bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of the Mediterranean mean sea level to atmospheric pressure forcing
Authors: Le Traon Pierre‐Yves , Gauzelin Philippe
Published: February 2004

The response of the Mediterranean mean sea level to atmospheric pressure forcing is analyzed using 3 years of TOPEX/POSEIDON data. Coherence analysis between mean sea level and atmospheric pressure shows a significant departure from a standard inverse barometer effect at frequencies higher than 30 days−1. At high frequencies the phase difference between sea level and pressure is about 100°, while it should be 180° for a perfect inverse barometer response. This result is in agreement with previous findings and confirms the role of the Straits of Gibraltar and Sicily in limiting the water exchange (and thus the response to atmospheric pressure forcing) at high frequencies. The response of the Mediterranean mean sea level is then investigated using the Candela [1991] analytical model which takes account of friction in the Straits of Gibraltar and Sicily. The model explains a large part of the variance in TOPEX/POSEIDON mean sea level variations (50% for the western basin and 38% for the eastern basin). Compared to an inverse barometer correction, it gives a smoother response with a phase delay at high frequencies. It also explains more variance in TOPEX/POSEIDON mean sea level variations (5 cm2 and 7 cm2 for the western and eastern basins, respectively). This demonstrates that this simple model provides an improved correction of atmospheric pressure effects in TOPEX/POSEIDON data. As the two corrections have an rms difference of 2–3 cm with maximum differences of up to 10 cm, the impact on the mapping of oceanic circulation is not negligible. This is exemplified through the comparison of sea level anomaly derived from the two corrections.
Bulk parameterization of momentum, heat, and moisture fluxes over a coastal upwelling area
Authors: Enriquez Amelito G. , Friehe Carl A.
Published: February 2004

Aircraft measurements of turbulent fluxes of momentum, sensible heat, and moisture were used to calculate bulk aerodynamic coefficients over the northern California coastal shelf during wintertime (Shelf MIxed Layer Experiment, SMILE) and summertime (Coastal Ocean Dynamics Experiment, CODE). Low‐level (30 m) data from 15 SMILE flights and 15 CODE flights with varying stability conditions, wind directions, and intensities were reduced to the standard reference height of 10 m using diabatic flux‐profile relations following Monin‐Obukhov similarity theory. The fluxes were parameterized by bulk aerodynamic formulas after reduction to neutral stability. Results for summer and winter were in reasonably good agreement if the bulk coefficients are averaged over intervals of 1 m s−1 and linear regression with speed is performed using the averaged values. The neutral drag coefficient showed a statistically significant linear dependence on wind speed at 10‐m height, while the neutral Stanton and Dalton numbers (the heat and moisture transfer coefficients) were independent of wind speed and were not significantly different from each other. The response of the ocean to the atmospheric forcing and the feedback of the resulting ocean circulation on the wind forcing were studied using a vertically resolved numerical model of coastal upwelling. The model was run using buoy observations of wind speed, air temperature, atmospheric pressure, and relative humidity from SMILE and CODE. The resulting coastal upwelling produced a negative feedback through decreased sea surface temperature at the coast and increased atmospheric stability which decreased the effective drag coefficient (and hence the wind stress) by at most 30% near the coast, with an average decrease of about 12% within 100 km from the coast. The effect of this decrease in wind stress, however, produced an insignificant change in the sea surface temperature field, which indicates that parameterization of coastal drag coefficients for modeling coastal upwelling can be done without taking into account surface temperature feedback.
Surface roughness of Baltic sea ice
Authors: Manninen A. T.
Published: February 2004

Small‐, medium‐, and large‐scale measurements of sea ice surface roughness were carried out in the Baltic Sea over a 3‐year period. A clear relationship was found between the rms height and correlation length of Baltic sea ice. In most cases the surface correlation function was close to exponential. The logarithm of rms height showed a linear dependence on that of measured distance. Similarly, the correlation length was in many cases linearly dependent on the measured distance. This dependence on length suggests that ice surface roughness could be characterized as a fractal.
Basin‐wide zonal wind stress and ocean thermal variations in the equatorial Pacific Ocean
Authors: Yang Y. J. , Tang T. Y. , Weisberg Robert H.
Published: February 2004

Wind data, obtained from the model results of the European Centre for Medium Range Weather Forecasts (ECMWF), for the equatorial Pacific Ocean from 1985 to 1992, were employed to study the basin‐wide distributions for various constituents of zonal wind stress. Forcing the ocean by the individual constituent of zonal wind stress, the upper ocean thermal variation was investigated using a linear analytical ocean model. The interannual variation of zonal wind stress is largest in amplitude in the west‐central part of the basin and is dominated by an eastwardly propagating wave. The upper layer thickness perturbation h shows an evolving eastward propagation over the region where the interannual wind stress variation occurs, while to the east and west the region changes nearly in phase. The evolution of h agrees well with the evolution of upper ocean heat content anomaly, estimated from the Tropical Atmosphere‐Ocean (TAO) moored array. The annual cycle of zonal wind stress can be described properly by a combination of annual and semiannual variations. The annual variation of zonal wind stress was found to propagate westward with relative maxima out of phase to the west and east of the west‐central Pacific. The semiannual variation is stationary and is largest in amplitude in the western basin. Forced by the two components of the annual cycle of zonal wind stress, the evolution of h shows a westward propagation. This does not correlate well with the pattern of the evolution of the annual cycle of upper ocean heat content which emanates from the east‐central Pacific and shows both eastward and westward propagation. The seemingly anomalous eastward propagation is mainly related to the abrupt change during the relaxation/intensification period of the easterly wind stress. The abrupt change of the annual zonal wind stress variation in both time and space is, then, critical for the evolution of the pattern of the annual ocean response.
The importance of interocean exchange south of Africa in a numerical model
Authors: Thompson Simon R. , Stevens David P. , Döös Kristofer
Published: February 2004

