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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   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.

Yun, JY, Talley LD.  2003.  Cabbeling and the density of the North Pacific Intermediate Water quantified by an inverse method. Journal of Geophysical Research-Oceans. 108   10.1029/2002jc001482   AbstractWebsite

North Pacific Intermediate Water (NPIW), defined as the main salinity minimum in the subtropical North Pacific, at a density of 26.7-26.8sigma(theta), is denser than the winter surface water in the Oyashio which is the source of the salinity minimum. We showed previously that cabbeling and double diffusion during mixing between the Oyashio water and more saline Kuroshio water can account for the density increase from the surface source water to the salinity minimum. An inverse method is employed herein to quantify the effect of cabbeling, using CTD data from the western North Pacific. The difference between proportional mixing between parcels of Oyashio and Kuroshio waters and mixing along isopycnals is exploited to compute the convergence of water into density layers. The diapycnal transport convergence associated with cabbeling into the NPIW density layer is estimated to be 0.56 Sv for an assumed turnover time of 1 year in the region between 142degreesE and 152degreesE. Diapycnal transport convergences in the regions 152degreesE-165degreesE, 165degreesE-175degreesW, and 175degreesW-136degreesW are similarly estimated by assuming longer turnover times. We estimate that the total diapycnal transport convergence into the NPIW density layer may be up to 2.3 Sv in the entire NPIW region.

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   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.

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.

Williams, NL, Juranek LW, Johnson KS, Feely RA, Riser SC, Talley LD, Russell JL, Sarmiento JL, Wanninkhof R.  2016.  Empirical algorithms to estimate water column pH in the Southern Ocean. Geophysical Research Letters. 43:3415-3422.   10.1002/2016gl068539   AbstractWebsite

Empirical algorithms are developed using high-quality GO-SHIP hydrographic measurements of commonly measured parameters (temperature, salinity, pressure, nitrate, and oxygen) that estimate pH in the Pacific sector of the Southern Ocean. The coefficients of determination, R-2, are 0.98 for pH from nitrate (pH(N)) and 0.97 for pH from oxygen (pH(Ox)) with RMS errors of 0.010 and 0.008, respectively. These algorithms are applied to Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) biogeochemical profiling floats, which include novel sensors (pH, nitrate, oxygen, fluorescence, and backscatter). These algorithms are used to estimate pH on floats with no pH sensors and to validate and adjust pH sensor data from floats with pH sensors. The adjusted float data provide, for the first time, seasonal cycles in surface pH on weekly resolution that range from 0.05 to 0.08 on weekly resolution for the Pacific sector of the Southern Ocean.

Williams, NL, Feely RA, Sabine CL, Dickson AG, Swift JH, Talley LD, Russell JL.  2015.  Quantifying anthropogenic carbon inventory changes in the Pacific sector of the Southern Ocean. Marine Chemistry. 174:147-160.   10.1016/j.marchem.2015.06.015   AbstractWebsite

The Southern Ocean plays a major role in mediating the uptake, transport, and long-term storage of anthropogenic carbon dioxide (CO2) into the deep ocean. Examining the magnitude and spatial distribution of this oceanic carbon uptake is critical to understanding how the earth's carbon system will react to continued increases in this greenhouse gas. Here, we use the extended multiple linear regression technique to quantify the total and anthropogenic change in dissolved inorganic carbon (DIC) along the S04P and P16S CLIVAR/U.S. Global Ocean Carbon and Repeat Hydrography Program lines south of 67 degrees S in the Pacific sector of the Southern Ocean between 1992 and 2011 using discrete bottle measurements from repeat occupations. Along the S04P section, which is located in the seasonal sea ice zone south of the Antarctic Circumpolar Current in the Pacific, the anthropogenic component of the DIC increase from 1992 to 2011 is mostly found in the Antarctic Surface Water (AASW, upper 100 m), while the increase in DIC below the mixed layer in the Circumpolar Deep Water can be primarily attributed to either a slowdown in circulation or decreased ventilation of deeper, high CO2 waters. In the AASW we calculate an anthropogenic increase in DIC of 12-18 mu mol kg(-1) and an average storage rate of anthropogenic CO2 of 0.10 +/- 0.02 mol m(-2) yr(-1) for this region compared to a global average of 0.5 +/- 0.2 mol m(-2) yr(-1). In surface waters this anthropogenic CO2 uptake results in an average pH decrease of 0.0022 +/- 0.0004 pH units yr(-1), a 0.47 +/- 0.10% yr(-1) decrease in the saturation state of aragonite (Omega(Aragonite)) and a 2.0 +/- 0.7 m yr(-1) shoaling of the aragonite saturation horizons (calculated for the Omega(Aragonite) = 1.3 contour). (C) 2015 Published by Elsevier B.V.

