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  • 1
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    Tectonic control over large-scale diffuse degassing in eastern Sicily (Italy) (2005)
    Blackwell Science Ltd
    Details
    Publication Date: 2017-04-04
    Description: Eastern Sicily (southern Italy) is characterised by the presence of many natural gas emissions (mofettes, mud volcanoes). These gases are mostly carbon dioxide and methane, with minor amounts of helium, hydrogen, carbon monoxide and hydrocarbons. In this study, the extent and orientation of soil gas anomalies (He and CO2) were investigated on a wide area (approximately 110 km2) located just SW of Mt. Etna. From a structural point of view, this area lays on a typical foredeep–foreland system that marks the boundary between the southern part of the Eurasian plate and the northern part of the African plate in the central Mediterranean. No tectonic structure was revealed in this area by surface geological surveys. Very high soil emissions were found, and their spatial pattern reveals the existence of some active faults all directed about N508E. This direction coincides with that of two major fault systems that cut eastern Sicily and are evident, respectively, NE and SW of the study area. Soil gas data suggest that these fault systems are the expression of a single continuous structural line which is probably responsible for the past and present magma uprise in eastern Sicily. Isotopic values of carbon of CO2 suggest a minor contribution of organic carbon. Moreover, in the highest degassing sites the isotopic values of He found in association with CO2 (He abundance¼11–70 p.p.m.; R/Ra between 6.0 and 6.2) suggest that both gases are mantle derived. The extent of the areas affected by high gas emissions and the amounts of deep CO2 emitted in the investigated area (several hundred tonnes per day) may provide additional supporting evidence of a mantle upwelling taking place beneath this region.
    Description: Gruppo Nazionale per la Vulcanologia Italy.
    Description: Published
    Description: 273–284
    Description: partially_open
    Keywords: CO2 ; diffuse degassing ; Sicily ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Inorganic carbon system dynamics in landfast Arctic sea ice during the early-melt period (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 120 (2015): 3542-3566, doi:10.1002/2014JC010620.
    Description: We present the results of a 6 week time series of carbonate system and stable isotope measurements investigating the effects of sea ice on air-sea CO2 exchange during the early melt period in the Canadian Arctic Archipelago. Our observations revealed significant changes in sea ice and sackhole brine carbonate system parameters that were associated with increasing temperatures and the buildup of chlorophyll a in bottom ice. The warming sea-ice column could be separated into distinct geochemical zones where biotic and abiotic processes exerted different influences on inorganic carbon and pCO2 distributions. In the bottom ice, biological carbon uptake maintained undersaturated pCO2 conditions throughout the time series, while pCO2 was supersaturated in the upper ice. Low CO2 permeability of the sea ice matrix and snow cover effectively impeded CO2 efflux to the atmosphere, despite a strong pCO2 gradient. Throughout the middle of the ice column, brine pCO2 decreased significantly with time and was tightly controlled by solubility, as sea ice temperature and in situ melt dilution increased. Once the influence of melt dilution was accounted for, both CaCO3 dissolution and seawater mixing were found to contribute alkalinity and dissolved inorganic carbon to brines, with the CaCO3 contribution driving brine pCO2 to values lower than predicted from melt-water dilution alone. This field study reveals a dynamic carbon system within the rapidly warming sea ice, prior to snow melt. We suggest that the early spring period drives the ice column toward pCO2 undersaturation, contributing to a weak atmospheric CO2 sink as the melt period advances.
    Description: We acknowledge support from the Polar Continental Shelf Program (PCSP) of Natural Resources Canada, the Natural Sciences and Engineering Research Council of Canada, the Northern Scientific Training Program, Canada Economic Development, and Fisheries and Oceans Canada.
    Description: 2015-11-19
    Keywords: Sea ice ; Carbon cycling ; CO2 ; Brines ; Stable isotopes ; Arctic Ocean
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Sea surface pCO2 and O2 dynamics in the partially ice-covered Arctic Ocean (2017)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 1425–1438, doi:10.1002/2016JC012162.
    Description: Understanding the physical and biogeochemical processes that control CO2 and dissolved oxygen (DO) dynamics in the Arctic Ocean (AO) is crucial for predicting future air-sea CO2 fluxes and ocean acidification. Past studies have primarily been conducted on the AO continental shelves during low-ice periods and we lack information on gas dynamics in the deep AO basins where ice typically inhibits contact with the atmosphere. To study these gas dynamics, in situ time-series data have been collected in the Canada Basin during late summer to autumn of 2012. Partial pressure of CO2 (pCO2), DO concentration, temperature, salinity, and chlorophyll-a fluorescence (Chl-a) were measured in the upper ocean in a range of sea ice states by two drifting instrument systems. Although the two systems were on average only 222 km apart, they experienced considerably different ice cover and external forcings during the 40–50 day periods when data were collected. The pCO2 levels at both locations were well below atmospheric saturation whereas DO was almost always slightly supersaturated. Modeling results suggest that air-sea gas exchange, net community production (NCP), and horizontal gradients were the main sources of pCO2 and DO variability in the sparsely ice-covered AO. In areas more densely covered by sea ice, horizontal gradients were the dominant source of variability, with no significant NCP in the surface mixed layer. If the AO reaches equilibrium with atmospheric CO2 as ice cover continues to decrease, aragonite saturation will drop from a present mean of 1.00 ± 0.02 to 0.86 ± 0.01.
