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1999
Talley, LD.  1999.  Some aspects of ocean heat transport by the shallow, intermediate and deep overturning circulations. Mechanisms of global climate change at millennial time scales. ( Clark PU, Webb RS, Keigwin LD, Eds.).:1-22., Washington, DC: American Geophysical Union Abstract
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1998
Zhang, HM, Talley LD.  1998.  Heat and buoyancy budgets and mixing rates in the upper thermocline of the Indian and global oceans. Journal of Physical Oceanography. 28:1961-1978.   10.1175/1520-0485(1998)028<1961:habbam>2.0.co;2   AbstractWebsite

Diapycnal and diathermal diffusivity values in the upper thermocline are estimated from buoyancy and heat budgets for water volumes bounded by isopycnals and isotherms, the air-sea interface, and coastline where applicable. Comprehensive analysis is given to the Indian Ocean, with an extended global general description. The Indian Ocean,gains buoyancy in the north (especially in the northeast) and loses buoyancy in the subtropical south. Freshest and least-dense water appears in the Bay of Bengal and isopycnals outcrop southwestward from there and then southward. Computation of diapycnal diffusivity (K-p) starts from the Bay of Bengal, expanding southwestward and southward and with depth. As isopycnals extend equatorward from the northeast and with increasing depth, K-p remains at about 1.3 cm(2) s(-1) for 20.2 sigma(theta) (Bay of Bengal) to 22.0 sigma(theta) (northeast Indian Ocean). Farther south (poleward) and at greater depth, K-p decreases from 0.9 cm(2) s(-1) for 23.0 sigma(theta) (north of 20 degrees S) to 0.5 cm(2) s(-1) for 25.0 sigma(theta) (north of 35 degrees S). Isotherms outcrop poleward from the equator. Diathermal diffusivity values computed from the heat budget are large at the equator and near the surface (4.0 cm(2) s(-1) for 28.5 degrees C isotherm) but decrease rapidly poleward and with depth (1.3 cm(2) s(-1) for 27.0 degrees C). This indicates stronger mixing either near the equator or the surface, or a possible component in the diathermal direction of the larger isopycnal diffusivity, as isotherms do not follow isopycnals in the upper Indian Ocean north of 10 degrees S. For the 21.0 degrees C isotherm? which closely follows isopycnal 25.0 sigma(theta), the heat budget yields a K-theta again of 0.5 cm(2) s(-1), the value of the diapycnal diffusivity. For the Indian-Pacific system, K-rho decreases from 1.3 cm(2) s(-1) for 22.0 sigma(theta) (the warm pool water, depth similar to 60 m) to 0.9 cm(2) s(-1) for 23.0 sigma(theta) (the tropical water between 20 degrees N and 20 degrees S, depth similar to 100 m), and to 0.1 cm(2) s(-1) for 25.0 sigma(theta) (40 degrees N-40 degrees S, depth similar to 170 m). In the eastern tropical Pacific, K-rho = 1.1 cm(2) s(-1) for 21.5 sigma(theta) (depth similar to 25 m) while K-rho = 0.6 cm(2) s(-1) for 22.0 sigma(theta) (depth similar to 35 m). In the Atlantic, K-rho = 0.6 cm(2) s(-1) for 24.0 sigma(theta) between 20 degrees N and 15 degrees S (depth similar to 80 m), and 0.2 cm(2) s(-1) for 25.0 sigma(theta) between 30 degrees N and 35 degrees S (depth similar to 120 m). For the water volume bounded by 25.5 sigma(theta) farther south and north (50 degrees N-40 degrees S), air-sea buoyancy gain in the Tropics is about the size of the buoyancy loss in the subtropics, and the near-zero net flux may not have significance compared to the errors in the data. For 27.5 sigma(theta), which encompasses the large region from about 65 degrees N to the Antarctic (with midocean average depth of 400 m), K-rho is 0.2 cm(2) s(-1). The results indicate that mixing strength generally decreases poleward and with depth in the upper ocean.

