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1.
Isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) and alkenones were analyzed in sediment samples retrieved from Ocean Drilling Program Site 1241 covering the last 150000 years to understand the hydrological evolution of the eastern Pacific warm pool (EPWP). GDGT and alkenone concentrations showed higher values in marine isotope stage (MIS)-2 and MIS-6, which suggests the enhancement of primary production at glacial maxima. $ {\text{TEX}}_{86}^{\text{H}} $ - and $ U_{ 3 7^\prime }^{\text{K}} $ -derived temperature depicted different temperature evolutions. $ U_{ 3 7^\prime }^{\text{K}} $ -derived temperature was marked by small variation during the glacial–interglacial cycles, whereas $ {\text{TEX}}_{86}^{\text{H}} $ -derived temperature showed pronounced glacial–interglacial variation that was similar to Mg/Ca-derived temperature records from nearby cores in the EPWP. Given that enhanced primary production during glacial maxima suggests nutricline shoaling, unchanged $ U_{ 3 7^\prime }^{\text{K}} $ over glacial–interglacial cycles can be interpreted as the shift of alkenone production depth. $ {\text{TEX}}_{86}^{\text{H}} $ seems not to be influenced by glacial–interglacial changes in nutricline depths, recording an integrated temperature in surface and thermocline water. The shallow nutricline in the EPWP during glacial maxima most likely reflected the intense formation of Antarctic intermediate water.  相似文献   

2.
We investigated the spatial distribution of glycerol dialkyl glycerol tetraethers (GDGTs), alkenones, and polyunsaturated fatty acids in particulate organic matter collected at four sites along a depth transect from the continental shelf to the Okinawa Trough in the East China Sea during the spring bloom in 2008. The maximum alkenone concentration appeared in the top 25?m at all sites and the $ U_{37}^{{{\text{K}}'}} $ values were consistent with in situ water temperatures in the depth interval, suggesting that the alkenones were produced mainly in surface water. At the slope and shelf sites, GDGTs in the water column showed a concentration maximum at 74?C99?m depth, and the $ {\text{TEX}}_{86}^{\text{H}} $ agreed with in situ water temperatures, suggesting the in situ production of GDGTs in the depth interval. The low-salinity surface water above 20?m depth was characterized by low GDGT concentrations and low $ {\text{TEX}}_{86}^{\text{L}} $ -based temperatures, suggesting either the production of GDGTs in winter season or the lateral advection of GDGTs by an eastward current. At the slope and Okinawa Trough sites, TEX86-based temperatures were nearly constant in the water column deeper than 300?m and corresponded to temperatures at the surface and near-surface waters rather than in situ temperatures. This observation is consistent with a hypothesis that Thaumarchaeota cells produced in surface waters are delivered to deeper water and also indicates that the residence time of suspended GDGTs in the deep-water column is large enough to mix the GDGTs produced in different seasons.  相似文献   

3.
Izvestiya, Atmospheric and Oceanic Physics - From the ERA5 reanalysis data, the time series of the first coefficients ( $$C_{0}^{0}$$ , $$C_{1}^{0}$$ , $$C_{1}^{1}$$ , $$S_{1}^{1}$$ , $$C_{2}^{0}$$...  相似文献   

4.
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5.
The Practical Salinity Scale (PSS) 1978 is defined only for salinities within the range 2-42. We have investigated the relationship between mass-determined salinity, electrical conductivity, and temperature for salinities between 0 and 2 with the aim of developing an extension to the Practical Salinity Scale 1978. The paper presents our data, on the basis of which the following correction is proposed to extend the validity of the equations defining the scale to the entire 0-42 range:S=summin{i=0}max{5} (a_{i}+b_{i}f(t))R_{t}^{i/2}-frac{a_{0}}{1 + 1.5x + x^{2}}-frac{b_{0}f(t)}{1+y^{1/2} + y + y^{3/2}}wheref(t)=frac{(t-15)}{1 + k(t-15)x=400R_{t}y=100R_{t}and the constanta_{i}, b_{i}, andkare defind by the Practical Salinity Scale 1978.  相似文献   

