Wave climate off northern Norway

The wave climate off northern Norway is considered and the investigation is based on wave measurements made at Tromsøflaket by means of a waverider buoy during the years 1977–1981. Data quality of waverider measurements is briefly commented upon; however, more emphasis is given to an evaluation of the long-term representativity of the actual measuring period and to a procedure accounting approximately for a lack of representativity. The wave climate is presented in terms of a smoothed joint probability density function of the significant wave height, H_s, and the spectral peak period, T_p. Based on this distribution a consistent design curve in the H_s, T_p space is established.     

A generalized approach for long-term modelling of extreme crest-to-trough wave heights

This paper deals with the long-term modelling of high sea waves. The solution is given for the return period of sea storms during which an arbitrary chosen number of waves, with crest-to-trough heights exceeding a fixed threshold, occur. This return period is derived starting from the Equivalent Triangular Storm (ETS) model, which associates a triangle to each actual storm and thus represents a significant wave height time series at a fixed location by means of a sequence of triangular storms. The short-term statistics is then applied to investigate the occurrence of large crest-to-trough wave heights during a given storm. Finally, by combining the statistical distribution of significant wave heights, the ETS model and the short-term wave statistics, the solution is given for the return periods R_N and R_N of a sea storm in which N or at least N waves higher than a fixed threshold occur. The values of R_N are then calculated, starting from data of two buoys moored in the Pacific Ocean and in the Mediterranean Sea.     

地热对海洋影响的实验室模拟

This study, using laboratory experiments and scaling analysis, evaluates the influence of geothermal heating on global oceanic circulation. Upon a well-developed large-scale convective flow, an additional heat flux perturbation δF/F is employed. The increments of flow and thermal properties, including eddy diffusivity KT, flow velocity V and bottom temperature Tb, are found to be independent of the applied heat flux F. Together with the scaling analysis of convective flow at different configurations, where the flow is thermally driven in the relatively low or extremely high turbulent thermal convections or the horizontal convection, the variances of flow properties, δKT/KT and δV/V, are found to be close to 0.5% and 0.75% at δF/F=2%. This means that the small heat flux perturbation plays a negligible role in the global convective flow. However, δTb/ΔT is found to be 1.5% at δF/F=2%, which would have a significant effect in the local region. The results might provide a clue to understanding the influence of geothermal heating on global oceanic circulation. It is expected that geothermal heating will contribute less than 1% in turbulent mixing and volume flux to global oceanic circulation, so its influence can be negligible in this situation. However, when it comes to the local environment, the influence of geothermal heating cannot be ignored. For example, temperature increases of about 0.5°C with geothermal heating would have a significant effect on the physical environments within the benthic boundary layer.     

以海浪波要素表示的外频谱形式

孙孕等（１９９４）提出了外频谱的概念,并推导出外频谱的理论形式,但其控制参量是由内频谱导出的,不便于实际应用,通过对实测海浪数据的分析,得到了控制外频谱的３个和内频谱有关的参量与波浪要素之间的关系,进而将外频谱表示以有效波高和有效波周期作为控制参量的形式,应用实测资料将本文得到的外频谱形式与理论外频谱进行了比较,发现二者符合良好。     

Seasonal and interannual variability of the air–sea CO2 flux in the Atlantic sector of the Barents Sea

The seasonal and interannual variability of the air–sea CO₂ flux (F) in the Atlantic sector of the Barents Sea have been investigated. Data for seawater fugacity of CO₂ (fCO₂^sw) acquired during five cruises in the region were used to identify and validate an empirical procedure to compute fCO₂^sw from phosphate (PO₄), seawater temperature (T), and salinity (S). This procedure was then applied to time series data of T, S, and PO₄ collected in the Barents Sea Opening during the period 1990–1999, and the resulting fCO₂^sw estimates were combined with data for the atmospheric mole fraction of CO₂, sea level pressure, and wind speed to evaluate F.The results show that the Atlantic sector of the Barents Sea is an annual sink of atmospheric CO₂. The monthly mean uptake increases nearly monotonically from 0.101 mol C m^− 2 in midwinter to 0.656 mol C m^− 2 in midfall before it gradually decreases to the winter value. Interannual variability in the monthly mean flux was evaluated for the winter, summer, and fall seasons and was found to be ± 0.071 mol C m^− 2 month^− 1. The variability is controlled mainly through combined variation of fCO₂^sw and wind speed. The annual mean uptake of atmospheric CO₂ in the region was estimated to 4.27 ± 0.68 mol C m^− 2.     

