bluuebunny/crossref_metadata_2025 huggingface dataset:
Oceanic turbulence: Big bangs or continuous creation?
Authors: Caldwell Douglas R.
Published: February 2008

In a discussion of the turbulence characteristics of patches of ‘microstructure’ in the ocean, the hypothesis advocated by Gibson (1982), that the patches are produced by very rare but extremely powerful turbulence‐generating events which usually have ‘fossilized’ before their observation, is contrasted with the hypothesis of a turbulence field driven at the time and scale at which it is observed. In this ‘continuous creation’ notion, by no means original here, the driving energy is converted to turbulence kinetic energy in such a way that the observed overturning thickness scale LT is linearly related to the length scale (ε/N3)1/2, where ε is the kinetic energy dissipation rate and N is the buoyancy frequency. (This relationship does not hold in boundary layers, where another length scale, the distance from the boundary, is imposed.) If the time scale of the largest vertical eddies is N−1, the parameters of turbulence and its effects can be estimated by the measurement of N and LT. For example, the kinetic energy dissipation rate would be proportional to LT2N3, and the vertical eddy diffusivity would be proportional to LT2N. Careful attention must be paid to the sampling process and its assumptions. ‘Fossilized’ regions are expected, in the sense that these regions had previously been the sites of turbulence stronger than that present at the time of observation, but consideration of the fossilization process is not necessary for the interpretation of microstructure data.
Fitting of satellite and in‐situ ocean surface temperatures: Results for Polymode during the winter of 1977–1978
Authors: Maul George A. , Bravo Nicolas J.
Published: February 2008

During the POLYMODE experiment, infrared and visible data from GOES were the only satellite data permanently archived in digital form. GOES data lack onboard calibration capability and were fitted, using least squares and other methods, to XBT, buoy, tide gage, and ship of opportunity reports to remove atmospheric effects and calibration offset. For the experiment period considered, December 1977 through February 1978, bivariate Gaussian discriminant function cloud identification showed more than 93% of the 8‐km resolution GOES infrared pixels to be cloud contaminated. Cloud‐free in‐situ calibration points were distributed in nonrandom groups, which resulted in systematic errors when using least squares techniques. Surfaces and regression lines were least squares fitted between satellite and in‐situ data; differences and ratios were also used. Best results were obtained with a regression in the form of the infrared radiative transfer equation but were no better than ±0.9 K. As a result of extensive cloudiness the linear regressions were seldom useful, and temperature ratios with ±1.3 K experimental errors best represent the applicability of GOES data to sea surface temperatures. A composite of all cloud‐free data for the three months left 5% of the area unobserved, but the mean surface temperature map and the standard deviation map are an improvement over atlas maps because of higher spatial resolution.
On interpolating gappy records for time‐series analysis
Authors: Sturges W.
Published: February 2008

For the case of a known data series a Monte Carlo technique is used to estimate how well a cubic spline method will reconstruct the original data when gaps are put in randomly, to allow the use of standard spectral analysis methods. A general result is that the adverse effects of the gaps increase most rapidly for the smallest percentages of data lost. The results depend very strongly on the amount of power in the frequency band of interest relative to the power at other frequencies. For a strong signal, rising well above the background, it was found that a loss of data of ∼20% to 30%, if the length of the holes is only 1/3 to 1/2 the period of interest, will still allow an estimate of phase to ∼10° at the 90% confidence level. The errors associated with loss of data are estimated as a function of the strength of the signal, the size of the gaps, and the amount of data lost
Attenuation of capillary and gravity waves at sea by monomolecular organic surface films
Authors: Hühnerfuss Heinrich , Alpers Werner , Garrett William D. , Lange Philipp A. , Stolte Siegfried
Published: February 2008

During the MARSEN 79 experiment, attenuation of capillary and gravity water waves by two oleyl alcohol and one methyl oleate surface films (‘slicks’) was investigated. A slight influence of an oleyl alcohol slick occurs at frequencies between 0.5 Hz and 0.7 Hz and above 0.7 Hz (wavelength L = 3.2 m) wave attenuation becomes significant. A methyl oleate slick causes only a slight wave damping in the frequency range ƒ<5 Hz (L>6.7 cm). In the capillary wave range ƒ≥14 Hz the wave‐damping characteristics for the two surface film substances are comparable. In the high‐frequency capillary wave range ƒ>20 Hz, however, methyl oleate surface films act more strongly on the wave field, as was demonstrated by additional wind‐wave tunnel experiments. The different wave attenuation characteristics of these two surface active compounds are attributed to different interaction between their hydrophilic part and the adjacent water layer.
The concentration of ammonia in Southern Ocean air
Authors: Ayers G. P. , Gras J. L.
Published: February 2008

Measurements of ammonia gas concentration at Cape Grim (40°41′S, 144°41′E) have been made during six field expeditions between February 1978 and May 1980. For this coastal site a clear distinction between maritime and continental winds was evident in the observed ammonia concentrations. While continental winds gave concentrations comparable with those generally reported in the northern hemisphere (∼1 μg m−3, STP), maritime winds gave much lower concentrations (mean 0.06 μg m−3, STP). No large seasonal trend was apparent in the latter data.
Measurement of monoterpene hydrocarbons at Niwot Ridge, Colorado
Authors: Roberts J. M. , Fehsenfeld F. C. , Albritton D. L. , Sievers R. E.
Published: February 2008