6.
A statistical model for the time evolution of seafloor roughness due to biological activity is applied to photographic and acoustic data. In this model, the function describing small scale seafloor topography obeys a time-evolution equation with a random forcing term that creates roughness and a diffusion term that degrades roughness. When compared to acoustic data from the 1999 and 2004 Sediment Acoustics Experiments (SAX99 and SAX04), the model yields diffusivities in the range from 3.5$,times {hbox {10}} ^{-11}$ to 2.5 $,times {hbox {10}} ^{-10}~{hbox {m}}^{2} {hbox {s}} ^{-1}$ (from 10 to 80 cm$^{2} {hbox {yr}}^{-1}$), with the larger values occurring at sites where bottom-feeding fish were active. While the experimental results lend support to the model, a more focused experimental and simulation effort is required to test several assumptions intrinsic to the model.   相似文献   

7.
The ratiosZ_{K,t}of electrical conductivities of potassium chloride (KCI) solutions of known concentration (K) to standard seawater at the same temperature have been measured at15degC and24degC for solutions withZ_{k,15}between 0.96 and 1.04. The "normal" concentration (N or K_{N}) givingZ_{N,15}= 1was found to beK_{N} = 32.4356gKCI/kg solution. The effect of temperature onZ_{N,t}was measured over the range15degC to30degC. Equations are given for KCI concentration as a function ofZ_{15}and the inverse function, forZ_{15}/Z_{24}as a function ofZ_{24}(to allow use of a laboratory salinometer for the KCI-seawater comparisons), andZ_{N,t}as a function of temperature.  相似文献   

8.
The ratiosR_{s,t,o}of electrical conductivity of seawater samples of precisely known salinity to standard seawater at the same temperature have been measured over a wide range of salinities from 0 to42permilS and over the full range of oceanic temperatures from -2 to35degC. The samples withS<35permilwere prepared by accurate weight dilution of standard seawater with distilled water. High salinity samples were prepared by fast evaporation of standard seawater and subsequent weight dilution into the already determined <35permilrange. An equation was derived which expresses the S versusR_{s,t,o}relationship very precisely from1-42permiland at all temperatures, i.e.,S = f_{1}(R_{s,t,o}) + f_{2}(R_{s, t,o},t) =Sigma_{n=0}^{5} a_{n}R^{n/2}+ frac{Delta t}{1+kDelta t} Sigma_{n=0}^{5} b_{n}R^{n/2}whereDelta t = t-15degC,R = R_{s, t.o}; only the first termf_{1}is required at15degC. The effeet of temperature on the electrical conductivity of standard seawater was also measured. The ratior_{t}of the conductivity at temperaturetto the conductivity at15degC (C_{35,t, o}/C_{35,15,o}) is very aeenrately expressed by a fourth degree equation int. i.e,r_{t}=Sigma_{n=0}^{4} c_{n}t^{n}These two equations are sufficient for all salinity determinations at normal atmospheric pressure.  相似文献   

