Impact of an artificial surfactant release on air-sea gas fluxes during Deep Ocean Gas Exchange Experiment II

Abstract. The isotopic composition of carbon, δ13C, in seawater is used in reconstructions of ocean circulation, marine productivity, air-sea gas exchange, and biosphere carbon storage. Here, a synthesis of δ13C measurements taken from foraminifera in marine sediment cores over the last 150 000 years is presented. The dataset comprises previously published and unpublished data from benthic and planktonic records throughout the global ocean. Data are placed on a common δ18O age scale suitable for examining orbital timescale variability but not millennial events, which are removed by a 10 ka filter. Error estimates account for the resolution and scatter of the original data, and uncertainty in the relationship between δ13C of calcite and of dissolved inorganic carbon (DIC) in seawater. This will assist comparison with δ13C of DIC output from models, which can be further improved using model outputs such as temperature, DIC concentration, and alkalinity to improve estimates of fractionation during calcite formation. High global deep ocean δ13C, indicating isotopically heavy carbon, is obtained during Marine Isotope Stages (MIS) 1, 3, 5a, c and e, and low δ13C during MIS 2, 4 and 6, which are temperature minima, with larger amplitude variability in the Atlantic Ocean than the Pacific Ocean. This is likely to result from changes in biosphere carbon storage, modulated by changes in ocean circulation, productivity, and air-sea gas exchange. The North Atlantic vertical δ13C gradient is greater during temperature minima than temperature maxima, attributed to changes in the spatial extent of Atlantic source waters. There are insufficient data from shallower than 2500 m to obtain a coherent pattern in other ocean basins. The data synthesis indicates that basin-scale δ13C during the last interglacial (MIS 5e) is not clearly distinguishable from the Holocene (MIS 1) or from MIS 5a and 5c, despite significant differences in ice volume and atmospheric CO2 concentration during these intervals. Similarly, MIS 6 is only distinguishable from MIS 2 or 4 due to globally lower δ13C values both in benthic and planktonic data. This result is obtained despite individual records showing differences between these intervals, indicating that care must be used in interpreting large scale signals from a small number of records.

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Dynamic C and N stocks – key factors controlling the C gas exchange of maize in a heterogenous peatland

Biogeosciences Discussions ◽

10.5194/bgd-11-16135-2014 ◽

2014 ◽

Vol 11 (11) ◽

pp. 16135-16176 ◽

Cited By ~ 1

Author(s):

M. Pohl ◽

M. Hoffmann ◽

U. Hagemann ◽

M. Giebels ◽

E. Albiac Borraz ◽

...

Keyword(s):

Gas Exchange ◽

Ecosystem Respiration ◽

Gross Primary Production ◽

Small Scale ◽

Organic Soils ◽

N Availability ◽

Soil System ◽

Gas Fluxes ◽

C And N ◽

Soc Stocks

Abstract. Drainage and cultivation of fen peatlands creates complex small-scale mosaics of soils with extremely variable soil organic carbon (SOC) stocks and groundwater-level (GWL). To date, it remains unclear if such sites are sources or sinks for greenhouse gases like CO2 and CH4, especially if used for cropland. As individual control factors like GWL fail to account for this complexity, holistic approaches combining gas fluxes with the underlying processes are required to understand the carbon (C) gas exchange of drained fens. It can be assumed that the stocks of SOC and N located above the variable GWL – defined as dynamic C and N stocks – play a key role in the regulation of plant- and microbially mediated C gas fluxes of these soils. To test this assumption, the present study analysed the C gas exchange (gross primary production – GPP, ecosystem respiration – Reco, net ecosystem exchange – NEE, CH4) of maize using manual chambers for four years. The study sites were located near Paulinenaue, Germany. Here we selected three soils, which represent the full gradient in pedogenesis, GWL and SOC stocks (0–1 m) of the fen peatland: (a) Haplic Arenosol (AR; 8 kg C m−2); (b) Mollic Gleysol (GL; 38 kg C m−2); and (c) Hemic Histosol (HS; 87 kg C m−2). Daily GWL data was used to calculate dynamic SOC (SOCdyn) and N (Ndyn) stocks. Average annual NEE differed considerably among sites, ranging from 47 ± 30 g C m−2 a−1 at AR to −305 ± 123 g C m−2 a−1 at GL and −127 ± 212 g C m−2 a−1 at HS. While static SOC and N stocks showed no significant effect on C fluxes, SOCdyn and Ndyn and their interaction with GWL strongly influenced the C gas exchange, particularly NEE and the GPP:Reco ratio. Moreover, based on nonlinear regression analysis, 86% of NEE variability was explained by GWL and SOCdyn. The observed high relevance of dynamic SOC and N stocks in the aerobic zone for plant and soil gas exchange likely originates from the effects of GWL-dependent N availability on C formation and transformation processes in the plant-soil system, which promote CO2 input via GPP more than CO2 emission via Reco. The process-oriented approach of dynamic C and N stocks is a promising, potentially generalizable method for system-oriented investigations of the C gas exchange of groundwater-influenced soils and could be expanded to other nutrients and soil characteristics. However, in order to assess the climate impact of arable sites on drained peatlands, it is always necessary to consider the entire range of groundwater-influenced mineral and organic soils and their respective areal extent within the soil landscape.