Modelling the carbon export and air–sea flux of CO2 in the Greenland Sea

We have developed a 3D model for the carbon cycle and air–sea flux of CO₂ in the Greenland Sea that consists of three submodels for hydrodynamics, carbon chemistry and plankton ecology. The hydrodynamical model, based on the primitive Navier–Stokes equations, simulates the physical environment that is used for the chemical and biological models. The chemical model calculates the pCO₂ as a function of the total inorganic carbon, alkalinity, temperature and salinity. The ecological model has eight state variables and simulates the transformation of CO₂ into organic carbon, vertical transport, and the respiration processes that convert the organic carbon back into inorganic form. The model gives an average annual primary production of 68 g C m⁻² y⁻¹, of which 44.7 g C m⁻² y⁻¹ is new production. In the eastern part of the Greenland Sea, the average annual new production is above 50 g C m⁻² y⁻¹. Simulated, annual flux of CO₂ from the atmosphere is 53 g C m⁻² y⁻¹, which sums up to 0.026 Gt for the whole Greenland Sea. Of this, 9 g C m⁻² y⁻¹ is exported by sinking particles, 6 g C m⁻² y⁻¹ by migrating zooplankton (mainly Calanus hyperboreus), and 38 g C m⁻² y⁻¹ by advection.     

Volume and heat transports and material fluxes in the East China Sea during April 1994

INTRODUCTIONTherehavebeenmanystudiesandcomputationsonVToftheKuroshiointheEastChinaThisprojectwassupportedbytheNationalNaturalScienceFoundationofChinaundercontractNo.49476278.Asanditsvacation.Forexample,(1)basedonhydrographicobservationsatactionG(PN)f...     

A global wave parameter database for geophysical applications. Part 1: Wave-current–turbulence interaction parameters for the open ocean based on traditional parameterizations

Ocean surface mixing and drift are influenced by the mixed layer depth, buoyancy fluxes and currents below the mixed layer. Drift and mixing are also functions of the surface Stokes drift U_ss, volume Stokes transport T_S, a wave breaking height scale H_swg, and the flux of energy from waves to ocean turbulence Φ_oc. Here we describe a global database of these parameters, estimated from a well-validated numerical wave model, that uses traditional forms of the wave generation and dissipation parameterizations, and covers the years 2003–2007. Compared to previous studies, the present work has the advantage of being consistent with the known physical processes that regulate the wave field and the air–sea fluxes, and also consistent with a very large number of in situ and satellite observations of wave parameters. Consequently, some of our estimates differ significantly from previous estimates. In particular, we find that the mean global integral of Φ_oc is 68 TW, and the yearly mean value of T_S is typically 10–30% of the Ekman transport, except in well-defined regions where it can reach 60%. We also have refined our previous estimates of U_ss by using a better treatment of the high frequency part of the wave spectrum. In the open ocean, U_ss ≃ 0.013U₁₀, where U₁₀ is the wind speed at 10 m height.     

Wave groupiness and spectral bandwidth as relevant parameters for the performance assessment of wave energy converters

To date the estimation of long-term wave energy production at a given deployment site has commonly been limited to a consideration of the significant wave height H_s and mean energy period T_e. This paper addresses the sensitivity of power production from wave energy converters to the wave groupiness and spectral bandwidth of sea states. Linear and non-linear systems are implemented to simulate the response of converters equipped with realistic power take-off devices in real sea states. It is shown in particular that, when the converters are not much sensitive to wave directionality, the bandwidth characteristic is appropriate to complete the set of overall wave parameters describing the sea state for the purpose of estimating wave energy production.     