    Description: U.S. National Science Foundation Arctic Observing Network Grant Number: ARC-1107346 and ARC-0856479
    Description: 2017-08-25
    Keywords: Arctic Ocean ; CO2 ; O2 ; Biogeochemistry ; Dynamics ; Carbon cycle
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Do Trichodesmium spp. populations in the North Atlantic export most of the nitrogen they fix? (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 28 (2014): 103-114, doi:10.1002/2013GB004652.
    Description: A new observational synthesis of diazotrophic biomass and nitrogen fixation provides the opportunity for systematic quantitative evaluation of these aspects in biogeochemical models. One such model of the Atlantic Ocean is scrutinized, and the simulated biomass is found to be an order of magnitude too low. Initial attempts to increase biomass levels through decreasing grazing and other loss terms caused an unrealistic buildup of nitrate in the upper ocean. Two key changes to the model structure facilitated a closer match to the observed biomass and nitrogen fixation rates: addition of a pathway for export of diazotrophically fixed organic material and uptake of inorganic nitrogen by the diazotroph population. These changes, along with a few other revisions to existing model parameterizations, facilitate more accurate simulation of basin-scale distributions of diazotrophic biomass, as well as mesoscale variations contained therein. The resulting solutions suggest that the Trichodesmium spp. populations of the North Atlantic export the vast majority of the nitrogen they fix, a finding that awaits assessment through direct observation.
    Description: Support of this research by the National Science Foundation and the National Aeronautics and Space Administration is gratefully acknowledged.
    Description: 2014-08-20
    Keywords: Trichodesmium ; Nitrogen fixation ; North Atlantic ; Eddies ; Modeling ; Export
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    IIOE-2 Cruise No.EP12-1, 15 April, 2017 - 03 May, 2017 Kochi, India - Goa, India. Dust induced Primary Productivity and N2 fixation experiments in the Arabian Sea. (2017)
    Physical Research Laboratory | Ahmedabad, India
    Details
    Publication Date: 2021-05-19
    Description: Oceans act as a major sink for anthropogenic CO2 through primary production. The Arabian Sea (area ~6.2 × 106 km2) covers only about 1% of the global ocean surface but contributes up to 5% of the global marine primary production, partly due to high influx of ‘new’ nitrogen via diazotrophic N2 fixation. Iron, whose main source in the ocean is atmospheric transport of dust, is an essential nutrient for sustaining N2 fixation. Despite being in the vicinity of the Thar desert on the east and the Arabia desert on the west, the Arabian Sea has been projected to be an HNLC (high nutrient low chlorophyll) region
    Description: Unpublished
    Keywords: IIOE-2 ; CO2 ; Primary production ; Sagar Sampada/FORV ; Nitrogen fixation
    Repository Name: AquaDocs
    Type: Report , Not Known
    Format: 6pp.
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  • 6
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    Metabolic balance of coastal Antarctic waters revealed by autonomous pCO2 and ΔO2/Ar measurements (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 41 (2014): 6803–6810, doi:10.1002/2014GL061266.
    Description: We use autonomous gas measurements to examine the metabolic balance (photosynthesis minus respiration) of coastal Antarctic waters during the spring/summer growth season. Our observations capture the development of a massive phytoplankton bloom and reveal striking variability in pCO2 and biological oxygen saturation (ΔO2/Ar) resulting from large shifts in community metabolism on time scales ranging from hours to weeks. Diel oscillations in surface gases are used to derive a high-resolution time series of net community production (NCP) that is consistent with 14C-based primary productivity estimates and with the observed seasonal evolution of phytoplankton biomass. A combination of physical mixing, grazing, and light availability appears to drive variability in coastal Antarctic NCP, leading to strong shifts between net autotrophy and heterotrophy on various time scales. Our approach provides insight into the metabolic responses of polar ocean ecosystems to environmental forcing and could be employed to autonomously detect climate-dependent changes in marine primary productivity.
    Description: This study was supported by funds from the U.S. National Science Foundation (OPP awards ANT-0823101, ANT-1043559, ANT-1043593, and ANT-1043532) as well as support for PDT and ECA from the National Science and Engineering Research Council of Canada.
    Description: 2015-04-03
    Keywords: Photosynthesis ; Respiration ; Net community production ; DO2/Ar ; CO2 ; Antarctica
    Repository Name: Woods Hole Open Access Server
    Type: Article
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