury in the Atlantic marine boundary layer

NASA Astrophysics Data System (ADS)

Soerensen, Anne L.; Sunderland, Elsie; Skov, Henrik; Holmes, Christopher; Jacob, Daniel J.

2010-05-01

Around one third of the mercury emissions today are from primary anthropogenic sources, with the remaining two-thirds from secondary reemissions of earlier deposition and natural sources (AMAP/UNEP 2008). Mercury exchange at the air-sea interface is important for the global distribution of atmospheric mercury as parts of deposited mercury will reenter the atmosphere through evasion. The exchange at the air-sea interface also affects the amount of inorganic mercury in the ocean and thereby the conversion to the neuro-toxic methylmercury. Here we combine new cruise measurements in the atmospheric marine boundary layer (MBL) of the Atlantic Ocean (Northern Hemisphere) from the fall of 2006 and the spring of 2007 with existing data from cruises in the Atlantic Ocean since 1978. We observe from these data a seasonal cycle in Hg(0) concentrations in the Atlantic marine boundary later (MBL) that exhibits minimum concentrations during summer and high concentrations during fall to spring. These observations suggest a local, seasonally dependent Hg(0) source in the MBL that causes variability in concentrations above the open ocean. To further investigate controls on Hg(0) concentrations in the MBL, we developed an improved representation of oceanic air-sea exchange processes within the GEOS-Chem global 3-D biogeochemical mercury model. Specifically, we used new data on mercury redox reactions in the surface ocean as a function of biological and photochemical processes, and implemented new algorithms for mercury dynamics associated with suspended particles. Our coupled atmospheric-oceanic modeling results support the premise that oceanic evasion is a main driver controlling Hg(0) concentrations in the MBL. We also use the model to investigate what drivers the evasion across the air-sea interface on shorter timescales. This is done by tracking evasion rates and other model components on an hourly basis for chosen locations in the Atlantic Ocean.

Kinetic control on Zn isotope signatures recorded in marine diatoms

NASA Astrophysics Data System (ADS)

Köbberich, Michael; Vance, Derek

2017-08-01

Marine diatoms dominate the oceanic cycle of the essential micronutrient zinc (Zn). The stable isotopes of zinc and other metals are increasingly used to understand trace metal micronutrient cycling in the oceans. One clear feature of the early isotope data is the heavy Zn isotope signature of the average oceanic dissolved pool relative to the inputs, potentially driven by uptake of light isotopes into phytoplankton cells and export to sediments. However, despite the fact that diatoms strip Zn from surface waters across the Antarctic polar front in the Southern Ocean, the local upper ocean is not isotopically heavy. Here we use culturing experiments to quantify the extent of Zn isotope fractionation by diatoms and to elucidate the mechanisms driving it. We have cultured two different open-ocean diatom species (T. oceanica and Chaetoceros sp.) in a series of experiments at constant medium Zn concentration but at bioavailable medium Fe ranging from limiting to replete. We find that T. oceanica can maintain high growth rates and Zn uptake rates over the full range of bioavailable iron (Fe) investigated, and that the Zn taken up has a δ66Zn that is unfractionated relative to that of the bioavailable free Zn in the medium. The studied representative of the genus Chaetoceros, on the other hand, shows more significantly reduced Zn uptake rates at low Fe and records more variable biomass δ66Zn signatures, of up to 0.85‰ heavier than the medium. We interpret the preferential uptake of heavy isotopes at extremely low Zn uptake rates as potentially due to either of the following two mechanisms. First, the release of extracellular polymeric substances (EPS), at low Fe levels, may preferentially scavenge heavy Zn isotopes. Second, the Zn uptake rate may be slow enough to establish pseudo-equilibrium conditions at the transporter site, with heavy Zn isotopes forming more stable surface complexes. Thus we find that, in our experiments, Fe-limitation exerts a key control that not only limits diatom growth, but also affects the Zn uptake physiology of diatoms. Uptake of heavy isotopes occurs under Fe-limiting conditions that drive extremely low Zn uptake rates. On the other hand, more rapid Zn uptake rates result in biomass that is indistinguishable from the external bioavailable free Zn pool. These experimental results can, in principle, explain the range of Zn isotopic compositions found in the real surface ocean, given the geographically variable interplay between Fe-limitation, Zn uptake rates, and the degree of organic complexation of oceanic Zn.

Distribution of Dissolved Zinc in the Western and Central Subarctic North Pacific

NASA Astrophysics Data System (ADS)

Kim, Taejin; Obata, Hajime; Nishioka, Jun; Gamo, Toshitaka

2017-09-01

We investigated the biogeochemical cycling of dissolved zinc (Zn) in the western and central subarctic North Pacific during the GEOTRACES GP 02 cruise. The relationship between dissolved Zn and silicate in the subarctic North Pacific plotted as a concave curve. Values of Zn* were strongly positive in the intermediate waters (26.6-27.5 σθ) of both the western and the central subarctic North Pacific. There was a distinct kink in the relationship between dissolved Zn and soluble reactive phosphorus (SRP) at the transition from shallow to intermediate water, which is similar to what has been reported for other open oceans. The high Zn:SRP ratio and high Zn* in the intermediate water suggest that intermediate water masses play an important role in the decoupling of dissolved Zn and silicate in the subarctic North Pacific, which implies that the biogeochemical processes that control dissolved Zn and silicate in the intermediate water are different from those in other oceanic regions.

Phosphorus cycling. Major role of planktonic phosphate reduction in the marine phosphorus redox cycle.

PubMed

Van Mooy, B A S; Krupke, A; Dyhrman, S T; Fredricks, H F; Frischkorn, K R; Ossolinski, J E; Repeta, D J; Rouco, M; Seewald, J D; Sylva, S P

2015-05-15

Phosphorus in the +5 oxidation state (i.e., phosphate) is the most abundant form of phosphorus in the global ocean. An enigmatic pool of dissolved phosphonate molecules, with phosphorus in the +3 oxidation state, is also ubiquitous; however, cycling of phosphorus between oxidation states has remained poorly constrained. Using simple incubation and chromatography approaches, we measured the rate of the chemical reduction of phosphate to P(III) compounds in the western tropical North Atlantic Ocean. Colonial nitrogen-fixing cyanobacteria in surface waters played a critical role in phosphate reduction, but other classes of plankton, including potentially deep-water archaea, were also involved. These data are consistent with marine geochemical evidence and microbial genomic information, which together suggest the existence of a vast oceanic phosphorus redox cycle. Copyright © 2015, American Association for the Advancement of Science.

Implications for an Enhanced Biological Pump in the Sea-Ice Reduction Region of the Western Arctic Ocean

NASA Astrophysics Data System (ADS)

Nishino, S.; Shimada, K.; Itoh, M.; Yamamoto-Kawai, M.; Chiba, S.

2009-12-01

Since the late 1990s, catastrophic sea-ice reduction during summer has been observed in the western Arctic Ocean. Regions of decreasing sea ice might be associated with increased biological production compared to ice-covered ocean areas due to light intensification in the water column. The R/V Mirai field experiments in summer 2004 revealed that the algal biomass (chlorophyll a) in the open water region of the western Canada Basin increased from that observed in summer 1994, when the sea ice covered that area. Under the euphotic zone of the increased algal biomass area, evidence of diatom detritus decomposition was found, while such evidence was not observed in 1994, suggesting an enhancement of biological pump (see figure). The increase of algal biomass was not found throughout the sea-ice reduction region; rather, it was observed western Canada Basin where nutrients are effectively supplied from shelf regions. Further west from the Canada Basin, Russian river water with relatively high nutrients may play an important role in the biogeochemical cycles. Monthly sea-ice concentrations (white = 100%, black = 0%) in September of (a) 1994 and (b) 2004 (National Ice Center), and (c) vertical profiles of silicate obtained from the field experiments of Arctic Ocean Section 94 in 1994 (○) and Mirai04 in 2004 (■). The positions where the profiles were obtained are depicted by dots in (a) and (b), respectively.

Cell surface reactivity of Synechococcus sp. PCC 7002: Implications for metal sorption from seawater

NASA Astrophysics Data System (ADS)

Liu, Yuxia; Alessi, D. S.; Owttrim, G. W.; Petrash, D. A.; Mloszewska, A. M.; Lalonde, S. V.; Martinez, R. E.; Zhou, Qixing; Konhauser, K. O.

2015-11-01

The past two decades have seen a significant advancement in our understanding of bacterial surface chemistry and the ability of microbes to bind metals from aqueous solutions. Much of this work has been aimed at benthic, mat-forming species in an effort to model the mechanisms by which microbes may exert control over metal contaminant transport in soils and groundwater. However, there is a distinct paucity of information pertaining to the surface chemistry of marine planktonic species, and their ability to bind trace metals from the ocean's photic zone. To this end, the surface properties of the cyanobacterium Synechococcus sp. PCC 7002 were studied as this genus is one of the dominant marine phytoplankton, and as such, contributes significantly to metal cycling in the ocean's photic zone. Zeta potential measurement indicates that the cell surfaces display a net negative charge. This was supported by potentiometric titration and Fourier transform infrared spectroscopy analyses demonstrating that the cells are dominated by surface proton releasing ligands, including carboxyl, phosphoryl and amino functional groups, with a total ligand density of 34.18 ± 1.62 mmol/g (dry biomass). Cd adsorption experiments further reveal that carboxyl groups play a primary role in metal adsorption, with 1.0 g of dry biomass binding an equivalent of 7.05 × 10-5 M of Cd from solution at pH = 8. To put this value into context, in 1 L of seawater, and with an open-ocean population of Synechococcus of 105 cells/mL in the photic zone, approximately 10 nmol of Cd could potentially be adsorbed by the cyanobacteria; an amount equivalent to seawater Cd concentrations. Although we have only focused on one microbial species and one metal cation, and we have not considered trace element assimilation, our results highlight the potential role of surface sorption by phytoplankton in the cycling of metals in the ocean.

The role of iron in the biogeochemistry of the Southern Ocean and equatorial Pacific: a comparison of in situ iron enrichments

NASA Astrophysics Data System (ADS)

Boyd, Philip W.

A better understanding of the relationship between iron supply and the biogeochemical functioning of high nitrate low chlorophyll (HNLC) regions may be obtained by comparing and contrasting observations from oceanic provinces. The open polar Southern Ocean and the eastern equatorial Pacific are HNLC regimes, but have different oceanographic properties. Until recently, there have been insufficient datasets on the role of iron (mainly from deckboard iron enrichments) to enable a comprehensive comparison of these regions. However, the recent Southern Ocean Iron RElease Experiment (SOIREE), the first in situ iron enrichment in polar waters, provides a detailed suite of time-series measurements to compare with those from the equatorial Pacific IronEx II study. As expected, a comparison of these polar and tropical studies yielded differences in the timing of iron-mediated responses that are mainly due to the temperature-dependence of biological rates. However, trends from both studies are similar with respect to the magnitude of iron-mediated changes in bulk signals (such as macronutrient uptake), algal physiological responses, and shifts in algal community structure. There are also parallels between these studies in the response of components of the pelagic ecosystem such as heterotrophic bacteria. Such convergence suggests that it is possible to incorporate considerable detail into future generic models investigating the role of the biota in the biogeochemical cycling of iron. There are also significant differences, such as the degree of herbivory, and the fate of the accumulated algal carbon during these two iron-stimulated phytoplankton blooms. Such departures offer a means to understand better important regional differences in the biogeochemical cycling of iron in HNLC waters, and to investigate the possible effects of physical artefacts—caused by mixing with surrounding HNLC waters at the boundaries of these labelled patches—during such mesoscale perturbation experiments.

Insights into the paleoclimate of the PETM from an ensemble of EMIC simulations

NASA Astrophysics Data System (ADS)

Keery, John; Holden, Philip; Edwards, Neil; Monteiro, Fanny; Ridgwell, Andy

2016-04-01

The Eocene epoch, and in particular, the Paleocene-Eocene Thermal Maximum (PETM) of 55.8 Ma, exhibit several features of particular interest for probing our understanding of the Earth system and carbon cycle. CO2 levels have not yet been definitively established, but were known to have varied considerably, peaking at up to several times modern values. Temperatures were several degrees higher than in the modern era, and there were periods of relatively rapid warming, with substantial variability in carbon cycle processes. The Eocene is therefore highly relevant for our understanding of the climate of the 21st Century. Earth system models of intermediate complexity (EMICs), with less detailed simulation of the dynamics of the atmosphere and oceans than general circulation models (GCMs), are sufficiently fast to allow climate modelling over long periods of geological time in comparatively short periods of computer run-time. This speed advantage of EMICs over GCMs permits an "ensemble" of model simulations to be run, allowing statistical analysis of results to be carried out, and allowing the uncertainties in model predictions to be estimated. Here we apply the EMICs PLASIM-GENIE, and GENIE-1, with an Eocene paleogeography which incorporates the major continental configurations and ocean connections, including a shallow strait linking the Arctic to the Tethys, but with neither the Tasman Gateway nor the Drake Passage yet open. Our two model strategy benefits from the detailed simulation of ocean biogeochemistry in GENIE-1, and the 3D spectral atmospheric dynamics in PLASIM-GENIE, which also provides boundary conditions for the GENIE-1 simulations. Using a 50-member ensemble of 1000-year quasi-equilibrium simulations with PLASIM-GENIE, we investigate the relative contributions of orbital and CO2 variability on climate and equator-pole temperature gradients. Results from PLASIM-GENIE are used to configure a harmonised ensemble of GENIE-1 simulations, which will be compared with newly obtained geochemical data on ocean oxygenation through the Eocene from the UK NERC RESPIRE project.

An ensemble Kalman filter with a high-resolution atmosphere-ocean coupled model for tropical cyclone forecasts

NASA Astrophysics Data System (ADS)

Kunii, M.; Ito, K.; Wada, A.

2015-12-01

An ensemble Kalman filter (EnKF) using a regional mesoscale atmosphere-ocean coupled model was developed to represent the uncertainties of sea surface temperature (SST) in ensemble data assimilation strategies. The system was evaluated through data assimilation cycle experiments over a one-month period from July to August 2014, during which a tropical cyclone as well as severe rainfall events occurred. The results showed that the data assimilation cycle with the coupled model could reproduce SST distributions realistically even without updating SST and salinity during the data assimilation cycle. Therefore, atmospheric variables and radiation applied as a forcing to ocean models can control oceanic variables to some extent in the current data assimilation configuration. However, investigations of the forecast error covariance estimated in EnKF revealed that the correlation between atmospheric and oceanic variables could possibly lead to less flow-dependent error covariance for atmospheric variables owing to the difference in the time scales between atmospheric and oceanic variables. A verification of the analyses showed positive impacts of applying the ocean model to EnKF on precipitation forecasts. The use of EnKF with the coupled model system captured intensity changes of a tropical cyclone better than it did with an uncoupled atmosphere model, even though the impact on the track forecast was negligibly small.

The Living Ocean. SeaWiFS: Studying Ocean Color from Space. Teacher's Guide with Activities

NASA Technical Reports Server (NTRS)

1994-01-01

This educational document, designed for grades 9 to 10, discusses the observation of oceans from space. Topics covered include ocean color, the role of phytoplankton, the carbon cycle, and the greenhouse effect. Activities and discussion questions are presented.

Anthropogenic carbon in the ocean—Surface to interior connections

NASA Astrophysics Data System (ADS)

Groeskamp, Sjoerd; Lenton, Andrew; Matear, Richard; Sloyan, Bernadette M.; Langlais, Clothilde

2016-11-01

Quantifying the surface to interior transport of anthropogenic carbon (CA) is critical for projecting future carbon uptake and for improved understanding of the role of the oceans in the global carbon cycle. Here we develop and apply a diagnostic tool that provides a volumetric stream function in (CA,σ0) coordinates to calculate the total diapycnal CA transport in the ocean, where σ0 is the surface referenced potential density anomaly. We combine this with air-sea fluxes of CA to infer the internal ocean mixing of CA to obtain a closed globally integrated budget analyses of the ocean's CA transport. This diagnostic separates the contribution from the mean flow, seasonal cycles, trend, surface fluxes, and mixing in the distribution and the accumulation of CA in the ocean. We find that the redistribution of CA from the surface to the interior of the ocean is due to an interplay between circulation and mixing. The circulation component is dominated by the mean flow; however, effects due to seasonal cycles are significant for the CA redistribution. The two most important pathways for CA subduction are through the transformation of thermocline water (TW) into subantarctic mode water and by transformation of Circumpolar Deep Water (CDW) into lighter Antarctic Intermediate Water. The results suggest that an accurate representation of intermediate and mode water formation, deep water formation, and spatial and temporal distribution of ocean mixing in ocean models is essential to simulate and project the oceanic uptake of CA.

The seasonal cycle of pCO2 and CO2 fluxes in the Southern Ocean: diagnosing anomalies in CMIP5 Earth system models

NASA Astrophysics Data System (ADS)

Precious Mongwe, N.; Vichi, Marcello; Monteiro, Pedro M. S.

2018-05-01

The Southern Ocean forms an important component of the Earth system as a major sink of CO2 and heat. Recent studies based on the Coupled Model Intercomparison Project version 5 (CMIP5) Earth system models (ESMs) show that CMIP5 models disagree on the phasing of the seasonal cycle of the CO2 flux (FCO2) and compare poorly with available observation products for the Southern Ocean. Because the seasonal cycle is the dominant mode of CO2 variability in the Southern Ocean, its simulation is a rigorous test for models and their long-term projections. Here we examine the competing roles of temperature and dissolved inorganic carbon (DIC) as drivers of the seasonal cycle of pCO2 in the Southern Ocean to explain the mechanistic basis for the seasonal biases in CMIP5 models. We find that despite significant differences in the spatial characteristics of the mean annual fluxes, the intra-model homogeneity in the seasonal cycle of FCO2 is greater than observational products. FCO2 biases in CMIP5 models can be grouped into two main categories, i.e., group-SST and group-DIC. Group-SST models show an exaggeration of the seasonal rates of change of sea surface temperature (SST) in autumn and spring during the cooling and warming peaks. These higher-than-observed rates of change of SST tip the control of the seasonal cycle of pCO2 and FCO2 towards SST and result in a divergence between the observed and modeled seasonal cycles, particularly in the Sub-Antarctic Zone. While almost all analyzed models (9 out of 10) show these SST-driven biases, 3 out of 10 (namely NorESM1-ME, HadGEM-ES and MPI-ESM, collectively the group-DIC models) compensate for the solubility bias because of their overly exaggerated primary production, such that biologically driven DIC changes mainly regulate the seasonal cycle of FCO2.

Implications of a More Comprehensive Nitrogen Cycle in a Global Biogeochemical Ocean Model

NASA Astrophysics Data System (ADS)

Six, K. D.; Ilyina, T.

2016-02-01

Nitrogen plays a crucial role for nearly all living organisms in the Earth system. Changes in the marine nitrogen cycle not only alter the marine biota, but will also have an impact on the marine carbon cycle and, in turn, on climate due to the close coupling of the carbon-nitrogen cycle. The understanding of processes and controls of the marine nitrogen cycle is therefore a prerequisite to reduce uncertainties in the prediction of future climate. Nevertheless, most ocean biogeochemical components of modern Earth system models have a rather simplistic representation of marine N-cycle mainly focusing on nitrate. Here we present results of the HAMburg Ocean Carbon Cycle model (HAMOCC) as part of the MPI-ESM which was extended by a prognostic representation of ammonium and nitrite to resolve important processes of the marine N-cycle such as nitrification and anaerobic ammonium oxidation (anammox). Additionally, we updated the production of nitrous oxide, an important greenhouse gas, allowing for two sources from oxidation of ammonium (nitrification) and from reduction of nitrite (nitrifier-denitrification) at low oxygen concentrations. Besides an extended model data comparison we discuss the following aspects of the N-cycle by model means: (1) contribution of anammox to the loss of fixed nitrogen, and (2) production and emission of marine nitrous oxide.

A Preliminary Model Study of the Large-Scale Seasonal Cycle in Bottom Pressure Over the Global Ocean

NASA Technical Reports Server (NTRS)

Ponte, Rui M.

1998-01-01

Output from the primitive equation model of Semtner and Chervin is used to examine the seasonal cycle in bottom pressure (Pb) over the global ocean. Effects of the volume-conserving formulation of the model on the calculation Of Pb are considered. The estimated seasonal, large-scale Pb signals have amplitudes ranging from less than 1 cm over most of the deep ocean to several centimeters over shallow, boundary regions. Variability generally increases toward the western sides of the basins, and is also larger in some Southern Ocean regions. An oscillation between subtropical and higher latitudes in the North Pacific is clear. Comparison with barotropic simulations indicates that, on basin scales, seasonal Pb variability is related to barotropic dynamics and the seasonal cycle in Ekman pumping, and results from a small, net residual in mass divergence from the balance between Ekman and Sverdrup flows.

Observing the seasonal cycle of the upper ocean in the Ross Sea, Antarctica, with autonomous profiling floats

NASA Astrophysics Data System (ADS)

Porter, D. F.; Springer, S. R.; Padman, L.; Fricker, H. A.; Bell, R. E.

2017-12-01

The upper layers of the Southern Ocean where it meets the Antarctic ice sheet undergoes a large seasonal cycle controlled by surface radiation and by freshwater fluxes, both of which are strongly influenced by sea ice. In regions where seasonal sea ice and icebergs limit use of ice-tethered profilers and conventional moorings, autonomous profiling floats can sample the upper ocean. The deployment of seven Apex floats (by sea) and six ALAMO floats (by air) provides unique upper ocean hydrographic data in the Ross Sea close to the Ross Ice Shelf front. A novel choice of mission parameters - setting parking depth deeper than the seabed - limits their drift, allowing us to deploy the floats close to the ice shelf front, while sea ice avoidance algorithms allow the floats to to sample through winter under sea ice. Hydrographic profiles show the detailed development of the seasonal mixed layer close to the Ross front, and interannual variability of the seasonal mixed layer and deeper water masses on the central Ross Sea continental shelf. After the sea ice breakup in spring, a warm and fresh surface mixed layer develops, further warming and deepening throughout the summer. The mixed layer deepens, with maximum temperatures exceeding 0ºC in mid-February. By March, the surface energy budget becomes negative and sea ice begins to form, creating a cold, saline and dense surface layer. Once these processes overcome the stable summer stratification, convection erodes the surface mixed layer, mixing some heat downwards to deeper layers. There is considerable interannual variability in the evolution and strength of the surface mixed layer: summers with shorter ice-free periods result in a cooler and shallower surface mixed layer, which accumulates less heat than the summers with longer ice-free periods. Early ice breakup occurred in all floats in 2016/17 summer, enhancing the absorbed solar flux leading to a warmer surface mixed layer. Together, these unique measurements from autonomous profilers provide insight into the hydrographic state of the Ross Sea at the start of the spring period of sea-ice breakup, and how ocean mixing and sea ice interact to initiate the summer open-water season.

Impact of oceanic processes on the carbon cycle during the last termination

NASA Astrophysics Data System (ADS)

Bouttes, N.; Paillard, D.; Roche, D. M.; Waelbroeck, C.; Kageyama, M.; Lourantou, A.; Michel, E.; Bopp, L.

2012-01-01

During the last termination (from ~18 000 years ago to ~9000 years ago), the climate significantly warmed and the ice sheets melted. Simultaneously, atmospheric CO2 increased from ~190 ppm to ~260 ppm. Although this CO2 rise plays an important role in the deglacial warming, the reasons for its evolution are difficult to explain. Only box models have been used to run transient simulations of this carbon cycle transition, but by forcing the model with data constrained scenarios of the evolution of temperature, sea level, sea ice, NADW formation, Southern Ocean vertical mixing and biological carbon pump. More complex models (including GCMs) have investigated some of these mechanisms but they have only been used to try and explain LGM versus present day steady-state climates. In this study we use a coupled climate-carbon model of intermediate complexity to explore the role of three oceanic processes in transient simulations: the sinking of brines, stratification-dependent diffusion and iron fertilization. Carbonate compensation is accounted for in these simulations. We show that neither iron fertilization nor the sinking of brines alone can account for the evolution of CO2, and that only the combination of the sinking of brines and interactive diffusion can simultaneously simulate the increase in deep Southern Ocean δ13C. The scenario that agrees best with the data takes into account all mechanisms and favours a rapid cessation of the sinking of brines around 18 000 years ago, when the Antarctic ice sheet extent was at its maximum. In this scenario, we make the hypothesis that sea ice formation was then shifted to the open ocean where the salty water is quickly mixed with fresher water, which prevents deep sinking of salty water and therefore breaks down the deep stratification and releases carbon from the abyss. Based on this scenario, it is possible to simulate both the amplitude and timing of the long-term CO2 increase during the last termination in agreement with ice core data. The atmospheric δ13C appears to be highly sensitive to changes in the terrestrial biosphere, underlining the need to better constrain the vegetation evolution during the termination.

Impact of oceanic processes on the carbon cycle during the last termination

NASA Astrophysics Data System (ADS)

Bouttes, N.; Paillard, D.; Roche, D. M.; Waelbroeck, C.; Kageyama, M.; Lourantou, A.; Michel, E.; Bopp, L.

2011-06-01

During the last termination (from ~18 000 yr ago to ~9000 yr ago) the climate significantly warmed and the ice sheets melted. Simultaneously, atmospheric CO2 increased from ~190 ppm to ~260 ppm. Although this CO2 rise plays an important role in the deglacial warming, the reasons for its evolution are difficult to explain. Only box models have been used to run transient simulations of this carbon cycle transition, but by forcing the model with data constrained scenarios of the evolution of temperature, sea level, sea ice, NADW formation, Southern Ocean vertical mixing and biological carbon pump. More complex models (including GCMs) have investigated some of these mechanisms but they have only been used to try and explain LGM versus present day steady-state climates. In this study we use a climate-carbon coupled model of intermediate complexity to explore the role of three oceanic processes in transient simulations: the sinking of brines, stratification-dependant diffusion and iron fertilization. Carbonate compensation is accounted for in these simulations. We show that neither iron fertilization nor the sinking of brines alone can account for the evolution of CO2, and that only the combination of the sinking of brines and interactive diffusion can simultaneously simulate the increase in deep Southern Ocean δ13C. The scenario that agrees best with the data takes into account all mechanisms and favours a rapid cessation of the sinking of brines around 18 000 yr ago, when the Antarctic ice sheet extent was at its maximum. Sea ice formation was then shifted to the open ocean where the salty water is quickly mixed with fresher water, which prevents deep sinking of salty water and therefore breaks down the deep stratification and releases carbon from the abyss. Based on this scenario it is possible to simulate both the amplitude and timing of the CO2 increase during the last termination in agreement with data. The atmospheric δ13C appears to be highly sensitive to changes in the terrestrial biosphere, underlining the need to better constrain the vegetation evolution during the termination.

Physical Climatology of Indonesian Maritime Continent: An Overview of Observational Studies

NASA Astrophysics Data System (ADS)

Yamanaka, M. D.

2014-12-01

The Indonesian maritime continent (IMC) is a miniature of our land-sea coexisting planet Earth. Firstly, without interior activity, the Earth becomes an even-surfaced "aqua-planet" with both atmosphere and ocean flowing almost zonally, and solar differential heating generates (global thermal tides and) Hadley's meridional circulations with ITCZ along the equator as observed actually over open (Indian and Pacific) oceans in the both sides of IMC. ITCZ involves intraseasonal variations or super cloud clusters moving eastward. Secondly, the lands and seas over the actual Earth have been keeping the area ratio of 3:7 (similar to that of islands and inland/surrounding seas in IMC), but their displacements have produced IMC near the equator, which turns equatorial Pacific easterly current northward (Kuroshio) and reflects equatorial oceanic waves inducing coupled ocean-atmosphere interannual variations such as ENSO and IOD, or displacements of Walker's zonal circulations. Thirdly, because IMC consists of many large/small islands with very long coastlines, many narrow straits become a dam for the global (Pacific to Indian) ocean circulation, and the land-sea heat capacity contrasts along the coastlines generate the world's largest rainfall with diurnal cycles (sea-land breeze circulations). The diurnal cycles are dominant in the rainy season (austral summer in Jawa and Bali), because rainfall-induced sprinkler-like land cooling reverses the trans-coastal temperature gradient before sunrise, and subsequent clear sky on land until around noon provides solar heating dependent on season. These processes lead to rapid land/hydrosphere-atmosphere water exchange, local air pollutant washout, and transequatorial boreal winter monsoon (cold surge). In El Niño years the cooler sea-surface temperature suppresses the morning coastal-sea rainfall, and induces often serious smog over IMC. Lastly, high-resolution observations/models covering both over islands and seas are necessary. A radar-profiler network (HARIMAU) has been constructed during FY2005-09, and capacity building on radar operations and buoy manufacturing has been promoted during FY2009-13 by Japan-Indonesia collaboration projects, which are taken over by an Indonesian national center (MCCOE) established in November 2013.

Towards coupled physical-biogeochemical models of the ocean carbon cycle

NASA Technical Reports Server (NTRS)

Rintoul, Stephen R.

1992-01-01

The purpose of this review is to discuss the critical gaps in our knowledge of ocean dynamics and biogeochemical cycles. It is assumed that the ultimate goal is the design of a model of the earth system that can predict the response to changes in the external forces driving climate.

A review of ocean color remote sensing methods and statistical techniques for the detection, mapping and analysis of phytoplankton blooms in coastal and open oceans

NASA Astrophysics Data System (ADS)

Blondeau-Patissier, David; Gower, James F. R.; Dekker, Arnold G.; Phinn, Stuart R.; Brando, Vittorio E.

2014-04-01

The need for more effective environmental monitoring of the open and coastal ocean has recently led to notable advances in satellite ocean color technology and algorithm research. Satellite ocean color sensors' data are widely used for the detection, mapping and monitoring of phytoplankton blooms because earth observation provides a synoptic view of the ocean, both spatially and temporally. Algal blooms are indicators of marine ecosystem health; thus, their monitoring is a key component of effective management of coastal and oceanic resources. Since the late 1970s, a wide variety of operational ocean color satellite sensors and algorithms have been developed. The comprehensive review presented in this article captures the details of the progress and discusses the advantages and limitations of the algorithms used with the multi-spectral ocean color sensors CZCS, SeaWiFS, MODIS and MERIS. Present challenges include overcoming the severe limitation of these algorithms in coastal waters and refining detection limits in various oceanic and coastal environments. To understand the spatio-temporal patterns of algal blooms and their triggering factors, it is essential to consider the possible effects of environmental parameters, such as water temperature, turbidity, solar radiation and bathymetry. Hence, this review will also discuss the use of statistical techniques and additional datasets derived from ecosystem models or other satellite sensors to characterize further the factors triggering or limiting the development of algal blooms in coastal and open ocean waters.

The Seasonal Cycle of Carbon in the Southern Pacific Ocean Observed from Biogeochemical Profiling Floats

NASA Astrophysics Data System (ADS)

Sarmiento, J. L.; Gray, A. R.; Johnson, K. S.; Carter, B.; Riser, S.; Talley, L. D.; Williams, N. L.

2016-02-01

The Southern Ocean is thought to play an important role in the ocean-atmosphere exchange of carbon dioxide and the uptake of anthropogenic carbon dioxide. However, the total number of observations of the carbonate system in this region is small and heavily biased towards the summer. Here we present 1.5 years of biogeochemical measurements, including pH, oxygen, and nitrate, collected by 11 autonomous profiling floats deployed in the Pacific sector of the Southern Ocean in April 2014. These floats sampled a variety of oceanographic regimes ranging from the seasonally ice-covered zone to the subtropical gyre. Using an algorithm trained with bottle measurements, alkalinity is estimated from salinity, temperature, and oxygen and then used together with the measured pH to calculate total carbon dioxide and pCO2 in the upper 1500 dbar. The seasonal cycle in the biogeochemical quantities is examined, and the factors governing pCO2 in the surface waters are analyzed. The mechanisms driving the seasonal cycle of carbon are further investigated by computing budgets of heat, carbon, and nitrogen in the mixed layer. Comparing the different regimes sampled by the floats demonstrates the complex and variable nature of the carbon cycle in the Southern Ocean.

Merging Ocean Color Data From Multiple Missions. Chapter 6

NASA Technical Reports Server (NTRS)

Gregg, Watson W.

2003-01-01

Oceanic phytoplankton may play an important role in the cycling of carbon on the Earth, through the uptake of carbon dioxide in the process of photosynthesis. Although they are ubiquitous in the global oceans, their abundances and dynamics are difficult to estimate, primarily due to the vast spatial extent of the oceans and the short time scales over which their abundances can change. Consequently, the effects of oceanic phytoplankton on biogeochemical cycling, climate change, and fisheries are not well known. In response to the potential importance of phytoplankton in the global carbon cycle and the lack of comprehensive data, NASA and the international community have established high priority satellite missions designed to acquire and produce high quality ocean color data (Table 6.1). Ten of the missions are routine global observational missions: the Ocean Color and Temperature Sensor (OCTS), the Polarization and Directionality of the Earth's Reflectances sensor (POLDER), Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Moderate Resolution Imaging Spectrometer-AM (MODIS-AM), Medium Resolution Imaging Spectrometer (MERIS), Global Imager (GLI), MODIS-PM, Super-GLI (S-GLI), and the Visible/Infrared Imager and Radiometer Suite (VIIRS) on the NPOESS Preparatory Project (NPP) and the National Polar-orbiting Operational Environmental Satellite System (NPOESS). In addition, there are several other missions capable of providing ocean color data on smaller scales. Most of these missions contain the spectral band complement considered necessary to derive oceanic chlorophyll concentrations and other related parameters. Many contain additional bands that can provide important ancillary information about the optical and biological state of the oceans.

Oceanic nitrogen cycling and N2O flux perturbations in the Anthropocene

NASA Astrophysics Data System (ADS)

Landolfi, A.; Somes, C. J.; Koeve, W.; Zamora, L. M.; Oschlies, A.

2017-08-01

There is currently no consensus on how humans are affecting the marine nitrogen (N) cycle, which limits marine biological production and CO2 uptake. Anthropogenic changes in ocean warming, deoxygenation, and atmospheric N deposition can all individually affect the marine N cycle and the oceanic production of the greenhouse gas nitrous oxide (N2O). However, the combined effect of these perturbations on marine N cycling, ocean productivity, and marine N2O production is poorly understood. Here we use an Earth system model of intermediate complexity to investigate the combined effects of estimated 21st century CO2 atmospheric forcing and atmospheric N deposition. Our simulations suggest that anthropogenic perturbations cause only a small imbalance to the N cycle relative to preindustrial conditions (˜+5 Tg N y-1 in 2100). More N loss from water column denitrification in expanded oxygen minimum zones (OMZs) is counteracted by less benthic denitrification, due to the stratification-induced reduction in organic matter export. The larger atmospheric N load is offset by reduced N inputs by marine N2 fixation. Our model predicts a decline in oceanic N2O emissions by 2100. This is induced by the decrease in organic matter export and associated N2O production and by the anthropogenically driven changes in ocean circulation and atmospheric N2O concentrations. After comprehensively accounting for a series of complex physical-biogeochemical interactions, this study suggests that N flux imbalances are limited by biogeochemical feedbacks that help stabilize the marine N inventory against anthropogenic changes. These findings support the hypothesis that strong negative feedbacks regulate the marine N inventory on centennial time scales.

Excerpt from a Forthcoming Book. The Ocean Book: Dive In--The Beginning of Your Ocean Study.

ERIC Educational Resources Information Center

Science Activities, 1989

1989-01-01

Six activities complete with reproducible worksheets are presented. Materials and procedures for each are listed. Answers to the quiz and crossword puzzle are included. Topics include the water cycle, the world's oceans, the ocean floor, and fish. (CW)

From rifting to subduction: the role of inheritance in the Wilson Cycle

NASA Astrophysics Data System (ADS)

Beaussier, Stéphane; Gerya, Taras; Burg, Jean-Pierre

2017-04-01

The Wilson Cycle entails that oceans close and reopen. This cycle is a fundamental principle in plate tectonics, inferring continuity from divergence to convergence and that continental rifting takes place along former suture zones. This view questions the role of inherited structures at each stage of the Wilson Cycle. Using the 3D thermo-mechanical code, I3ELVIS (Gerya and Yuen 2007) we present a high-resolution continuous model of the Wilson cycle from continental rifting, breakup and oceanic spreading to convergence and spontaneous subduction initiation. Therefore, all lateral and longitudinal structures of the lithospheres are generated self-consistently and are consequences of the initial continental structure, tectono-magmatic inheritance and material rheology. In the models, subduction systematically initiates off-ridge and is controlled by the convergence-induced swelling of the ridge. Geometry and dynamics of the developing off-ridge subduction is controlled by four main factors: (1) the obliquity of the ridge with respect to the convergence direction; (2) fluid-induced weakening of the oceanic crust; (3) irregularity of ridge and margins inherited from rifting and spreading; (4) strain localization at transform faults formed during ocean floor spreading. Further convergence can lead to obduction of the oceanic crust and segments of ridge after the oceanic lithosphere is entrained into subduction. We show that the main parameters controlling the occurrence and geometry of obducted ophiolite are the convergence rate and the inherited structure of the passive margins and ridge. Our numerical experiments results show the essential role played by inheritance during the Wilson Cycle and are consistent with nature observations such as the tectonic history of the Oman subduction-obduction system. REFERENCES Gerya, T. V., and D. A. Yuen. 2007: "Robust Characteristics Method for Modelling Multiphase Visco-Elasto-Plastic Thermo-Mechanical Problems, Physics of the Earth and Planetary Interiors, 163 (1-4), 83-105.

Patterns of Genetic Diversity and Co-Existence in Open Ocean Diatoms: the Effects of Water Mass Structure, Selection and Sex

NASA Astrophysics Data System (ADS)

Rynearson, T. A.; Chen, G.

2016-02-01

The open ocean North Atlantic spring bloom influences regional ecology and global biogeochemistry. Diatoms dominate the peak of the bloom and significantly impact productivity and export of organic carbon from the bloom. Despite their key role in a yearly event with global impacts, the genetic diversity and population structure of diatoms that comprise this open ocean bloom are unknown. Here we investigated the population genetics of the diatom Thalassiosira gravida sampled during the 2008 North Atlantic Bloom Experiment using newly-developed microsatellite markers. Here, we show that the genetic diversity of open ocean diatoms is high and that their population structure differs dramatically from coastal diatoms. High levels of genetic diversity were observed across all water samples and did not change during the bloom. Four genetically distinct populations were identified but were not associated with different water masses, depths or time points during the bloom. Instead, all four populations co-existed within samples, spanning different water masses, stages of the bloom and depths of over >300 m. The pattern of genetically distinct, co-existing populations in the open ocean contrasts dramatically with coastal habitats, where distinct populations have not been observed to co-exist at the same time and place. It is likely that populations originate via transport from disparate locations combined with overwintering capacity in the water column or sediments. The pattern of co-existence suggests that the open ocean may serve as a gene pool that harbors different populations that are then available for selection to act upon, which may contribute to the ecological and biogeochemical success of diatoms and influence their long-term evolutionary survival.

Advancing Ocean Science Through Coordination, Community Building, and Outreach

NASA Astrophysics Data System (ADS)

Benway, H. M.

2016-02-01

The US Ocean Carbon and Biogeochemistry (OCB) Program (www.us-ocb.org) is a dynamic network of scientists working across disciplines to understand the ocean's role in the global carbon cycle and how marine ecosystems and biogeochemical cycles are responding to environmental change. The OCB Project Office, which is based at the Woods Hole Oceanographic Institution (WHOI), serves as a central information hub for this network, bringing different scientific disciplines together and cultivating partnerships with complementary US and international programs to address high-priority research questions. The OCB Project Office plays multiple important support roles, such as hosting and co-sponsoring workshops, short courses, working groups, and synthesis activities on emerging research issues; engaging with relevant national and international science planning initiatives; and developing education and outreach activities and products with the goal of promoting ocean carbon science to broader audiences. Current scientific focus areas of OCB include ocean observations (shipboard, autonomous, satellite, etc.); changing ocean chemistry (acidification, expanding low-oxygen conditions, etc.); ocean carbon uptake and storage; estuarine and coastal carbon cycling; biological pump and associated biological and biogeochemical processes and carbon fluxes; and marine ecosystem response to environmental and evolutionary changes, including physiological and molecular-level responses of individual organisms, as well as shifts in community structure and function. OCB is a bottom-up organization that responds to the continually evolving priorities and needs of its network and engages marine scientists at all career stages. The scientific leadership of OCB includes a scientific steering committee and subcommittees on ocean time-series, ocean acidification, and ocean fertilization. This presentation will highlight recent OCB activities and products of interest to the ocean science community.