Summer and winter air–sea CO2 fluxes in the Southern Ocean

The seasonal variability of the carbon dioxide (CO₂) system in the Southern Ocean, south of 50°S, is analysed from observations obtained in January and August 2000 during OISO cruises conducted in the Indian Antarctic sector. In the seasonal ice zone, SIZ (south of 58°S), surface ocean CO₂ concentrations are well below equilibrium during austral summer. During this season, when sea-ice is not obstructing gas exchange at the air–sea interface, the oceanic CO₂ sink ranges from −2 to −4 mmol/m²/d in the SIZ. In the permanent open ocean zone, POOZ (50–58°S), surface oceanic fugacity fCO₂ increases from summer to winter. The seasonal fCO₂ variations (from 10 to 30 μatm) are relatively low compared to seasonal amplitudes observed in the subtropics or the subantarctic zones. However, these variations in the POOZ are large enough to cross the atmospheric level from summer to winter. Therefore, this region is neither a permanent CO₂ sink nor a permanent CO₂ source. In the POOZ, air–sea CO₂ fluxes calculated from observations are about −1.1 mmol/m²/d in January (a small sink) and 2.5 mmol/m²/d in August (a source). These estimates obtained for only two periods of the year need to be extrapolated on a monthly scale in order to calculate an integrated air–sea CO₂ flux on an annual basis. For doing this, we use a biogeochemical model that creates annual cycles for nitrate, inorganic carbon, total alkalinity and fCO₂. The changing pattern of ocean CO₂ summer sink and winter source is well reproduced by the model. It is controlled mainly by the balance between summer primary production and winter deep vertical mixing. In the POOZ, the annual air–sea CO₂ flux is about −0.5 mol/m²/yr, which is small compared to previous estimates based on oceanic observations but comparable to the small CO₂ sink deduced from atmospheric inverse methods. For reducing the uncertainties attached to the global ocean CO₂ sink south of the Polar Front the regional results presented here should be synthetized with historical and new observations, especially during winter, in other sectors of the Southern Ocean.     

Biological versus physical processes as drivers of large oscillations of the air–sea CO2 flux in the Antarctic marginal ice zone during summer

The fugacity of CO₂ and abundance of chlorophyll a (Chla) were determined in two long transects from the Polar Front to the Antarctic Continent in austral summer, December 1995–January 1996. Large undersaturations of CO₂ in the surface water were observed coinciding with high Chla content. In the major hydrographic regions the mean air–sea fluxes were found to range from −3 to +7 mmol m⁻² d⁻¹ making these regions act as a sink as well as a source for CO₂. In the total 40-d period, the summation of the several strong source and sink regions revealed an overall modest net source of 0.3 mmol m⁻² d⁻¹, this based on the Wanninkhof (J. Geophys. Res. 97 (1992) 7373) quadratic relationship at in situ windspeed. A simple budget approach was used to quantify the role of phytoplankton blooms in the inorganic carbonate system of the Antarctic seas in a time frame spanning several weeks. The major controlling physical factors such as air–sea flux, Ekman pumping and upwelling are included. Net community production varies between −9 and +7 mmol m⁻² d⁻¹, because of the large oscillations in the dominance of autotrophic (CO₂ fixation) versus heterotrophic (CO₂ respiration) activity. Here the mixed layer depth is the major controlling factor. When integrated over time the gross influx and efflux of CO₂ from air to sea is large, but the net residual air/sea exchange is a modest efflux from sea to atmosphere.     