Williams, NL, Juranek LW, Feely RA, Johnson KS, Sarmiento JL, Talley LD, Dickson AG, Gray AR, Wanninkhof R, Russell JL, Riser SC, Takeshita Y.  2017.  Calculating surface ocean pCO(2) from biogeochemical Argo floats equipped with pH: An uncertainty analysis. Global Biogeochemical Cycles. 31:591-604.   10.1002/2016gb005541   AbstractWebsite

More than 74 biogeochemical profiling floats that measure water column pH, oxygen, nitrate, fluorescence, and backscattering at 10 day intervals have been deployed throughout the Southern Ocean. Calculating the surface ocean partial pressure of carbon dioxide (pCO(2sw)) from float pH has uncertainty contributions from the pH sensor, the alkalinity estimate, and carbonate system equilibrium constants, resulting in a relative standard uncertainty in pCO(2sw) of 2.7% (or 11 mu atm at pCO(2sw) of 400 mu atm). The calculated pCO(2sw) from several floats spanning a range of oceanographic regimes are compared to existing climatologies. In some locations, such as the subantarctic zone, the float data closely match the climatologies, but in the polar Antarctic zone significantly higher pCO(2sw) are calculated in the wintertime implying a greater air-sea CO2 efflux estimate. Our results based on four representative floats suggest that despite their uncertainty relative to direct measurements, the float data can be used to improve estimates for air-sea carbon flux, as well as to increase knowledge of spatial, seasonal, and interannual variability in this flux. Plain Language Summary The Southern Ocean is a key player in the global flow of carbon, yet it is hard to reach, and there are relatively few measurements there, especially in winter. Measuring the amount of carbon dioxide gas in seawater is key to advancing our understanding of the Southern Ocean. More than 74 robotic floats that use sensors to measure seawater properties have been deployed throughout the Southern Ocean, and each has a lifetime of around 5 years. It is currently not possible to directly measure carbon dioxide gas from these floats; however, it is possible to estimate carbon dioxide from things that the float can measure, like pH, a measure of ocean acidity. Here surface ocean carbon dioxide is estimated from several floats and compared to two ship-based estimates. In some locations, the floats closely match the existing estimates, but in other locations the floats see significantly higher surface ocean carbon dioxide in the wintertime, reinforcing the idea that the Southern Ocean's role in the global carbon cycle needs a closer look. Our results show that despite not measuring carbon dioxide directly, these floats will help scientists learn a lot about the Southern Ocean's part in the global flow of carbon.

Whalen, CB, MacKinnon JA, Talley LD, Waterhouse AF.  2015.  Estimating the mean diapycnal mixing using a finescale strain parameterization. Journal of Physical Oceanography. 45:1174-1188.   10.1175/jpo-d-14-0167.1   AbstractWebsite

Finescale methods are currently being applied to estimate the mean turbulent dissipation rate and diffusivity on regional and global scales. This study evaluates finescale estimates derived from isopycnal strain by comparing them with average microstructure profiles from six diverse environments including the equator, above ridges, near seamounts, and in strong currents. The finescale strain estimates are derived from at least 10 nearby Argo profiles (generally <60 km distant) with no temporal restrictions, including measurements separated by seasons or decades. The absence of temporal limits is reasonable in these cases, since the authors find the dissipation rate is steady over seasonal time scales at the latitudes being considered (0 degrees-30 degrees and 40 degrees-50 degrees). In contrast, a seasonal cycle of a factor of 2-5 in the upper 1000m is found under storm tracks (30 degrees-40 degrees) in both hemispheres. Agreement between the mean dissipation rate calculated using Argo profiles and mean from microstructure profiles is within a factor of 2-3 for 96% of the comparisons. This is both congruous with the physical scaling underlying the finescale parameterization and indicates that the method is effective for estimating the regional mean dissipation rates in the open ocean.

