Recent increase of DIC in the western North Pacific

The temporal variation of the total dissolved inorganic carbon (DIC) content in the western North Pacific is investigated by comparing the DIC distribution obtained from the data sets of three different periods, the GEOSECS data observed in 1973, the CO₂ dynamics Cruise data observed in 1982, and recent Japanese data sets observed during the early 1990s. The overall feature of the signal of temporal DIC change during 1973 and early 1990s agreed with that of former studies, and did not significantly change with the calculation scheme (the grid-selection method vs. the multiple regression method). The observed increase in DIC among the different time scales showed a good inner consistency, which also indicates the stability of the method used in the DIC change calculation. The apparent rate of increase of the DIC inventory in the upper 1000 m water column, however, differed significantly by the data set used for the calculation: It was 5.6±2.4 g C/m²/year, based on the data comparison between 1982 and the early 1990s, while it became 7.6±2.4 g C/m²/year when based on the data between 1973 and the early 1990s. This result provides us an information about the data-dependency on the former estimation of temporal DIC change.     

Splitting of the subtropical gyre in the western North Pacific

Examined here is a hypothetical idea of the splitting of the subtropical gyre in the western North Pacific on the basis of two independent sources of data,i.e., the long-term mean geopotential-anomaly data compiled by the Japanese Oceanographic Data Center and the synoptic hydrographic (STD) data taken by the Hakuho Maru in the source region of the Kuroshio and the Subtropical Countercurrent in the period February and March 1974. Both of the synoptic and the long-term mean dynamic-topographic maps reveal three major ridges, which indicate that the western subtropical gyre is split into three subgyres. Each subgyre is made up of the pair of currents, the Kuroshio and the Kuroshio Countercurrent, the Subtropical Countercurrent and a westward flow lying just south of the Countercurrent (18°N–21°N), and the northern part of the North Fquatorial Current and an eastward flow at around 18°N. The subgyres are more or less composed of a train of anticyclonic eddies with meridional scales of between 300 and 600 km, so that the volume transport of the subgyres varies by a factor of two or more from section to section. The upper-water characteristics also support the splitting of the subtropical gyre; the water characteristics are fairly uniform within each subgyre, but markedly different between them. The northern rim of each subgyre appears as a sharp density front accompanied by an eastward flow. The bifurcations of the sharp density fronts across the western boundary current indicate that the major part of the surface waters in the North Equatorial Countercurrent is not brought into the Kuroshio. The western boundary current appears as a continuous feature of high speed, but the waters transported change discontinuously at some places.     

High-resolution IP<Subscript>25</Subscript>-based reconstruction of sea-ice variability in the western North Pacific and Bering Sea during the past 18,000 years

Due to its strong influence on heat and moisture exchange between the ocean and the atmosphere, sea ice is an essential component of the global climate system. In the context of its alarming decrease in terms of concentration, thickness and duration, understanding the processes controlling sea-ice variability and reconstructing paleo-sea-ice extent in polar regions have become of great interest for the scientific community. In this study, for the first time, IP₂₅, a recently developed biomarker sea-ice proxy, was used for a high-resolution reconstruction of the sea-ice extent and its variability in the western North Pacific and western Bering Sea during the past 18,000 years. To identify mechanisms controlling the sea-ice variability, IP₂₅ data were associated with published sea-surface temperature as well as diatom and biogenic opal data. The results indicate that a seasonal sea-ice cover existed during cold periods (Heinrich Stadial 1 and Younger Dryas), whereas during warmer intervals (Bølling-Allerød and Holocene) reduced sea ice or ice-free conditions prevailed in the study area. The variability in sea-ice extent seems to be linked to climate anomalies and sea-level changes controlling the oceanographic circulation between the subarctic Pacific and the Bering Sea, especially the Alaskan Stream injection though the Aleutian passes.     

Spatial and Temporal Variation of Surface xCO<Subscript>2</Subscript> Providing Net Biological Productivities in the Western North Pacific in June

More than 14,000 measurements of surface water xCO₂ were obtained during two cruises, 3 weeks apart in June 2000, along 155°E between 34 and 44°N in the western North Pacific Ocean. Based on the distributions of salinity and sea surface temperature (SST), the region has been divided into 6 subregions; Oyashio, Oyashio front, Transition, Kuroshio front, and Kuroshio extension I and II zones, from north to south. The surface waters were always undersaturated with respect to atmospheric CO₂. The Oyashio water was the least undersaturated: its xCO₂ decreased slightly by 7 ppm, while SST increased by 2°C. The xCO₂ normalized to a constant temperature decreased considerably. In the two frontal zones, a large drawdown of 30–40 ppm was observed after 18–19 days. In the Kuroshio extension zones, the xCO₂ increased, but the normalized xCO₂ decreased considerably. The Transition zone water may be somewhat affected by mixing with the subsurface water, as indicated by the smallest SST rise, an undecreased PO₄ concentration, and a colder and less stable surface layer than the Oyashio front water. As the uncertainty derived from the air-sea CO₂ flux was not large, the xCO₂ data allowed us to calculate the net biological productivity. The productivities around 60 mmol C m⁻²d⁻¹ outside the Transition zone indicate that the northwestern North Pacific, especially the two frontal zones, can be regarded as one of the most productive oceans in the world.     