Measurements of atmospheric monoterpene hydrocarbons were made at a site in the Colorado mountains. The research was undertaken to examine the influence of the compounds on the photochemistry of the troposphere. A sampling technique was developed using Tenax GC porous polymer traps with analysis by capillary gas chromatography and detection by flame ionization and mass spectrometry. Positive identification of six monoterpene hydrocarbons, α‐pinene, camphene, β‐pinene, myrcene, Δ‐3‐carene, and d‐limonene, was obtained, as well as tentative identification of α‐thujene and β‐phellandrene. A definite seasonal trend was evident in the average monoterpene mixing ratios. The summertime average was 0.30 ppbv for the sum of the five major identified monoterpenes, β‐pinene, α‐pinene, Δ‐3‐carene, camphene, and d‐limonene, with a high degree of constancy in relative ratios of each throughout the summer months. Wintertime measurements gave mixing ratios below the detection limits (0.001 ppbv of an individual compound). Simultaneous measurements of ozone, NO, NO2, and monoterpene hydrocarbons allowed examination of the contribution of monoterpene photooxidation to ozone production. Based on reported modeling studies, monoterpenes were estimated to be a small source of ozone, insufficient to account for the relatively high ozone mixing ratios (>80 ppbv) sometimes observed at this sampling site.
Nitrogen oxides in the troposphere: Global and regional budgets
Authors: Logan Jennifer A.
Published: February 2008

The cycle of nitrogen oxides in the troposphere is discussed from both global and regional perspectives. Global sources for NOx are estimated to be of magnitude 50(±25)×1012gm N yr−1. Nitrogen oxides are derived from combustion of fossil fuels (∼40%) and biomass burning (∼25%) with the balance from lightning and microbial activity in soils. Estimates for the rate of removal of NOx based on recent atmospheric and precipitation chemistry data are consistent with global source strengths derived here. Industrial and agricultural activities provide approximately two thirds of the global source for NOx. In North America, sources from combustion of fossil fuels exceed natural sources by a factor of 3–13. Wet deposition removes about one third of the combustion source of NOx over North America, while dry deposition removes a similar amount. The balance is exported from the continent. Deposition of nitrate in precipitation over eastern Canada and the western Atlantic is clearly influenced by sources of NOx in the eastern United States. Major uncertainties in the cycle of NOx are attributed to lack of field measurements and inadequate understanding of heterogeneous processes involving NOx.
Winter mixed layer entrainment of Weddell Deep Water
Authors: Gordon A. L. , Chen C. T. A. , Metcalf W. G.
Published: February 2008

Observations from the Somov during the US‐USSR Weddell Polynya expedition show that the mixed layer below the sea ice just prior to the austral spring retreat in the 60°S Greenwich meridian region has an oxygen content of 7.4 ml/1. This is 86% of full oxygen saturation, representing an oxygen deficit, relative to full saturation, of 1.1 ml/1. The source of this deficit is believed to be a consequence of oxygen‐poor (4.5 ml/1) Weddell Deep Water (WDW) entrainment by the winter mixed layer. Assuming effective cutoff of ocean‐atmosphere oxygen exchange by the nearly complete snow and sea ice cover with no net impact of oxygen content as a result of biological factors, a mixing ratio of 1:3 for WDW to “beginning of winter” surface water is required to explain the end‐of‐winter mixed‐layer oxygen content. Accompanying the WDW transfer into the mixed layer is heat transfer of approximately 7×103 cal/cm2 (2.9×108 J/m2) during the five winter months of sea ice coverage as well as salt transfer, which requires 34 cm of fresh water to produce typical mixed‐layer salinity. During the seven ice‐free months when entrainment is expected to be minor, diffusive heat and salt flux continues. A mean annual heat flux of 12 W/m2 is suggested, with an annual demand for freshwater of 46 cm/yr. Consideration of the winter period salinity budget indicates net sea ice melting of 20 cm, which can be attributed to regional convergence of sea ice. The remaining freshwater is derived from excess precipitation and possibly iceberg melt. Oxygen undersaturation of the winter surface water suggests slightly less potential for abyssal water ventilation than might be expected from a fully saturated condition.
Thermohaline stratification below the Southern Ocean sea ice
Authors: Gordon Arnold L. , Huber Bruce A.
Published: February 2008

