bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutrients in the Atlantic thermocline
Authors: Kawase M. , Sarmiento J. L.
Published: February 2008

A set of maps are presented of nutrient distribution on isopycnal surfaces in the North and tropical Atlantic Ocean main thermocline. The data used in producing these maps are from the Transient Tracers in the Oceans (TTO) North Atlantic Study and Tropical Atlantic Study, an associated German study (Meteor 56/5), two cross‐Atlantic sections from cruise 109 of the Atlantis II, and the GEOSECS program. The nutrient distributions reflect primarily the sources at the northern and southern outcrops of the isopycnal surfaces, the in situ regeneration due to decomposition of sinking organic materials, and the interior physical processes as inferred from thermocline models and the distribution of conservative properties such as salinity. However, silica also exhibits behavior that cannot be explained by in situ regeneration. A simple phenomenological model suggests that cross‐isopycnal advection and mixing in the equatorial region may play an important role in the nutrient dynamics. These data should prove of great value in constraining models of physical as well as biogeochemical processes.
Some observations of ring topography and ring‐ring interactions in the Gulf of Mexico
Authors: Lewis James K. , Kirwan A. D.
Published: February 2008

The movement and interactions of Loop Current rings are studied using trajectory and sea surface temperature (SST) data from the Gulf of Mexico. The movements of three rings as determiend by drifters seeded in the rings are compared. The data show the rings moving west through the deepest portion of the Gulf and then northward after impacting with the Mexican coast. The trajectory data indicate a ring life span of at least 9–13 months, with two of the rings persisting off the Mexican coast for at least 3–5 months. The trajectory of a fourth drifter, not seeded in a ring, still shows strong anticyclonic motion. The SST data for the period that this last drifter was deployed show the interaction of three anticyclones in the western Gulf. The drifter circles all three anticyclones and shows, along with the SST data, the coalescing of two of the anticyclones.
A coupled ice‐ocean model of a wind‐driven coastal flow
Authors: Ikeda Motoyoshi
Published: February 2008

Ice movement driven by winds along the coast is studied using a two‐dimensional (vertical seaward), ice‐ocean coupled model. Right‐hand alongshore winds are given when internal ice stresses are important to determine the ice movement. These winds induce right‐hand coastal currents and ice movement. A shoreward Ekman flow beneath the ice is a major mechanism to constrain the ice over the shelf, balancing the internal ice pressure gradient. When the wind ceases, the ice decreases its alongshore velocity, and the ice‐covered band becomes wider. The alongshore ice velocity is sensitive to ice shear strength, which determines the shear stress at the coast; i.e., weak (strong) shear strength allows a large (small) ice velocity at the coast, resulting in intense (weak) Ekman flow and downwelling, which induces a fast (slow) coastal current. The alongshore velocity is also sensitive to the relatively small cross‐shore component of the wind; i.e., the seaward (shoreward) component reduces (induces) the shear stress and allows large (small) ice velocity. The results are applied to the ice over the Labrador shelf.
Kinematic and dynamic estimates from electromagnetic current meter data
Authors: Aubrey David G. , Trowbridge John H.
Published: February 2008

The dynamic response of electromagnetic current meters (manufactured by Marsh‐McBirney, Inc.) has been clarified through a comprehensive laboratory measurement program combined with a thorough literature review. Elucidation of the behavior of these flow meters under a variety of dynamic conditions has been neglected in the past. Since flow past a spherical body has considerable hydrodynamic complexity for different dynamic conditions, a careful laboratory study was carried out for pure steady, pure oscillatory (horizontal plane), and combined steady/oscillatory conditions at two test facilities. Test results indicate that flow meter behavior under pure steady flow is reasonable in the absence of high levels of free‐stream turbulence, with an rms error of 1–5 cm/s. These errors could be reduced with a higher‐order polynomial regression fit. Pure oscillatory response was also reasonable, with rms errors of 1–2 cm/s, and sensitivity which is correlated with the oscillatory Reynolds number (Re)0, and the Keulegan‐Carpenter number (A/d, where A is the oscillation excursion and d is the probe diameter). Combined steady/oscillatory flows degraded current meter performance with larger residual errors (1–6 cm/s) and significant differences in sensitivity (up to 20%). Horizontal cosine response showed systematic deviations from pure cosine behavior, with a notable intercardinal undersensitivity and cosine “shoulder” at lower Reynolds numbers. Error analysis shows these current sensors are adequate for many kinematic measurements but may lead to excessive errors when using velocity to calculate dynamical quantities (such as bottom friction, Reynolds stress, or log‐layer friction velocities). A careful error analysis must precede any use of these meters for estimating dynamical quantities. These studies pointed out a potential difficulty in using these meters in areas of large ambient turbulence levels (20% turbulent intensities), which are characteristic of many near‐bottom shallow water environments. Further study is needed to clarify this behavior.
Calibration and verification of a dissipation model for random breaking waves
Authors: Battjes J. A. , Stive M. J. F.
Published: February 2008

