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1982
Talley, LD, McCartney MS.  1982.  Distribution and Circulation of Labrador Sea-Water. Journal of Physical Oceanography. 12:1189-1205.   10.1175/1520-0485(1982)012<1189:dacols>2.0.co;2   AbstractWebsite

Labrador Sea Water is the final product of the cyclonic circulation of Subpolar Mode Water in the open northern North Atlantic (McCartney and Talley, 1982). The temperature and salinity of the convectively formed Subpolar Mode Water decrease from 14.7°C, 36.08‰ to 3.4°C, 34.88‰ on account of the cumulative effects of excess precipitation and cooling. The coldest Mode Water is Labrador Sea Water, which spreads at mid-depths and is found throughout the North Atlantic Ocean north of 40°N and along its western boundary to 18°N.A vertical minimum in potential vorticity is used as the primary tracer for Labrador Sea Water. Labrador Sea Water is advected in three main directions out of the Labrador Sea: 1) northeastward into the Irminger Sea, 2) southeastward across the Atlantic beneath the North Atlantic current, and 3) southward past Newfoundland with the Labrador Current and thence westward into the Slope Water region, crossing under the Gulf Stream off Cape Hatteras.The Labrador Sea Water core is nearly coincident with an isopycnal which also intersects the lower part of the Mediterranean Water, whose high salinity and high potential vorticity balance the low salinity and low potential vorticity of the Labrador Sea Water. Nearly isopycnal mixing between them produces the upper part of the North Atlantic Deep Water.A 27-year data set from the Labrador Sea at Ocean Weather Station Bravo shows decade-long changes in the temperature, salinity, density and formation rate of Labrador Sea Water, indicating that Labrador Sea Water property distributions away from the Labrador Sea are in part due to changes in the source.

Talley, LD, Raymer ME.  1982.  Eighteen Degree Water variability. Journal of Marine Research. 40:757-775. AbstractWebsite

The Eighteen Degree Water of the western North Atlantic is formed by deep convection in winter. The circulation and changing properties of Eighteen Degree Water are studied using hydrographic data from a long time series at the Panulirus station (32 degrees 10'N, 64 degrees 30'W) and from the Gulf Stream '60 experiment. Due to its relative vertical homogeneity, which persists year-round, the Eighteen Degree Water can be identified by its low potential vorticity (f/rho)(partial derivative rho/partial derivative z). The Eighteen Degree Water is formed in an east-west band of varying characteristics offshore of the Gulf Stream. The Eighteen Degree Water formed at the eastern end of the subtropical gyre recirculates westward past the Panulirus station. Renewal of Eighteen Degree Water occurred regularly from 1954 to 1971, ceased from 1972 to 1975, and began again after 1975. The properties (18 degrees C, 36.5 parts per thousand) of Eighteen Degree Water seen at the Panulirus station were nearly uniform from 1954 to 1964. There was a shift in properties in 1964 and by 1972 the Eighteen Degree Water properties were 17.1 degrees C, 36.4 parts per thousand, The new Eighteen Degree Water formed after 1975 had nearly the same characteristics as that of 1954. The density, potential temperature, salinity and the temperature-salinity relation of the entire upper water column at the Panulirus station changed at the same time as the Eighteen Degree Water properties. The upper water column was denser and colder from 1964 to 1975 than from 1954 to 1964 and after 1975.

McCartney, MS, Talley LD.  1982.  The Sub-Polar Mode Water of the North-Atlantic Ocean. Journal of Physical Oceanography. 12:1169-1188.   10.1175/1520-0485(1982)012<1169:tsmwot>2.0.co;2   AbstractWebsite