The end of winter stratification within the cold cyclonic trough of the Weddell gyre near 60°S between 5°E and the Greenwich meridian is resolved with the Mikhail Somov data set. The temperature maximum of the Weddell Deep Water (WDW) is, for the most part, less than 0.5°C, but warmer cells of WDW are found. These warm WDW cells have temperature, salinity, and oxygen properties similar to the WDW characteristic of the Weddell gyre inflow, which is situated to the southeast of the Mikhail Somov study region. The warm WDW cells are accompanied by domes in the pycnocline of 40 m amplitude over the surrounding pycnocline, while deeper isopycnals are depressed. Anticyclonic shear below the 27.83 σ‐θ isopycnal within the warm WDW cells is compensated by the cyclonic shear associated with the pycnocline dome. The pycnocline domes are exposed to about 50% greater entrainment by the turbulently active winter mixed layer, relative to the regional entrainment rate. This entrainment can significantly erode the warm cells in a single winter season, introducing excess heat and salt into the mixed layer. While the heat is lost to the atmosphere, the excess salt is not necessarily compensated by increased fresh water introduction. It is hypothesized that the warm WDW cells within the Weddell gyre trough are derived from instability within the frontal zone which extends from Maud Rise to the northeast, separating the Weddell warm regime from the cold regime. Greater than normal injection of warm WDW cells into the Weddell gyre trough would increase the surface salinity, which would tend to destabilize the pycnocline, increasing the probability of deep convection and polynya events.
Tidal forcing of the water mass interface in the Strait of Messina
Authors: Hopkins Tom Sawyer , Salusti Ettore , Settimi Daniele
Published: February 2008

The tidal currents of the Strait of Messina and their effect on the displacement of the water‐mass interface are discussed utilizing the historical velocity data of Francesco Vercelli, taken from ∼100 anchor stations during 1922 and 1923. The data show a complex, strongly tidal behavior, in which speeds of 200–300 cm/s are attained over the sill. Messina is an amphidromic point for the tides of the two main basins of the Mediterranean Sea, and two distinct water masses flow through the strait at different stages of the tide: the subsurface Levantine intermediate water flowing north alternating with surface Tyrrhenian water flowing south. The time evolution of the interface between the two marine water layers at the semidiurnal periodicity is computed from the observed distribution of acceleration term for the baroclinic component. This interface shows large vertical oscillations with amplitudes of ∼100 m intersecting both the surface and bottom. The results are in reasonable agreement with recent satellite data and other recent field observations and numerical experiments. An estimate of the mean position of the interface is made by assuming that the potential energy required to uplift the interface, from the equilibrium depth of 150 m to the observed 30 m depth over the sill, is derived from the time‐independent contribution of the nonlinear field acceleration term. The results are in reasonable agreement with observations.
Mean circulation and eddy kinetic energy in the eastern North Atlantic
Authors: Krauss W. , Käse R. H.
Published: February 2008

Sixty‐two satellite‐tracked buoys have been released in the northern part of the western and central North Atlantic during 1981 and 1982 by the Institut für Meereskunde, Universität Kiel, Federal Republic of Germany. Additionally, six buoys deployed in spring 1980 by the Bedford Institute have been taken over. Mean values and variances about the mean have been calculated for 3° by 3° areas. The mean velocities confirm the large‐scale gyre circulation as deduced from hydrographie data and numerical models. The center of the gyre is located at about 33°N. Eddy kinetic energy decreases east‐ and southward and is concentrated along the North Atlantic Current. It appears that the North Atlantic Current (Polar Front) is the main source of eddy kinetic energy for the northern North Atlantic, whereas the Mid‐Atlantic Ridge is no source of eddy energy. Eddy kinetic energy along the North Atlantic Current decreases from about 1000 cm2 s−2 near Newfoundland to 300 cm2 s−2 west of Scotland. A homogeneous pool of low eddy kinetic energy (less than 100 cm2 s−2) appears in the central North Atlantic east of the Mid‐Atlantic Ridge. The level increases towards the European and African shelf where the mean southward flow also becomes stronger. The results concern the upper ocean.
On the production and dissipation of mechanical energy in the ocean
Authors: Lueck Rolf , Reid Robert
Published: February 2008

The equation for the conservation of total mechanical energy (kinetic, gravitational, and elastic energy) is derived from the conservation of momentum and mass and averaged over the volume of the oceans to equate the production and dissipation of mechanical energy in a statistically steady ocean. The work done by the atmosphere dominates production and is estimated as 0.1 W/m2 from synoptic data which is consistent with most (but not all) of the reported observations of turbulent dissipation. Potential energy production contributes only .0.2% to the total production implying an eddy diffusivity of buoyancy of 10−5 m2/s and a thermal Cox number of 200. The “low” values of diffusivity derived from microstructure observations appear to reflect a relatively small potential energy production.
Estimates of the joint statistics of amplitudes and periods of ocean waves using an integral transform technique
Authors: Shum K. T. , Melville W. K.
Published: February 2008

An integral transform method is used to obtain continuous time series of wave amplitude and period from ocean wave measurements. The joint statistics of these two variables are determined and directly compared with the theoretical probability densities predicted by Longuet‐Higgins (1975, 1983). Good agreement is found for data from both calm and hurricane sea states. This method avoids the ambiguities in the definitions of wave amplitude and period found in earlier comparisons of field data with theory.
Current and hydrographic variability in the northwestern Gulf of Mexico
Authors: Brooks David A.
Published: February 2008