Whalen, CB, MacKinnon JA, Talley LD.  2018.  Large-scale impacts of the mesoscale environment on mixing from wind-driven internal waves. Nature Geoscience. 11:842-+.   10.1038/s41561-018-0213-6   AbstractWebsite

Oceanic mesoscale structures such as eddies and fronts can alter the propagation, breaking and subsequent turbulent mixing of wind-generated internal waves. However, it has been difficult to ascertain whether these processes affect the global-scale patterns, timing and magnitude of turbulent mixing, thereby powering the global oceanic overturning circulation and driving the transport of heat and dissolved gases. Here we present global evidence demonstrating that mesoscale features can significantly enhance turbulent mixing due to wind-generated internal waves. Using internal wave-driven mixing estimates calculated from Argo profiling floats between 30 degrees and 45 degrees N, we find that both the amplitude of the seasonal cycle of turbulent mixing and the response to increases in the wind energy flux are larger to a depth of at least 2,000 m in the presence of a strong and temporally uniform field of mesoscale eddy kinetic energy. Mixing is especially strong within energetic anticyclonic mesoscale features compared to cyclonic features, indicating that local modification of wind-driven internal waves is probably one mechanism contributing to the elevated mixing observed in energetic mesoscale environments.

Whalen, CB, Talley LD, MacKinnon JA.  2012.  Spatial and temporal variability of global ocean mixing inferred from Argo profiles. Geophysical Research Letters. 39:n/a-n/a.   10.1029/2012GL053196   AbstractWebsite

The influence of turbulent ocean mixing transcends its inherently small scales to affect large scale ocean processes including water-mass transformation, stratification maintenance, and the overturning circulation. However, the distribution of ocean mixing is not well described by sparse ship-based observations since this mixing is both spatially patchy and temporally intermittent. We use strain information from Argo float profiles in the upper 2,000 m of the ocean to generate over 400,000 estimates of the energy dissipation rate, indicative of ocean mixing. These estimates rely on numerous assumptions, and do not take the place of direct measurement methods. Temporally averaged estimates reveal clear spatial patterns in the parameterized dissipation rate and diffusivity distribution across all the oceans. They corroborate previous observations linking elevated dissipation rates to regions of rough topography. We also observe heightened estimated dissipation rates in areas of high eddy kinetic energy, as well as heightened diffusivity in high latitudes where stratification is weak. The seasonal dependence of mixing is observed in the Northwest Pacific, suggesting a wind-forced response in the upper ocean.

Waterhouse, AF, MacKinnon JA, Nash JD, Alford MH, Kunze E, Simmons HL, Polzin KL, St Laurent LC, Sun OM, Pinkel R, Talley LD, Whalen CB, Huussen TN, Carter GS, Fer I, Waterman S, Garabato ACN, Sanford TB, Lee CM.  2014.  Global patterns of diapycnal mixing from measurements of the turbulent dissipation rate. Journal of Physical Oceanography. 44:1854-1872.   10.1175/jpo-d-13-0104.1   AbstractWebsite

The authors present inferences of diapycnal diffusivity from a compilation of over 5200 microstructure profiles. As microstructure observations are sparse, these are supplemented with indirect measurements of mixing obtained from(i) Thorpe-scale overturns from moored profilers, a finescale parameterization applied to (ii) shipboard observations of upper-ocean shear, (iii) strain as measured by profiling floats, and (iv) shear and strain from full-depth lowered acoustic Doppler current profilers (LADCP) and CTD profiles. Vertical profiles of the turbulent dissipation rate are bottom enhanced over rough topography and abrupt, isolated ridges. The geography of depth-integrated dissipation rate shows spatial variability related to internal wave generation, suggesting one direct energy pathway to turbulence. The global-averaged diapycnal diffusivity below 1000-m depth is O(10(-4))m(2) s(-1) and above 1000-m depth is O(10(-5))m(2) s(-1). The compiled microstructure observations sample a wide range of internal wave power inputs and topographic roughness, providing a dataset with which to estimate a representative global-averaged dissipation rate and diffusivity. However, there is strong regional variability in the ratio between local internal wave generation and local dissipation. In some regions, the depth-integrated dissipation rate is comparable to the estimated power input into the local internal wave field. In a few cases, more internal wave power is dissipated than locally generated, suggesting remote internal wave sources. However, at most locations the total power lost through turbulent dissipation is less than the input into the local internal wave field. This suggests dissipation elsewhere, such as continental margins.