Ecogenomics and potential biogeochemical impacts of globally abundant ocean viruses.

PubMed

Roux, Simon; Brum, Jennifer R; Dutilh, Bas E; Sunagawa, Shinichi; Duhaime, Melissa B; Loy, Alexander; Poulos, Bonnie T; Solonenko, Natalie; Lara, Elena; Poulain, Julie; Pesant, Stéphane; Kandels-Lewis, Stefanie; Dimier, Céline; Picheral, Marc; Searson, Sarah; Cruaud, Corinne; Alberti, Adriana; Duarte, Carlos M; Gasol, Josep M; Vaqué, Dolors; Bork, Peer; Acinas, Silvia G; Wincker, Patrick; Sullivan, Matthew B

2016-09-29

Ocean microbes drive biogeochemical cycling on a global scale. However, this cycling is constrained by viruses that affect community composition, metabolic activity, and evolutionary trajectories. Owing to challenges with the sampling and cultivation of viruses, genome-level viral diversity remains poorly described and grossly understudied, with less than 1% of observed surface-ocean viruses known. Here we assemble complete genomes and large genomic fragments from both surface- and deep-ocean viruses sampled during the Tara Oceans and Malaspina research expeditions, and analyse the resulting 'global ocean virome' dataset to present a global map of abundant, double-stranded DNA viruses complete with genomic and ecological contexts. A total of 15,222 epipelagic and mesopelagic viral populations were identified, comprising 867 viral clusters (defined as approximately genus-level groups). This roughly triples the number of known ocean viral populations and doubles the number of candidate bacterial and archaeal virus genera, providing a near-complete sampling of epipelagic communities at both the population and viral-cluster level. We found that 38 of the 867 viral clusters were locally or globally abundant, together accounting for nearly half of the viral populations in any global ocean virome sample. While two-thirds of these clusters represent newly described viruses lacking any cultivated representative, most could be computationally linked to dominant, ecologically relevant microbial hosts. Moreover, we identified 243 viral-encoded auxiliary metabolic genes, of which only 95 were previously known. Deeper analyses of four of these auxiliary metabolic genes (dsrC, soxYZ, P-II (also known as glnB) and amoC) revealed that abundant viruses may directly manipulate sulfur and nitrogen cycling throughout the epipelagic ocean. This viral catalog and functional analyses provide a necessary foundation for the meaningful integration of viruses into ecosystem models where they act as key players in nutrient cycling and trophic networks.

Ecogenomics and potential biogeochemical impacts of globally abundant ocean viruses

NASA Astrophysics Data System (ADS)

2016-09-01

Ocean microbes drive biogeochemical cycling on a global scale. However, this cycling is constrained by viruses that affect community composition, metabolic activity, and evolutionary trajectories. Owing to challenges with the sampling and cultivation of viruses, genome-level viral diversity remains poorly described and grossly understudied, with less than 1% of observed surface-ocean viruses known. Here we assemble complete genomes and large genomic fragments from both surface- and deep-ocean viruses sampled during the Tara Oceans and Malaspina research expeditions, and analyse the resulting ‘global ocean virome’ dataset to present a global map of abundant, double-stranded DNA viruses complete with genomic and ecological contexts. A total of 15,222 epipelagic and mesopelagic viral populations were identified, comprising 867 viral clusters (defined as approximately genus-level groups). This roughly triples the number of known ocean viral populations and doubles the number of candidate bacterial and archaeal virus genera, providing a near-complete sampling of epipelagic communities at both the population and viral-cluster level. We found that 38 of the 867 viral clusters were locally or globally abundant, together accounting for nearly half of the viral populations in any global ocean virome sample. While two-thirds of these clusters represent newly described viruses lacking any cultivated representative, most could be computationally linked to dominant, ecologically relevant microbial hosts. Moreover, we identified 243 viral-encoded auxiliary metabolic genes, of which only 95 were previously known. Deeper analyses of four of these auxiliary metabolic genes (dsrC, soxYZ, P-II (also known as glnB) and amoC) revealed that abundant viruses may directly manipulate sulfur and nitrogen cycling throughout the epipelagic ocean. This viral catalog and functional analyses provide a necessary foundation for the meaningful integration of viruses into ecosystem models where they act as key players in nutrient cycling and trophic networks.

Geochemical, Sulfur Isotopic Characteristics and Source Contributions of Size-Aggregated Aerosols Collected in Baring Head, New Zealand.

NASA Astrophysics Data System (ADS)

Li, J.; Michalski, G. M.; Davy, P.; Harvey, M.; Wilkins, B. P.; Katzman, T. L.

2017-12-01

Sulfate aerosols are critical to the climate, human health, and the hydrological cycle in the atmosphere, yet the sources of sulfate in aerosols are not completely understood. In this work, we evaluated the sources of sulfate in size-aggregated aerosols from the Southern Pacific Ocean and the land of New Zealand using geochemical and isotopic analyses. Aerosols were collected at Baring Head, New Zealand between 6/30/15 to 8/4/16 using two collectors, one only collects Southern Pacific Ocean derived aerosols (open-ocean collector), the other collects aerosols from both the ocean and the land (all-direction collector). Each collector is equipped with two filters to sample size-aggregated aerosols (fine aerosols: <0.5 um and coarse aerosols: 0.5-10 um). Our results show that fine and coarse aerosols show distinctive sulfate sources: sulfate in fine aerosols is a mixture of sea-salt sulfate ( 30%) and Non-Sea-Salt sulfate (NSS-SO42-, 70%), while coarse aerosols are dominated by sea-salt sulfate. However, some NSS-SO42- was also observed in coarse aerosols collected in summer, suggesting the presence of accumulation mode NSS-SO42- aerosols, which is possibly due to high summer biogenic DMS flux. The sources of sulfur in NSS-SO42- could be further determined by their d34S values. DMS emission is likely the sole sulfur source in the open-ocean collector as it shows constant DMS-like d34S signatures (15-18‰) throughout the year. Meanwhile, the d34S of NSS-SO42- in the all-direction collector display a seasonal trend: summer time d34S values are higher and DMS-like (15-18‰), indicating DMS emission is the dominant sulfur source; winter time d34S values are lower ( 6-12‰), therefore the sulfur is likely sourced from both DMS emission and terrestrial S input with low d34S values, such as volcanic activities, fossil fuel and wood burning.

Spatiotemporal trends in surface seawater CO2 in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Kealoha, A. K.; Shamberger, K.

2016-12-01

The Gulf of Mexico (GoM) contains many interconnected ecosystems intimately linked to regional economic stability through fisheries. Yet, numerous human pressures, including eutrophication-induced hypoxia and ocean acidification (OA), threaten the health of this large marine ecosystem. A comprehensive characterization of the drivers of GoM seawater CO2 cycling is required to assess interactions between these local stresses, global climate change, and OA. Several observational and modeling studies have been conducted in an effort to characterize CO2-system trends within the GoM. However, observational studies are limited to specific regions and time-frames, while modeled data are based on parameterizations that often cannot account for all the biogeochemical processes occurring in this complex system. Here, we present a compilation of approximately 510,000 continuous, underway measurements of sea surface temperature, salinity and seawater CO2, collected from 1996-2013 throughout the entire GoM. These data reveal distinct spatial and temporal CO2 trends that are driven primarily by temperature, Mississippi River outflow, biological productivity, and water circulation. For example, during the spring and summer, nutrient input from the Mississippi River stimulates biological productivity that drives surface seawater CO2 below atmospheric levels in the north-central GoM shelf waters. Although open ocean waters are generally a source of CO2 to the atmosphere in the summer, a unique combination of physical processes including high river discharge, offshore currents and eddy activity can transport low CO2 coastal water beyond the shelf causing vast areas, tens of thousands of square kilometers, of the open ocean to switch to a CO2 sink for several months. Since anthropogenic-driven climate change is expected to influence ocean circulation patterns, GoM CO2 source-sink characteristics and regional scale ocean carbon budgets may be altered in the future. We also combine discrete CO2 chemistry data collected in the Flower Garden Banks National Marine Sanctuary with historical underway data to provide insight into the connections between Gulf wide carbon variability and variability within these important coral reef ecosystems.

Monitoring terrestrial dissolved organic carbon export at land-water interfaces using remote sensing

NASA Astrophysics Data System (ADS)

Yu, Q.; Li, J.; Tian, Y. Q.

2017-12-01

Carbon flux from land to oceans and lakes is a crucial component of carbon cycling. However, this lateral carbon flow at land-water interface is often neglected in the terrestrial carbon cycle budget, mainly because observations of the carbon dynamics are very limited. Monitoring CDOM/DOC dynamics using remote sensing and assessing DOC export from land to water remains a challenge. Current CDOM retrieval algorithms in the field of ocean color are not simply applicable to inland aquatic ecosystems since they were developed for coarse resolution ocean-viewing imagery and less complex water types in open-sea. We developed a new semi-analytical algorithm, called SBOP (Shallow water Bio-Optical Properties algorithm) to adapt to shallow inland waters. SBOP was first developed and calibrated based on in situ hyperspectral radiometer data. Then we applied it to the Landsat-8 OLI images and evaluated the effectiveness of the multispectral images on inversion of CDOM absorption based on our field sampling at the Saginaw Bay in the Lake Huron. The algorithm performances (RMSE = 0.17 and R2 = 0.87 in the Saginaw Bay; R2 = 0.80 in the northeastern US lakes) is promising and we conclude the CDOM absorption can be derived from Landsat-8 OLI image in both optically deep and optically shallow waters with high accuracy. Our method addressed challenges on employing appropriate atmospheric correction, determining bottom reflectance influence for shallow waters, and improving for bio-optical properties retrieval, as well as adapting to both hyperspectral and the multispectral remote sensing imagery. Over 100 Landsat-8 images in Lake Huron, northeastern US lakes, and the Arctic major rivers were processed to understand the CDOM spatio-temporal dynamics and its associated driving factors.

The effect of widespread early aerobic marine ecosystems on methane cycling and the Great Oxidation

NASA Astrophysics Data System (ADS)

Daines, Stuart J.; Lenton, Timothy M.

2016-01-01

The balance of evidence suggests that oxygenic photosynthesis had evolved by 3.0-2.7 Ga, several hundred million years prior to the Great Oxidation ≈2.4 Ga. Previous work has shown that if oxygenic photosynthesis spread globally prior to the Great Oxidation, this could have supported widespread aerobic ecosystems in the surface ocean, without oxidising the atmosphere. Here we use a suite of models to explore the implications for carbon cycling and the Great Oxidation. We find that recycling of oxygen and carbon within early aerobic marine ecosystems would have restricted the balanced fluxes of methane and oxygen escaping from the ocean, lowering the atmospheric concentration of methane in the Great Oxidation transition and its aftermath. This in turn would have minimised any bi-stability of atmospheric oxygen, by weakening a stabilising feedback on oxygen from hydrogen escape to space. The result would have been a more reversible and probably episodic rise of oxygen at the Great Oxidation transition, consistent with existing geochemical evidence. The resulting drop in methane levels to ≈10 ppm is consistent with climate cooling at the time but adds to the puzzle of what kept the rest of the Proterozoic warm. A key test of the scenario of abundant methanotrophy in oxygen oases before the Great Oxidation is its predicted effects on the organic carbon isotope (δ13Corg) record. Our open ocean general circulation model predicts δC13org ≈ - 30 to -45‰ consistent with most data from 2.65 to 2.45 Ga. However, values of δC13org ≈ - 50 ‰ require an extreme scenario such as concentrated methanotroph production where shelf-slope upwelling of methane-rich water met oxic shelf water.

Volume 35, AMT-1 Cruise Report and Preliminary Results

NASA Technical Reports Server (NTRS)

Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor); Robins, David B.; Bale, Anthony J.; Moore, Gerald F.; Rees, Nigel W.; Gallienne, Christopher P.; Westbrooke, Anthony G.; Maranon, Emilio; Spooner, William H.;

Linking carbon and iron cycles by investigating transport, fate and mineralogy of iron-bearing colloids from peat-draining rivers - Scotland as model for high-latitude rivers

NASA Astrophysics Data System (ADS)

Wood, Deborah; Crocket, Kirsty; Brand, Tim; Stutter, Marc; Wilson, Clare; Schröder, Christian

2016-04-01

Linking carbon and iron cycles by investigating transport, fate and mineralogy of iron-bearing colloids from peat-draining rivers - Scotland as model for high-latitude rivers Wood, D.A¹, Crocket, K², Brand, T², Stutter, M³, Wilson, C¹ & Schröder, C¹ ¹Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA ²Scottish Association for Marine Science, University of the Highlands and Islands, Dunbeg, Oban, PA37 1QA ³James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH The biogeochemical iron cycle exerts significant control on the carbon cycle¹. Iron is a limiting nutrient in large areas of the world's oceans and its bioavailability controls CO2 uptake by marine photosynthesizing microorganisms. While atmospheric iron inputs to the open ocean have been extensively measured, global river inputs have likely been underestimated because most major world rivers exhibit extensive iron removal by flocculation and sedimentation during seawater mixing. Iron minerals and organic matter mutually stabilise each other², which results in a 'rusty carbon sink' in sediments³ on the one hand but may also enhance transport beyond the salinity gradient on the other. Humic-rich, high latitude rivers have a higher iron-carrying capacity⁴-⁶ but are underrepresented in iron flux calculations. The West Coast sea lochs in Scotland are fed by predominantly peatland drainage catchments, and the rivers entering the sea lochs carry a high load of organic matter. The short distance between many of these catchments and the coastal ocean facilitates source-to-sea research investigating transport, fate and mineralogy of iron-bearing colloids providing a good analogue for similar high latitude fjordic systems. We use SeaFAST+ICP-MS and Mössbauer spectroscopy to survey trace metal concentrations, with emphasis on iron concentrations, speciation and mineralogy, across salinity gradients. In combination with ultra-filtration techniques, this allows determination of the concentrations and chemical composition of different size fractions of iron-organic matter particles and colloids. We are developing new filtering and enrichment protocols to enable the use of Mössbauer spectroscopy in order to close a gap in the understanding of iron mineralogy in sub-micron particles. Here we will present results from a first sampling campaign in Loch Sunart and its tributaries. Acknowledgements: This is a MASTS-funded PhD project (GSS30). Preliminary work was supported by a SAGES PECRE grant to C.S., and a MASTS Visiting Fellowship award (VF41) to K.C. References: 1. Raiswell and Canfield (2012). The Iron Biogeochemical Cycle Past and Present. Geochemical Perspectives 1(1), 1-220. 2. Schröder et al. The biogeochemical iron cycle and astrobiology. Hyperfine Interactions in press. 3. Lalonde et al. (2012). Preservation of organic matter in sediments promoted by iron. Nature 483, 198-200. 4. Batchelli et al. (2010). Evidence for strong but dynamic iron-humic colloidal associations in humic-rich coastal waters. Environ. Sci. Technol., 44, 8485-8490. 5. Krachler et al. (2010). Relevance of peat-draining rivers for the riverine input of dissolved iron into the ocean. Sci. Total Environ., 408, 2402-2408. 6. Pokrovsky et al. (2014). Fate of colloids during estuarine mixing in the Arctic. Ocean Sci., 10, 107-125.

Modern Estimates of Global Water Cycle Fluxes

NASA Astrophysics Data System (ADS)

Rodell, M.; Beaudoing, H. K.; L'Ecuyer, T. S.; Olson, W. S.

2014-12-01

The goal of the first phase of the NASA Energy and Water Cycle Study (NEWS) Water and Energy Cycle Climatology project was to develop "state of the global water cycle" and "state of the global energy cycle" assessments based on data from modern ground and space based observing systems and data integrating models. Here we describe results of the water cycle assessment, including mean annual and monthly fluxes over continents and ocean basins during the first decade of the millennium. To the extent possible, the water flux estimates are based on (1) satellite measurements and (2) data-integrating models. A careful accounting of uncertainty in each flux was applied within a routine that enforced multiple water and energy budget constraints simultaneously in a variational framework, in order to produce objectively-determined, optimized estimates. Simultaneous closure of the water and energy budgets caused the ocean evaporation and precipitation terms to increase by about 10% and 5% relative to the original estimates, mainly because the energy budget required turbulent heat fluxes to be substantially larger in order to balance net radiation. In the majority of cases, the observed annual, surface and atmospheric water budgets over the continents and oceans close with much less than 10% residual. Observed residuals and optimized uncertainty estimates are considerably larger for monthly surface and atmospheric water budget closure, often nearing or exceeding 20% in North America, Eurasia, Australia and neighboring islands, and the Arctic and South Atlantic Oceans. The residuals in South America and Africa tend to be smaller, possibly because cold land processes are a non-issue. Fluxes are poorly observed over the Arctic Ocean, certain seas, Antarctica, and the Australasian and Indonesian Islands, leading to reliance on atmospheric analysis estimates. Other details of the study and future directions will be discussed.

The Impact of the Ocean Sulfur Cycle on Climate using the Community Earth System Model

NASA Astrophysics Data System (ADS)

Cameron-Smith, P. J.; Elliott, S. M.; Bergmann, D. J.; Branstetter, M. L.; Chuang, C.; Erickson, D. J.; Jacob, R. L.; Maltrud, M. E.; Mirin, A. A.

2011-12-01

Chemical cycling between the various Earth system components (atmosphere, biosphere, land, ocean, and sea-ice) can cause positive and negative feedbacks on the climate system. The long-standing CLAW/GAIA hypothesis proposed that global warming might stimulate increased production of dimethyl sulfide (DMS) by plankton in the ocean, which would then provide a negative climate feedback through atmospheric oxidation of the DMS to sulfate aerosols that reflect sunlight directly, and indirectly by affecting clouds. Our state-of-the-art earth system model (CESM with an ocean sulfur cycle and atmospheric chemistry) shows increased production of DMS over the 20th century by plankton, particularly in the Southern Ocean and Equatorial Pacific, which leads to modest cooling from direct reflection of sunlight in those regions. This suggests the possibility of local climate change mitigation by the plankton species that produce DMS. Part of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Wind energy input into the upper ocean over a lengthening open water season

NASA Astrophysics Data System (ADS)

Mahoney, A. R.; Rolph, R.; Walsh, J. E.

2017-12-01

Wind energy input into the ocean has important consequences for upper ocean mixing, heat and gas exchange, and air-sea momentum transfer. In the Arctic, the open water season is increasing and extending further into the fall storm season, allowing for more wind energy input into the water column. The rate at which the delayed freeze-up timing extends into fall storm season is an important metric to evaluate because the expanding overlap between the open water period and storm season could contribute a significant amount of wind energy into the water column in a relatively short period of time. We have shown that time-integrated wind speeds over open water in the Chukchi Sea and southern Beaufort region have increased since 1979 through 2014. An integrated wind energy input value is calculated for each year in this domain over the open water season, as well as for periods over partial concentrations of ice cover. Spatial variation of this integrated wind energy is shown along the Alaskan coastline, which can have implications for different rates of coastal erosion. Spatial correlation between average wind speed over open water and open water season length from 1979-2014 show positive values in the southern Beaufort, but negative values in the northern Chukchi. This suggests possible differences in the role of the ocean on open water season length depending on region. We speculate that the warm Pacific water outflow plays a more dominant role in extending the open water season length in the northern Chukchi when compared to the southern Beaufort, and might help explain why we can show there is a relatively longer open water season length there. The negative and positive correlations in wind speeds over open water and open water season length might also be explained by oceanic changes tending to operate on longer timescales than the atmosphere. Seasonal timescales of wind events such as regional differences in overlap of the extended open water season due to regional differences in delayed freeze-up into the fall storm season are also investigated. In addition, we have shown that the increased integrated wind energy input over open water values are more a result of the increased open water season length, rather than the increase in wind speeds over open water.

Terrestrial water cycle induced meridional overturning circulation variability over the Atlantic Ocean

NASA Astrophysics Data System (ADS)

Hsu, C. W.; Velicogna, I.

2016-12-01

Terrestrial water cycle has a significant role in the long-term changes of Atlantic meridional overturning circulation (AMOC). With the fresh water input over the ocean from the river runoff or ice melting at the higher latitude, AMOC transport has been predicted to slow down at the end of the century. We compare ocean bottom pressure measured from the GRACE satellite data with the conventional density derived transport observations from the RAPID MOC/MOCHA array to study the impact of the terrestrial water cycle on the seasonal and inter annual AMOC variability detected by the RAPID MOC/MOCHA array observations. We propose that the observed short-term variability is due to coupling of wind driven and terrestrial water cycle changes. We show that the proposed mechanism explains a significant portion of the transport variance and we present new possible mechanism that can explain the residual transport signal in AMOC.

Chemical Oceanography and the Marine Carbon Cycle

NASA Astrophysics Data System (ADS)

Emerson, Steven; Hedges, John

The principles of chemical oceanography provide insight into the processes regulating the marine carbon cycle. The text offers a background in chemical oceanography and a description of how chemical elements in seawater and ocean sediments are used as tracers of physical, biological, chemical and geological processes in the ocean. The first seven chapters present basic topics of thermodynamics, isotope systematics and carbonate chemistry, and explain the influence of life on ocean chemistry and how it has evolved in the recent (glacial-interglacial) past. This is followed by topics essential to understanding the carbon cycle, including organic geochemistry, air-sea gas exchange, diffusion and reaction kinetics, the marine and atmosphere carbon cycle and diagenesis in marine sediments. Figures are available to download from www.cambridge.org/9780521833134. Ideal as a textbook for upper-level undergraduates and graduates in oceanography, environmental chemistry, geochemistry and earth science and a valuable reference for researchers in oceanography.

Life Cycle of the Salmon. Ocean Related Curriculum Activities.

ERIC Educational Resources Information Center

Tarabochia, Kathy

The ocean affects all of our lives. Therefore, awareness of and information about the interconnections between humans and oceans are prerequisites to making sound decisions for the future. Project ORCA (Ocean Related Curriculum Activities) has developed interdisciplinary curriculum materials designed to meet the needs of students and teachers…

Diurnal variability in carbon and nitrogen pools within Chesapeake Bay and northern Gulf of Mexico: implications for future ocean color satellite sensors

NASA Astrophysics Data System (ADS)

Mannino, A.; Novak, M. G.; Tzortziou, M.; Salisbury, J.

2016-02-01

Relative to their areal extent, estuaries and coastal ocean ecosystems contribute disproportionately more to global biogeochemical cycling of carbon, nitrogen and other elements compared to the open ocean. Applying ocean color satellite data to study biological and biogeochemical processes within coastal ecosystems is challenging due to the complex mixtures of aquatic constituents derived from terrestrial, anthropogenic, and marine sources, human-impacted atmospheric properties, presence of clouds during satellite overpass, fine-scale spatial gradients, and time-varying processes on diurnal scales that cannot be resolved with current sensors. On diurnal scales, biological, photochemical, and biogeochemical processes are regulated by the variation in solar radiation. Other physical factors, such as tides, river discharge, estuarine and coastal ocean circulation, wind-driven mixing, etc., impart further variability on biological and biogeochemical processes on diurnal to multi-day time scales. Efforts to determine the temporal frequency required from a NASA GEO-CAPE ocean color satellite sensor to discern diurnal variability C and N stocks, fluxes and productivity culminated in field campaigns in the Chesapeake Bay and northern Gulf of Mexico. Near-surface drogues were released and tracked in quasi-lagrangian space to monitor hourly changes in community production, C and N stocks, and optical properties. While only small diurnal changes were observed in dissolved organic carbon (DOC) and colored dissolved organic matter (CDOM) absorption in Chesapeake Bay, substantial variation in particulate organic carbon (POC) and nitrogen (PN), chlorophyll-a, and inorganic nitrogen (DIN) were measured. Similar or greater diurnal changes in POC, PN, chlorophyll-a and DIN were found in Gulf of Mexico nearshore and offshore sites. These results suggest that satellite observations at hourly frequency are desirable to capture diurnal variability in carbon and nitrogen stocks, fluxes and productivity within coastal ecosystems.

Sustained eruptions on Enceladus explained by turbulent dissipation in tiger stripes

NASA Astrophysics Data System (ADS)

Kite, Edwin S.; Rubin, Allan M.

2016-04-01

Spacecraft observations suggest that the plumes of Saturn’s moon Enceladus draw water from a subsurface ocean, but the sustainability of conduits linking ocean and surface is not understood. Observations show eruptions from “tiger stripe” fissures that are sustained (although tidally modulated) throughout each orbit, and since the 2005 discovery of the plumes. Peak plume flux lags peak tidal extension by ˜1 rad, suggestive of resonance. Here, we show that a model of the tiger stripes as tidally flexed slots that puncture the ice shell can simultaneously explain the persistence of the eruptions through the tidal cycle, the phase lag, and the total power output of the tiger stripe terrain, while suggesting that eruptions are maintained over geological timescales. The delay associated with flushing and refilling of O(1)-m-wide slots with ocean water causes erupted flux to lag tidal forcing and helps to buttress slots against closure, while tidally pumped in-slot flow leads to heating and mechanical disruption that staves off slot freezeout. Much narrower and much wider slots cannot be sustained. In the presence of long-lived slots, the 106-y average power output of the tiger stripes is buffered by a feedback between ice melt-back and subsidence to O(1010) W, which is similar to observed power output, suggesting long-term stability. Turbulent dissipation makes testable predictions for the final flybys of Enceladus by Cassini. Our model shows how open connections to an ocean can be reconciled with, and sustain, long-lived eruptions. Turbulent dissipation in long-lived slots helps maintain the ocean against freezing, maintains access by future Enceladus missions to ocean materials, and is plausibly the major energy source for tiger stripe activity.

Lagrangian analysis of multi-satellite data in support of open ocean Marine Protected Area design

NASA Astrophysics Data System (ADS)

Della Penna, Alice; Koubbi, Philippe; Cotté, Cedric; Bon, Cécile; Bost, Charles-André; d'Ovidio, Francesco

2017-06-01

Compared to ecosystem conservation in territorial seas, protecting the open ocean has peculiar geopolitical, economic and scientific challenges. One of the major obstacle is defining the boundary of an open ocean Marine Protected Area (MPA). In contrast to coastal ecosystems, which are mostly constrained by topographic structures fixed in time, the life of marine organisms in the open ocean is entrained by fluid dynamical structures like eddies and fronts, whose lifetime occurs on ecologically-relevant timescales. The position of these highly dynamical structures can vary interannually by hundreds of km, and so too will regions identified as ecologically relevant such as the foraging areas of marine predators. Thus, the expected foraging locations suggested from tracking data cannot be directly extrapolated beyond the year in which the data were collected. Here we explore the potential of Lagrangian methods applied to multisatellite data as a support tool for a MPA proposal by focusing on the Crozet archipelago oceanic area (Indian Sector of the Southern Ocean). By combining remote sensing with biologging information from a key marine top predator (Eudyptes chrysolophus, or Macaroni penguin) of the Southern Ocean foodweb, we identify a highly dynamic branch of the Subantarctic front as a foraging hotspot. By tracking this feature in historical satellite data (1993-2012) we are able to extrapolate the position of this foraging ground beyond the years in which tracking data are available and study its spatial variability.

Pelagic functional group modeling: Progress, challenges and prospects

NASA Astrophysics Data System (ADS)

Hood, Raleigh R.; Laws, Edward A.; Armstrong, Robert A.; Bates, Nicholas R.; Brown, Christopher W.; Carlson, Craig A.; Chai, Fei; Doney, Scott C.; Falkowski, Paul G.; Feely, Richard A.; Friedrichs, Marjorie A. M.; Landry, Michael R.; Keith Moore, J.; Nelson, David M.; Richardson, Tammi L.; Salihoglu, Baris; Schartau, Markus; Toole, Dierdre A.; Wiggert, Jerry D.

2006-03-01

In this paper, we review the state of the art and major challenges in current efforts to incorporate biogeochemical functional groups into models that can be applied on basin-wide and global scales, with an emphasis on models that might ultimately be used to predict how biogeochemical cycles in the ocean will respond to global warming. We define the term "biogeochemical functional group" to refer to groups of organisms that mediate specific chemical reactions in the ocean. Thus, according to this definition, "functional groups" have no phylogenetic meaning—these are composed of many different species with common biogeochemical functions. Substantial progress has been made in the last decade toward quantifying the rates of these various functions and understanding the factors that control them. For some of these groups, we have developed fairly sophisticated models that incorporate this understanding, e.g. for diazotrophs (e.g. Trichodesmium), silica producers (diatoms) and calcifiers (e.g. coccolithophorids and specifically Emiliania huxleyi). However, current representations of nitrogen fixation and calcification are incomplete, i.e., based primarily upon models of Trichodesmium and E. huxleyi, respectively, and many important functional groups have not yet been considered in open-ocean biogeochemical models. Progress has been made over the last decade in efforts to simulate dimethylsulfide (DMS) production and cycling (i.e., by dinoflagellates and prymnesiophytes) and denitrification, but these efforts are still in their infancy, and many significant problems remain. One obvious gap is that virtually all functional group modeling efforts have focused on autotrophic microbes, while higher trophic levels have been completely ignored. It appears that in some cases (e.g., calcification), incorporating higher trophic levels may be essential not only for representing a particular biogeochemical reaction, but also for modeling export. Another serious problem is our tendency to model the organisms for which we have the most validation data (e.g., E. huxleyi and Trichodesmium) even when they may represent only a fraction of the biogeochemical functional group we are trying to represent. When we step back and look at the paleo-oceanographic record, it suggests that oxygen concentrations have played a central role in the evolution and emergence of many of the key functional groups that influence biogeochemical cycles in the present-day ocean. However, more subtle effects are likely to be important over the next century like changes in silicate supply or turbulence that can influence the relative success of diatoms versus dinoflagellates, coccolithophorids and diazotrophs. In general, inferences drawn from the paleo-oceanographic record and theoretical work suggest that global warming will tend to favor the latter because it will give rise to increased stratification. However, decreases in pH and Fe supply could adversely impact coccolithophorids and diazotrophs in the future. It may be necessary to include explicit dynamic representations of nitrogen fixation, denitrification, silicification and calcification in our models if our goal is predicting the oceanic carbon cycle in the future, because these processes appear to play a very significant role in the carbon cycle of the present-day ocean and they are sensitive to climate change. Observations and models suggest that it may also be necessary to include the DMS cycle to predict future climate, though the effects are still highly uncertain. We have learned a tremendous amount about the distributions and biogeochemical impact of bacteria in the ocean in recent years, yet this improved understanding has not yet been incorporated into many of our models. All of these considerations lead us toward the development of increasingly complex models. However, recent quantitative model intercomparison studies suggest that continuing to add complexity and more functional groups to our ecosystem models may lead to decreases in predictive ability if the models are not properly constrained with available data. We also caution that capturing the present-day variability tells us little about how well a particular model can predict the future. If our goal is to develop models that can be used to predict how the oceans will respond to global warming, then we need to make more rigorous assessments of predictive skill using the available data.

Decreased calcification in the Southern Ocean over the satellite record

NASA Astrophysics Data System (ADS)

Freeman, Natalie M.; Lovenduski, Nicole S.

2015-03-01

Widespread ocean acidification is occurring as the ocean absorbs anthropogenic carbon dioxide from the atmosphere, threatening marine ecosystems, particularly the calcifying plankton that provide the base of the marine food chain and play a key role within the global carbon cycle. We use satellite estimates of particulate inorganic carbon (PIC), surface chlorophyll, and sea surface temperature to provide a first estimate of changing calcification rates throughout the Southern Ocean. From 1998 to 2014 we observe a 4% basin-wide reduction in summer calcification, with ˜9% reductions in large regions (˜1 × 106 km2) of the Pacific and Indian sectors. Southern Ocean trends are spatially heterogeneous and primarily driven by changes in PIC concentration (suspended calcite), which has declined by ˜24% in these regions. The observed decline in Southern Ocean calcification and PIC is suggestive of large-scale changes in the carbon cycle and provides insight into organism vulnerability in a changing environment.

Rapid nitrous oxide cycling in the suboxic ocean

NASA Astrophysics Data System (ADS)

Babbin, Andrew R.; Bianchi, Daniele; Jayakumar, Amal; Ward, Bess B.

2015-06-01

Nitrous oxide (N2O) is a powerful greenhouse gas and a major cause of stratospheric ozone depletion, yet its sources and sinks remain poorly quantified in the oceans. We used isotope tracers to directly measure N2O reduction rates in the eastern tropical North Pacific. Because of incomplete denitrification, N2O cycling rates are an order of magnitude higher than predicted by current models in suboxic regions, and the spatial distribution suggests strong dependence on both organic carbon and dissolved oxygen concentrations. Furthermore, N2O turnover is 20 times higher than the net atmospheric efflux. The rapid rate of this cycling coupled to an expected expansion of suboxic ocean waters implies future increases in N2O emissions.

Nutrient and Trace Metal Controls on Alkaline Phosphatase in the Subtropical Ocean: Insights from Bioassays and Gene Expression

NASA Astrophysics Data System (ADS)

Mahaffey, C.; Reynolds, S.; Davis, C. E.; Lohan, M. C.

2016-02-01

Phosphorus is an essential nutrient for all life on earth. In the ocean, the most bioavailable form of phosphorus is inorganic phosphate, but in the extensive subtropical gyres, phosphate concentrations can be chronically low in the surface ocean and limit biological activity. In response to phosphate limitation, organisms produce phosphohydrolytic enzymes, such as alkaline phosphatases (AP), that enable them to utilize the more replete dissolved organic phosphorus (DOP) pool to meet their cellular phosphorus demands. Synthesis of data from the surface ocean from 14 open ocean studies reveals an inverse hyperbolic relationship between phosphate and AP, where AP is significantly induced at phosphate concentrations below 50 nM and DOP concentrations decrease as AP increases. AP activity was significantly higher in the subtropical Atlantic compared to the subtropical Pacific Ocean, even over the same low phosphate concentration range (0 to 50 nM). While the phosphate concentration may have a first order control on the rates of AP, we demonstrate that other factors influence AP activity. AP are metalloenzymes and zinc and iron are co-factors of the AP proteins PhoA and PhoX, respectively. Using bioassay experiments, we show that the addition of Saharan dust and zinc significantly increases the rate of AP. To our knowledge, our results are the first direct field-based evidence that AP activity is limited by zinc in the subtropical ocean. In colonies of nitrogen fixer, Trichodesmium, we found enhanced expression of the phoA gene in a region of elevated zinc concentrations and enhanced expression of the phoX gene in a region of elevated iron concentrations around the intertropical convergence zone. Our study highlights the potential link between the phosphorus cycle and trace metals, specifically zinc and iron, and implies that there is potential for zinc-phosphorus and iron-phosphorus co-limitation in the ocean via AP.

FixO3 : Early progress towards Open Ocean observatory Data Management Harmonisation

NASA Astrophysics Data System (ADS)

Pagnani, Maureen; Huber, Robert; Lampitt, Richard

2014-05-01

Since 2002 there has been a sustained effort, supported as European framework projects, to harmonise both the technology and the data management of Open Ocean fixed observatories run by European nations. FixO3 started in September 2013, and for 4 years will coordinate the convergence of data management best practice across a constellation of moorings in the Atlantic, in both hemispheres, and in the Mediterranean. To ensure the continued existence of these unique sources of oceanographic data as sustained observatories it is vital to improve access to the data collected, both in terms of methods of presentation, real-time availability, long-term archiving and quality assurance. The data management component of FixO3 will improve access to marine observatory data by harmonizing data management standards and workflows covering the complete life cycle of data from real time data acquisition to long-term archiving. Legal and data policy aspects will be examined to identify transnational barriers to open-access to marine observatory data. A harmonised FixO3 data policy is being synthesised from the partner's existing policies, which will overcome the identified barriers, and provide a formal basis for data exchange between FixO3 infrastructures. Presently, the interpretation and implementation of accepted standards has considerable incompatibilities within the observatory community, and these different approaches will be unified into the FixO3 approach. Further, FixO3 aims to harmonise data management and standardisation efforts with other European and international marine data and observatory infrastructures. The FixO3 synthesis will build on the standards established in other European infrastructures such as EDMONET, SEADATANET, PANGAEA, EuroSITES (European contribution to JCOMMP OceanSITES programme), and MyOcean (the Marine Core Service for GMES) infrastructures as well as relevant international infrastructures and data centres such as the ICOS Ocean Thematic Centre. The data management efforts are central to FixO3. Combined with the procedural and technological harmonisation, tackled in separate work packages, the FixO3 network of observatories will efficiently and cost effectively provide a consistent resource of quality controlled accessible oceanographic data The project website www.fixo3.eu is being developed as both a data showcase and single distribution point, and with database driven tools will enable the sharing of information between the observatories in the most smart and cost effective way. The network of knowledge built throughout the project will become a legacy resource that will ensure access to the unique ensemble data sets only achievable at these key observatories.

Oxygen minimum zones (OMZs) in the modern ocean

NASA Astrophysics Data System (ADS)

Paulmier, A.; Ruiz-Pino, D.

2009-03-01

In the modern ocean, oxygen minimum zones (OMZs) are potential traces of a primitive ocean in which Archean bacteria lived and reduced chemical anomalies occurred. But OMZs are also keys to understanding the present unbalanced nitrogen cycle and the oceans’ role on atmospheric greenhouse control. OMZs are the main areas of nitrogen loss (as N 2, N 2O) to the atmosphere through denitrification and anammox, and could even indirectly mitigate the oceanic biological sequestration of CO 2. It was recently hypothesized that OMZs are going to spread in the coming decades as a consequence of global climate change. Despite an important OMZ role for the origin of marine life and for the biogeochemical cycles of carbon and nitrogen, there are some key questions on the structure of OMZs at a global scale. There is no agreement concerning the threshold in oxygen that defines an OMZ, and the extent of an OMZ is often evaluated by denitrification criteria which, at the same time, are O 2-dependent. Our work deals with the identification of each OMZ, the evaluation of its extent, volume and vertical structure, the determination of its seasonality or permanence and the comparison between OMZs and denitrification zones at a global scale. The co-existence in the OMZ of oxic (in its boundaries) and suboxic (even anoxic, in its core) conditions involves rather complex biogeochemical processes such as strong remineralization of the organic matter, removal of nitrate and release of nitrite. The quantitative OMZ analysis is focused on taking into account the whole water volume under the influence of an OMZ and adapted to the study of the specific low oxygen biogeochemical processes. A characterization of the entire structure for the main and most intense OMZs (O 2 < 20 μM reaching 1 μM in the core) is proposed based on a previously published CRIO criterion from the eastern South Pacific OMZ and including a large range of O 2 concentrations. Using the updated global WOA2005 O 2 climatology, the four known tropical OMZs in the open ocean have been described: the Eastern South Pacific and Eastern Tropical North Pacific, in the Pacific Ocean; the Arabian Sea and Bay of Bengal, in the Indian Ocean. Moreover, the Eastern Sub-Tropical North Pacific (25-52°N) has been identified as a lesser known permanent deep OMZ. Two additional seasonal OMZs at high latitude have also been identified: the West Bering Sea and the Gulf of Alaska. The total surface of the permanent OMZs is 30.4 millions of km 2 (∼8% of the total oceanic area), and the volume of the OMZ cores (10.3 millions of km 3) corresponds to a value ∼7 times higher than previous evaluations. The volume of the OMZ cores is about three times larger than that of the associated denitrification zone, here defined as NMZ (‘nitrate deficit or NDEF > 10 μM’ maximum zone). The larger OMZ, relative to the extent of denitrification zone, suggests that the unbalanced nitrogen cycle on the global scale could be more intense than previously recognized and that evaluation of the OMZ from denitrification could underestimate their extent.