A model describing the average rate of energy dissipation in random waves breaking in shallow water, published previously by Battjes and Janssen (1978), has been applied to an extensive set of data for the purposes of calibration and verification. Both laboratory and field data were used, obtained on beaches with a more or less plane slope as well as on barred beaches, and for a wide range of wave conditions. Optimal values have been estimated for an adjustable breaking wave height‐coefficient in the model; these appear to vary slightly but systematicaly with the incident wave steepness, in a range that is physically realistic. A parameterization of this dependence allows the use of the model for prediction. Applied to the present data set, the correlation coefficient between measured and predicted rms wave heights is 0.98, with an rms normalized error of 6% and a bias that does not differ significantly from zero.
The role of the ocean in a regional sulfur cycle
Authors: Bates Timothy S. , Cline Joel D.
Published: February 2008

Dimethylsulfide (DMS) concentrations were measured in ocean waters along the West Coast of the United States on three cruises during 1983 and 1984. Concentrations in surface waters ranged from 13 to 380 ng S/L with a summer average of 60 and a winter average of 20 ng S/L. The flux of sulfur from the ocean to the atmosphere was calculated using the stagnant film boundary layer model to be 28 mg S/m2/a. On the basis of a non‐sea salt sulfate residence time of 5 days, the calculated net flux of biogenic sulfur to the West Coast of the United States is 0.045 Tg/a. This is 4–13% of the combined total anthropogenic emissions from the western United States.
Production of global sea surface temperature fields for the Jet Propulsion Laboratory workshop comparisons
Authors: Hilland Jeffrey E. , Chelton Dudley B. , Njoku Eni G.
Published: February 2008

Sea surface temperature (SST) is measured from space by the advanced very high resolution radiometer (AVHRR), scanning multichannel microwave radiometer (SMMR), high resolution infrared sounder (HIRS) and VISSR atmospheric sounder (VAS). Typical accuracies have been reported from 0.5°C regionally to 2.0°C on a global basis. To evaluate the accuracy of the satellite‐derived sea surface, temperatures, a series of three workshops was organized to provide uniform data reduction and analysis. The analytical techniques used to intercompare satellite and in situ measurements are described in detail. Selected results showed the overall average rms errors were in the range 0.5°–1.0°C.
Wave height variation across beaches of arbitrary profile
Authors: Dally William R. , Dean Robert G. , Dalrymple Robert A.
Published: February 2008

An intuitive expression for the spatial change in energy flux associated with waves breaking in the surf zone is developed. Using shallow water linear wave theory, analytical solutions for wave height transformation due to shoaling and breaking on a flat shelf, a plane slope, and an “equilibrium” beach profile are derived and then compared to laboratory data with favorable results. The effect of beach slope on wave decay is included explicitly, while wave steepness effects are included implicitly by specification of the incipient conditions. Set‐down/set‐up in the mean water level, bottom friction losses, and bottom profiles of arbitrary shape are introduced, and solutions are obtained numerically. The model is calibrated and verified using laboratory data with very good results for the wave decay but not so favorable results for set‐up. A test run on a prototype scale profile containing two bar and trough systems demonstrates the model's ability to describe the shoaling, breaking, and wave re‐forming process commonly observed in nature. Bottom friction is found to play a negligible role in wave decay in the surf zone when compared to shoaling and breaking.
New algorithms for microwave measurements of ocean winds: Applications to Seasat and the special sensor microwave imager
Authors: Wentz Frank J. , Mattox L. A. , Peteherych Steve
Published: February 2008

Improved second generation normalized radar cross section (NRCS) and brightness temperature (TB) models and associated wind retrieval algorithms are derived for the Seasat microwave radiometer SMMR and scatterometer SASS. The derivation of the NRCS model is based on the assumption of a Rayleigh distribution of wind speeds, and no in situ anemometer measurements are used. Furthermore, the NRCS model derivation is designed to preclude, as much as possible, systematic errors in the polarization and incidence angle relationships. A constant power law NRCS model is used, except for nadir observations. The nadir NRCS for winds above 15 m/s falls off faster with increasing wind speed than is predicted by a constant power law relationship. The TB model derivation consists of finding the wind‐induced emissivity coefficients, modifying the 37‐GHz atmospheric absorption coefficients and removing biases in the TB observations. The TB biases are found to be stable except for the 18‐GHz channels, which experience large, time‐dependent biases. The NRCS and TB models are incorporated into new wind retrieval algorithms, which are used to process the SASS and SMMR 3‐month data sets. Small residual systematic errors in the SASS winds (±0.5 m/s or less) are found. A histogram of the SASS winds closely resembles a Rayleigh distribution. The SASS winds are compared with 1623 National Data Buoy Office (NDBO) buoy observations, and a 1.6‐m/s rms discrepancy, with a −0.1‐m/s bias, is found. The SASS and SMMR winds are compared on a 150‐km cell‐by‐cell basis, giving 123,000 wind comparisons for the 3‐month period. The comparisons are done using eight different combinations of three SMMR channels. Good agreement is found between the SASS and SMMR winds, except for two of the channel combinations that show little, if any, skill in retrieving wind. Over the SASS primary off‐nadir swath, the SMMR and SASS wind agreement ranges from 1.3 to 2.2 m/s, depending on the channel combination. For the SMMR versus SASS nadir wind comparisons, the agreement slightly degrades. The SMMR winds appear to be more noisy than the SASS winds for winds below 3 m/s. These results indicate that the Special Sensor Microwave Imager (SSM/I), to be launched in 1986, will have the capability to measure the near‐surface wind speed to an accuracy of about 2 m/s.
Observed tides on the northeastern Bering Sea shelf
Authors: Mofjeld Harold O.
Published: February 2008