From July 1980 to February 1981, ten current meters on three moorings were deployed in the 200‐ to 700‐m‐depth range over the continental slope in the northwestern Gulf of Mexico. The currents were characterized by energetic fluctuations with time scales of a week to several months. Westward drifting Loop Current anticyclones provided the principal driving mechanism for the fluctuations. Longshore current speeds at the 200‐m depth occasionally exceeded 70 cm/s and were persistently >50 cm/s during a 2‐month period in the fall. Except during a hurricane, the currents were only marginally coupled with the winds measured at Brownsville, Texas. Tidal motions accounted for <1% of the current variance.
The rotary bottom boundary layer
Authors: Ostendorf David W.
Published: February 2008

We derive a simple analytical model of the boundary layer induced by rotary tidal currents flowing over a horizontal bottom in the absence of strong vertical stratification, formulating explicit estimates of the shear velocity, dissipation, and friction factors relating inviscid velocity to bottom shear stress. Accordingly, these friction factors may be calibrated by an observed velocity profile through the rotary bottom boundary layer, thereby reducing the empiricism of existing depth averaged models of tidal hydraulics. We illustrate the procedure by analyzing measured M2 rotary current profiles on the outer Europeann shelf with good model accuracy; the local dissipation‐based friction factor compares favorably with a global value based upon a calibrated numerical model of the northwest European shelf as well.
Effective diffusivities within oceanic thermohaline staircases
Authors: Kelley Dan
Published: February 2008

A scale for the thickness of layers in regular “diffusive”‐type thermohaline staircases, derived from dimensional analysis, is found to collapse oceanic data. Combining this scale with laboratory‐derived double‐diffusive flux laws, we formulate effective diffusivities for salt, heat, and density. The diffusivities depend on the Turner number Rρ, but are independent of the Brunt‐Vaisala frequency. For Rρ near 1 the diffusivities for salt and heat are approximately equal (≃10−4 m2 s−1). They decrease roughly as Rρ−4 and Rρ−2, respectively, over the oceanic range 1≤Rρ≤10.
Storm surges in the Beaufort and Chukchi Seas
Authors: Kowalik Z.
Published: February 2008

Specific problems of storm surge modeling in the polar seas are analyzed. The vertically integrated equations of motion and continuity are applied to the prediction of the storm surge wave in both the ice‐free and ice‐covered seas. The interactions of atmosphere, ice, and water are expressed by the normal and tangential stresses. A numerical grid is set over the Chukchi and Beaufort seas, and three storm surges are simulated and briefly described. Patterns of motion and sea surface geometry are related to low and high atmospheric pressure systems. Comparison of the measured and computed sea level and observed and computed ice edge proves that the model is suitable to reproduce both water and ice motion.
Sea ice motion as a drunkard's walk
Authors: Colony R. , Thorndike A. S.
Published: February 2008

Observations of sea ice displacement over short periods of time are used to deduce some statistics of the ice motion over long periods of time. The objective is to follow the trajectory of a piece of ice, starting at a randomly selected time and location and ending when the ice either melts or leaves the Arctic Basin. Trajectories are also followed backward in time to the time and location where the piece of ice was formed. Statistical properties considered are the age and remaining lifetime of ice in various locations and the probability that ice presently occupying a particular location was originally created or will ultimately melt in certain regions. Possible applications are to the distribution of pollutants by sea ice and to the design of experiments involving drifting measurement platforms.
Similarity of the wind wave spectrum in finite depth water: 1. Spectral form
Authors: Bouws E. , Günther H. , Rosenthal W. , Vincent C. L.
Published: February 2008

A self‐similar spectral shape (the TMA spectrum) to describe wind waves in water of finite depth is presented. The parametric spectral form is depth dependent and an extension of the deep water JONSWAP spectrum. The behavior of the spectrum in frequency and wave number space is discussed. About 2800 spectra selected from three data sets (TEXEL storm, MARSEN, ARSLOE) are investigated to show the general validity of the proposal self‐similar spectral shape.
SAR imaging of waves in water and ice: Evidence for velocity bunching
Authors: Lyzenga D. R. , Shuchman R. A. , Lyden J. D. , Rufenach C. L.
Published: February 2008

Synthetic aperture radar (SAR) images collected over the Arctic marginal ice zone show gravity wave patterns in both the open water and the ice. Diffuse wave patterns are visible in the water at near range (small incidence angles), while more distinct wave patterns are visible in the ice across the entire swath. The wave patterns in the ice appear as bright lines rather than sinusoidal intensity variations. Additionally, the images show a periodic displacement of the ice/water boundary, apparently due to Doppler shift effects associated with the gravity wave orbital motions. These observations are interpreted as evidence for the velocity bunching effect and also illustrate the effects of random Scatterer motions in the open water.
A numerical model of interactions between a marine ice sheet and the solid earth: Application to a West Antarctic ice stream
Authors: Lingle Craig S. , Clark James A.
Published: February 2008