Assessing the Feasibility and Risks of Using Wave-Driven Upwelling Pumps to Enhance the Biological Sequestration of Carbon in Open Oceans

NASA Astrophysics Data System (ADS)

White, A.; Bjorkman, K.; Grabowski, E.; Letelier, R. M.; Poulos, S.; Watkins, B.; Karl, D. M.

2008-12-01

In 1976, John D. Isaacs proposed to use wave energy to pump cold and nutrient-rich deep water into the sunlit surface layers. The motivation for this endeavor has taken many forms over the years, from energy production to fueling aquaculture to the more recent suggestion that artificial upwelling could be used to stimulate primary productivity and anthropogenic carbon sequestration in oligotrophic regions of the ocean. However, the potential for biological carbon sequestration in response to upwelling will depend on the concentration of nutrients relative to that of dissolved inorganic carbon in the water being upwelled and on the response of the marine microbial assemblage to this nutrient enrichment. In June 2008, we tested a commercially available wave pump in the vicinity of Station ALOHA, north of Oahu, Hawaii in order to assess the logistics of at-sea deployment and the survivability of the equipment in the open ocean. Our engineering test was also designed to evaluate a recently published hypothesis (Karl and Letelier, 2008, Marine Ecology Progress Series) that upwelling of water containing excess phosphate relative to nitrogen compared to the canonical "Redfield" molar ratio of 16N:1P, would generate a two-phased phytoplankton bloom and enhance carbon sequestration. In this presentation, we analyze the results of this field test within the context of pelagic biogeochemical cycles. Furthermore, we discuss the deployment of a 300m wave pump, efforts to sample a biochemical response, the engineering challenges faced and the practical and ethical implications of these results for future experiments aimed at stimulating the growth of phytoplankton in oligotrophic regions.

Characterizing Marine Habitat Space on a Snowball Earth with a 3D Global Climate Model

NASA Astrophysics Data System (ADS)

Sohl, L. E.; Chandler, M. A.; Lingo, F.

2016-12-01

The impact of long-term, severe cold conditions during the Neoproterozoic glacial events ( 715-635 Ma) on the origins and evolution of metazoans remains unclear, even as recent paleobiological analyses lend support to the notion that metazoans appeared and diversified long before their first definitive appearance in the Ediacaran fossil record (Cohen and MacDonald, Paleobiology 41:610, 2015; Spence et al., Sedimentology 63:253, 2016). Cumulative geologic evidence for active hydrologic cycling and the presence of open waters in near-shore environments suggests that a fully ice-covered ocean (a "hard" Snowball) at this time in Earth history is unlikely, opening up the possibility that life did more than just survive in a few localized refugia. Here we present results from 3D climate simulations of a Neoproterozoic Snowball Earth, using the NASA/GISS global climate model (GCM) ModelE2 to explore oceanographic conditions during the Sturtian glacial interval. The GCM was allowed to run to an equilibrium state, with forcings (reduced solar luminosity, CO2) that yielded a stable sea ice front at approximately 30 degrees latitude. Among the prognostic variables available for analysis are ocean temperature and salinity gradients in three dimensions, and rates and regions of vertical mixing that enhance the distribution of heat and nutrients in the oceans. Using information derived from physical limitations of certain modern organisms likely related to early complex life (e.g., demosponges) we review the geographic distribution of potential habitat space. Our preliminary analysis suggests that salinity rather than temperature could be a key constraint on the distribution of complex life, a contrast to the expectation of temperature as a key limiting factor.

Fixed point Open Ocean Observatory network (FixO3): Multidisciplinary observations from the air-sea interface to the deep seafloor

NASA Astrophysics Data System (ADS)

Lampitt, Richard; Cristini, Luisa

2014-05-01

The Fixed point Open Ocean Observatory network (FixO3) seeks to integrate the 23 European open ocean fixed point observatories and to improve access to these key installations for the broader community. These will provide multidisciplinary observations in all parts of the oceans from the air-sea interface to the deep seafloor. Coordinated by the National Oceanography Centre, UK, FixO3 builds on the significant advances achieved through the previous Europe-funded FP7 programmes EuroSITES, ESONET and CARBOOCEAN. Started in September 2013 with a budget of 7 Million Euros over 4 years the project has 29 partners drawn from academia, research institutions and SME's. In addition 12 international experts from a wide range of disciplines comprise an Advisory Board. On behalf of the FixO3 Consortium, we present the programme that will be achieved through the activities of 12 Work Packages: 1. Coordination activities to integrate and harmonise the current procedures and processes. Strong links will be fostered with the wider community across academia, industry, policy and the general public through outreach, knowledge exchange and training. 2. Support actions to offer a) free access to observatory infrastructures to those who do not have such access, and b) free and open data services and products. 3. Joint research activities to innovate and enhance the current capability for multidisciplinary in situ ocean observation. Support actions include Transnational Access (TNA) to FixO3 infrastructure, meaning that European organizations can apply to free-of-charge access to the observatories for research and testing in two international calls during the project lifetime. The first call for TNA opens in summer 2014. More information can be found on FixO3 website (www.fixo3.eu/). Open ocean observation is currently a high priority for European marine and maritime activities. FixO3 will provide important data on environmental products and services to address the Marine Strategy Framework Directive and in support of the European Integrated Maritime Policy. The FixO3 network will provide free and open access to in situ fixed point data of the highest quality. It will provide a strong integrated framework of open ocean facilities in the Atlantic from the Arctic to the Antarctic and throughout the Mediterranean, enabling an integrated, regional and multidisciplinary approach to understand natural and anthropogenic change in the ocean.

Sources and levels of ambient ocean sound near the Antarctic Peninsula.

PubMed

Dziak, Robert P; Bohnenstiehl, DelWayne R; Stafford, Kathleen M; Matsumoto, Haruyoshi; Park, Minkyu; Lee, Won Sang; Fowler, Matt J; Lau, Tai-Kwan; Haxel, Joseph H; Mellinger, David K

2015-01-01

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10-20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue (Balaenoptera musculus) and fin (B. physalus) whales also dominate the long-term spectra records in the 15-28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean.

Sources and Levels of Ambient Ocean Sound near the Antarctic Peninsula

PubMed Central

Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Stafford, Kathleen M.; Matsumoto, Haruyoshi; Park, Minkyu; Lee, Won Sang; Fowler, Matt J.; Lau, Tai-Kwan; Haxel, Joseph H.; Mellinger, David K.

2015-01-01

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10–20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue (Balaenoptera musculus) and fin (B. physalus) whales also dominate the long-term spectra records in the 15–28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean. PMID:25875205

Geographical Distribution and Sources of Nutrients in Atmospheric Aerosol Over the Pacific Ocean

NASA Astrophysics Data System (ADS)

Uematsu, M.

2016-12-01

The Pacific Ocean, the world's largest (occupying about 30% of the Earth's total surface area) has several distinguishing biogeochemical features. In the western Pacific, dust particles originating from arid and semi-arid regions in Asia and Australia are transported to the north and south, respectively. Biomass burning emissions from Southeast Asia are exported to the tropical Pacific, and anthropogenic substances flowing out of Asia and Eurasia spread both regionally and globally. Over high primary productive areas such as the subarctic North Pacific, the equatorial Pacific and the Southern Ocean, biogenic gasses are released to the atmosphere and transported to other areas. These processes may affect cloud and rainfall patterns, air quality, and the radiative balance of downwind regions. The deposition of atmospheric aerosols containing iron and other essential nutrients is important for biogeochemical cycles in the oceans because this source of nutrients helps sustain primary production and affects food-web structure; these effects in turn influence the chemical properties of marine atmosphere. From an atmospheric chemistry standpoint, sea-salt aerosols produced by strong winds and marine biogenic gases emitted from highly productive waters affect the physicochemical characteristics of marine aerosols. As phytoplankton populations are patchy and atmospheric processes sporadic, the interactions between atmospheric chemical constituents and marine biota vary for different regions as well as seasonally and over longer timescales. To address these and other emerging issues, and more generally to better understand the important biogeochemical processes and interactions occurring over the open oceans, more long-term recurrent research cruises with standardized atmospheric shipboard measurements will be needed in the future.

Causes of strong ocean heating during glacial periods

NASA Astrophysics Data System (ADS)

Zimov, N.; Zimov, S. A.

2013-12-01

During the last deglaciation period, the strongest climate changes occurred across the North Atlantic regions. Analyses of borehole temperatures from the Greenland ice sheet have yielded air temperature change estimates of 25°C over the deglaciation period (Dahl-Jensen et al. 1998). Such huge temperature changes cannot currently be explained in the frames of modern knowledge about climate. We propose that glacial-interglacial cycles are connected with gradual warming of ocean interior waters over the course of glaciations and quick transport of accumulated heat from ocean to the atmosphere during the deglaciation periods. Modern day ocean circulation is dominated by thermal convection with cold waters subsiding in the Northern Atlantic and filling up the ocean interior with cold and heavy water. However during the glaciation thermal circulation stopped and ocean circulation was driven by 'haline pumps' -Red and Mediterranean seas connected with ocean with only narrow but deep straights acts as evaporative basins, separating ocean water into fresh water which returns to the ocean surface (precipitation) and warm but salty, and therefore heavy, water which flows down to the ocean floor. This haline pump is stratifying the ocean, allowing warmer water locate under the colder water and thus stopping thermal convection in the ocean. Additional ocean interior warming is driven by geothermal heat flux and decomposition of organic rain. To test the hypothesis we present simple ocean box model that describes thermohaline circulation in the World Ocean. The first box is the Red and Mediterranean sea, the second is united high-latitude seas, the third is the ocean surface, and the fourth the ocean interior. The volume of these water masses and straight cross-sections are taken to be close to real values. We have accepted that the exchange of water between boxes is proportional to the difference in water density in these boxes, Sun energy inputs to the ocean and sea surface are taken as constant. Energy income to the interior box from the geothermal heat flux is also taken as constant. Even though energy inputs are taken as constants, the model manages to recreate the glacial-interglacial cycles. In the glacial periods only haline circulation takes place, the ocean is strongly stratified, and the interior box accumulates heat, while high-latitudes accumulate ice. 112,000 years after glaciation starts, water density on the ocean bottom becomes equal to the density of water in high-latitude seas, strong thermal convection take place, and the ocean quickly (within 14,600 years) releases the heat. The magnitude and duration of such cycles correspond with magnitudes and durations reconstructed for actual glacial-interglacial cycles. From the proposed mechanism it follows that during the glaciations it is likely that the Arctic Ocean was a big reservoir of isotopically light fresh ice. If in a glacial period, the World Ocean were half filled with warm water from the Red Sea and bioproductivity of the ocean declined because of the slow circulation, then carbon storage within the ocean reservoir would decline by ~2000 Pg (10^15 g) of carbon.

Coplanar polychlorinated biphenyl congeners in shark livers from the north-western African Atlantic ocean

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serrano, R.; Fernandez, M.A.; Hernandez, L.M.

1997-01-01

Polychlorinated biphenyls have been widely used by industry throughout the world since 1930. Although their use has been banned in many countries since the late 1970s, they still represent an important class of priority pollutants due to their persistence. Most open uses of these chemicals have been severely curtailed in industrialized nations, but a considerable fraction of past productions is probably still cycling in the ecosphere. In recent years, attention has been focused on the toxicity of PCBs, especially of those congeners showing similar toxicity as the polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDFs). It has been shown that PCB congeners`more » toxicity largely depends on the chlorine substitution pattern. The most toxic PCB cogeners are those with two para chlorines, at least two meta chlorines and 0-2 ortho chlorines. These so-called {open_quotes}coplanar{close_quotes} (non- mono- and di-ortho) PCB cogeners are able to obtain planar conformation. Recently, toxic equivalence factors have been assigned to coplanar PCBs. Thus determination of individual PCB cogeners is important for evaluating the toxic potentials of PCB residues in, for example, wildlife. This paper presents preliminary results of a study looking at levels of PCB congeners, including coplanar ones, in the liver of six shark species, collected in the North African Atlantic Ocean. 15 refs., 2 figs., 2 tabs.« less

An Analytical Framework for the Steady State Impact of Carbonate Compensation on Atmospheric CO2

NASA Astrophysics Data System (ADS)

Omta, Anne Willem; Ferrari, Raffaele; McGee, David

2018-04-01

The deep-ocean carbonate ion concentration impacts the fraction of the marine calcium carbonate production that is buried in sediments. This gives rise to the carbonate compensation feedback, which is thought to restore the deep-ocean carbonate ion concentration on multimillennial timescales. We formulate an analytical framework to investigate the impact of carbonate compensation under various changes in the carbon cycle relevant for anthropogenic change and glacial cycles. Using this framework, we show that carbonate compensation amplifies by 15-20% changes in atmospheric CO2 resulting from a redistribution of carbon between the atmosphere and ocean (e.g., due to changes in temperature, salinity, or nutrient utilization). A counterintuitive result emerges when the impact of organic matter burial in the ocean is examined. The organic matter burial first leads to a slight decrease in atmospheric CO2 and an increase in the deep-ocean carbonate ion concentration. Subsequently, enhanced calcium carbonate burial leads to outgassing of carbon from the ocean to the atmosphere, which is quantified by our framework. Results from simulations with a multibox model including the minor acids and bases important for the ocean-atmosphere exchange of carbon are consistent with our analytical predictions. We discuss the potential role of carbonate compensation in glacial-interglacial cycles as an example of how our theoretical framework may be applied.

Impact of the ocean diurnal cycle on the North Atlantic mean sea surface temperatures in a regionally coupled model

NASA Astrophysics Data System (ADS)

Guemas, Virginie; Salas-Mélia, David; Kageyama, Masa; Giordani, Hervé; Voldoire, Aurore

2013-03-01

This study investigates the mechanisms by which the ocean diurnal cycle can affect the ocean mean state in the North Atlantic region. We perform two ocean-atmosphere regionally coupled simulations (20°N-80°N, 80°W-40°E) using the CNRMOM1D ocean model coupled to the ARPEGE4 atmospheric model: one with a 1 h coupling frequency (C1h) and another with a 24 h coupling frequency (C24h). The comparison between both experiments shows that accounting for the ocean diurnal cycle tends to warm up the surface ocean at high latitudes and cool it down in the subtropics during the boreal summer season (June-August). In the subtropics, the leading cause for the formation of the negative surface temperature anomalies is the fact that the nocturnal entrainment heat flux overcompensates the diurnal absorption of solar heat flux. Both in the subtropics and in the high latitudes, the surface temperature anomalies are involved in a positive feedback loop: the cold (warm) surface anomalies favour a decrease (increase) in evaporation, a decrease (increase) in tropospheric humidity, a decrease (increase) in downwelling longwave radiative flux which in turn favours the surface cooling (warming). Furthermore, the decrease in meridional sea surface temperature gradient affects the large-scale atmospheric circulation by a decrease in the zonal mean flow.

The Ocean Carbon States Database: a proof-of-concept application of cluster analysis in the ocean carbon cycle

NASA Astrophysics Data System (ADS)

Latto, Rebecca; Romanou, Anastasia

2018-03-01

In this paper, we present a database of the basic regimes of the carbon cycle in the ocean, the ocean carbon states, as obtained using a data mining/pattern recognition technique in observation-based as well as model data. The goal of this study is to establish a new data analysis methodology, test it and assess its utility in providing more insights into the regional and temporal variability of the marine carbon cycle. This is important as advanced data mining techniques are becoming widely used in climate and Earth sciences and in particular in studies of the global carbon cycle, where the interaction of physical and biogeochemical drivers confounds our ability to accurately describe, understand, and predict CO2 concentrations and their changes in the major planetary carbon reservoirs. In this proof-of-concept study, we focus on using well-understood data that are based on observations, as well as model results from the NASA Goddard Institute for Space Studies (GISS) climate model. Our analysis shows that ocean carbon states are associated with the subtropical-subpolar gyre during the colder months of the year and the tropics during the warmer season in the North Atlantic basin. Conversely, in the Southern Ocean, the ocean carbon states can be associated with the subtropical and Antarctic convergence zones in the warmer season and the coastal Antarctic divergence zone in the colder season. With respect to model evaluation, we find that the GISS model reproduces the cold and warm season regimes more skillfully in the North Atlantic than in the Southern Ocean and matches the observed seasonality better than the spatial distribution of the regimes. Finally, the ocean carbon states provide useful information in the model error attribution. Model air-sea CO2 flux biases in the North Atlantic stem from wind speed and salinity biases in the subpolar region and nutrient and wind speed biases in the subtropics and tropics. Nutrient biases are shown to be most important in the Southern Ocean flux bias. All data and analysis scripts are available at https://data.giss.nasa.gov/oceans/carbonstates/ (DOI: https://doi.org/10.5281/zenodo.996891).

The Ocean Carbon States Database: A Proof-of-Concept Application of Cluster Analysis in the Ocean Carbon Cycle

NASA Technical Reports Server (NTRS)

Latto, Rebecca; Romanou, Anastasia

2018-01-01

In this paper, we present a database of the basic regimes of the carbon cycle in the ocean, the 'ocean carbon states', as obtained using a data mining/pattern recognition technique in observation-based as well as model data. The goal of this study is to establish a new data analysis methodology, test it and assess its utility in providing more insights into the regional and temporal variability of the marine carbon cycle. This is important as advanced data mining techniques are becoming widely used in climate and Earth sciences and in particular in studies of the global carbon cycle, where the interaction of physical and biogeochemical drivers confounds our ability to accurately describe, understand, and predict CO2 concentrations and their changes in the major planetary carbon reservoirs. In this proof-of-concept study, we focus on using well-understood data that are based on observations, as well as model results from the NASA Goddard Institute for Space Studies (GISS) climate model. Our analysis shows that ocean carbon states are associated with the subtropical-subpolar gyre during the colder months of the year and the tropics during the warmer season in the North Atlantic basin. Conversely, in the Southern Ocean, the ocean carbon states can be associated with the subtropical and Antarctic convergence zones in the warmer season and the coastal Antarctic divergence zone in the colder season. With respect to model evaluation, we find that the GISS model reproduces the cold and warm season regimes more skillfully in the North Atlantic than in the Southern Ocean and matches the observed seasonality better than the spatial distribution of the regimes. Finally, the ocean carbon states provide useful information in the model error attribution. Model air-sea CO2 flux biases in the North Atlantic stem from wind speed and salinity biases in the subpolar region and nutrient and wind speed biases in the subtropics and tropics. Nutrient biases are shown to be most important in the Southern Ocean flux bias.

Assessment of disk MHD generators for a base load powerplant

NASA Technical Reports Server (NTRS)

Chubb, D. L.; Retallick, F. D.; Lu, C. L.; Stella, M.; Teare, J. D.; Loubsky, W. J.; Louis, J. F.; Misra, B.

1981-01-01

Results from a study of the disk MHD generator are presented. Both open and closed cycle disk systems were investigated. Costing of the open cycle disk components (nozzle, channel, diffuser, radiant boiler, magnet and power management) was done. However, no detailed costing was done for the closed cycle systems. Preliminary plant design for the open cycle systems was also completed. Based on the system study results, an economic assessment of the open cycle systems is presented. Costs of the open cycle disk conponents are less than comparable linear generator components. Also, costs of electricity for the open cycle disk systems are competitive with comparable linear systems. Advantages of the disk design simplicity are considered. Improvements in the channel availability or a reduction in the channel lifetime requirement are possible as a result of the disk design.

76 FR 65183 - National Oceanic and Atmospheric Administration

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-20

... DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Climate Assessment... Oceanic and Atmospheric Administration (NOAA), Department of Commerce (DOC). ACTION: Notice of open..., National Oceanic and Atmospheric Administration. [FR Doc. 2011-27113 Filed 10-19-11; 8:45 am] BILLING CODE...

Ocean N2O Emissions : Recent Global Estimates and Anthropogenically Influenced Changes

NASA Astrophysics Data System (ADS)

Suntharalingam, P.; Buithenuis, E.; Andrews, O.; Le Quere, C.

2016-12-01

Oceanic N2O is produced by microbial activity during organic matter cycling in the subsurface ocean; its production mechanisms display sensitivity to ambient oxygen level. In the oxic ocean, N2O is produced as a byproduct during the oxidation of ammonia to nitrate, mediated by ammonia oxidizing bacteria and archea. N2O is also produced and consumed in sub-oxic and anoxic waters through the action of marine denitrifiers during the multi-step reduction of nitrate to gaseous nitrogen. The oceanic N2O distribution therefore displays significant heterogeneity with background levels of 10-20 nmol/l in the well-oxygenated ocean basins, high concentrations (> 40 nmol/l) in hypoxic waters, and N2O depletion in the core of ocean oxygen minimum zones (OMZs). Oceanic N2O emissions are estimated to account for up to a third of the pre-industrial N2O fluxes to the atmosphere, however the natural cycle of ocean N2O has been perturbed in recent decades by inputs of anthropogenically derived nutrient, and by the impacts of climate change. Anthropogenic nitrogen inputs (e.g., NOx and NHy from fossil fuel combustion and agricultural fertilizer) enter the ocean via atmospheric deposition and riverine fluxes, influencing oceanic N2O production via their impact on the marine organic matter cycle. In addition, climate variations associated with surface ocean warming affect oceanic circulation and nutrient transport pathways, influencing marine productivity and the ventilation of oxygen minimum zones. Recent studies have suggested that possible expansion of oceanic OMZs in a warming climate could lead to significant changes in N2O production and fluxes from these regions. We will summarise the current state of knowledge on the ocean N2O budget and net flux to the atmosphere. Recently reported estimates have been based on (i) empirical relationships derived from ocean tracer data (e.g., involving excess N2O and Apparent Oxygen Utilization (AOU) correlations), (ii) ocean biogeochemical models, and (iii) air-sea flux calculations which combine surface ocean N2O measurements with gas-exchange relationships. We will also present results from ongoing ocean biogeochemistry model analyses evaluating the separate influences of climate variation and anthropogenic nutrient inputs on ocean N2O emissions for recent decades.

An examination of the role of particles in oceanic mercury cycling

NASA Astrophysics Data System (ADS)

Lamborg, Carl H.; Hammerschmidt, Chad R.; Bowman, Katlin L.

2016-11-01

Recent models of global mercury (Hg) cycling have identified the downward flux of sinking particles in the ocean as a prominent Hg removal process from the ocean. At least one of these models estimates the amount of anthropogenic Hg in the ocean to be about 400 Mmol, with deep water formation and sinking fluxes representing the largest vectors by which pollutant Hg is able to penetrate the ocean interior. Using data from recent cruises to the Atlantic, we examined the dissolved and particulate partitioning of Hg in the oceanic water column as a cross-check on the hypothesis that sinking particle fluxes are important. Interestingly, these new data suggest particle-dissolved partitioning (Kd) that is approximately 20× greater than previous estimates, which thereby challenges certain assumptions about the scavenging and active partitioning of Hg in the ocean used in earlier models. For example, the new particle data suggest that regenerative scavenging is the most likely mechanism by which the association of Hg and particles occurs. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Southern Ocean biological iron cycling in the pre-whaling and present ecosystems

NASA Astrophysics Data System (ADS)

Maldonado, Maria T.; Surma, Szymon; Pakhomov, Evgeny A.

2016-11-01

This study aimed to create the first model of biological iron (Fe) cycling in the Southern Ocean food web. Two biomass mass-balanced Ecopath models were built to represent pre- and post-whaling ecosystem states (1900 and 2008). Functional group biomasses (tonnes wet weight km-2) were converted to biogenic Fe pools (kg Fe km-2) using published Fe content ranges. In both models, biogenic Fe pools and consumption in the pelagic Southern Ocean were highest for plankton and small nektonic groups. The production of plankton biomass, particularly unicellular groups, accounted for the highest annual Fe demand. Microzooplankton contributed most to biological Fe recycling, followed by carnivorous zooplankton and krill. Biological Fe recycling matched previous estimates, and, under most conditions, could entirely meet the Fe demand of bacterioplankton and phytoplankton. Iron recycling by large baleen whales was reduced 10-fold by whaling between 1900 and 2008. However, even under the 1900 scenario, the contribution of whales to biological Fe recycling was negligible compared with that of planktonic consumers. These models are a first step in examining oceanic-scale biological Fe cycling, highlighting gaps in our present knowledge and key questions for future research on the role of marine food webs in the cycling of trace elements in the sea. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Southern Ocean biological iron cycling in the pre-whaling and present ecosystems.

PubMed

Maldonado, Maria T; Surma, Szymon; Pakhomov, Evgeny A

2016-11-28

This study aimed to create the first model of biological iron (Fe) cycling in the Southern Ocean food web. Two biomass mass-balanced Ecopath models were built to represent pre- and post-whaling ecosystem states (1900 and 2008). Functional group biomasses (tonnes wet weight km -2 ) were converted to biogenic Fe pools (kg Fe km -2 ) using published Fe content ranges. In both models, biogenic Fe pools and consumption in the pelagic Southern Ocean were highest for plankton and small nektonic groups. The production of plankton biomass, particularly unicellular groups, accounted for the highest annual Fe demand. Microzooplankton contributed most to biological Fe recycling, followed by carnivorous zooplankton and krill. Biological Fe recycling matched previous estimates, and, under most conditions, could entirely meet the Fe demand of bacterioplankton and phytoplankton. Iron recycling by large baleen whales was reduced 10-fold by whaling between 1900 and 2008. However, even under the 1900 scenario, the contribution of whales to biological Fe recycling was negligible compared with that of planktonic consumers. These models are a first step in examining oceanic-scale biological Fe cycling, highlighting gaps in our present knowledge and key questions for future research on the role of marine food webs in the cycling of trace elements in the sea.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

Mantle temperature under drifting deformable continents during the supercontinent cycle

NASA Astrophysics Data System (ADS)

Yoshida, Masaki

2013-04-01

The thermal heterogeneity of the Earth's mantle under the drifting continents during a supercontinent cycle is a controversial issue in earth science. Here, a series of numerical simulations of mantle convection are performed in 3D spherical-shell geometry, incorporating drifting deformable continents and self-consistent plate tectonics, to evaluate the subcontinental mantle temperature during a supercontinent cycle. Results show that the laterally averaged temperature anomaly of the subcontinental mantle remains within several tens of degrees (±50 °C) throughout the simulation time. Even after the formation of the supercontinent and the development of subcontinental plumes due to the subduction of the oceanic plates, the laterally averaged temperature anomaly of the deep mantle under the continent is within +10 °C. This implies that there is no substantial temperature difference between the subcontinental and suboceanic mantles during a supercontinent cycle. The temperature anomaly immediately beneath the supercontinent is generally positive owing to the thermal insulation effect and the active upwelling plumes from the core-mantle boundary. In the present simulation, the formation of a supercontinent causes the laterally averaged subcontinental temperature to increase by a maximum of 50 °C, which would produce sufficient tensional force to break up the supercontinent. The periodic assembly and dispersal of continental fragments, referred to as the supercontinent cycle, bear close relation to the evolution of mantle convection and plate tectonics. Supercontinent formation involves complex processes of introversion, extroversion or a combination of these in uniting dispersed continental fragments, as against the simple opening and closing of individual oceans envisaged in Wilson cycle. In the present study, I evaluate supercontinent processes in a realistic mantle convection regime. Results show that the assembly of supercontinents is accompanied by a combination of introversion and extroversion processes. The regular periodicity of the supercontinent cycles observed in previous 2D and 3D simulation models with rigid nondeformable continents is not confirmed. The small-scale thermal heterogeneity is dominated in deep mantle convection during the supercontinent cycle, although the large-scale, active upwelling plumes intermittently originate under drifting continents and/or the supercontinent. Results suggest that active subducting cold plates along continental margins generate thermal heterogeneity with short-wavelength structures, which is consistent with the thermal heterogeneity in the present-day mantle convection inferred from seismic tomography models. References: [1] Yoshida, M. Mantle temperature under drifting deformable continents during the supercontinent cycle, Geophys. Res. Lett., 2013, in press. [2] Yoshida, M. and M. Santosh, Mantle convection modeling of supercontinent cycle: Introversion, extroversion, or combination?, 2013, submitted.

MiniFluo fluorescence sensor, advances in FDOM Ocean Measurements

NASA Astrophysics Data System (ADS)

Cyr, Frédéric; Tedetti, Marc; Goutx, Madeleine

2017-04-01

As part of the European project "Next generation Low-Cost Multifunctional Web Enabled Ocean Sensor Systems Empowering Marine, Maritime and Fisheries Management (NeXOS)", we developed the MiniFluo, a glider-compatible optical sensor for measurements of fluorescent dissolved organic matter (FDOM). In situ applications of the MiniFluo are presented here. The configuration used targets both natural (Tryptophan) and an anthropogenic (Phenanthrene) DOM fluorophores. Observations from three glider campaigns in the NW Mediterranean (Fall 2015 and Spring and Summer 2016) are presented. It is shown that the use of the Minifluo highlights new features of DOM dynamics in the region. For example, the Tryptophan (an amino-acid traditionally used as a tracer for waste waters) is found here closely related to open sea Chl-a fluorescence. Differences between Chl-a and Tryptophan fluorescence also give subtle information on seasonal changes in ecosystem structure and DOM release that could not be observed with traditional glider measurements. The study also highlights the presence of phenanthrene (an anthropogenic polycyclic aromatic hydrocarbon (PAH) in the surface and sub-surface waters of the Mediterranean. Implications of these finding will be put in the context of both the Mediterranean Sea DOM dynamics and also the ocean carbon cycle, from which the Dissolved Organic Carbon pool remains qualitatively unknown.

Bacterial Degradation of Phosphonates Bound to High-Molecular-Weight Dissolved Organic Matter Produces Methane and Other Hydrocarbons

NASA Astrophysics Data System (ADS)

Sosa, O.; Ferron Smith, S.; Karl, D. M.; DeLong, E.; Repeta, D.

2016-02-01

The biological degradation of dissolved organic matter (DOM) plays important roles in the carbon cycle and energy balance of the ocean. Yet, the biochemical pathways that drive DOM turnover remain to be fully characterized. In this study, we tested the ability of two open ocean bacterial isolates (a Pseudomonas stutzeri strain (Gammaproteobacteria) and a Sulfitobacter isolate (Alphaproteobacteria)) to degrade DOM phosphonates. Each isolate encoded a complete phosphonate degradation pathway in its genome, and each was able to degrade simple alkyl-phosphonates like methyl phosphonate, releasing methane (or other short chain hydrocarbon gases) as a result. We found that cultures incubated in the presence of HMW DOM polysaccharides also produced methane and other trace gases under aerobic conditions. To demonstrate that phosphonates were the source of these gases, we constructed a P. stutzeri mutant disabled in the phosphonate degradation pathway. Unlike the wild type, the mutant strain was deficient in the production of methane and other gases from HMW DOM-associated phosphonates. These observations support the hypothesis that DOM-bound methyl phosphonates may be a significant source of methane in the water column, and that bacterial degradation of these compounds likely contribute to the subsurface methane maxima observed throughout the world's oceans.

Antarctic Ocean Nutrient Conditions During the Last Two Glacial Cycles

NASA Astrophysics Data System (ADS)

Studer, A.; Sigman, D. M.; Martinez-Garcia, A.; Benz, V.; Winckler, G.; Kuhn, G.; Esper, O.; Lamy, F.; Jaccard, S.; Wacker, L.; Oleynik, S.; Gersonde, R.; Haug, G. H.

2014-12-01

The high concentration of the major nutrients nitrate and phosphate in the Antarctic Zone of the Southern Ocean dictates the nature of Southern Ocean ecosystems and permits these nutrients to be carried from the deep ocean into the nutrient-limited low latitudes. Incomplete nutrient consumption in the Antarctic also allows the leakage of deeply sequestered carbon dioxide (CO2) back to the atmosphere, and changes in this leakage may have driven glacial/interglacial cycles in atmospheric CO2. In a sediment core from the Pacific sector of the Antarctic Ocean, we report diatom-bound N isotope (δ15Ndb) records for total recoverable diatoms and two assemblages of diatom species. These data indicate tight coupling between the degree of nitrate consumption and Antarctic climate across the last two glacial cycles, with δ15Ndb (and thus the degree of nitrate consumption) increasing at each major Antarctic cooling event. Measurements in the same sediment core indicate that export production was reduced during ice ages, pointing to an ice age reduction in the supply of deep ocean-sourced nitrate to the Antarctic Ocean surface. The reduced export production of peak ice ages also implies a weaker winter-to-summer decline (i.e. reduced seasonality) in mixed layer nitrate concentration, providing a plausible explanation for an observed reduction in the inter-assemblage δ15Ndb difference during these coldest times. Despite the weak summertime productivity, the reduction in wintertime nitrate supply from deep waters left the Antarctic mixed layer with a low nitrate concentration, and this wintertime change also would have reduced the outgassing of CO2. Relief of light limitation fails to explain the intermediate degree of nitrate consumption that characterizes early glacial conditions, as improved light limitation coincident with reduced nitrate supply would drive nitrate consumption to completion. Thus, the data favor iron availability as the dominant control on annual Antarctic Ocean export production over glacial cycles.

Meridional contrasts in productivity changes driven by the Cenozoic opening of Drake Passage

NASA Astrophysics Data System (ADS)

Donnadieu, Y.; Ladant, J. B.; Bopp, L.; Wilson, P. A.; Lear, C. H.

2017-12-01

The progressive opening of Drake Passage across the Eocene and the Oligocene occurs contemporaneously to the long-term global cooling of the late Eocene, which culminated with the Eocene-Oligocene glaciation of Antarctica. Atmospheric pCO2 decline during the late Eocene is thought to have played a major role in the climatic shifts of the Eocene-Oligocene boundary, yet reasons behind CO2 variations remain obscure. Changes in marine productivity affecting the biological oceanic carbon pump represent a possible cause. Here, we explore whether and how the opening of Drake Passage may have affected the marine biogeochemistry, and in particular paleoproductivity changes, with the use of a fully coupled atmosphere-ocean-biogeochemical model (IPSL-CM5A). We find that the simulated changes to Drake Passage opening exhibit a uniform decrease in the low latitudes while the high latitude response is more spatially heterogeneous. Mechanistically, the low latitude productivity decrease is a consequence of the dramatic reorganization of the ocean circulation when Drake Passage opens, as the shift from a well ventilated to a swampier ocean drives nutrient depletion in the low latitudes. In the high latitudes, the onset of the Antarctic Circumpolar Current in the model exerts a strong control both on nutrient availability but also on regions of deep water formation, which results in non-uniform patterns of productivity change in the Southern Ocean. The qualitative agreement between geographically diverse long-term paleoproductivity records and the simulated variations suggests that the opening of Drake Passage may contribute to part of the long-term paleoproductivity signal recorded in the data.

The inverse problem: Ocean tides derived from earth tide observations

NASA Technical Reports Server (NTRS)

Kuo, J. T.

1978-01-01

Indirect mapping ocean tides by means of land and island-based tidal gravity measurements is presented. The inverse scheme of linear programming is used for indirect mapping of ocean tides. Open ocean tides were measured by the numerical integration of Laplace's tidal equations.

Major role of nitrite-oxidizing bacteria in dark ocean carbon fixation.

PubMed

Pachiadaki, Maria G; Sintes, Eva; Bergauer, Kristin; Brown, Julia M; Record, Nicholas R; Swan, Brandon K; Mathyer, Mary Elizabeth; Hallam, Steven J; Lopez-Garcia, Purificacion; Takaki, Yoshihiro; Nunoura, Takuro; Woyke, Tanja; Herndl, Gerhard J; Stepanauskas, Ramunas

2017-11-24

Carbon fixation by chemoautotrophic microorganisms in the dark ocean has a major impact on global carbon cycling and ecological relationships in the ocean's interior, but the relevant taxa and energy sources remain enigmatic. We show evidence that nitrite-oxidizing bacteria affiliated with the Nitrospinae phylum are important in dark ocean chemoautotrophy. Single-cell genomics and community metagenomics revealed that Nitrospinae are the most abundant and globally distributed nitrite-oxidizing bacteria in the ocean. Metaproteomics and metatranscriptomics analyses suggest that nitrite oxidation is the main pathway of energy production in Nitrospinae. Microautoradiography, linked with catalyzed reporter deposition fluorescence in situ hybridization, indicated that Nitrospinae fix 15 to 45% of inorganic carbon in the mesopelagic western North Atlantic. Nitrite oxidation may have a greater impact on the carbon cycle than previously assumed. Copyright © 2017, American Association for the Advancement of Science.

Deciphering ocean carbon in a changing world

PubMed Central

Moran, Mary Ann; Stubbins, Aron; Fatland, Rob; Aluwihare, Lihini I.; Buchan, Alison; Crump, Byron C.; Dorrestein, Pieter C.; Dyhrman, Sonya T.; Hess, Nancy J.; Howe, Bill; Longnecker, Krista; Medeiros, Patricia M.; Obernosterer, Ingrid; Repeta, Daniel J.; Waldbauer, Jacob R.

2016-01-01

Dissolved organic matter (DOM) in the oceans is one of the largest pools of reduced carbon on Earth, comparable in size to the atmospheric CO2 reservoir. A vast number of compounds are present in DOM, and they play important roles in all major element cycles, contribute to the storage of atmospheric CO2 in the ocean, support marine ecosystems, and facilitate interactions between organisms. At the heart of the DOM cycle lie molecular-level relationships between the individual compounds in DOM and the members of the ocean microbiome that produce and consume them. In the past, these connections have eluded clear definition because of the sheer numerical complexity of both DOM molecules and microorganisms. Emerging tools in analytical chemistry, microbiology, and informatics are breaking down the barriers to a fuller appreciation of these connections. Here we highlight questions being addressed using recent methodological and technological developments in those fields and consider how these advances are transforming our understanding of some of the most important reactions of the marine carbon cycle. PMID:26951682

Deciphering ocean carbon in a changing world.

PubMed

Moran, Mary Ann; Kujawinski, Elizabeth B; Stubbins, Aron; Fatland, Rob; Aluwihare, Lihini I; Buchan, Alison; Crump, Byron C; Dorrestein, Pieter C; Dyhrman, Sonya T; Hess, Nancy J; Howe, Bill; Longnecker, Krista; Medeiros, Patricia M; Niggemann, Jutta; Obernosterer, Ingrid; Repeta, Daniel J; Waldbauer, Jacob R

2016-03-22

Dissolved organic matter (DOM) in the oceans is one of the largest pools of reduced carbon on Earth, comparable in size to the atmospheric CO2 reservoir. A vast number of compounds are present in DOM, and they play important roles in all major element cycles, contribute to the storage of atmospheric CO2 in the ocean, support marine ecosystems, and facilitate interactions between organisms. At the heart of the DOM cycle lie molecular-level relationships between the individual compounds in DOM and the members of the ocean microbiome that produce and consume them. In the past, these connections have eluded clear definition because of the sheer numerical complexity of both DOM molecules and microorganisms. Emerging tools in analytical chemistry, microbiology, and informatics are breaking down the barriers to a fuller appreciation of these connections. Here we highlight questions being addressed using recent methodological and technological developments in those fields and consider how these advances are transforming our understanding of some of the most important reactions of the marine carbon cycle.

Geoengineering impact of open ocean dissolution of olivine on atmospheric CO2, surface ocean pH and marine biology

NASA Astrophysics Data System (ADS)

Köhler, Peter; Abrams, Jesse F.; Völker, Christoph; Hauck, Judith; Wolf-Gladrow, Dieter A.

2013-03-01

Ongoing global warming induced by anthropogenic emissions has opened the debate as to whether geoengineering is a ‘quick fix’ option. Here we analyse the intended and unintended effects of one specific geoengineering approach, which is enhanced weathering via the open ocean dissolution of the silicate-containing mineral olivine. This approach would not only reduce atmospheric CO2 and oppose surface ocean acidification, but would also impact on marine biology. If dissolved in the surface ocean, olivine sequesters 0.28 g carbon per g of olivine dissolved, similar to land-based enhanced weathering. Silicic acid input, a byproduct of the olivine dissolution, alters marine biology because silicate is in certain areas the limiting nutrient for diatoms. As a consequence, our model predicts a shift in phytoplankton species composition towards diatoms, altering the biological carbon pumps. Enhanced olivine dissolution, both on land and in the ocean, therefore needs to be considered as ocean fertilization. From dissolution kinetics we calculate that only olivine particles with a grain size of the order of 1 μm sink slowly enough to enable a nearly complete dissolution. The energy consumption for grinding to this small size might reduce the carbon sequestration efficiency by ˜30%.

