Nitrous oxide research progress in polar and sub-polar oceans

N2O gas depletes ozone and has a powerful greenhouse effect. Oceans are among the most important N2O sources and have been the subject of extensive studies. Polar oceans are important regions for deep water formation and global-scale thermohaline circulation. Therefore, these water bodies play an important role in the N2O budget, however, these regions were not well studied. This review of previously published studies and data on polar oceans, including both the Arctic Ocean and Southern Ocean, describes the distribution pattern of N2O and possible regulating mechanism of these distribution patterns and shows that the Arctic Ocean and Southern Ocean both represent source and sink regions, suggesting that the source/sink characteristics of the Arctic and Southern oceans and their strengths need further study. Questions related to N2O circulation in polar oceans were proposed, and future work is suggested

Concentration maxima of methane in the bottom waters over the Chukchi Sea shelf: implication of its biogenic source

Knowledge about the distribution of CH4 remains insufficient due to the scarcity of data in the Arctic shelves. We conducted shipboard observations over the Chukchi Sea shelf (CSS) in the western Arctic Ocean in September 2012 to obtain the distribution and source characteristics of dissolved CH4 in seawater. The oceanographic data indicated that a salinity gradient generated a pronounced pycnocline at depths of 20–30 m. The vertical diffusion of biogenic elements was restricted, and these elements were trapped in the bottom waters. Furthermore, high CH4 concentrations were measured below the pycnocline, and low CH4 concentrations were observed in the surface waters. The maximum concentrations of nutrients simultaneously occurred in the dense and cold bottom waters, and significant correlations were observed between CH4 and 2 3 SiO , 3 4 PO , 2 NO , and 4 NH (p < 0.01, n= 44). These results suggest that the production of CH4 in the CSS has a similar trend as that of nutrient regeneration and is probably associated with the degradation of organic matter. The high primary productivity and high concentration of organic matter support the formation of biogenic CH4 in the CSS and the subsequent release of CH4 to the water column

Multiple processes affecting surface seawater N2O saturation anomalies in tropical oceans and Prydz Bay, Antarctica

We analyzed the N2O content of surface seawater sampled from Prydz Bay, Antarctica, on a cruise track between 30°S and 30°N during the twenty-second Chinese National Antarctic Research Expedition during austral summer, 2006. The surface water showed an average pN2O value of 311.9±7.6 nL·L-1 (14.1±0.4 nmol·L-1), which was slightly undersaturated. The air-sea N2O flux in the region was -0.3±0.8 μmol·m-2·d-1; however, N2O in the surface water was oversaturated in most stations along the cruise track. Saturation anomalies were greater than 10%, with a maximum of 54.7% being observed at the Equator, followed by 31% at 10°N in the Sulu Sea. The air-sea fluxes at these locations were 12.4 and 4 μmol·m-2·d-1, respectively. Overall, the results indicated that surface water in Prydz Bay was near equilibrium with atmospheric N2O, and that ocean waters in lower latitudes acted as a N2O source. Physical processes such as stratification, ice-melt water dilution, and solar radiation dominate the factors leading to N2O saturation of surface water of Prydz Bay, while biological production and upwelling are primarily responsible for the N2O oversaturation of surface water observed in subtropical and tropical regions along the cruise track

Advances in Chinese and international biogeochemistry research in the western Arctic Ocean: a review

Over the past decades, the Arctic Ocean has experienced rapid warming under climate change, which has dramatically altered its physical and biogeochemical properties. Reduction in the sea-ice cover is one of the most important driving forces of biogeochemical changes in the Arctic Ocean. Between 1999 and 2016, seven Chinese National Arctic Research Expeditions have taken place in the Bering and Chukchi seas, allowing assessment of the biogeochemical response of the western Arctic Ocean to global warming. Herein, we summarize advances in Chinese and international marine biogeochemistry research in the western Arctic Ocean, reviewing results from the Chinese expeditions and highlighting future trends of biogeochemistry in the Pacific Arctic region. The findings reported in this paper contribute towards a better understanding of water masses, greenhouse gases, nutrients, ocean acidification, and organic carbon export and burial processes in this region