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.

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.

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.

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.

Treguier, AM, Theetten S, Chassignet EP, Penduff T, Smith R, Talley L, Beismann JO, Boning C.  2005.  The North Atlantic subpolar gyre in four high-resolution models. Journal of Physical Oceanography. 35:757-774.   10.1175/jpo2720.1   AbstractWebsite

The authors present the first quantitative comparison between new velocity datasets and high-resolution models in the North Atlantic subpolar gyre [1/10 degrees Parallel Ocean Program model (POPNA10), Miami Isopycnic Coordinate Ocean Model (MICOM), 1/6 degrees Atlantic model (ATL6), and Family of Linked Atlantic Ocean Model Experiments (FLAME)]. At the surface, the model velocities agree generally well with World Ocean Circulation Experiment (WOCE) drifter data. Two noticeable exceptions are the weakness of the East Greenland coastal current in models and the presence in the surface layers of a strong southwestward East Reykjanes Ridge Current. At depths, the most prominent feature of the circulation is the boundary current following the continental slope. In this narrow flow, it is found that gridded float datasets cannot be used for a quantitative comparison with models. The models have very different patterns of deep convection, and it is suggested that this could be related to the differences in their barotropic transport at Cape Farewell. Models show a large drift in watermass properties with a salinization of the Labrador Sea Water. The authors believe that the main cause is related to horizontal transports of salt because models with different forcing and vertical mixing share the same salinization problem. A remarkable feature of the model solutions is the large westward transport over Reykjanes Ridge [10 Sv (Sv = 10(6) m(3) s(-1)) or more].

Tishchenko, PY, Talley LD, Lobanov VB, Zhabin IA, Luchm VA, Nedashkovskii AP, Sagalaev SG, Chichkin RV, Shkirnikova EM, Ponomarev VI, Masten D, Kang DJ, Kim KR.  2003.  Seasonal variability of the hydrochemical conditions in the sea of Japan. Oceanology. 43:643-655. AbstractWebsite

In the summer of 1999 and the winter of 2000, during international expeditions of R/Vs Professor Khromov and Roger Revelle, hydrological and hydrochemical studies of the Sea of Japan were performed. Comparing the hydrochemical characteristics of the Sea of Japan in the summer and winter seasons, we have found that the seasonal variability affects not only the upper quasihomogeneous layer but also the deeper layers. This variability is caused by the intensification of vertical mixing during the winter season. It was shown that the mixing intensification in the deep layers of the sea in the winter might be caused both by the slope convection and by the deep convection in the open part of the sea, penetrating deeper than 1000 in. It was found that the area of positive values of the biological constituent of the apparent oxygen consumption coincides with the area of deep convection. The climatic zoning in the distribution of partial pressure of carbon dioxide was revealed for both seasons. In the northwestern part of the sea, carbon dioxide is released into the atmosphere due to the deep convection in the winter and the heating process in the summer. The southern part of the sea absorbs the atmospheric carbon dioxide because of the process of photosynthesis and cooling of the waters supplied from the Korea Strait.