Major role of planktonic phosphate reduction in the marine phosphorus redox cycle

NASA Astrophysics Data System (ADS)

Van Mooy, B. A. S.; Krupke, A.; Dyhrman, S. T.; Fredricks, H. F.; Frischkorn, K. R.; Ossolinski, J. E.; Repeta, D. J.; Rouco, M.; Seewald, J. D.; Sylva, S. P.

2015-05-01

Phosphorus in the +5 oxidation state (i.e., phosphate) is the most abundant form of phosphorus in the global ocean. An enigmatic pool of dissolved phosphonate molecules, with phosphorus in the +3 oxidation state, is also ubiquitous; however, cycling of phosphorus between oxidation states has remained poorly constrained. Using simple incubation and chromatography approaches, we measured the rate of the chemical reduction of phosphate to P(III) compounds in the western tropical North Atlantic Ocean. Colonial nitrogen-fixing cyanobacteria in surface waters played a critical role in phosphate reduction, but other classes of plankton, including potentially deep-water archaea, were also involved. These data are consistent with marine geochemical evidence and microbial genomic information, which together suggest the existence of a vast oceanic phosphorus redox cycle.

Identifying Meteorological Controls on Open and Closed Mesoscale Cellular Convection Associated with Marine Cold Air Outbreaks

NASA Astrophysics Data System (ADS)

McCoy, Isabel L.; Wood, Robert; Fletcher, Jennifer K.

2017-11-01

Mesoscale cellular convective (MCC) clouds occur in large-scale patterns over the ocean and have important radiative effects on the climate system. An examination of time-varying meteorological conditions associated with satellite-observed open and closed MCC clouds is conducted to illustrate the influence of large-scale meteorological conditions. Marine cold air outbreaks (MCAO) influence the development of open MCC clouds and the transition from closed to open MCC clouds. MCC neural network classifications on Moderate Resolution Imaging Spectroradiometer (MODIS) data for 2008 are collocated with Clouds and the Earth's Radiant Energy System (CERES) data and ERA-Interim reanalysis to determine the radiative effects of MCC clouds and their thermodynamic environments. Closed MCC clouds are found to have much higher albedo on average than open MCC clouds for the same cloud fraction. Three meteorological control metrics are tested: sea-air temperature difference (ΔT), estimated inversion strength (EIS), and a MCAO index (M). These predictive metrics illustrate the importance of atmospheric surface forcing and static stability for open and closed MCC cloud formation. Predictive sigmoidal relations are found between M and MCC cloud frequency globally and regionally: negative for closed MCC cloud and positive for open MCC cloud. The open MCC cloud seasonal cycle is well correlated with M, while the seasonality of closed MCC clouds is well correlated with M in the midlatitudes and EIS in the tropics and subtropics. M is found to best distinguish open and closed MCC clouds on average over shorter time scales. The possibility of a MCC cloud feedback is discussed.

Cycles in oceanic teleconnections and global temperature change

NASA Astrophysics Data System (ADS)

Seip, Knut L.; Grøn, Øyvind

2018-06-01

Three large ocean currents are represented by proxy time series: the North Atlantic Oscillation (NAO), the Southern Oscillation Index (SOI), and the Pacific Decadal Oscillation (PDO). We here show how proxies for the currents interact with each other and with the global temperature anomaly (GTA). Our results are obtained by a novel method, which identifies running average leading-lagging (LL) relations, between paired series. We find common cycle times for a paired series of 6-7 and 25-28 years and identify years when the LL relations switch. Switching occurs with 18.4 ± 14.3-year intervals for the short 6-7-year cycles and with 27 ± 15-year intervals for the 25-28-year cycles. During the period 1940-1950, the LL relations for the long cycles were circular (nomenclature x leads y: x → y): GTA → NAO → SOI → PDO → GTA. However, after 1960, the LL relations become more complex and there are indications that GTA leads to both NAO and PDO. The switching years are related to ocean current tie points and reversals reported in the literature.

Gases in Seawater

NASA Astrophysics Data System (ADS)

Nightingale, P. D.; Liss, P. S.

2003-12-01

The annual gross and net primary productivity of the surface oceans is similar in size to that on land (IPCC, 2001). Marine productivity drives the cycling of gases such as oxygen (O2), dimethyl sulfide (DMS), carbon monoxide (CO), carbon dioxide (CO2), and methyl iodide (CH3I) which are of fundamental importance in studies of marine productivity, biogeochemical cycles, atmospheric chemistry, climate, and human health, respectively. For example, ˜30% of the world's population (1,570 million) is thought to be at risk of iodine-deficiency disorders that impair mental development (WHO, 1996). The main source of iodine to land is the supply of volatile iodine compounds produced in the ocean and then transferred to the atmosphere via the air-surface interface. The flux of these marine iodine species to the atmosphere is also thought to be important in the oxidation capacity of the troposphere by the production of the iodine oxide radical ( Alicke et al., 1999). A further example is that the net flux of CO2 from the atmosphere to the ocean, ˜1.7±0.5 Gt C yr-1, represents ˜30% of the annual release of anthropogenic CO2 to the atmosphere (IPCC, 2001). This net flux is superimposed on a huge annual flux (90 Gt C yr-1) of CO2 that is cycled "naturally" between the ocean and the atmosphere. The long-term sink for anthropogenic CO2 is recognized as transfer to the ocean from the atmosphere. A final example is the emission of volatile sulfur, in the form of DMS, from the oceans. Not only is an oceanic flux from the oceans needed to balance the loss of sulfur (a bioessential element) from the land via weathering, it has also been proposed as having a major control on climate due to the formation of cloud condensation nuclei (Charlson et al., 1987). Indeed, the existence of DMS and CH3I has been used as evidence in support of the Gaia hypothesis (Lovelock, 1979).There are at least four main processes that affect the concentration of gases in the water column: biological production and consumption, photochemistry, air-sea exchange, and vertical mixing. We will not discuss the effect of vertical mixing on gases in seawater and instead refer the reader to Chapter 6.08. Nor will we consider the deeper oceans as this region is discussed in chapters on benthic fluxes and early diagenesis (Chapter 6.11), the biological pump (Chapter 6.04), and the oceanic calcium carbonate cycle (Chapter 6.19) all in this volume. We will discuss the cycling of gases in surface oceans, including the thermocline, and in particular concentrate on the exchange of various volatile compounds across the air-sea interface.As we will show, while much is known about the cycling of gases such as CO2 and DMS in the water column, frustratingly little is known about many of the chemical species for which the ocean is believed to be a significant source to the atmosphere. We suspect the passage of time will reveal that the cycling of volatile compounds containing selenium and iodine may well prove as complex as that of DMS. Early studies of DMS assumed that it was produced from a precursor compound, dimethylsulfoniopropionate (DMSP), known to be present in some species of phytoplankton, and that the main sink in the water column was exchange across the air-sea interface. We now know that DMSP and DMS are both rapidly cycled in water column by a complex interaction between phytoplankton, microzooplankton, bacteria, and viruses (see Figure 1). Some detailed process experiments have revealed that only ˜10% of the total DMS produced (and less than 1.3% of the DMSP produced) is transferred to the atmosphere, with the bulk of the DMS and DMSP, either being recycled in the water column or photo-oxidized (Archer et al., 2002b).

Global Links to Local Carbon Cycling Perturbation

NASA Astrophysics Data System (ADS)

Chen, J.; Montanez, I. P.; Wang, X.; Qi, Y.

2016-12-01

Carbon cycle perturbations recorded by stable carbon isotope excursions (CIEs) play an important role in understanding climate, oceanography, and the biosphere through time. Recent studies, however, reveal the influence of regional processes on apparent global CIEs. Deconvolving local/regional from global processes imprinted in the carbon isotopic records of sedimentary successions requires integrated sedimentologic, stratigraphic, and geochemical study. Here we present coupled C and Sr isotopic records of diagenetically screened micrite and brachiopods from late Mississippian shallow-marine, carbonate platform and contemporaneous carbonate slope successions from the east Paleotethys Ocean region (South China). These records reveal distinctly different signatures of the depositional response to the onset of Carboniferous glaciation. C and Sr isotopic compositions of the platform carbonates exhibit systematic fluctuations in step with inferred sea-level changes captured by depositional cycles. CIEs in the platform succession can be correlated to the contemporaneous C isotope record from the Antler carbonate ramp (Idaho, USA). In contrast, slope carbonate and conodont isotopic records exhibit minimal variability interpreted to record the open-ocean seawater composition. The isotopic disparity between successions is interpreted to record the influence of local depositional, but not diagenetic, processes operating on the carbonate platform in response to glacioeustasy. Variability in the nature of coupled isotopic and inferred sea level fluctuations is interpreted to record stepwise onset of the late Paleozoic ice age in the late Mississippian. Initial large magnitude shifts in C and Sr isotopic compositions of late Visean to early Serpukhovian carbonates correspond to 1 to 2 myr-scale cycles driven by the buildup of continental glaciers. Subsequent decreased magnitude of isotopic shifts coincident with a shift to shorter duration and smaller magnitude sea-level fluctuations in the middle to late Serpukhovian interval is interpreted to record temporary retraction of the ice sheets in response to late Serpukhovian warming. Overall, the coupled stratigraphic and isotopic records indicate stepwise ice buildup prior to widespread glaciation across the mid-Carboniferous boundary.

Pelagic Biocarbonates: Assessing the "Forgotten" Fine Fraction

NASA Astrophysics Data System (ADS)

Brummer, G. J. A.

2016-02-01

Biocarbonates play an important role in the global carbon cycle and cover over half of the ocean floor. Biocarbonates in the open ocean are best known from planktonic foraminifera, which are relatively large (>150µm), heavy and few and coccoliths, which are very small (<32µm), light and abundant. Both of these components are relatively well studied. The size fraction in between adult foraminifera and coccoliths (32-150µm: the so-called fine fraction) consists of a large but poorly known mixture of particles, which is genarlly assumed to consist primarily of "juvenile" planktonic foraminifera, with minor amounts of calcareous dinoflagellates and various others less well-known microfossils. Abundance, diversity, mass and composition within the fine fraction are poorly constrained, as is the response to acidification/dissolution. This lack of knowledge primarily reflects the gap in size fraction studied by the different disciplinary approaches and techniques, which are not suited for identifying and quantifying these intermediate groups. Comparative ontogeny of planktonic foraminifera now shows that this fine fraction in sediments does not consist of "juveniles" as in the living plankton, but is dominated by mature specimens of small-sized species. First estimates indicate that these small species not only account for about one third of the number of species of planktonic foraminifera but also form about one third of their shell flux and global carbonate production in weight. Still, we hardly know anything on seasonality, depth habitat, shell composition (isotopes, trace metal incorporation), potential autotrophic symbionts, molecular genetics and geological range of these clearly very important species. Estimates from well-preserved sediments, show that the important role of these minute foraminiferal planktonic species may hold for much of the 180Ma long fossil record, opening a new research field pertaining to both modern and past pelagic ecosystems and the role of these species in global carbon cycles.

A model for the oceanic mass balance of rhenium and implications for the extent of Proterozoic ocean anoxia

NASA Astrophysics Data System (ADS)

Sheen, Alex I.; Kendall, Brian; Reinhard, Christopher T.; Creaser, Robert A.; Lyons, Timothy W.; Bekker, Andrey; Poulton, Simon W.; Anbar, Ariel D.

2018-04-01

Emerging geochemical evidence suggests that the atmosphere-ocean system underwent a significant decrease in O2 content following the Great Oxidation Event (GOE), leading to a mid-Proterozoic ocean (ca. 2.0-0.8 Ga) with oxygenated surface waters and predominantly anoxic deep waters. The extent of mid-Proterozoic seafloor anoxia has been recently estimated using mass-balance models based on molybdenum (Mo), uranium (U), and chromium (Cr) enrichments in organic-rich mudrocks (ORM). Here, we use a temporal compilation of concentrations for the redox-sensitive trace metal rhenium (Re) in ORM to provide an independent constraint on the global extent of mid-Proterozoic ocean anoxia and as a tool for more generally exploring how the marine geochemical cycle of Re has changed through time. The compilation reveals that mid-Proterozoic ORM are dominated by low Re concentrations that overall are only mildly higher than those of Archean ORM and significantly lower than many ORM deposited during the ca. 2.22-2.06 Ga Lomagundi Event and during the Phanerozoic Eon. These temporal trends are consistent with a decrease in the oceanic Re inventory in response to an expansion of anoxia after an interval of increased oxygenation during the Lomagundi Event. Mass-balance modeling of the marine Re geochemical cycle indicates that the mid-Proterozoic ORM with low Re enrichments are consistent with extensive seafloor anoxia. Beyond this agreement, these new data bring added value because Re, like the other metals, responds generally to low-oxygen conditions but has its own distinct sensitivity to the varying environmental controls. Thus, we can broaden our capacity to infer nuanced spatiotemporal patterns in ancient redox landscapes. For example, despite the still small number of data, some mid-Proterozoic ORM units have higher Re enrichments that may reflect a larger oceanic Re inventory during transient episodes of ocean oxygenation. An improved understanding of the modern oceanic Re cycle and a higher temporal resolution for the Re compilation will enable further tests of these hypotheses regarding changes in the surficial Re geochemical cycle in response to variations in atmosphere-ocean oxygenation. Nevertheless, the existing Re compilation and model results are in agreement with previous Cr, Mo, and U evidence for pervasively anoxic and ferruginous conditions in mid-Proterozoic oceans.

Undocumented water column sink for cadmium in open ocean oxygen-deficient zones

PubMed Central

Janssen, David J.; Conway, Tim M.; John, Seth G.; Christian, James R.; Kramer, Dennis I.; Pedersen, Tom F.; Cullen, Jay T.

2014-01-01

Cadmium (Cd) is a micronutrient and a tracer of biological productivity and circulation in the ocean. The correlation between dissolved Cd and the major algal nutrients in seawater has led to the use of Cd preserved in microfossils to constrain past ocean nutrient distributions. However, linking Cd to marine biological processes requires constraints on marine sources and sinks of Cd. Here, we show a decoupling between Cd and major nutrients within oxygen-deficient zones (ODZs) in both the Northeast Pacific and North Atlantic Oceans, which we attribute to Cd sulfide (CdS) precipitation in euxinic microenvironments around sinking biological particles. We find that dissolved Cd correlates well with dissolved phosphate in oxygenated waters, but is depleted compared with phosphate in ODZs. Additionally, suspended particles from the North Atlantic show high Cd content and light Cd stable isotope ratios within the ODZ, indicative of CdS precipitation. Globally, we calculate that CdS precipitation in ODZs is an important, and to our knowledge a previously undocumented marine sink of Cd. Our results suggest that water column oxygen depletion has a substantial impact on Cd biogeochemical cycling, impacting the global relationship between Cd and major nutrients and suggesting that Cd may be a previously unidentified tracer for water column oxygen deficiency on geological timescales. Similar depletions of copper and zinc in the Northeast Pacific indicate that sulfide precipitation in ODZs may also have an influence on the global distribution of other trace metals. PMID:24778239

Undocumented water column sink for cadmium in open ocean oxygen-deficient zones.

PubMed

Janssen, David J; Conway, Tim M; John, Seth G; Christian, James R; Kramer, Dennis I; Pedersen, Tom F; Cullen, Jay T

2014-05-13

Cadmium (Cd) is a micronutrient and a tracer of biological productivity and circulation in the ocean. The correlation between dissolved Cd and the major algal nutrients in seawater has led to the use of Cd preserved in microfossils to constrain past ocean nutrient distributions. However, linking Cd to marine biological processes requires constraints on marine sources and sinks of Cd. Here, we show a decoupling between Cd and major nutrients within oxygen-deficient zones (ODZs) in both the Northeast Pacific and North Atlantic Oceans, which we attribute to Cd sulfide (CdS) precipitation in euxinic microenvironments around sinking biological particles. We find that dissolved Cd correlates well with dissolved phosphate in oxygenated waters, but is depleted compared with phosphate in ODZs. Additionally, suspended particles from the North Atlantic show high Cd content and light Cd stable isotope ratios within the ODZ, indicative of CdS precipitation. Globally, we calculate that CdS precipitation in ODZs is an important, and to our knowledge a previously undocumented marine sink of Cd. Our results suggest that water column oxygen depletion has a substantial impact on Cd biogeochemical cycling, impacting the global relationship between Cd and major nutrients and suggesting that Cd may be a previously unidentified tracer for water column oxygen deficiency on geological timescales. Similar depletions of copper and zinc in the Northeast Pacific indicate that sulfide precipitation in ODZs may also have an influence on the global distribution of other trace metals.

Basin-scale estimates of pelagic and coral reef calcification in the Red Sea and Western Indian Ocean.

PubMed

Steiner, Zvi; Erez, Jonathan; Shemesh, Aldo; Yam, Ruth; Katz, Amitai; Lazar, Boaz

2014-11-18

Basin-scale calcification rates are highly important in assessments of the global oceanic carbon cycle. Traditionally, such estimates were based on rates of sedimentation measured with sediment traps or in deep sea cores. Here we estimated CaCO3 precipitation rates in the surface water of the Red Sea from total alkalinity depletion along their axial flow using the water flux in the straits of Bab el Mandeb. The relative contribution of coral reefs and open sea plankton were calculated by fitting a Rayleigh distillation model to the increase in the strontium to calcium ratio. We estimate the net amount of CaCO3 precipitated in the Red Sea to be 7.3 ± 0.4·10(10) kg·y(-1) of which 80 ± 5% is by pelagic calcareous plankton and 20 ± 5% is by the flourishing coastal coral reefs. This estimate for pelagic calcification rate is up to 40% higher than published sedimentary CaCO3 accumulation rates for the region. The calcification rate of the Gulf of Aden was estimated by the Rayleigh model to be ∼1/2 of the Red Sea, and in the northwestern Indian Ocean, it was smaller than our detection limit. The results of this study suggest that variations of major ions on a basin scale may potentially help in assessing long-term effects of ocean acidification on carbonate deposition by marine organisms.

Indian Ocean research: Opportunities and challenges

NASA Astrophysics Data System (ADS)

Hood, Raleigh R.; Wiggert, Jerry D.; Naqvi, S. Wajih A.

Historically, the Indian Ocean (IO) has received relatively little attention from the oceanographic community and therefore remains substantially undersampled compared to the Atlantic and Pacific oceans. This situation is compounded by the IO being a dynamically complex and highly variable system under monsoonal influence. The biogeochemical and ecological impacts of this complex physical forcing are not yet fully understood. Specific questions and hypotheses have emerged from recent studies that have yet to be tested, such as the potential role of zooplankton grazing versus iron limitation in controlling phytoplankton production in the Arabian Sea (AS). Furthermore, the IO is a globally important denitrification zone, and it also appears to be a region where N2 fixation rates are significant. However, there are still large uncertainties in the rate estimates for both. The IO is also warming rapidly, but the impacts of this warming on the biota, carbon uptake, and nitrogen cycling are unquantified. The increasing population density and rapid economic growth of the countries surrounding the Bay of Bengal and eastern AS make these regions' coastal environments particularly vulnerable to anthropogenic influences. Warming and anthropogenic effects might also impact the huge myctophid stocks in the AS and other commercially valuable species. These potential influences and their socioeconomic ramifications need to be explored. Deployment of coastal and open ocean observing systems in the IO has created new opportunities for carrying out biogeochemical and ecological research. International research efforts should be motivated to exploit these opportunities for addressing the questions identified in this chapter.

Basin-scale estimates of pelagic and coral reef calcification in the Red Sea and Western Indian Ocean

PubMed Central

Steiner, Zvi; Erez, Jonathan; Shemesh, Aldo; Yam, Ruth; Katz, Amitai; Lazar, Boaz

2014-01-01

Basin-scale calcification rates are highly important in assessments of the global oceanic carbon cycle. Traditionally, such estimates were based on rates of sedimentation measured with sediment traps or in deep sea cores. Here we estimated CaCO3 precipitation rates in the surface water of the Red Sea from total alkalinity depletion along their axial flow using the water flux in the straits of Bab el Mandeb. The relative contribution of coral reefs and open sea plankton were calculated by fitting a Rayleigh distillation model to the increase in the strontium to calcium ratio. We estimate the net amount of CaCO3 precipitated in the Red Sea to be 7.3 ± 0.4·1010 kg·y−1 of which 80 ± 5% is by pelagic calcareous plankton and 20 ± 5% is by the flourishing coastal coral reefs. This estimate for pelagic calcification rate is up to 40% higher than published sedimentary CaCO3 accumulation rates for the region. The calcification rate of the Gulf of Aden was estimated by the Rayleigh model to be ∼1/2 of the Red Sea, and in the northwestern Indian Ocean, it was smaller than our detection limit. The results of this study suggest that variations of major ions on a basin scale may potentially help in assessing long-term effects of ocean acidification on carbonate deposition by marine organisms. PMID:25368148

Satellite-based global-ocean mass balance estimates of interannual variability and emerging trends in continental freshwater discharge

PubMed Central

Syed, Tajdarul H.; Famiglietti, James S.; Chambers, Don P.; Willis, Josh K.; Hilburn, Kyle

2010-01-01

Freshwater discharge from the continents is a key component of Earth’s water cycle that sustains human life and ecosystem health. Surprisingly, owing to a number of socioeconomic and political obstacles, a comprehensive global river discharge observing system does not yet exist. Here we use 13 years (1994–2006) of satellite precipitation, evaporation, and sea level data in an ocean mass balance to estimate freshwater discharge into the global ocean. Results indicate that global freshwater discharge averaged 36,055 km3/y for the study period while exhibiting significant interannual variability driven primarily by El Niño Southern Oscillation cycles. The method described here can ultimately be used to estimate long-term global discharge trends as the records of sea level rise and ocean temperature lengthen. For the relatively short 13-year period studied here, global discharge increased by 540 km3/y2, which was largely attributed to an increase of global-ocean evaporation (768 km3/y2). Sustained growth of these flux rates into long-term trends would provide evidence for increasing intensity of the hydrologic cycle. PMID:20921364

Disentangling the record of diagenesis, local redox conditions, and global seawater chemistry during the latest Ordovician glaciation

NASA Astrophysics Data System (ADS)

Ahm, Anne-Sofie C.; Bjerrum, Christian J.; Hammarlund, Emma U.

2017-02-01

The Late Ordovician stratigraphic record integrates glacio-eustatic processes, water-column redox conditions and carbon cycle dynamics. This complex stratigraphic record, however, is dominated by deposits from epeiric seas that are susceptible to local physical and chemical processes decoupled from the open ocean. This study contributes a unique deep water basinal perspective to the Late Ordovician (Hirnantian) glacial record and the perturbations in seawater chemistry that may have contributed to the Hirnantian mass extinction event. We analyze recently drilled cores and outcrop samples from the upper Vinini Formation in central Nevada and report combined trace- and major element geochemistry, Fe speciation (FePy /FeHR and FeHR /FeT), and stable isotope chemostratigraphy (δ13COrg and δ34SPy). Measurements of paired samples from outcrop and core reveal that reactive Fe is preserved mainly as pyrite in core samples, while outcrop samples have been significantly altered as pyrite has been oxidized and remobilized by modern weathering processes. Fe speciation in the more pristine core samples indicates persistent deep water anoxia, at least locally through the Late Ordovician, in contrast to the prevailing interpretation of increased Hirnantian water column oxygenation in shallower environments. Deep water redox conditions were likely decoupled from shallower environments by a basinal shift in organic matter export driven by decreasing rates of organic matter degradation and decreasing shelf areas. The variable magnitude in the record of the Hirnantian carbon isotope excursion may be explained by this increased storage of isotopically light carbon in the deep ocean which, in combination with increased glacio-eustatic restriction, would strengthen lateral- and vertical gradients in seawater chemistry. We adopt multivariate statistical methods to deconstruct the spatial and temporal re-organization of seawater chemistry during the Hirnantian glaciation and attempt to isolate the latent magnitude and global perturbation in the carbon cycle. We speculate, using a two component mixing model and residual estimates from principal component analysis, that the secular open ocean Hirnantian C isotope excursion possibly amounts to only ∼ +1.5‰. Such an increase could be mechanistically driven by the combination of sea-level fall, persistent deep water anoxia, and cooler glacial temperatures that increased the organic carbon burial efficiency in the deeper basins.

Predicting the La Niña of 2020-21: Termination of Solar Cycles and Correlated Variance in Solar and Atmospheric Variability

NASA Astrophysics Data System (ADS)

Leamon, R. J.; McIntosh, S. W.

2017-12-01

Establishing a solid physical connection between solar and tropospheric variability has posed a considerable challenge across the spectrum of Earth-system science. Over the past few years a new picture to describe solar variability has developed, based on observing, understanding and tracing the progression, interaction and intrinsic variability of the magnetized activity bands that belong to the Sun's 22-year magnetic activity cycle. The intra- and extra-hemispheric interaction of these magnetic bands appear to explain the occurrence of decadal scale variability that primarily manifests itself in the sunspot cycle. However, on timescales of ten months or so, those bands posses their own internal variability with an amplitude of the same order of magnitude as the decadal scale. The latter have been tied to the existence of magnetized Rossby waves in the solar convection zone that result in surges of magnetic flux emergence that correspondingly modulate our star's radiative and particulate output. One of the most important events in the progression of these bands is their (apparent) termination at the solar equator that signals a global increase in magnetic flux emergence that becomes the new solar cycle. We look at the particulate and radiative implications of these termination points, their temporal recurrence and signature, from the Sun to the Earth, and show the correlated signature of solar cycle termination events and major oceanic oscillations that extend back many decades. A combined one-two punch of reduced particulate forcing and increased radiative forcing that result from the termination of one solar cycle and rapid blossoming of another correlates strongly with a shift from El Niño to La Niña conditions in the Pacific Ocean. This shift does not occur at solar minima, nor solar maxima, but at a particular, non-periodic, time in between. The failure to identify these termination points, and their relative irregularity, have inhibited a correlation to be observed and physical processes to be studied. This result potentially opens the door to a broader understanding of solar variability on our planet and its weather. Ongoing tracking of solar magnetic band migration indicates that Cycle 24 will terminate in the 2020 timeframe and thus we may expect to see an attendant shift to La Niña conditions at that time.

Seasonality of submesoscale dynamics in the Kuroshio Extension

NASA Astrophysics Data System (ADS)

Rocha, Cesar B.; Gille, Sarah T.; Chereskin, Teresa K.; Menemenlis, Dimitris

2016-11-01

Recent studies show that the vigorous seasonal cycle of the mixed layer modulates upper ocean submesoscale turbulence. Here we provide model-based evidence that the seasonally changing upper ocean stratification in the Kuroshio Extension also modulates submesoscale (here 10-100 km) inertia-gravity waves. Summertime restratification weakens submesoscale turbulence but enhances inertia-gravity waves near the surface. Thus, submesoscale turbulence and inertia-gravity waves undergo vigorous out-of-phase seasonal cycles. These results imply a strong seasonal modulation of the accuracy of geostrophic velocity diagnosed from submesoscale sea surface height delivered by the Surface Water and Ocean Topography satellite mission.

Sedimentary organic matter and carbonate variations in the Chukchi Borderland in association with ice sheet and ocean-atmosphere dynamics over the last 155 kyr

NASA Astrophysics Data System (ADS)

Rella, S. F.; Uchida, M.

2011-12-01

Knowledge on past variability of sedimentary organic carbon in the Arctic Ocean is important to assess natural carbon cycling and transport processes related to global climate changes. However, the late Pleistocene oceanographic history of the Arctic is still poorly understood. In the present study we show sedimentary records of total organic carbon (TOC), CaCO3, benthic foraminiferal δ18O and the coarse grain size fraction from a piston core recovered from the northern Northwind Ridge in the far western Arctic Ocean, a region potentially sensitively responding to past variability in surface current regimes and sedimentary processes such as coastal erosion. An age model based on oxygen stratigraphy, radiocarbon dating and lithological constraints suggests that the piston core records paleoenvironmental changes of the last 155 kyr. TOC shows orbital-scale increases and decreases that can be respectively correlated to the waxing and waning of large ice sheets dominating the Eurasian Arctic, suggesting advection of fine suspended matter derived from glacial erosion to the Northwind Ridge by eastward flowing intermediate water and/or surface water and sea ice during cold episodes of the last two glacial-interglacial cycles. At millennial scales, increases in TOC might correlate to a suite of Dansgaard-Oeschger Stadials between 120 and 45 ka before present (BP) indicating a possible response to abrupt northern hemispheric temperature changes. Between 70 and 45 ka BP, closures and openings of the Bering Strait could have additionally influenced TOC variability. CaCO3 content tends to anti-correlate with TOC on both orbital and millennial time scales, which we interpret in terms of enhanced sediment advection from the carbonate-rich Canadian Arctic via an extended Beaufort Gyre during warm periods of the last two glacial-interglacial cycles and increased organic carbon advection from the Siberian Arctic during cold periods when the Beaufort Gyre contracted. We propose that this pattern may be related to orbital- and millennial-scale variations of dominant atmospheric surface pressure systems expressed in mode shifts of the Arctic Oscillation.

Seasonal variation of the South Indian tropical gyre

NASA Astrophysics Data System (ADS)

Aguiar-González, Borja; Ponsoni, Leandro; Ridderinkhof, Herman; van Aken, Hendrik M.; de Ruijter, Will P. M.; Maas, Leo R. M.

2016-04-01

The South Indian tropical gyre receives and redistributes water masses from the Indonesian Throughflow (ITF), a source of Pacific Ocean water which represents the only low-latitude connector between the world oceans and, therefore, a key component in the global ocean circulation and climate system. We investigate the seasonal variation of the South Indian tropical gyre and its associated open-ocean upwelling system, known as the Seychelles-Chagos Thermocline Ridge (SCTR), based on satellite altimeter data (AVISO) and global atlases of temperature and salinity (CARS09), wind stress (SCOW) and wind-driven circulation. Two novel large-scale features governing the upper geostrophic circulation of the South Indian tropical gyre are revealed. First, the seasonal shrinkage of the ocean gyre. This occurs when the South Equatorial Countercurrent (SECC) recirculates before arrival to Sumatra from winter to spring, in apparent synchronization with the annual cycle of the ITF. Second, the open-ocean upwelling is found to vary following seasonality of the overlying geostrophic ocean gyre, a relationship that has not been previously shown for this region. An analysis of major forcing mechanisms suggests that the thermocline ridge results from the constructive interaction of basin-scale wind stress curl, local-scale wind stress forcing and remote forcing driven by Rossby waves of different periodicity: semiannual in the west, under the strong influence of monsoonal winds; and, annual in the east, where the southeasterlies prevail. One exception occurs during winter, when the well-known westward intensification of the upwelling core, the Seychelles Dome, is shown to be largely a response of the wind-driven circulation. Broadly speaking, the seasonal shrinkage of the ocean gyre (and the SCTR) is the one feature that differs most when the geostrophic circulation is compared to the wind-driven Sverdrup circulation. From late autumn to spring, the eastward SECC recirculates early in the east on feeding the westward South Equatorial Current, therefore closing the gyre before arrival to Sumatra. We find this recirculation longitude migrates over 20° and collocates with the westward advance of a zonal thermohaline front emerging from the encounter between (upwelled) Indian Equatorial Water and relatively warmer and fresher Indonesian Throughflow Water. We suggest this front, which we call the Indonesian Throughflow Front, plays an important role as forcing to the tropical gyre, generating southward geostrophic flows that contribute to the early recirculation of the SECC at longitudes more westward than predicted from the barotropic wind-driven circulation. Because our findings are based on time-averaged seasonal fields from 22 years of satellite altimeter data and from about 60 years of non-systematic sampling of ocean temperature and salinity data (CARS09), we stress the importance of further study on the possibility that interanual variability in the seasonal ITF may cause changes in the seasonal resizing of the ocean gyre and its associated upwelling ridge.

Southern Ocean coccolithophore biogeography - controlling factors and implications for global biogeochemical cycles

NASA Astrophysics Data System (ADS)

Nissen, Cara; Vogt, Meike; Münnich, Matthias; Gruber, Nicolas

2017-04-01

Southern Ocean phytoplankton biogeography is important for the biogeochemical cycling of carbon, silicate, and the transport of macronutrients to lower latitudes. With the discovery of the "Great Calcite Belt" (GBC), revealing an unexpectedly high prevalence of calcifying phytoplankton in the subtropical frontal region between 40-55°S, the relative importance of Southern Ocean coccolithophores for phytoplankton biomass, net primary productivity and the carbon cycle need to be revisited. Using a regional high-resolution model with an embedded ecosystem module (ROMS-BEC) for the Southern Ocean (24-78°S) that has been extended to include an explicit representation of coccolithophores, we assess the environmental drivers of Southern Ocean coccolithophore biogeography over the course of the growing season. We thereby focus on biotic interactions and the relative importance of top-down (grazing) versus bottom-up factors (light, nutrient, temperature) controlling growth and abundance. In our simulation, coccolithophores are an important member of the Southern Ocean phytoplankton community, contributing 13% to annually integrated net primary productivity south of 30°S. We estimate the integrated annual calcification rate to account for 40% of the satellite derived global estimate. Modeled coccolithophore biomass is highest in February and March in a latitudinal band between 40-55°S, when diatoms become heavily silicate limited. This region is characterized by a number of divergent fronts with a low Si:Fe ratio of waters supplied to the mixed layer, supporting an increased growth of coccolithophores at the expense of diatoms. We find top down controls to be the major control on the relative abundance of diatoms and coccolithophores in the Southern Ocean. We perform iron and silicate fertilization experiments to assess the effects of changed nutrient availability on coccolithophore abundance in the GCB. We find that changes in nutrient stoichiometry significantly alter phytoplankton community composition, the relative contribution of particulate organic and inorganic carbon, as well as opal to export, and the supply of nutrients to lower latitudes. Consequently, when assessing potential future changes in Southern Ocean coccolithophore abundance and its implications for biogeochemical cycles, both physical (temperature, light, nutrient availability) and chemical (ocean acidification) changes, but also biotic interactions need to be considered.

Rectification of Atmospheric Intraseasonal Oscillations on Seasonal to Interannual Sea Surface Temperature in the Indian Ocean

NASA Astrophysics Data System (ADS)

Duncan, B.; Han, W.

2010-12-01

An ocean general circulation model (the Hybrid Coordinate Ocean Model, HYCOM) is used to examine the rectification of atmospheric intraseasonal oscillations (ISOs) on lower-frequency seasonal to interannual sea surface temperatures (SSTs) in the Indian Ocean (IO). Existing studies have shown that ISOs rectify on low-frequency equatorial surface currents, suggesting that they may also have important impacts on low-frequency SST variability. To evaluate these impacts, a hierarchy of experiments is run with HYCOM that isolates the ocean response to atmospheric forcing by 10-30 day (submonthly), 30-90 day (dominated by the Madden-Julian Oscillation), and 10-90 day (all ISO) events. Other experiments isolate the ocean response to a range of forcing processes including shortwave radiation, precipitation, and winds. Results indicate that ISOs have a non-negligible effect on the seasonal and annual cycles of SST in the Arabian Sea. The maximum seasonal SST variability in the Arabian Sea is 1.6°C, while the ISO-forced seasonal SST variability has a maximum of 0.4°C. Because SSTs in the Arabian Sea are already warm (>28°C), a change of 0.4°C can affect convection there. ISOs also have non-negligible effects on the seasonal variability of SST in the south- and west- equatorial IO. The ISO contribution to the seasonal cycle of mixed layer thickness (hmix) in the eastern equatorial IO has a maximum of 9m, while the total hmix seasonal cycle has a maximum of 14m. ISOs affect the hmix seasonal cycle by up to 10m in the Arabian Sea, where the total seasonal cycle has a maximum of 75m. Further work will seek to explain the causes of this observed rectification of ISOs on seasonal SST and mixed layer variability, and to extend our results to include interannual timescales.

Microbial Ecology of the Dark Ocean above, at, and below the Seafloor†

PubMed Central

Orcutt, Beth N.; Sylvan, Jason B.; Knab, Nina J.; Edwards, Katrina J.

2011-01-01

Summary: The majority of life on Earth—notably, microbial life—occurs in places that do not receive sunlight, with the habitats of the oceans being the largest of these reservoirs. Sunlight penetrates only a few tens to hundreds of meters into the ocean, resulting in large-scale microbial ecosystems that function in the dark. Our knowledge of microbial processes in the dark ocean—the aphotic pelagic ocean, sediments, oceanic crust, hydrothermal vents, etc.—has increased substantially in recent decades. Studies that try to decipher the activity of microorganisms in the dark ocean, where we cannot easily observe them, are yielding paradigm-shifting discoveries that are fundamentally changing our understanding of the role of the dark ocean in the global Earth system and its biogeochemical cycles. New generations of researchers and experimental tools have emerged, in the last decade in particular, owing to dedicated research programs to explore the dark ocean biosphere. This review focuses on our current understanding of microbiology in the dark ocean, outlining salient features of various habitats and discussing known and still unexplored types of microbial metabolism and their consequences in global biogeochemical cycling. We also focus on patterns of microbial diversity in the dark ocean and on processes and communities that are characteristic of the different habitats. PMID:21646433

Evidence for arsenic metabolism and cycling by microorganisms 2.7 billion years ago

NASA Astrophysics Data System (ADS)

Sforna, Marie Catherine; Philippot, Pascal; Somogyi, Andrea; van Zuilen, Mark A.; Medjoubi, Kadda; Schoepp-Cothenet, Barbara; Nitschke, Wolfgang; Visscher, Pieter T.

2014-11-01

The ability of microbes to metabolize arsenic may have emerged more than 3.4 billion years ago. Some of the modern environments in which prominent arsenic metabolism occurs are anoxic, as were the Precambrian oceans. Early oceans may also have had a relatively high abundance of arsenic. However, it is unclear whether arsenic cycling occurred in ancient environments. Here we assess the chemistry and nature of cell-like globules identified in salt-encrusted portions of 2.72-billion-year-old fossil stromatolites from Western Australia. We use Raman spectroscopy and X-ray fluorescence to show that the globules are composed of organic carbon and arsenic (As). We argue that our data are best explained by the occurrence of a complete arsenic cycle at this site, with As(III) oxidation and As(V) reduction by microbes living in permanently anoxic conditions. We therefore suggest that arsenic cycling could have occurred more widely in marine environments in the several hundred million years before the Earth’s atmosphere and shallow oceans were oxygenated.

76 FR 13999 - Meeting of the Ocean Research and Resources Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-15

..., and other current issues in the ocean science and management communities; including, the review and... DEPARTMENT OF DEFENSE Department of the Navy Meeting of the Ocean Research and Resources Advisory Panel AGENCY: Department of the Navy, DoD. ACTION: Notice of open meeting. SUMMARY: The Ocean Research...

76 FR 22083 - Meeting of the Ocean Research and Resources Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-20

... other current issues in the ocean science and management communities; including, the review and... DEPARTMENT OF DEFENSE Department of the Navy Meeting of the Ocean Research and Resources Advisory Panel AGENCY: Department of the Navy, DoD. ACTION: Notice of open meeting. SUMMARY: The Ocean Research...

Phosphorus in the ocean and marine sediments: similarities between present and past processes

NASA Astrophysics Data System (ADS)

Tamburini, F.