The warm waters of the subtropical and subpolar basins of the North Atlantic have tight regional temperature-salinity relationships, and are conventionally called the regional “Central Waters.” A volumetric census of the temperature-salinity characteristics of the North Atlantic by Wright and Worthington (1970) shows that waters characterized by certain segments of the T-S relationships have large volumes compared to those of other segments: volumetric “Mode Waters.” Such Mode Waters appear as layers with increased vertical separation between isopycnals-pycnostads. The present study reports on the existence of pycnostads in the central and eastern North Atlantic. These Subpolar Mode Waters are formed by deep winter convection in the subpolar North Atlantic, and participate in the upper water circulation of the northern North Atlantic. The seasonal outcropping of the pycnostads occurs within and adjacent to the North Atlantic Current, the Irminger Current, the East and West Greenland Currents, and the Labrador Current. The warmer pycnostads (10°C<=T<=15°C) recirculate in an anticyclonic subtropical gyre east and south of the North Atlantic Current, causing volumetric modes in the central and eastern subtropical North Atlantic. A branch of the North Atlantic Current carries somewhat heavier and cooler (8°C<=T<=10°C) pycnostads northward past Ireland. The bulk of the current turns westward, but one branch continues northward, providing a warm core to the Norwegian Current (8°C). Within the main westward flow the density continues to increase and temperature to decrease. Southeast of Iceland pycnostad temperatures are near 8°C. Following the cyclonic circulation around the Irminger Sea west of the Reykjanes Ridge the temperature drops to less than 5°C. The cyclonic flow around the Labrador Sea gives a final pycnostad temperature below 3.5°C. The last, coldest, densest pycnostad is the Labrador Sea Water which influences lower latitudes via the southward flowing, Deep Western Boundary Current along the western boundary, and via eastward flow at mid-depth in the North Atlantic Current (Talley and McCartney, 1982).

1983
Talley, LD.  1983.  Radiating Barotropic Instability. Journal of Physical Oceanography. 13:972-987.   10.1175/1520-0485(1983)013<0972:rbi>2.0.co;2   AbstractWebsite

The linear stability of zonal, parallel shear flow on a beta-plane is discussed. While the localized shear region supports unstable waves, the far-field can support Rossby waves because of the ambient potential-vorticity gradient. An infinite zonal flow with a continuous cross-stream velocity gradient is approximated with segments of uniform flow, joined together by segments of uniform potential vorticity. This simplification allows an exact dispersion relation to be found. There are two classes of linearly unstable solutions. One type is trapped to the source of energy and has large growth rates. The second type is weaker instabilities which excite Rossby waves in the far-field: the influence of these weaker instabilities extends far beyond that of the most unstable waves.

Talley, LD.  1983.  Radiating Instabilities of Thin Baroclinic Jets. Journal of Physical Oceanography. 13:2161-2181.   10.1175/1520-0485(1983)013<2161:riotbj>2.0.co;2   AbstractWebsite

The linear stability of thin, quasi-geostrophic, two-layer zonal jets on the β-plane is considered. The meridional structure of the jets is approximated in such a way as to allow an exact dispersion relation to be found. Necessary conditions for instability and energy integrals are extended to these piece-wise continuous profiles. The linearly unstable modes which arise can be related directly to instabilities arising from the vertical and horizontal shear. It is found empirically that the necessary conditions for instability are sufficient for the cases considered. Attention is focused on unstable modes that penetrate far into the locally stable ocean interior and which are found when conditions allow the jet instability phase speeds to overlap the far-field. free-wave phase speeds. These radiating instabilities exist in addition to more unstable waves which are trapped within a few deformation radii of the jet. The growth rates of the radiating instabilities depend strongly on the size of the overlap of instability and free-wave phase speeds. The extreme cases of this are westward jets which have vigorously growing, radiating instabilities and purely eastward jets which do not radiate at all. Radiating instabilities are divided into two types: a subset of the jets' main unstable waves near marginal stability and instabilities which appear to be destabilized free waves of the interior ocean. It is suggested that the fully developed field of instabilities of a zonal current consists of the most unstable, trapped waves directly in the current with a shift to less unstable, radiating waves some distance from the current. A brief comparison of the model results with observations south of the Gulf Stream is made.

1984
Talley, LD.  1984.  Meridional Heat-Transport in the Pacific-Ocean. Journal of Physical Oceanography. 14:231-241.   10.1175/1520-0485(1984)014<0231:mhtitp>2.0.co;2   AbstractWebsite

The heat transported meridionally in the Pacific Ocean is calculated from the surface heat budgets of Clark and Weare and others; both budgets were based on Bunker's method with different radiation formulas. The meridional heat transport is also calculated from the surface heat budget of Esbensen and Kushnir, who used Budyko's method. The heat transport is southward at most latitudes if the numbers of Clark and of Weare are used. It is northward in the North Pacific and southward in the South Pacific if Eshensen and Kushnir's numbers are used. Systematic errors in both calculations appear to be so large that confident determination of even the sign of the heat transport in the North Pacific is not possible. The amount of heat transported poleward by all oceans is obtained from the Pacific Ocean calculation and transports in the Atlantic and Indian Oceans based on Bunker's surface heat fluxes.