Tsuchiya, M, Talley LD.  1998.  A Pacific hydrographic section at 88 degrees W: Water-property distribution. Journal of Geophysical Research-Oceans. 103:12899-12918.   10.1029/97jc03415   AbstractWebsite

Full-depth conductivity-temperature-depth (CTD)/hydrographic measurements with high horizontal and vertical resolution were made in February-April 1993 along a line lying at a nominal longitude of 88 degrees W and extending from southern Chile (54 degrees S) to Guatemala (14 degrees N). It crossed five major deep basins (Southeast Pacific, Chile, Peru, Panama, and Guatemala basins) east of the East Pacific Rise. Vertical sections of potential temperature, salinity, potential density, oxygen, silica, phosphate, nitrate, and nitrite are presented to illustrate the structure of the entire water column. Some features of interest found in the sections are described, and an attempt is made to interpret them in terms of the isopycnal property distributions associated with the large-scale ocean circulation. These features include: various near-surface waters observed in the tropical and subtropical regions and the fronts that mark the boundaries of these waters; the possible importance of salt fingering to the downward salt transfer from the high-salinity subtropical water; a shallow thermostad (pycnostad) developed at 16 degrees-18.5 degrees C in the subtropical water; low-salinity surface water in the subantarctic zone west of southern Chile; large domains of extremely low oxygen in the subpycnocline layer on both sides of the equator and a secondary nitrite maximum associated with a nitrate minimum in these low-oxygen domains; high-salinity, low-oxygen, high-nutrient subpycnocline water that is carried poleward along the eastern boundary by the Peru-Chile Undercurrent; the Subantarctic Mode and Antarctic Intermediate waters; middepth isopycnal property extrema observed at the crest of the Sala y Gomez Ridge; influences of the North Pacific and the North Atlantic upon deep waters along the section; and the characteristics and sources of the bottom waters in the five deep basins along the section.

Talley, LD, Fryer G, Lumpkin R.  1998.  Physical oceanography of the tropical Pacific. Geography of the Pacific Islands. ( Rapaport M, Ed.).:19-32., Honolulu: Bess Press Abstract
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1997
Gordon, AL, Ma SB, Olson DB, Hacker P, Ffield A, Talley LD, Wilson D, Baringer M.  1997.  Advection and diffusion of Indonesian throughflow water within the Indian Ocean South Equatorial Current. Geophysical Research Letters. 24:2573-2576.   10.1029/97gl01061   AbstractWebsite

Warm, low salinity Pacific water weaves through the Indonesian Seas into the eastern boundary of the Indian Ocean. The Indonesian Throughflow Water (ITW) adds freshwater into the Indian Ocean as it spreads by the advection and diffusion within the Indian Ocean's South Equatorial Current (SEC). The low salinity throughflow trace, centered along 12 degrees S, stretches across the Indian Ocean, separating the monsoon dominated regime of the northern Indian Ocean from the more typical subtropical stratification to the south. ITW is well represented within the SEC thermocline, extending with concentrations above 80% of initial characteristics from the sea surface to 300-m within the eastern half of the Indian Ocean, with 60% concentration reaching well into the western Indian Ocean. The ITW transport within the SEC varies from 4 to 12 x 10(6) m(3)sec(-1), partly in response to variations of the injection rate at the eastern boundary and to the likelihood of a zonally elongated recirculation cell between the Equatorial Counter Current and the SEC within the Indian Ocean. Lateral mixing disperses the ITW plume meridionally with an effective isopycnal mixing coefficient of 1.1 to 1.6 x 10(4) m(2)sec(-1).

Johnson, GC, Talley LD.  1997.  Deep tracer and dynamical plumes in the tropical Pacific Ocean. Journal of Geophysical Research-Oceans. 102:24953-24964.   10.1029/97jc01913   AbstractWebsite

Anomalous middepth plumes in potential temperature-salinity, theta-S, and buoyancy frequency squared, N-2, Originate east of the East Pacific Rise Crest and decay toward the west. Conductivity-temperature-depth (CTD) data from recent hydrographic sections at 15 degrees S and 10 degrees N are used together with meridional sections at 110 degrees, 135 degrees, and 151 degrees W to map these structures. Warm salty plumes west of the rise crest have maxima centered at 2700 m, 10 degrees S and 8 degrees N, and are interrupted by a cold, fresh tongue centered at 2900 m, 2 degrees S. The theta-S anomalies decay to half their peak strength 2800 km to the west of the rise crest, +/-300 km in the meridional, and +/-0.4 km in the vertical. Vertical N-2 minima occur within the plumes, regions of reduced vertical gradients in theta and S. These minima are underlain by maxima near the depth of the rise crest, about 3200 m. The N-2 plumes decay more rapidly to the west of the rise crest than do the theta-S plumes. The N-2 structure is consistent with a pair of stacked gyres in each hemisphere. There are at least three possible mechanisms consistent with some aspects of these features. First, a deep maximum in upwelling somewhere below 2700 m would result in equatorvard and westward interior flow at 2700 m. advecting these plumes along with it. Second, rapid upwelling of warm, salty, unstratified water in the eastern basins could result in westward overflows over the rise crest. Third, upwelling and associated entrainment processes owing to hydrothermal venting could result in stacked counter-rotating gyres west of the rise crest.