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Stomatal design principles in synthetic and real leaves

Journal of The Royal Society Interface ◽

10.1098/rsif.2016.0535 ◽

2016 ◽

Vol 13 (124) ◽

pp. 20160535 ◽

Cited By ~ 15

Author(s):

Maciej A. Zwieniecki ◽

Katrine S. Haaning ◽

C. Kevin Boyce ◽

Kaare H. Jensen

Keyword(s):

Gas Exchange ◽

Climate Science ◽

Design Principles ◽

Geometrical Properties ◽

Physical Mechanisms ◽

Gas Fluxes ◽

Wide Range ◽

Life On Earth ◽

Scientific Fields ◽

Stomatal Patterning

Stomata are portals in plant leaves that control gas exchange for photosynthesis, a process fundamental to life on Earth. Gas fluxes and plant productivity depend on external factors such as light, water and CO 2 availability and on the geometrical properties of the stoma pores. The link between stoma geometry and environmental factors has informed a wide range of scientific fields—from agriculture to climate science, where observed variations in stoma size and density are used to infer prehistoric atmospheric CO 2 content. However, the physical mechanisms and design principles responsible for major trends in stomatal patterning are not well understood. Here, we use a combination of biomimetic experiments and theory to rationalize the observed changes in stoma geometry. We show that the observed correlations between stoma size and density are consistent with the hypothesis that plants favour efficient use of space and maximum control of dynamic gas conductivity, and that the capacity for gas exchange in plants has remained constant over at least the last 325 Myr. Our analysis provides a new measure to gauge the relative performance of species based on their stomatal characteristics.

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A synthesis of marine sediment core δ<sup>13</sup>C data over the last 150 000 years

Climate of the Past Discussions ◽

10.5194/cpd-5-2497-2009 ◽

2009 ◽

Vol 5 (6) ◽

pp. 2497-2554 ◽

Cited By ~ 2

Author(s):

K. I. C. Oliver ◽

B. A. A. Hoogakker ◽

S. Crowhurst ◽

G. M. Henderson ◽

R. E. M. Rickaby ◽

...

Keyword(s):

Gas Exchange ◽

Carbon Storage ◽

Ocean Circulation ◽

Marine Sediment ◽

Large Scale ◽

Dissolved Inorganic Carbon ◽

Deep Ocean ◽

Global Ocean ◽

Last Interglacial ◽

Basin Scale

Abstract. The isotopic composition of carbon, δ13C, in seawater is used in reconstructions of ocean circulation, marine productivity, air-sea gas exchange, and biosphere carbon storage. Here, a synthesis of δ13C measurements taken from foraminifera in marine sediment cores over the last 150 000 years is presented. The dataset comprises previously published and unpublished data from benthic and planktonic records throughout the global ocean. Data are placed on a common δ18O age scale and filtered to remove timescales shorter than 6 kyr. Error estimates account for the resolution and scatter of the original data, and uncertainty in the relationship between δ13C of calcite and of dissolved inorganic carbon (DIC) in seawater. This will assist comparison with δ13C of DIC output from models, which can be further improved using model outputs such as temperature, DIC concentration, and alkalinity to improve estimates of fractionation during calcite formation. High global deep ocean δ13C, indicating isotopically heavy carbon, is obtained during Marine Isotope Stages (MIS) 1, 3, 5a, 5c and 5e, and low δ13C during MIS 2, 4 and 6, which are temperature minima, with larger amplitude variability in the Atlantic Ocean than the Pacific Ocean. This is likely to result from changes in biosphere carbon storage, modulated by changes in ocean circulation, productivity, and air-sea gas exchange. The North Atlantic vertical δ13C gradient is greater during temperature minima than temperature maxima, attributed to changes in the spatial extent of Atlantic source waters. There are insufficient data from shallower than 2500 m to obtain a coherent pattern in other ocean basins. The data synthesis indicates that basin-scale δ13C during the last interglacial (MIS 5e) is not clearly distinguishable from the Holocene (MIS 1) or from MIS 5a and 5c, despite significant differences in ice volume and atmospheric CO2 concentration during these intervals. Similarly, MIS 6 is only distinguishable from MIS 2 or 4 due to globally lower δ13C values both in benthic and planktonic data. This result is obtained despite individual records showing differences between these intervals, indicating that care must be used in interpreting large scale signals from a small number of records.