Seasonal variability of surface and internal M<Subscript>2</Subscript> tides in the Arctic Ocean

The modeling results of surface and internal M₂ tides for summer and winter periods in the Arctic Ocean (AO) are presented. We employed a modified version of the three-dimensional finite-element hydrothermodynamic model QUODDY-4 differing from the original model by using a rotated (instead of spherical) coordinate system and by considering the equilibrium-tide effects. It has been shown that the modeling results for the surface tide differs little from the results obtained earlier by other authors. According to these results, the amplitudes of internal tidal waves (ITWs) in the AO are significantly lower than in other oceans and the ITWs proper have the character of trapped waves. Their source of generation is located at the continental slope northwest of the New Siberian Islands. Our results are consistent with the fields of average (over a tidal cycle) and integral (by depth) densities of baroclinic tidal energy, the maximum baroclinic tidal velocity, and the coefficient of diapycnic mixing. The local rate of baroclinic tidal energy dissipation at the AO ridges increases as it approaches the bottom, as was observed on Mid-Atlantic and Hawaii ridges (but merely within the bottom boundary layer) and is two to three orders of magnitude lower than in other oceans. The ITW degeneration scale in the AO is several hundreds of kilometers in summer and winter, remaining within the range of its values between 100 and 1000 km in mid- and low-latitude oceans. In both seasons, the integral (over the AO area) rate of baroclinic tidal energy dissipation is two orders of magnitude lower than the global estimate (2.5 × 10¹² W).     

Response of the western North Pacific subtropical ocean to the slow-moving super typhoon Nanmadol

Based on in-situ observation,satellite and reanalysis data,responses of the western North Pacific subtropical ocean(WNPSO)to the slow-moving category 5 super typhoon Nanmadol in 2011 are analyzed.The dynamical response is dominated by near-inertial currents and Ekman currents with maximum amplitude of 0.39m/s and 0.15m/s,respectively.The near-inertial currents concentrated around 100m below the sea surface and had an e-folding timescale of 4 days.The near-inertial energy propagated both upward and downward,and the vertical phase speed and wavelength were estimated to be 5m/h and 175m,respectively.The frequency of the near-inertial currents was blue-shifted near the surface and redshifted in ocean interior which may relate to wave propagation and/or background vorticity.The resultant surface cooling reaches-4.35℃ and happens when translation speed of Nanmadol is smaller than 3.0m/s.When Nanmadol reaches super typhoon intensity,the cooling is less than 3.0℃ suggesting that the typhoon translation speed plays important roles as well as typhoon intensity in surface cooling.Upwelling induced by the slow-moving typhoon wind leads to typhoon track confined cooling area and the right-hand bias of cooling is slight.The mixed layer cooling and thermocline warming are induced by wind-generated upwelling and vertical entrainment.Vertical entrainment also led to mixed layer salinity increase and thermocline salinity decrease,however,mixed layer salinity decrease occurs at certain stations as well.Our results suggest that typhoon translation speed is a vital factor responsible for the oceanic thermohaline and dynamical responses,and the small Mach number(slow typhoon translation speed)facilitate development of Ekman current and upwelling.     

Methane in the western North Pacific

The concentration of methane in about 400 seawater samples collected in the western North Pacific, mostly from 40°N to 5°S along 165°E was determined. While the concentration of methane in the surface water was slightly greater in the high-latitudes, it did not widely vary with a standard deviation of 0.29 n mol/l for a mean value of 2.49 n mol/l. The 90% confidence limit of the mean was 0.08 n mol/l. The degree of oversaturation in 1991 (31±4%) was not different from that in circa 1970. If we assume that this degree of oversaturation occurs in the entire oceans, the annual flux of methane becomes 6×10¹²g CH₄. Both the concentrations of methane and chlorophylla were higher in the surface 100 m layer. However, the correlation between them was not well in the entire surface waters. This may indicate that the production of methane is not directly related to the photosynthetic process. The concentration of methane decreased gradually with increasing depth down to 1000 m. Its horizontally and vertically uniform concentration in the abyssal water suggests that the turnover time of methane in the oxic pelagic water is in the range between a few years and a few hundred years.     