A time‐dependent numerical model has been constructed that simulates retreat of a West Antarctic ice stream from the edge of the continental shelf during the Holocene period of rising sea level. This paper describes a method for computing the deformation of the solid earth caused by changes in ice and water loading during retreat of the ice stream. The relative sea level changes caused by earth deformation are incorporated as a feedback mechanism in the ice stream model. Elastic and viscous uplift of the earth, caused by thinning of the ice stream and its catchment area, is found to delay retreat of the grounding line relative to computed retreat when the ice stream was assumed to be resting on a rigid earth. Computed retreat of the grounding line began very slowly, at 15,000 B.P., because of rising eustatic sea level. Retreat accelerated after about 30 km, at 13,000 B.P., because of increasing water depth and a seabed sloping down toward the ice sheet interior. By 8000 B.P. the feedback effects of earth deformation caused retreat of the grounding line to be delayed by about 1000 years, relative to computed retreat on a rigid earth. The elastic and viscous earth response exerted a moderating influence on the computed retreat rate because uplift at the grounding line partially counteracted the effect of increasing water depth. Computed retreat of the grounding line slowed, and gradually stopped, near the present position of the ice stream grounding line. Uplift of the seafloor caused the total retreat distance to be reduced by 80 km relative to retreat computed on a rigid earth. A readvance of 20 km of the grounding line occurred between 3000 B.P. and the present because continuing viscous uplift caused sea depth to decrease. Resistance from the Ross Ice Shelf was found to be of primary importance in bringing retreat of the grounding line to a stop in the Ross Embayment, as suggested by earlier investigators. Within the context of a given ice shelf retreat history the feedback effects of earth deformation caused a reduction of the grounding‐line retreat rate, a reduction of the total computed retreat distance, and a readvance of the grounding line after eustatic sea level stopped rising.
On the motion of very small bodies in water waves
Authors: Giménez Curto Luis A.
Published: February 2008

The equation of motion of a small isolated body that moves in translational motion through a fluid which is itself in unsteady and nonuniform motion is established on the assumption that actual forces acting on the body can be split up in gravity; a drag component, which accounts for viscosity and vorticity effects; and an inertial force with the same formal expression as the force that would act on the body if the flow were irrotational (this force is obtained for an unrestricted irrotational flow in the appendix). By assuming that flow acceleration is small compared with that due to gravity and that ϵ =wƒω/g≪ 1, which defines what here is called “very small body” (wƒbeing still water terminal fall velocity, ω angular frequency, andgacceleration due to gravity), some approximate equations are obtained using a perturbation scheme. Subsequently, a simple expression is derived for the leading order approximation of the velocity of very small bodies in water waves. This solution shows that, at least under certain conditions, the hypothesis of some delay time (Kennedy and Locher, 1972) is sound, although this time is not the same, in general, for the vertical velocity component as for the horizontal one. From a practical point of view, owing to the assumptions involved in this derivation, the applicability of the solution must be restricted to suspended sediment particles in low concentrations and to reasonably well‐behaved wave conditions, including superposition of linear waves (particularly standing waves and irregular wave fields), slightly nonlinear waves, and weak currents superimposed on waves. The direct application of the results of this investigation to flows with a high degree of turbulence intensity must be precluded because of the existence of large flow accelerations.
Soluble impurities in the Byrd Station ice core, Antarctica: Their origin and sources
Authors: Palais Julie M. , Legrand Michel
Published: February 2008

Polar ice cores contain long and detailed records of paleoatmospheric composition, paleoclimate, and their evolution through time. By making a complete ionic balance in melted samples of ice, it is possible to evaluate the origin (identification of chemical compounds) and sources (continental, marine, volcanic, extraterrestrial) of soluble impurities contained in these ice cores. Once these are known, an attempt can be made to try and explain the cause of any observed changes. In this paper we present results of analyses of the major soluble impurities (H+, Na+, NH4+, K+, SO4−, NO3−, Cl−) made on bulk samples selected at approximately 50 m intervals down the length of an ice core from Byrd Station, Antarctica (80°01′S, 119°31′W, 1530 m). Most samples are in ionic balance, and it is therefore possible to suggest with which compounds the ionic impurities are linked. These compounds include an important contribution from both sea salts (NaCl and Na2SO4) and strong acids (approximately equal amounts of HNO3 and H2SO4). The Cl/Na mole ratio is found to be quite stable throughout the core and hovers about the expected bulk sea water ratio. In general, the marine‐derived components at Byrd Station decreased by a factor of 2 between the Late Glacial Maximum and Holocene while the gas‐derived acid components decreased by a factor of only 1.5. Some possible causes of these variations are suggested.
Thermohaline circulation in the Arctic Mediterranean Seas
Authors: Aagaard K. , Swift J. H. , Carmack E. C.
Published: February 2008

The renewal of the deep North Atlantic by the various overflows of the Greenland‐Scotland ridges is only one manifestation of the convective and mixing processes which occur in the various basins and shelf areas to the north: the Arctic Ocean and the Greenland, Iceland, and Norwegian seas, collectively called the Arctic Mediterranean. The traditional site of deep ventilation for these basins is the Greenland Sea, but a growing body of evidence also points to the Arctic Ocean as a major source of deep water. This deep water is relatively warm and saline, and it appears to be a mixture of dense, brine‐enriched shelf water with intermediate strata in the Arctic Ocean. The deep water exits the Arctic Ocean along the Greenland slope to mix with the Greenland Sea deep water. Conversely, very cold low‐salinity deep water from the Greenland Sea enters the Arctic Ocean west of Spitsbergen. Within the Arctic Ocean, the Lomonosov Ridge excludes the Greenland Sea deep water from the Canadian Basin, leaving the latter warm, saline, and rich in silica. In general, the entire deep‐water sphere of the Arctic Mediterranean is constrained by the Greenland‐Scotland ridges to circulate internally. Therefore it is certain of the intermediate waters formed in the Greenland and Iceland seas which ventilate the North Atlantic. These waters have a very short residence time in their formation areas and are therefore able to rapidly transmit surface‐induced signals into the deep North Atlantic.
Redfield ratio based on chemical data from isopycnal surfaces
Authors: Takahashi Taro , Broecker Wallace S. , Langer Sara
Published: February 2008