McCarthy, MC, Talley LD, Baringer MO.  1997.  Deep upwelling and diffusivity in the southern Central Indian Basin. Geophysical Research Letters. 24:2801-2804.   10.1029/97gl02112   AbstractWebsite

Transport of the deepest water westward through a gap at 28 degrees S in the Ninetyeast Ridge between the Central Indian Basin and the West Australia Basin is calculated from hydrographic data collected as part of WOCE Hydrographic Program section I8N. Zero reference velocity levels at mid-depth were chosen through consideration of water masses. The small transport of 1.0 Sv westward of water denser than sigma(4) = 45.92 kg m(-3) through the gap must all upwell in the southern Central Indian Basin. Of this, 0.7 Sv upwells between the central and western sill sections, that is, close to the sill itself. Using the areas covered by the isopycnal, we calculate an average vertical velocity of 3.3 . 10(-3) cm s(-1) close to the sill and of 4.2 . 10(-4) cm s(-1) west of the sill. Associated average vertical diffusivities are 105 cm(2) s(-1) close to the sill and 13 cm(2) s(-1) west of the sill, in this bottom layer.

Talley, LD, Baringer MO.  1997.  Preliminary results from WOCE hydrographic sections at 80 degrees E and 32 degrees S in the central Indian Ocean. Geophysical Research Letters. 24:2789-2792.   10.1029/97gl02657   AbstractWebsite

The hydrographic properties and circulation along sections at 80 degrees E and 32 degrees S in March, 1995, in the Indian Ocean are described very briefly. A halocline was well-developed in the tropics. A westward coastal jet of fresh Bay of Bengal water was present at the sea surface at Sri Lanka with eastward flow of saline Arabian Sea water below. The Equatorial Undercurrent was well developed as were the deep equatorial jets. The Indonesian throughflow jet presented a large dynamic signature at 10 to 14 degrees S coinciding with a strong front in all properties to great depth. Its mid-depth salinity minimum is separated from that of the Antarctic Intermediate Water. The Subantarctic Mode Water of the southeastern Indian Ocean imparts its high oxygen ventilation signature to the whole of the transects, including the tropical portion. The deepest water in the Central Indian Basin is pooled in the center of the basin, and its principal source appears to be the sill at 11 degrees S through the Ninetyeast Ridge. Northward deep water transports across the 32 degrees S section were similar to those observed in 1987 but the deep water was lower in oxygen and fresher than in 1987. Upper ocean waters at 32 degrees S were more saline and warmer in 1995.

Talley, LD.  1997.  North Pacific intermediate water transports in the mixed water region. Journal of Physical Oceanography. 27:1795-1803.   10.1175/1520-0485(1997)027<1795:npiwti>2.0.co;2   AbstractWebsite

Initial mixing between the subtropical and subpolar waters of Kuroshio and Oyashio origin occurs in the mixed water region (interfrontal zone) between the Kuroshio and Oyashio. The relatively fresh water that enters the Kuroshio Extension from the Mixed Water Region is this already mixed subtropical transition water. Subtropical transition water in the density range 26.64-27.4 sigma(theta) can be considered to be the newest North Pacific Intermediate Water (NPIW) in the subtropical gyre; this density range is approximately that which is ventilated in the subpolar gyre with significant influence from the Okhotsk Sea. Freshening of the Kuroshio Extension core occurs between 140 degrees and 165 degrees E in the upper part of the NPIW (26.64-27.0 sigma(theta)), with the greatest freshening associated with the eastern side of the first and second Kuroshio meanders. Kuroshio Extension freshening in the lower part of the NPIW (27.0-27.4 sigma(theta)) occurs more gradually and farther to the east. There is nearly no distinction in water properties north and south of the Kuroshio Extension by 175 degrees W. The upper part of the NPIW in the Mixed Water Region progresses from very intrusive and including much freshwater in the west, to much smoother and more saline water in the east. The lower part of the NPIW in the mixed water region progresses from very intrusive and fresh in the far west, to noisy and more saline at 152 degrees E, to smooth and fresher in the east. These suggest a difference between the two layers in both advection direction and possibly transport across the Subarctic Front. Assuming that all waters in the region are an isopycnal mixture of subtropical and subpolar water, the zonal transport of subpolar water in the subtropical gyre at 152 degrees E is estimated at about 3 Sv (Sv = 10(6) m(3) s(-1)). This could be approximately one-quarter of the Oyashio transport in this density range.