Deciphering the Properties of Different Arctic Ice Types During the Growth Phase of MOSAiC: Implications for Future Studies on Gas Pathways

The increased fraction of first year ice (FYI) at the expense of old ice (second-year ice (SYI) and multi-year ice (MYI)) likely affects the permeability of the Arctic ice cover. This in turn influences the pathways of gases circulating therein and the exchange at interfaces with the atmosphere and ocean. We present sea ice temperature and salinity time series from different ice types relevant to temporal development of sea ice permeability and brine drainage efficiency from freeze-up in October to the onset of spring warming in May. Our study is based on a dataset collected during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in 2019 and 2020. These physical properties were used to derive sea ice permeability and Rayleigh numbers. The main sites included FYI and SYI. The latter was composed of an upper layer of residual ice that had desalinated but survived the previous summer melt and became SYI. Below this ice a layer of new first-year ice formed. As the layer of new first-year ice has no direct contact with the atmosphere, we call it insulated first-year ice (IFYI). The residual/SYI-layer also contained refrozen melt ponds in some areas. During the freezing season, the residual/SYI-layer was consistently impermeable, acting as barrier for gas exchange between the atmosphere and ocean. While both FYI and SYI temperatures responded similarly to atmospheric warming events, SYI was more resilient to brine volume fraction changes because of its low salinity (< 2). Furthermore, later bottom ice growth during spring warming was observed for SYI in comparison to FYI. The projected increase in the fraction of more permeable FYI in autumn and spring in the coming decades may favor gas exchange at the atmosphere-ice interface when sea ice acts as a source relative to the atmosphere. While the areal extent of old ice is decreasing, so is its thickness at the onset of freeze-up. Our study sets the foundation for studies on gas dynamics within the ice column and the gas exchange at both ice interfaces, i.e. with the atmosphere and the ocean

32th Chinese Anantarctic Research Expedition N2O data at Antarctic Peninsula

&lt;p&gt;N2O is a greenhouse gas with a greenhouse potential 256 times higher than carbon dioxide on a century scale. The ocean is one of the important natural sources of this greenhouse gas. They affect the greenhouse gas budget of the atmosphere through the exchange of sea air interfaces, thereby affecting global warming. This data is the analysis data of N2O dissolved in seawater samples collected from CTD at different levels during China's 32nd Antarctic Scientific Expedition (2015-2016). It is of great significance for understanding the distribution and flux of N2O in the Antarctic Peninsula of the Southern Ocean, and has a guiding role in clarifying the impact of greenhouse gas exchange on climate change during the rapid retreat of sea ice in the Southern Ocean. 1. Measurement instrument name: Gas chromatography instrument model: Shimadzu 2010B Measurement method: Headspace calibration method: Use the national first-class N2O standard gas (with an accuracy of 1%) from the National Center for Reference Materials to calibrate the instrument signal value. 2. Observation method and data obtained. During the period from December 29, 2015 to January 14, 2016, seawater N2O samples were collected from 40 stations on the Antarctic Peninsula. 3. Observation area: The sea area under investigation during this voyage includes the Antarctic Peninsula&lt;/p&gt

32th Chinese Anatarctic Researh Expedition DIC and TA data at Antarctic Peninsula

&lt;p&gt;This data is the dissolved inorganic carbon (DIC) and total alkalinity (TA) of the carbonate system parameters during China's 32nd Antarctic Scientific Expedition (2015-2016). The relevant water samples were collected at designated stations in the Southern Ocean survey area using Niskin water samplers, properly preserved, and returned to the terrestrial laboratory for analysis. The parameters related to the carbonate system are of great significance for understanding the process, mechanism, and ability of CO2 absorption or transfer in the Southern Ocean and adjacent sea areas, as well as the ocean acidification status in the Southern Ocean and its specific sea areas. 1. Name and model of measuring instrument: Dissolved inorganic carbon analyzer (AS-C3, Apollo), alkalinity automatic titrator (AS-ALK2, Apollo). Calibration method: Use CO2 standard seawater from Scripps Research Institute in the United States to calibrate the instrument. 2. The observed data were collected from December 2015 to January 2016 in the Antarctic Peninsula region, Antarctica. Samples of dissolved inorganic carbon DIC and total alkalinity TA were collected from seawater&lt;/p&gt