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Roles of leaf trichomes in heat transfers and gas‐exchange characteristics across environmental gradients

10.22541/au.160794364.42389606/v1 ◽

2020 ◽

Author(s):

Gaku Amada ◽

Yoshiko Kosugi ◽

Kanehiro Kitayama ◽

Yusuke Onoda

Keyword(s):

Gas Exchange ◽

Low Temperature ◽

Environmental Gradients ◽

Gas Diffusion ◽

Leaf Temperature ◽

Heat Diffusion ◽

Diffusion Resistance ◽

Leaf Trichomes ◽

Gas Fluxes ◽

Gas Exchange Characteristics

Dense leaf trichomes can directly decrease gas fluxes through increased gas diffusion resistance and indirectly increase gas fluxes through increased leaf temperature due to increased heat diffusion resistance, which may contribute to adaptation to dry and/or low‐temperature conditions. However, it remains unclear whether the leaf‐trichome resistance increases or decreases the gas‐exchange rates through combined direct and indirect effects. We focused on Metrosideros polymorpha, a dominant tree species inhabiting a large range of environmental gradients in the Hawaiian Islands, whose leaves have an enormous variation in trichome thickness on the lower surface. In five elevational sites, we measured leaf morphological and physiological traits including trichome thickness, gas‐exchange characteristics, and leaf temperature. The trichome thickness was largest in the coldest and driest site and thinnest at the wettest site. Leaf temperature was significantly increased with trichome thickness. With biophysical and physiological models, we show that leaf trichomes can increase the daily photosynthesis through increasing leaf temperature only in the cold alpine area. The daily water‐use efficiency can be lower with increasing leaf trichomes at any elevational sites. Therefore, in terms of diffusion resistance, the leaf trichomes of M. polymorpha can contribute to the adaptation to low‐temperature environments but not to dry environments.

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Gas Exchange and Bubble-Induced Supersaturation in a Wind-Wave Tank

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-1666.1 ◽

2004 ◽

Vol 21 (12) ◽

pp. 1925-1935 ◽

Cited By ~ 7

Author(s):

Peter Bowyer ◽

David Woolf

Keyword(s):

Steady State ◽

Gas Exchange ◽

Wind Wave ◽

Relative Strength ◽

Water Interface ◽

Wave Tank ◽

Gas Concentration ◽

Gas Fluxes ◽

Air Water Interface ◽

Series Of Experiments

Abstract Gas exchange and bubble-induced supersaturation were measured in a wind-wave tank using total gas saturation meters. The water in the tank was subjected to bubbling using a large number of frits at a depth of 0.6 m. A simple linear model of bubble-mediated gas exchange implies that this should force an equilibrium supersaturation of 3%. This is confirmed by experiment, but a small additional steady-state supersaturation is also forced by warming. The total steady-state supersaturation is approached asymptotically. When the bubblers were switched off, the total gas pressure approached a new steady state at much lower supersaturation, at a rate that depended on the state of the wind and waves in the tank. The rates of approach on the various equilibria enabled the gas flux across the surface of the bubbles or across the air–water interface to be calculated. In addition a series of experiments was conducted where the water was subjected to bubbling in the presence of wind or wind and paddle waves: in this case gas invasion from the bubbles was balanced by gas evasion near or at the surface resulting in an equilibrium at <3% and enabling the relative strength of the invasion and evasion to be estimated. Gas concentrations could be measured in a rapid, automated manner using simple apparatus. To derive gas fluxes, corrections for changes in water temperature and fluctuations in air pressure are necessary, and these are quantified. In addition, transient fluctuations in gas concentration at the start of bubbling periods allowed mixing within the tank to be observed.

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Direct measurements of biogenic dimethylsulphide fluxes from the oceans: a synthesis

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f04-047 ◽

2004 ◽

Vol 61 (5) ◽

pp. 836-844 ◽

Cited By ~ 8

Author(s):

H J Zemmelink ◽

J WH Dacey ◽

E J Hintsa

Keyword(s):

Gas Exchange ◽

Field Measurements ◽

Eddy Correlation ◽

Trace Gas ◽

Gas Transfer ◽

Transfer Rates ◽

Gas Fluxes ◽

Direct Measurements ◽

Powerful Approach ◽

Trace Gas Fluxes

This paper provides a brief overview of the state-of-the-art of techniques that are currently used for field measurements of trace gas fluxes and the subsequent derivation of gas transfer rates over the oceans. Special attention is given to the relaxed eddy accumulation (REA) and gradient flux (GF) techniques, which rely on empirical functions thus far mainly validated over land. The universality of these functions and their application at sea have not yet been fully evaluated. New experiments have shown that the emission of dimethylsulphide (DMS) can be measured by the REA and GF techniques. Moreover, these measurements have provided parameterizations of gas exchange rates that are within the range of relationships between wind speed and gas transfer that have recently been derived from eddy correlation (EC) and deliberate tracer measurements. Using DMS as a model, gas is potentially a powerful approach to intercalibrate the REA, GF, and EC techniques, test their applicability in the marine environment, and investigate processes that determine trace gas exchange across the ocean surface.

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