西太平洋副热带高压变化与赤道太平洋海温场的联系

通过对西太平洋副热带高压变化的多年统计分析,发现其具有明显的年际和年代际变化特征,副高面积和强度均存在3~4 a和11~14 a显著周期,副高西伸脊点存在3~5 a和准13 a显著周期。副高面积和强度变化基本一致,与赤道中东太平洋海表温度（SST）存在显著的正相关关系,西伸脊点与中东太平洋海表温度变化则存在负的相关关系。赤道太平洋不同经度的SST与副高变化存在明显的差异,赤道中太平洋SST异常与副高变化的关系最为密切,东太平洋相对偏弱,而西太平洋呈现相反的相关关系。由此可以认为,赤道中太平洋异常SST变化是影响副高变化的关键区域。根据它们之间存在的密切关系,通过回归分析,建立了它们二者之间的回归方程,对2013年春夏季副高的强度和西伸脊点位置变化进行了预测,为2013年我国汛期降水预测提供一定的参考。     

Sudden stratospheric warmings: statistical characteristics and influence on NO<Subscript>2</Subscript> and O<Subscript>3</Subscript> total contents

Statistical characteristics of major and minor sudden stratospheric warmings (SSWs) in the Northern Hemisphere (NH) for 1958–2015 are analyzed using data of NCEP-NCAR, ERA 40, and ERA-Interim reanalyses. Dependencies of the number of major SSWs with the displacement of the circumpolar stratospheric vortex and the number of minor SSWs on the phase of the quasi-biennial oscillation (QBO) of the equatorial stratospheric wind and on the level of solar activity (SA) in the 11-year solar cycle have been revealed. Major SSWs accompanied by a displacement of the polar vortex occur more often at a high level of SA and at the easterly phase of the QBO in the 50–40 hPa layer, while minor SSWs occur more often at a low SA level and at the westerly phase of the QBO. An analysis of spatiotemporal dynamics of the stratospheric polar vortex at major SSWs is performed. The most probable directions of vortex displacement caused by SSWs have been revealed. Influences of the major SSWs on the total contents of NO₂ and ozone, as well as on stratosphere temperature, are analyzed.     

Comparing data obtained from ground-based measurements of the total contents of O<Subscript>3</Subscript>, HNO<Subscript>3</Subscript>,HCl,and NO<Subscript>2</Subscript> and from their numerical simulation

Chemistry climate models of the gas composition of the atmosphere make it possible to simulate both space and time variations in atmospheric trace-gas components (TGCs) and predict their changes. Both verification and improvement of such models on the basis of a comparison with experimental data are of great importance. Data obtained from the 2009–2012 ground-based spectrometric measurements of the total contents (TCs) of a number of TGCs (ozone, HNO₃, HCl, and NO₂) in the atmosphere over the St. Petersburg region (Petergof station, St. Petersburg State University) have been compared to analogous EMAC model data. Both daily and monthly means of their TCs for this period have been analyzed in detail. The seasonal dependences of the TCs of the gases under study are shown to be adequately reproduced by the EMAC model. At the same time, a number of disagreements (including systematic ones) have been revealed between model and measurement data. Thus, for example, the EMAC model underestimates the TCs of NO₂, HCl, and HNO₃, when compared to measurement data, on average, by 14, 22, and 35%, respectively. However, the TC of ozone is overestimated by the EMAC model (on average, by 12%) when compared to measurement data. In order to reveal the reasons for such disagreements between simulated and measured data on the TCs of TGCs, it is necessary to continue studies on comparisons of the contents of TGCs in different atmospheric layers.     

Latitudinal dependence of variations in stratospheric NO<Subscript>2</Subscript> content

Diurnal and annual variations in the NO₂ total content (TC), the effect of its decrease owing to the products of the eruption of Mt. Pinatubo, its variations during an 11-year cycle of solar activity, and its linear trends are analyzed on the basis of data obtained from the ground-based spectrometric measurements of the NO₂ TC in stratospheric vertical columns over the stations of the Network for the Detection of Atmospheric Composition Change. Latitudinal dependence of the indicated variations and trends is revealed. The annual estimates of the linear trends of the NO₂ TC are found to be mostly positive for the middle and low latitudes of the Southern Hemisphere and negative for the middle and low latitudes of the Northern Hemisphere. The maximum values of the positive and negative trends amount to ～10% per ten years. In the high and polar latitudes of both hemispheres, the annual trend estimates are statistically insignificant. Seasonal estimates of the trends may differ from their annual estimates. The trends and solar-activity effect in the NO₂ TC, which were estimated by using the two-dimensional model SOCRATES, as well as the analytical estimates of a zonal mean trend of the NO₂ TC, on the whole, significantly differ from the estimates obtained from the measurements.     