Bottom pressure observations (November 1981 to August 1982) show that the diurnal tides dominate the outer reaches of the northeastern Bering Sea shelf. The diurnal tides decrease inshore from the shelf break (maximum K1 amplitude of 38 cm) and appear to be evanescent Sverdrup (Poincaré) waves on the outer shelf. The K1 amplitude (2.3 cm) in the Bering Strait is 6% of that at the shelf break. The diurnal phase lags vary little (322°–359°G for the K1 tide) between the stations. North and eastward from the shelf break, the tides become smaller and more semidiurnal. The semidiurnal amplitudes vary considerably between stations; these observations show the effects of semidiurnal amphidromic systems predicted by numerical models. The M2 amplitude (7.6 cm) in the Bering Strait is about a third of that at the shelf break (M2 amplitude of 23 cm). The semidiurnal phase lags are earliest at the shelf break (87°G for M2) and appear to increase toward St. Lawrence Island (336°G for M2 in Shpanberg Strait) and the Bering Strait (202°G for M2). The tidal harmonic constants fluctuated seasonally, possibly in response to the variations in ice cover. The diurnal amplitudes generally increased during winter, while the semidiurnal amplitudes decreased. At the shelf break the K1 amplitude increased 2.5 cm or 7%, but the O1 and semidiurnal M2 amplitudes (0.4 cm or 2% for M2) showed little variation. In Bering Strait the variations in M2 amplitude (up to 3.0 cm) amounted to 37% of the mean amplitude; the decrease may be due to attenuation of the M2 tide from the Arctic Ocean in addition to damping of the M2 tide on the northeastern Bering Sea shelf. Shorter‐term fluctuations were also observed in the tides. The tidal fluctuations may contribute to those observed in the deep sea. Numerical models show a set of amphidromic systems (including a semidiurnal system off Cape Navarin) and rapid phase transitions in the vicinity of some of the stations; these models are in relatively good agreement with the observations.
Generation mechanism of internal waves by tidal flow over a sill
Authors: Hibiya Toshiyuki
Published: February 2008

The generation mechanism of internal waves by relatively strong tidal flow over a sill is clarified analytically. Special attention is directed to the role of the tidal advection effect, which is examined by use of characteristics. An internal wave which propagates upstream is gradually formed over the sill through the interference among infinitesimal amplitude internal waves (elementary waves) emanated from the sill at each instant of time. In the accelerating (decelerating) stage of tidal flow, the effective amplification of an internal wave takes place as the Froude number exceeds (falls below) unity, because during this period the internal wave slowly travels downstream (upstream), crossing over the sill, where elementary waves are efficiently superimposed. When the strength of the tidal advection effect is appropriate, the internal wave formed in the accelerating stage (Ac wave) and that formed in the decelerating stage (Dc wave) overlap, so that the resultant wave height becomes very large. Since the relative position of Ac and Dc waves varies depending on the strength of the tidal advection effect, the resultant internal wave form is strongly affected by it. When the tidal advection effect is strong, the Ac wave is carried too far downstream to interfere with the Dc wave, and hence the resultant wave form consists of two crests and two troughs. When the tidal advection effect is moderate, the optimum interference between Ac and Dc waves occurs, and the resultant wave form consists of one crest and one trough, with its horizontal scale approaching that of the sill. When the tidal advection effect is weak, the internal wave height becomes very small, since elementary waves propagate almost freely in the tidal flow without coming close together, and the resultant wave form approaches a sinusoidal wave of tidal frequency.
Acoustic measurements of internal wave rms displacement and rms horizontal current off Bermuda in late 1983
Authors: Stoughton Roland B. , Flatté Stanley M. , Howe Bruce M.
Published: February 2008

We use acoustic pulse travel times to measure rms internal wave currents and depth‐ and time‐dependent rms internal wave displacements west of Bermuda in August and September 1983. Displacement energy levels at depth ≲ 200 m are close to the standard Garrett‐Munk (GM) level, while displacement energy levels in the depth range 600–900 m are about one‐half GM. These levels are constant in time to ∼30% over the 6 week data period. Current energy levels in the depth range 600–900 m are nearly 5 times higher than would be inferred from a GM model scaled to the observed displacements, probably indicating that near‐inertial motions were much stronger than in a GM spectrum. These measurements are consistent with other in situ observations, if a general picture is formed of WKBJ‐scaling violation of about a factor of 2 for displacements, and a strong non‐GM inertial peak in horizontal current spectra.
On the Alaska Coastal Current in the western Gulf of Alaska
Authors: Schumacher J. D. , Reed R. K.
Published: February 2008