1996
Talley, LD.  1996.  North Atlantic circulation and variability, reviewed for the CNLS conference. Physica D. 98:625-646.   10.1016/0167-2789(96)00123-6   AbstractWebsite

The circulation and water mass structure of the North Atlantic are reviewed, with emphasis on the large-scale overturning cell which produces North Atlantic Deep Water (NADW). Properties and transports for its major components (Nordic Seas Overflow Water, Labrador Sea Water, Mediterranean Water, Antarctic Intermediate Water and Antarctic Bottom Water) are reviewed. The transport estimates and properties of NADW coupled with the observed meridional heat transport in the Atlantic limit the temperature of northward flow which replenishes the NADW to the range 11-15 degrees C. The high salinity of the North Atlantic compared with other ocean basins is important for its production of intermediate and deep waters; about one third of its higher evaporation compared with the North Pacific is due to the Mediterranean. The evaporation/precipitation balance for the North Atlantic is similar to the Indian and South Atlantic Oceans; the difference between the North and South Atlantic may be that high evaporation in the North Atlantic affects much greater depths through Mediterranean Water production. Also described briefly is variability of water properties in the upper layers of the subtropical/subpolar North Atlantic, as linked to the North Atlantic Oscillation. The oceanographic time series at Bermuda is then used to show decadal variations in the properties of the Subtropical Mode Water, a thick layer which lies in the upper 500 m. Salinity of this layer and at the sea surface increases during periods when the North Atlantic westerlies weaken between Iceland and the Azores and shift southwestward. (The North Atlantic Oscillation index is low during these periods). Temperature at the surface and in this layer are slightly negatively correlated with salinity, decreasing when salinity increases. It is hypothesized that the salinity increases result from incursion of saline water from the eastern subtropical gyre forced by the southward migration of the westerlies, and that the small temperature decreases are due to increased convection in the Sargasso Sea, also resulting from the southward shift of the westerlies.

Tsuchiya, M, Talley LD.  1996.  Water-property distributions along an eastern Pacific hydrographic section at 135W. Journal of Marine Research. 54:541-564.   10.1357/0022240963213583   AbstractWebsite

As part of the World Ocean Circulation Experiment, full-depth CTD/hydrographic measurements with high horizontal and vertical resolutions were made in June-August 1991 along a line extending from 34N to 33S at a nominal longitude of 135W with an additional short leg that connects it to the California coast roughly along 34N. The line spans the major part of the subtropical and intertropical circulation regime of the eastern North and South Pacific. The primary purpose of this paper is to present vertical sections of various properties from CTD and discrete water-sample measurements along this line and to give an overview of some important features as a basis for more comprehensive basin-scale studies. These features include: the frontal structures found in the surface-layer salinity field in the North Pacific; relatively high-salinity water that dominates the subpycnocline layer between the equator and 17N; troughs of the subpycnocline isopycnals for 26.8-27.5 sigma(theta) found at 12N and 12.5S; a permanent thermostad at 9-10 degrees C observed between 4.5N and 15N; the pycnostad of the Subantarctic Mode Water centered at 27.0-27.05 sigma(theta) and developed south of 22S; two types of the Antarctic Intermediate Water representing the subtropical and equatorial circulation regimes; a thick tongue of high silica centered at 3000 m (45.8 sigma(4)) and extending southward across the entire section; deep (2000-3000 m) westward flows at 5-8N and 10-15S separated by an eastward flow at 1-2S; and dense, cold, oxygen-rich, nutrient-poor bottom waters, which are associated with fracture zones and believed to represent the pathways of eastward flows into the Northeast Pacific Basin of the bottom waters separated from the northward-flowing western boundary undercurrent. This work once again demonstrates the usefulness of long lines of high-quality, high-resolution hydrographic stations such as the one described herein in advancing the understanding of the large-scale ocean circulation.