A fine resolution numerical model of the Southern Ocean (the Fine Resolution Antarctic Model (FRAM)) has been used to investigate the way in which heat is supplied to the South Atlantic. The heat budget in the model is compared with other estimates and is found to be broadly realistic. The temperature structure in the Atlantic, and therefore the meridional heat transport, depend heavily on the input of heat from the Indian Ocean via the Agulhas Retroflection region. FRAM is compared with three models which do not exhibit a significant input of heat from the Indian Ocean. These models also have a lower equatorward heat transport in the South Atlantic. Horizontal resolution affects the amount of Agulhas transfer with coarser resolution leading to lower heat transport in the Atlantic, a result which has implications for ocean models used in climate simulations.
Mean hydrographic fields and their interannual variability over the Texas‐Louisiana continental shelf in spring, summer, and fall
Authors: Li Y. , Nowlin W. D. , Reid R. O.
Published: February 2004

New hydrographic data from the Texas‐Louisiana continental shelf were combined with data from older cruises covering significant portions of this shelf to produce spatial distributions of surface and bottom temperature and salinity as well as of surface geopotential anomaly relative to 70 dbar. These were used to calculate mean fields with their standard deviations for spring (May), summer (July–August), and fall (November). For each season, histograms were prepared of differences between properties in the individual fields and our seasonal mean values at each grid point in the individual fields. These histograms have highly tuned Gaussian distributions centered on zero differences, proving that a distribution selected randomly will likely be quite similar to the mean for the season in which the sample was made. The individual fields of salinity for summer and geopotential anomaly for spring are included for comparison with the mean fields. The mean fields, produced by adding a large data set to that used by Cochrane and Kelly [1986], substantiate the bimodal annual patterns of circulation and property distributions over the inner shelf region described by them. Essentially, there is downcoast (directed from the Mississippi toward Brownsville) nearshore flow except during the summer months. That flow is driven by downcoast along‐shelf wind and enhanced by Mississippi‐Atchafalaya River discharge. In July and August the average wind has an upcoast component and the nearshore flow is reversed. Patterns and values of the standard deviations are used to infer causes and magnitudes of interannual variability, respectively. Three examples of anomalous property distributions are presented to illustrate the effects of the principal external forcing mechanisms affecting interannual variability on the Texas‐Louisiana shelf. These mechanisms are wind stress, Mississippi‐Atchafalaya River discharge, and mesoscale eddies in the offshore circulation near the shelf‐slope break. For each cruise examined, residuals of geopotential anomaly and surface salinity relative to the seasonal mean are examined in relation to departures of river discharge from the long‐term (64 year) average and an index of along‐shelf wind component appropriate to the times of the cruises. The residuals of geopotential anomaly were found to be significantly negatively correlated with those of surface salinity, with an intercept of approximately zero indicating that salinity plays the dominant role relative to temperature in year‐to‐year variability of the geopotential anomaly. Positive river discharge residuals were correlated with negative surface salinity residuals; enhanced downcoast wind resulted in negative surface salinity residuals; and enhanced upcoast wind resulted in positive surface salinity residuals. Most correlations were significant (different from zero) at the 95% confidence level.
Frequency‐wavenumber spectrum of wind‐generated gravity‐capillary waves
Authors: Hara Tetsu , Bock Erik J. , Donelan Mark
Published: February 2004

Spatial‐temporal information on wind‐generated gravity‐capillary waves is obtained using a scanning laser slope gauge in a wind wave flume. The results show that a significant portion of short wind wave energy may be contained in wave modes that propagate with the dominant waves rather than at their phase speeds predicted by the dispersion relation. Double‐peaked directional spreading of the spectrum is observed in a certain range of wavenumber and wind stress. A close examination of such results suggests that nonlinear interactions may take place between short waves and higher harmonics of dominant waves or among short waves and enhance the growth of short waves in oblique directions.
Tropical Atlantic sea surface temperature variability and its relation to El Niño‐Southern Oscillation
Authors: Enfield David B. , Mayer Dennis A.
Published: February 2004