McCartney, MS, Talley LD.  1984.  Warm-to-Cold Water Conversion in the Northern North-Atlantic Ocean. Journal of Physical Oceanography. 14:922-935.   10.1175/1520-0485(1984)014<0922:wtcwci>2.0.co;2   AbstractWebsite

A box Model of warm-to-cold-water conversion in the northern North Atlantic is developed and used to estimate conversion rates, given water mass temperatures, conversion paths and rate of air-sea heat exchange. The northern North Atlantic is modeled by three boxes, each required to satisfy heat and mass balance statements. The boxes represent the Norwegian Sea, and a two-layer representation of the open subpolar North Atlantic. In the Norwegian Sea box, warm water enters from the south, is cooled in the cyclonic gyre of the Norwegian–Greenland Sea, and the colder water returns southwards to the open subpolar North Atlantic. Some exchange with the North Polar Sea also is included. The open subpolar North Atlantic has two boxes. In the abyssal box, the dense overflows from the Norwegian Sea flow south, entraining warm water from the upper-ocean box. In the upper-ocean box, warm water enters from the south, supplying the warm water for an upper ocean cyclonic circulation that culminates in production by convection of Labrador Sea Water, and also the warm water that is entrained into the abyss, and the warm water that continues north into the Norwegian Sea. Our estimates are that 14 × 106 m3 s−1 of warm (11.5°C) water flows north to the west of Ireland, with about a third of this branching into the Norwegian Sea. The production rate for Labrador Sea Water is 8.5 × 106 m3 s−1), and this combines with a flow of dense Norwegian Sea Overflow waters (with entrained warmer waters) at 2.5 × 106 m3 s−1 to give a Deep Western Boundary Current of 11 × 106 m3 s−1. The total southward flow east of Newfoundland is this plus 4 × 106 m3 s−1 of cold less dense Labrador Current waters (there is a net southward flow between Newfoundland and Ireland of about 1 × 106 m3 s−1 supplied by northward flow through the Bering Strait, passing through the North Polar Sea to enter the Norwegian Sea.

1985
Talley, LD.  1985.  Ventilation of the Sub-Tropical North Pacific - the Shallow Salinity Minimum. Journal of Physical Oceanography. 15:633-649.   10.1175/1520-0485(1985)015<0633:votsnp>2.0.co;2   AbstractWebsite

The shallow salinity minimum of the subtropical North Pacific is shown to be a feature of the ventilated, wind-driven circulation. Subduction of low salinity surface water in the northeastern subtropical gyre beneath higher salinity water to the south causes the salinity minimum. Variation of salinity along surface isopycnals causes variations in density and salinity at the minimum.A model of ventilated flow is used to demonstrate how the shallow salinity minimum can arise. The model is modified to account for nonzonal, realistic winds; it is also extended to examine the three-dimensional structure of the western shadow zone. The boundary between the subtropical and subpolar gyres is given by the zero of the zonal integral of Ekman pumping. The western shadow zone fills the subtropical gyre at the base of the ventilated layers and decreases in extent with decreasing density. For parameters appropriate to the North Pacific, the eastern shadow zone is of very limited extent.Observations of salinity and potential vorticity within and below the ventilated layer bear out model predictions of the extent of the western shadow zone.

1986
Joyce, TM, Warren BA, Talley LD.  1986.  The Geothermal Heating of the Abyssal Sub-Arctic Pacific-Ocean. Deep-Sea Research Part a-Oceanographic Research Papers. 33:1003-1015.   10.1016/0198-0149(86)90026-9   AbstractWebsite

Recent deep CTD-O2 measurements in the abyssal North Pacific along 175°W, 152°W, and 47°N indicate large-scale changes in the O-S characteristics in the deepest kilometer of the water column. Geothermal heat flux from the abyssal sediments can be invoked as the agent for causing large-scale modification of abyssal temperatures (but not salinities) in the subarctic Pacific Ocean. East-west and north-south thermal age differences of about 100 years are inferred using a spatially uniform geothermal heat flux of 5 x 10-2 WrmW m-2.

Talley, LD, de Szoeke RA.  1986.  Spatial Fluctuations North of the Hawaiian Ridge. Journal of Physical Oceanography. 16:981-984.   10.1175/1520-0485(1986)016<0981:sfnoth>2.0.co;2   AbstractWebsite

A closely spaced hydrographic section from Oabu, Hawaii to 28°N, 152°W and then north along 152°W shows strong eddy or current features with dynamic height signatures of about 30 dyn cm across 150 km and associated geostrophic surface velocities of approximately 60 cm s−1. Two such features are found between Hawaii and the Subtropical Front, which is located at 32°N. Similar features have been observed on a number of other hydrographic and XBT sections perpendicular to the Hawaiian Ridge. It is hypothesized that the features are semipermanent, are due to the presence of the Ridge, and are related to the North Hawaiian Ridge Current of Mysak and Magaard.