Yuan, XJ, Talley LD.  1996.  The subarctic frontal zone in the North Pacific: Characteristics of frontal structure from climatological data and synoptic surveys. Journal of Geophysical Research-Oceans. 101:16491-16508.   10.1029/96jc01249   AbstractWebsite

The subarctic front is a thermohaline structure across the North Pacific, separating colder, fresher water to the north from warmer, saltier water to the south. Levitus's [1982] data and 72 conductivity-temperature-depth/salinity-temperature-depth sections are used to show the spatial and seasonal variations of the climatological frontal zone and the characteristics of the frontal structure in synoptic surveys. The temperature gradient in the mean frontal zone is stronger in the western Pacific and decreases eastward, while the salinity gradient has less variation across the Pacific. The temperature gradient also has larger seasonal variation, with a maximum in spring, than the salinity gradient. The synoptic surveys show that the frontal zone is narrower and individual fronts tend to be stronger in the western Pacific than in the eastern Pacific. Density gradients tend to be more compensated at the strongest salinity fronts than at the strongest temperature fronts. A horizontal minimum of vertical stability is found south of the subarctic halocline outcrop. The northern boundary of the North Pacific Intermediate Water merges with the frontal zone west of 175 degrees W and is north of the northern boundary of the subarctic frontal zone in the eastern Pacific. The shallow salinity minima start within the subarctic frontal zone in the eastern Pacific.

Talley, LD.  1996.  Antarctic Intermediate Water in the South Atlantic. The South Atlantic : present and past circulation. ( Wefer G, Berger WH, Siedler G, Webb D, Eds.).:219-238., Berlin ; New York: Springer Abstract
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Talley, LD.  1996.  Physical oceanography. Encylopedia of Earth Sciences. :745-749., New York: MacMillan Publishing Abstract
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1995
Speer, KG, Siedler G, Talley L.  1995.  The Namib Col Current. Deep-Sea Research Part I-Oceanographic Research Papers. 42:1933-1950.   10.1016/0967-0637(95)00088-7   AbstractWebsite

Recent measurements indicate the transatlantic extent of the Namib Col Current at depths of 1300-3000 m near Lat. 22 degrees S in the South Atlantic Ocean. This current forms a continuous circulation structure from the Namib Col on the Walvis Ridge to the western trough, though its characteristic change as deepwater with varying properties enters and leaves the current owing to a meridional flow component. Transport estimates from hydrographic sections on the Walvis Ridge and at 15 degrees W near the crest of the Mid-Atlantic Ridge indicate a strength of about 3 x 10(6) m(3) s(-1) The current is part of a larger-scale eastward Row at Lon. 25 degrees W; transport estimates across the salinity maximum core there show a similar strength. Associated with this high-salinity high-oxygen current is a basin-wide front in these properties of varying intensity (weaker in the east) marking the transition to deep water whose North Atlantic characteristics have been partly erased by mixing with Circumpolar Deep Water in the southwest South Atlantic. The water which finally crosses the Walvis Ridge is supplied both by the eastward flow of this (diluted) North Atlantic Deep Water and by a general southeastward interior flow from the northern Angola Basin. Evidence suggests that this deep water continues south in the eastern Cape Basin, leaving the South Atlantic near the African continent.

Suga, T, Talley LD.  1995.  Antarctic Intermediate Water Circulation in the Tropical and Subtropical South-Atlantic. Journal of Geophysical Research-Oceans. 100:13441-13453.   10.1029/95jc00858   AbstractWebsite

Recent hydrographic data from the South Atlantic Ventilation Experiment cruises and others are combined with historical data and used to map the isopycnal properties corresponding to the Antarctic Intermediate Water (AAIW) in the Atlantic Ocean. The low salinity of the AAIW extends eastward across the South Atlantic just south of the equator (3-4 degrees S). Evidence of a weak eastward flow just north of the equator (1-2 degrees N) is also shown. Lateral and vertical homogenization of properties in the AAIW is found at the equator between 2 degrees S and 2 degrees N; there is no clear zonal gradient in salinity just along the equator. These observations suggest enhanced mixing within the equatorial baroclinic deformation radius. The South Atlantic tropical gyre is shown to consist of the following three cells: one cyclonic cell centered at about 7 degrees S, another centered at about 19 degrees S in the west and 23 degrees S in the east, and one anticyclonic cell centered at about 13 degrees S. These cells are associated with a westward extension at 10 degrees S of high salinity and low oxygen which originates in the eastern tropical South Atlantic and a front in these properties at about 15 degrees S in the west and about 20 degrees S in the east.

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.

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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1994
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.

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.

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.

1992
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.

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.

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.