Past analyses of tropical Atlantic sea surface temperature variability have suggested a dipole behavior between the northern and southern tropics, across the Intertropical Convergence Zone (ITCZ). By analyzing an improved 43‐year (1950–1992) record of SST [Smith et al, 1996] and other data derived from the Comprehensive Ocean‐Atmosphere Data Set (COADS), it is shown that the regions north and south of the ITCZ are statistically independent of each other at the seasonal to interannual timescales dominating the data, confirming the conclusions of Houghton and Tourre [1992]. Some dipole behavior does develop weakly during the boreal spring season, when there is a tendency for SST anomaly west of Angola to be opposite of that in the tropical North Atlantic. It is further shown that tropical Atlantic SST variability is correlated with Pacific El Niño‐Southern Oscillation (ENSO) variability in several regions. The major region affected is the North Atlantic area of NE trades west of 40°W along 10°N–20°N and extending into the Caribbean. There, about 50–80% of the anomalous SST variability is associated with the Pacific ENSO, with Atlantic warmings occurring 4–5 months after the mature phases of Pacific warm events. An analysis of local surface flux fields derived from COADS data shows that the ENSO‐related Atlantic warmings occur as a result of reductions in the surface NE trade wind speeds, which in turn reduce latent and sensible heat losses over the region in question, as well as cooling due to entrainment. This ENSO connection is best developed during the boreal spring following the most frequent season of maximum ENSO anomalies in the Pacific. A region of secondary covariability with ENSO occurs along the northern edge of the mean ITCZ position and appears to be associated with northward migrations of the ITCZ when the North Atlantic warmings occur. Although easterly winds are intensified in the western equatorial Atlantic in response to Pacific warm events, they do not produce strong local changes in SST. Contrary to expectations from studies based on equatorial dynamics, these teleconnected wind anomalies do not give rise to significant correlations of SST in the Gulf of Guinea with the Pacific ENSO. As the teleconnection sequence matures, strong SE trades at low southern latitudes follow the development of the North Atlantic SST anomaly and precede by several months the appearance of weak negative SST anomalies off Angola and stronger positive anomalies extending eastward from southern Brazil along 15°–30°S.
Long baroclinic Rossby waves detected by TOPEX/POSEIDON
Authors: Polito Paulo S. , Cornillon Peter
Published: February 2004

Residual sea surface height anomaly fields are obtained over the North Atlantic Basin from TOPEX/POSEIDON altimeter data. Evidence of westward propagating anomalies characterized as first‐mode baroclinic Rossby waves is presented. The phase speeds are obtained from the analysis of the autocorrelation matrices of the residual surface height anomaly in three dimensions, on a 5°×5° grid. Periods are calculated by least squares fitting a sinusoidal function to the time series at each grid point. Zonal and meridional wavelengths are obtained from the phase speed and period and are least squares fit to the data as a consistency check. Zonally averaged westward phase speeds vary between 1 and 27 km/d, between 50° and 5°N, increasing southward. Phase speeds are directed to the southwest north of approximately 25°N and to the northwest south of this latitude. The sea surface height signal is divided into two spectral bands, the first with periods between 280 and 450 days and the second with periods between 120 and 280 days. For the first band the average of the periods taken over the whole basin is 370 days. In the second band a signal of period between 6 and 7 months is evident also throughout the basin. The zonally averaged zonal wavelengths associated with the first band are in the range of 400–4600 km between 50° and 5°N and for the second band are in the range 270–2500 km between 45° and 5°N. Longer wavelengths are found close to the southern boundaries. Shorter wavelengths are found in the northern portion of the basin. Comparison with results from numerical models suggests that the baroclinic waves observed at midlatitudes are generated at the eastern boundary by fluctuations of the wind stress curl. Waves observed south of 20°N support the hypothesis of direct wind forcing.
Major features and forcing of high‐latitude northern hemisphere atmospheric circulation using a 110,000‐year‐long glaciochemical series
Authors: Mayewski Paul A. , Meeker Loren D. , Twickler Mark S. , Whitlow Sallie , Yang Qinzhao , Lyons W. Berry , Prentice Michael
Published: February 2004

The Greenland Ice Sheet Project 2 glaciochemical series (sodium, potassium, ammonium, calcium, magnesium, sulfate, nitrate, and chloride) provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid‐low latitudes of the northern hemisphere. Interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants, volcanic and biomass burning events, storminess over marine surfaces, continental aridity and biogenic source strength plus information related to the controls on both high‐ and low‐frequency climate events of the last 110,000 years. Climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long‐term behavior of atmospheric circulation patterns through changes in ice volume (sea level), events such as the Heinrich events (massive discharges of icebergs first identified in the marine record) that are found to operate on a 6100‐year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics, and rapid climate change events (massive reorganizations of atmospheric circulation) that are demonstrated to operate on 1450‐year cycles. Changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events. Explanation for the exact timing and global synchroneity of these events is, however, more complicated. Preliminary evidence points to possible solar variability‐climate associations for these events and perhaps others that are embedded in our ice‐core‐derived atmospheric circulation records.
Impact of eastern Arctic shelf waters on the Nansen Basin intermediate layers
Authors: Schauer Ursula , Muench Robin D. , Rudels Bert , Timokhov Leonid
Published: February 2004