9.
Weller??s allometric model assumes that the allometric relationships of mean area occupied by a tree $ \bar{s} $ , i.e., the reciprocal of population density $ \rho $ , $ \bar{s}\left( { = {1 \mathord{\left/ {\vphantom {1 {\rho = g_{\varphi } \cdot \bar{w}^{\varphi } }}} \right. \kern-0em} {\rho = g_{\varphi } \cdot \bar{w}^{\varphi } }}} \right) $ , mean tree height $ \bar{H}\left( { = g_{\theta } \cdot \bar{w}^{\theta } } \right) $ , and mean aboveground mass density $ \bar{d}\left( { = g_{\delta } \cdot \bar{w}^{\delta } } \right) $ to mean aboveground mass $ \bar{w} $ hold. Using the model, the self-thinning line $ \left( {\bar{w} = K \cdot \rho^{ - \alpha } } \right) $ of overcrowded Kandelia obovata stands in Okinawa, Japan, was studied over 8?years. Mean tree height increased with increasing $ \bar{w} $ . The values of the allometric constant $ \theta $ and the multiplying factor $ g_{\theta } $ are 0.3857 and 2.157?m?kg???, respectively. The allometric constant $ \delta $ and the multiplying factor $ g_{\delta } $ are ?0.01673 and 2.685?m?3?kg1???, respectively. The $ \delta $ value was not significantly different from zero, showing that $ \bar{d} $ remains constant regardless of any increase in $ \bar{w} $ . The average of $ \bar{d} $ , i.e., biomass density $ \left( {{{\bar{w} \cdot \rho } \mathord{\left/ {\vphantom {{\bar{w} \cdot \rho } {\bar{H}}}} \right. \kern-0em} {\bar{H}}}} \right) $ , was 2.641?±?0.022?kg?m?3, which was considerably higher than 1.3?C1.5?kg?m?3 of most terrestrial forests. The self-thinning exponent $ \alpha \left( { = {1 \mathord{\left/ {\vphantom {1 {\varphi = }}} \right. \kern-0em} {\varphi = }}{1 \mathord{\left/ {\vphantom {1 {\left\{ {1 - \left( {\theta + \delta } \right)} \right\}}}} \right. \kern-0em} {\left\{ {1 - \left( {\theta + \delta } \right)} \right\}}}} \right) $ and the multiplying factor $ K\left( { = \left( {g_{\theta } \cdot g_{\delta } } \right)^{\alpha } } \right) $ were estimated to be 1.585 and 16.18?kg?m?2??, respectively. The estimators $ \theta $ and $ \delta $ are dependent on each other. Therefore, the observed value of $ \theta + \delta $ cannot be used for the test of the hypothesis that the expectation of the estimator $ \theta + \delta $ equals 1/3, i.e., $ \alpha = {3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-0em} 2} $ , or 1/4, i.e., $ \alpha = {4 \mathord{\left/ {\vphantom {4 3}} \right. \kern-0em} 3} $ . The $ \varphi $ value was 0.6310, which is the same as the reciprocal of the self-thinning exponent of 1.585, and was not significantly different from 2/3 (t?=?1.860, df?=?191, p?=?0.06429), i.e., $ \alpha = {3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-0em} 2} $ . Thus the self-thinning exponent is not significantly different from 3/2 based on the simple geometric model. On the other hand, the self-thinning exponent was significantly different from 3/4 (t?=?6.213, df?=?191, p?=?3.182?×?10?9), i.e., $ \alpha = {4 \mathord{\left/ {\vphantom {4 3}} \right. \kern-0em} 3} $ . Therefore, the self-thinning exponent is significantly different from 4/3 based on the metabolic model.  相似文献   

10.
If knowledge of our theories on the directivity of tsunamis had received worldwide attention, the following operations could have been carried out internationally just after the large earthquake of 19 September 1985 which occurred near Acapulco, Mexico. Having found the great circle, “line S” which is perpendicular to the coast around Acapulco, we could have calculated the angles between line S and line A and between line S and line D, where line A and line D are the great circle connecting Acapulco and Auckland, New Zealand and that connecting Acapulco and Duke of York Island (Chile), respectively. The resultant angles are 30?43′ and 41?49′(>68?48′/2), we could thereafter neglect the eastern half of the offshore energy flux. When we assume that the speed of trans-Pacific tsunami is 400 knots, the probability that the actual tsunami will come earlier than the calculated arrival time proves to be $$\frac{1}{{\sqrt {2\pi } }}\int_{ - {\text{ }}\infty }^{ - {\text{ }}0.689} {e^{ - t^{{2 \mathord{\left/ {\vphantom {2 2}} \right. \kern-\nulldelimiterspace} 2}} } dt = 0.2454} $$ Contact with New Zealand prior to the forecasted arrival time was essential, but the tsunami attention for the Japanese coast was unnecessary. Without such application of our directivity theories, frequent fruitless warnings will be issued for future trans-Pacific tsunamis. Quick improvements in warning procedures are required.  相似文献   

11.
To elucidate the sources and transformations of nitrogen in the South China Sea (SCS), the nitrogen isotopic composition of nitrate (\({\updelta }^{ 1 5} {\text{N}}_{{{\text{NO}}_{ 3} }}\)) was measured in seawater samples from the water column of this marginal sea and the adjacent western North Pacific Ocean (WNP). Comparison of the isotopic signatures from these two locations suggests that the main source of nitrogen into the SCS was nitrate that entered from the WNP through the Luzon Strait. Values of \({\updelta }^{ 1 5} {\text{N}}_{{{\text{NO}}_{ 3} }}\) were generally lower in the SCS than in the WNP, and the \({\updelta }^{ 1 5} {\text{N}}_{{{\text{NO}}_{ 3} }}\) maximum observed in the SCS intermediate water was lower than the corresponding WNP maximum. This pattern is attributed to mixing within the SCS in combination with the outflow of SCS intermediate water to the WNP. A mass balance model indicates that atmospherically derived N (a combined input of new nitrogen from marine N2 fixation and atmospheric deposition) supplied approximately 6% of the particulate nitrogen exported from the euphotic zone to the deep SCS. This supply of isotopically light nitrogen cannot, however, explain the low and downward-decreasing δ15N that has been previously observed in sinking particles of the deep SCS. We propose that an alternative explanation might be a downward-increasing ratio of isotopically light NH4 +-N to organic N due to the degradation of organic N within the sinking particles (i.e., relative enrichment of the NH4 +) and also particle incorporation of excreted ammonium from zooplankton.  相似文献   