2004-12-01

Because phosphorus (P) is an essential nutrient, geochemical research has focused over the years on understanding the different aspects of the P cycle in the oceans, from the global to microbial scale. In the last 40 years, giant phosphorite deposits were largely studied, and their episodic occurrence in the geological record was alternatively interpreted as the product of shallow water environments, high productivity, low-sedimentation rates, and/or changes in sea level. Although research has focused more recently on the oceanic burial fluxes and residence time of P, there is still a general agreement on the need for more data. Thanks to new analytical techniques, allowing the detection of small quantities of phosphate (on the order of ?mol/g), and to the increased availability of sediment cores, P-bearing sediments have been found everywhere beneath the ocean floor. This finding has changed our understanding of P behavior in the ocean, and is redefining the role of P as an important nutrient, for example, over glacial-interglacial time scales. I will present glacial-interglacial reconstructions of burial and benthic fluxes of P, with the goal of understanding to which extent the P cycle is linked to global processes. The data, averaged to the whole ocean, indicate that burial fluxes of reactive P during glacial times are not considerably lower than during interglacials. This observation could lead to the conclusion that no changes occurred in P cycle on glacial-interglacial timescales and, therefore, that C cycle and climate variations were independent of P cycle. However, when the benthic flux estimates are taken into account, a different picture arises. During low sea level periods, the redistribution of sediments from shallow to deep waters, due to the reduction of the continental margin surface, fostered P regeneration during settling of organic matter. Even if P burial fluxes remain fairly constant, the oceanic phosphate inventory of glacial bottom waters was probably higher. On a different time scale, the shift in P behavior between glacial and interglacial periods could have been promoted by conditions similar to those that led to the formation of phosphorite deposits, which are abundant in the geological past but rare today.

Atmospheric Dissolved Iron Depostiion to the Global Oceans: Effects of Oxalate-Promoted Fe Dissolution, Photochemical Redox Cycling, and Dust Mineralogy

NASA Technical Reports Server (NTRS)

Johnson, M. S.; Meskhidze, N.

2013-01-01

Mineral dust deposition is suggested to be a significant atmospheric supply pathway of bioavailable iron (Fe) to Fe-depleted surface oceans. In this study, mineral dust and dissolved Fe (Fed) deposition rates are predicted for March 2009 to February 2010 using the 3-D chemical transport model GEOS-Chem implemented with a comprehensive dust-Fe dissolution scheme. The model simulates Fed production during the atmospheric transport of mineral dust taking into account inorganic and organic (oxalate)-promoted Fe dissolution processes, photochemical redox cycling between ferric (Fe(III)) and ferrous (Fe(II)) forms of Fe, dissolution of three different Fe-containing minerals (hematite, goethite, and aluminosilicates), and detailed mineralogy of windblown dust from the major desert regions. Our calculations suggest that during the yearlong simulation is approximately 0.26 Tg (1 Tg = 1012 g) of Fed was deposited to global oceanic regions. Compared to simulations only taking into account proton-promoted Fe dissolution, the addition of oxalate to the dust-Fe mobilization scheme increased total annual model-predicted Fed deposition to global oceanic regions by approximately 75%. The implementation of Fe(II)/Fe(III) photochemical redox cycling in the model allows for the distinction between different oxidation states of deposited Fed. Our calculations suggest that during the daytime, large fractions of Fed deposited to the global oceans is likely to be in Fe(II) form, while nocturnal fluxes of Fed are largely in Fe(III) form. Model simulations also show that atmospheric fluxes of Fed can be strongly influenced by the mineralogy of Fe-containing compounds. This study shows that Fed deposition to the oceans is controlled by total dust-Fe mass concentrations, mineralogy, the surface area of dust particles, atmospheric chemical composition, cloud processing, and meteorological parameters and exhibits complex and spatiotemporally variable patterns. Our study suggests that the explicit model representation of individual processes leading to Fed production within mineral dust are needed to improve the understanding of the atmospheric Fe cycle, and quantify the effect of dust-Fe on ocean biological productivity, carbon cycle, and climate.

The Effect of Thermal Cycling on Crystal-Liquid Separation During Lunar Magma Ocean Differentiation

NASA Technical Reports Server (NTRS)

Mills, Ryan D.

2013-01-01

Differentiation of magma oceans likely involves a mixture of fractional and equilibrium crystallization [1]. The existence of: 1) large volumes of anorthosite in the lunar highlands and 2) the incompatible- rich (KREEP) reservoir suggests that fractional crystallization may have dominated during differentiation of the Moon. For this to have occurred, crystal fractionation must have been remarkably efficient. Several authors [e.g. 2, 3] have hypothesized that equilibrium crystallization would have dominated early in differentiation of magma oceans because of crystal entrainment during turbulent convection. However, recent numerical modeling [4] suggests that crystal settling could have occurred throughout the entire solidification history of the lunar magma ocean if crystals were large and crystal fraction was low. These results indicate that the crystal size distribution could have played an important role in differentiation of the lunar magma ocean. Here, I suggest that thermal cycling from tidal heating during lunar magma ocean crystallization caused crystals to coarsen, leading to efficient crystal-liquid separation.

Radiocarbon constraints on the glacial ocean circulation and its impact on atmospheric CO2

NASA Astrophysics Data System (ADS)

Skinner, L. C.; Primeau, F.; Freeman, E.; de La Fuente, M.; Goodwin, P. A.; Gottschalk, J.; Huang, E.; McCave, I. N.; Noble, T. L.; Scrivner, A. E.

2017-07-01

While the ocean's large-scale overturning circulation is thought to have been significantly different under the climatic conditions of the Last Glacial Maximum (LGM), the exact nature of the glacial circulation and its implications for global carbon cycling continue to be debated. Here we use a global array of ocean-atmosphere radiocarbon disequilibrium estimates to demonstrate a ~689+/-53 14C-yr increase in the average residence time of carbon in the deep ocean at the LGM. A predominantly southern-sourced abyssal overturning limb that was more isolated from its shallower northern counterparts is interpreted to have extended from the Southern Ocean, producing a widespread radiocarbon age maximum at mid-depths and depriving the deep ocean of a fast escape route for accumulating respired carbon. While the exact magnitude of the resulting carbon cycle impacts remains to be confirmed, the radiocarbon data suggest an increase in the efficiency of the biological carbon pump that could have accounted for as much as half of the glacial-interglacial CO2 change.

Design and development of a community carbon cycle benchmarking system for CMIP5 models

NASA Astrophysics Data System (ADS)

Mu, M.; Hoffman, F. M.; Lawrence, D. M.; Riley, W. J.; Keppel-Aleks, G.; Randerson, J. T.

2013-12-01

Benchmarking has been widely used to assess the ability of atmosphere, ocean, sea ice, and land surface models to capture the spatial and temporal variability of observations during the historical period. For the carbon cycle and terrestrial ecosystems, the design and development of an open-source community platform has been an important goal as part of the International Land Model Benchmarking (ILAMB) project. Here we designed and developed a software system that enables the user to specify the models, benchmarks, and scoring systems so that results can be tailored to specific model intercomparison projects. We used this system to evaluate the performance of CMIP5 Earth system models (ESMs). Our scoring system used information from four different aspects of climate, including the climatological mean spatial pattern of gridded surface variables, seasonal cycle dynamics, the amplitude of interannual variability, and long-term decadal trends. We used this system to evaluate burned area, global biomass stocks, net ecosystem exchange, gross primary production, and ecosystem respiration from CMIP5 historical simulations. Initial results indicated that the multi-model mean often performed better than many of the individual models for most of the observational constraints.

Biogeochemistry of Recently Discovered Oxygen-Depleted Mesoscale Eddies in the Open Eastern Tropical North Atlantic

NASA Astrophysics Data System (ADS)

Fiedler, B.; Grundle, D.; Löscher, C. R.; Schütte, F.; Hauss, H.; Karstensen, J.; Silva, P.; Koertzinger, A.

2016-02-01

Severely oxygen-depleted mesoscale features in the open eastern tropical North Atlantic, which are formed in the Mauritanian upwelling region, were discovered only recently. So far, few remote surveys conducted with autonomous platforms such as moorings, underwater gliders and profiling floats have provided a very first insight into these mesoscale eddies. Due to their hydrographic properties such water bodies are well isolated from ambient waters and therefore can develop severe near-surface oxygen deficits. In this presentation we show results from the first-ever biogeochemical survey of one of these anticyclonic mode-water eddies conducted in spring 2014 at the Cape Verde Ocean Observatory (CVOO) off West Africa. Very low oxygen concentrations of 4.5 µmol kg-1 associated with a CO2 partial pressure of 1164 µatm were found close to the core of the eddy (at 100 m depth). Measurements for nitrate and phosphate also show exceptional high values. Findings point to rapid oxygen consumption through remineralization of organic matter along with depressed lateral mixing of this water body. Indeed, rates for oxygen utilization (OUR) were found to be enhanced when compared to known values in the Atlantic. A closer look into the carbonate system inside the eddýs core revealed disadvantageous conditions for calcifying organisms with the pH dropping down to 7.6 and the Aragonite saturation level reaching 1 at the lower boundary of the euphotic zone. Finally, strong indications for a shift in nitrogen cycling in the core of the eddy from nitrification towards denitrification were found based on gene abundance and N2O-isotope analyses. To our knowledge such severe hypoxic and even suboxic near-surface conditions along with active denitrification have never been reported before in the open Atlantic Ocean.

Ocean Carbon Cycle Feedbacks Under Negative Emissions

NASA Astrophysics Data System (ADS)

Schwinger, Jörg; Tjiputra, Jerry

2018-05-01

Negative emissions will most likely be needed to achieve ambitious climate targets, such as limiting global warming to 1.5°. Here we analyze the ocean carbon-concentration and carbon-climate feedback in an Earth system model under an idealized strong CO2 peak and decline scenario. We find that the ocean carbon-climate feedback is not reversible by means of negative emissions on decadal to centennial timescales. When preindustrial surface climate is restored, the oceans, due to the carbon-climate feedback, still contain about 110 Pg less carbon compared to a simulation without climate change. This result is unsurprising but highlights an issue with a widely used carbon cycle feedback metric. We show that this metric can be greatly improved by using ocean potential temperature as a proxy for climate change. The nonlinearity (nonadditivity) of climate and CO2-driven feedbacks continues to grow after the atmospheric CO2 peak.

Atmospheric Transport and Input of Iron to the Southern Ocean

NASA Astrophysics Data System (ADS)

Tindale, N. W.

2002-12-01

While Australia is not generally considered to be a major source of mineral dust to the atmosphere, at least compared to Asian and African desert regions, it does appear to be the main source of mineral material to the Southern Ocean region south of Australia and New Zealand. In common with most of the greater Southern Ocean, this region contains high nitrate, low chlorophyll (HNLC) waters. Recent open ocean iron enrichment experiments in this region have demonstrated that phytoplankton growth and biomass are limited by iron availability. However the flux of atmospheric iron to this open ocean region is poorly known with very few direct measurements of mineral aerosol levels and input. Using mineral aerosol samples collected on Macquarie Island and at Cape Grim, together with other chemical data, air mass trajectories and satellite data, the spatial and temporal variability of aerosol iron transport and input to the Southern Ocean region south of Australia is estimated.

FP7 GLOWASIS - A new collaborative project aimed at pre-validation of a GMES Global Water Scarcity Information Service

NASA Astrophysics Data System (ADS)

Westerhoff, R.; Levizzani, V.; Pappenberger, F.; de Roo, A.; Lange, R. D.; Wagner, W.; Bierkens, M. F.; Ceran, M.; Weerts, A.; Sinclair, S.; Miguez-Macho, G.; Langius, E.; Glowasis Team

2011-12-01

The main objective of the project GLOWASIS is to pre-validate a GMES Global Service for Water Scarcity Information. It will be set up as a one-stop-shop portal for water scarcity information, in which focus is put on: - monitoring data from satellites and in-situ sensors; - improving forecasting models with improved monitoring data; - linking statistical water data in forecasting; - promotion of GMES Services and European satellites. In European and global pilots on the scale of river catchments it combines hydrological models with in-situ and satellite derived water cycle information, as well as government ruled statistical water demand data. By linking water demand and supply in three pilot studies with existing platforms (European Drought Observatory and PCR-GLOBWB) for medium- and long-term forecasting in Europe, Africa and worldwide, GLOWASIS' information contributes both in near-real time reporting for emerging drought events as well as in provision of climate change time series. By combining complex water cycle variables, governmental issues and economic relations with respect to water demand, GLOWASIS will aim for the needed streamlining of the wide variety of important water scarcity information. More awareness for the complexity of the water scarcity problem will be created and additional capabilities of satellite-measured water cycle parameters can be promoted. The service uses data from GMES Core Services LMCS Geoland2 and Marine Core Service MyOcean (land use, soil moisture, soil sealing, sea level), in-situ data from GEWEX' initiatives (i.e. International Soil Moisture network), agricultural and industrial water use and demand (statistical - AQUASTAT, SEEAW and modelled) and additional water-cycle information from existing global satellite services. In-depth interviews with a.o. EEA and the Australian Bureau of Meteorology are taking place. GLOWASIS will aim for an open source and open-standard information portal on water scarcity and use of modern media (forums, Twitter, etc). Infrastructure of the GLOWASIS portal is set up for dissemination and inclusion of current and future innovative and integrated multi-purpose products for research & operational applications with open standards. The project has started in January 2011 and the duration is 24 months.

The global distribution and dynamics of chromophoric dissolved organic matter.

PubMed

Nelson, Norman B; Siegel, David A

2013-01-01

Chromophoric dissolved organic matter (CDOM) is a ubiquitous component of the open ocean dissolved matter pool, and is important owing to its influence on the optical properties of the water column, its role in photochemistry and photobiology, and its utility as a tracer of deep ocean biogeochemical processes and circulation. In this review, we discuss the global distribution and dynamics of CDOM in the ocean, concentrating on developments in the past 10 years and restricting our discussion to open ocean and deep ocean (below the main thermocline) environments. CDOM has been demonstrated to exert primary control on ocean color by its absorption of light energy, which matches or exceeds that of phytoplankton pigments in most cases. This has important implications for assessing the ocean biosphere via ocean color-based remote sensing and the evaluation of ocean photochemical and photobiological processes. The general distribution of CDOM in the global ocean is controlled by a balance between production (primarily microbial remineralization of organic matter) and photolysis, with vertical ventilation circulation playing an important role in transporting CDOM to and from intermediate water masses. Significant decadal-scale fluctuations in the abundance of global surface ocean CDOM have been observed using remote sensing, indicating a potentially important role for CDOM in ocean-climate connections through its impact on photochemistry and photobiology.

Regional contributions of ocean iron fertilization to atmospheric CO2 changes during the last glacial termination

NASA Astrophysics Data System (ADS)

Opazo, N. E.; Lambert, F.

2017-12-01

Mineral dust aerosols affect climate directly by changing the radiative balance of the Earth, and indirectly by acting as cloud condensation nuclei and by affecting biogeochemical cycles. The impact on marine biogeochemical cycles is primarily through the supply of micronutrients such as iron to nutrient-limited regions of the oceans. Iron fertilization of High Nutrient Low Chlorophyll (HNLC) regions of the oceans is thought to have significantly affected the carbon cycle on glacial-interglacial scales and contributed about one fourth of the 80-100 ppm lowering of glacial atmospheric CO2 concentrations.In this study, we quantify the effect of global dust fluxes on atmospheric CO2 using the cGENIE model, an Earth System Model of Intermediate Complexity with emphasis on the carbon cycle. Global Holocene and Last Glacial Maximum (LGM) dust flux fields were obtained from both dust model simulations and reconstructions based on observational data. The analysis was performed in two stages. In the first instance, we produced 8 global intermediate dust flux fields between Holocene and LGM and simulated the atmospheric CO2 drawdown due to these 10 dust levels. In the second stage, we only changed dust flux levels in specific HNLC regions to isolate the effect of these ocean basins. We thus quantify the contribution of the South Atlantic, the South Pacific, the North Pacific, and the Central Pacific HNLC regions to the total atmospheric CO2 difference due to iron fertilization of the Earth's oceans.

Molecular-level dynamics of refractory dissolved organic matter

NASA Astrophysics Data System (ADS)

Niggemann, J.; Gerdts, G.; Dittmar, T.

2012-04-01

Refractory dissolved organic matter (DOM) accounts for most of the global oceanic organic carbon inventory. Processes leading to its formation and factors determining its stability are still largely unknown. We hypothesize that refractory DOM carries a universal molecular signature. Characterizing spatial and temporal variability in this universal signature is a key to understanding dynamics of refractory DOM. We present results from a long-term study of the DOM geo-metabolome in the open North Sea. Geo-metabolomics considers the entity of DOM as a population of compounds, each characterized by a specific function and reactivity in the cycling of energy and elements. Ten-thousands of molecular formulae were identified in DOM by ultrahigh resolution mass spectrometry analysis (FT-ICR-MS, Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry). The DOM pool in the North Sea was influenced by a complex interplay of processes that produced, transformed and degraded dissolved molecules. We identified a stable fraction in North Sea DOM with a molecular composition similar to deep ocean DOM. Molecular-level changes in this stable fraction provide novel information on dynamics and interactions of refractory DOM.

Geodynamic models of the Wilson Cycle: From rifts to mountains to rifts

NASA Astrophysics Data System (ADS)

Buiter, Susanne; Tetreault, Joya; Torsvik, Trond

2015-04-01

The Wilson Cycle theory that oceans close and reopen along the former suture is a fundamental concept in plate tectonics. The theory suggests that subduction initiates at a passive margin, closing the ocean, and that future continental extension localises at the ensuing collision zone. Each stage of the Wilson Cycle will therefore be characterised by inherited structural and thermal heterogeneities. Here we investigate the role of Wilson Cycle inheritance by considering the influence of (1) passive margin structure on continental collision and (2) collision zones on passive margin formation. Passive margins may be preferred locations for subduction initiation because inherited faults and areas of exhumed serpentinized mantle may weaken a margin enough to localise shortening. If subduction initiates at a passive margin, the shape and structure of the passive margins will affect future continental collision. Our review of present-day passive margins along the Atlantic and Indian Oceans reveals that most passive margins are located on former collision zones. Continental break-up occurs on relatively young sutures, such as Morocco-Nova Scotia, and on very old sutures, such as the Greenland-Labrador and East Antarctica-Australia systems. This implies that it is not always post-collisional collapse that initiates the extensional phase of a Wilson Cycle. We highlight the impact of collision zone inheritance on continental extension and rifted margin architecture. We show numerical experiments of one Wilson Cycle of subduction, collision, and extension. Subduction initiates at a tapered passive margin. Closure of a 60 Ma ocean leads to continental collision and slab break-off, followed by some tens of kilometres of slab eduction. Mantle flow above the sinking detached slab enhances deformation in the rift area. The resulting rift exposes not only continental crust, but also subduction-related sediments and oceanic crust remnants. Renewed subduction in the post-collision phase is enabled by lithosphere delamination and slab rollback, leading to back-arc extension in a style similar to the Tyrrhenian Sea.

Glacial CO2 Cycles: A Composite Scenario

NASA Astrophysics Data System (ADS)

Broecker, W. S.

2015-12-01

There are three main contributors to the glacial drawdown of atmospheric CO2 content: starvation of the supply of carbon to the ocean-atmosphere reservoir, excess CO2 storage in the deep sea, and surface-ocean cooling. In this talk, I explore a scenario in which all three play significant roles. Key to this scenario is the assumption that deep ocean storage is related to the extent of nutrient stratification of the deep Atlantic. The stronger this stratification, the larger the storage of respiration CO2. Further, it is my contention that the link between Milankovitch insolation cycles and climate is reorganizations of the ocean's thermohaline circulation leading to changes in the deep ocean's CO2 storage. If this is the case, the deep Atlantic d13C record kept in benthic foraminifera shells tells us that deep ocean CO2 storage follows Northern Hemisphere summer insolation cycles and thus lacks the downward ramp so prominent in the records of sea level, benthic 18O and CO2. Rather, the ramp is created by the damping of planetary CO2 emissions during glacial time intervals. As it is premature to present a specific scenario, I provide an example as to how these three contributors might be combined. As their magnitudes and shapes remain largely unconstrained, the intent of this exercise is to provoke creative thinking.

An examination of the role of particles in oceanic mercury cycling.

PubMed

Lamborg, Carl H; Hammerschmidt, Chad R; Bowman, Katlin L

2016-11-28

Recent models of global mercury (Hg) cycling have identified the downward flux of sinking particles in the ocean as a prominent Hg removal process from the ocean. At least one of these models estimates the amount of anthropogenic Hg in the ocean to be about 400 Mmol, with deep water formation and sinking fluxes representing the largest vectors by which pollutant Hg is able to penetrate the ocean interior. Using data from recent cruises to the Atlantic, we examined the dissolved and particulate partitioning of Hg in the oceanic water column as a cross-check on the hypothesis that sinking particle fluxes are important. Interestingly, these new data suggest particle-dissolved partitioning ( K d ) that is approximately 20× greater than previous estimates, which thereby challenges certain assumptions about the scavenging and active partitioning of Hg in the ocean used in earlier models. For example, the new particle data suggest that regenerative scavenging is the most likely mechanism by which the association of Hg and particles occurs.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

The Aerosol/Cloud/Ecosystems Mission (ACE)

NASA Technical Reports Server (NTRS)

Schoeberl, Mark

2008-01-01

The goals and measurement strategy of the Aerosol/Cloud/Ecosystems Mission (ACE) are described. ACE will help to answer fundamental science questions associated with aerosols, clouds, air quality and global ocean ecosystems. Specifically, the goals of ACE are: 1) to quantify aerosol-cloud interactions and to assess the impact of aerosols on the hydrological cycle and 2) determine Ocean Carbon Cycling and other ocean biological processes. It is expected that ACE will: narrow the uncertainty in aerosol-cloud-precipitation interaction and quantify the role of aerosols in climate change; measure the ocean ecosystem changes and precisely quantify ocean carbon uptake; and, improve air quality forecasting by determining the height and type of aerosols being transported long distances. Overviews are provided of the aerosol-cloud community measurement strategy, aerosol and cloud observations over South Asia, and ocean biology research goals. Instruments used in the measurement strategy of the ACE mission are also highlighted, including: multi-beam lidar, multiwavelength high spectra resolution lidar, the ocean color instrument (ORCA)--a spectroradiometer for ocean remote sensing, dual frequency cloud radar and high- and low-frequency micron-wave radiometer. Future steps for the ACE mission include refining measurement requirements and carrying out additional instrument and payload studies.

A one ocean model of biodiversity

NASA Astrophysics Data System (ADS)

O'Dor, Ronald K.; Fennel, Katja; Berghe, Edward Vanden

2009-09-01

The history of life is written in the ocean, and the history of the ocean is written in DNA. Geologists have shown us that hundreds of millions of years of ocean history can be revealed from records of a single phylum in cores of mud from abyssal plains. We are now accumulating genetic tools to unravel the relationships of hundreds of phyla to track this history back billions of years. The technologies demonstrated by the Census of Marine Life (CoML) mean that the ocean is no longer opaque or unknowable. The secrets of the largest component of the biosphere are knowable. The cost of understanding the history of ocean life is not cheap, but it is also not prohibitive. A transparent, open ocean is available for us to use to understand ourselves. This article develops a model of biodiversity equilibration in a single, physically static ocean as a step towards biodiversity in physically complex real oceans. It attempts to be quantitative and to simultaneously account for biodiversity patterns from bacteria to whales focusing on emergent properties rather than details. Biodiversity reflects long-term survival of DNA sequences, stabilizing "ecosystem services" despite environmental change. In the ocean, mechanisms for ensuring survival range from prokaryotes maintaining low concentrations of replicable DNA throughout the ocean volume, anticipating local change, to animals whose mobility increases with mass to avoid local change through movement. Whales can reach any point in the ocean in weeks, but prokaryotes can only diffuse. The high metabolic costs of mobility are offset by the dramatically lower number of DNA replicates required to ensure survival. Reproduction rates probably scale more or less inversely with body mass. Bacteria respond in a week, plankton in a year, whales in a century. We generally lack coherent theories to explain the origins of animals (metazoans) and the contributions of biodiversity to ecosystems. The One Ocean Model suggests that mobile metazoans paved the way for their own energetic life styles by decreasing the amount of primary production sinking to feed the benthic anaerobic prokaryotes. Increasing metazoan mobility and diversity ensured that less and less production sank and accelerated development of the aerobic oceans they require. High biodiversity among middle-sized organisms stabilizes the system, but rapid environmental changes can decrease diversity in a positive feedback loop ending in mass extinction events and the return of the anaerobes. The oceans have gone through this cycle several times. Global warming may be a mild flu compared to "the revenge of the microbes".

Distribution and structure of pranktonic Archaea in the Arctic Ocean using 2008 - 2010 R/V Mirai cruise samples

NASA Astrophysics Data System (ADS)

Amano (Sato), C.; Akiyama, S.; Uchida, M.; Utsumi, M.

2011-12-01

Recent molecular biological techniques indicate that there is widely spreading marine planktonic Archaea in the world's ocean under euphotic zone, and those microbial metabolisms are now recognized the drive forces of the world ocean geochemical cycling. In addition, after the discovery of large amount of marine Archaea, it is pointed out to an accurate calculation of the ocean carbon cycling that the grasp of the Archaea quantitive distribution and their methabolism are indispensable. Remarkably, part of marine Archaea (Crenarchaeota) certainly has carbon fixing ability, thus there is currently great interest in the marine Archaea for getting to understand the carbon cycling. In this study, we evaluated the Archaeal spatial distribution and their biomass in the Pacific sector of the Arctic Ocean, where is the Archaeal quantitative data was less and strongly needed to reveal the marine bacterial carbon cycling due to resent changing the Arctic region such as extensive melting ice. The Arctic Ocean cruise by R/V MIRAI was done from August to October in 2008 - 2010 in the Chukchi Sea, Canada Basin and East Siberian Sea. In these cruises, vertical seawater samples were collected with 12 L Niskin bottles with CTD system at total 30 stations to investigate the distributions of bacterial population density. The Catalyzed Reporter Deposition Fluorescence in situ hybridization (CARD-FISH) technique targeting Crenarchaeal, Euryarchaeal and Eubacterial rRNA was used for identifying and enumerating marine microbial cells under florescent microscope. These cells were counted and measured the size, and calculated the biomass. From the results, in the Pacific sector of the Arctic Ocean, it was determined that the fraction of Archaea was abundant under euphotic zone like as other oceans, and the vertical distribution of planktonic Archaea were obviously different by each sea area. Especially in East Siberian Sea, the fraction of Crenarchaeota was relatively high near bottom reaching 40% of total detected bacteria. And it was found that Crenarchaeota was less dominant in the fresh surface layer contrasted to Euryarchaeota. This Archaeal distribution characteristic founded out in the Pacific sector of the Arctic Ocean would be come from obvious water mass structure and environmental factors. This result should connect to understand whole Arhcaeal quantitative knowledge in the world ocean.

The OTEC connection - Power from the sea

NASA Astrophysics Data System (ADS)

Petty, D.

1980-02-01

OTEC is discussed as a means of contributing to United States energy self-sufficiency. The technology involved in the conversion of ocean thermal gradients found in tropical regions to electricity transmittable by submarine cable is examined, with attention given to the operating principles of open- and closed-cycle Rankine engines and design considerations for the evaporators, condensers and heat exchangers. The environmental impact and economics of OTEC are considered, and Department of Energy research projects in areas of OTEC technology including heat transfer, biofouling, environmental assessment, underwater electrical transmission and mooring and test plants are indicated. It is pointed out that US islands presently offer excellent markets for early commercial OTEC plants, with Gulf Coast markets requiring further technology developments to be economically attractive.

An Autonomous Ozone Instrument for Atmospheric Measurements from Ocean Buoys

NASA Astrophysics Data System (ADS)

Hintsa, E. J.; Rawlins, W. T.; Sholkovitz, E. R.; Hosom, D. S.; Allsup, G. P.; Purcell, M. J.; Scott, D. R.; Mulhall, P.

2002-05-01

Tropospheric ozone is an oxidant, a greenhouse gas, and a pollutant. Because of its adverse health effects, there are numerous monitoring stations on land but none over the oceans. We have built an ozone instrument for deployment anywhere at sea from ocean buoys, to study ozone chemistry over the oceans, intercontinental transport of pollution, diurnal and seasonal cycles of ozone, and to make baseline and long-term time series measurements of ozone in remote locations. The instrument uses direct (Beer's Law) absorption of UV radiation in a dual-path cell, with ambient and ozone-free air alternately switched between the two paths, to measure ozone. Ozone can be measured at a rate of 1 Hz, with a precision of about 1 ppb at sea level. The air inlet and outlet have valves which close automatically under high wind conditions or rain to protect the ozone sensor. The instrument has been packaged for deployment at sea, and tested on a 3-meter discus buoy with other instruments in coastal waters in fall 2001. It can operate autonomously or be controlled via line-of-sight modem or a satellite link. We will present the details of the instrument, and laboratory and buoy test data from its first deployment, including a comparison with a nearby ozone monitoring station on land. We will also present an evaluation of the instrument's performance and describe plans for improvements. In summer 2002, the ozone measurement system will be operated at the Martha's Vineyard Coastal Observatory; in the future we anticipate deploying on the Bermuda Testbed Mooring, followed by use on the open ocean to measure long-range transport of ozone.

Global reductions in seafloor biomass in response to climate change.

PubMed

Jones, Daniel O B; Yool, Andrew; Wei, Chih-Lin; Henson, Stephanie A; Ruhl, Henry A; Watson, Reg A; Gehlen, Marion

2014-06-01

Seafloor organisms are vital for healthy marine ecosystems, contributing to elemental cycling, benthic remineralization, and ultimately sequestration of carbon. Deep-sea life is primarily reliant on the export flux of particulate organic carbon from the surface ocean for food, but most ocean biogeochemistry models predict global decreases in export flux resulting from 21st century anthropogenically induced warming. Here we show that decadal-to-century scale changes in carbon export associated with climate change lead to an estimated 5.2% decrease in future (2091-2100) global open ocean benthic biomass under RCP8.5 (reduction of 5.2 Mt C) compared with contemporary conditions (2006-2015). Our projections use multi-model mean export flux estimates from eight fully coupled earth system models, which contributed to the Coupled Model Intercomparison Project Phase 5, that have been forced by high and low representative concentration pathways (RCP8.5 and 4.5, respectively). These export flux estimates are used in conjunction with published empirical relationships to predict changes in benthic biomass. The polar oceans and some upwelling areas may experience increases in benthic biomass, but most other regions show decreases, with up to 38% reductions in parts of the northeast Atlantic. Our analysis projects a future ocean with smaller sized infaunal benthos, potentially reducing energy transfer rates though benthic multicellular food webs. More than 80% of potential deep-water biodiversity hotspots known around the world, including canyons, seamounts, and cold-water coral reefs, are projected to experience negative changes in biomass. These major reductions in biomass may lead to widespread change in benthic ecosystems and the functions and services they provide. © 2013 The Authors Global Change Biology Published by John Wiley & Sons Ltd.

Sources and levels of ambient ocean sound near the antarctic peninsula

DOE PAGES

Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Stafford, Kathleen M.; ...

2015-04-14

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10–20 dB higher in the open,more » deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue ( Balaenoptera musculus) and fin ( B. physalus) whales also dominate the long-term spectra records in the 15–28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean.« less

Distribution and Magnitude of Dinitrogen Fixation in the Eastern Tropical North Pacific Oxygen Deficient Zone.

NASA Astrophysics Data System (ADS)

Selden, C.; Mulholland, M. R.; Widner, B.; Bernhardt, P. W.; Macías Tapia, A.; Jayakumar, A.

2016-12-01

The Eastern Tropical North Pacific Ocean (ETNP) hosts one of the world's three major open ocean oxygen deficient zones (ODZs). Hotspots for fixed nitrogen (N) loss processes, ODZs have classically been discounted as areas of significant dinitrogen (N2) fixation, the microbe-mediated reduction of N2 to ammonium (NH4+), which has historically been ascribed primarily to euphotic, nutrient-deplete tropical waters. Challenging this paradigm, active expression of nifH (the dinitrogen reductase structural gene) has recently been documented in the ETNP, Eastern Tropical South Pacific, and Arabian Sea ODZs, implying a closer coupling of fixed nitrogen input and loss processes than previously thought. Here, we report rates of N­2 fixation measured in the ETNP ODZ along vertical gradients of oxygen, light, and dissolved N concentrations. Detailed vertical profiles of N2 fixation rates and dissolved N concentrations made within the ODZ were compared with similar profiles from oxic waters outside the ODZ. In addition, different organic carbon sources were investigated as potential rate-limiting factors for N2 fixation in sub-euphotic waters. By establishing the magnitude and distribution of N­2 fixation in the ETNP ODZ, this study contributes to current understanding of N cycling in anoxic and aphotic waters, and serves to elucidate nuances in the global N budget, enabling more accurate biogeochemical modeling. Understanding these processes in present day ODZs is crucial for predicting how ongoing anthropogenic intensification of coastal ODZs will alter biogeochemical cycles in the future.

Open cycle ocean thermal energy conversion steam control and bypass system

DOEpatents

Wittig, J. Michael; Jennings, Stephen J.

1980-01-01

Two sets of hinged control doors for regulating motive steam flow from an evaporator to a condenser alternatively through a set of turbine blades in a steam bypass around the turbine blades. The evaporator has a toroidal shaped casing situated about the turbine's vertical axis of rotation and an outlet opening therein for discharging motive steam into an annular steam flow path defined between the turbine's radially inner and outer casing structures. The turbine blades extend across the steam flow path intermediate the evaporator and condenser. The first set of control doors is arranged to prevent steam access to the upstream side of the turbine blades and the second set of control doors acts as a bypass around the blades so as to maintain equilibrium between the evaporator and condenser during non-rotation of the turbine. The first set of control doors preferably extend, when closed, between the evaporator casing and the turbine's outer casing and, when open, extend away from the axis of rotation. The second set of control doors preferably constitute a portion of the turbine's outer casing downstream from the blades when closed and extend, when open, toward the axis of rotation. The first and second sets of control doors are normally held in the open and closed positions respectively by locking pins which may be retracted upon detecting an abnormal operating condition respectively to permit their closing and opening and provide steam flow from the evaporator to the condenser.

Reactive Gaseous Mercury Formation Over The North Pacific Ocean: Influence Of Environmental Parameters On Elemental Mercury Oxidation In The Marine Boundary Layer

NASA Astrophysics Data System (ADS)

Laurier, F. J.

2002-12-01

Global mercury models have identified wet and dry particle deposition and evasion of dissolved gaseous mercury from the ocean and from land as key controls over global mercury cycling (1,2). Recent ocean studies (3,4) however, have indicated that estimated mercury evasion rates from the ocean substantially exceed estimated deposition. Oxidized reactive gaseous mercury species (RGHg) are now known to play a major role in the global mercury cycle (2,5). RGHg species are water-soluble, exhibit a much shorter atmospheric lifetime than elemental mercury, and contribute to a large extent to atmospheric mercury deposition (2,3,6). Although recent global mercury models have accounted for the dry deposition of RGHg derived from point source emissions (6,7), the formation and deposition of RGHg in remote areas have not been incorporated. We suggest that the oxidation of elemental mercury over the ocean, by gas phase or heterogeneous reactions, is an important part the global mercury cycle. In agreement with previous studies (3,8,9) our recent data from atmospheric collections over the North Pacific Ocean support the notion of enhanced oxidation in the marine boundary layer. Our results show an inverse correlation between RGHg production and ozone, and a diurnal cycle with highest concentrations during periods of highest UV irradiation. In addition, the relationship between RGHg and other parameters measured during the cruise will be discussed. Our results clearly show that RGHg deposition to the ocean must be an important Hg source, and a crucial part of the global Hg cycle. (1) Mason R.P., Fitzgerald W.F., and Morel F.M.M. (1994), The biogeochemical cycling of elemental mercury: Anthropogenic influences, Geochim. Cosmochim. Acta, 58: 3191-3198 (2) Shia R.L., Seigneur C., Pai P., Ko M., and Sze N.-D. (1999), Global simulation of atmospheric mercury concentrations and deposition fluxes, J. Geophy. Res., 104(D19), 23, 747-23, 760 (3) Mason, R.P., Lawson N.M., and Sheu G.-R. (2001), Mercury in the Atlantic Ocean: factors controlling air-sea exchange of mercury and its distribution in the upper water, Deep-Sea Res. II, 2829-2853 (4) Lamborg, C.H., Rolfus K.R., and Fitzgerald W.F. (1999), The atmospheric cycling and air-sea exchange of mercury species in the south and equatorial Atlantic Ocean, Deep-Sea Res. II, 957-977 (5) Lindberg S.E., Brooks S., Lin C.-J., Scott K. J., Landis M. S., Stevens R.K., Goodsite M., and Richter A. (2002), Dynamic oxidation of gaseous mercury in the arctic troposphere at polar sunrise, Environ. Sci. Technol., 1245-1256 (6) Bullock O.R. (2000), Modeling assessment of transport and deposition patterns of anthropogenic mercury air emissions in the United States and Canada, Sci Total Environ., 259(1-3), 145-157 (7) Xu X., Yang X., Miller d.R., Helble J.J., and Carley R.J. (2000), a regional scale modelling study of atmospheric transport and formation of mercury. II. Simulation results for the northeast United states, Atmos. Environ., 34: 4945-4955 (8) Sheu G.-R. (2001), Speciation and distribution of atmospheric mercury: Significance of reactive gaseous mercury in the global mercury cycle. PhD. thesis, University of Maryland, College park, pp. 170 (9) Guentzel J.L., Landing W.M., Gill G.A., and Pollman C.D. (2001), Processes influencing rainfall deposition of mercury in Florida, Environ. Sci. Technol., 35: 863-873

Major role of nitrite-oxidizing bacteria in dark ocean carbon fixation

NASA Astrophysics Data System (ADS)

Pachiadaki, Maria G.; Sintes, Eva; Bergauer, Kristin; Brown, Julia M.; Record, Nicholas R.; Swan, Brandon K.; Mathyer, Mary Elizabeth; Hallam, Steven J.; Lopez-Garcia, Purificacion; Takaki, Yoshihiro; Nunoura, Takuro; Woyke, Tanja; Herndl, Gerhard J.; Stepanauskas, Ramunas

2017-11-01

Carbon fixation by chemoautotrophic microorganisms in the dark ocean has a major impact on global carbon cycling and ecological relationships in the ocean’s interior, but the relevant taxa and energy sources remain enigmatic. We show evidence that nitrite-oxidizing bacteria affiliated with the Nitrospinae phylum are important in dark ocean chemoautotrophy. Single-cell genomics and community metagenomics revealed that Nitrospinae are the most abundant and globally distributed nitrite-oxidizing bacteria in the ocean. Metaproteomics and metatranscriptomics analyses suggest that nitrite oxidation is the main pathway of energy production in Nitrospinae. Microautoradiography, linked with catalyzed reporter deposition fluorescence in situ hybridization, indicated that Nitrospinae fix 15 to 45% of inorganic carbon in the mesopelagic western North Atlantic. Nitrite oxidation may have a greater impact on the carbon cycle than previously assumed.

Deep mantle cycling of oceanic crust: evidence from diamonds and their mineral inclusions.

PubMed

Walter, M J; Kohn, S C; Araujo, D; Bulanova, G P; Smith, C B; Gaillou, E; Wang, J; Steele, A; Shirey, S B

2011-10-07

A primary consequence of plate tectonics is that basaltic oceanic crust subducts with lithospheric slabs into the mantle. Seismological studies extend this process to the lower mantle, and geochemical observations indicate return of oceanic crust to the upper mantle in plumes. There has been no direct petrologic evidence, however, of the return of subducted oceanic crustal components from the lower mantle. We analyzed superdeep diamonds from Juina-5 kimberlite, Brazil, which host inclusions with compositions comprising the entire phase assemblage expected to crystallize from basalt under lower-mantle conditions. The inclusion mineralogies require exhumation from the lower to upper mantle. Because the diamond hosts have carbon isotope signatures consistent with surface-derived carbon, we conclude that the deep carbon cycle extends into the lower mantle.

