bluuebunny/crossref_metadata_2025 huggingface dataset:
Geochemical profiles in the central Arctic Ocean: Their relation to freezing and shallow circulation
Authors: Moore R. M. , Lowings Malcolm G. , Tan F. C.
Published: February 2008

Temperature, salinity, nutrient, tritium, and oxygen isotope data collected during the Lomonosov Ridge Experiment along a drift track between the Makarov and Fram Basins over the Lomonosov Ridge are presented. The relationship of these quantities to the processes that maintain the halocline, in particular to the production of more saline waters by addition of brines formed during the freezing of seawater, is described. The results support the idea that the wide continental shelves of the Arctic Ocean play an important role in maintaining the halocline. Appendix table is available with entire article on microfiche. Order from the American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document C82‐001; $2.50. Payment must accompany order.
Initial model results for Arctic mixed layer circulation under a refreezing lead
Authors: Kozo Thomas L.
Published: February 2008

At the temperatures in the Arctic Ocean mixed layer during lead‐induced surface water cooling, convection is primarily salinity controlled owing to continuous brine expulsion from newly forming ice. A nonlinear, time‐dependent, convective model has been developed that simulates existing field data obtained on the circulation characteristics under and near a refreezing lead. The model uses typical Arctic Ocean ambient conditions as initial input and allows for imposition of varying geostrophic currents. The zero geostrophic current (free convective case) model output for typical lead surface salt input resulted in maximum horizontal current velocities of 0.05 m s−1, eddy viscosities on the order of 0.01 m2s−1, average salt fluxes beneath the lead of 3.3×10−5kg m−2s−1, and a subsequent increase in the depth of the mixed layer. The circulation cells are symmetric with respect to the lead axis. Imposition of a cross lead constant geostrophic current shows a resultant circulation cell asymmetry associated with increased salt advection in a forced convective regime.
A decade of stratospheric sulfate measurements compared with observations of volcanic eruptions
Authors: Sedlacek W. A. , Mroz E. J. , Lazrus A. L. , Gandrud B. W.
Published: February 2008

Sulfate aerosol concentrations in the stratosphere have been measured for 11 years (1971–1981) using portions of filters collected by the Department of Energy's High Altitude Sampling Program. Data collected seasonally at altitudes between 13 km and 20 km spanning latitudes from 75°N to 51°S are reported. These data are compared with the reported altitudes of volcanic eruption plumes during the same decade. From this comparison it is concluded that (1) several unreported volcanic eruptions or eruptions to altitudes higher than reported did occur during the decade, (2) the e‐fold removal time for sulfate aerosol from the stratosphere following the eruption of Volcan Fuego in 1974 was 11.2±1.2 months, (3) the volcanic contribution to the average stratospheric sulfate concentration over the decade was greater than 50%, and (4) there may be evidence for an anthropogenic contribution to stratospheric sulfate that increases at the rate of 6 to 8% per year.
Initial observations of the subsurface structure and short‐term variability of the seaward deflection of the Gulf Stream off Charleston, South Carolina
Authors: Bane John M.
Published: February 2008

A recurring seaward deflection of the surface layer of the Gulf Stream has been observed near 32°N latitude off the coast of the southeastern United States. It has been suggested that a ridge and trough bottom feature (the so‐called ‘Charleston bump’) on the upper continental slope off the Georgia/South Carolina coast produces the deflection through a bottom steering effect. Present data indicate that the deflection is great enough to direct the Gulf Stream's shoreward surface thermal front to the east, and even south of east, about 70percnt; of the time. Air‐deployed expendable bathythermograph surveys have been made with sufficient coverage to provide several synoptic, three‐dimensional views of the Gulf Stream's thermal frontal zone in the region between Savannah, Georgia, and Cape Hatteras, North Carolina. These views show the subsurface structure of the seaward deflection to exhibit large short‐term variability. During wintertime conditions (February 1979) the greatest deflection (>090° true) of the near‐surface front occurred at a time when the deeper front was more aligned (∼080° true) with local topography. Within the few days following this observation the deflection angle at all depths decreased to near or below 070° true. Two large‐amplitude Gulf Stream meanders progressed northeastward away from the deflection region during this time period. Deflection angles at all levels during late summertime conditions (November 1979) were observed to be near 070° true. A simple, kinematical model which incorporates growing, propagating Gulf Stream meanders is proposed to explain the deflection's short‐term variability. A dome‐shaped volume of cold water was observed to be located over the upper continental slope immediately downstream of the deflection. The existence and persistence of this cold dome suggest that upwelling is important in its maintenance, a hypothesis consistent with its hydrographic properties.
A dynamic model for the production of H+ NO3−, and SO42− in urban fog
Authors: Jacob Daniel J. , Hoffmann Michael R.
Published: February 2008