12.
Forty-three open-ocean observations of drag coefficients observed at Argus Island Tower near Bermuda by the dissipation technique resulted in constant drag coefficients for mean horizontal wind velocities between 7.8 and10.4 m .s^{1}in good agreement with the larger near-neutral data set of DeLeonibus and Simpson [1] and the neutral data of Large and Pond [2], both of whom observed10^{3}C_{10} = 1.2whereC_{10}is the drag coefficient at l0 m. Ratios of vertical-to-horizontal wind velocity spectral densities averaged over an inertial subrange of 0.8 to 1.6 Hz ranged from 0.7 to 1.07 in agreement with the Busch and Panofsky [3] result that isotropy is approached only when the observation height is much greater than the Nyquist wavelength.  相似文献   

13.
Systems of identical precisely spaced bubbles or similar monopole scatterers in water-e.g., inflated balloons or thin-walled shells-insonified at frequenciesomega_{SR}dose to their fundamental radial resonanceomega_{0}(bubble) frequency may themselves display resonance modes or superresonances (SR's) [1]. Ordinary single-bubble resonances magnify the local free-field pressure amplitudep_{1}by a factor(ka)^{-1},abeing the radius andkthe wavenumber in water: for air bubbles or balloons in water, this factor is of the order of 70. Under SR conditions each member of the system amplifies the local free-field amplitude by a further factor of order(ka)^{-1}. Depending upon geometry and other constraints, the pressure fieldP_{SR}on the surface and in the interior of each scatterer will then be in the range of10^{3}p_{1}to5 times 10^{3} p_{1}. This paper investigates the sensitivity of this phenomenon to small departures from the ideal model. In particular, it examines the effect of small differences in scatter positioning and volumes in the context of an SR system consisting of two bubbles/balloons close to the boundary of a thin elastic plate overlying a fluid half-space. It is found that, to observe the SR phenomenon, radii and positions should be controlled to within approximately 1/2 percent.P_{SR}is also sensitive to the angle of incidence of the plane wave train. For the simple system examined here, this sensitivity is considerable for either flexural wave trains or volume acoustic waves incident upon the bubble/ balloon pair (doublet). Practical uses of the phenomenon may range from the design of passive high-Qacoustical filter/amplifiers and acoustical lenses to improved source efficiencies.  相似文献   

14.
Rationale for the measurement of open-ocean tsunami signatures are presented, and available pertinent data are reviewed. Models for tsunami signature and background noise are proposed in order to synthesize an optimum tsunami receiver. Using these models, the minimum tsunami amplitude (in cm) to yield the probability of correct tsunami detectionP_{D} = 0.999and probability of false alarmP_{F} = 10^{-3}is found to be0.718/sqrt{f_{0}}, wheref_{0}is the tsunami dominant frequency (in cycles/h). A realizable receiver is proposed and its performance is evaluated using actual tsunami signatures. It is demonstrated that the detection of a tsunami with an average amplitude as small as 0.7 cm is possible for theP_{D}andP_{F}as above. Simulation results using synthesized background noise are shown. Tidal effects on the receiver performance also are considered and are found negligible for a certain range of the receiver parameters, resulting in a considerable reduction of the signal processing required.  相似文献   

15.
地图网络数学定义的研究   总被引：3，自引：0，他引：3       下载免费PDF全文
根据拓扑学中网的数学定义,证明了收敛于xi∈A belong to X的网{xia）和收敛于xi的地图符号qgf（xi）的网{qgf（xi）a）的存在,推导了可表达坐标网、水网、道路网等多种地图网络的数学定义。  相似文献   