The Eurasian shelves supply water to the Nansen Basin intermediate layers in two ways: as buoyancy‐driven plumes of dense winter water and as permanent inflow of the Barents Sea branch of Atlantic Water. While the plumes are local and seasonal phenomena, the Barents Sea flow is part of the large‐scale circulation. Both interact with Atlantic Water, which enters the Arctic Ocean through Fram Strait and moves as a subsurface boundary current eastward along the continental slope. During the Polarstern cruise ARK IX/4 in summer 1993, the Fram Strait branch was observed as a narrow core within tens of kilometers of the Barents Sea shelf edge. Here, several patches of cold, low‐salinity water spread across the slope down to about 500 m depth. Their origin is assumed to be the northern Barents Sea. They mix with the warm, saline Fram Strait branch water (FSBW), so that the core properties of the latter become modified downstream. In the eastern Nansen Basin the Fram Strait branch is displaced toward the inner basin by inflow of the Barents Sea Branch of Atlantic Water (BSBW). This inflow appears as a broad (200 km) wedge extending from 200 to 1300 m depth. BSBW is colder and less saline than water of the Fram Strait branch, and it is less dense and less stratified than the ambient water. Both branches appear to undergo vigorous mixing while spreading eastward, so that any eastward continuation of the boundary flow transports about 50% BSBW and 50% FSBW above 600 m and about 80% BSBW and 20% FSBW below that level toward the Canadian Basin. According to available observations, the Barents and Kara Seas are the only source areas for shelf waters ventilating the Nansen Basin below the halocline, and these waters constitute a freshwater input rather than a salt input. Winter shelf water from the Laptev Sea cannot contribute to layers deeper than the upper halocline.
The importance of aspiration and channel curvature in producing strong vertical mixing over a sill
Authors: Seim Harvey E. , Gregg Michael C.
Published: February 2004

On the basis of observations of the time‐dependent, tidally forced flow over a long sill we find that aspiration and channel curvature set the flow structure and condition the flow to allow intense vertical mixing. Aspiration reduces the potential energy of the water column by thinning it while maintaining its density contrast. Channel curvature induces a cross‐channel circulation that can rapidly overturn a stratified flow. Eighteen along‐channel sections of density, velocity, and dissipation rate of turbulent kinetic energy ∈ were collected in and around the Tacoma Narrows of Puget Sound, a site suspected of driving a strong vertical circulation in adjoining Main Basin. Rapid inflow to the Narrows on flood from one channel of a triple junction reduces dynamic pressure, allowing dense water from below sill depth to be uplifted, or aspirated, into the Narrows. We estimate water from below 150 m, 3 times the sill depth, is drawn into the Narrows on a 3‐m flood tide. Once in the Narrows the flow remains stratified until it passes a 50° bend where a strong secondary circulation overturns the 50‐m‐deep water column and generates intense turbulent mixing. Cross‐channel velocities of up to 0.4 m s−1 are observed, and maximum values of ∈ exceed 10−3 W kg−1. Upon leaving the sill, stratification is reestablished, and turbulence decays. A similar set of sequences occurs on ebb, except that the outflow bypasses the flood inflow channel and instead discharges into Colvos Passage, the third branch of the triple junction. Colvos Passage ultimately discharges the ebb effluent back into Main Basin, enhancing the impact of mixing at the Narrows by discharging the mixed product far from the source. Scaling of the cross‐channel momentum equation suggests that, below a threshold value of along‐channel velocity, stratification should suppress secondary circulation for a given vertical shear, radius of curvature and channel width. Above the threshold velocity the magnitude of the cross‐channel velocity is roughly consistent with predictions for unstratified flow. We estimate the maximum effective eddy diffusivity that aspiration and mixing in the Narrows can produce in Main Basin to be 10−3 m2 s−1.
Estimates of the transport through the East River, New York
Authors: Blumberg Alan F. , Pritchard Donald W.
Published: February 2004

The hydrodynamic characteristics of the East River, New York, which connects Long Island Sound to New York Harbor, have been investigated via a high‐resolution, topographically conformal and orthogonal curvilinear grid together with high‐quality acoustic Doppler current profiler measurements. The objective is to determine the volume flux of water through this important water body. The model was calibrated and validated through comparisons with measured salinities, water levels, current velocities, and data‐based estimates of volume flux. Detailed statistical analyses demonstrated that both the tidal and meteorological bands spanning inverse frequencies between 3 hours and 5 days were well simulated by the model. The climatological band (inverse frequencies greater than 5 days) did not exhibit uniformly good agreement because of the paucity of salinity and temperature measurements available for use as model forcing functions. Results from an 18‐month (1988 to 1989) simulation indicate that the net long‐term flux of water is directed out of Long Island Sound and toward New York Harbor. The total rate was found to be about 310 m3 s−1. At the eastern end of the East River near its confluence with Long Island Sound, the net flow was distinctly two‐layered with flows of about 260 m3 s−1 directed toward the sound in the surface layer and flows of approximately 570 m3 s−1 in the bottom layer directed toward New York Harbor. There appeared to be a 100 m3 s−1 monthly variation about the mean transport at the eastern end. However, on shorter timescales the transport reversed direction for days at a time.
Temporal and spatial scales of the Yellow Sea thermal variability
Authors: Chu Peter C. , Wells Susan K. , Haeger Steven D. , Szczechowski Carl , Carron Michael
Published: February 2004