The chemical composition of nighttime urban fog has been investigated using a hybrid kinetic and equilibrium model. Extremely high acidity may be imparted to the droplets by condensation and growth on acidic condensation nuclei or by in situ S(IV) oxidation. Important oxidants of S(IV) were found to be O2 as catalyzed by Fe(III) and Mn(II), H2O2, and O3. Formation of hydroxymethanesulfonate ion (HMSA) via the nucleophilic addition of HSO3− to CH2O(1) significantly increased the droplet capacity for S(IV) but did not slow down the net S(IV) oxidation rate leading to fog acidification. Gas phase nitric acid, ammonia, and hydrogen peroxide were scavenged efficiently, although aqueous phase hydrogen peroxide was depleted rapidly by reduction with S(IV). Nitrate production in the aqueous phase was found to be dominated by HNO3 gas phase scavenging. Major aqueous phase species concentrations were controlled primarily by condensation, evaporation, and pH.
Equatorial ozone characteristics as measured at Natal (5.9°S, 35.2°W)
Authors: Kirchhoff V. W. J. H. , Hilsenrath E. , Motta A. G. , Sahai Y. , Medrano‐B R. A.
Published: February 2008

Ozone density profiles obtained with ECC balloon sondes during the first 3 years of a joint INPE/NASA long‐term program of measurements at Natal have been analyzed. Ozone variations with time, as expected, are small. A correlation analysis of ozone and temperature profiles taken concurrently indicates a small correlation coefficient in the troposphere, a positive and increasing correlation between the tropopause and the ozone peak, turning negative above it. Outstanding features of the data are tropospheric densities substantially higher than those measured at other low latitude stations and also a total ozone content that is higher than that given by satellite measurements.
The “insulating” effect of a steep continental slope
Authors: Csanady G. T. , Shaw Ping Tung
Published: February 2008

Geochemical evidence shows that the midcontinental slope off the Mid‐Atlantic Bight constitutes an important sink for substances attached to fine particles. It is reasonable to infer that near‐bottom currents in this region are generally much weaker than those over the adjacent continental shelf, allowing the settling out of fine particles and their incorporation into permanent sediment. A partial dynamical explanation of this phenomenon may be sought in the “insulating” effect of a steep slope. At levels below the main thermocline the bottom pressure perturbation associated with steady flow is governed by a parabolic equation which expresses vorticity tendency balance between bottom stress curl and vortex stretching. A heat conduction analogy is appropriate, in which the friction coefficient corresponds to conductivity and the bottom slope corresponds to heat capacity. Over the continental slope the latter is large, suppressing pressure gradients originating from the shelf. Thus steady, near‐bottom currents over the middle slope are generally weak. Exceptions to this rule are locations subject to intense winter cooling and deep convection, which may generate strong thermohaline near‐bottom flow. Oscillatory motions of importance (which may be taken to be coastally trapped waves and topographic waves propagating shoreward from deep water) are weak partly because an efficient local generation mechanism is lacking. Disturbances originating from the Gulf Stream decay as the depth reduces below 3 km, by a mechanism the details of which are not clear at present. The findings in the Mid‐Atlantic Bight are likely to apply to other continental slopes distant from western boundary currents and not subject to intense winter cooling.
A study of the optical characteristics of the suspended particles in the benthic nepheloid layer of the Scotian Rise
Authors: Spinrad Richard W. , Zaneveld J. Ronald V. , Kitchen James C.
Published: February 2008

Light transmission profiles have been used to study the optical properties of the suspended particles which are characteristic of the area of the Scotian Rise in the North Atlantic Ocean. This area is typified by very strong bottom currents and a highly variable bedform morphology. A good correlation (r = 0.96) has been found between the suspended volume and the light beam attenuation coefficient. This correlation is consistent with the fact that the cumulative slope of the hyperbolic particle size distribution is nearly constant throughout the region (slope = 3.1 ± 0.3). Numerical analysis of the optical data in conjunction with particle size analysis yields values of the index of refraction of the suspended particles of 1.20±0.07 relative to water. The conclusion drawn from these results is that the Scotian Rise benthic zone is characterized by suspended particles of high relative index of refraction and size distributions which do not vary much with altitude above bottom or over periods of time of more than a year in spite of the extensive fluctuations in activity of the region.
Chemical accumulation variations under the Peru Current during the past 130,000 years
Authors: Boyle Edward A.
Published: February 2008

The titanium to aluminum ratio in core V19–29 is correlated with aluminosilicate accumulation rates. This correlation may be due to Pleistocene eolian transport fluctuations which alter the mean grain size of sedimented eolian material. The relation between aluminum accumulation rate and Ti/Al, established from accumulation rates integrated over 11,000–50,000 year intervals, can be inverted to compute a high‐resolution record of aluminosilicate and calcium carbonate accumulation rates over the past 130,000 years. Carbonate accumulation rates are closely related to the oxygen isotope record in the core, with a phase lag and damping constant that is compatible with the response time (shown to be only 6000 years) of calcium carbonate in the ocean. Carbonate sedimentation at this site responds to several processes independently correlated with climatic change. The relative importance of these processes for carbonate sedimentation at this site can be constrained by the record in this core and other lines of evidence: 15% of the increased carbonate deposition at this site during glacial periods may be due to diminished NADW (North Atlantic deep water) formation; 10% is due to carbonate productivity decreases in the North Atlantic; 25% may be due to a diminished shallow‐sea carbonate sink; and the residual 50% must be due to a local productivity increase. These assignments are consistent with observations on carbonate paleoceanography in the North Atlantic. Aluminosilicate accumulation rate variations correlate with the record of eolian quartz deposition near northwest Africa and, in a general way, with the climatic record. But in detail the record differs substantially from the oxygen isotope record and may provide independent evidence on the nature of climate dynamics.
A coupled climate‐ice sheet model applied to the Quaternary Ice Ages
Authors: Pollard David
Published: February 2008