1987
Talley, LD, White WB.  1987.  Estimates of Time and Space Scales at 300-Meters in the Midlatitude North Pacific from the Transpac-Xbt Program. Journal of Physical Oceanography. 17:2168-2188.   10.1175/1520-0485(1987)017<2168:eotass>2.0.co;2   AbstractWebsite

Estimates of length and time scales of temperature variability at 300 meters in the midlatitude North Pacific are made. Data are XBT traces collected from 1976 to 1984 in the TRANSPAC Volunteer Observing Ship program. Temperatures at 300 meters are grouped in two-mouth bins and gridded using the Surface II mapping program.Temperature variance about the time mean is largest in the Kuroshio Extension and nearly constant in the eastern North Pacific. A cooling trend occurred in the eastern North Pacific over the eight years of the dataset. In the western Pacific, the annual cycle is most intense 1°–2° north of the Kuroshio Extension, with an indication of meridional propagation away from the region of most intense variability. Propagation of annual waves in the eastern Pacific was predominantly northwestward.Wavenumber and frequency spectra are computed from normalized temperatures with the mean and bimonthly average removed in order to eliminate the dominant annual cycle. Based on the overall temperature variance, the North Pacific was divided into western and eastern regions. Zonal wavenumber and frequency spectra and two-dimensional ω/k spectra were computed for a number of latitudes in the eastern and western regions. Two-dimensional k/l spectra were also computed for the western and eastern regions. The spectra indicate westward propagation throughout the midlatitude North Pacific with additional eastward propagation in the Kuroshio Extension region, shorter length and time scales in the Kuroshio Extension compared with other regions, and slight dominance of southwestward propagation in bath the eastern and western North Pacific.Tests to determine the effective spatial resolution of the dataset indicate that local average-station spacing is a good measure of local Nyquist wavelength. However, because of the nearly random sampling in a spatially limited region, an unresolved wave is aliased more or less in a band stretching towards low wavenumber rather than folded in coherent, predictable locations in the spectrum. With the choice of a two-month time bin, spectra are about equally aliased in space and time, with Nyquist wavelength and period close to the beginning of energy rolloff reported in other surveys, which have better spatial resolution but less degrees of freedom.

1988
Talley, LD.  1988.  Potential Vorticity Distribution in the North Pacific. Journal of Physical Oceanography. 18:89-106.   10.1175/1520-0485(1988)018<0089:pvditn>2.0.co;2   AbstractWebsite

Vertical sections and maps of potential vorticity ρ−1f∂ρ/∂z for the North Pacific are presented. On shallow isopycnals, high potential vorticity is found in the tropics, subpolar gyre, and along the eastern boundary of the subtropical gyre, all associated with Ekman upwelling. Low potential vorticity is found in the western subtropical gyre (subtropical mode water), in a separate patch near the sea surface in the eastern subtropical gyre and extending around the gyre, and near sea-surface outcrops in the subpolar gyre; the last is analogous to the subpolar mode water of the North Atlantic and Southern Ocean.Meridional gradients of potential vorticity are high between the subtropical and subpolar gyres at densities which outcrop only in the subpolar gyre; lateral gradients of potential vorticity are low in large regions of the subtropical gyre on these isopycnals. On slightly denser isopycnals which do not outcrop in the North Pacific, there are large regions of low potential vorticity gradients which cross the subtropical-subpolar gyre boundary. These regions decrease in area with depth and vanish between 2500 and 3000 meters. Regions of low lateral gradients of potential vorticity are surrounded by and overlie regions where the meridional gradient of potential vorticity is approximately β. In the abyssal waters, below 3500 meters, meridional potential vorticity gradients again decrease, perhaps associated with slow geothermal heating. The depth and shape of the region wheel potential vorticity is relatively uniform or possesses closed contours is noted and related to theories of wind-driven circulation.

1989
Salmon, R, Talley LD.  1989.  Generalizations of Arakawas Jacobian. Journal of Computational Physics. 83:247-259.   10.1016/0021-9991(89)90118-6   AbstractWebsite

A simple method yields discrete Jacobians that obey analogues of the differential properties needed to conserve energy and enstrophy in 2-dimensional flow. The method is actually independent of the type of discretization and thus applies to an arbitrary representation in gridpoints, finite elements, or spectral modes, or to any mixture of the three. We illustrate the method by deriving simple energy- and enstrophy-conserving Jacobians for an irregular triangular mesh in a closed domain, and for a mixed gridpoint-and-mode representation in a semi-infinite channel.