Impact of hydrothermalism on the ocean iron cycle

PubMed Central

Resing, Joseph

2016-01-01

As the iron supplied from hydrothermalism is ultimately ventilated in the iron-limited Southern Ocean, it plays an important role in the ocean biological carbon pump. We deploy a set of focused sensitivity experiments with a state of the art global model of the ocean to examine the processes that regulate the lifetime of hydrothermal iron and the role of different ridge systems in governing the hydrothermal impact on the Southern Ocean biological carbon pump. Using GEOTRACES section data, we find that stabilization of hydrothermal iron is important in some, but not all regions. The impact on the Southern Ocean biological carbon pump is dominated by poorly explored southern ridge systems, highlighting the need for future exploration in this region. We find inter-basin differences in the isopycnal layer onto which hydrothermal Fe is supplied between the Atlantic and Pacific basins, which when combined with the inter-basin contrasts in oxidation kinetics suggests a muted influence of Atlantic ridges on the Southern Ocean biological carbon pump. Ultimately, we present a range of processes, operating at distinct scales, that must be better constrained to improve our understanding of how hydrothermalism affects the ocean cycling of iron and carbon. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’. PMID:29035256

Impact of hydrothermalism on the ocean iron cycle.

PubMed

Tagliabue, Alessandro; Resing, Joseph

2016-11-28

As the iron supplied from hydrothermalism is ultimately ventilated in the iron-limited Southern Ocean, it plays an important role in the ocean biological carbon pump. We deploy a set of focused sensitivity experiments with a state of the art global model of the ocean to examine the processes that regulate the lifetime of hydrothermal iron and the role of different ridge systems in governing the hydrothermal impact on the Southern Ocean biological carbon pump. Using GEOTRACES section data, we find that stabilization of hydrothermal iron is important in some, but not all regions. The impact on the Southern Ocean biological carbon pump is dominated by poorly explored southern ridge systems, highlighting the need for future exploration in this region. We find inter-basin differences in the isopycnal layer onto which hydrothermal Fe is supplied between the Atlantic and Pacific basins, which when combined with the inter-basin contrasts in oxidation kinetics suggests a muted influence of Atlantic ridges on the Southern Ocean biological carbon pump. Ultimately, we present a range of processes, operating at distinct scales, that must be better constrained to improve our understanding of how hydrothermalism affects the ocean cycling of iron and carbon.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

Acidification of subsurface coastal waters enhanced by eutrophication

EPA Science Inventory

Uptake of fossil-fuel carbon dioxide (CO2) from the atmosphere has acidified the surface ocean by ~0.1 pH units and driven down the carbonate saturation state. Ocean acidification is a threat to marine ecosystems and may alter key biogeochemical cycles. Coastal oceans have also b...

Tropical Pacific Climate, Carbon, and Ocean Biogeochemical Response to the Central American Seaway in a GFDL Earth System Model

NASA Astrophysics Data System (ADS)

Sentman, L. T.; Dunne, J. P.; Stouffer, R. J.; Krasting, J. P.; Wittenberg, A. T.; Toggweiler, J. R.; Broccoli, A. J.

2017-12-01

To explore the tropical Pacific climate, carbon, and ocean biogeochemical response to the shoaling and closure of the Central American Seaway during the Pliocene (5.3-2.6 Ma), we performed a suite of sensitivity experiments using the Geophysical Fluid Dynamics Laboratory Earth System Model, GFDL-ESM2G, varying only the seaway widths and sill depths. These novel ESM simulations include near-final closure of the seaway with a very narrow, 1º grid cell wide opening. Net mass transport through the seaway into the Caribbean is 20.5-23.1 Sv with a deep seaway, but only 14.1 Sv for the wide/shallow seaway because of the inter-basin bi-directional horizontal mass transport. Seaway transport originates from the Antarctic Circumpolar Current in the Pacific and rejoins it in the South Atlantic, reducing the Indonesian Throughflow and transporting heat and salt southward into the South Atlantic, in contrast to present-day and previous seaway simulations. Tropical Pacific mean climate and interannual variability is sensitive to the seaway shoaling, with the largest response to the wider/deeper seaway. In the tropical Pacific, the top 300-m warms 0.4-0.8°C, the equatorial east-west sea surface temperature gradient increases, the north-south sea surface temperature asymmetry at 110°W decreases, thermocline deepens 5-11 m, and the east-west thermocline gradient increases. In the Niño-3 region, ENSO amplitude increases, skewed toward more cold (La Niña) events, El Niño and La Niña develops earlier ( 3 months), the annual cycle weakens and the semi-annual and interannual cycles strengthen from increased symmetry of the north-south sea surface temperature gradient, and atmospheric global teleconnections strengthen with the seaway. The increase in global ocean overturning with the seaway results in a younger average ocean ideal age, reduced dissolved inorganic carbon inventory and marine net primary productivity, and altered inter-basin patterns of surface sediment carbonate sedimentation and preservation in the Caribbean and eastern equatorial Pacific, consistent with paleoclimate proxy data. The air-sea CO2 flux into the ocean decreases with the narrow seaway, thereby increasing atmospheric pCO2 concentrations by at least 236 ppm compared with present-day, with implications for warming during the Pliocene.

NASA Oceanic Processes Program, Fiscal Year 1981

NASA Technical Reports Server (NTRS)

1982-01-01

Summaries are included for Nimbus 7, Seasat, TIROS-N, Altimetry, Color Radiometry, in situ data collection systems, Synthetic Aperture Radar (SAR)/Open Ocean, SAR/Sea Ice, Scatterometry, National Oceanic Satellite System, Free Flying Imaging Radar Experiment, TIROS-N/Scatterometer and/or ocean color scanner, and Ocean Topography Experiment. Summaries of individual research projects sponsored by the Ocean Processes Program are given. Twelve investigations for which contracting services are provided by NOAA are included.

Decadal Air-Sea Interaction in the North Atlantic Based on Observations and Modeling Results

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa

1998-01-01

The decadal, 12-14 year, cycle observed in the North Atlantic SST and tide gauge data was examined using the NCEP/NCAR reanalyses, COADS data and an ocean model simulation. Besides this decadal mode, a shorter, subdecadal period of about 8 years exists in tide gauge data north of 40N, in the subpolar SST and in the winter North Atlantic Oscillation (NAO) index and in subpolar winter heat flux values. The decadal cycle is a well separated mode in a singular spectrum analysis (SSA) for a time series of SST EOF mode 1 with a center over the Gulf Stream extension. Tide gauge and SST data are consistent in that both show a significant subdecadal periodicity exclusively in the subpolar gyre, but in subtropics the 12-14 year period is the prominent, but nonstationary, decadal signal. The main finding of this study is that this 12-14 year cycle can be constructed based on the leading mode of the surface heat flux. This connection to the surface heat flux implicates the participation of the thermohaline circulation in the decadal cycle. During the cycle starting from the positive index phase of NAO, SST and oceanic heat content anomalies are created in subtropics due to local heat flux and intensification of the thermohaline circulation. The anomalies advect to the subpolar gyre where they are amplified by local heat flux and are part of the negative feedback of thermohaline circulation on itself. Consequently the oceanic thermohaline circulation slows down and the opposite cycle starts. The oscillatory nature would not be possible without the active atmospheric participation in the cycle, because it provides the unstable interaction through heat flux, without it, the oceanic mode would be damped. This analysis suggests that the two principal modes of heat flux variability, corresponding to patterns similar to North Atlantic Oscillation (NAO) and Western Atlantic (WA), are part of the same decadal cycle and an indirect measure of the north-south movement of the storm tracks.

Seasonal sea surface cooling in the equatorial Pacific cold tongue controlled by ocean mixing.

PubMed

Moum, James N; Perlin, Alexander; Nash, Jonathan D; McPhaden, Michael J

2013-08-01

Sea surface temperature (SST) is a critical control on the atmosphere, and numerical models of atmosphere-ocean circulation emphasize its accurate prediction. Yet many models demonstrate large, systematic biases in simulated SST in the equatorial 'cold tongues' (expansive regions of net heat uptake from the atmosphere) of the Atlantic and Pacific oceans, particularly with regard to a central but little-understood feature of tropical oceans: a strong seasonal cycle. The biases may be related to the inability of models to constrain turbulent mixing realistically, given that turbulent mixing, combined with seasonal variations in atmospheric heating, determines SST. In temperate oceans, the seasonal SST cycle is clearly related to varying solar heating; in the tropics, however, SSTs vary seasonally in the absence of similar variations in solar inputs. Turbulent mixing has long been a likely explanation, but firm, long-term observational evidence has been absent. Here we show the existence of a distinctive seasonal cycle of subsurface cooling via mixing in the equatorial Pacific cold tongue, using multi-year measurements of turbulence in the ocean. In boreal spring, SST rises by 2 kelvin when heating of the upper ocean by the atmosphere exceeds cooling by mixing from below. In boreal summer, SST decreases because cooling from below exceeds heating from above. When the effects of lateral advection are considered, the magnitude of summer cooling via mixing (4 kelvin per month) is equivalent to that required to counter the heating terms. These results provide quantitative assessment of how mixing varies on timescales longer than a few weeks, clearly showing its controlling influence on seasonal cooling of SST in a critical oceanic regime.

Ocean deoxygenation, the global phosphorus cycle and the possibility of human-caused large-scale ocean anoxia

NASA Astrophysics Data System (ADS)

Watson, Andrew J.; Lenton, Timothy M.; Mills, Benjamin J. W.

2017-08-01

The major biogeochemical cycles that keep the present-day Earth habitable are linked by a network of feedbacks, which has led to a broadly stable chemical composition of the oceans and atmosphere over hundreds of millions of years. This includes the processes that control both the atmospheric and oceanic concentrations of oxygen. However, one notable exception to the generally well-behaved dynamics of this system is the propensity for episodes of ocean anoxia to occur and to persist for 105-106 years, these ocean anoxic events (OAEs) being particularly associated with warm `greenhouse' climates. A powerful mechanism responsible for past OAEs was an increase in phosphorus supply to the oceans, leading to higher ocean productivity and oxygen demand in subsurface water. This can be amplified by positive feedbacks on the nutrient content of the ocean, with low oxygen promoting further release of phosphorus from ocean sediments, leading to a potentially self-sustaining condition of deoxygenation. We use a simple model for phosphorus in the ocean to explore this feedback, and to evaluate the potential for humans to bring on global-scale anoxia by enhancing P supply to the oceans. While this is not an immediate global change concern, it is a future possibility on millennial and longer time scales, when considering both phosphate rock mining and increased chemical weathering due to climate change. Ocean deoxygenation, once begun, may be self-sustaining and eventually could result in long-lasting and unpleasant consequences for the Earth's biosphere. This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'.

The growth of finfish in global open-ocean aquaculture under climate change.

PubMed

Klinger, Dane H; Levin, Simon A; Watson, James R

2017-10-11

Aquaculture production is projected to expand from land-based operations to the open ocean as demand for seafood grows and competition increases for inputs to land-based aquaculture, such as freshwater and suitable land. In contrast to land-based production, open-ocean aquaculture is constrained by oceanographic factors, such as current speeds and seawater temperature, which are dynamic in time and space, and cannot easily be controlled. As such, the potential for offshore aquaculture to increase seafood production is tied to the physical state of the oceans. We employ a novel spatial model to estimate the potential of open-ocean finfish aquaculture globally, given physical, biological and technological constraints. Finfish growth potential for three common aquaculture species representing different thermal guilds-Atlantic salmon ( Salmo salar ), gilthead seabream ( Sparus aurata ) and cobia ( Rachycentron canadum )-is compared across species and regions and with climate change, based on outputs of a high-resolution global climate model. Globally, there are ample areas that are physically suitable for fish growth and potential expansion of the nascent aquaculture industry. The effects of climate change are heterogeneous across species and regions, but areas with existing aquaculture industries are likely to see increases in growth rates. In areas where climate change results in reduced growth rates, adaptation measures, such as selective breeding, can probably offset potential production losses. © 2017 The Author(s).

The Neoarchaean surficial sulphur cycle: An alternative hypothesis based on analogies with 20th-century atmospheric lead.

PubMed

Gallagher, M; Whitehouse, M J; Kamber, B S

2017-05-01

We revisit the S-isotope systematics of sedimentary pyrite in a shaly limestone from the ca. 2.52 Ga Gamohaan Formation, Upper Campbellrand Subgroup, Transvaal, South Africa. The analysed rock is interpreted to have been deposited in a water depth of ca. 50-100 m, in a restricted sub-basin on a drowning platform. A previous study discovered that the pyrites define a nonzero intercept δ 34 S V - CDT -Δ 33 S data array. The present study carried out further quadruple S-isotope analyses of pyrite, confirming and expanding the linear δ 34 S V - CDT -Δ 33 S array with an δ 34 S zero intercept at ∆ 33 S ca. +5. This was previously interpreted to indicate mixing of unrelated S-sources in the sediment environment, involving a combination of recycled sulphur from sulphides that had originally formed by sulphate-reducing bacteria, along with elemental sulphur. Here, we advance an alternative explanation based on the recognition that the Archaean seawater sulphate concentration was likely very low, implying that the Archaean ocean could have been poorly mixed with respect to sulphur. Thus, modern oceanic sulphur systematics provide limited insight into the Archaean sulphur cycle. Instead, we propose that the 20th-century atmospheric lead event may be a useful analogue. Similar to industrial lead, the main oceanic input of Archaean sulphur was through atmospheric raindown, with individual giant point sources capable of temporally dominating atmospheric input. Local atmospheric S-isotope signals, of no global significance, could thus have been transmitted into the localised sediment record. Thus, the nonzero intercept δ 34 S V - CDT -Δ 33 S data array may alternatively represent a very localised S-isotope signature in the Neoarchaean surface environment. Fallout from local volcanic eruptions could imprint recycled MIF-S signals into pyrite of restricted depositional environments, thereby avoiding attenuation of the signal in the subdued, averaged global open ocean sulphur pool. Thus, the superposition of extreme local S-isotope signals offers an alternative explanation for the large Neoarchaean MIF-S excursions and asymmetry of the Δ 33 S rock record. © 2017 John Wiley & Sons Ltd.

Impact of an intense water column mixing (0-1500 m) on prokaryotic diversity and activities during an open-ocean convection event in the NW Mediterranean Sea.

PubMed

Severin, Tatiana; Sauret, Caroline; Boutrif, Mehdi; Duhaut, Thomas; Kessouri, Fayçal; Oriol, Louise; Caparros, Jocelyne; Pujo-Pay, Mireille; Durrieu de Madron, Xavier; Garel, Marc; Tamburini, Christian; Conan, Pascal; Ghiglione, Jean-François

2016-12-01

Open-ocean convection is a fundamental process for thermohaline circulation and biogeochemical cycles that causes spectacular mixing of the water column. Here, we tested how much the depth-stratified prokaryotic communities were influenced by such an event, and also by the following re-stratification. The deep convection event (0-1500 m) that occurred in winter 2010-2011 in the NW Mediterranean Sea resulted in a homogenization of the prokaryotic communities over the entire convective cell, resulting in the predominance of typical surface Bacteria, such as Oceanospirillale and Flavobacteriales. Statistical analysis together with numerical simulation of vertical homogenization evidenced that physical turbulence only was not enough to explain the new distribution of the communities, but acted in synergy with other parameters such as exported particulate and dissolved organic matters. The convection also stimulated prokaryotic abundance (+21%) and heterotrophic production (+43%) over the 0-1500 m convective cell, and resulted in a decline of cell-specific extracellular enzymatic activities (-67%), thus suggesting an intensification of the labile organic matter turnover during the event. The rapid re-stratification of the prokaryotic diversity and activities in the intermediate layer 5 days after the intense mixing indicated a marked resilience of the communities, apart from the residual deep mixed water patch. © 2016 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

Pteropods are Undervalued Contributors to Aragonite Flux in Tropical Gyres

NASA Astrophysics Data System (ADS)

Pebody, C. A.; Lampitt, R. S.

2016-02-01

Pteropods are a large component of the animals routinely caught in sediment traps at 3000m at the NOG observatory in the North Atlantic Oligotrophic Gyre and at the SOG observatory in the South Atlantic Oligotrophic Gyre. Sediment traps have been used to collect downward settling material at NOG and SOG since 2008. Pteropods have been identified and removed from the samples during processing in line with best practice. Some of these animals maybe opportunistic swimmers, but some are most definitely broken and should be considered as a component of the downward particle flux. Samples from both locations demonstrate a sustained and sometimes seasonal flux of pteropods to the deep ocean interior. In gyre regions with low levels of particle flux compared to temperate regions, the additional mostly inorganic material supplied in the form of pteropod shells represents a large proportional increase. Our data set from both northern and southern Atlantic gyres demonstrates due consideration should be given to the importance of pteropod flux and the contribution this makes to the biological carbon pump. These observatories at 23°N 41°W and 18°S 25°W, are part of the FixO3 open observatory network and are supported by NOC and NERC. Analysis of the first three years of each observatory are now yielding new insight on these large and poorly sampled areas of the open ocean. Key words: pteropods; aragonite; sediment traps; NOG SOG; FixO3; biological carbon pump; biogeochemical cycles; Tropical Atlantic Gyres.

Major role of microbes in carbon fluxes during Austral winter in the Southern Drake Passage.

PubMed

Manganelli, Maura; Malfatti, Francesca; Samo, Ty J; Mitchell, B Greg; Wang, Haili; Azam, Farooq

2009-09-14

Carbon cycling in Southern Ocean is a major issue in climate change, hence the need to understand the role of biota in the regulation of carbon fixation and cycling. Southern Ocean is a heterogeneous system, characterized by a strong seasonality, due to long dark winter. Yet, currently little is known about biogeochemical dynamics during this season, particularly in the deeper part of the ocean. We studied bacterial communities and processes in summer and winter cruises in the southern Drake Passage. Here we show that in winter, when the primary production is greatly reduced, Bacteria and Archaea become the major producers of biogenic particles, at the expense of dissolved organic carbon drawdown. Heterotrophic production and chemoautotrophic CO(2) fixation rates were substantial, also in deep water, and bacterial populations were controlled by protists and viruses. A dynamic food web is also consistent with the observed temporal and spatial variations in archaeal and bacterial communities that might exploit various niches. Thus, Southern Ocean microbial loop may substantially maintain a wintertime food web and system respiration at the expense of summer produced DOC as well as regenerate nutrients and iron. Our findings have important implications for Southern Ocean ecosystem functioning and carbon cycle and its manipulation by iron enrichment to achieve net sequestration of atmospheric CO(2).

Development and Utilization of Regional Oceanic Modeling System (ROMS). Delicacy, Imprecision, and Uncertainty of Oceanic Simulations: An Investigation with the Regional Oceanic Modeling System (ROMS). Mixing in the Ocean Surface Layer Using the Regional Oceanic Modeling System (ROMS).

DTIC Science & Technology

2011-09-30

community use for ROMS is biogeochemisty: chemical cycles, water quality, blooms , micro-nutrients, larval dispersal, biome transitions, and coupling to...J.C. McWilliams, X. Capet, and J. Kurian, 2010: Heat balance and eddies in the Peru- Chile Current System. Climate Dynamics, 37, in press. doi10.1007

Covariation of deep Southern Ocean oxygenation and atmospheric CO2 through the last ice age.

PubMed

Jaccard, Samuel L; Galbraith, Eric D; Martínez-García, Alfredo; Anderson, Robert F

2016-02-11

No single mechanism can account for the full amplitude of past atmospheric carbon dioxide (CO2) concentration variability over glacial-interglacial cycles. A build-up of carbon in the deep ocean has been shown to have occurred during the Last Glacial Maximum. However, the mechanisms responsible for the release of the deeply sequestered carbon to the atmosphere at deglaciation, and the relative importance of deep ocean sequestration in regulating millennial-timescale variations in atmospheric CO2 concentration before the Last Glacial Maximum, have remained unclear. Here we present sedimentary redox-sensitive trace-metal records from the Antarctic Zone of the Southern Ocean that provide a reconstruction of transient changes in deep ocean oxygenation and, by inference, respired carbon storage throughout the last glacial cycle. Our data suggest that respired carbon was removed from the abyssal Southern Ocean during the Northern Hemisphere cold phases of the deglaciation, when atmospheric CO2 concentration increased rapidly, reflecting--at least in part--a combination of dwindling iron fertilization by dust and enhanced deep ocean ventilation. Furthermore, our records show that the observed covariation between atmospheric CO2 concentration and abyssal Southern Ocean oxygenation was maintained throughout most of the past 80,000 years. This suggests that on millennial timescales deep ocean circulation and iron fertilization in the Southern Ocean played a consistent role in modifying atmospheric CO2 concentration.

Water cycling between ocean and mantle: Super-earths need not be waterworlds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowan, Nicolas B.; Abbot, Dorian S., E-mail: n-cowan@northwestern.edu

2014-01-20

Large terrestrial planets are expected to have muted topography and deep oceans, implying that most super-Earths should be entirely covered in water, so-called waterworlds. This is important because waterworlds lack a silicate weathering thermostat so their climate is predicted to be less stable than that of planets with exposed continents. In other words, the continuously habitable zone for waterworlds is much narrower than for Earth-like planets. A planet's water is partitioned, however, between a surface reservoir, the ocean, and an interior reservoir, the mantle. Plate tectonics transports water between these reservoirs on geological timescales. Degassing of melt at mid-ocean ridgesmore » and serpentinization of oceanic crust depend negatively and positively on seafloor pressure, respectively, providing a stabilizing feedback on long-term ocean volume. Motivated by Earth's approximately steady-state deep water cycle, we develop a two-box model of the hydrosphere and derive steady-state solutions to the water partitioning on terrestrial planets. Critically, hydrostatic seafloor pressure is proportional to surface gravity, so super-Earths with a deep water cycle will tend to store more water in the mantle. We conclude that a tectonically active terrestrial planet of any mass can maintain exposed continents if its water mass fraction is less than ∼0.2%, dramatically increasing the odds that super-Earths are habitable. The greatest source of uncertainty in our study is Earth's current mantle water inventory: the greater its value, the more robust planets are to inundation. Lastly, we discuss how future missions can test our hypothesis by mapping the oceans and continents of massive terrestrial planets.« less

Global and regional axial ocean angular momentum signals and length-of-day variations (1985-1996)

NASA Astrophysics Data System (ADS)

Ponte, Rui M.; Stammer, Detlef

2000-07-01

Changes in ocean angular momentum M about the polar axis are related to fluctuations in zonal currents (relative component Mr) and latitudinal shifts in mass (planetary component MΩ). Output from a 1° ocean model is used to calculate global Mr, MΩ, and M time series at 5 day intervals for the period January 1985 to April 1996. The annual cycle in Mr, MΩ, and M is larger than the semiannual cycle, and MΩ amplitudes are nearly twice those of Mr. Year-to-year modulation of the seasonal cycle is present, but interannual variability is weak. The spectrum of M is red (background slope between ω-1 and ω-2) at subseasonal periods, implying a white or blue spectrum for the external torque on the ocean. Comparisons with previous studies indicate the importance of direct atmospheric forcing in inducing subseasonal M signals, relative to instabilities and other internal sources of rapid oceanic signals. Regional angular momentum estimates show that seasonal variability tends to be larger at low latitudes, but many local maxima exist because of the spatial structure of zonal current and mass variability. At seasonal timescales, latitudes ~20°S-10°N contribute substantial variability to MΩ, while signals in Mr can be traced to Antarctic Circumpolar Current transports and associated circulation. Variability in M is found to be small when compared with similar time series for the atmosphere and the solid Earth, but ocean signals are significantly coherent with atmosphere-solid Earth residuals, implying a measurable oceanic impact on length-of-day variations.

Evaluation of NorESM-OC (versions 1 and 1.2), the ocean carbon-cycle stand-alone configuration of the Norwegian Earth System Model (NorESM1)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwinger, Jorg; Goris, Nadine; Tjiputra, Jerry F.

Idealised and hindcast simulations performed with the stand-alone ocean carbon-cycle configuration of the Norwegian Earth System Model (NorESM-OC) are described and evaluated. We present simulation results of three different model configurations (two different model versions at different grid resolutions) using two different atmospheric forcing data sets. Model version NorESM-OC1 corresponds to the version that is included in the NorESM-ME1 fully coupled model, which participated in CMIP5. The main update between NorESM-OC1 and NorESM-OC1.2 is the addition of two new options for the treatment of sinking particles. We find that using a constant sinking speed, which has been the standard in NorESM'smore » ocean carbon cycle module HAMOCC (HAMburg Ocean Carbon Cycle model), does not transport enough particulate organic carbon (POC) into the deep ocean below approximately 2000 m depth. The two newly implemented parameterisations, a particle aggregation scheme with prognostic sinking speed, and a simpler scheme that uses a linear increase in the sinking speed with depth, provide better agreement with observed POC fluxes. Additionally, reduced deep ocean biases of oxygen and remineralised phosphate indicate a better performance of the new parameterisations. For model version 1.2, a re-tuning of the ecosystem parameterisation has been performed, which (i) reduces previously too high primary production at high latitudes, (ii) consequently improves model results for surface nutrients, and (iii) reduces alkalinity and dissolved inorganic carbon biases at low latitudes. We use hindcast simulations with prescribed observed and constant (pre-industrial) atmospheric CO 2 concentrations to derive the past and contemporary ocean carbon sink. As a result, for the period 1990–1999 we find an average ocean carbon uptake ranging from 2.01 to 2.58 Pg C yr -1 depending on model version, grid resolution, and atmospheric forcing data set.« less

Evaluation of NorESM-OC (versions 1 and 1.2), the ocean carbon-cycle stand-alone configuration of the Norwegian Earth System Model (NorESM1)

DOE PAGES

Schwinger, Jorg; Goris, Nadine; Tjiputra, Jerry F.; ...

2016-08-02

Idealised and hindcast simulations performed with the stand-alone ocean carbon-cycle configuration of the Norwegian Earth System Model (NorESM-OC) are described and evaluated. We present simulation results of three different model configurations (two different model versions at different grid resolutions) using two different atmospheric forcing data sets. Model version NorESM-OC1 corresponds to the version that is included in the NorESM-ME1 fully coupled model, which participated in CMIP5. The main update between NorESM-OC1 and NorESM-OC1.2 is the addition of two new options for the treatment of sinking particles. We find that using a constant sinking speed, which has been the standard in NorESM'smore » ocean carbon cycle module HAMOCC (HAMburg Ocean Carbon Cycle model), does not transport enough particulate organic carbon (POC) into the deep ocean below approximately 2000 m depth. The two newly implemented parameterisations, a particle aggregation scheme with prognostic sinking speed, and a simpler scheme that uses a linear increase in the sinking speed with depth, provide better agreement with observed POC fluxes. Additionally, reduced deep ocean biases of oxygen and remineralised phosphate indicate a better performance of the new parameterisations. For model version 1.2, a re-tuning of the ecosystem parameterisation has been performed, which (i) reduces previously too high primary production at high latitudes, (ii) consequently improves model results for surface nutrients, and (iii) reduces alkalinity and dissolved inorganic carbon biases at low latitudes. We use hindcast simulations with prescribed observed and constant (pre-industrial) atmospheric CO 2 concentrations to derive the past and contemporary ocean carbon sink. As a result, for the period 1990–1999 we find an average ocean carbon uptake ranging from 2.01 to 2.58 Pg C yr -1 depending on model version, grid resolution, and atmospheric forcing data set.« less

Modelling sea ice formation in the Terra Nova Bay polynya

NASA Astrophysics Data System (ADS)

Sansiviero, M.; Morales Maqueda, M. Á.; Fusco, G.; Aulicino, G.; Flocco, D.; Budillon, G.

2017-02-01

Antarctic sea ice is constantly exported from the shore by strong near surface winds that open leads and large polynyas in the pack ice. The latter, known as wind-driven polynyas, are responsible for significant water mass modification due to the high salt flux into the ocean associated with enhanced ice growth. In this article, we focus on the wind-driven Terra Nova Bay (TNB) polynya, in the western Ross Sea. Brine rejected during sea ice formation processes that occur in the TNB polynya densifies the water column leading to the formation of the most characteristic water mass of the Ross Sea, the High Salinity Shelf Water (HSSW). This water mass, in turn, takes part in the formation of Antarctic Bottom Water (AABW), the densest water mass of the world ocean, which plays a major role in the global meridional overturning circulation, thus affecting the global climate system. A simple coupled sea ice-ocean model has been developed to simulate the seasonal cycle of sea ice formation and export within a polynya. The sea ice model accounts for both thermal and mechanical ice processes. The oceanic circulation is described by a one-and-a-half layer, reduced gravity model. The domain resolution is 1 km × 1 km, which is sufficient to represent the salient features of the coastline geometry, notably the Drygalski Ice Tongue. The model is forced by a combination of Era Interim reanalysis and in-situ data from automatic weather stations, and also by a climatological oceanic dataset developed from in situ hydrographic observations. The sensitivity of the polynya to the atmospheric forcing is well reproduced by the model when atmospheric in situ measurements are combined with reanalysis data. Merging the two datasets allows us to capture in detail the strength and the spatial distribution of the katabatic winds that often drive the opening of the polynya. The model resolves fairly accurately the sea ice drift and sea ice production rates in the TNB polynya, leading to realistic polynya extent estimates. The model-derived polynya extent has been validated by comparing the modelled sea ice concentration against MODIS high resolution satellite images, confirming that the model is able to reproduce reasonably well the TNB polynya evolution in terms of both shape and extent.

Particle flux in deep seas: regional characteristics and temporal variability

NASA Astrophysics Data System (ADS)

Lampitt, R. S.; Antia, A. N.

1997-08-01

Particle flux data have been collated from the literature representing most areas of the open ocean to determine regional trends in deep water flux and its seasonal variability. Organic carbon flux data normalised to a depth of 2000 m exhibits a range of an order of magnitude in areas outside the polar domains (0.38 to 4.2 g/m2/y). In polar regions the range is wider (0.01-5.9 g/m2/y). Latitudinal trends are not apparent for most components of the flux although calcite flux exhibits a poleward decrease. Limited data from polar regions show fluxes of opaline silica not significantly higher than elsewhere. The variability of flux over annual cycles was calculated and expressed as a Flux Stability Index (FSI) and the relationship between this and vertical flux of material examined. Somewhat surprisingly there is no significant relationship between FSI and fluxes of dry mass, organic carbon, inorganic carbon or opaline silica. At each site, net annual primary production was determined using published satellite derived estimates. There is a negative but weak relationship between FSI and the proportion of primary production exported to 2000 m (e2000 ratio). The most variable of the non-polar environments export to 2000 m about twice as much of the primary production as the most stable ones. Polar environments have very low e2000 ratios with no apparent relationship to FSI. At primary production levels below 200 g C/m2/y there is a positive correlation between production and organic carbon flux at 2000 m but above this level, flux remains constant at about 3.5g C/m2/y. A curve derived to describe this relationship was applied to estimates of annual primary production in each of 34 of the open ocean biogeochemical provinces proposed by Longhurst et al. (1995). Globally, open ocean flux of organic carbon at 2000 m is 0.34 Gt/yr which is 1% of the total net primary production in these regions. This flux is nearly equally divided between the Atlantic, Pacific and Southern Oceans. The Indian and Arctic oceans between them only contribute 5% to the total. The eight planktonic climatological categories proposed by Longhurst (1995) provide a most useful means of examining the data on flux and its variability. A characteristic level of FSI was found in each category with highest levels in the tropics and lowest levels in the Antarctic. There is also a characteristic level of export ratio in each category with the highest in monsoonal environments (1.7%) and the lowest in Antarctica (0.1%).

From Rivers to Oceans and Back: Linking Models to Encompass the Full Salmon Life Cycle

NASA Astrophysics Data System (ADS)

Danner, E.; Hendrix, N.; Martin, B.; Lindley, S. T.

2016-02-01

Pacific salmon are a promising study subject for investigating the linkages between freshwater and coastal ocean ecosystems. Salmon use a wide range of habitats throughout their life cycle as they move with water from mountain streams, mainstem rivers, estuaries, bays, and coastal oceans, with adult fish swimming back through the same migration route they took as juveniles. Conditions in one habitat can have growth and survival consequences that manifest in the following habitat, so is key that full life cycle models are used to further our understanding salmon population dynamics. Given the wide range of habitats and potential stressors, this approach requires the coordination of a multidisciplinary suite of physical and biological models, including climate, hydrologic, hydraulic, food web, circulation, bioenergetic, and ecosystem models. Here we present current approaches to linking physical and biological models that capture the foundational drivers for salmon in complex and dynamic systems.

Open Vessel Data Management (OpenVDM), Open-source Software to Assist Vessel Operators with the Task of Ship-wide Data Management.

NASA Astrophysics Data System (ADS)

Pinner, J. W., IV

2016-02-01

Data from shipboard oceanographic sensors are collected in various ASCii, binary, open and proprietary formats. Acquiring all of these formats using single, monolithic data acquisition system (DAS) can be cumbersome, complex and difficult to adapt for the ever changing suite of emerging oceanographic sensors. Another approach to the at-sea data acquisition challenge is to utilize multiple DAS software packages and corral the resulting data files with a ship-wide data management system. The Open Vessel Data Management project (OpenVDM) implements this second approach to ship-wide data management and over the last three years has successfully demonstrated it's ability to deliver a consistent cruise data package to scientists while reducing the workload placed on marine technicians. In addition to meeting the at-sea and post-cruise needs of scientists OpenVDM is helping vessel operators better adhere to the recommendations and best practices set forth by 3rd party data management and data quality groups such as R2R and SAMOS. OpenVDM also includes tools for supporting telepresence-enabled ocean research/exploration such as bandwidth-efficient ship-to-shore data transfers, shore-side data access, data visualization and near-real-time data quality tests and data statistics. OpenVDM is currently operating aboard three vessels. The R/V Endeavor, operated by the University of Rhode Island, is a regional-class UNOLS research vessel operating under the traditional NFS, P.I. driven model. The E/V Nautilus, operated by the Ocean Exploration Trust specializes in ROV-based, telepresence-enabled oceanographic research. The R/V Falkor operated by the Schmidt Ocean Institute is an ocean research platform focusing on cutting-edge technology development. These three vessels all have different missions, sensor suites and operating models yet all are able to leverage OpenVDM for managing their unique datasets and delivering a more consistent cruise data package to scientists and data archives.

Food webs of two intermittently open estuaries receiving 15N-enriched sewage effluent

NASA Astrophysics Data System (ADS)

Hadwen, Wade L.; Arthington, Angela H.

2007-01-01

Carbon and nitrogen stable isotope signatures were used to assess the response of food webs to sewage effluent discharged into two small intermittently open estuaries in northern New South Wales, Australia. One of these systems, Tallows Creek, has a history of direct sewage inputs, whilst the other, Belongil Creek, receives wastewater via an extensive wetland treatment system. The food webs of both systems were driven by algal sources of carbon, reflecting high autotrophic productivity in response to the nutrients entering the system from sewage effluent. All aquatic biota collected from Tallows Creek had significantly enriched δ15N signatures relative to their conspecifics from Belongil Creek, indicating that sewage nitrogen had been assimilated and transferred throughout the Tallows Creek food web. These δ15N values were higher than those reported from studies in permanently open estuaries receiving sewage effluent. We suggest that these enriched signatures and the transfer of nitrogen throughout the entire food web reflect differences in hydrology and associated nitrogen cycling processes between permanently open and intermittently open estuaries. Although all organisms in Tallows Creek were generally 15N-enriched, isotopically light (less 15N-enriched) individuals of estuary perchlet ( Ambassis marianus) and sea mullet ( Mugil cephalus) were also collected. These individuals were most likely recent immigrants into Tallows Creek, as this system had only recently been opened to the ocean. This isotopic discrimination between resident (enriched) and immigrant (significantly less enriched) individuals can provide information on fish movement patterns and the role of heavily polluted intermittently open estuaries in supporting commercially and recreationally valuable estuarine species.

Variable C : N : P stoichiometry of dissolved organic matter cycling in the Community Earth System Model

DOE PAGES

Letscher, R. T.; Moore, J. K.; Teng, Y. -C.; ...

2014-06-16

Dissolved organic matter (DOM) plays an important role in the ocean's biological carbon pump by providing an advective/mixing pathway for ~ 20% of export production. DOM is known to have a stoichiometry depleted in nitrogen (N) and phosphorus (P) compared to the particulate organic matter pool, a~fact that is often omitted from biogeochemical-ocean general circulation models. However the variable C : N : P stoichiometry of DOM becomes important when quantifying carbon export from the upper ocean and linking the nutrient cycles of N and P with that of carbon. Here we utilize recent advances in DOM observational data coveragemore » and offline tracer-modeling techniques to objectively constrain the variable production and remineralization rates of the DOM C / N / P pools in a simple biogeochemical-ocean model of DOM cycling. The optimized DOM cycling parameters are then incorporated within the Biogeochemical Elemental Cycling (BEC) component of the Community Earth System Model and validated against the compilation of marine DOM observations. The optimized BEC simulation including variable DOM C : N : P cycling was found to better reproduce the observed DOM spatial gradients than simulations that used the canonical Redfield ratio. Global annual average export of dissolved organic C, N, and P below 100 m was found to be 2.28 Pg C yr -1 (143 Tmol C yr -1), 16.4 Tmol N yr -1, and 1 Tmol P yr -1, respectively with an average export C : N : P stoichiometry of 225 : 19 : 1 for the semilabile (degradable) DOM pool. DOC export contributed ~ 25% of the combined organic C export to depths greater than 100 m.« less

Variable C : N : P stoichiometry of dissolved organic matter cycling in the Community Earth System Model

DOE PAGES

Letscher, R. T.; Moore, J. K.; Teng, Y. -C.; ...

2015-01-12

Dissolved organic matter (DOM) plays an important role in the ocean's biological carbon pump by providing an advective/mixing pathway for ~ 20% of export production. DOM is known to have a stoichiometry depleted in nitrogen (N) and phosphorus (P) compared to the particulate organic matter pool, a fact that is often omitted from biogeochemical ocean general circulation models. However the variable C : N : P stoichiometry of DOM becomes important when quantifying carbon export from the upper ocean and linking the nutrient cycles of N and P with that of carbon. Here we utilize recent advances in DOM observationalmore » data coverage and offline tracer-modeling techniques to objectively constrain the variable production and remineralization rates of the DOM C : N : P pools in a simple biogeochemical-ocean model of DOM cycling. The optimized DOM cycling parameters are then incorporated within the Biogeochemical Elemental Cycling (BEC) component of the Community Earth System Model (CESM) and validated against the compilation of marine DOM observations. The optimized BEC simulation including variable DOM C : N : P cycling was found to better reproduce the observed DOM spatial gradients than simulations that used the canonical Redfield ratio. Global annual average export of dissolved organic C, N, and P below 100 m was found to be 2.28 Pg C yr -1 (143 Tmol C yr -1, 16.4 Tmol N yr -1, and 1 Tmol P yr -1, respectively, with an average export C : N : P stoichiometry of 225 : 19 : 1 for the semilabile (degradable) DOM pool. Dissolved organic carbon (DOC) export contributed ~ 25% of the combined organic C export to depths greater than 100 m.« less

Phase locking of convectively coupled equatorial atmospheric Kelvin waves over Indian Ocean basin

NASA Astrophysics Data System (ADS)

Baranowski, Dariusz; Flatau, Maria; Flatau, Piotr; Matthews, Adrian

2015-04-01

The properties of convectively coupled Kelvin waves in the Indian Ocean and their propagation over the Maritime Continent are studied. It is shown that Kelvin waves are longitude - diurnal cycle phase locked over the Maritime Continent, Africa and the Indian Ocean. Thus, it is shown that they tend to propagate over definite areas during specific times of the day. Over the Maritime Continent, longitude-diurnal cycle phase locking is such that it agrees with mean, local diurnal cycle of convection. The strength of the longitude-diurnal cycle phase locking differs between 'non-blocked' Kelvin waves, which make successful transition over the Maritime Continent, and 'blocked' waves that terminated within it. It is shown that a specific combination of Kelvin wave phase speed and time of the day at which a wave approaches the Maritime Continent influence the chance of successful transition into the Western Pacific. Kelvin waves that maintain phase speed of 10 to 11 degrees per day over the central-eastern Indian Ocean and arrive at 90E between 9UTC and 18UTC have the highest chance of being 'non-blocked' by the Maritime Continent. The distance between the islands of Sumatra and Borneo agrees with the distance travelled by an average convectively coupled Kelvin wave in one day. This suggests that the Maritime Continent may act as a 'filter' for Kelvin waves favoring successful propagation of those waves for which propagation is in phase with the local diurnal cycle of precipitation. The AmPm index, a simple measure of local diurnal cycle for propagating disturbances, is introduced and shown to be useful metric depicting key characteristics of the convection associated with propagating Kelvin waves.