Trophic coupling between <Emphasis Type="Italic">Synechococcus</Emphasis> and pigmented nanoflagellates in the coastal waters of Taiwan,western subtropical Pacific

In our attempt to characterize the interaction of trophic coupling between Synechococcus and pigmented nanoflagellates (PNFs), successive size-fraction experiments were performed at a coastal station on the northeast coast of Taiwan from June, 2005 to January, 2006. By estimating the growth rate and grazing rate of Synechococcus in the presence of nanoflagellates of different sizes, we truncated the food web by removing organisms with different body sizes (<2 μm, <5 μm, <10 μm, and <20 μm). The growth rates of Synechococcus ranged from −0.016 to 0.051 h⁻¹ during the experimental period, suggesting that temperature was a primary mechanism controlling Synechococcus growth. In addition to size and relative biomass of pigmented nanoflagellates and Synechococcus, it is suggested that community structures played an important role in trophic link. Furthermore, we conclude that the trophic cascading effect in the northeast coast of Taiwan includes: 1) high grazing rates at night in the warm season; 2) the Synechococcus biomass generally exceeds the grazing threshold (6 × 10⁴ cells mL⁻¹); and 3) the biomass ratio of <5 μm PNFs to >5 μm PNFs should be 1:1 to 2:1.     

Effects of CO<Subscript>2</Subscript> Enrichment on Marine Phytoplankton

Rising atmospheric CO₂ and deliberate CO₂ sequestration in the ocean change seawater carbonate chemistry in a similar way, lowering seawater pH, carbonate ion concentration and carbonate saturation state and increasing dissolved CO₂ concentration. These changes affect marine plankton in various ways. On the organismal level, a moderate increase in CO₂ facilitates photosynthetic carbon fixation of some phytoplankton groups. It also enhances the release of dissolved carbohydrates, most notably during the decline of nutrient-limited phytoplankton blooms. A decrease in the carbonate saturation state represses biogenic calcification of the predominant marine calcifying organisms, foraminifera and coccolithophorids. On the ecosystem level these responses influence phytoplankton species composition and succession, favouring algal species which predominantly rely on CO₂ utilization. Increased phytoplankton exudation promotes particle aggregation and marine snow formation, enhancing the vertical flux of biogenic material. A decrease in calcification may affect the competitive advantage of calcifying organisms, with possible impacts on their distribution and abundance. On the biogeochemical level, biological responses to CO₂ enrichment and the related changes in carbonate chemistry can strongly alter the cycling of carbon and other bio-active elements in the ocean. Both decreasing calcification and enhanced carbon overproduction due to release of extracellular carbohydrates have the potential to increase the CO₂ storage capacity of the ocean. Although the significance of such biological responses to CO₂ enrichment becomes increasingly evident, our ability to make reliable predictions of their future developments and to quantify their potential ecological and biogeochemical impacts is still in its infancy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Vertical structure of the M<Subscript>2</Subscript> tidal current in the Yellow Sea

The vertical structure of the M₂ tidal current in the Yellow Sea is analyzed from data acquired using an acoustic Doppler current profiler. The observed vertical profiles of the M₂ tidal current are decomposed into two rotating components of counter-clockwise and clockwise, and restructured using a simple one-point model with a constant vertical eddy viscosity. The analyzed results show that the internal fictional effect dominates the vertical structure of the tidal current in the bottom boundary layer. In the Yellow Sea, the effect of the bottom friction reduces the current speed by about 20–40% and induces the bottom phase advance by about 15–50 minutes. In the shallower coastal regions, the effects of bottom topography are more prominent on the vertical structure of tidal currents. The vertical profile of the tidal current in summer, when the water column is strongly stratified, is disturbed near the pycnocline layer. The stratification significantly influences the vertical shear and distinct seasonal variation of the tidal current.     

Spatial structure of the <Emphasis Type="Italic">M</Emphasis><Subscript>2</Subscript> tidal wave in the canadian arctic archipelago

The surface M ₂ tide in the Canadian Arctic Archipelago (CAA) is reproduced on the basis of the QUODDY-4 three-dimensional finite-element hydrodynamic model. Particular emphasis has been placed on comparing model estimates for the amplitudes and phases of tidal elevations and the parameters of ellipses (major semiaxis and eccentricity) of the barotropic tidal current velocity with observational data. We present their spatial distributions and the distributions of averaged (over a tidal cycle) values of the density, horizontal transfer, and dissipation rate of barotropic tidal energy. It is found that the CAA is a much less effective dissipator of barotropic tidal energy than the World Ocean.     