16.
The development of the AIRS (EOS/Aqua) and IASI (MetOp) satellite hyperspectral IR sounders opens new opportunities for determining the average tropospheric carbon dioxide concentration (XCO2 X_{CO_2 } ) and total methane content (QCH4 Q_{CH_4 } ) in the atmosphere from large distances, which is important in climatic studies and since the ground network for CO2 and CH4 observations is scarce. The improved scheme for XCO2 X_{CO_2 } retrieval from the AIRS data, which was used to construct the XCO2 X_{CO_2 } spatial distribution based on the AIRS data for July 2003 and 2010 covering Siberia, is presented. A similar methodology was also used to retrieve instantaneous XCO2 X_{CO_2 } values from the cloud-cleared IASI data for July 7, 2008 and the YAK-AEROSIB experimental region. A comparison of the satellite data with quasi-synchronous aircraft observations gives an error of about 2.2 million−1. The iterative physical algorithm was developed in order to retrieve QCH4 Q_{CH_4 } . The efficiency of the proposed algorithm was estimated during the experiments with actual IASI data covering the Siberian region during several days in July 2008. The QCH4 Q_{CH_4 } estimates were validated by comparing them with the spatially superimposed and quasi-synchronous QCH4 Q_{CH_4 } , estimates based on the AIRS data. The standard deviations of both types of estimates are not more than 3%.  相似文献   

17.
To estimate benthic denitrification in a marginal sea, we assessed the usefulness of \({\text{N}}_{2}^{*}\) , a new tracer to measure the excess nitrogen gas (N2) using dissolved N2 and argon (Ar) with N* in the intermediate layer (26.6–27.4σ θ ) of the Okhotsk Sea. The examined parameters capable of affecting \({\text{N}}_{2}^{*}\) are denitrification, air injection and rapid cooling. We investigated the relative proportions of these effects on \({\text{N}}_{2}^{*}\) using multiple linear regression analysis. The best model included two examined parameters of denitrification and air injection based on the Akaike information criterion as a measure of the model fit to data. More than 80 % of \({\text{N}}_{2}^{*}\) was derived from the denitrification, followed by air injection. Denitrification over the Okhotsk Sea shelf region was estimated to be 5.6 ± 2.4 μmol kg?1. The distribution of \({\text{N}}_{2}^{*}\) was correlated with potential temperature (θ) between 26.6 and 27.4σ θ (r = ?0.55). Therefore, we concluded that \({\text{N}}_{2}^{*}\) and N* can act complementarily as a quasi-conservative tracer of benthic denitrification in the Okhotsk Sea. Our findings suggest that \({\text{N}}_{2}^{*}\) in combination with N* is a useful chemical tracer to estimate benthic denitrification in a marginal sea.  相似文献   

18.
A new portable salinometer has been developed which is based On a direct determination of the conductivity ratioR_{t} = (C_{x}/ C_{s})_{t}of sample(x)to standard(s)seawater in a dual-cell, continuous-flow system. The new salinometer requires only 10 ml of unknown and much less of standard, drawn from the source bottles through fine Teflon tubes, to obtain complete flushing and several repeat readings to the order ofpm0.001, in salinity. The system is autobalancing over the full range of conductivity ratio from 0 to 1.3 and in the future will be direct reading in salinity units. The amount of standard water required is so low that standard water ampoules, at the rate of l/day, can be used as the source. The method used offers a possibility of a direct measurement of salinity in the ocean by measuringR_{t}in situ.  相似文献   

19.
Izvestiya, Atmospheric and Oceanic Physics - The phase shift between changes in the global surface temperature Tg and atmospheric CO2 content $${{q}_{{{\text{C}}{{{\text{O}}}_{2}}}}}$$ has been...  相似文献   

20.
A triaxial set of underwater receiving coils was developed and tested. The receiving system was used jointly with an underwater, calibrated, horizontal, electric dipole source in studies of extremely low-frequency electromagnetic propagation. This paper discusses the electromechanical design of the receiver and tethering system and addresses system sensitivity and noise levels. The receiving system was used successfully in a series of measurements, in spite of serious motion noise contamination. A stationary system sensitivity of5 times 10^{-4} gamma/sqrt{Hz}was achieved.  相似文献   

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