Underway Measurement of Dissolved Inorganic Carbon (DIC) in Estuarine Waters

Dissolved inorganic carbon (DIC) is an important parameter of the marine carbonate system. Underway analyses of DIC are required to describe spatial and temporal changes of DIC in marine systems. In this study, we developed a microvolume flow detection method for the underway determination of DIC in marine waters, using gas-diffusion flow analysis in conjunction with electrical conductivity (EC) measurement. Only an acid carrier reagent (0.2 mol.L&minus;1) and an ultrapure water acceptor are required for the DIC monitoring system. In this system, a sampling loop (100 &micro;L) is used to quantify the injection sample volume, allowing micro-sample volume detection. The water sample reacts with the acid reagent to convert carbonate and bicarbonate species into CO2. The water sample is then carried into a gas-diffusion assembly, where the CO2 diffuses from the sampling stream into the acceptor stream. CO2 in the acceptor is detected subsequently by an electrical conductivity. The limit of DIC detection using ultrapure water is 0.16 mM. A good repeatability is obtained, with a relative standard deviation (RSD) of 0.56% (1 mM, n = 21). The time interval for detecting one sample is 5 min. During the observation period, measurements can be switched between standard solutions and water samples automatically. Accuracy and precision of the instrument is sufficient for the underway observation of marine DIC in estuarine waters

Nitrous oxide concentrations during CHINARE 36 cruise 2020

The data set comprises concentrations of dissolved N2O from seawater samples collected during the 36th Chinese Antarctic Research Expedition (36th CHINARE). The 36th CHINARE took place onboard the research vessel/icebreaker Xuelong 2 between the 3rd and 31st of January 2020 and focused on physical and biogeochemical surveys of the Ross Sea (Pacific sector of the Southern Ocean). Samples were collected by drawing water from 10 L Niskin bottles (installed on a standard CTD-Rosette) into brown borosilicate 20 mL vials, which were then sealed with rubber (butyl) stoppers and aluminium caps. Immediately after collection, samples were preserved by adding 0.05 mL of a saturated mercuric chloride solution. Samples were analyzed by means of a standard headspace method coupled to gas chromatography/electron capture detection. Details on the measurement equipment and data analysis can be found in Kock et al. (2016; see: www.biogeosciences.net/13/827/2016/)

Spatial Variability and Factors Influencing the Air-Sea N2O Flux in the Bering Sea, Chukchi Sea and Chukchi Abyssal Plain

The concentrations of the ozone-depleting greenhouse gas nitrous oxide (N2O) in the upper 300 m of the Subarctic and Arctic Oceans determined during the 5th Chinese National Arctic Research Expedition were studied. The surface water samples revealed that the study area could be divided into three regions according to the distribution of dissolved N2O in the surface water, namely, the Aleutian Basin (52° N–60° N), continental shelf (60° N–73° N) and Canadian Basin (north of 73° N), with N2O in the surface water in equilibrium, oversaturated and undersaturated relative to the atmosphere, respectively. The influences of physical and chemical processes, such as eddy diffusion and sedimentary emissions, beneath the surface layer are discussed. The results of a flux evaluation show that the Aleutian Basin may be a weak N2O source of approximately 0.46 ± 0.1 μmol·m−2·d−1, and the continental shelf acts as a strong N2O source of approximately 8.2 ± 1.4 μmol·m−2·d−1. By contrast, the Chukchi Abyssal Plain (CAP) of the Canadian Basin is at least a temporal N2O sink with a strength of approximately −10.2 ± 1.4 μmol·m−2·d−1