The composition of the organic matter oxidized within the thermocline of the Atlantic and Indian oceans has been estimated from the chemical data along the σθ 27.0 and 27.2 horizons. These estimates are based on the differences between the preformed and observed concentrations of PO4, NO3, total inorganic CO2, alkalinity, and O2. Since these isopycnal horizons are ventilated both from the north and the south, the preformed concentration estimates take into account the relative contributions of these two end‐members. The proportions of these end‐members are estimated on the basis of the potential temperature of the water, assuming that no cross‐isopycnal mixing occurred. Except for the northern Indian Ocean, the composition of the waters entering the isopycnal horizons is established through linear extrapolation of the property‐oxygen trends to oxygen saturation. The σθ 27.0 and 27.2 waters do not outcrop in the northern Indian Ocean, and these horizons receive waters spilling into the Indian Ocean from the Red Sea. Therefore the composition of the Red Sea overflow water with these densities is taken to be the northern Indian end‐member. The results of this study indicate that the accepted Redfield P:N:C: −O2 ratio of 1:16:106:138 requires revision. Our analysis yields a ratio of 1:16:103:172 if the carbon value is represented by the observed increase in the total CO2 concentration. On the other hand, if the carbon value is assumed to be represented by the oxygen utilization minus the oxygen used for oxidation of NH3 with two moles of O2 per nitrogen atom, a ratio of 1:16:140:172 is obtained. Thus the P: −O2 ratio lies between 1:103 and 1:140. This discrepancy may be accounted for by the increased CO2 concentrations in the source waters as a result of the uptake of anthropogenic CO2 or by an excess demand of oxygen for oxidation of hydrogenated organic molecules. Therefore, without a firm knowledge of either the corrections for the anthropogenic CO2 effect or the hydrogen content of the biological residues, the true P:C ratio cannot be obtained. The ratio of P:CaCO3 dissolution has been estimated to be about 1:12. This indicates that the CO2 produced by the oxidation of organic carbon to that derived from the dissolution of CaCO3 is bout 10:1 at these density horizons.
Internal and external sources of mean sea level variations
Authors: Palumbo A. , Mazzarella A.
Published: February 2008

The joint variation of monthly mean sea level, rainfall, and evaporation recorded in Naples and in other western Mediterranean stations is analyzed. The mass balance among sea level, rainfall, and evaporation and the application of the Wiener filter methods show that the major portion of sea level variance concentrated at annual and semiannual components is dominated by evaporation; the effect of rainfall is less than the effect of evaporation; the Atlantic water flux acts as a balancing source of sea level fluctuations among those of rainfall and evaporation.
Some characteristics of internal gravity waves in the equatorial Pacific
Authors: Eriksen Charles C.
Published: February 2008

One‐year moored current and temperature measurements made in the central equatorial Pacific Ocean at subthermocline depths display spectral characteristics at internal gravity wave frequencies which are distinct from those found at mid‐latitudes. These characteristics are meridional orientation of current ellipses, kinetic energy scaling proportional to (buoyancy frequency)1.2, and coherence of zonal current and temperature at phases significantly different then 0° or 180°. Characteristics vary over as little as 100 m vertically but not over 40 km horizontally. Low‐frequency flow is predominantly zonal and shares similar spatial structure, suggesting internal waves are influenced by it. Although horizontal internal wave fluxes cannot be calculated directly from the observations, models provide a framework in which to interpret internal wave spectral characteristics. Models of internal waves near the equator in a resting ocean, an ocean with a uniform zonal current, and an ocean with depth‐dependent zonal current all require wave flux to be horizontally anisotropic in order to obtain current ellipses and zonal current‐temperatures similar to those observed. The model with vertical shear is the most realistic of these three. Observed shears are sufficiently strong to allow the possibility of internal wave critical layers, which in turn are a likely source of both horizontal anisotropy and vertical asymmetry of wave fluxes.
A theoretical model for saltating grains in water
Authors: Wiberg Patricia L. , Smith J. Dungan
Published: February 2008

The equations of motion for a sediment grain near a noncohesive bed and those for the local fluid flow are combined to produce a set of differential equations that can be solved numerically to describe the trajectory of a saltating grain as a function of time. The lift coefficient is set based on a reanalysis of data produced by Chepil, and the other parameters of the problem are set using standard fluid mechanical relationships; the initial velocity and position are specified with a separate model. The heights of the resulting trajectories are found to be significantly lower than available measurements would indicate; therefore two extensions of the model are examined: the effect that spin lift and form lift have on a series of trajectories, and the effect of partially elastic collisions between a moving grain and the bed over which it is traveling. A model that includes the second process is less complicated than one that includes the first, and it yields trajectories that agree very well with available experimental measurements when a rebound coefficient that varies around 0.5 and depends on the impact momentum is used. We conclude that the model provides a reasonable representation of saltation in water and that both fluid‐solid and solid‐solid interactions are required to reproduce the parameters of measured trajectories.
Simulations of acoustic tomography array performance with untracked or drifting sources and receivers
Authors: Cornuelle Bruce D.
Published: February 2008