Analyses of wind, adjusted sea level, temperature, salinity, and current data show that the Alaska Coastal Current (ACC) flows generally westward from Shelikof Strait to the Shumagin Islands. The seasonal nature of the ACC in the western Gulf of Alaska is similar to that in the northern gulf, but minimum salinity, maximum current speeds, and changes in baroclinic transport are less extreme to the west. Southwest of Shelikof Strait the ACC apparently is bifurcated by the bathymetry. One branch continues flowing along the Alaska Peninsula, and the other flows south. The southward flowing branch may rejoin the westward flowing one in the sea valley just east of the Shumagin Islands.
A quasi‐synoptic survey of the thermocline circulation and water mass distribution within the Canary Basin
Authors: Käse Rolf H. , Price James F. , Richardson Philip L. , Zenk Walter
Published: February 2008

Shipboard hydrographic measurements and moored current meters are used to infer both the large‐scale and mesoscale water mass distribution and features of the general circulation in the Canary Basin. We found a convoluted current system dominated by the time‐dependent meandering of the eastward flowing Azores Current and the formation of mesoscale eddies. At middepths, several distinctly different water masses are identified: Subpolar Mode and Labrador Sea Water are centered in the northwest, Subantarctic Intermediate Water is centered in the southeast, and the saltier, warmer Mediterranean tongue lies between them. Mesoscale structures of these water masses suggest the presence of middepth meanders and detached eddies which may be caused by fluctuations of the Azores Current.
Isotopic versus micrometeorologic ocean CO2 fluxes: A serious conflict
Authors: Broecker Wallace S. , Ledwell James R. , Takahashi Taro , Weiss Ray , Merlivat Liliane , Memery Laurent , Peng Tsung‐Hung , Jahne Bernd , Munnich Karl Otto
Published: February 2008

Eddy correlation measurements over the ocean give CO2 fluxes an order of magnitude or more larger than expected from mass balance measurements using radiocarbon and radon 222. In particular, Smith and Jones (1985) reported large upward and downward fluxes in a surf zone at supersaturations of 15% and attributed them to the equilibration of bubbles at elevated pressures. They argue that even on the open ocean such bubble injection may create steady state CO2 supersaturations and that inferences of fluxes based on air‐sea pCO2 differences and radon exchange velocities must be made with caution. We defend the global average CO2 exchange rate determined by three independent radioisotopic means: prebomb radiocarbon inventories; global surveys of mixed layer radon deficits; and oceanic uptake of bomb‐produced radiocarbon. We argue that laboratory and lake data do not lead one to expect fluxes as large as reported from the eddy correlation technique; that the radon method of determining exchange velocities is indeed useful for estimating CO2 fluxes; that supersaturations of CO2 due to bubble injection on the open ocean are negligible; that the hypothesis that Smith and Jones advance cannot account for the fluxes that they report; and that the pCO2 values reported by Smith and Jones are likely to be systematically much too high. The CO2 fluxes for the ocean measured to date by the micrometeorological method can be reconciled with neither the observed concentrations of radioisotopes of radon and carbon in the oceans nor the tracer experiments carried out in lakes and in wind/wave tunnels.
On the spacing and draft distributions for pressure ridge keels
Authors: Wadhams Peter , Davy Tom
Published: February 2008

The negative exponential distribution is reconsidered as a description of pressure ridge spacings and drafts. It is found to give an excellent fit for drafts but not for spacings. The spacing distribution is found to be fitted much better by a three‐parameter lognormal distribution, of which the third parameter (the threshold) is dependent on the beam width of the instrument used to collect the ice bottom profile.
Random walks with manholes: Simple models of dispersion in turbulence with coherent vortices
Authors: Bennett Andrew F.
Published: February 2008

A one‐dimensional discrete random walk is used to model particle dispersion in a turbulent flow containing isolated, coherent vortices. Steps of length zero are allowed, representing trapping of particles in orbits around vortices. The length of each step is dependent on the preceding step; that is, a second‐order model is used. If there is a nonzero transition probability for a step of nonzero length following a step of zero length, then the net displacement is asymptotically normally distributed. If a step of zero length is always followed by another such step, then the displacement variance is bounded, and the statistics are not normal.
Biological consequences of a recurrent eddy off Point Conception, California
Authors: Haury Loren R. , Simpson James J. , Peláez José , Koblinsky Chester J. , Wiesenhahn David
Published: February 2008

The biological effects on three different time scales (100‐day mesoscale, annual, and several‐year) of a mesoscale anticyclonic eddy consistently found in shipboard surveys and satellite‐sensed data several hundred kilometers southwest of Point Conception, California, are described. A detailed shipboard study of the eddy in January 1981 found a complex system of fronts in surface chlorophyll at the northern edge of the eddy; microplankton and zooplankton distributions were strongly affected by entrainment processes at the surface and, apparently, at depth. Concurrent satellite coastal zone color scanner ocean color images show agreement with the general surface characteristics of the eddy chlorophyll field but do not reflect features deeper than about 25 m, including the contribution of the deep chlorophyll maximum to the integrated chlorophyll values. Satellite data for the period October 1980 through October 1981 and shipboard data from California Cooperative Oceanic Fisheries Investigations (CalCOFI) for December 1980 to July 1981 show the continued presence of the eddy in the sea surface temperature and color field and in the distributions of surface chlorophyll and zooplankton displacement volume. A review of the CalCOFI survey results from 1949 to the present time demonstrates the recurrent nature of the eddy system on a year‐to‐year basis. The eddy system appears to have a significant effect on the distribution of both oceanic and nearshore organisms. Offshore transport of coastal species occurs in the form of large entrained plumes or filaments.
The tidal spectrum underneath Antarctic ice shelves
Authors: Pedley M. , Paren J. G. , Potter J. R.
Published: February 2008