A coupled climate‐ice sheet model is used in an attempt to simulate the northern hemispheric ice‐sheet volume variations implied by deep‐sea core records over the last several 105 years. The climate model consists of a global one‐level diffusive energy‐balance equation with seasonal variation and land‐ocean contrast, using a severely truncated series of associated Legendre functions. The ice‐sheet model uses a standard vertically averaged flow law and predicts ice thickness in a north‐south cross section; bedrock deformation under the ice is included as linear flow confined to a thin asthenospheric channel. The climate model is tuned to the modern climate and tested against results from atmospheric general circulation models for 18,000 and 10,000 yr B.P. It is suggested that the lack of sea‐ice variations causes the biggest departures from the GCM results. The sensitivities to the orbital perturbations of the coupled model and of the ice‐sheet model alone with a prescribed snow‐budget distribution are examined. Some qualitative differences are found in the latitudinal forms of these sensitivities. Despite these differences, however, the two types of models produce similar ice‐age simulations over the last 700 thousand years in response to the orbital perturbations. In particular, fairly realistic simulations with strong 100 Kyr cycles similar to those obtained by adding an ice‐calving mechanism to the ice‐sheet model in Pollard (1982a) are again produced in the coupled model.
The Atmospheric Lifetime Experiment: 4. Results for CF2Cl2 based on three years data
Authors: Cunnold D. M. , Prinn R. G. , Rasmussen R. A. , Simmonds P. G. , Alyea F. N. , Cardelino C. A. , Crawford A. J.
Published: February 2008

Observations of dichlorodifluoromethane obtained several times daily over the period July 1978 to June 1981 at Adrigole, Ireland (52°N, 10°W), Ragged Point, Barbados (13°N, 59°W), Point Matatula, American Samoa (14°S, 171°W), and Cape Grim, Tasmania (41°S, 145°E), are reported. Observations at Cape Meares, Oregon (45°N, 124°W), are also given for the period November 1980 to June 1981. On January 1, 1980, the average mixing ratio of dichlorodifluoromethane in the lower troposphere is estimated to have been 285 pptv and to have been increasing at 6.0%/year. The atmospheric lifetime of this compound is estimated from this data by adjusting its destruction rate in a two‐dimensional model of the atmosphere so as to provide the best fit to the observations. Assuming destruction of CF2Cl2 in the stratosphere only, the lifetime estimate for January 1, 1980, by the inventory technique is 69+36−18 years. The trend technique principally provides a lower limit to the lifetime of 81 years. The results suggest a need for further assessment of dichlorodifluoromethane release estimates, particularly those from the USSR and eastern Europe.
A theoretical model of the optical properties of sea ice in the visible and near infrared
Authors: Grenfell Thomas C.
Published: February 2008

A radiative transfer model is presented that makes it possible to calculate the interaction between sea ice and solar radiation from the near ultraviolet to 2750 nm as a function of the physical characteristics of the ice. The bubble density and brine distribution are related to the ice salinity, temperature, bulk density, initial growth rate, and thermal history. Spectral albedos and corresponding asymptotic extinction coefficients are presented for a representative range of initial formation conditions and subsequent temperature variations. A comparison is made with observations for conditions where the ice can be approximated by a single homogeneous layer, and theoretical and observational results are found to be in agreement. Of particular significance is that the wavelength dependence for both albedos and extinction coefficients appears to be accurate. For more general application, however, a multilayer model is needed
Sea ice structure and biological activity in the Antarctic marginal ice zone
Authors: Clarke D. B. , Ackley S. F.
Published: February 2008

Ice cores obtained during October‐November 1981 from Weddell Sea pack ice were analyzed for physical, chemical, and biological parameters. Frazil ice, which is associated with dynamic, turbulent conditions in the water column, predominated (70%). Both floe thickness and salinity indicate ice which is less than 1 year old. Chemical analyses, particularly with regard to the nutrients, revealed a complex picture. Phosphate values are scattered relative to the dilution curve. Nitrate and silicate values are lower than expected from simple scaling with salinity and suggest diatom growth within the ice. Nitrite values are higher in the ice than in adjacent waters. Frazil ice formation which probably concentrates algal cells from the water column into ice floes results in higher initial chlorophyll a concentrations in the ice than in adjacent waters. This mechanical concentration is further enhanced by subsequent reproduction within the ice. Ice core chlorophyll ranged from 0.09 to 3.8 mg/m3, comparable to values previously reported for this area but significantly lower than values for Antarctic coastal fast ice. The dominance of frazil ice in the Weddell is one of the major differences between this area and others. Consequently, we believe that ice structural conditions significantly influence the biological communities in the ice.
Concentration gradients and growth/decay characteristics of the seasonal sea ice cover
Authors: Comiso J. C. , Zwally H. J.
Published: February 2008