The Diurnal Cycle over the Maritime Continent and its Interaction with the MJO

NASA Astrophysics Data System (ADS)

Matthews, A. J.; Peatman, S.; Baranowski, D. B.; Stevens, D. P.; Heywood, K. J.; Flatau, P. J.; Schmidtko, S.

2014-12-01

The complex land-sea distribution and topography of the maritime continent acts to disrupt or even completely block the eastward propagation of the Madden-Julian Oscillation (MJO) from the Indian Ocean to the western Pacific. This leads to changes in tropical latent heat release and subsequent impacts on global circulation. Convection over the maritime continent is dominated by the diurnal cycle. Where the mean diurnal cycle is strong (over the islands and surrounding seas), 80% of the MJO precipitation signal in the maritime continent is accounted for by changes in the amplitude of the diurnal cycle. The canonical view of the MJO as the smooth eastward propagation of a large-scale precipitation envelope also breaks down over the islands of the Maritime Continent. Instead, a vanguard of precipitation jumps ahead of the main body by approximately 6 days or 2000 km. Hence, there can be enhanced precipitation over Sumatra, Borneo or New Guinea when the large-scale MJO envelope over the surrounding ocean is one of suppressed precipitation. This behaviour is discussed in terms of an interaction between the diurnal cycle and the MJO circulation. The diurnal cycle is also strong in the ocean. Seaglider measurements taken during the CINDY/DYNAMO campaign show the existence of a diurnal warm layer in the upper few metres of the ocean. This has a significant effect on the surface fluxes, of an order of Watts per square metre. The diurnal warm layer is favoured during the inactive phase of the MJO and may act to help precondition the atmosphere to convection. The activities of the MJO Task Force and Subseasonal to Seasonal Prediction project will be discussed in this context.

Millennial-scale variability in the local radiocarbon reservoir age of south Florida during the Holocene

USGS Publications Warehouse

Toth, Lauren T.; Cheng, Hai; Edwards, R. Lawrence; Ashe, Erica; Richey, Julie N.

2017-01-01

A growing body of research suggests that the marine environments of south Florida provide a critical link between the tropical and high-latitude Atlantic. Changes in the characteristics of water masses off south Florida may therefore have important implications for our understanding of climatic and oceanographic variability over a broad spatial scale; however, the sources of variability within this oceanic corridor remain poorly understood. Measurements of ΔR, the local offset of the radiocarbon reservoir age, from shallow-water marine environments can serve as a powerful tracer of water-mass sources that can be used to reconstruct variability in local-to regional-scale oceanography and hydrology. We combined radiocarbon and U-series measurements of Holocene-aged corals from the shallow-water environments of the Florida Keys reef tract (FKRT) with robust statistical modeling to quantify the millennial-scale variability in ΔR at locations with (“nearshore”) and without (“open ocean”) substantial terrestrial influence. Our reconstructions demonstrate that there was significant spatial and temporal variability in ΔR on the FKRT during the Holocene. Whereas ΔR was similar throughout the region after ∼4000 years ago, nearshore ΔR was significantly higher than in the open ocean during the middle Holocene. We suggest that the elevated nearshore ΔR from ∼8000 to 5000 years ago was most likely the result of greater groundwater influence associated with lower sea level at this time. In the open ocean, which would have been isolated from the influence of groundwater, ΔR was lowest ∼7000 years ago, and was highest ∼3000 years ago. We evaluated our open-ocean model of ΔR variability against records of local-to regional-scale oceanography and conclude that local upwelling was not a significant driver of open-ocean radiocarbon variability in this region. Instead, the millennial-scale trends in open-ocean ΔR were more likely a result of broader-scale changes in western Atlantic circulation associated with an increase in the supply of equatorial South Atlantic water to the Caribbean and shifts in the character of South Atlantic waters resulting from variation in the intensity of upwelling off the southwest coast of Africa. Because accurate estimates of ΔR are critical to precise calibrations of radiocarbon dates from marine samples, we also developed models of nearshore and open-ocean ΔR versus conventional 14C ages that can be used for regional radiocarbon calibrations for the Holocene. Our study provides new insights into the patterns and drivers of oceanographic and hydrologic variability in the Straits of Florida and highlights the value of the paleoceanographic records from south Florida to our understanding of Holocene changes in climate and ocean circulation throughout the Atlantic.

The effect of surface irradiance on the absorption spectrum of chromophoric dissolved organic matter in the global ocean

NASA Astrophysics Data System (ADS)

Swan, Chantal M.; Nelson, Norman B.; Siegel, David A.; Kostadinov, Tihomir S.

2012-05-01

The cycling pathways of chromophoric dissolved organic matter (CDOM) within marine systems must be constrained to better assess the impact of CDOM on surface ocean photochemistry and remote sensing of ocean color. Photobleaching, the loss of absorption by CDOM due to light exposure, is the primary sink for marine CDOM. Herein the susceptibility of CDOM to photobleaching by sea surface-level solar radiation was examined in 15 samples collected from wide-ranging open ocean regimes. Samples from the Pacific, Atlantic, Indian and Southern Oceans were irradiated over several days with full-spectrum light under a solar simulator at in situ temperature in order to measure photobleaching rate and derive an empirical matrix, ɛsurf (m-1 μEin-1), which quantifies the effect of surface irradiance on the spectral absorption of CDOM. Irradiation responses among the ocean samples were similar within the ultraviolet (UV) region of the spectrum spanning 300-360 nm, generally exhibiting a decrease in the CDOM absorption coefficient (m-1) and concomitant increase in the CDOM spectral slope parameter, S (nm-1). However, an unexpected irradiation-induced increase in CDOM absorption between approximately 360 and 500 nm was observed for samples from high-nutrient low-chlorophyll (HNLC) environments. This finding was linked to the presence of dissolved nitrate and may explain discrepancies in action spectra for dimethylsulfide (DMS) photobleaching observed between the Equatorial Pacific and Subtropical North Atlantic Oceans. The nitrate-to-phosphate ratio explained 27-70% of observed variability in ɛsurf at observation wavelengths of 330-440 nm, while the initial spectral slope of the samples explained up to 52% of variability in ɛsurf at observation wavelengths of 310-330 nm. These results suggest that the biogeochemical and solar exposure history of the water column, each of which influence the chemical character and thus the spectral quality of CDOM and its photoreactivity, are the main factors regulating the susceptibility of CDOM to photodegradation in the surface ocean. The ɛsurf parameter reported herein may be applied to remote sensing retrievals of CDOM to estimate photobleaching at the surface on regional to global scales.

SEA Semester Undergraduates Research the Ocean's Role in Climate Systems in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Meyer, A. W.; Becker, M. K.; Grabb, K. C.

2014-12-01

Sea Education Association (SEA)'s fully accredited Oceans & Climate SEA Semester program provides upper-level science undergraduates a unique opportunity to explore the ocean's role in the global climate system as they conduct real-world oceanographic research and gain first-hand understanding of and appreciation for the collaborative nature of the scientific research process. Oceans & Climate is an interdisciplinary science and policy semester in which students also explore public policy perspectives to learn how scientific knowledge is used in making climate-related policy. Working first at SEA's shore campus, students collaborate with SEA faculty and other researchers in the local Woods Hole scientific community to design and develop an original research project to be completed at sea. Students then participate as full, working members of the scientific team and sailing crew aboard the 134-foot brigantine SSV Robert C. Seamans; they conduct extensive oceanographic sampling, manage shipboard operations, and complete and present the independent research project they designed onshore. Oceans & Climate SEA Semester Cruise S-250 sailed from San Diego to Tahiti on a 7-week, >4000nm voyage last fall (November-December 2013). This remote open-ocean cruise track traversed subtropical and equatorial regions of the Pacific particularly well suited for a diverse range of climate-focused studies. Furthermore, as SEA has regularly collected scientific data along similar Pacific cruise tracks for more than a decade, students often undertake projects that require time-series analyses. 18 undergraduates from 15 different colleges and universities participated in the S-250 program. Two examples of the many projects completed by S-250 students include a study of the possible relationship between tropical cyclone intensification, driven by warm sea surface temperatures, and the presence of barrier layers; and a study of nutrient cycling in the eastern Pacific, focusing on primary nitrite maximum changes in various oceanographic regions with differing levels of stratification and accompanying localization of microbial communities. These studies, as well as additional scientific and policy projects conducted by other Oceans & Climate students, will be highlighted in this poster presentation.

NREL: U.S. Life Cycle Inventory Database Home Page

Science.gov Websites

U.S. Life-Cycle Inventory Database Buildings Research Photo of a green field with an ocean in the background. U.S. Life Cycle Inventory Database NREL and its partners created the U.S. Life Cycle Inventory (LCI) Database to help life cycle assessment (LCA) practitioners answer questions about environmental

Quantifying the contribution of single microbial cells to nitrogen assimilation in aquatic environments

NASA Astrophysics Data System (ADS)

Musat, N.; Kuypers, M. M. M.

2009-04-01

Nitrogen is a primary productivity-limiting nutrient in the ocean. The nitrogen limitation of productivity may be overcome by organisms capable of converting dissolved N2 into fixed nitrogen available to the ecosystem. In many oceanic regions, growth of phytoplankton is nitrogen limited because fixation of N2 cannot make up for the removal of fixed inorganic nitrogen (NH4+, NO2-, NO3-) by anaerobic microbial processes. The amount of available fixed nitrogen in the ocean can be changed by the biological processes of heterotrophic denitrification, anaerobic ammonium oxidation and nitrogen fixation. For a complete understanding of nitrogen cycling in the ocean a link between the microbial and biogeochemical processes at the single cell level and their role in global biogeochemical cycles is essential. Here we report a recently developed method, Halogen In Situ Hybridization-Secondary Ion Mass Spectroscopy (HISH-SIMS) and its potential application to study the nitrogen-cycle processes in the ocean. The method allows simultaneous phylogenetic identification and quantitation of metabolic activities of single microbial cells in the environment. It uses horseradish-peroxidase-labeled oligonucleotide probes and fluorine-containing tyramides for the identification of microorganisms in combination with stable-isotope-labeling experiments for analyzing the metabolic function of single microbial cells. HISH-SIMS was successfully used to study nitrogen assimilation and nitrogen fixation by anaerobic phototrophs in a meromictic alpine lake. The HISH-SIMS method enables studies of the ecophysiology of individual, phylogenetically identified microorganisms involved in the N-cycle and allows us to track the flow of nitrogen within microbial communities.

The Growing Human Footprint on Coastal and Open-Ocean Biogeochemistry

NASA Astrophysics Data System (ADS)

Doney, Scott C.

2010-06-01

Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in mercury and persistent organic pollutants. Most of these perturbations, tied either directly or indirectly to human fossil fuel combustion, fertilizer use, and industrial activity, are projected to grow in coming decades, resulting in increasing negative impacts on ocean biota and marine resources.

The growing human footprint on coastal and open-ocean biogeochemistry.

PubMed

Doney, Scott C

2010-06-18

Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in mercury and persistent organic pollutants. Most of these perturbations, tied either directly or indirectly to human fossil fuel combustion, fertilizer use, and industrial activity, are projected to grow in coming decades, resulting in increasing negative impacts on ocean biota and marine resources.

Forecasting tsunamis in Poverty Bay, New Zealand, with deep-ocean gauges

NASA Astrophysics Data System (ADS)

Power, William; Tolkova, Elena

2013-12-01

The response/transfer function of a coastal site to a remote open-ocean point is introduced, with the intent to directly convert open-ocean measurements into the wave time history at the site. We show that the tsunami wave at the site can be predicted as the wave is measured in the open ocean as far as 1,000+ km away from the site, with a straightforward computation which can be performed almost instantaneously. The suggested formalism is demonstrated for the purpose of tsunami forecasting in Poverty Bay, in the Gisborne region of New Zealand. Directional sensitivity of the site response due to different conditions for the excitation of the shelf and the bay's normal modes is investigated and used to explain tsunami observations. The suggested response function formalism is validated with available records of the 2010 Chilean tsunami at Gisborne tide gauge and at the nearby deep-ocean assessment and reporting of tsunamis (DART) station 54401. The suggested technique is also demonstrated by hindcasting the 2011 Tohoku tsunami and 2012 Haida Gwaii tsunami at Monterey Bay, CA, using an offshore record of each tsunami at DART station 46411.

Differing growth responses of major phylogenetic groups of marine bacteria to natural phytoplankton blooms in the western North Pacific Ocean.

PubMed

Tada, Yuya; Taniguchi, Akito; Nagao, Ippei; Miki, Takeshi; Uematsu, Mitsuo; Tsuda, Atsushi; Hamasaki, Koji

2011-06-01

Growth and productivity of phytoplankton substantially change organic matter characteristics, which affect bacterial abundance, productivity, and community structure in aquatic ecosystems. We analyzed bacterial community structures and measured activities inside and outside phytoplankton blooms in the western North Pacific Ocean by using bromodeoxyuridine immunocytochemistry and fluorescence in situ hybridization (BIC-FISH). Roseobacter/Rhodobacter, SAR11, Betaproteobacteria, Alteromonas, SAR86, and Bacteroidetes responded differently to changes in organic matter supply. Roseobacter/Rhodobacter bacteria remained widespread, active, and proliferating despite large fluctuations in organic matter and chlorophyll a (Chl-a) concentrations. The relative contribution of Bacteroidetes to total bacterial production was consistently high. Furthermore, we documented the unexpectedly large contribution of Alteromonas to total bacterial production in the bloom. Bacterial abundance, productivity, and growth potential (the proportion of growing cells in a population) were significantly correlated with Chl-a and particulate organic carbon concentrations. Canonical correspondence analysis showed that organic matter supply was critical for determining bacterial community structures. The growth potential of each bacterial group as a function of Chl-a concentration showed a bell-shaped distribution, indicating an optimal organic matter concentration to promote growth. The growth of Alteromonas and Betaproteobacteria was especially strongly correlated with organic matter supply. These data elucidate the distinctive ecological role of major bacterial taxa in organic matter cycling during open ocean phytoplankton blooms.

Differing Growth Responses of Major Phylogenetic Groups of Marine Bacteria to Natural Phytoplankton Blooms in the Western North Pacific Ocean ▿ †

PubMed Central

Tada, Yuya; Taniguchi, Akito; Nagao, Ippei; Miki, Takeshi; Uematsu, Mitsuo; Tsuda, Atsushi; Hamasaki, Koji

2011-01-01

Growth and productivity of phytoplankton substantially change organic matter characteristics, which affect bacterial abundance, productivity, and community structure in aquatic ecosystems. We analyzed bacterial community structures and measured activities inside and outside phytoplankton blooms in the western North Pacific Ocean by using bromodeoxyuridine immunocytochemistry and fluorescence in situ hybridization (BIC-FISH). Roseobacter/Rhodobacter, SAR11, Betaproteobacteria, Alteromonas, SAR86, and Bacteroidetes responded differently to changes in organic matter supply. Roseobacter/Rhodobacter bacteria remained widespread, active, and proliferating despite large fluctuations in organic matter and chlorophyll a (Chl-a) concentrations. The relative contribution of Bacteroidetes to total bacterial production was consistently high. Furthermore, we documented the unexpectedly large contribution of Alteromonas to total bacterial production in the bloom. Bacterial abundance, productivity, and growth potential (the proportion of growing cells in a population) were significantly correlated with Chl-a and particulate organic carbon concentrations. Canonical correspondence analysis showed that organic matter supply was critical for determining bacterial community structures. The growth potential of each bacterial group as a function of Chl-a concentration showed a bell-shaped distribution, indicating an optimal organic matter concentration to promote growth. The growth of Alteromonas and Betaproteobacteria was especially strongly correlated with organic matter supply. These data elucidate the distinctive ecological role of major bacterial taxa in organic matter cycling during open ocean phytoplankton blooms. PMID:21515719

Strengthening seasonal marine CO2 variations due to increasing atmospheric CO2

NASA Astrophysics Data System (ADS)

Landschützer, Peter; Gruber, Nicolas; Bakker, Dorothee C. E.; Stemmler, Irene; Six, Katharina D.

2018-01-01

The increase of atmospheric CO2 (ref. 1) has been predicted to impact the seasonal cycle of inorganic carbon in the global ocean2,3, yet the observational evidence to verify this prediction has been missing. Here, using an observation-based product of the oceanic partial pressure of CO2 (pCO2) covering the past 34 years, we find that the winter-to-summer difference of the pCO2 has increased on average by 2.2 ± 0.4 μatm per decade from 1982 to 2015 poleward of 10° latitude. This is largely in agreement with the trend expected from thermodynamic considerations. Most of the increase stems from the seasonality of the drivers acting on an increasing oceanic pCO2 caused by the uptake of anthropogenic CO2 from the atmosphere. In the high latitudes, the concurrent ocean-acidification-induced changes in the buffer capacity of the ocean enhance this effect. This strengthening of the seasonal winter-to-summer difference pushes the global ocean towards critical thresholds earlier, inducing stress to ocean ecosystems and fisheries4. Our study provides observational evidence for this strengthening seasonal difference in the oceanic carbon cycle on a global scale, illustrating the inevitable consequences of anthropogenic CO2 emissions.

Community structures of actively growing bacteria shift along a north-south transect in the western North Pacific

PubMed Central

Taniguchi, Akito; Hamasaki, Koji

2008-01-01

Bacterial community structures and their activities in the ocean are tightly coupled with organic matter fluxes and thus control ocean biogeochemical cycles. Bromodeoxyuridine (BrdU), halogenated nucleoside and thymidine analogue, has been recently used to monitor actively growing bacteria (AGB) in natural environments. We labelled DNA of proliferating cells in seawater bacterial assemblages with BrdU and determined community structures of the bacteria that were possible key species in mediating biochemical reactions in the ocean. Surface seawater samples were collected along a north-south transect in the North Pacific in October 2003 and subjected to BrdU magnetic beads immunocapture and PCR-DGGE (BUMP-DGGE) analysis. Change of BrdU-incorporated community structures reflected the change of water masses along a north-south transect from subarctic to subtropical gyres in the North Pacific. We identified 25 bands referred to AGB as BrdU-incorporated phylotypes, belonging to Alphaproteobacteria (5 bands), Betaproteobacteria (1 band), Gammaproteobacteria (4 bands), Cytophaga-Flavobacterium-Bacteroides (CFB) group bacteria (5 bands), Gram-positive bacteria (6 bands), and Cyanobacteria (4 bands). BrdU-incorporated phylotypes belonging to Vibrionales, Alteromonadales and Gram-positive bacteria appeared only at sampling stations in a subtropical gyre, while those belonging to Roseobacter-related bacteria and CFB group bacteria appeared at the stations in both subarctic and subtropical gyres. Our result revealed phylogenetic affiliation of AGB and their dynamic change along with north-south environmental gradients in open oceans. Different species of AGB utilize different amount and kinds of substrates, which can affect the change of organic matter fluxes along transect. PMID:18177366

Preparing to predict: The Second Autonomous Ocean Sampling Network (AOSN-II) experiment in the Monterey Bay

NASA Astrophysics Data System (ADS)

Ramp, S. R.; Davis, R. E.; Leonard, N. E.; Shulman, I.; Chao, Y.; Robinson, A. R.; Marsden, J.; Lermusiaux, P. F. J.; Fratantoni, D. M.; Paduan, J. D.; Chavez, F. P.; Bahr, F. L.; Liang, S.; Leslie, W.; Li, Z.

2009-02-01

The Autonomous Ocean Sampling Network Phase Two (AOSN-II) experiment was conducted in and offshore from the Monterey Bay on the central California coast during July 23-September 6, 2003. The objective of the experiment was to learn how to apply new tools, technologies, and analysis techniques to adaptively sample the coastal ocean in a manner demonstrably superior to traditional methodologies, and to use the information gathered to improve predictive skill for quantities of interest to end-users. The scientific goal was to study the upwelling/relaxation cycle near an open coastal bay in an eastern boundary current region, particularly as it developed and spread from a coastal headland. The suite of observational tools used included a low-flying aircraft, a fleet of underwater gliders, including several under adaptive autonomous control, and propeller-driven AUVs in addition to moorings, ships, and other more traditional hardware. The data were delivered in real time and assimilated into the Harvard Ocean Prediction System (HOPS), the Navy Coastal Ocean Model (NCOM), and the Jet Propulsion Laboratory implementation of the Regional Ocean Modeling System (JPL/ROMS). Two upwelling events and one relaxation event were sampled during the experiment. The upwelling in both cases began when a pool of cold water less than 13 °C appeared near Cape Año Nuevo and subsequently spread offshore and southward across the bay as the equatorward wind stress continued. The primary difference between the events was that the first event spread offshore and southward, while the second event spread only southward and not offshore. The difference is attributed to the position and strength of meanders and eddies of the California Current System offshore, which blocked or steered the cold upwelled water. The space and time scales of the mesoscale variability were much shorter than have been previously observed in deep-water eddies offshore. Additional process studies are needed to elucidate the dynamics of the flow.

Oceanographic and atmospheric conditions on the continental shelf north of the Monterey Bay during August 2006

NASA Astrophysics Data System (ADS)

Ramp, Steven R.; Lermusiaux, Pierre F. J.; Shulman, Igor; Chao, Yi; Wolf, Rebecca E.; Bahr, Frederick L.

2011-09-01

A comprehensive data set from the ocean and atmosphere was obtained just north of the Monterey Bay as part of the Monterey Bay 2006 (MB06) field experiment. The wind stress, heat fluxes, and sea surface temperature were sampled by the Naval Postgraduate School's TWIN OTTER research aircraft. In situ data were collected using ships, moorings, gliders and AUVs. Four data-assimilating numerical models were additionally run, including the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS ®) model for the atmosphere and the Harvard Ocean Prediction System (HOPS), the Regional Ocean Modeling System (ROMS), and the Navy Coastal Ocean Model (NCOM) for the ocean. The scientific focus of the Adaptive Sampling and Prediction Experiment (ASAP) was on the upwelling/relaxation cycle and the resulting three-dimensional coastal circulation near a coastal promontory, in this case Point Año Nuevo, CA. The emphasis of this study is on the circulation over the continental shelf as estimated from the wind forcing, two ADCP moorings, and model outputs. The wind stress during August 2006 consisted of 3-10 day upwelling favorable events separated by brief 1-3 day relaxations. During the first two weeks there was some correlation between local winds and currents and the three models' capability to reproduce the events. During the last two weeks, largely equatorward surface wind stress forced the sea surface and barotropic poleward flow occurred over the shelf, reducing model skill at predicting the circulation. The poleward flow was apparently remotely forced by mesoscale eddies and alongshore pressure gradients, which were not well simulated by the models. The small, high-resolution model domains were highly reliant on correct open boundary conditions to drive these larger-scale poleward flows. Multiply-nested models were no more effective than well-initialized local models in this respect.

Are changes in the phytoplankton community structure altering the flux of CO2 in regions of the North Atlantic?

NASA Astrophysics Data System (ADS)

Ostle, C.; Landschutzer, P.; Johnson, M.; Schuster, U.; Watson, A. J.; Edwards, M.; Robinson, C.

2016-02-01

The North Atlantic Ocean is a globally important sink of carbon dioxide (CO2). However, the strength of the sink varies temporally and regionally. This study uses a neural network method to map the surface ocean pCO2 (partial pressure of CO2) and flux of CO2from the atmosphere to the ocean alongside measurements of plankton abundance collected from the Continuous Plankton Recorder (CPR) survey to determine the relationship between regional changes in phytoplankton community structure and regional differences in carbon flux. Despite increasing sea surface temperatures, the Grand Banks of Newfoundland show a decrease in sea surface pCO2 of -2 µatm yr-1 from 1993 to 2011. The carbon flux in the North Sea is variable over the same period. This is in contrast to most of the open ocean within the North Atlantic, where increases in sea surface pCO2 follow the trend of increasing CO2 in the atmosphere, i.e. the flux or sink remains constant. The increasing CO2 sink in the Grand Banks of Newfoundland and the variable sink in the North Sea correlate with changes in phytoplankton community composition. This study investigates the biogeochemical and oceanographic mechanisms potentially linking increasing sea surface temperature, changes in phytoplankton community structure and the changing carbon sink in these two important regions of the Atlantic Ocean. The use of volunteer ships to concurrently collect these datasets demonstrates the potential to investigate relationships between plankton community structure and carbon flux in a cost-effective way. These results not only have implications for plankton-dynamic biogeochemical models, but also likely influence carbon export, as different phytoplankton communities have different carbon export efficiencies. Extending and maintaining such datasets is critical to improving our understanding of and monitoring carbon cycling in the surface ocean and improving climate model accuracy.

Mechanisms for Seasonal and Interannual Sea Surface Salinity Variability in the Indian Ocean

NASA Astrophysics Data System (ADS)

Köhler, J.; Stammer, D.; Serra, N.; Bryan, F.

2016-12-01

Space-borne salinity data in the Indian Ocean are analyzed over the period 2000-2015 based on data from the European Space Agency's (ESA) "Soil Moisture and Ocean Salinity" (SMOS) and the National Aeronautical Space Agency's (NASA) "Aquarius/SAC-D" missions. The seasonal variability is the dominant mode of sea surface salinity (SSS) variability in the Indian Ocean, accounting for more than 50% of salinity variance. Through a combined analysis of the satellite and ARGO data, dominant forcing terms for seasonal salinity changes are identified. It is found, that E-P controls seasonal salinity tendency in the western Indian Ocean, where the ITCZ has a strong seasonal cycle. In contrast, Ekman advection is the dominant term in the northern and eastern equatorial Indian Ocean. The influence of vertical processes on the salinity tendency is enhanced in coastal upwelling regions and south of the equator due to mid-ocean upwelling. Jointly those processes can explain most of the observed seasonal cycle with a correlation of 0.85 and an RMS difference of 0.07/month. However, the detailed composition of driving terms depends on underlying data products. In general, our study confirms previous results from Lisan Yu (2011); however, in the eastern Indian Ocean contrasting results indicate the leading role of meridional Ekman advection to the seasonal salinity tendency instead of surface external forces due to precipitation. The inferred dominant salinity budget terms are confirmed by results obtained from a high resolution NCAR Core model run driven by NCEP forcing fields. From an EOF analysis of the salinity fields after substracting the annual and semiannual cycle we found that the first EOF mode explains more than 20% of salinity variance. The first principal component of SSS EOF is correlated with the Indian Ocean Dipole Mode Index. Nevertheless the EOF pattern shows a meridional tripole structure, while the IOD describes a zonal SST dipole (Saji et al, 1999).

Uncertainty in Earth System Models: Benchmarks for Ocean Model Performance and Validation

NASA Astrophysics Data System (ADS)

Ogunro, O. O.; Elliott, S.; Collier, N.; Wingenter, O. W.; Deal, C.; Fu, W.; Hoffman, F. M.

2017-12-01

The mean ocean CO2 sink is a major component of the global carbon budget, with marine reservoirs holding about fifty times more carbon than the atmosphere. Phytoplankton play a significant role in the net carbon sink through photosynthesis and drawdown, such that about a quarter of anthropogenic CO2 emissions end up in the ocean. Biology greatly increases the efficiency of marine environments in CO2 uptake and ultimately reduces the impact of the persistent rise in atmospheric concentrations. However, a number of challenges remain in appropriate representation of marine biogeochemical processes in Earth System Models (ESM). These threaten to undermine the community effort to quantify seasonal to multidecadal variability in ocean uptake of atmospheric CO2. In a bid to improve analyses of marine contributions to climate-carbon cycle feedbacks, we have developed new analysis methods and biogeochemistry metrics as part of the International Ocean Model Benchmarking (IOMB) effort. Our intent is to meet the growing diagnostic and benchmarking needs of ocean biogeochemistry models. The resulting software package has been employed to validate DOE ocean biogeochemistry results by comparison with observational datasets. Several other international ocean models contributing results to the fifth phase of the Coupled Model Intercomparison Project (CMIP5) were analyzed simultaneously. Our comparisons suggest that the biogeochemical processes determining CO2 entry into the global ocean are not well represented in most ESMs. Polar regions continue to show notable biases in many critical biogeochemical and physical oceanographic variables. Some of these disparities could have first order impacts on the conversion of atmospheric CO2 to organic carbon. In addition, single forcing simulations show that the current ocean state can be partly explained by the uptake of anthropogenic emissions. Combined effects of two or more of these forcings on ocean biogeochemical cycles and ecosystems are challenging to predict since additive or antagonistic effects may occur. A benchmarking tool for accurate assessment and validation of marine biogeochemical outputs will be indispensable as the model community continues to improve ESM developments. It will provide a first order tool in understanding climate-carbon cycle feedbacks.

Natural biogeochemical cycle of mercury in a global three-dimensional ocean tracer model

NASA Astrophysics Data System (ADS)

Zhang, Yanxu; Jaeglé, Lyatt; Thompson, LuAnne

2014-05-01

We implement mercury (Hg) biogeochemistry in the offline global 3-D ocean tracer model (OFFTRAC) to investigate the natural Hg cycle, prior to any anthropogenic input. The simulation includes three Hg tracers: dissolved elemental (Hg0aq), dissolved divalent (HgIIaq), and particle-bound mercury (HgPaq). Our Hg parameterization takes into account redox chemistry in ocean waters, air-sea exchange of Hg0, scavenging of HgIIaq onto sinking particles, and resupply of HgIIaq at depth by remineralization of sinking particles. Atmospheric boundary conditions are provided by a global simulation of the natural atmospheric Hg cycle in the GEOS-Chem model. In the surface ocean, the OFFTRAC model predicts global mean concentrations of 0.16 pM for total Hg, partitioned as 80% HgIIaq, 14% Hg0aq, and 6% HgPaq. Total Hg concentrations increase to 0.38 pM in the thermocline/intermediate waters (between the mixed layer and 1000 m depth) and 0.82 pM in deep waters (below 1000 m), reflecting removal of Hg from the surface to the subsurface ocean by particle sinking followed by remineralization at depth. Our model predicts that Hg concentrations in the deep North Pacific Ocean (>2000 m) are a factor of 2-3 higher than in the deep North Atlantic Ocean. This is the result of cumulative input of Hg from particle remineralization as deep waters transit from the North Atlantic to the North Pacific on their ~2000 year journey. The model is able to reproduce the relatively uniform concentrations of total Hg observed in the old deep waters of the North Pacific Ocean (observations: 1.2 ± 0.4 pM; model: 1.1 ± 0.04 pM) and Southern Ocean (observations: 1.1 ± 0.2 pM; model: 0.8 ± 0.02 pM). However, the modeled concentrations are factors of 5-6 too low compared to observed concentrations in the surface ocean and in the young water masses of the deep North Atlantic Ocean. This large underestimate for these regions implies a factor of 5-6 anthropogenic enhancement in Hg concentrations.

Acidification at the Surface in the East Sea: A Coupled Climate-carbon Cycle Model Study

NASA Astrophysics Data System (ADS)

Park, Young-Gyu; Seol, Kyung-Hee; Boo, Kyung-On; Lee, Johan; Cho, Chunho; Byun, Young-Hwa; Seo, Seongbong

2018-05-01

This modeling study investigates the impacts of increasing atmospheric CO2 concentration on acidification in the East Sea. A historical simulation for the past three decades (1980 to 2010) was performed using the Hadley Centre Global Environmental Model (version 2), a coupled climate model with atmospheric, terrestrial and ocean cycles. As the atmospheric CO2 concentration increased, acidification progressed in the surface waters of the marginal sea. The acidification was similar in magnitude to observations and models of acidification in the global ocean. However, in the global ocean, the acidification appears to be due to increased in-situ oceanic CO2 uptake, whereas local processes had stronger effects in the East Sea. pH was lowered by surface warming and by the influx of water with higher dissolved inorganic carbon (DIC) from the northwestern Pacific. Due to the enhanced advection of DIC, the partial pressure of CO2 increased faster than in the overlying air; consequently, the in-situ oceanic uptake of CO2 decreased.

Ocean export production and foraminiferal stable isotopes in the Antarctic Southern Ocean across the mid-Pleistocene transition

NASA Astrophysics Data System (ADS)

Hasenfratz, A. P.; Martinez-Garcia, A.; Jaccard, S.; Hodell, D. A.; Vance, D.; Bernasconi, S. M.; Greaves, M.; Haug, G. H.

2014-12-01

Changes in buoyancy forcing in the Antarctic Zone (AZ) of the Southern Ocean are believed to play an instrumental role in modulating atmospheric CO2 concentrations during glacial cycles by regulating the transfer of carbon between the ocean interior and the atmosphere. Indeed, a million-year-spanning high-resolution excess Barium record from the AZ of the South Atlantic (ODP 1094), which traces changes in export production, shows decreased export production during cold periods suggesting decreased overturning. Here, we extend this AZ export production record back to 1.6 Myr. In addition, we present new carbon and oxygen isotope records of benthic and planktic foraminifera from the same site, complemented by Mg/Ca measurements in some intervals. The interpretation of these new data in the context of other South Atlantic records contributes to a better understanding of Southern Ocean hydrography and its role in modulating glacial/interglacial cycles over the past 1.6 Myr.

On the role of mesoscale eddies for the biological productivity and biogeochemistry in the eastern tropical Pacific Ocean off Peru

NASA Astrophysics Data System (ADS)

Stramma, L.; Bange, H. W.; Czeschel, R.; Lorenzo, A.; Frank, M.

2013-06-01

Mesoscale eddies seem to play an important role for both the hydrography and biogeochemistry of the eastern tropical Pacific Ocean (ETSP) off Peru. However, detailed surveys of these eddies are not available, which has so far hampered an in depth understanding of their implications for nutrient distribution and biological productivity. In this study three eddies along a section at 16°45' S have been surveyed intensively during R/V Meteor cruise M90 in November 2012. A coastal mode water eddy, an open ocean mode water eddy and an open ocean cyclonic eddy have been identified and sampled in order to determine both their hydrographic properties and their influence on the biogeochemical setting of the ETSP. In the thermocline the temperature of the coastal anticyclonic eddy was up to 2 °C warmer, 0.2 more saline and the swirl velocity was up to 35 cm s-1. The observed temperature and salinity anomalies, as well as swirl velocities of both types of eddies were about twice as large as had been described for the mean eddies in the ETSP and the observed heat and salt anomalies (AHA, ASA) show a much larger variability than the mean AHA and ASA. We found that the eddies contributed significantly to productivity by maintaining pronounced subsurface maxima of chlorophyll. Based on a comparison of the coastal (young) mode water eddy and the open ocean (old) mode water eddy we conclude that the aging of eddies when they detach from the coast and move westward to the open ocean considerably influences the eddies' properties: chlorophyll maxima are weaker and nutrients are subducted. The coastal mode water eddy was found to be a hotspot of nitrogen loss in the OMZ, whereas, the open ocean cyclonic eddy was of negligible importance for nitrogen loss. Our results show that the important role the eddies play in the ETSP can only be fully deciphered and understood through dedicated high spatial and temporal resolution oceanographic/biogeochemical surveys.

Evaluating the performance of Sentinel-3 SRAL SAR Altimetry in the Coastal and Open Ocean, and developing improved retrieval methods - The ESA SCOOP Project.

NASA Astrophysics Data System (ADS)

Benveniste, J.; Cotton, D.; Moreau, T.; Varona, E.; Roca, M.; Cipollini, P.; Cancet, M.; Martin, F.; Fenoglio-Marc, L.; Naeije, M.; Fernandes, J.; Restano, M.; Ambrozio, A.

2016-12-01

The ESA Sentinel-3 satellite, launched in February 2016 as a part of the Copernicus programme, is the second satellite to operate a SAR mode altimeter. The Sentinel 3 Synthetic Aperture Radar Altimeter (SRAL) is based on the heritage from Cryosat-2, but this time complemented by a Microwave Radiometer (MWR) to provide a wet troposphere correction, and operating at Ku and C-Bands to provide an accurate along-track ionospheric correction. Together this instrument package, including both GPS and DORIS instruments for accurate positioning, allows accurate measurements of sea surface height over the ocean, as well as measurements of significant wave height and surface wind speed. SCOOP (SAR Altimetry Coastal & Open Ocean Performance) is a project funded under the ESA SEOM (Scientific Exploitation of Operational Missions) Programme Element, started in September 2015, to characterise the expected performance of Sentinel-3 SRAL SAR mode altimeter products, in the coastal zone and open-ocean, and then to develop and evaluate enhancements to the baseline processing scheme in terms of improvements to ocean measurements. There is also a work package to develop and evaluate an improved Wet Troposphere correction for Sentinel-3, based on the measurements from the on-board MWR, further enhanced mostly in the coastal and polar regions using third party data, and provide recommendations for use. At the end of the project recommendations for further developments and implementations will be provided through a scientific roadmap. In this presentation we provide an overview of the SCOOP project, highlighting the key deliverables and discussing the potential impact of the results in terms of the application of delay-Doppler (SAR) altimeter measurements over the open-ocean and coastal zone. We also present the initial results from the project, including: Key findings from a review of the current "state-of-the-art" for SAR altimetry, Specification of the initial "reference" delay-Doppler and echo modelling /retracking processing schemes, Evaluation of the initial Test Data Set in the Open Ocean and Coastal Zone Overview of modifications planned to the reference delay-Doppler and echo modelling/ re-tracking processing schemes.

The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change

PubMed Central

Keeling, Charles D.; Whorf, Timothy P.

2000-01-01

Variations in solar irradiance are widely believed to explain climatic change on 20,000- to 100,000-year time-scales in accordance with the Milankovitch theory of the ice ages, but there is no conclusive evidence that variable irradiance can be the cause of abrupt fluctuations in climate on time-scales as short as 1,000 years. We propose that such abrupt millennial changes, seen in ice and sedimentary core records, were produced in part by well characterized, almost periodic variations in the strength of the global oceanic tide-raising forces caused by resonances in the periodic motions of the earth and moon. A well defined 1,800-year tidal cycle is associated with gradually shifting lunar declination from one episode of maximum tidal forcing on the centennial time-scale to the next. An amplitude modulation of this cycle occurs with an average period of about 5,000 years, associated with gradually shifting separation-intervals between perihelion and syzygy at maxima of the 1,800-year cycle. We propose that strong tidal forcing causes cooling at the sea surface by increasing vertical mixing in the oceans. On the millennial time-scale, this tidal hypothesis is supported by findings, from sedimentary records of ice-rafting debris, that ocean waters cooled close to the times predicted for strong tidal forcing. PMID:10725399

Ocean deoxygenation, the global phosphorus cycle and the possibility of human-caused large-scale ocean anoxia.

PubMed

Watson, Andrew J; Lenton, Timothy M; Mills, Benjamin J W

2017-09-13

The major biogeochemical cycles that keep the present-day Earth habitable are linked by a network of feedbacks, which has led to a broadly stable chemical composition of the oceans and atmosphere over hundreds of millions of years. This includes the processes that control both the atmospheric and oceanic concentrations of oxygen. However, one notable exception to the generally well-behaved dynamics of this system is the propensity for episodes of ocean anoxia to occur and to persist for 10 5 -10 6 years, these ocean anoxic events (OAEs) being particularly associated with warm 'greenhouse' climates. A powerful mechanism responsible for past OAEs was an increase in phosphorus supply to the oceans, leading to higher ocean productivity and oxygen demand in subsurface water. This can be amplified by positive feedbacks on the nutrient content of the ocean, with low oxygen promoting further release of phosphorus from ocean sediments, leading to a potentially self-sustaining condition of deoxygenation. We use a simple model for phosphorus in the ocean to explore this feedback, and to evaluate the potential for humans to bring on global-scale anoxia by enhancing P supply to the oceans. While this is not an immediate global change concern, it is a future possibility on millennial and longer time scales, when considering both phosphate rock mining and increased chemical weathering due to climate change. Ocean deoxygenation, once begun, may be self-sustaining and eventually could result in long-lasting and unpleasant consequences for the Earth's biosphere.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Authors.