A year‐long tidal record has been obtained from beneath the George VI Ice Shelf, Antarctica. An unusual feature of the record is a significant response in tidal species 3 to 7. These harmonics are practically absent from records further north on the west coast of the Antarctic Peninsula but are present in all tidal height records from George VI Sound. A strong ter‐diurnal signal also exists in the tidal currents under the ice shelf. Nonlinearity also occurs in the tidal motion of the Ronne and Ekström ice shelves but has not been reported from the Ross Ice Shelf. The tidal dynamics of several Antarctic ice shelves have therefore been modified by a region of strong nonlinear response to tidal forcing. If nonlinear tides in the semidiurnal band are present on the Ross Ice Shelf, they could account for difficulties in modeling the area's weak semidiurnal tides. An anelastic component in the deformation of the ice at the grounding line is tentatively proposed as the mechanism responsible. The positioning of recording pressure sensors in pairs on the seafloor and at the ice shelf base will allow this hypothesis to be tested and also provide a value for the power dissipated by tidally induced flexure at the grounding line.
Oscillating turbulent boundary layer with suspended sediments
Authors: Hagatun Kjell , Eidsvik Karl J.
Published: February 2008

A dynamic boundary layer model with simultaneous interactions between constant, oscillatory, and turbulent flow; suspended sediments; and erosion is developed. The model appears to be verified as well as the existing data permits. In purely oscillatory flow most of the state variables appear to be associated with a turbulent kinetic energy maximum developing near the bottom and phase angle π/2 and propagating upward thereafter. The maximum horizontal sediment flux is approximately proportional to the third power of the maximum turbulent stress. A channel flow with constant pressure gradient may be strongly reduced by the presence of waves. The waves may also increase the suspended sediment concentration significantly.
A model of the seasonal cycle in the tropical Atlantic Ocean
Authors: Philander S. G. H. , Pacanowski R. C.
Published: February 2008

In the western tropical Atlantic, seasonal variations in the surface winds and in the ocean are dominated by an annual harmonic. A simulation with a general circulation model indicates that the response in the western side of the basin is an equilibrium one practically in phase with the local winds. It includes the following: large vertical excursions of the thermocline that have a 180° change in phase across 8°N approximately; a change in the direction of the North Brazilian Coastal Current, which flows continuously along the coast between December and May but which veers offshore near 5°N to feed the North Equatorial Countercurrent during the other months; and a seasonal reversal of the countercurrent. To the east of 30°W, seasonal changes in the model have a prominent semiannual harmonic in phase with the local winds but only partially attributable to forcing at that frequency. The transients excited by the abrupt intensification of the southeast tradewinds in May happen to have a phase essentially the same as that of the semiannual forcing. These transients decay by the end of the calendar year, so that the seasonal cycle that starts with the intensification of the winds in May can be treated as an initial value problem as far as the upper ocean, above the thermocline, is concerned. The winds along the equator determine the response of the surface equatorial layer in the Gulf of Guinea but play a minor role in the seasonal upwelling along the coast near 5°N. That upwelling is strongly influenced by changes in both components of the wind, and in the curl of the wind, over the Gulf of Guinea.
The distribution of bomb tritium in the ocean
Authors: Broecker Wallace S. , Peng Tsung Hung , Ostlund Gote
Published: February 2008

A global picture of the water column inventories of bomb‐produced tritium is constructed from the GEOSECS data set. this picture is compared with that obtained by combining the bomb tritium input function of Weiss and Roether [1980] with the bomb radiocarbon calibrated lateral redistribution model of Broecker et al. [1985]. While differences between the calculated and observed distribution exist, they are surprisingly small. Tritium distributions calculated using the lateral redistribution model provide predictions of the changes to be expected in the next few decades. Such predictions are essential to the design of sound strategies for continued monitoring of the tritium transient.
The response of the upper ocean to a large summertime injection of smoke in the atmosphere
Authors: Mettlach Theodore R. , Haney Robert L. , Garwood Roland W. , Ghan Steven J.
Published: February 2008

A one‐dimensional oceanic planetary boundary layer model is used to investigate the response of the upper ocean to the atmospheric conditions which are predicted to develop following a hypothetical nuclear exchange. The ocean model is driven by the surface heat and momentum fluxes predicted by an atmospheric general circulation model following a summertime injection of 1.5 × 1014g of smoke from postwar fires over Europe, Asia, and North America. Although the specific response of the upper ocean is highly dependent on the geographic location, the mid‐latitude summertime mixed layer typically cools 3° to 5°C and deepens 25 m during the first 30 days following the smoke injection. Moreover, a large fraction of this response is found to take place during a short 2‐ to 3‐day period of very intense winds and falling air temperatures, which occurs during the first week or two after the smoke injection.
Ventilation rate of the deep Arctic Ocean from carbon 14 data
Authors: Östlund H. Göte , Possnert Göran , Swift James H.
Published: February 2008