Empirical ocean-color algorithms to retrieve chlorophyll-a, total suspended matter, and colored dissolved organic matter absorption coefficient in the Yellow and East China Seas

A bio-optical dataset collected during the 1998?C2007 period in the Yellow and East China Seas (YECS) was used to provide alternative empirical ocean-color algorithms in the retrieval of chlorophyll-a (Chl-a), total suspended matter (TSM), and colored dissolved organic matter (CDOM) absorption coefficients at 440 nm (ag₄₄₀). Assuming that remote-sensing reflectance (Rrs) could be retrieved accurately, empirical algorithms for T_Chl (regionally tuned Tassan??s Chl-a algorithm) in case-1 waters (T_Chl2i in case-2 waters), T_TSM (regionally tuned Tassan??s TSM algorithm), and T_ag440 or C_ag440 (regionally tuned Tassan??s or Carder??s ag₄₄₀ algorithm) were able to retrieve Chl-a, TSM, and ag₄₄₀ with uncertainties as high as 35, 46, and 35%, respectively. Applying the standard SeaWiFS Rrs, T_Chl was not viable in the eastern part of the YECS, which was associated with an inaccurate SeaWiFS Rrs retrieval because of improper atmospheric correction. T_Chl behaved better than other algorithms in the turbid case-2 waters, although overestimation was still observed. To retrieve more reliable Chl-a estimates with standard SeaWiFS Rrs in turbid water (a proxy for case-2 waters), we modified T_Chl for data with SeaWiFS normalized water-leaving radiance at 555 nm (nLw₅₅₅) > 2 mW cm^?2 ??m^?1 sr^?1 (T_Chl2s). Finally, with standard SeaWiFS Rrs, we recommend switching algorithms from T_Chl2s (for case-2 waters) to MOC_Chl (SeaWiFS-modified NASA OC4v4 standard algorithm for case-1 waters) for retrieving Chl-a, which resulted in uncertainties as high as 49%. To retrieve TSM and ag₄₄₀ using SeaWiFS Rrs, we recommend empirical algorithms for T_TSM (pre-SeaWiFS-modified form) and MT_ag440 or MC_ag440 (SeaWiFS Rrs-modified forms of T_ag440 or C_ag440). These could retrieve with uncertainties as high as 82 and 52%, respectively.     

Variability of gas composition and flux intensity in natural marine hydrocarbon seeps

The relationship between surface bubble composition and gas flux to the atmosphere was examined at five large seeps from the Coal Oil Point seep field (Santa Barbara Channel, CA, USA). The field research was conducted using a flux buoy designed to simultaneously measure the surface bubbling gas flux and the buoy’s position with differential GPS, and to collect gas samples. Results show that the flux from the five seeps surveyed a total of 11 times ranged from 800–5,500 m³ day^?1. The spatial distribution of flux from the five seeps was well described by two lognormal distributions fitted to two flux ranges. The seafloor and sea surface composition of bubbles differed, with the seafloor bubbles containing significantly more CO₂ (3–25%) and less air (N₂ and O₂). At the sea surface, the mole fraction of N₂ correlated directly with O₂ (R ² = 0.95) and inversely with CH₄ (R ² = 0.97); the CO₂ content was reduced to the detection limit (<0.1%). These data demonstrate that the bubble composition is modified by gas exchange during ascent: dissolved air enters, and CO₂ and hydrocarbon gases leave the bubbles. The mean surface composition at the five seeps varied with water depth and gas flux, with more CH₄ and higher CH₄/N₂ ratios found in shallower seeps with higher flux. It is suggested that the CH₄/N₂ ratio is a good proxy for total or integrated gas loss from the rising bubbles, although additional study is needed before this ratio can be used quantitatively.     

Polar lows and tropical hurricanes: Their energy and sizes and a quantitative criterion for their generation