Tishchenko, PY, Talley LD, Nedashkovskii AP, Sagalaev SG, Zvalinskii VI.  2002.  Temporal variability of the hydrochemical properties of the waters of the Sea of Japan. Oceanology. 42:795-803. AbstractWebsite

Hydrochemical studies were performed in the Sea of Japan from onboard R/V Akademik Vinogradov in 1992 and R/Vs Roger Revelle and Professor Khromov in 1999. A comparison of the hydrochemical properties (concentrations of dissolved oxygen and nutrients and proteins of the carbonate system) of the waters of the Sea of Japan with those of the adjacent basins (the Sea of Okhotsk, Pacific Ocean, and East China Sea) demonstrates significant differences between them. In addition, a significant temporal variability of the hydrochemical properties of the intermediate and abyssal waters of the Sea of Japan was revealed. A general increase in the contents of inorganic forms of phosphorus, nitrogen, and normalized organic matter along with a general decrease in the oxygen concentration and normalized alkalinity with time was established. We suggest a model for an open basin, in which the principal reason for the observed features and temporal variability of the hydrochemical properties is related to the water exchange between the Sea of Japan and adjacent basins. A supposition is posed on the strong dependence of the water exchange on the variability of the intensity analysis direction of the major currents of the northwestern Pacific Ocean, especially the Kuroshio Current.

Tishchenko, PY, Talley LD, Lobanov VB, Nedashkovskii AP, Pavlova GY, Sagalaev SG.  2007.  The influence of geochemical processes in the near-bottom layer on the hydrochemical characteristics of the waters of the Sea of Japan. Oceanology. 47:350-359.   10.1134/s0001437007030071   AbstractWebsite

According to the results of the international expedition aboard the R/Vs Roger Revelle and Professor Khromov in the summer 1999, areas with low oxygen contents (below 210 mu M/kg) and those with increased contents of dissolved inorganic carbon and phosphates were found that roughly coincided with one another. These areas are located near the bottom on the southwestern slope of the Tsushima Basin in the region of the Korea Strait and on the continental slope in the region of the Tatar Strait in the northern part of the sea at about 46 degrees N. The set of hydrochemical data points to a high geochemical activity in the near-bottom layer of the areas noted. This activity is confirmed by direct observations of the composition of the interstitial water in the sediments collected in the northern part of the sea during the expedition of R/V Akademik M.A. Lavrent'ev in 2003. It was supposed that the main cause of the increased geochemical activity is the runoff of suspended and dissolved matter from the Korea and Tatar straits. In the areas mentioned, the near-bottom waters are characterized by low values of the nitrogen-phosphorus ratio (below 10), which is geochemical proof of the denitrification process occurring under the conditions of high oxygen concentrations characteristic of the Sea of Japan. Based on the value of the annual production in the Sea of Japan, a rate of denitrification equal to 3.4 x 10(12) gN/year was calculated. Hence, it is confirmed that the geochemical processes in the near-bottom layer have a direct influence on the spatiotemporal characteristics of the hydrochemical properties of the waters of the Sea of Japan.

Tamsitt, V, Talley LD, Mazloff MR.  2019.  A deep eastern boundary current carrying Indian deep water south of Australia. Journal of Geophysical Research: Oceans. 124:2218-2238.   10.1029/2018jc014569   Abstract

In the Southern Hemisphere, the ocean's deep waters are predominantly transported from low to high latitudes via boundary currents. In addition to the Deep Western Boundary Currents, pathways along the eastern boundaries of the southern Atlantic, Indian, and Pacific transport deep water poleward into the Southern Ocean where these waters upwell to the sea surface. These deep eastern boundary currents and their physical drivers are not well characterized, particularly those carrying carbon and nutrient-rich deep waters from the Indian and Pacific basins. Here we describe the poleward deep eastern boundary current that carries Indian Deep Water along the southern boundary of Australia to the Southern Ocean using a combination of hydrographic observations and Lagrangian experiments in an eddy-permitting ocean state estimate. We find strong evidence for a deep boundary current carrying the low-oxygen, carbon-rich signature of Indian Deep Water extending between 1,500 and 3,000 m along the Australian continental slope, from 30°S to the Antarctic Circumpolar Current southwest of Tasmania. From the Lagrangian particles it is estimated that this pathway transports approximately 5.8 ± 1.3 Sv southward from 30°S to the northern boundary of the Antarctic Circumpolar Current. The volume transport of this pathway is highly variable and is closely correlated with the overlying westward volume transport of the Flinders Current.