Application of mass balances of 18O, tritium and salt, plus 14C data show that the deep Eurasian Basin exchanges water with the subarctic Atlantic Ocean on a time scale of 10 to 100 years, while the deep Canada Basin has an exchange time scale of about 700 years. Only small fractions, less than 10 to 15% of the deep waters, originate from the shelves. The deep Canada Basin cannot consist of fossil water from glacial time or from the latest cool climate spell, just 100 to 300 years ago.
Accuracy of bulk‐method‐determined flux, stability, and sea surface roughness
Authors: Blanc Theodore V.
Published: February 2008

This paper discusses the various uses of bulk‐method‐determined fluxes and the inherent difficulties of making flux measurements over the ocean. The accuracy of eddy correlation, profile, dissipation, and bulk flux methods is compared. We conclude that there are four principal sources of uncertainty in bulk flux determinations made using ship data: the accuracy of the flux measurements used to develop the bulk method, the variations resulting from the use of different bulk coefficient schemes, the accuracy of the meteorological sensors, and the distortion of the measurements produced by the ship. This paper also describes previously published analyses of each of these uncertainty sources and compares the relative importance of those sources. Finally, the results are combined to estimate the overall accuracy of the method. Our analysis determined that the average accuracy of the bulk method ranges from 35% to 105% for stress magnitudes of 0.025–1.0 N/m2, 35–220% for sensible heat flux magnitudes of 5–150 W/m2, 40–215% for latent heat flux magnitudes of 10–300 W/m2, 85% to > 1000% for Monin‐Obukhov stability magnitudes at 10 m of 0.001–10, and 160% to > 1 × 104% for roughness length magnitudes of 10−5–10−2 m. The results of the analysis are presented graphically and in tabular and polynomial forms to facilitate their use by those wishing to test the sensitivity of their work to the typical average uncertainty of bulk method flux, stability, and sea surface roughness determinations.
High‐frequency internal wave observations in the marginal ice zone
Authors: Sandven Stein , Johannessen Ola M.
Published: February 2008

Three thermistor chains extending from 15 to 65 m were deployed from ice floes in the Marginal Ice Zone north of Svalbard in a triangle with sides of 500–800 m for a period of 7 days. Vertical displacement spectra indicate that the internal wave energy level is lower than the Garrett and Munk spectrum by a factor of 2–3 but higher than other observations in the Arctic. A group of internal waves (a wave train), with frequency of 2–3 cph was observed to propagate at 0.05 m/s through the triangle in a west‐southwesterly direction during a 4‐ to 6‐hour period. A case study of this wave train, where the horizontal phase differences between the three thermistor chains were analyzed, showed wavelengths of 100–200 m and phase velocities of 0.10–0.15 m/s. Observation of the density field and the velocity field indicated that stratification dominated over vertical shear. Consequently, the dispersion relation was calculated by solving numerically the vertical mode equation for internal waves in a shearless ocean. The estimated wavelengths and phase velocities agree with the dispersion relation for first‐mode internal waves. The generating mechanisms may be tidal oscillations associated with a seamount located east of the triangle, or ice keels moving in relation to the water creating lee waves in the pycnocline.
A time‐dependent model for turbulent transfer in a stratified oceanic boundary layer
Authors: McPhee Miles G.
Published: February 2008

A first‐order model for vertical flux of momentum and scalars in a rotational boundary layer is applied to the oceanic boundary layer beneath sea ice. Model eddy viscosity is proportional to the product of the local friction velocity u* and a master length scale for vertical exchange, which is a function of the rotational length scale u*/ƒ and the local Obukhov length L. The ratio of eddy diffusivity to eddy viscosity is 1 when turbulence is energetic but falls to lower values when turbulence levels are low and stratification high, according to an empirical relation. There are three empirical constants in the theory: ξN, the ratio of the master length scale to the rotational length scale; Rc, the critical flux Richardson number; and a shape factor describing the falloff of the eddy diffusivity ratio at high gradient Richardson numbers. For an idealized simulation of melting and freezing conditions representative of the marginal ice zone, the model agrees closely with a similar implementation of the Mellor‐Yamada level 2.5 model. The model is demonstrated by performing a simulation of surface drift and mixed‐layer properties observed during the 1984 Marginal Ice Zone Experiment field study in the Greenland Sea.
High‐frequency ice floe collisions in the Greenland Sea During the 1984 Marginal Ice Zone Experiment
Authors: Martin Seelye , Becker Paul
Published: February 2008

During the 1984 Marginal Ice Zone Greenland Sea Experiment, we carried out a field study on the relation between ice floe collisions and ocean swell. The experiment consisted of the deployment on separate ice floes of three buoys, each of which contained a compass and a set of triaxial accelerometers. The floes had characteristic diameters of 100 m and thicknesses of 1–5 m. From two major deployments of these buoys, we gathered 16 days of data. From the vertical accelerometer data, we calculated the variation in the long‐period ocean swell with time; from the horizontal accelerometers, we determined the individual and mean collision properties. Examination of the individual collisions showed that two types of collisions occurred: a short‐period spike that recurred with the period of the ocean swell, and a longer period acceleration event that was uncorrelated with the swell. We observed several hundred of the first type of collision in our data set but only eight of the second type. The number of periodic collisions in a 9‐min sample and the energy of these collisions were generally correlated with the ocean swell energy. The ocean swell measured at the floes had root‐mean‐square (rms) amplitudes of 1–30 mm and periods between 10 and 18 s. After removal of the ocean swell signal, the collisions had characteristic horizontal displacements of 5–35 mm, with rms velocities of the order of 1 mm s−1.
Infragravity waves over a natural barred profile
Authors: Sallenger Asbury H. , Holman Robert A.
Published: February 2008