Similarity and dimension considerations applied to convection in a rotating fluid allows one to estimate the sizes and horizontal velocities of generated vortices. To do this, it is necessary to know the buoyancy flux in the fluid and the angular velocity of fluid rotation [1, 2]. The author’s preliminary efforts [3] have shown that the sizes, wind speeds, and total kinetic energy can thus be estimated correctly for tropical cyclones (TCs), as well as for polar lows (PLs) (which are often called explosive mesocyclones because they take just a few hours to develop). In this study, the sensible and latent heat fluxes for U = 33 m/s and the related buoyancy fluxes are estimated on the basis of climatology, bulk formulas, and the velocity scale of convection in a rotating fluid. In the tropics, at hurricane wind speeds U ≥ 33 m/s and climatological air humidity r = 80%, the total heat flux at the water surface temperature T _s ≥ 26°C becomes equal to or greater than 700 W/m². Due to the Clausius-Clapeyron equation, the latent heat flux to the atmosphere (the main part of the flux in the tropics) decreases substantially at lower values of T _s. Thus, an energy flux from the ocean to the atmosphere of 700 W/m² or greater should be regarded as the first necessary condition for TC genesis instead of the temperature T _s. Low static stability, which must be at least half its climatological value as estimated here, is another necessary condition [4]. In polar regions, total fluxes roughly twice those in the tropics are needed for the formation of explosive mesocyclones, PLs, which is explained by the much smaller role of latent heat, greater geostrophicity, and stronger static stability of the atmosphere there. Enthalpy fluxes and wind speeds are interrelated: the larger the flux is, the stronger the convection, the higher the concentration of angular momentum in an ascending convective air column, and the greater the azimuthal velocity in the vortex are, which in turn enhances the transfer of energy from the ocean. Considering the problem with the use of simple analytic relations makes it possible, for the first time, to find a numerical criterion for their generation. It is hoped that this material may be useful for educational purposes as well.     

A calculation method of the sensible heat flux by sodar

- During the second course of USA - PRC joint air sea interaction experiment in 1986, the temperature structure parameters CT2 were measured by sodar over the Western Pacific Ocean. Based on similarity theory, a method is discussed to calculate the sensible heat flux over the ocean in unstable stratification. Becausehumidity is great over the ocean, so we have to consider the influence of water vapor structure parameter Ce2and the correlation coefficient betweene and T on the calculation of sensible heat flux using CT2 profiles measured by sodar. A new formula is suggested in terms of parameterization. The sensible heat flux calculated by sodar measurements is compared with that by bulk transfer method, and the results agree well.     

Interannual variability in the wintertime air–sea flux of carbon dioxide in the northern North Atlantic, 1981–2001

Gridded fields of sea surface temperature (SST), sea level pressure (SLP), and wind speed were used in combination with data for the atmospheric mole fraction of CO₂ and an empirical relationship between measured values of the fugacity of carbon dioxide in surface water and SST, to calculate the air–sea CO₂ flux in the northern North Atlantic. The flux was calculated for each of the months October–March, in the time period 1981 until 2001, allowing for an assessment of the interannual variations in the region. Locally and on a monthly time scale, the interannual variability of the flux could be as high as ±100% in regions seasonally covered by sea ice. However, in open-ocean areas the variability was normally between ±20% and ±40%. The interannual variability was found to be approximately halved when fluxes averaged over each winter season were compared. Summarised over the whole northern North Atlantic, the air to sea carbon flux over winter totalled 0.08 Gton, with an interannual variability of about ±7%. On a monthly basis the interannual variations were slightly higher, about ±8% to ±13%. Changes in wind speed and atmospheric fCO₂ (the latter directly related to SLP variations) accounted for most of the interannual variations of the computed air–sea CO₂ fluxes. A tendency for increasing CO₂ flux into the ocean with increasing values of the NAO index was identified.     