The growth and decay characteristics of sea ice in the northern and southern hemispheres are presented quantitatively by using brightness temperature data from the Nimbus 5 Electrically Scanning Microwave Radiometer. The areal extent of >15% ice cover follows a basically symmetrical seasonal cycle in the northern hemisphere, ranging from 8×106 km2 in summer to 16×106 km2 in winter. In contrast the seasonal cycle in the southern hemisphere is asymmetrical, with longer periods of growth than decay and areal extent ranging from 4×106 km2 in summer to 20×106 km2 in winter. At different longitudes the occurrences of the maximum rates of advance of the ice edge differ by up to 2 months, and similarly for retreat. The distribution of the rate of change in the latitudinal position of the ice edge, using as a reference point the 50% ice concentration line near the ice‐ocean boundary, follows a quasi‐Gaussian function with peak at about 60 km/month and with a standard deviation of about ±120 km/month. However, for some months, rates as large as a 940‐km/month change in the latitudinal position are observed when the movement of the ice edge tends to be in the eastward or westward direction as, for example, in the Weddell Sea. The gradient of ice concentration near the ice edge has considerable variability, following a Poisson distribution with peaks at about 0.89% ice concentration per kilometer as derived from the 3‐day averages and 0.62% ice concentration per kilometer from the monthly averages. During the growth cycle, the dominant change in ice cover is the advance of consolidated ice behind the advancing ice edge, while during decay the retreat of the ice edge is accompanied by massive reduction of ice concentration within the ice pack. The monthly changes in ice edge position in the southern hemisphere are also shown to have good correlation with the rates of advance and retreat of the 271 K surface temperature isotherms inferred from climatological temperature data.
An estimate of the mean field of Arctic sea ice motion
Authors: Colony R. , Thorndike A. S.
Published: February 2008

The observational basis for our understanding of sea ice motion comes from the trajectories of particular ice floes. These ice floes may have been marked by a manned research station or, more recently, by an automatic data buoy. Since 1893, almost 100 station‐years of drift data have been recorded. Using the principles of optimal linear estimation, these data are used to obtain a quantitative estimate of the field of mean motion.
Momentum transport in thermohaline staircases
Authors: Ruddick Barry R.
Published: February 2008

Given the fine‐scale temperature and salinity in an actively convecting thermohaline staircase, can the average eddy viscosity be estimated? A simple model for momentum transport in such a system shows that the average dissipation and viscosity are controlled by the regions of high dissipation and small eddy viscosity, i.e., the interfaces. The model results are combined with a mechanistic argument for momentum transport across the interfaces by convection‐driven internal waves. The average eddy viscosity for the staircase is about 40Jb/N2, where Jb is the buoyancy flux, and NM is the buoyancy frequency. By definition the eddy diffusivity of the staircase is −Jb/N2, and so the turbulent Prandtl number is constant and equal to −40. The model predictions are consistent with dissipation measurements in the Bahamas by Larson and Gregg (1983) and imply eddy viscosities of about 10−3 m2/s.
Setup and swash on a natural beach
Authors: Holman R. A. , Sallenger A. H.
Published: February 2008

Wave setup and swash statistics were calculated from 154 runup time series measured on a moderately steep beach under incident waves varying from 0.4 to 4.0 m significant wave height. When scaled by the incident wave height, setup, swash height, and total runup (the sum of setup and half the swash height) were found to vary linearly with the surf zone similarity parameter ξ0 = β(H0/L0)−1/2. The foreshore slope appeared the appropriate value for the calculation of ξ0, although the setup data showed some influence of an offshore bar at low tide. For low Irribaren numbers the swash height in the incident frequency band becomes saturated, while for high Irribaren numbers, no such signs of saturations were seen. Thus the infragravity band appears to become dominant in the swash below some value of ξ0. For these data, that value is approximately 1.75, although there is considerable scatter associated with that estimate.
A three‐dimensional analysis of marine radar images for the determination of ocean wave directionality and surface currents
Authors: Young I. R. , Rosenthal W. , Ziemer F.
Published: February 2008

A series of spatial wave images recorded by a conventional marine radar is analyzed to determine the three‐dimensional E(kx, ky, ω) spectrum. In the absence of a surface current the spectral energy in this three‐dimensional wave number frequency space will lie on a shell defined by the dispersion relationship. Any deviation from the expected dispersion relationship can be interpreted as being due to a current induced Doppler shift of the wave frequency. A least squares curve fitting technique is used to determine the surface current required to account for the observed Doppler shift. A comparison of the radar determined spectra and surface currents with ground truth data indicates that the radar system and analysis technique produces results consistent with conventional instrumentation.
Estuarine flocs: Their size, settling velocity and density
Authors: Gibbs Ronald J.
Published: February 2008