Tamsitt, V, Drake HF, Morrison AK, Talley LD, Dufour CO, Gray AR, Griffies SM, Mazloff MR, Sarmiento JL, Wang J, Weijer W.  2017.  Spiraling pathways of global deep waters to the surface of the Southern Ocean. Nature Communications. 8:172.   10.1038/s41467-017-00197-0   Abstract

Upwelling of global deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. However, the exact pathways and role of topography in Southern Ocean upwelling remain largely unknown. Here we show detailed upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution models. The analysis reveals that the northern-sourced deep waters enter the Antarctic Circumpolar Current via southward flow along the boundaries of the three ocean basins, before spiraling southeastward and upward through the Antarctic Circumpolar Current. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the Antarctic Circumpolar Current, with a spatially nonuniform distribution. The timescale for half of the deep water to upwell from 30° S to the mixed layer is ~60–90 years.

Tamsitt, V, Talley LD, Mazloff MR, Cerovecki I.  2016.  Zonal variations in the Southern Ocean heat budget. Journal of Climate. 29:6563-6579.   10.1175/JCLI-D-15-0630.1   AbstractWebsite

The spatial structure of the upper ocean heat budget in the Antarctic Circumpolar Current (ACC) is investigated using the ⅙°, data-assimilating Southern Ocean State Estimate (SOSE) for 2005–10. The ACC circumpolar integrated budget shows that 0.27 PW of ocean heat gain from the atmosphere and 0.38 PW heat gain from divergence of geostrophic heat transport are balanced by −0.58 PW cooling by divergence of Ekman heat transport and −0.09 PW divergence of vertical heat transport. However, this circumpolar integrated balance obscures important zonal variations in the heat budget. The air–sea heat flux shows a zonally asymmetric pattern of ocean heat gain in the Indian and Atlantic sectors and ocean heat loss in the Pacific sector of the ACC. In the Atlantic and Indian sectors of the ACC, the surface ocean heat gain is primarily balanced by divergence of equatorward Ekman heat transport that cools the upper ocean. In the Pacific sector, surface ocean heat loss and cooling due to divergence of Ekman heat transport are balanced by warming due to divergence of geostrophic heat advection, which is similar to the dominant heat balance in the subtropical Agulhas Return Current. The divergence of horizontal and vertical eddy advection of heat is important for warming the upper ocean close to major topographic features, while the divergence of mean vertical heat advection is a weak cooling term. The results herein show that topographic steering and zonal asymmetry in air–sea exchange lead to substantial zonal asymmetries in the heat budget, which is important for understanding the upper cell of the overturning circulation.

Tamsitt, V, Abernathey RP, Mazloff MR, Wang J, Talley LD.  2018.  Transformation of deep water masses along Lagrangian upwelling pathways in the Southern Ocean. Journal of Geophysical Research: Oceans.   10.1002/2017JC013409   AbstractWebsite

Upwelling of northern deep waters in the Southern Ocean is fundamentally important for the closure of the global meridional overturning circulation and delivers carbon and nutrient‐rich deep waters to the sea surface. We quantify water mass transformation along upwelling pathways originating in the Atlantic, Indian, and Pacific and ending at the surface of the Southern Ocean using Lagrangian trajectories in an eddy‐permitting ocean state estimate. Recent related work shows that upwelling in the interior below about 400 m depth is localized at hot spots associated with major topographic features in the path of the Antarctic Circumpolar Current, while upwelling through the surface layer is more broadly distributed. In the ocean interior upwelling is largely isopycnal; Atlantic and to a lesser extent Indian Deep Waters cool and freshen while Pacific deep waters are more stable, leading to a homogenization of water mass properties. As upwelling water approaches the mixed layer, there is net strong transformation toward lighter densities due to mixing of freshwater, but there is a divergence in the density distribution as Upper Circumpolar Deep Water tends become lighter and dense Lower Circumpolar Deep Water tends to become denser. The spatial distribution of transformation shows more rapid transformation at eddy hot spots associated with major topography where density gradients are enhanced; however, the majority of cumulative density change along trajectories is achieved by background mixing. We compare the Lagrangian analysis to diagnosed Eulerian water mass transformation to attribute the mechanisms leading to the observed transformation.

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
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.