1991
Bingham, FM, Talley LD.  1991.  Estimates of Kuroshio Transport Using an Inverse Technique. Deep-Sea Research Part a-Oceanographic Research Papers. 38:S21-S43.   10.1016/S0198-0149(12)80003-3   AbstractWebsite

Two CTD/hydrographic sections across the Kuroshio were combined using an inverse technique to estimate the absolute transport. The hydrographic data were obtained as part of a transpacific section across 24-degrees-N in 1985. The inverse technique treats the two sections as ends of a channel and conserves mass flowing into and out of the channel as a whole and within certain discrete layers. The strong topographic constraints imposed by the region of the East China Sea resulted in transport estimates independent of the initial reference level for the geostrophic calculation. The calculated transports were 26.6 Sv northwest of Okinawa and 21.9 Sv across the Tokara Straits. The accuracy of the estimate was approximately 3.3 Sv for the Okinawa section and 5.1 Sv for the Tokara Straits section. The principal errors in the calculation came from lack of knowledge of the flow in the shallow areas of both sections, inadequate sampling of the rapidly varying topography, an estimate of 5 Sv transport in the Tsushima Current and Osumi branch of the Kuroshio and uncertainty over the relative weighting given in the inverse solutions to the different sections. A set of acoustic Doppler current profiler (ADCP) data taken simultaneously was combined with the inverse model. Because initial mass imbalances were smaller, the combined model gave a better estimate of transport than that of the model using the CTD data alone. Two different methods of using the ADCP data in the inverse model were compared. It was found to be preferable to use the ADCP data as an initial reference for the geostrophic velocities, rather than as a set of separate constraints.

Talley, LD.  1991.  An Okhotsk Sea-Water Anomaly - Implications for Ventilation in the North Pacific. Deep-Sea Research Part a-Oceanographic Research Papers. 38:S171-S190.   10.1016/S0198-0149(12)80009-4   AbstractWebsite

An unusually cold, fresh and oxygenated layer of water centered at a pressure of 800 dbar and sigma-theta of 27.4 was found at a CTD station in the western Pacific at 43-degrees-5'N, 153-degrees-20'E in August 1985. The anomaly was part of a larger pattern of less dramatic but nevertheless higher variance at densities up to 27.6-sigma-theta in the mixed water region of the Oyashio and Kuroshio, south of the Bussol' Strait, which connects the Sea of Okhotsk and the open North Pacific. Isopycnal maps indicate that the source of the anomaly, which was embedded in a cyclonic flow, was the Okhotsk Sea. Surface properties in the Okhotsk Sea, based on all available NODC observations, and isopycnal maps indicate that the layer probably did not originate at the sea surface in open water. Instead, the principal modifying influences at densities of 26.8-27.6-sigma-theta in the North Pacific are sea-ice formation and vertical mixing, the latter primarily in the Kuril Straits. A simple calculation shows that most of the low salinity influence at these densities in the North Pacific can originate in the Okhotsk Sea and that vertical mixing in the open North Pacific may be much less important than previously thought.

Talley, LD, Joyce TM, de Szoeke RA.  1991.  Transpacific Sections at 47-Degrees-N and 152-Degrees-W - Distribution of Properties. Deep-Sea Research Part a-Oceanographic Research Papers. 38:S63-S82.   10.1016/S0198-0149(12)80005-7   AbstractWebsite

Three CTD/hydrographic sections with closely-spaced stations were occupied between May 1984 and May 1987, primarily in the subpolar North Pacific. Vertical sections of CTD quantities, oxygen and nutrients are presented. Upper water properties suggest that the Subarctic Front is located south of the subtropical/subpolar gyre boundary at 152-degrees-W, that there is leakage of North Pacific Intermediate Water from the subtropical to the subpolar gyre in the eastern Pacific, and verify the poleward shift of the subtropical gyre center with depth. At intermediate depths (1000-2000 m), a separation between the western and eastern parts of the subpolar gyre is found at 180-degrees along 47-degrees-N. Abyssal waters are oldest in the northeast, with primary sources indicated at the western boundary and north of the Hawaiian Ridge. Properties and geostrophic velocity from detailed crossings of the boundary trenches suggest that flow in the bottom of the Kuril-Kamchatka Trench at the western boundary at 42-degrees-N and 47-degrees-N is northward. Very narrow boundary layers at intermediate depths are revealed in silica, as well as in the dynamical properties, at both the western and northern boundaries, and probably reflect southward and westward flow.