The size and settling velocity of flocs of suspended sediments from the Chesapeake Bay were measured in laboratory experiments and in the field. The curves between floc diameter and settling velocity showed a non‐Stoke's relationship that was best described by the following: settling velocity (cm/s) = 1.73 (floc diameter, cm)0.78. Furthermore, the relationship between floc diameter and settling velocity indicated that the floe density decreased as the floes increased in size. In addition to changing density, a cylinder shape was found to be the best shape factor.
Long‐wave observations near the Galápagos Islands
Authors: Bernard Eddie N. , Milburn Hugh B.
Published: February 2008

Two bottom pressure recorders were deployed from April to August 1982 at 2.5°S, 95.0°W in 3751‐m water depth and at 0.5°S, 89.5°W in water of 16‐m depth to ascertain the background level of wave energy in the period range of 4–90 min. Preliminary analysis of these data reveals the instrument is capable of detecting: (1) tsunami as small as 1 cm in the open ocean and (2) disturbances from distant hurricanes.
Objective mapping by least squares fitting
Authors: Davis Russ E.
Published: February 2008

The conventional method of mapping a smooth field from noisy observations by fitting to a prescribed set of functions using a least‐square‐misfit criterion does not properly account for observational noise. The alternative procedure of objective mapping (minimum mean square error estimation) requires certain statistical knowledge of the smooth field and this is often unavailable. A method of mapping which removes both these drawbacks is obtained by combining the two procedures. Development of the hybrid elucidates the relationship between function fitting and objective analysis.
Active microwave measurements of Arctic sea ice under summer conditions
Authors: Onstott R. G. , Gogineni S. P.
Published: February 2008

Helicopter‐borne L‐C‐X‐Ku‐band radar backscatter data were acquired over test sites in the region about Saint Patrick Island, Northwest Territory, Canada, during June 1982. It is shown that the microwave response of sea ice is greatly influenced by summer, due to the many changes in properties of the snowpack and ice sheet. Hence the well‐documented winter‐and‐spring microwave response may not be extended into the summer season. In summer, the scattering cross sections of multiyear and first‐year ice become very similar, and their contrast is not only greatly reduced, but exhibits reversals in strength. During the early part of summer, discrimination was similar at all frequencies between 4 and 18 GHz with first‐year ice returns slightly stronger than those of multiyear ice. However, during peak melt, when the first‐year ice was extensively flooded and produced weaker returns than multiyear ice, operation at lower frequencies, especially L‐band, showed a 2–3 dB discrimination advantage. Angles greater than 25° from vertical provided the best contrast.
Energy exchange over Antarctic sea ice in the spring
Authors: Andreas Edgar L. , Makshtas Aleksandr P.
Published: February 2008

In October and November of 1981, during the U.S.‐USSR Weddell Polynya Expedition, we made the first measurements ever of the turbulent and radiative fluxes over the interior pack ice of the Southern Ocean. The daily averaged, surface‐averaged sum of these fluxes—the so‐called balance, which comprises the conductive, heat storage, and phase‐change terms—was positive for all but one day during the cruise: the ablation season had begun. Variability in the sum of the turbulent fluxes produced most of the variability in the balance. And these turbulent fluxes generally correlated with the geostrophic wind—a northerly wind (in off the ocean) transferring heat to the surface, and a southerly wind removing it.
Albedo of a water surface, spectral variation, effects of atmospheric transmittance, sun angle and wind speed
Authors: Katsaros Kristina B. , McMurdie Lynn A. , Lind Richard J. , DeVault John E.
Published: February 2008

Some properties of sea surface albedo have been investigated. (1) With aircraft data of upward and downward hemispheric irradiances in three broad bands of the solar spectrum we have investigated albedo as a function of transmittance (variations in windspeed and solar altitude were small). Transmittance measures the depletion of the solar radiation on its path through the atmosphere. For short solar wavelengths, 0.28–;0.53 μm, surface albedo shows little dependence on transmittance, while for longer solar wavelengths, 0.53–2.8 μm, albedo increases with decreasing transmittance. This behavior results from the observation that the short wavelengths are mostly diffuse for all degrees of cloudiness, whereas longer wavelengths become more diffuse with increasing cloudiness. (2) With measurements from broadband pyranometers on a mast over Lake Washington (Seattle, Washington) and from ships in the North Atlantic and the Tropical Atlantic during summer we have investigated the variation of albedo with solar altitude and transmittance. Our results are in general agreement with those of Payne (1972), but some deviations are indicated at high solar altitudes with low transmittances and for solar altitudes below 20°. The effects of wind speed on normalized albedo measured in the Joint Air‐Sea Interaction (JASIN) experiment agree with previous findings of Payne (1972) and Simpson and Paulson (1979).
Macrozooplankton biomass in a warm‐core Gulf Stream ring: Time series changes in size structure, taxonomic composition, and vertical distribution
Authors: Davis Cabell S. , Wiebe Peter H.
Published: February 2008

