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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.

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.

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   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.

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   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.

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   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.

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.  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   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.

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   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   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.

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

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   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   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).