1992
Talley, LD, Joyce TM.  1992.  The Double Silica Maximum in the North Pacific. Journal of Geophysical Research-Oceans. 97:5465-5480.   10.1029/92jc00037   AbstractWebsite

The North Pacific has two vertical silica maxima. The well-known intermediate maximum occurs between 2000 and 2500 m with a potential density relative to 2000 dbar of 36.90 in the northeastern Pacific. The deep maximum, which has not been observed extensively before, is found at or near the ocean bottom in the northern North Pacific in a narrow latitude range. Maps of silica on isopycnals which intersect the intermediate and bottom maxima show that the lowest silica is found in the western tropical North Pacific, suggesting a route for the spread of South Pacific water into the deep North Pacific. Low-silica water is found along the western boundary of the North Pacific, with a separate broad tongue south of Hawaii. The highest silica on both isopycnals is in the northeast Pacific. A bottom maximum in the Cascadia Basin in the northeastern Pacific can be differentiated from both open-ocean maxima. Four sources for the vertical maxima are considered: in situ dissolution of sinking panicles, bottom sediment dissolution, hydrothermal venting, and upslope advection in the northeastern Pacific. Because not enough is known about any of these sources, only rough estimates of their contributions can be made. The bottom maximum is most likely to result from bottom sediment dissolution but requires a flux larger than some current direct estimates. The Cascadia Basin bottom maximum may result from both bottom sediment dissolution and hydrothermal venting. The intermediate maximum is likely to result primarily from dissolution of sinking particles. There is no quantitative estimate of the effect of possible upslope advection or enhancement of bottom fluxes due to the Columbia River outflow.

Yuan, XJ, Talley LD.  1992.  Shallow Salinity Minima in the North Pacific. Journal of Physical Oceanography. 22:1302-1316.   10.1175/1520-0485(1992)022<1302:ssmitn>2.0.co;2   AbstractWebsite

CTD/STD data from 24 cruises in the North Pacific are studied for their vertical salinity structure and compared to bottle observations. A triple-salinity minimum is found in two separated regions in the eastern North Pacific. In the first region, bounded by the northern edge of the subarctic frontal zone and the 34-degrees-N front between 160-degrees and 150-degrees-W, a middle salinity minimum is found below the permanent pycnocline in the density range of 26.0 and 26.5 sigma(theta). This middle minimum underlies Reid's shallow salinity minimum and overlies the North Pacific Intermediate Water (NPIW). In the second region, southeast of the first, a seasonal salinity minimum appears above the shallow salinity minimum at densities lower than 25.1 sigma(theta). The shallow salinity minimum and the NPIW can be found throughout year, while the seasonal minimum only appears in summer and fall. The middle and shallow salinity minima, as well as the seasonal minimum, originate at the sea surface in the northeast Pacific. The properties at the minima depend on the surface conditions in their source areas. The source of the middle minimum is the winter surface water in a narrow band between the gyre boundary and the subarctic front west of 170-degrees-W. The shallow salinity minimum is generated in winter and is present throughout the year. The seasonal salinity minimum has the same source area as the shallow salinity minimum but is formed in summer and fall at lower density and is not present in winter. A tropical shallow salinity minimum found south of 18-degrees-N does not appear to be connected with the shallow salinity minimum in the eastern North Pacific. South of 20-degrees-N, the shallow salinity minimum and the NPIW appear to merge into a thick, low salinity water mass. When an intrusion of high salinity water breaks through this low salinity water mass south of 18-degrees-N, this tropical salinity minimum appears at the same density as the shallow salinity minimum. Though the water mass of the tropical minimum is derived from the water in the shallow salinity minimum, the formation of the vertical minimum is different.