Macrozooplankton size structure and taxonomic composition in warm‐core ring 82B was examined from a time series (March, April, June) of ring center MOCNESS (1 m) samples. Size distributions of 15 major taxonomic groups were determined from length measurements digitized from silhouette photographs of the samples. Silhouette digitization allows rapid quantification of Zooplankton size structure and taxonomic composition. Length/weight regressions, determined for each taxon, were used to partition the biomass (displacement volumes) of each sample among the major taxonomic groups. Zooplankton taxonomic composition and size structure varied with depth and appeared to coincide with the hydrographic structure of the ring. In March and April, within the thermostad region of the ring, smaller herbivorous/omnivorous Zooplankton, including copepods, crustacean larvae, and euphausiids, were dominant, whereas below this region, larger carnivores, such as medusae, ctenophores, fish, and decapods, dominated. Copepods were generally dominant in most samples above 500 m. Total macrozooplankton abundance and biomass increased between March and April, primarily because of increases in herbivorous taxa, including copepods, crustacean larvae, and larvaceans. A marked increase in total macrozooplankton abundance and biomass between April and June was characterized by an equally dramatic shift from smaller herbivores (1.0–3.0 mm) in April to large herbivores (5.0–6.0 mm) and carnivores (>15 mm) in June. Species identifications made directly from the samples suggest that changes in trophic structure resulted from seeding type immigration and subsequent in situ population growth of Slope Water zooplankton species.
Atmospheric boundary layer structure and drag coefficients over sea ice
Authors: Overland James E.
Published: February 2008

This paper estimates the air/sea drag coefficient for first‐year ice from recent aircraft measurements and reconciles the range of observed drag coefficients (103CD = 1.2–3.7 referenced to 10 m) for all sea ice types, based on ice roughness and seasonal meteorology. For the purpose of sea ice modeling, it is necessary to define an effective drag coefficient which relates regional stress to regional wind, because sea ice is heterogeneous on scales less than 20 km. Regional stress is influenced by the distribution of surface roughness, the buoyancy flux from quasi‐periodic leads, and external atmospheric conditions, principally the inversion height. 103CD is 1.3–1.5 for smooth ice but is much greater for nonflat surfaces. For wind speeds greater than 5 m/s and air temperatures below freezing, the effective 103CD is 2.5–3.0 for nearly continuous pack ice, such as first‐year ice in seasonal ice zones and central Arctic basin. The range of values of 103CD is 3.0–3.7 for unstable boundary layers typical of off‐ice winds in the marginal ice zone (MIZ) or even greater if the ice has been broken by a recent storm. CD values at the lower end of these ranges are associated with low inversion heights. These coefficients are confirmed by 103CD of 2.9, 2.5, and 3.1 for first‐year sea ice calculated from gust probe data collected by the NOAA P‐3 aircraft, interior to the inner MIZ in the Bering Sea during the Marginal Ice Zone Experiment (MIZEX‐West) in February 1983, and 103CD of 2.6 for the Arctic calculated from Arctic Ice Dynamics Joint Experiment (AIDJEX) aircraft data for February 1976. The effective drag coefficient with the presence of even a small concentration of sea ice is greater than the oceanic value as shown by a 103CD of 2.2 calculated from NOAA P‐3 gust probe data over a 40‐km track of 0.4 ice concentration in the outer MIZ of the Greenland Sea in June 1984 during MIZEX‐84. The relation of surface wind and stress to the geostrophic wind for shallow inversion heights, typical of high latitudes, is reviewed with a turbulent closure atmospheric boundary layer model. The winter Arctic is typified by low inversions (<100 m), low geostrophic drag coefficients, and large geostrophic/surface wind turning angles, with low functional dependence on surface roughness. Seasonal ice zones are typified by a more modest influence of the inversion on boundary layer characteristics.
The evolving structure of an upwelling filament
Authors: Flament Pierre , Armi Laurence , Washburn Libe
Published: February 2008

The evolution of an upwelling filament was studied over a 2‐week period by using satellite infrared images, and its thermohaline structure was mapped in situ. The surface velocity field consisted of a large meander extending offshore for at least 300 km. The northern branch was ∼40 km wide, flowing offshore at a peak velocity of 0.55 m/s; the southern branch was flowing inshore at 0.35 m/s. The offshore transport was more than 106 m3 s−1, larger than the Ekman transport. The meander was unstable to barotropic instabilities at a scale of ∼15 km. From a succession of images a surface convergence γ ≈ 8·10−6 s−1 over 20 km was observed near the sharp front limiting the filament to the south. The ∼350 m width of the front indicates a separation of scales between the large‐scale strain field and the mixed‐layer turbulence parameterized with an eddy diffusion coefficient KH ≈ 0.25 m2 s−1. Thermohaline layers that originated at the convergence near the sharp front suggest a secondary circulation subducting denser waters to the south underneath the lighter northern water.
Eddy kinetic energy distribution in the Southern Ocean from altimetry and FGGE drifting buoys
Authors: Daniault Nathalie , Ménard Yves
Published: February 2008