Measurements of cross‐shore flow were made across the surf zone during a storm as a nearshore bar became better developed and migrated offshore. Measured infragravity band spectra were compared to synthetic spectra calculated numerically over the natural barred profile assuming a white run‐up spectrum of leaky mode or high‐mode edge waves. As in earlier studies, the spectra compared closely; however, for some frequencies the energy of the measured spectrum exceeded the energy of the synthetic spectrum, suggesting that the run‐up spectrum was not white but had dominating frequencies. Utilizing cross‐shore flow data and synthetic spectra from a number of cross‐shore locations, an equivalent run‐up spectrum was calculated for each day. On the first day of the storm, the equivalent run‐up spectrum indicated a dominant wave that had a node in velocity reasonably close to the bar crest. Later during the storm, when the bar had migrated farther offshore, there was no evidence for a dominant motion having a velocity node at the bar crest. The structure of the equivalent run‐up spectrum compared well with spectra of direct measurements of run‐up obtained several hundred meters away. We have no clear evidence in support of the theory that infragravity waves might form or force the offshore migration of a bar. To confirm this finding, longer records obtained synoptically over a developing bar are required. The dominant wave observed early in the storm was consistent with Symond and Bowen's (1984) theoretical prediction of resonant amplification of discrete frequencies over a barred profile.
Variability of an under‐ice river plume in Hudson Bay
Authors: Ingram R. Grant , Larouche Pierre
Published: February 2008

Observations of the Great Whale River plume in the coastal waters of Hudson Bay, Canada, during late winter and early spring during four different years showed its area to vary as a power of the discharge. The under‐ice plume area was much larger than plume area in open water for comparable discharges. Differences in plume geometry were related to elapsed time since ice formation and low‐frequency variability of the coastal circulation. The strength and orientation of the coastal motion was weakly correlated with the cross‐Hudson Bay atmospheric pressure gradient. The passage of low‐pressure systems over Hudson Bay is thought to generate a progressive edge wave in the absence of direct wind forcing. The amplitude of the low‐frequency variations in coastal circulation decreased with the increasing spatial extent of the landfast ice in the study area.
Wind and topographic effects on the Labrador Current at Carson Canyon
Authors: Kinsella E. Douglas , Hay Alex E. , Denner Warren W.
Published: February 2008

We present results from an experimental investigation of the interaction between a shelf break jet and a submarine canyon and of the response of this system to a single upwelling favorable wind event. The field site was Carson Canyon, located at the edge of the Grand Bank of Newfoundland. The shelf break jet is the Labrador Current. The time‐averaged current measurements indicate that the interaction between the Labrador Current and the canyon topography is nonlinear and that the mean current crosses isobaths to flow into the canyon on the upstream side but is steered off shelf on the downstream side. The mean flow vorticity balance in the near field and far field is examined, using a two‐layer model with the lower layer at rest. In the far field we obtain an interesting result which suggests that the cross‐stream shear in combination with bottom friction can drive a significant on‐shelf flow. This flow is equivalent to a volume transport of about 60 m3s−1per 100 m of along‐shelf distance, which is comparable to typical wind‐driven Ekman transports on and off continental shelves and which appears to have important implications for the on‐off‐shelf transport of icebergs in the Grand Banks region. In the near field the Rossby number is of order unity and bottom friction is less important. Many of the observed flow properties can be explained qualitatively in terms of an upstream inertial boundary layer and potential vorticity conservation. The time‐dependent response to upwelling favorable winds was registered by current meters in the canyon and at the shelf break at the canyon perimeter. These observations indicate an amplified upwelling response at the shelf break and vertical ascent rates within the canyon of about 0.7 cm s−1.
Genesis of a Gulf of Mexico ring as determined from kinematic analyses
Authors: Lewis James K. , Kirwan A. D.
Published: February 2008

The kinematics of the Loop Current are studied using trajectories of drifters in the Gulf of Mexico during mid‐June through September 1985. One of the drifters was in the Loop Current proper, while other drifters were in two recently shed Loop Current rings. The drifter in the Loop Current showed strong anticyclonic motion during the study period. This Loop Current anticyclone first began off the northwest coast of Cuba. It rapidly moved northward into the Gulf of Mexico as a ring pinched off from the Loop Current. Analysis of the Loop Current drifter motion showed that the anticyclone became an integral part of the Loop Current, taking on many of the characteristics of the most recently shed ring. The results of the analysis suggest a process by which Loop Current rings can be generated. Apparently, this mechanism can cause the Loop Current to become reconfigured in 2–3 months for beginning the process of ring separation.
Characteristics of extreme rainfall events in northwestern Peru during the 1982–1983 El Niño period
Authors: Goldberg R. A. , Tisnado M. G. , Scofield R. A.
Published: February 2008