This paper presents an analysis on the space/time statistical thermal structure in the Yellow Sea from the Navy's Master Observation Oceanography Data Set during 1929–1991. This analysis is for the establishment of an Optimum Thermal Interpolation System of the Yellow Sea (a shallow sea), for the assimilation of observational data into coastal σ coordinate ocean prediction models (e.g., the Princeton Ocean Model), and for the design of an optimum observational network. After quality control the data set consists of 35,658 profiles. Sea surface temperatures at 50% and 80% water depths are presented here as representing the thermal structure of surface, middepth, and near‐bottom layers. In the Yellow Sea shelf the temporal and spatial signals fluctuate according to the Asian monsoon. Variation of surface forcing from winter to summer monsoon season causes the change of the thermal structure, including the decorrelation scales. Our computation shows that the seasonal variation of the surface horizontal decorrelation scale is around 90 km from 158 km in winter to 251 km in summer and the seasonal variation of the surface temporal decorrelation scale is around 2.4 days from 14.7 days in winter to 12.3 days in summer. The temporal decorrelation scale increases with depth in both summer (evident) and winter (slight). The near‐bottom water (σ=0.8) has the longest temporal scale in summer, which could be directly related to the existence of the Yellow Sea Cold Water throughout the summer in the middle of the Yellow Sea. The temporal and spatial decorrelation scales obtained in this study are useful for running optimum interpolation models and for designing an optimum observational network. The minimum sampling density required to detect thermal variability in the Yellow Sea shelf would be 50–80 km and 4–6 day intervals per temperature measurement with the knowledge that the subsurface features will also be adequately sampled.
Anticyclonic eddies trapped on the continental shelf by topographic irregularities
Authors: Yankovsky Alexander E. , Chapman David C.
Published: February 2004

Nonlinear effects produced during the scattering of a barotropic shelf wave (BSW) by a spatially varying mean current are studied using a primitive equation numerical model. Both the BSW phase and the mean current propagate in the same (positive) direction along shelf/slope topography which is uniform everywhere except for a localized topographic irregularity, e.g., a submarine canyon. The mean current is specified at the upstream boundary and adjusts to the topography, closely following isobaths through the model domain. The incident BSW signal is then introduced at the upstream boundary either as a harmonic wave or as a pulse of finite duration. The BSW signal scatters its energy into other available wave modes when it encounters the topographic irregularity. The scattered wave field is dominated by evanescent modes which are trapped at the topographic irregularity and appear as intense mesoscale flows between the coast and the mean current. Nonlinear dynamics transform these large‐amplitude evanescent modes into persistent eddy‐like features on the shelf. The nonlinear interaction is much stronger when the current on the shelf associated with the BSW is opposite to the mean current direction (i.e., negative), so anticyclonic eddies are preferentially generated at the topographic irregularity. For a harmonic BSW, an anticyclonic eddy periodically appears when the negative current phase passes and disappears when the positive current phase passes. A BSW pulse with negative velocity at the coast produces a strong anticyclonic eddy which persists, after the pulse has passed, for a time period substantially longer than the pulse duration. A pulse with positive velocity at the coast does not generate any persistent features on the shelf. The anticyclonic eddies produce mass exchange between the shelf and the mean current and could contribute significantly to cross‐shelf exchange on continental shelves.
Response of global upper ocean temperature to changing solar irradiance
Authors: White Warren B. , Lean Judith , Cayan Daniel R. , Dettinger Michael D.
Published: February 2004

By focusing on time sequences of basin‐average and global‐average upper ocean temperature (i.e., from 40°S to 60°N) we find temperatures responding to changing solar irradiance in three separate frequency bands with periods of >100 years, 18–25 years, and 9–13 years. Moreover, we find them in two different data sets, that is, surface marine weather observations from 1990 to 1991 and bathythermograph (BT) upper ocean temperature profiles from 1955 to 1994. Band‐passing basin‐average temperature records find each frequency component in phase across the Indian, Pacific, and Atlantic Oceans, yielding global‐average records with maximum amplitudes of 0.04°±0.01°K and 0.07°±0.01°K on decadal and interdecadal scales, respectively. These achieve maximum correlation with solar irradiance records (i.e., with maximum amplitude 0.5 W m−2 at the top of the atmosphere) at phase lags ranging from 30° to 50°. From the BT data set, solar signals in global‐average temperature penetrate to 80–160 m, confined to the upper layer above the main pycnocline. Operating a global‐average heat budget for the upper ocean yields sea surface temperature responses of 0.01°–0.03°K and 0.02°–0.05°K on decadal and interdecadal scales, respectively, from the 0.1 W m−2 penetration of solar irradiance to the sea surface. Since this is of the same order as that observed (i.e., 0.04°–0.07°K), we can infer that anomalous heat from changing solar irradiance is stored in the upper layer of the ocean.
On an efficient numerical method for modeling sea ice dynamics
Authors: Zhang Jinlun , Hibler W. D.
Published: February 2004