The eddy kinetic energy distribution in the Southern Ocean has been estimated from Seasat altimeter data available on repetitive orbits during 24 days in September–October 1978 and from 192 free‐drifting buoy trajectories obtained during the First GARP Global Experiment (FGGE) from November 1978 to the first months of 1980. A good spatial coherence is found between the results of these two independent methods in the Southern Ocean from 30°S to 65°S. The distribution shows strong, eddy kinetic activity near the western boundaries (Argentine Basin, Mozambique Plateau, Tasman Sea, etc.) and near topographic features (ridges and continental shelves: Drake Passage, Crozet and Kerguelen plateaus, Macquarie Rise, etc.). At first the ratio between both estimates was found to be very high, with kinetic energy distribution from FGGE drifters being 3 times larger than from the altimeter. After an investigation of the effect of the wind on eddy kinetic energy estimates from drifting buoys it seems that the wind cannot be the main reason for such a large discrepancy. Next, the eddy kinetic energy distribution from drifters was recomputed and processed through a band‐pass filter, in the range 1/6 to 1/24 cycles per day, in order to achieve a better match to the temporal scales explored by Seasat altimeter measurements. Although there still remain some differences between the two distributions, comparable values for mean eddy kinetic energy estimates over the whole Southern Ocean are then found. The remaining differences might be attributed to various sources, one of them being the nonsimultaneity of the two data bases.
Wave energy saturation on a natural beach of variable slope
Authors: Sallenger Asbury H. , Holman Robert A.
Published: February 2008

Time series of flow were measured across the inner surf zone during a storm. These data were used to quantify the dependence of wave height (transformed from measured flow) and velocity on local slope and depth. Similar to previous studies, as incident waves broke and propagated into the surf zone, wave energy became saturated, and wave height was strongly dependent on depth. However, the ratio of rms wave height to local depth (γrms) was found not to be constant but to vary between 0.29 and 0.55; γrmsincreased with local slope and was independent of deepwater wave steepness. Thus the surf zone similarity parameter (the ratio of slope to the square root of steepness) did not adequately parameterize γrms.
The Haida Current
Authors: Thomson Richard E. , Emery William J.
Published: February 2008

We present evidence for a narrow, poleward flowing surface current over the continental slope of northwestern British Columbia and southwestern Alaska. Named for a prominent native Indian tribe of the region, the Haida Current occurs predominantly between October and April. Maximal flow takes place in midwinter from November through February. Characteristic features of the current include a minimal extent of 200–300 km, a width of 20–30 km, a depth scale of 500 m, and near‐surface temperature signatures of up to +1°C within the core of the current, as well as large‐amplitude O(10 km) mesoscale waves and eddies along its flank. The wind stress and alongshore sea surface slope are shown to be the primary driving mechanisms for the current.
Diagnostic study on the vertical circulation and the maintenance mechanisms of the cyclonic gyre in Lake Biwa
Authors: Endoh Shuichi
Published: February 2008

Lake Biwa in Japan has a stable cyclonic gyre during seasons of thermal stratification. A vertical circulation consisting of downwelling in the central area and upwelling near the rim of the gyre is calculated by the diagnostic model. The energetics in the model indicate that this vertical circulation corresponds to the decay process of the gyre. Tracking of drifters in summer supports the presence of a vertical circulation, though its magnitude is about 50% less than that estimated by the diagnostic model. This is explained from the ratio of kinetic energy and available potential energy of the gyre. The realistic value of the vertical eddy viscosity is estimated to be 0.8–2.1 cm2 s−1 in summer. Monthly variations of the horizontal and vertical circulations are calculated by the diagnostic model using the monthly mean density fields. The gyre and the vertical circulation are maximal in September. The characteristic decay time scale of the gyre is estimated to be about 10 days. The effect of topographic differential heating is considered to be one of the maintenance mechanisms of the gyre in early summer, and the wind stress curl to be the important maintenance force for the gyre from late summer to late fall.
Characteristics of Arctic winter sea ice from satellite multispectral microwave observations
Authors: Comiso J. C.
Published: February 2008

Scatter plots of satellite multispectral microwave emissivities at two or three different frequencies and/or polarizations reveal unique clusters that are persistent throughout winter conditions in the Arctic region. Cluster analysis of both global and regional data shows that there are more than one radiometrically different types of multiyear ice in the central Arctic, reflecting the strong effect of volume scattering, which varies with the size and shape of the inhomogeneities in the material as well as with the overall structure and history of formation. Some of the clusters in the central Arctic also exhibit “hook patterns” in 18‐GHz versus 37‐GHz plots, indicating sensitivity to modification of the signature by some surface and subsurface effects at 37 GHz. Sensitivity to snow cover and other surface effects in the first‐year ice region is also evident at 37 GHz. A coplanarity test using three SMMR channels shows the potential as well as limitation of the sensor in discriminating different ice types. However, the capability for accurate determination of sea ice concentration, especially in the central Arctic, is evident from scatter plots of the emissivities using the two polarizations at 37 GHz. The consolidated ice data in the central Arctic form a very compact and linear set of points in these plots, and they slope the same way throughout the winter of 1979 and in other years (1980–1984). An ice concentration algorithm based on the utilization of this slope (∼1.03) is developed that yields retrieved values with an accuracy of about 5% in the central Arctic and 10% in the seasonal sea ice region. The total areal ice extent and actual ice cover were also derived from ice concentrations retrieved by using the algorithm, and the results from several years of midwinter data show a relatively stable ice cover in the northern hemisphere.
On time delays in the nearshore zone between onshore and longshore currents at incident wave frequencies
Authors: Kim Chang S. , Huntley David A.
Published: February 2008