Ocean deoxygenation, the global phosphorus cycle and the possibility of human-caused large-scale ocean anoxia

PubMed Central

Lenton, Timothy M.; Mills, Benjamin J. W.

2017-01-01

The major biogeochemical cycles that keep the present-day Earth habitable are linked by a network of feedbacks, which has led to a broadly stable chemical composition of the oceans and atmosphere over hundreds of millions of years. This includes the processes that control both the atmospheric and oceanic concentrations of oxygen. However, one notable exception to the generally well-behaved dynamics of this system is the propensity for episodes of ocean anoxia to occur and to persist for 105–106 years, these ocean anoxic events (OAEs) being particularly associated with warm ‘greenhouse’ climates. A powerful mechanism responsible for past OAEs was an increase in phosphorus supply to the oceans, leading to higher ocean productivity and oxygen demand in subsurface water. This can be amplified by positive feedbacks on the nutrient content of the ocean, with low oxygen promoting further release of phosphorus from ocean sediments, leading to a potentially self-sustaining condition of deoxygenation. We use a simple model for phosphorus in the ocean to explore this feedback, and to evaluate the potential for humans to bring on global-scale anoxia by enhancing P supply to the oceans. While this is not an immediate global change concern, it is a future possibility on millennial and longer time scales, when considering both phosphate rock mining and increased chemical weathering due to climate change. Ocean deoxygenation, once begun, may be self-sustaining and eventually could result in long-lasting and unpleasant consequences for the Earth's biosphere. This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’. PMID:28784709

Radiocarbon evidence for a smaller oceanic carbon dioxide sink than previously believed

NASA Astrophysics Data System (ADS)

Hesshaimer, Vago; Heimann, Martin; Levin, Ingeborg

1994-07-01

RADIOCARBON produced naturally in the upper atmosphere or arti-ficially during nuclear weapons testing is the main tracer used to validate models of oceanic carbon cycling, in particular the exchange of carbon dioxide with the atmosphere1-3 and the mixing parameters within the ocean itself4-7. Here we test the overall consistency of exchange fluxes between all relevant compartments in a simple model of the global carbon cycle, using measurements of the long-term tropospheric CO2 concentration8 and radiocarbon composition9-12, the bomb 14C inventory in the stratosphere13,14 and a compilation of bomb detonation dates and strengths15. We find that to balance the budget, we must invoke an extra source to account for 25% of the generally accepted uptake of bomb 14C by the oceans3. The strength of this source decreases from 1970 onwards, with a characteristic timescale similar to that of the ocean uptake. Significant radiocarbon transport from the remote high stratosphere and significantly reduced uptake of bomb 14C by the biosphere can both be ruled out by observational constraints. We therefore conclude that the global oceanic bomb 14C inventory should be revised downwards. A smaller oceanic bomb 14C inventory also implies a smaller oceanic radiocarbon penetration depth16, which in turn implies that the oceans take up 25% less anthropogenic CO2 than had previously been believed.

Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction

NASA Astrophysics Data System (ADS)

Schmittner, Andreas; Galbraith, Eric D.; Hostetler, Steven W.; Pedersen, Thomas F.; Zhang, Rong

2007-09-01

Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that explain how changes in deepwater subduction in the North Atlantic can cause large and synchronous variations of oxygen minimum zones throughout the Northern Hemisphere of the Indian and Pacific oceans, consistent with the paleoclimate records. Cold periods in the North Atlantic are associated with reduced nutrient delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. Reduced export production diminishes subsurface respiration of organic matter leading to higher oxygen concentrations and less denitrification. This effect of reduced oxygen consumption dominates at low latitudes. At high latitudes in the Southern Ocean and North Pacific, increased mixed layer depths and steepening of isopycnals improve ocean ventilation and oxygen supply to the subsurface. Atmospheric teleconnections through changes in wind-driven ocean circulation modify this basin-scale pattern regionally. These results suggest that changes in the Atlantic Ocean circulation, similar to those projected by climate models to possibly occur in the centuries to come because of anthropogenic climate warming, can have large effects on marine ecosystems and biogeochemical cycles even in remote areas.

Global declines in oceanic nitrification rates as a consequence of ocean acidification.

PubMed

Beman, J Michael; Chow, Cheryl-Emiliane; King, Andrew L; Feng, Yuanyuan; Fuhrman, Jed A; Andersson, Andreas; Bates, Nicholas R; Popp, Brian N; Hutchins, David A

2011-01-04

Ocean acidification produced by dissolution of anthropogenic carbon dioxide (CO(2)) emissions in seawater has profound consequences for marine ecology and biogeochemistry. The oceans have absorbed one-third of CO(2) emissions over the past two centuries, altering ocean chemistry, reducing seawater pH, and affecting marine animals and phytoplankton in multiple ways. Microbially mediated ocean biogeochemical processes will be pivotal in determining how the earth system responds to global environmental change; however, how they may be altered by ocean acidification is largely unknown. We show here that microbial nitrification rates decreased in every instance when pH was experimentally reduced (by 0.05-0.14) at multiple locations in the Atlantic and Pacific Oceans. Nitrification is a central process in the nitrogen cycle that produces both the greenhouse gas nitrous oxide and oxidized forms of nitrogen used by phytoplankton and other microorganisms in the sea; at the Bermuda Atlantic Time Series and Hawaii Ocean Time-series sites, experimental acidification decreased ammonia oxidation rates by 38% and 36%. Ammonia oxidation rates were also strongly and inversely correlated with pH along a gradient produced in the oligotrophic Sargasso Sea (r(2) = 0.87, P < 0.05). Across all experiments, rates declined by 8-38% in low pH treatments, and the greatest absolute decrease occurred where rates were highest off the California coast. Collectively our results suggest that ocean acidification could reduce nitrification rates by 3-44% within the next few decades, affecting oceanic nitrous oxide production, reducing supplies of oxidized nitrogen in the upper layers of the ocean, and fundamentally altering nitrogen cycling in the sea.

NASA Tropical Rainfall Measurement Mission (TRMM): Effects of tropical rainfall on upper ocean dynamics, air-sea coupling and hydrologic cycle

NASA Technical Reports Server (NTRS)

Lagerloef, Gary; Busalacchi, Antonio J.; Liu, W. Timothy; Lukas, Roger B.; Niiler, Pern P.; Swift, Calvin T.

1995-01-01

This was a Tropical Rainfall Measurement Mission (TRMM) modeling, analysis and applications research project. Our broad scientific goals addressed three of the seven TRMM Priority Science Questions, specifically: What is the monthly average rainfall over the tropical ocean areas of about 10(exp 5) sq km, and how does this rain and its variability affect the structure and circulation of the tropical oceans? What is the relationship between precipitation and changes in the boundary conditions at the Earth's surface (e.g., sea surface temperature, soil properties, vegetation)? How can improved documentation of rainfall improve understanding of the hydrological cycle in the tropics?

Barium isotopes reveal role of ocean circulation on barium cycling in the Atlantic

NASA Astrophysics Data System (ADS)

Bates, Stephanie L.; Hendry, Katharine R.; Pryer, Helena V.; Kinsley, Christopher W.; Pyle, Kimberley M.; Woodward, E. Malcolm S.; Horner, Tristan J.

2017-05-01

We diagnose the relative influences of local-scale biogeochemical cycling and regional-scale ocean circulation on Atlantic barium cycling by analysing four new depth profiles of dissolved Ba concentrations and isotope compositions from the South and tropical North Atlantic. These new profiles exhibit systematic vertical, zonal and meridional variations that reflect the influence of both local-scale barite cycling and large-scale ocean circulation. Epipelagic decoupling of dissolved Ba and Si reported previously in the tropics is also found to be associated with significant Ba isotope heterogeneity. As such, we contend that this decoupling originates from the depth segregation of opal and barite formation but is exacerbated by weak vertical mixing. Zonal influence from isotopically-'heavy' water masses in the western North Atlantic evidence the advective inflow of Ba-depleted Upper Labrador Sea Water, which is not seen in the eastern basin or the South Atlantic. Meridional variations in Atlantic Ba isotope systematics below 2000 m appear entirely controlled by conservative mixing. Using an inverse isotopic mixing model, we calculate the Ba isotope composition of the Ba-poor northern end-member as +0.45 ‰ and the Ba-rich southern end-member +0.26 ‰, relative to NIST SRM 3104a. The near-conservative behaviour of Ba below 2000 m indicates that Ba isotopes can serve as an independent tracer of the provenance of northern- versus southern-sourced water masses in the deep Atlantic Ocean. This finding may prove useful in palaeoceanographic studies, should appropriate sedimentary archives be identified, and offers new insights into the processes that cycle Ba in seawater.

Nonlinear Interactions between Climate and Atmospheric Carbon Dioxide Drivers of Terrestrial and Marine Carbon Cycle Changes

NASA Astrophysics Data System (ADS)

Hoffman, F. M.; Randerson, J. T.; Moore, J. K.; Goulden, M.; Fu, W.; Koven, C.; Swann, A. L. S.; Mahowald, N. M.; Lindsay, K. T.; Munoz, E.

2017-12-01

Quantifying interactions between global biogeochemical cycles and the Earth system is important for predicting future atmospheric composition and informing energy policy. We applied a feedback analysis framework to three sets of Historical (1850-2005), Representative Concentration Pathway 8.5 (2006-2100), and its extension (2101-2300) simulations from the Community Earth System Model version 1.0 (CESM1(BGC)) to quantify drivers of terrestrial and ocean responses of carbon uptake. In the biogeochemically coupled simulation (BGC), the effects of CO2 fertilization and nitrogen deposition influenced marine and terrestrial carbon cycling. In the radiatively coupled simulation (RAD), the effects of rising temperature and circulation changes due to radiative forcing from CO2, other greenhouse gases, and aerosols were the sole drivers of carbon cycle changes. In the third, fully coupled simulation (FC), both the biogeochemical and radiative coupling effects acted simultaneously. We found that climate-carbon sensitivities derived from RAD simulations produced a net ocean carbon storage climate sensitivity that was weaker and a net land carbon storage climate sensitivity that was stronger than those diagnosed from the FC and BGC simulations. For the ocean, this nonlinearity was associated with warming-induced weakening of ocean circulation and mixing that limited exchange of dissolved inorganic carbon between surface and deeper water masses. For the land, this nonlinearity was associated with strong gains in gross primary production in the FC simulation, driven by enhancements in the hydrological cycle and increased nutrient availability. We developed and applied a nonlinearity metric to rank model responses and driver variables. The climate-carbon cycle feedback gain at 2300 was 42% higher when estimated from climate-carbon sensitivities derived from the difference between FC and BGC than when derived from RAD. We re-analyzed other CMIP5 model results to quantify the effects of such nonlinearities on their projected climate-carbon cycle feedback gains.

Terrestrial dissolved organic matter distribution in the North Sea.

PubMed

Painter, Stuart C; Lapworth, Dan J; Woodward, E Malcolm S; Kroeger, Silke; Evans, Chris D; Mayor, Daniel J; Sanders, Richard J

2018-07-15

The flow of terrestrial carbon to rivers and inland waters is a major term in the global carbon cycle. The organic fraction of this flux may be buried, remineralized or ultimately stored in the deep ocean. The latter can only occur if terrestrial organic carbon can pass through the coastal and estuarine filter, a process of unknown efficiency. Here, data are presented on the spatial distribution of terrestrial fluorescent and chromophoric dissolved organic matter (FDOM and CDOM, respectively) throughout the North Sea, which receives organic matter from multiple distinct sources. We use FDOM and CDOM as proxies for terrestrial dissolved organic matter (tDOM) to test the hypothesis that tDOM is quantitatively transferred through the North Sea to the open North Atlantic Ocean. Excitation emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC) revealed a single terrestrial humic-like class of compounds whose distribution was restricted to the coastal margins and, via an inverse salinity relationship, to major riverine inputs. Two distinct sources of fluorescent humic-like material were observed associated with the combined outflows of the Rhine, Weser and Elbe rivers in the south-eastern North Sea and the Baltic Sea outflow to the eastern central North Sea. The flux of tDOM from the North Sea to the Atlantic Ocean appears insignificant, although tDOM export may occur through Norwegian coastal waters unsampled in our study. Our analysis suggests that the bulk of tDOM exported from the Northwest European and Scandinavian landmasses is buried or remineralized internally, with potential losses to the atmosphere. This interpretation implies that the residence time in estuarine and coastal systems exerts an important control over the fate of tDOM and needs to be considered when evaluating the role of terrestrial carbon losses in the global carbon cycle. Copyright © 2018 The Author(s). Published by Elsevier B.V. All rights reserved.

Spatially Explicit Models of Carbon and Alkalinity Cycling in the Coastal Oceans

NASA Astrophysics Data System (ADS)

O'Mara, N. A.; Dunne, J. P.

2016-12-01

Calcium carbonate (CaCO3) production, dissolution, and preservation are strongly influenced by seawater temperature and carbon chemistry and thus play a key role in the global carbon cycle and are highly susceptible to influence by climate change. Coastal and continental shelf (neritic) environments have been estimated to account for more than half of all CaCO3 accumulation in ocean sediment globally. Unfortunately, current neritic CaCO3 budgets are muddled with assumptions of the spatial extent of various communities, rely on long term averages rather than deterministic relationships for production rates, and therefore have little predictive power for quantifying the impact of climate change on this system. Current biogeochemical components of globally coupled earth system models include open ocean pelagic CaCO3 production and deep sea preservation (0.130 PgC yr-1), but do not resolve nearshore pelagic or benthic production. Here, a 1° spatially explicit model for determining CaCO3 accumulation in neritic sediments is developed. Globally gridded observational, satellite, and benthic community area data are used to calculate rates of benthic and pelagic community CaCO3 production and preservation using a set of equations sensitive to temperature, carbonate saturation state, light availability, and nutrients. Accumulation rates (PgC yr-1) of four neritic zone environments are calculated: coral reefs and banks (0.075), seagrass dominated embayments (0.043), carbonate rich shelves (0.042), and carbonate poor shelves (0.0007). This analysis corroborates previous budget predictions of total neritic CaCO3 accumulation (0.160) and additionally supports the hypothesis that benthic CaCO3 production (0.151) in coastal water greatly exceeds pelagic production (0.009). However, results additionally suggest that erroneous assumptions about spatial extent of neritic communities have led to overestimations of coral reef and under estimations of embayment accumulation rates in the past.

Polaro–cryptic mirror of the lookdown as a biological model for open ocean camouflage

PubMed Central

Brady, Parrish C.; Travis, Kort A.; Maginnis, Tara; Cummings, Molly E.

2013-01-01

With no object to hide behind in 3D space, the open ocean represents a challenging environment for camouflage. Conventional strategies for reflective crypsis (e.g., standard mirror) are effective against axially symmetric radiance fields associated with high solar altitudes, yet ineffective against asymmetric polarized radiance fields associated with low solar inclinations. Here we identify a biological model for polaro–crypsis. We measured the surface-reflectance Mueller matrix of live open ocean fish (lookdown, Selene vomer) and seagrass-dwelling fish (pinfish, Lagodon rhomboides) using polarization-imaging and modeling polarization camouflage for the open ocean. Lookdowns occupy the minimization basin of our polarization-contrast space, while pinfish and standard mirror measurements exhibit higher contrast values than optimal. The lookdown reflective strategy achieves significant gains in polaro–crypsis (up to 80%) in comparison with nonpolarization sensitive strategies, such as a vertical mirror. Lookdowns achieve polaro–crypsis across solar altitudes by varying reflective properties (described by 16 Mueller matrix elements mij) with incident illumination. Lookdowns preserve reflected polarization aligned with principle axes (dorsal–ventral and anterior–posterior, m22 = 0.64), while randomizing incident polarization 45° from principle axes (m33 = –0.05). These reflectance properties allow lookdowns to reflect the uniform degree and angle of polarization associated with high-noon conditions due to alignment of the principle axes and the sun, and reflect a more complex polarization pattern at asymmetrical light fields associated with lower solar elevations. Our results suggest that polaro–cryptic strategies vary by habitat, and require context-specific depolarization and angle alteration for effective concealment in the complex open ocean environment. PMID:23716701

The Role of External Inputs and Internal Cycling in Shaping the Global Ocean Cobalt Distribution: Insights From the First Cobalt Biogeochemical Model

NASA Astrophysics Data System (ADS)

Tagliabue, Alessandro; Hawco, Nicholas J.; Bundy, Randelle M.; Landing, William M.; Milne, Angela; Morton, Peter L.; Saito, Mak A.

2018-04-01

Cobalt is an important micronutrient for ocean microbes as it is present in vitamin B12 and is a co-factor in various metalloenzymes that catalyze cellular processes. Moreover, when seawater availability of cobalt is compared to biological demands, cobalt emerges as being depleted in seawater, pointing to a potentially important limiting role. To properly account for the potential biological role for cobalt, there is therefore a need to understand the processes driving the biogeochemical cycling of cobalt and, in particular, the balance between external inputs and internal cycling. To do so, we developed the first cobalt model within a state-of-the-art three-dimensional global ocean biogeochemical model. Overall, our model does a good job in reproducing measurements with a correlation coefficient of >0.7 in the surface and >0.5 at depth. We find that continental margins are the dominant source of cobalt, with a crucial role played by supply under low bottom-water oxygen conditions. The basin-scale distribution of cobalt supplied from margins is facilitated by the activity of manganese-oxidizing bacteria being suppressed under low oxygen and low temperatures, which extends the residence time of cobalt. Overall, we find a residence time of 7 and 250 years in the upper 250 m and global ocean, respectively. Importantly, we find that the dominant internal resupply process switches from regeneration and recycling of particulate cobalt to dissolution of scavenged cobalt between the upper ocean and the ocean interior. Our model highlights key regions of the ocean where biological activity may be most sensitive to cobalt availability.

Global and Regional Axial Ocean Angular Momentum Signals and Length-of-day Variations (1985-1996)

NASA Technical Reports Server (NTRS)

Ponte, Rui M.; Stammer, Detlef

2000-01-01

Changes in ocean angular momentum M about the polar axis are related to fluctuations in zonal currents (relative component M(sub tau) and latitudinal shifts in mass (planetary component M(sub Omega). Output from a 1 deg. ocean model is used to calculate global M(sub tau), (sub Omega), and M time series at 5 day intervals for the period January 1985 to April 1996. The annual cycle in M(sub tau), M(sub Omega), and M is larger than the semiannual cycle, and M(sub Omega) amplitudes are nearly twice those of M(sub tau). Year-to-year modulation of the seasonal cycle is present, but interannual variability is weak. The spectrum of M is red (background slope between omega(sup -1) and omega(sup -2) at sub-seasonal periods, implying a white or blue spectrum for the external torque on the ocean. Comparisons with previous studies indicate the importance of direct atmospheric forcing in inducing sub-seasonal M signals, relative to instabilities and other internal sources of rapid oceanic signals. Regional angular momentum estimates show that seasonal variability tends to be larger at low latitudes, but many local maxima exist because of the spatial structure of zonal current and mass variability. At seasonal timescales, latitudes approx. 20 deg. S - 10 deg. N contribute substantial variability to M(sub Omega), while signals in M(sub tau) can be traced to Antarctic Circumpolar Current transports and associated circulation. Variability in M is found to be small when compared with similar time series for the atmosphere and the solid Earth, but ocean signals are significantly coherent with atmosphere-solid Earth residuals, implying a measurable oceanic impact on length-of-day variations.

Global and Regional Axial Ocean Angular Momentum Signals and Length-of-Day Variations (1985-1996)

NASA Technical Reports Server (NTRS)

Ponte, Rui M.; Stammer, Detlef

1999-01-01

Changes in ocean angular momentum about the polar axis (M) are related to fluctuations in zonal currents (relative component M(sub r)) and latitudinal shifts in mass (planetary component M(sub Omega)). Output from a 1 deg ocean model is used to calculate global M(sub r), M(sub Omega), and M time series at 5-day intervals for the period January 1985-April 1996. The annual cycle in M(sub r), M(sub Omega), and M is larger than the semiannual cycle, and M(sub Omega) amplitudes are nearly twice those of M(sub r). Year-to-year modulation of the seasonal cycle is present, but interannual variability is weak. The spectrum of M is red (background slope between omega(sup (-1) and omega(sup -2)) at subseasonal periods, implying a white or blue spectrum for the external torque on the ocean. Comparisons with previous studies indicate the importance of direct atmospheric forcing in inducing subseasonal M signals, relative to instabilities and other internal sources of rapid oceanic signals. Regional angular momentum estimates show that seasonal variability tends to be larger at low latitudes but there are many local maxima due to the spatial structure of zonal current and mass variability. At seasonal timescales, latitudes approximately 20 S - 10 N contribute substantial variability to M(sub Omega), while signals in M(sub r) can be traced to Antarctic Circumpolar Current transports and associated circulation. Variability in M is found to be small when compared with similar time series for the atmosphere and the solid Earth, but ocean signals are significantly coherent with atmosphere-solid Earth residuals, implying a measurable oceanic impact on length-of-day variations.

Indian Ocean Surface Circulations and Their Connection to Indian Ocean Dipole, Identified From Ocean Surface Currents Analysis Real Time (OSCAR) Data

DTIC Science & Technology

2008-06-01

31 1. Seasonal Development .......................................................................32 2. Winter Monsoon...summary of the monsoon system in the Indian Ocean. The top part indicates the wind cycle; the lower part shows the major currents that develop in...energy interests in the Indian Ocean’s waters. The rapid economic progress in developing nations, such as India and South Africa, also adds up their

Ocean salinities reveal strong global water cycle intensification during 1950 to 2000.

PubMed

Durack, Paul J; Wijffels, Susan E; Matear, Richard J

2012-04-27

Fundamental thermodynamics and climate models suggest that dry regions will become drier and wet regions will become wetter in response to warming. Efforts to detect this long-term response in sparse surface observations of rainfall and evaporation remain ambiguous. We show that ocean salinity patterns express an identifiable fingerprint of an intensifying water cycle. Our 50-year observed global surface salinity changes, combined with changes from global climate models, present robust evidence of an intensified global water cycle at a rate of 8 ± 5% per degree of surface warming. This rate is double the response projected by current-generation climate models and suggests that a substantial (16 to 24%) intensification of the global water cycle will occur in a future 2° to 3° warmer world.

Evidence for microbial carbon and sulfur cycling in deeply buried ridge flank basalt

USGS Publications Warehouse

Lever, Mark A.; Rouxel, Olivier; Alt, Jeffrey C.; Shimizu, Nobumichi; Ono, Shuhei; Coggon, Rosalind M.; Shanks, Wayne C.; Lapham, Laura; Elvert, Marcus; Prieto-Mollar, Xavier; Hinrichs, Kai-Uwe; Inagaki, Fumio; Teske, Andreas

2013-01-01

Sediment-covered basalt on the flanks of mid-ocean ridges constitutes most of Earth's oceanic crust, but the composition and metabolic function of its microbial ecosystem are largely unknown. By drilling into 3.5-million-year-old subseafloor basalt, we demonstrated the presence of methane- and sulfur-cycling microbes on the eastern flank of the Juan de Fuca Ridge. Depth horizons with functional genes indicative of methane-cycling and sulfate-reducing microorganisms are enriched in solid-phase sulfur and total organic carbon, host δ13C- and δ34S-isotopic values with a biological imprint, and show clear signs of microbial activity when incubated in the laboratory. Downcore changes in carbon and sulfur cycling show discrete geochemical intervals with chemoautotrophic δ13C signatures locally attenuated by heterotrophic metabolism.

Integrated Assessment of Carbon Dioxide Removal

NASA Astrophysics Data System (ADS)

Rickels, W.; Reith, F.; Keller, D.; Oschlies, A.; Quaas, M. F.

2018-03-01

To maintain the chance of keeping the average global temperature increase below 2°C and to limit long-term climate change, removing carbon dioxide from the atmosphere (carbon dioxide removal, CDR) is becoming increasingly necessary. We analyze optimal and cost-effective climate policies in the dynamic integrated assessment model (IAM) of climate and the economy (DICE2016R) and investigate (1) the utilization of (ocean) CDR under different climate objectives, (2) the sensitivity of policies with respect to carbon cycle feedbacks, and (3) how well carbon cycle feedbacks are captured in the carbon cycle models used in state-of-the-art IAMs. Overall, the carbon cycle model in DICE2016R shows clear improvements compared to its predecessor, DICE2013R, capturing much better long-term dynamics and also oceanic carbon outgassing due to excess oceanic storage of carbon from CDR. However, this comes at the cost of a (too) tight short-term remaining emission budget, limiting the model suitability to analyze low-emission scenarios accurately. With DICE2016R, the compliance with the 2°C goal is no longer feasible without negative emissions via CDR. Overall, the optimal amount of CDR has to take into account (1) the emission substitution effect and (2) compensation for carbon cycle feedbacks.

Enhanced Arctic Amplification Began at the Mid-Brunhes Event ~400,000 years ago.

PubMed

Cronin, T M; Dwyer, G S; Caverly, E K; Farmer, J; DeNinno, L H; Rodriguez-Lazaro, J; Gemery, L

2017-11-03

Arctic Ocean temperatures influence ecosystems, sea ice, species diversity, biogeochemical cycling, seafloor methane stability, deep-sea circulation, and CO 2 cycling. Today's Arctic Ocean and surrounding regions are undergoing climatic changes often attributed to "Arctic amplification" - that is, amplified warming in Arctic regions due to sea-ice loss and other processes, relative to global mean temperature. However, the long-term evolution of Arctic amplification is poorly constrained due to lack of continuous sediment proxy records of Arctic Ocean temperature, sea ice cover and circulation. Here we present reconstructions of Arctic Ocean intermediate depth water (AIW) temperatures and sea-ice cover spanning the last ~ 1.5 million years (Ma) of orbitally-paced glacial/interglacial cycles (GIC). Using Mg/Ca paleothermometry of the ostracode Krithe and sea-ice planktic and benthic indicator species, we suggest that the Mid-Brunhes Event (MBE), a major climate transition ~ 400-350 ka, involved fundamental changes in AIW temperature and sea-ice variability. Enhanced Arctic amplification at the MBE suggests a major climate threshold was reached at ~ 400 ka involving Atlantic Meridional Overturning Circulation (AMOC), inflowing warm Atlantic Layer water, ice sheet, sea-ice and ice-shelf feedbacks, and sensitivity to higher post-MBE interglacial CO 2 concentrations.

Dominance of Epsilonproteobacteria associated with a whale fall at a 4204 m depth - South Atlantic Ocean

NASA Astrophysics Data System (ADS)

Cavalett, Angélica; Silva, Marcus Adonai Castro da; Toyofuku, Takashi; Mendes, Rodrigo; Taketani, Rodrigo Gouvêa; Pedrini, Jéssica; Freitas, Robert Cardoso de; Sumida, Paulo Yukio Gomes; Yamanaka, Toshiro; Nagano, Yuriko; Pellizari, Vivian Helena; Perez, José Angel Alvarez; Kitazato, Hiroshi; Lima, André Oliveira de Souza

2017-12-01

The deep ocean is the largest marine environment on Earth and is home to a large reservoir of biodiversity. Within the deep ocean, large organic falls attract a suite of metazoans and microorganisms, which form an important community that, in part, relies on reduced chemical compounds. Here, we describe a deep-sea (4204 m) microbial community associated with sediments collected underneath a whale fall skeleton in the South Atlantic Ocean. Metagenomic analysis of 1 Gb of Illumina HiSeq. 2000 reads, including taxonomic and functional genes, was performed by using the MG-RAST pipeline, SEED, COG and the KEGG database. The results showed that Proteobacteria (79%) was the main phylum represented. The most dominant bacterial class in this phylum was Epsilonproteobacteria (69%), and Sulfurovum sp. NBC37-1 (97%) was the dominant species. Different species of Epsilonproteobacteria have been described in marine and terrestrial environments as important organisms for nutrient cycling. Functional analysis revealed key genes for nitrogen and sulfur cycles, including protein sequences for Sox system (sulfur oxidation) enzymes. These enzymes were mainly those of the Epsilonproteobacteria, indicating their importance for nitrogen and sulfur cycles and the balance of nutrients in this environment.

Iron control on global productivity: an efficient inverse model of the ocean's coupled phosphate and iron cycles.

NASA Astrophysics Data System (ADS)

Pasquier, B.; Holzer, M.; Frants, M.

2016-02-01

We construct a data-constrained mechanistic inverse model of the ocean's coupled phosphorus and iron cycles. The nutrient cycling is embedded in a data-assimilated steady global circulation. Biological nutrient uptake is parameterized in terms of nutrient, light, and temperature limitations on growth for two classes of phytoplankton that are not transported explicitly. A matrix formulation of the discretized nutrient tracer equations allows for efficient numerical solutions, which facilitates the objective optimization of the key biogeochemical parameters. The optimization minimizes the misfit between the modelled and observed nutrient fields of the current climate. We systematically assess the nonlinear response of the biological pump to changes in the aeolian iron supply for a variety of scenarios. Specifically, Green-function techniques are employed to quantify in detail the pathways and timescales with which those perturbations are propagated throughout the world oceans, determining the global teleconnections that mediate the response of the global ocean ecosystem. We confirm previous findings from idealized studies that increased iron fertilization decreases biological production in the subtropical gyres and we quantify the counterintuitive and asymmetric response of global productivity to increases and decreases in the aeolian iron supply.

Uranium isotope evidence for two episodes of deoxygenation during Oceanic Anoxic Event 2

NASA Astrophysics Data System (ADS)

Clarkson, Matthew O.; Stirling, Claudine H.; Jenkyns, Hugh C.; Dickson, Alexander J.; Porcelli, Don; Moy, Christopher M.; Pogge von Strandmann, Philip A. E.; Cooke, Ilsa R.; Lenton, Timothy M.

2018-03-01

Oceanic Anoxic Event 2 (OAE 2), occurring ˜94 million years ago, was one of the most extreme carbon cycle and climatic perturbations of the Phanerozoic Eon. It was typified by a rapid rise in atmospheric CO2, global warming, and marine anoxia, leading to the widespread devastation of marine ecosystems. However, the precise timing and extent to which oceanic anoxic conditions expanded during OAE 2 remains unresolved. We present a record of global ocean redox changes during OAE 2 using a combined geochemical and carbon cycle modeling approach. We utilize a continuous, high-resolution record of uranium isotopes in pelagic and platform carbonate sediments to quantify the global extent of seafloor anoxia during OAE 2. This dataset is then compared with a dynamic model of the coupled global carbon, phosphorus, and uranium cycles to test hypotheses for OAE 2 initiation. This unique approach highlights an intra-OAE complexity that has previously been underconstrained, characterized by two expansions of anoxia separated by an episode of globally significant reoxygenation coincident with the “Plenus Cold Event.” Each anoxic expansion event was likely driven by rapid atmospheric CO2 injections from multiphase Large Igneous Province activity.

Compiled records of carbon isotopes in atmospheric CO2 for historical simulations in CMIP6

NASA Astrophysics Data System (ADS)

Graven, Heather; Allison, Colin E.; Etheridge, David M.; Hammer, Samuel; Keeling, Ralph F.; Levin, Ingeborg; Meijer, Harro A. J.; Rubino, Mauro; Tans, Pieter P.; Trudinger, Cathy M.; Vaughn, Bruce H.; White, James W. C.

2017-12-01

The isotopic composition of carbon (Δ14C and δ13C) in atmospheric CO2 and in oceanic and terrestrial carbon reservoirs is influenced by anthropogenic emissions and by natural carbon exchanges, which can respond to and drive changes in climate. Simulations of 14C and 13C in the ocean and terrestrial components of Earth system models (ESMs) present opportunities for model evaluation and for investigation of carbon cycling, including anthropogenic CO2 emissions and uptake. The use of carbon isotopes in novel evaluation of the ESMs' component ocean and terrestrial biosphere models and in new analyses of historical changes may improve predictions of future changes in the carbon cycle and climate system. We compile existing data to produce records of Δ14C and δ13C in atmospheric CO2 for the historical period 1850-2015. The primary motivation for this compilation is to provide the atmospheric boundary condition for historical simulations in the Coupled Model Intercomparison Project 6 (CMIP6) for models simulating carbon isotopes in the ocean or terrestrial biosphere. The data may also be useful for other carbon cycle modelling activities.

76 FR 27019 - Interagency Ocean Observation Committee, Meeting of the Data Management and Communications...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-10

... Observation Committee, Meeting of the Data Management and Communications Steering Team AGENCY: National Ocean...). ACTION: Notice of open meeting. SUMMARY: NOAA's Integrated Ocean Observing System (IOOS) Program... meeting of the IOOC's Data Management and Communications Steering Team (DMAC-ST). The DMAC-ST membership...

78 FR 46932 - Meeting of the Ocean Research Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-02

... DEPARTMENT OF DEFENSE Department of the Navy Meeting of the Ocean Research Advisory Panel AGENCY: Department of the Navy, DoD. ACTION: Notice of open meeting. SUMMARY: The Ocean Research Advisory Panel (ORAP..., Office of Naval Research, 875 North Randolph Street, Suite 1425, Arlington, VA 22203- 1995, telephone 703...

PCDDs, PCDFs, and coplanar PCBs in albatross from the North Pacific and Southern Oceans: levels, patterns, and toxicological implications.

PubMed

Tanabe, Shinsuke; Watanabe, Mafumi; Minh, Tu Binh; Kunisue, Tatsuya; Nakanishi, Shigeyuki; Ono, Hitoshi; Tanaka, Hiroyuki

2004-01-15

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (coplanar PCBs) were determined in five albatross species collected from the North Pacific and Southern Oceans to assess the north-south differences in residue levels, accumulation patterns, and toxic potential. Black-footed and Laysan albatrosses from the North Pacific Ocean contained higher levels of PCDD/Fs and coplanar PCBs than albatrosses from the Southern Ocean, indicating that emission sources of these contaminants were predominant in the northern hemisphere. Residue levels in albatrosses from the remote North Pacific Ocean far from the point source of pollution were comparable to or higher than those in terrestrial and coastal birds from contaminated areas in developed nations, suggesting the specific exposure and accumulation of PCDD/Fs and coplanar PCBs in albatross. The long life span and ingestion of plastic resin pellets by albatrosses could be the plausible explanations for the elevated accumulation of persistent and lipophilic contaminants including PCDD/Fs and coplanar PCBs in these birds. Relative proportions of PCDFs and coplanar PCBs in albatross were higher than those observed in birds inhabiting terrestrial and coastal areas, suggesting that these toxic chemicals may have higher transportability by air and water than PCDDs. Congener patterns of PCDD/Fs in albatross showed less variability as compared to those in terrestrial species, indicating that contamination patterns of PCDD/Fs were similar within the open ocean environment. Contributions of PCDD/Fs to total TEQs in albatrosses from the open ocean were generally lower than those in terrestrial birds, suggesting different toxic potency of PCDD/Fs and coplanar PCBs on animals inhabiting open ocean and terrestrial environment. Whereas albatrosses from southern oceans retained lower TEQ concentrations, possible adverse effects of PCDD/Fs and coplanar PCBs to black-footed and Laysan albatrosses of the North Pacific Ocean may be suspected from TEQ levels.

Skipjack tuna as a bioindicator of contamination by perfluorinated compounds in the oceans.

PubMed

Hart, Kimberly; Kannan, Kurunthachalam; Tao, Lin; Takahashi, Shin; Tanabe, Shinsuke

2008-09-15

Perfluorinated chemicals (PFCs) have emerged as global environmental contaminants. Studies have reported the widespread occurrence of PFCs in biota from marine coastal waters and in remote polar regions. However, few studies have reported the distribution of PFCs in biota from offshore waters and open oceans. In this study, concentrations of nine PFCs were determined in the livers of 60 skipjack tuna (Katsuwonus pelamis) collected from offshore waters and the open ocean along the Pacific Rim, including the Sea of Japan, the East China Sea, the Indian Ocean, and the Western North Pacific Ocean, during 1997-1999. At least one of the nine PFCs was found in every tuna sample analyzed. Overall, perfluorooctanesulfonate (PFOS) and perfluoroundecanoic acid (PFUnDA) were the predominant compounds found in livers of tuna at concentrations of <1-58.9 and <1-31.6 ng/g, wet wt, respectively. Long-chain perfluorocarboxylates such as perfluorodecanoic acid (PFDA) and perfluorododecanoic acid (PFDoDA) were common in the tuna livers. In livers of tuna from several offshore and open-ocean locations, concentrations of PFUnDA were greater than the concentrations of PFOS. The profiles and concentrations of PFCs in tuna livers suggest that the sources in East Asia are dominated by long-chain perfluorocarboxylates, especially PFUnDA. High concentrations of PFUnDA in tuna may indicate a shift in sources of PFCs in East Asia. The spatial distribution of PFOS in skipjack tuna reflected the concentrations previously reported in seawater samples from the Pacific and Indian Oceans, suggesting that tuna are good bioindicators of pollution by PFOS. Despite its predominance in ocean waters, PFOA was rarely found in tuna livers, indicative of the low bioaccumulation potential of this compound. Our study establishes baseline concentrations of PFCs in skipjack tuna from the oceans of the Asia-Pacific region, enabling future temporal trend studies of PFCs in oceans.

Impacts of atmospheric anthropogenic nitrogen on the open ocean.

PubMed

Duce, R A; LaRoche, J; Altieri, K; Arrigo, K R; Baker, A R; Capone, D G; Cornell, S; Dentener, F; Galloway, J; Ganeshram, R S; Geider, R J; Jickells, T; Kuypers, M M; Langlois, R; Liss, P S; Liu, S M; Middelburg, J J; Moore, C M; Nickovic, S; Oschlies, A; Pedersen, T; Prospero, J; Schlitzer, R; Seitzinger, S; Sorensen, L L; Uematsu, M; Ulloa, O; Voss, M; Ward, B; Zamora, L

2008-05-16

Increasing quantities of atmospheric anthropogenic fixed nitrogen entering the open ocean could account for up to about a third of the ocean's external (nonrecycled) nitrogen supply and up to approximately 3% of the annual new marine biological production, approximately 0.3 petagram of carbon per year. This input could account for the production of up to approximately 1.6 teragrams of nitrous oxide (N2O) per year. Although approximately 10% of the ocean's drawdown of atmospheric anthropogenic carbon dioxide may result from this atmospheric nitrogen fertilization, leading to a decrease in radiative forcing, up to about two-thirds of this amount may be offset by the increase in N2O emissions. The effects of increasing atmospheric nitrogen deposition are expected to continue to grow in the future.

Tracing Carbon Cycling in the Atmosphere and Oceans During the Cretaceous Ocean Anoxic Event 2 (OAE2, 94Ma)

NASA Astrophysics Data System (ADS)

Moran, S. A. M.; Boudinot, F. G.; Dildar, N.; Sepúlveda, J.

2017-12-01

We present a high-resolution record of compound-specific stable carbon isotope data from short-chain—aquatic algae—and long-chain n-alkanes—terrestrial plants—preserved in sedimentary sequences from the Smokey Hollow #1 (SH1) core in the Grand Staircase Escalante National Monument in southern Utah. The study area covered by SH1 core was situated at the western margin of the Western Interior Seaway during the Cretaceous Ocean Anoxic Event (OAE2, 94Ma.), and was characterized by high sedimentation rates and enhanced preservation of both marine and terrestrial organic matter. Short- and long-chain n-alkanes were isolated and purified from branched and cyclic aliphatic hydrocarbons using an optimized urea adduction protocol, and δ13Cn-alkane was measured using a Thermo MAT253 GC-C-IR-MS. We use the δ13Cn-alkane from aquatic and terrestrial sources to better understand carbon cycle interactions in the oceanic and atmospheric carbon pools across this event. Our results indicate that the δ13C of terrestrial plants experienced a faster and more pronounced positive carbon isotope excursion compared to marine sources. We will discuss how these results can inform models of carbon cycle interactions between the ocean and the atmosphere during greenhouse climates, and how they can be used to trace possible sources of CO2.