Tsuchiya, M, Talley LD, McCartney MS.  1992.  An Eastern Atlantic Section from Iceland Southward across the Equator. Deep-Sea Research Part a-Oceanographic Research Papers. 39:1885-1917.   10.1016/0198-0149(92)90004-d   AbstractWebsite

A long CTD/hydrographic section with closely-spaced stations was occupied in July-August 1988 from Iceland southward to 3-degrees-S along a nominal longitude of 20-degrees-W. The section extends from the surface down to the bottom, and spans the entire mid-ocean circulation regime of the North Atlantic from the subpolar gyre through the subtropical gyre and the equatorial currents. Vertical sections of potential temperature, salinity and potential density from CTD measurements and of oxygen, silica, phosphate and nitrate, based on discrete water-sample measurements are presented and discussed in the context of the large-scale circulation of the North Atlantic Ocean. The close spacing of high-quality stations reveals some features not described previously. The more important findings include: (1) possible recirculation of the lightest Subpolar Mode Water into the tropics; (2) a thermostad at temperatures of 8-9-degrees-C, lying below that of the Equatorial 13-degrees-C Water; (3) the nutrient distribution in the low-salinity water above the Mediterranean Outflow Water that supports the previous conjecture of northern influence of the Antarctic Intermediate Water; (4) a great deal of lateral structure of the Mediterranean Outflow Water, with a number of lobes of high salinity; (5) an abrupt southern boundary of the Labrador Sea Water at the Azores-Biscay Rise and a vertically well-mixed region to its south; (6) a sharp demarcation in the central Iceland Basin between the newest Iceland-Scotland Overflow Water and older bottom water, which has a significant component of southern water; (7) evidence that the Northeast Atlantic Deep Water is a mixture of the Mediterranean Outflow Water and the Northwest Atlantic Bottom Water with very little input from the Iceland-Scotland Overflow Water; (8) an isolated core of the high-salinity, low-silica Upper North Atlantic Deep Water at the equator; (9) a core of the high-oxygen, low-nutrient Lower North Atlantic Deep Water pressed against the southern flank of the Mid-Atlantic Ridge just south of the equator; (10) a weak minimum of salinity, and well-defined maxima of nutrients associated with the oxygen minimum that separates the Middle and Lower North Atlantic Deep Waters south of the equator; (11) a large body of nearly homogeneous water beneath the Middle North Atlantic Deep Water between 20-degrees-N and the Azores-Biscay Rise; and (12) a deep westward boundary undercurrent on the southern slope of the Rockall Plateau.

1993
Talley, LD.  1993.  Distribution and Formation of North Pacific Intermediate Water. Journal of Physical Oceanography. 23:517-537.   10.1175/1520-0485(1993)023<0517:dafonp>2.0.co;2   AbstractWebsite

The North Pacific Intermediate Water (NPIW), defined as the main salinity minimum in the subtropical North Pacific, is examined with respect to its overall property distributions. These suggest that NPIW is formed only in the northwestern subtropical gyre; that is, in the mixed water region between the Kuroshio Extension and Oyashio front. Subsequent modification along its advective path increases its salinity and reduces its oxygen. The mixed water region is studied using all bottle data available from the National Oceanographic Data Center, with particular emphasis on several winters. Waters from the Oyashio, Kuroshio, and the Tsugaru Warm Current influence the mixed water region, with a well-defined local surface water mass formed as a mixture of the surface waters from these three sources. Significant salinity minima in the mixed water region are grouped into those that are directly related to the winter surface density and are found at the base of the oxygen-saturated surface layer, and those that form deeper, around warm core rings. Both could be a source of the more uniform NPIW to the east, the former through preferential erosion of the minima from the top and the latter through simple advection. Both sources could exist all year with a narrowly defined density range that depends on winter mixed-layer density in the Oyashio region.

1994
Talley, LD, Johnson GC.  1994.  Deep, Zonal Subequatorial Currents. Science. 263:1125-1128.   10.1126/science.263.5150.1125   AbstractWebsite

Large-scale, westward-extending tongues of warm (Pacific) and cold (Atlantic) water are found between 2000 and 3000 meters both north and south of the equator in the Pacific and Atlantic oceans. They are centered at 5-degrees to 8-degrees north and 10-degrees to 15-degrees south (Pacific) and 5-degrees to 8-degrees north and 15-degrees to 20-degrees south (Atlantic). They are separated in both oceans by a contrasting eastward-extending tongue, centered at about 1-degrees to 2-degrees south, in agreement with previous helium isotope observations (Pacific). Thus, the indicated deep tropical westward flows north and south of the equator and eastward flow near the equator may result from more general forcing than the hydrothermal forcing previously hypothesized.