Retrieval of total ozone in the mesosphere with a new model of electronic-vibrational kinetics of O<Subscript>3</Subscript> and O<Subscript>2</Subscript> photolysis products

The paper presents a new model of electronic-vibrational kinetics of the products of ozone and molecular oxygen photodissociation in the terrestrial middle atmosphere. The model includes 45 excited states of the oxygen molecules O₂(b ¹, Σ _g ⁺ ,v= 0−2), O₂ (a ¹Δ _g , v= 0−5), and O₂(X ³Σ _g ⁻ , v= 1−35) and of the metastable atom O (¹ D) and over 100 aeronomic reactions. The model takes into account the dependence of quantum yields of the production of O₂(a ¹Δ _g , v= 0−5) in a singlet channel of ozone photolysis in the Hartley band on the wavelength of photolytic emission. Taking account of the electronic-vibrational kinetics is important in retrieval of the vertical profiles of ozone concentration from measured intensities of the Atm and IR Atm emissions of the oxygen bands above 65 km and leads to an increase in the ozone concentration retrieved from the 1.27-μm emission, in contrast to the previous model of pure electronic kinetics. Sensitivity analysis of the new model is made for variations in the concentrations of atmospheric constituents ([O₂], [N₂], [O(³P)], [O₃], [CO₂]), the gas temperature, rate constants of the reactions, and quantum yields of the reaction products. A group of reactions that most strongly affect the uncertainty of ozone retrieval from measured intensities of atmospheric emissions of molecular oxygen O₂(b ¹Σ _g ⁺ , v) and O₂(a ¹Δ _g , v) has been determined. Original Russian Text ? V.A. Yankovsky, V.A. Kuleshov, R.O. Manuilova, A.O. Semenov, 2007, published in Izvestiya AN. Fizika Atmosfery i Okeana, 2007, Vol. 43, No. 4, pp. 557–569.     

The influence of the spatial heterogeneity of vegetation cover and surface topography on vertical CO<Subscript>2</Subscript> fluxes within the atmospheric surface layer

The influence of the spatial heterogeneity of vegetation cover and topography on CO₂ fluxes in the atmospheric surface layer is estimated using a two-dimensional (2D) hydrodynamic model of turbulent exchange. A ~4.5-km-long profile that crossed a hilly area with a mosaic vegetation cover in Tula region was selected for model experiments. During the first experiment, a wind field and vertical fluxes were calculated by the 2D model for the entire selected profile with respect to the horizontal heterogeneity of the vegetation cover and surface topography. In the second experiment, the profile was considered an assemblage of elementary independent homogeneous segments; for each of them, vertical fluxes were calculated by the 2D model with the assumption of ‘zero’ horizontal advection, i.e., the required functions are independent of the horizontal coordinates. The influences of any boundary effects that appear at the interface between the different vegetation communities and at topographical irregularities on the turbulent regime are ignored in this case. For the profile selected, ignoring the horizontal advection, disturbances in the wind field that appeared at surface topography irregularities, and boundaries between different vegetation communities can lead to a 26% underestimation of the total CО₂ absorption by the ground surface on a clear sunny day under summer weather conditions.     

Perspectives on Biological Research for CO<Subscript>2</Subscript> Ocean Sequestration

Feasibility studies recently suggest that sequestration of anthropogenic CO₂ in the deep ocean could help reduce the atmospheric CO₂ concentration. However, implementation of this strategy could have a significant environmental impact on marine organisms. This has highlighted the urgent need of further studies concerning the biological impact of CO₂ ocean sequestration. In this paper we summarize the recent literature reporting on the biological impact of CO₂ and discuss the research work required for the future. Although fundamental research of the effect of CO₂ on marine organisms before the practical consideration of CO₂ ocean sequestration was limited, laboratory and field studies concerning biological impacts have been increasing after the first international workshop in 1991 discussing CO₂ ocean sequestration. Acute impacts of CO₂ ocean sequestration could be determined by laboratory and field experiments and assessed by simulation models as described by the following papers in this section. On the other hand, chronic effects of CO₂ ocean sequestration, those directly related to the marine ecosystem, would be difficult to verify by means of experiments and to assess using ecosystem models. One of the practical solutions for this issue implies field experiments starting with controlled small scale and eventually to a large scale of CO₂ injection intended to determine ecosystem alteration. This revised version was published online in July 2006 with corrections to the Cover Date.