2010年马卡罗夫海盆冰站观测期间垂向热通量时间变化研究

Based on hydrographic data obtained at an ice camp deployed in the Makarov Basin by the 4th Chinese Arctic Research Expedition in August of 2010, temporal variability of vertical heat flux in the upper ocean of the Makarov Basin is investigated together with its impacts on sea ice melt and evolution of heat content in the remnant of winter mixed layer(r WML). The upper ocean of the Makarov Basin under sea ice is vertically stratified. Oceanic heat flux from mixed layer(ML) to ice evolves in three stages as a response to air temperature changes, fluctuating from 12.4 W/m2 to the maximum 43.6 W/m2. The heat transferred upward from ML can support(0.7±0.3) cm/d ice melt rate on average, and daily variability of melt rate agrees well with the observed results. Downward heat flux from ML across the base of ML is much less, only 0.87 W/m2, due to enhanced stratification in the seasonal halocline under ML caused by sea ice melt, indicating that increasing solar heat entering summer ML is mainly used to melt sea ice, with a small proportion transferred downward and stored in the r WML. Heat flux from ML into r WML changes in two phases caused by abrupt air cooling with a day lag. Meanwhile, upward heat flux from Atlantic water(AW) across the base of r WML, even though obstructed by the cold halocline layer(CHL), reaches0.18 W/m2 on average with no obvious changing pattern and is also trapped by the r WML. Upward heat flux from deep AW is higher than generally supposed value near 0, as the existence of r WML enlarges the temperature gradient between surface water and CHL. Acting as a reservoir of heat transferred from both ML and AW, the increasing heat content of r WML can delay the onset of sea ice freezing.     

How storm size matters for surge height

The observed trend of peak storm surge η_max increasing with storm size R_max, roughly as η_max ∞ R_max^0.22, particularly on gently sloping coasts, is discussed in relation to the simple 1D analytical solutions for forced long waves due to respectively surface pressure p_s and wind stress τ_w. At constant depth h, the τ_w-driven surge is proportional to storm size while the p_s-driven part is not. This could perhaps be seen to explain why the size-dependence is stronger on flatter slopes where the τ_w-driven surge dominates. However, this direct size dependence disappears in the sloping beach scenario if the typical depth is assumed proportional to storm size. The observed size dependence is then more likely due to a combination of two 2D effects: Firstly, the sideways radiation from a travelling surge which exceeds the “stationary height” Δ_p/ρg is relatively weaker for a wider system. Secondly, the wind stress field is a dipole, and the mutual cancellation of the two poles is weaker for larger systems.     

Impact of the Eastern Mediterranean Transient on the distribution of anthropogenic CO2 and first estimate of acidification for the Mediterranean Sea

In the Mediterranean Sea the carbon chemistry is poorly known. However, the impact of the regional and large-scale anthropogenic pressures on this fragile environment rapidly modifies the distribution of the carbonate system key properties like C_T (total dissolved inorganic carbon), A_T (total alkalinity), C_ANT (anthropogenic CO₂), and pH. This leads inexorably to the acidification of its waters. In order to improve our knowledge, we first develop interpolation procedures to estimate C_T and A_T from oxygen, salinity, and temperature data using all available data from the EU/MEDAR/MEDATLAS II database. The acceptable levels of precision obtained for these estimates (6.11 ??mol-kg⁻¹ for C_T and 6.08 ??mol kg⁻¹ for A_T) allow us to draw the distribution of C_ANT (with an uncertainty of 6.75 ??mol kg⁻¹) using the Tracer combining Oxygen, inorganic Carbon, and total Alkalinity (TrOCA) approach. The results indicate that: 1) all Mediterranean water bodies are contaminated by anthropogenic carbon; 2) the lowest concentration of C_ANT is 37.5 ??mol kg⁻¹; and 3) the western basin is more contaminated than the Eastern basin. After reconstructing the distribution of key properties (C_T, A_T, C_ANT) for four periods of time (between 1986 and 2001) along a west-east section throughout the whole Mediterranean Sea, we analyze the impact of the Eastern Mediterranean Transient (EMT). Not only has the concentration of C_ANT increased (especially in the intermediate and the bottom layers of the eastern basin, during and after the EMT), but also the distribution of all properties has been considerably perturbed. This is discussed in detail. For the first time, the level of acidification is estimated for the Mediterranean Sea. Our results indicate that for the year 2001 all waters (even the deepest) have been acidified by values ranging from −0.14 to −0.05 pH unit since the beginning of the industrial era, which is clearly higher than elsewhere in the open ocean. Given that the pH of seawater may affect a very large number of chemical and biological processes, our results stress the necessity to develop new programs of research to understand and then predict the evolution of the carbonate system properties in the Mediterranean Sea.