Tsuchiya, M, Talley LD, McCartney MS.  1994.  Water-Mass Distributions in the Western South-Atlantic - a Section from South Georgia Island (54s) Northward across the Equator. Journal of Marine Research. 52:55-&.   10.1357/0022240943076759   AbstractWebsite

A long CTD/hydrographic section with closely spaced stations was made in February-April 1989 in the western Atlantic Ocean between 0-degrees-40'N and South Georgia (54S) along a nominal longitude of 25W. Vertical sections of various properties from CTD and discrete water-sample measurements are presented and discussed in terms of the large-scale circulation of the South Atlantic Ocean. One of the most important results is the identification of various deep-reaching fronts in relation to the large-scale circulation and the distribution of mode waters. Five major fronts are clearly defined in the thermal and salinity fields. These are the Polar (49.5S), Subantarctic (45S), Subtropical (41-42S), Brazil Current (35S) Fronts, and an additional front at 20-22S. The first three are associated with strong baroclinic shear. The Brazil Current Front is a boundary between the denser and lighter types of the Subantarctic Mode Water (SAMW), and the 20-22S front marks the boundary between the anticyclonic subtropical and cyclonic subequatorial gyres. The latter front coincides with the northern terminus of the high-oxygen tongue of the Antarctic Intermediate Water (AAIW) and also with the abrupt shift in density of the high-silica tongue originating in the Upper Circumpolar Water and extending northward. Two pycnostads with temperatures 20-24-degrees-C are observed between 10S and 25S with the denser one in the subtropical and the other lighter one in the subequatorial gyre. A weak thermostad centered at 4-degrees-C occurs in the AAIW between the Subtropical Front and the Subantarctic Front and shows characteristics similar to the densest variety of the SAMW. Another significant result is a detailed description of the complex structure of the deep and bottom waters. The North Atlantic Deep Water (NADW) north of 25S contains two vertical maxima of oxygen (at 2000 m and 3700 m near the equator) separated by intervening low-oxygen water with more influence from the Circumpolar Water. Each maximum is associated with a maximum of salinity and minima of nutrients. The deeper salinity maximum is only weakly defined and is limited to north of 18S, appearing more as vertically uniform salinity. South of 25S the NADW shows only a single maximum of salinity, a single maximum of oxygen, and a single minimum of each nutrient, all lying close together. The salinity maximum south of 25S and the deeper oxygen/salinity maximum north of 1 IS are derived from the same source waters. The less dense NADW containing the shallower extrema of characteristics turns to the east at lower latitudes and does not reach the region south of 25S. The southward spreading of the NADW is interrupted by domains of intensified circumpolar characteristics. This structure is closely related to the basin-scale gyre circulation pattern. The Weddell Sea Deep Water is the densest water we observed and forms a relatively homogeneous layer at the bottom of the Georgia and Argentine Basins. The bottom layer of the Brazil Basin is occupied by the vertically and laterally homogeneous Lower Circumpolar Water.

1995
Talley, LD, Nagata Y.  1995.  PICES Working Group I: Review of the Okhotsk Sea and Oyashio Region. PICES Scientific Report. 2:227.: North Pacific Marine Science Organization (PICES) Abstract
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Talley, LD, Nagata Y, Fujimura M, Iwao T, Kono T, Inagake D, Hirai M, Okuda K.  1995.  North Pacific Intermediate Water in the Kuroshio Oyashio Mixed Water Region. Journal of Physical Oceanography. 25:475-501.   10.1175/1520-0485(1995)025<0475:npiwit>2.0.co;2   AbstractWebsite

The North Pacific Intermediate Water (NPIW) orginates as a vertical salinity minimum in the mixed water region (MWR) between the Kuroshio and Oyashio, just east of Japan. Salinity minima in this region are examined and related to the water mass structures, dynamical features, and winter mixed layer density of waters of Oyashio origin. Stations in the MWR are divided into five regimes, of which three represent source waters (from the Kuroshio, Oyashio, and Tsugaru Current) and two are mixed waters formed from these three inputs. Examination of NPIW at stations just east of the MWR indicates that the mixed waters in the MWR are the origin of the newest NPIW. Multiple salinity minima with much finestructure are seen throughout the MWR in spring 1989, with the most fragmented occurring around the large warm core ring centered at 37 degrees N, 144 degrees E, suggesting that this is a dominant site for salinity minimum formation. The density of the NPIW in the MWR is slightly higher than the apparent late winter surface density of the subpolar water. It is hypothesized that the vertical mixing that creates interfacial layers above the salinity minima also increases the density of the minima to the observed NPIW density. Transport of new intermediate water (26.65-27.4 sigma(theta)) eastward out of the MWR is about 6 Sv (Sv = 10(6)m(3)s(-1)), of which roughly 45% is of Oyashio origin and the other 55% of Kuroshio origin. Therefore, the transport of subpolar water into the subtropical gyre in the western North Pacific is estimated to be about 3 Sv.