Ocean tomography as originally proposed required all sources and recievers to be tautly moored and acoustically tracked to separate travel time perturbations due to mooring motion from those due to ocean features. It is possible to process the tomographic travel times to estimate both ocean sound speed perturbations and mooring offsets, effecting a separation without external tracking. A side effect of this processing is a check on the ray identification, since the varying instrument positions can be used as a synthetic array for estimating ray angle. Simulations and examples with actual data were used to contrast mapping performance with and without mooring tracking for a variety of ray data sets. In general, the ocean maps degrade when the tracking data are withheld. However, when many high‐precision ray travel time measurements are available, the degradation is small; in these cases it would be possible to deploy free‐drifting instruments as part of a monitoring experiment.
Calibration of advanced very high resolution radiometer infrared observations
Authors: Brown Otis B. , Brown James W. , Evans Robert H.
Published: February 2008

A detailed analysis of the calibration procedures for the NOAA advanced very high resolution radiometer (AVHRR) based on thermal vacuum test data was performed as part of the Warm Core Rings Experiment. We find systematic differences in the derived calibration results and those reported in the various addenda to work by Lauritson et al. (1979). A weak, but important, dependence in calibration upon internal operating temperature is also observed. Calibration results for various AVHRR radiometers show instrument specific changes in the relative emittance between internal and external calibration targets. A consistent calibration methodology is developed based on this analysis of the thermal vacuum test data. Use of these new results provides an improvement of radiometer calibration at the ±0.2°C level. Such an improvement is quite important to the absolute accuracy of surface thermal fields which are derived from these data utilizing various multichannel atmospheric water vapor correction schemes. Demonstration of such accuracies with presently operational sensors is of importance to climate related studies being planned for the next decade since it shows that appropriate processing can lead to higher‐quality SST fields.
On the role played by upwelling of water in lowering sea surface temperatures during the passage of a storm
Authors: Greatbatch Richard J.
Published: February 2008

This paper examines the role played by upwelling of water and the associated reduction is mixed‐layer depth in lowering sea surface temperatures during the passage of a storm. The important parameter is RU = HU/(HM + Δh). HU measures how much the wind‐mixed layer is shallowed by vertical motion induced by the storm, HM is the undisturbed mixed‐layer depth ahead of the storm, and Δh measures the increase in mixed‐layer depth due to turbulent entrainment of water from below. Suitable quantitative definitions are given for HU and Δh, enabling RU to be calculated. With these definitions, the sea surface temperature decreases found in the three numerical experiments of Chang and Anthes (1978) are shown to be approximately a factor 1/(1 ‐ RU)2 larger than the decrease that is calculated using a one‐dimensional mixed‐layer model with no account taken for advection. The 1/(1 ‐ RU)2 dependence is shown to be a consequence of using the Kraus and Turner (1967) formulation for the wind‐mixed layer.
Geographically correlated orbit error and its effect on satellite altimetry missions
Authors: Tapley B. D. , Rosborough G. W.
Published: February 2008

The orbit accuracies needed to support the global crustal dynamics project and recent satellite altimeter missions have placed unique demands on both the data precision and the analysis systems. These include requirements for accurate and well‐distributed observations, improved computational techniques and substantial enhancements in the force models which describe the satellite's motion. For example, the satellite altimeter mission (TOPEX), whose objectives will be (1) to measure the time variable ocean surface topography and (2) to demonstrate the ability to map the general ocean circulation, requires that the radial component of the satellite's orbit be known with a root‐sum‐square absolute error of 13 cm for the three‐year mission lifetime. The primary force model error, which limits the contemporary orbit computation accuracy, is the inaccuracy in the values assigned to the spherical harmonic coefficients used to model the earth's gravity field. This investigation describes the effects of gravity model errors on previous satellite altimeter missions and looks at the projected effects of current geopotential model errors on future satellite altimeter missions. The investigation demonstrates that (1) the radial orbit error, represented in a geographic sense, will contain a regionally dependent mean and variability, (2) historically, it has not been possible to use conventional ground‐based tracking to remove these effects, and (3) the regionally correlated component can lead to bias in mean ocean surfaces created by minimizing altimeter differences at ground track crossover points. This last effect has been a primary limitation in using satellite altimetry to obtain the long‐wavelength components of the ocean surface topography. The magnitude of the regionally correlated error can be reduced only by improvement in the knowledge of the gravity field. The conclusion reached in this investigation is that an order of magnitude improvement in the accuracy of the earth's gravity field model is required to realize the full potential of the proposed TOPEX altimeter measurements.
The role of plastic ice interaction in marginal ice zone dynamics
Authors: Leppäranta M. , Hibler W. D.
Published: February 2008

