Global sea-surface iodide observations, 1967-2018

The marine iodine cycle has significant impacts on air quality and atmospheric chemistry. Specifically, the reaction of iodide with ozone in the top few micrometres of the surface ocean is an important sink for tropospheric ozone (a pollutant gas) and the dominant source of reactive iodine to the atmosphere. Sea surface iodide parameterisations are now being implemented in air quality models, but these are currently a major source of uncertainty. Relatively little observational data is available to estimate the global surface iodide concentrations, and this data has not hitherto been openly available in a collated, digital form. Here we present all available sea surface (<20 m depth) iodide observations. The dataset includes values digitised from published manuscripts, published and unpublished data supplied directly by the originators, and data obtained from repositories. It contains 1342 data points, and spans latitudes from 70°S to 68°N, representing all major basins. The data may be used to model sea surface iodide concentrations or as a reference for future observations

Hydrographic and biological changes in the Taiwan Strait during the 1997-1998 El Nino winter

During the 1997 - 1998 El Nino event, the average sea surface temperature (SST) in the Taiwan Strait (TWS) in the winter was similar to 1.4 degrees C higher than that of the winter climatological mean. The areal ratio of the warm water ( >= 2 degrees C above the regional mean) to the cold water ( >= 2 degrees C below the regional mean) in the TWS increased by 25% while the area of the eutrophic water ( chlorophyll a > 1 mg m(-3)) was halved. Field observations also indicate that the mixed layer in the TWS became more nutrient-poor during this winter. These observations are consistent with a diminished advection of the cold and eutrophic Zhe-Min Coastal Water, and, concomitantly, an expansive intrusion of the warm and oligotrophic South China Sea Warm Current/ Kuroshio Branch Water to the TWS as the northeast monsoon was weakened. Thus, El Nino events potentially can have significant ecological impacts on the TWS

Speciation analysis of iodine and bromine at picogram-per-gram levels in polar ice

Iodine and bromine species participate in key atmospheric reactions including the formation of cloud con- densation nuclei and ozone depletion. We present a novel method coupling a high-performance liquid chromatogra- phy with ion chromatography and inductively coupled plas- ma mass spectrometry, which allows the determination of iodine (I) and bromine (Br) species (IO3−, I−, Br−, BrO3−) at the picogram-per-gram levels presents in Antarctic ice. Chromatographic separation was achieved using an ION- PAC® AS16 Analytical Column with NaOH as eluent. Detection limits for I and Br species were 5 to 9 pg g−1 with an uncertainty of less than 2.5% for all considered species. Inorganic iodine and bromine species have been determined in Antarctic ice core samples, with concentrations close to the detection limits for iodine species, and approximately 150 pg g−1 for Br−. Although iodate (IO3−) is the most abundant iodine species in the atmosphere, only the much rarer iodide (I−) species was present in Antarctic Holocene ice. Bromine was found to be present in Antarctic ice as Br−

Hydrography and nutrient dynamics in the Northern South China Sea-shelf (NoSoCS)

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The decomposition of hydrogen peroxide by marine phytoplankton

All nine species of marine phytoplankton tested (a cyanobacterium: Synechococcus sp., three diatoms: Chaetoceros simplex, Thalassiosira oceanica and Skeletonema costatum, two prymnesiophytes: Pleurochrysis carterae and Isochrysis galbana, a prasinophyte: Tetraselmis sp., a green alga: Dunaliella tertiolecta, and a dinoflagellate: Amphidinium carterae) were able to decompose hydrogen peroxide in the dark. Since these phytoplankton species can be found widely in a variety of marine sub-environments, this indicates that the dark decomposition of hydrogen peroxide by phytoplankton is a general phenomenon in the oceans. The decomposition rates were first order with respect to the concentration of hydrogen peroxide and biomass. The second-order rate constants for these nine species of phytoplankton ranged between 2 x 10(-4) and 2.7 x 10(-2) mug Chl-a(-1) 1 h(-1). Synechococcus sp. and S. costatum were the most efficient, while P. carterae and D. tertiolecta were the least efficient decomposers. While the magnitudes and patterns in the changes were species-dependent, in general, increasing salinity, temperature, the presence of light and the depletion of nutrients enhanced the decomposition of hydrogen peroxide. The effect of growth phase was small.L'ensemble formé par cinq espèces océaniques (une cyanobactérie : Synechococcus sp.; deux diatomées : Chaetoceros simplex et Thalassiosira oceanica, et deux prymnésiophytes : Pleurochrysis carterae et Isochrysis galbana) et quatre espèces côtières (une prasinophyte : Tetraselmis sp.; une algue bleue : Dunaliella tertiolecta; une diatomée : Skeletonema costatum et un dinoflagellé : Amphidinium carterae) de phytoplancton testées sont capables de décomposer le peroxyde d'hydrogène à l'obscurité. Ces espèces sont ubiquistes, ce qui montre que la décomposition à l'obscurité du peroxyde d'hydrogène est un phénomène répandu. Les taux de décomposition vont de 2,0 × 10–4 et 2,7 × 10–2 μg Chl-a–1 1 h–1. Synechococcus sp. et S. costatum sont les décomposeurs les plus efficaces tandis que P. carterae et D. tertiolecta le sont le moins. L'aptitude à la décomposition du peroxyde d'hydrogène est affectée par les modifications physiques et chimiques de l'environnement et des facteurs biologiques. Un accroissement de la salinité et de la température, la présence de lumière et l'épuisement des sels nutritifs rehausse cette décomposition. L'effet de la phase de croissance est léger. L'importance et la nature de ces changements en fonction des modifications de l'environnement varie d'une espèce à l'autre

Climate modulates internal wave activity in the Northern South China Sea

Internal waves (IWs) generated in the Luzon Strait propagate into the Northern South China Sea (NSCS), enhancing biological productivity and affecting coral reefs by modulating nutrient concentrations and temperature. Here we use a state-of-the-art ocean data assimilation system to reconstruct water column stratification in the Luzon Strait as a proxy for IW activity in the NSCS and diagnose mechanisms for its variability. Interannual variability of stratification is driven by intrusions of the Kuroshio Current into the Luzon Strait and freshwater fluxes associated with the El Niño-Southern Oscillation. Warming in the upper 100m of the ocean caused a trend of increasing IW activity since 1900, consistent with global climate model experiments that show stratification in the Luzon Strait increases in response to radiative forcing. IW activity is expected to increase in the NSCS through the 21st century, with implications for mitigating climate change impacts on coastal ecosystems