Using rainfall data from 66 stations within the Chira‐Piura Project of northwestern Peru, we have prepared an atlas of histograms and contour maps describing the daily rainfall characteristics of the region during the El Niño period from November 1982 to June 1983. We have compared these data with those for the same 8‐month intervals during the 2 years preceding and following the designated period. Uniquely during the El Niño period, these data often exhibit localized storms of high rainfall intensity (>100 mm/d) which may then disperse over wider areas of the region during the following 2–3 days. The region nearby and to the east of Chulucanas (5.10°S, 80.17°W) appears to be a focal point for the initiation of such events, particularly during the 1983 months of the period. Case studies for a few of the most severe events have been performed and compared with an analysis using GOES satellite cloud imagery in conjunction with upper air and surface weather maps, to arrive at a possible scenario for the cause and evolution of such events. Statistically, a high percentage of the storms are found to be multicellular with scale sizes approaching 250 km, with minimum cloud temperatures colder than −60°C, and of durations exceeding 6 hours. Such storm systems are consistent with the extreme and disastrous rainfall events observed from ground stations. The satellite analysis has also permitted us to identify significant storms beyond the range of the ground‐based stations during this same time period, demonstrating the complementary value of satellite coverage for developing a more comprehensive view of the processes in effect.
An investigation of the El Niño‐Southern Oscillation cycle With statistical models: 1. Predictor field characteristics
Authors: Graham Nicholas E. , Michaelsen Joel , Barnett Tim P.
Published: February 2008

We have developed two sets of linear models for predicting equatorial Pacific sea surface temperatures (SSTs) from the Indo‐Pacific trade wind field and the near‐global sea level pressure (SLP) field. The models were constructed using a combination of extended empirical orthogonal functions (EEOFs) and canonical correlation analysis (CCA), a new approach in geophysical modeling. Our results are of interest both as they show the dominant modes of evolution in the SLP and wind fields through the El Niño‐Southern Oscillation cycle and with respect to the problem of predicting equatorial SSTs. This paper deals with the first issue above and describes some statistical composites that typify the development of features in the predictor fields over periods of years. The results of the EEOF analyses clearly show slowly propagating anomalies in both the near‐global SLP and trade wind fields. The CCA analysis, which highlights the co‐evolution of the two fields, suggests a strong coupling between the two and depicts the anomalous features as migrating centers of divergence and convergence that first appear over the eastern Indian Ocean. These features propagate slowly eastward, amplify as they expand into the western Pacific, decline as they cross the central ocean, then reamplify over the eastern Pacific. As reamplification takes place, new opposing anomalies appear in the Indo‐Pacific. Descriptions of the predictor data sets and details of the statistical techniques used may also be found in this paper. The SST data, model validation techniques, and forecast model results are presented in a companion paper (Graham et al., this issue).
Oceanographic variability off Ecuador associated with an El Niño event in 1982–1983
Authors: Cucalon E.
Published: February 2008

The development of the 1982–1983 El Niño event is described by reference to the oceanographic conditions prevailing off Ecuador during the period 1982–1984. The first signs of the anomaly's onset off the Ecuadorian coast were observed in August 1982: the 16°C isotherm was found some 50 m deeper than normal along 82°30′W; this observation preceded by approximately 2 months the rapid rise in sea level, the appearance of warm sea surface temperature (SST) anomalies, and heavy rainfalls. By February 1983, the whole area off Ecuador was covered by very warm (29°–30°C) and low salinity (less than 33.0 parts per thousand) surface water. Two mechanisms seemed to be involved in the formation of the low‐salinity water: advection of northern water and dilution by local rainfall. Although the ocean surface was 4°C warmer than normal, the most notable changes took place throughout the water column: a strong depression of the thermocline and all the isotherms down to 15°C, the largest anomalies being observed over the 100‐m water column, up to 9°C at 50‐m depth. During the subsequent months SSTs continued to increase; thus the highest SST anomalies (6.3°C) were observed in May and June. Recovery from the 1982–1983 anomaly started in July 1983 with a general uprising of the isotherms and a fall in sea level. By October, the warm SST anomalies had dropped to 1.5°C. In November 1983, the presence of the equatorial front also attested to the return to normal of the oceanographic conditions in the region.
Reproduction and population levels of Peruvian Guano Birds, 1980 to 1986
Authors: Tovar H. , Guillén V. , Cabrera D.
Published: February 2008

The three species of guano birds, guanay cormorant (Phalacrocorax bougainvillii), Peruvian booby (Sula variegate), and Peruvian pelican (Pelecanus occidentalis thagus), depend mainly on the Peruvian anchovy (Engraulis ringens) for sustenance. A naturally occurring limitation on the population size of these birds is the oceanographic phenomenon known as “El Niño”. The industrialization of the anchovy fishery during the 1960s and 1970s has also affected seabird populations: The annual extraction of huge volumes offish has decreased the availability of food for the guano birds, causing large population fluctuations and considerable changes in the relative abundance of the birds. Because of its great intensity and duration, the 1982–1983 El Niño caused high avian mortality, depressing populations to levels from which they have not yet recovered.