Observations of horizontal velocities just outside the surf zone on two natural beaches show unexpected time lags between the onshore/offshore currents and the longshore currents at incident wave frequencies. These time lags, typically around 20 s, appear to have been first noticed by Katoh (1981) in data from a beach in Japan. A number of possible hypotheses to explain these time lags are examined. Of these, propagation of secondary waves formed by reflection or diffraction at a point alongshore from the measurement site seems most able to explain the observations. This suggests a significance for reflected/diffracted waves, some distance from breakwaters or headlands, which has not previously been recognized in field studies. However, a number of questions remain that will only be resolved by further field data, particularly from beaches far removed from end effects.
Interocean exchange of thermocline water
Authors: Gordon Arnold L.
Published: February 2008

Formation of North Atlantic Deep Water (NADW) represents a transfer of upper layer water to abyssal depths at a rate of 15 to 20 × 106 m3/s. NADW spreads throughout the Atlantic Ocean and is exported to the Indian and Pacific Oceans by the Antarctic Circumpolar Current and deep western boundary currents. Naturally, there must be a compensating flow of upper layer water toward the northern North Atlantic to feed NADW production. It is proposed that this return flow is accomplished primarily within the ocean's warm water thermocline layer. In this way the main thermoclines of the ocean are linked as they participate in a thermohaline‐driven global scale circulation cell associated with NADW formation. The path of the return flow of warm water is as follows: Pacific to Indian flow within the Indonesian Seas, advection across the Indian Ocean in the 10°–15°S latitude belt, southward transfer in the Mozambique Channel, entry into the South Atlantic by a branch of the Agulhas Current that does not complete the retroflection pattern, northward advection within the subtropical gyre of the South Atlantic (which on balance with the southward flux of colder North Atlantic Deep Water supports the northward oceanic heat flux characteristic of the South Atlantic), and cross‐equatorial flow into the western North Atlantic. The magnitude of the return flow increases along its path as more NADW is incorporated into the upper layer of the ocean. Additionally, the water mass characteristics of the return flow are gradually altered by regional ocean‐atmosphere interaction and mixing processes. Within the Indonesian seas there is evidence of strong vertical mixing across the thermocline. The cold water route, Pacific to Atlantic transport of Subantarctic water within the Drake Passage, is of secondary importance, amounting to perhaps 25% of the warm water route transport. The continuity or vigor of the warm water route is vulnerable to change not only as the thermohaline forcing in the northern North Atlantic varies but also as the larger‐scale wind‐driven circulation factors vary. The interocean links within the Indonesian seas and at the Agulhas retroflection may be particularly responsive to such variability. Changes in the warm water route continuity may in turn influence formation characteristics of NADW.
Variations in brightness temperature over cold first‐year sea ice near Tuktoyaktuk, Northwest Territories
Authors: Lohanick A. W. , Grenfell T. C.
Published: February 2008

Microwave radiometric temperature (TB) profiles of first‐year sea ice were obtained along 70‐ to 100‐m traverses, with sled‐mounted radiometers at 10, 18.7, 33.6, and 37 GHz and an effective spot size of 30 cm. Measurements ofTBas a function of nadir angle were obtained at selected sites along the traverses. Snow and ice properties were recorded and correlated with theTBmeasurements to infer the effect of snow cover and ice conditions on the radiometric temperature.TBcorrelated positively with the brine volume profile in the ice at several sites, suggesting that brine volume has a strong effect onTBunder these conditions. An overall statistical comparison of snow thickness withTB, when compared with previously published models, suggests that the effect of snow cover on the microwave transmission coefficient of the snow/ice interface may be an important contribution to the radiometric temperature at these frequencies. A model is proposed to explain the data.
Statistical characterization of sea surface geometry for a wave slope field discontinuous in the mean square
Authors: Glazman Roman E.
Published: February 2008

Statistics of two dimensional wave groups, of steep wave events, and of a cascade pattern manifested in the surface geometry in a developed sea state are derived. However, mathematical theories used to parameterize these as well as many other features of random surfaces have very limited ranges of validity. For example, high‐order moments of wave spectra appearing in the calculations of wave slope statistics cannot be evaluated because of divergence of the corresponding integrals. In the present paper the restrictions are reviewed and the difficulties are shown to be due to a pseudo‐fractal geometry of the sea surface whose spectrum is known only within a limited range of frequency (characterized by either the resolution of a measuring technique or the constraints of a theoretical model). An approach is presented that solves the problem: treating the surface elevation field as specified on a spatial (temporal) running grid, an averaging procedure is developed employing the Taylor microscale as the mesh size. The technique is illustrated by first exposing errors in direct calculations of the effective surface impedance for a coherently reflected L band radio wave. The errors arise from the use of wave spectra whose high‐frequency tail is identified with the Phillips saturation range. The technique is then employed in the study of wave groups and steep waves for a Gaussian, two‐dimensional, time‐varying surface. In particular, it is found that wave groups are not observable in a developed sea. Finally, the theory is applied to estimating breaking wave statistics. A comparison with field observations is presented.