A computationally efficient numerical method for the solution of nonlinear sea ice dynamics models employing viscous‐plastic rheologies is presented. The method is based on a semi‐implicit decoupling of the x and y ice momentum equations into a form having better convergence properties than the coupled equations. While this decoupled form also speeds up solutions employing point relaxation methods, a line successive overrelaxation technique combined with a tridiagonal matrix solver procedure was found to converge particularly rapidly. The procedure is also applicable to the ice dynamics equations in orthogonal curvilinear coordinates which are given in explicit form for the special case of spherical coordinates.
Grain‐scale processes, folding, and stratigraphic disturbance in the GISP2 ice core
Authors: Alley R. B. , Gow A. J. , Meese D. A. , Fitzpatrick J. J. , Waddington E. D. , Bolzan J. F.
Published: February 2004

Flow disturbances have been shown to alter stratigraphic order in the lower part of the ice sheet in central Greenland. Vertical thin sections of the Greenland Ice Sheet Project 2 ice core show that in the lower 30%, the expected c axis‐vertical fabric is interrupted by planes of grains (“stripes”) with c axes oriented approximately in the dip directions of the planes. Stripe‐parallel shear produces small‐scale folds. The stripes can be explained qualitatively by a simple nucleation‐and‐growth model based on the strong anisotropy of ice‐crystal deformation. Nucleation probably is sensitive to spatially variable rates of polygonization, producing spatially variable stripe densities. Stripes are modeled to affect the ice viscosity, so variations in stripe density may contribute to viscosity contrasts that might produce larger deformational features and loss of stratigraphic order.
Dynamics of the vernal bloom in the marginal ice zone of the Barents Sea: Dimethyl sulfide and dimethylsulfoniopropionate budgets
Authors: Matrai Patricia A. , Vernet María
Published: February 2004

Phytoplankton is known to be a key element in the production and eventual oceanic efflux of dimethyl sulfide (DMS) to the atmosphere. We hypothesized that the alternation of Phaeocystis pouchetii and diatoms, the two major algal components of the spring bloom, would modulate the input of particulate organic sulfur (POS), dimethylsulfoniopropionate (DMSP), and DMS into the mixed layer of the marginal ice zone. A bloom of diatoms is expected to present similar pathways but to have very different rates of POS/DMSP/DMS production and POS/DMSP sinking and no or low DMS flux to the atmosphere as contrasted to the cycling occurring during the P. pouchetii phase of the bloom. Our initial hypothesis cannot be accepted based on our observations in the Barents Sea during the spring of 1993. The contribution of diatoms to the water column budgets of DMSP and DMS was significant and cannot be overlooked. We suggest that the physiological stage of the bloom is perhaps more important to biogeochemical cycling than its phytoplankton species composition in controlling DMSP and DMS fluxes in Arctic waters. Loss of paniculate DMSP in the mixed layer was mainly by release into the dissolved pool and by sedimentation father than by grazing, except in ice‐free waters. Cycling of DMS in the mixed layer was predominantly biological in ice‐free waters, while in Polar Front waters, ventilation was proportionally more important due to depressed microbiology.
Seasonal phytoplankton dynamics in the eastern tropical Atlantic
Authors: Monger Bruce , McClain Charles , Murtugudde Ragu
Published: February 2004

The coastal zone color scanner (CZCS) that operated aboard the Nimbus 7 satellite provided extensive coverage of phytoplankton pigment concentrations in the surface waters of the eastern tropical Atlantic (ETA) from March 1979 to February 1980 and coincided with four major research cruises to this region. Total primary production within the ETA (5°N–10°S, 25°W–10°E) was determined from CZCS pigment estimates and an empirical algorithm derived from concurrent in situ data taken along 4°W that relates near‐surface chlorophyll concentration and integrated primary production. We estimated an average annual production for the ETA of 2.3 Gt C yr−1 with an associated 3.5‐fold seasonal variation in the magnitude of this production. We describe the principal physical mechanisms controlling seasonal phytoplankton dynamics within the ETA and propose that in addition to seasonal change in the thermocline depth, one must also consider changes in the depth of the equatorial undercurrent. An extensive validation effort indicates that the standard CZCS global products are a conservative estimate of pigment concentrations in ETA surface waters. Significant underestimates by the CZCS global products were observed in June and July which we attributed, in part, to aerosol correction errors and, more importantly, to errors caused by a significant reduction in the concentration of near‐surface dissolved organic matter that resulted from strong equatorial upwelling.
On the annual variation of tropospheric zonal winds observed above Christmas Island in the central equatorial Pacific
Authors: Gage Kenneth S. , McAfee John R. , Williams Christopher R.
Published: February 2004