Under appropriate conditions, the nonlinear nature of plastic ice interaction together with a nonlinear coupling between ice thickness characteristics and ice rheology can substantially modify the character of marginal ice zone dynamics. This paper examines the steady state ramifications of these nonlinearities by using a one‐dimensional simplification of Hibler's (1979) two‐level viscous plastic sea ice model. A series of idealized small‐scale simulations (4‐km resolution) are carried out with the model formulated in a moving Lagrangian grid in order to remove diffusion effects. Analytic solutions for the equilibrium plastic adjustment case are also constructed. The results show that if the ice thickness distribution is allowed to equilibrate in response to a constant wind field, the thickness strength coupling will yield a sharp ice edge, with the compactness dropping rapidly to zero near the ice margin. Despite this compactness falloff, the steady adjusted ice velocity is nearly constant across the marginal ice zone. However, the adjustment to a steady state constant velocity can be preceded by a period of shearing, which will abate as the ice strengthens by ridging. With an increase in forcing near the edge, the ice velocity scales with the wind velocity but with a speed less than free drift. In the absence of water drag and wind stress the model exhibits a very slow outward creep but yields no ice edge jet effects. The ramifications of plastic interaction on upwelling and downwelling are also examined. With the same drag coefficients over ice and ocean, and for a north‐south ice edge, the model yields (in the northern hemisphere) upwelling for northward winds, downwelling for southward winds, and no effect for off‐ice winds.
Variability of subtidal current structure in a fjord estuary: Puget Sound, Washington
Authors: Bretschneider D. E. , Cannon G. A. , Holbrook J. R. , Pashinski D. J.
Published: February 2008

Simultaneous observations of currents and water properties were made in a section across East Passage in Puget Sound over a 31‐day period between March and April 1983. These observations, supplemented with CTD profiles, shore‐based wind data, and far‐field current measurements, were used to describe the cross‐channel variability of subtidal currents. The mean circulation consisted of seaward flow in the near surface and landward flow below 7 m, with a core of maximum velocity at mid‐depth. Volume transport was 22,000 m3/s. Topographic effects force most of the seaward compensating flow through an adjacent channel, creating a clockwise circulation around an intervening island. Empirical orthogonal function analysis was used to describe the spatial structure of current fluctuations. At subtidal time scales, three circulation modes are evident: (1) a near‐surface (upper 20 m), wind‐driven shear; (2) a near‐bottom layer (150–200 m) dominated by density currents that propagate up estuary after generation during neap tidal mixing at the entrance sill to Puget Sound; and (3) an intermediate layer (25–75 m) influenced by partial refluxing of Colvos Passage water and modulated at fortnightly periods by nonlinear mixed tides. These current observations are the first to show recirculation of seaward flowing water from Colvos Passage to landward flow in East Passage.
On the joint distribution of surface elevation and slopes for a nonlinear random sea, with an application to radar altimetry
Authors: Srokosz M. A.
Published: February 2008

The work of Longuet‐Higgins (1963) on the effects of wave nonlinearity on the statistics of the sea surface is extended here to obtain the joint distribution of surface elevation and slopes for a nonlinear random sea. The results are used to examine the effect of wave nonlinearity on the form of a radar altimeter pulse which is reflected from the sea surface. It is shown how wave information may be derived from the return pulse and how this can be used to correct errors in the altimeter mean sea level estimate (a problem known as “sea state bias”).
Global analysis of ocean surface wind and wind stress using a general circulation model and Seasat scatterometer winds
Authors: Kalnay Eugenia , Atlas Robert
Published: February 2008

We present instantaneous and 15‐day time‐averaged fields of surface wind, wind stress, curl of the wind stress, and wind divergence. These fields are derived from the Goddard Laboratory for Atmospheres four‐dimensional analysis/forecast cycle, for the period September 6–20, 1978, using conventional data, satellite temperature soundings, cloud‐track winds, and subjectively dealiased Seasat scatterometer winds.
Tracing the Amazon component of surface Atlantic water using 228Ra, salinity and silica
Authors: Moore Willard S. , Sarmiento Jorge L. , Key R. M.
Published: February 2008

High 228Ra/226Ra activity ratios characteristic of waters in the Amazon estuary provide a sensitive indicator of the presence of these waters in the Atlantic Ocean. A conservative mixing model utilizing the 228Ra/226Ra activity ratio (AR) tied to absolute measurements in the estuary allows us to estimate that 20–34% of the surface water east of the Antilles during June, 5–9% from the same area during December, and 15–20% of the eastern Caribbean surface water during December are derived from the Amazon estuary. Differences in 228Ra input occur in response to variable stratification of water near the river mouth. During high discharge, intense vertical mixing enriches the water in the estuary in 228Ra. A large fraction of this water moves to the north and east of the Antilles, where its relatively high 228Ra/226Ra AR distinguishes it over 1500 km from its source. During low discharge (northern hemisphere fall) a significant fraction of river water passes northwest of the zone of intense mixing into a vertically stratified region where 228Ra gain is lower. This water is transported by the Guiana Current along the coast of South America and into the Caribbean.