Simultaneous determination of dissolved organic carbon and total dissolved nitrogen in seawater by high temperature catalytic oxidation: conditions for precise shipboard measurements

Appropriate conditions have been achieved for the accurate, rapid, and highly precise shipboard simultaneous determination of dissolved organic carbon and total dissolved nitrogen in seawater by high temperature catalytic oxidation. A nitrogen-specific Antek 705D chemiluminescence detector and a CO₂-specific LiCor Li6252 IRGA have been coupled in-series with a Shimadzu TOC-5000 organic carbon analyser. Precision of both simultaneous measurements is ≤1.5%, i.e. ±1 μmol C l⁻¹ and ±0.3 μmol N l⁻¹, respectively. Quality of analysis is not compromised by vibrations associated with ocean going research vessels.     

Effect of upward internal flow on dynamics of riser model subject to shear current

Numerical study about vortex-induced vibration(VIV) related to a flexible riser model in consideration of internal flow progressing inside has been performed.The main objective of this work is to investigate the coupled fluid-structure interaction(FSI) taking place between tensioned riser model,external shear current and upward-progressing internal flow(from ocean bottom to surface).A CAE technology behind the current research which combines structural software with the CFD technology has been proposed.According to the result from dynamic analysis,it has been found that the existence of upward-progressing internal flow does play an important role in determining the vibration mode(/dominant frequency),vibration intensity and the magnitude of instantaneous vibration amplitude,when the velocity ratio of internal flow against external current is relatively high.As a rule,the larger the velocity of internal flow is,the more it contributes to the dynamic vibration response of the flexible riser model.In addition,multi-modal vibration phenomenon has been widely observed,for asymmetric curvature along the riser span emerges in the case of external shear current being imposed.     

Effect of skewness and kurtosis of sea-surface elevations on the accuracy of altimetry surface level measurements

We assess the influence of changes in the skewness and kurtosis of the distribution of elevations on a rough sea surface that were observed in field conditions on the accuracy of the recovery of the sea-surface level along the satellite trace. For different values of a significant height of surface waves, we obtain numerical estimates for the bias in relief recovery due to the simultaneous variation in skewness and kurtosis. It is shown that, with a decrease in kurtosis, the effect of skewness changes on the accuracy of altimetry measurements of the level increases. We note the limitations of the Gram-Charlier model in simulating the radar waveforms return from the sea surface.     

Seasonal dynamics and Trophic interactions of phytoplankton and zooplankton in the Vistula Lagoon of the Baltic Sea

The trophic relationships of the phytoplankton and zooplankton in the Vistula Lagoon in 2008?C2010 were investigated. In the current period, the lagoon is an eutrophic water body with summer blooms of blue-green algae. The trophic level of the Vistula Lagoon influences both the composition and quantitative characteristics of the communities of phytoplankton and zooplankton and the trophic relationships between them. In the analyzed period, the consumption of phytoplankton by the zooplankton on the average in the growing season was 28%, which is 1.5 times higher than in the late 1970s. The high grazing pressure of the zooplankton on the phytoplankton reduces its biomass, production, and the intensity of the blooming by the blue-green algae in the Vistula Lagoon.     

Change in biochemical and morphological characteristics of Lonicera caerulea in tectonically active zone of the Dzhazator River Valley (Altai Mountains)

Local geophysical and geochemical anomalies affect the polymorphism of taste variations, berry shape, and content of some biologically active substances in Lonicera caerulea leaves in the tectonically active Altai Mountains (Dzhazator River basin).     

Modelling the long-term distribution of significant wave height with the Beta and Gamma models

The paper suggests modelling the long-term distribution of significant wave height with the Gamma, Beta of the first and second kind models. The three models are interrelated, flexible and cover the three different tail types of Extreme Value Theory. They can be used simultaneously as a means of assessing the uncertainty effects that result from choosing equally plausible models with different tail types. This procedure is intended for those applications that require the long-term distribution of significant wave height as input rather than the prediction of extreme values. The models are fitted to some significant wave data as an illustration. Details about maximum likelihood estimation are given in A.     

Studies of the European Arctic on Cruise 80 of the R/V Akademik Mstislav Keldysh

Oceanology - The multidisciplinary expedition “European Arctic-2020” on board the R/V Akademik Mstislav Keldysh took place from July 31 to August 26, 2020. The investigations were...     

Distribution and Origin of Hydrocarbons on a Transarctic Transect

The paper summarizes results on the content and composition of aliphatic hydrocarbons (HCs) in suspended particulate matter (SPM) and bottom sediments in the Kara, Laptev, and East Siberian seas obtained in 2015–2018. It was established that the “losses” in HC concentrations in surface waters in the river (Ob, Yenisei, Lena, Khatanga, Indigirka, Kolyma) and seawater mixing zone in some cases exceeded their river removal by 90%. The composition of HCs in surface waters depends on the characteristics of the river catchment area, sampling season. and time of day (high/low tide) and basically coincides with the SPM distribution. In the pelagic zone of the seas, the HC content is close to the background (2–7 μg/L). The influence of anthropogenic input was established only in the Gulf of Ob, where the composition of alkanes is close to oil with a HC content of 86 μg/mg SPM. In bottom sediments, the particle size distribution determines the HCs, and terrigenous n-alkanes play the dominant role in the molecular composition.

     

Two Modes of Atmosphere–Ocean Interaction in the Atlantic Sector of the Arctic Basin

Oceanology - The paper examines the influence of the main mode of interannual variability of the North Atlantic climate system—the North Atlantic Oscillation (NAO)—on the hydrophysical...     

Concentration and Isotopic and Elemental Composition of Organic Matter in Subsea Thawed and Permafrost Deposits of Buor-Khaya Bay

Oceanology - A comparative analysis of the content and composition of organic matter (OM) in samples of bottom sediments and subaqueous permafrost rocks by the concentration of organic carbon (OC),...