Observations of tropospheric winds have been made nearly continuously since early 1986 in the altitude range 2–18 km using a 50 MHz VHF wind profiler at Christmas Island (2°N, 157°W). Tropospheric zonal winds observed at Christmas Island show a pronounced annual variation in the middle to upper troposphere with westerly winds typically observed during northern winter. The annual variation is strongest during La Niña and weakest during El Niño. The amplitude of the cycle has a broad peak in the upper troposphere. Empirical orthogonal function (EOF) analysis of the vertical structure of the annual variation shows that the principal mode explains nearly 90% of the variance in the 90‐ to 365‐day frequency band. We attribute the annual variation in zonal winds to the annual variation in deep tropical heating associated with deep convection. The annual variation in tropical convection gives rise to annual variations in the surface pressure and pressure difference between Darwin and Tahiti. The pressure difference is greatest during northern hemisphere winter months. Other measures of the annual variation in tropical convection are provided by the tropical tropopause height and by highly reflective clouds (HRC). The tropical tropopause is highest during the northern hemisphere winter months when convection is most active over the maritime continent/western Pacific warm pool region and lowest in northern summer when convection is most active over the land masses of the northern hemisphere. The HRC show an annual migration in the centers of active convection. The annual latitudinal migration of the active centers of convection over the western Pacific with respect to the equatorial waveguide appears to be an important factor in determining the annual variation evident in the remote response of the zonal winds observed over Christmas Island.
Global gridded inventories of anthropogenic emissions of sulfur and nitrogen
Authors: Benkovitz Carmen M. , Scholtz M. Trevor , Pacyna Jozef , Tarrasón Leonor , Dignon Jane , Voldner Eva C. , Spiro Peter A. , Logan Jennifer A. , Graedel T. E.
Published: February 2004

Two sets of global inventories of anthropogenic emissions of both oxides of sulfur and oxides of nitrogen for circa 1985 have been produced under the umbrella of the Global Emissions Inventory Activity (GEIA) of the International Global Atmospheric Chemistry Program. The two sets of inventories have different temporal, sectoral, and vertical resolution. Both were compiled using the same data sets; default data sets of global emissions have been refined via the use of more detailed regional data sets. This article reports on the compilation of the annual, one‐vertical‐level inventories, called version 1A; the inventory files are available to the scientific community via anonymous file transform protocol (FTP). Existing global inventories and regional inventories have been updated and combined on a 1° × 1° longitude/latitude grid. The resulting global anthropogenic emissions are 65 Tg S yr−1 and 21 Tg N yr−1; qualitative uncertainty estimates have been assigned on a regional basis. Emissions of both SOx and NOx are strongly localized in the highly populated and industrialized areas of eastern North America and across Europe; other smaller regions of large emissions are associated with densely populated areas with developed industries or in connection with exploitation of fuels or mineral reserves. The molar ratio of nitrogen to sulfur emissions reflects the overall character of sources; its value is generally between 0.33 and 10 for industrialized and heavily populated areas but varies over a wide range for other areas. We suggest that those requiring sulfur or nitrogen emission inventories standardize on the GEIA inventories, which we believe are authoritative and which are freely available to all users by anonymous FTP.
Validation of the UARS solar ultraviolet irradiances: Comparison with the ATLAS 1 and 2 measurements
Authors: Woods T. N. , Prinz D. K. , Rottman G. J. , London J. , Crane P. C. , Cebula R. P. , Hilsenrath E. , Brueckner G. E. , Andrews M. D. , White O. R. , VanHoosier M. E. , Floyd L. E. , Herring L. C. , Knapp B. G. , Pankratz C. K. , Reiser P. A.
Published: February 2004

The measurements of the solar ultraviolet spectral irradiance made by the two Upper Atmosphere Research Satellite (UARS) solar instruments, Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) and SOLar STellar Irradiance Comparison Experiment (SOLSTICE), are compared with same‐day measurements by two solar instruments on the shuttle ATmospheric Laboratory for Applications and Science (ATLAS) missions, ATLAS SUSIM and Shuttle Solar Backscatter UltraViolet (SSBUV) experiment. These measurements from the four instruments agree to within the 2σ uncertainty of any one instrument, which is 5 to 10% for all wavelengths above 160 nm and for strong emission features below 160 nm. Additionally, the long‐term relative accuracy of the two UARS data sets is better than the original 2% goal, especially at wavelengths greater than 160 nm. This level of agreement is credited to accurate preflight calibrations coupled with comprehensive inflight calibrations to track instrument degradation. Two solar irradiance spectra, 119 to 410 nm, are presented; the first combines observations from UARS SUSIM and UARS SOLSTICE taken on March 29, 1992, during the ATLAS 1 mission, and the second combines spectra for April 15, 1993, during the ATLAS 2 mission. The ATLAS 1 mission coincided with the initial decline from the maximum of solar cycle 22 when solar activity was relatively high. The ATLAS 2 mission occurred somewhat later during the declining phase of the solar cycle 22 when solar activity was more moderate.
Temperature dependence of the gas and liquid phase ultraviolet absorption cross sections of HCFC‐123 (CF3CHCl2) and HCFC‐142b (CH3CF2Cl)
Authors: Nayak Akshaya K. , Buckley Thomas J. , Kurylo Michael J. , Fahr Askar
Published: February 2004

The absorption cross sections for HCFC‐123 (CF3CHCl2) and HCFC‐142b (CH3CF2Cl) have been measured in the gas and liquid phases over the temperature range of about 220–330 K. The liquid phase results were converted into effective gas phase cross sections using a wavelength shift procedure, thereby extending the gas phase cross sections to longer wavelengths. The results are compared with other available data and lend increased confidence in atmospheric lifetime calculations for these important industrial alternatives to the fully halogenated chlorofluorocarbons.
Balloon‐borne observations of midlatitude fluorine abundance
Authors: Sen B. , Toon G. C. , Blavier J.‐F. , Fleming E. L. , Jackman C. H.
Published: February 2004

Volume mixing ratio profiles of fluorine source gases (CF2Cl2, CFCl3, CF2ClCFCl2, CHF2Cl, CF4, and SF6) and reservoir gases (COF2 and HF) have been derived from a series of high‐resolution infrared solar spectra recorded by the Jet Propulsion Laboratory MkIV interferometer during a September 1993 balloon flight from Fort Sumner, New Mexico (34°N, 104°W). The total fluorine budget over the 5‐ to 38‐km altitude range has been evaluated by adding these individual measured profiles to modeled predictions for the unmeasured gas COFCl (considered to be at most 6% of the total fluorine budget). The results indicate a steady decrease of total fluorine, with increasing altitude, from a tropospheric value of about 1.82 parts per billion by volume (ppbv) to 1.48 ppbv at 38 km. The latter value, made up entirely of the reservoir species, is commensurate with tropospheric concentrations of fluorine reported in the late 1980s and with time‐dependent two‐dimensional model predictions (1.45 ppbv). Therefore the “age” of the stratospheric air mass estimated from the MkIV fluorine budget is 4–5 years, in agreement with model simulations (≈6 years) and recent ATMOS measurements.
Mechanisms for the heterogeneous hydrolysis of hydrogen chloride, chlorine nitrate and dinitrogen pentoxide on water‐rich atmospheric particle surfaces
Authors: Koch Thomas G. , Banham Sally F. , Sodeau John R. , Horn Andrew B. , McCoustra Martin R. S. , Chesters Michael A.
Published: February 2004

The heterogeneous interaction of the stratospheric reservoir species HCl, ClONO2, and N2O5 with water‐rich polar stratospheric particle mimics is characterized by the formation of solvated ionic products. Simple semiempirical calculations have been used to explain the nature of the species observed in infrared spectroscopic measurements and to elucidate the mechanism by which they are formed. The initial stages of the interaction appear to involve an SN2‐type nucleophilic attack by the oxygen atom of the surface water molecule upon the most accessible electrophilic site of the adsorbing reactant. Mechanistic schemes involving protonated acid intermediates and their subsequent decomposition or hydrolysis can be used to accurately predict and explain the stable reaction products observed spectroscopically under stratospheric conditions.
Reaction of BrONO2 with H2O on submicron sulfuric acid aerosol and the implications for the lower stratosphere
Authors: Hanson D. R. , Ravishankara A. R. , Lovejoy E. R.
Published: February 2004

Uptake of BrONO2 onto submicron sulfuric acid aerosol was studied in a cylindrical flow reactor coupled to a chemical ionization mass spectrometer. On aerosol particles of ∼0.1 μm radius, the reaction of BrONO2 with H2O to produce HOBr and HNO3 is very efficient, with the reaction probability γ ≈ 0.8 for H2SO4‐content ≤ 70 wt%. The equilibrium constant for the gas phase process, BrONO2 + H2O ⇄ HOBr + HNO3, was measured and the heats of formation of the bromine compounds were deduced. The conversion of HOBr back into BrONO2 via reaction with HNO3 can be neglected in the stratosphere. The heterogeneous hydrolysis of BrONO2, followed by photolysis of the HOBr product, is a major source of HOx in the lower stratosphere. The role of bromine as an activator of chlorine is also discussed.
Surface layers on ice
Authors: Knight Charles A.
Published: February 2004

There is a widespread opinion that ice surfaces are covered by a liquid layer at equilibrium, and several treatments of the ice surface describe it as a homogeneous layer with a definable thickness. Arguments are presented that the ice surface cannot have a homogeneous surface layer and that representations of it that use such a layer are not useful approximations. No part of the transition layer on ice can be homogeneous except at a triple point without violating the phase rule. Some experiments suggest the existence of a surprisingly thick transition region at ice surfaces, but others do not. Water apparently does not completely wet ice, since its contact angle on ice close to the triple point appears not to be zero, and sharply faceted growth forms of ice from the vapor close to the melting point also suggest the absence of a thick, liquid, surface transition region.
Source determination from trace gas observations: An orthogonal function approach and results for long‐lived gases with surface sources
Authors: Plumb R. Alan , Zheng Xinyu
Published: February 2004

Differences between measured concentrations of atmospheric trace gases at different locations across the globe contain information about the locations of the sources of these gases. We use an orthogonal function approach and experiments with a three‐dimensional transport model to determine what source distributions can, in principle, be identified from such information. The ability to detect and to locate localized sources is severely limited by the number of observational sites and by the error growth implicit in the inverse problem. The former limitation appears to be the most severe restriction in practice, in contrast to results obtained using two‐dimensional (zonally averaged) models. Differences between results from two and three‐dimensional models are especially severe for tropical sources.