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Llanillo, PJ, Pelegri JL, Talley LD, Pena-Izquierdo J, Cordero RR.  2018.  Oxygen pathways and budget for the Eastern South Pacific Oxygen Minimum Zone. Journal of Geophysical Research-Oceans. 123:1722-1744.   10.1002/2017jc013509   AbstractWebsite

Ventilation of the eastern South Pacific Oxygen Minimum Zone (ESP-OMZ) is quantified using climatological Argo and dissolved oxygen data, combined with reanalysis wind stress data. We (1) estimate all oxygen fluxes (advection and turbulent diffusion) ventilating this OMZ, (2) quantify for the first time the oxygen contribution from the subtropical versus the traditionally studied tropical-equatorial pathway, and (3) derive a refined annual-mean oxygen budget for the ESP-OMZ. In the upper OMZ layer, net oxygen supply is dominated by tropical-equatorial advection, with more than one-third of this supply upwelling into the Ekman layer through previously unevaluated vertical advection, within the overturning component of the regional Subtropical Cell (STC). Below the STC, at the OMZ's core, advection is weak and turbulent diffusion (isoneutral and dianeutral) accounts for 89% of the net oxygen supply, most of it coming from the oxygen-rich subtropical gyre. In the deep OMZ layer, net oxygen supply occurs only through turbulent diffusion and is dominated by the tropical-equatorial pathway. Considering the entire OMZ, net oxygen supply (3.8 +/- 0.42 mu mol kg(-1) yr(-1)) is dominated by isoneutral turbulent diffusion (56.5%, split into 32.3% of tropical-equatorial origin and 24.2% of subtropical origin), followed by isoneutral advection (32.0%, split into 27.6% of tropical-equatorial origin and 4.4% of subtropical origin) and dianeutral diffusion (11.5%). One-quarter (25.8%) of the net oxygen input escapes through dianeutral advection (most of it upwelling) and, assuming steady state, biological consumption is responsible for most of the oxygen loss (74.2%).

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.

Carter, BR, Feely RA, Mecking S, Cross JN, Macdonald AM, Siedlecki SA, Talley LD, Sabine CL, Millero FJ, Swift JH, Dickson AG, Rodgers KB.  2017.  Two decades of Pacific anthropogenic carbon storage and ocean acidification along Global Ocean Ship-lebased Hydrographic Investigations Program sections P16 and P02. Global Biogeochemical Cycles. 31:306-327.   10.1002/2016gb005485   AbstractWebsite

A modified version of the extended multiple linear regression (eMLR) method is used to estimate anthropogenic carbon concentration (C-anth) changes along the Pacific P02 and P16 hydrographic sections over the past two decades. P02 is a zonal section crossing the North Pacific at 30 degrees N, and P16 is a meridional section crossing the North and South Pacific at similar to 150 degrees W. The eMLR modifications allow the uncertainties associated with choices of regression parameters to be both resolved and reduced. Canth is found to have increased throughout the water column from the surface to similar to 1000 m depth along both lines in both decades. Mean column Canth inventory increased consistently during the earlier (1990s-2000s) and recent (2000s-2010s) decades along P02, at rates of 0.53 +/- 0.11 and 0.46 +/- 0.11 mol Cm-2 a(-1), respectively. By contrast, Canth storage accelerated from 0.29 +/- 0.10 to 0.45 +/- 0.11 mol Cm-2 a(-1) along P16. Shifts in water mass distributions are ruled out as a potential cause of this increase, which is instead attributed to recent increases in the ventilation of the South Pacific Subtropical Cell. Decadal changes along P16 are extrapolated across the gyre to estimate a Pacific Basin average storage between 60 degrees S and 60 degrees N of 6.1 +/- 1.5 PgC decade(-1) in the earlier decade and 8.8 +/- 2.2 PgC decade(-1) in the recent decade. This storage estimate is large despite the shallow Pacific Canth penetration due to the large volume of the Pacific Ocean. By 2014, Canth storage had changed Pacific surface seawater pH by -0.08 to -0.14 and aragonite saturation state by -0.57 to -0.82.

Talley, LD.  2013.  Closure of the Global Overturning Circulation Through the Indian, Pacific, and Southern Oceans: Schematics and Transports. Oceanography. 26:80-97. AbstractWebsite

The overturning pathways for the surface-ventilated North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) and the diffusively formed Indian Deep Water (IDW) and Pacific Deep Water (PDW) are intertwined. The global overturning circulation (GOC) includes both large wind-driven upwelling in the Southern Ocean and important internal diapycnal transformation in the deep Indian and Pacific Oceans. All three northern-source Deep Waters (NADW, IDW, PDW) move southward and upwell in the Southern Ocean. AABW is produced from the denser, salty NADW and a portion of the lighter, low oxygen IDW/PDW that upwells above and north of NADW. The remaining upwelled IDW/PDW stays near the surface, moving into the subtropical thermoclines, and ultimately sources about one-third of the NADW. Another third of the NADW comes from AABW upwelling in the Atlantic. The remaining third comes from AABW upwelling to the thermocline in the Indian-Pacific. Atlantic cooling associated with NADW formation (0.3 PW north of 32 degrees S; 1 PW = 1015 W) and Southern Ocean cooling associated with AABW formation (0.4 PW south of 32 degrees S) are balanced mostly by 0.6 PW of deep diffusive heating in the Indian and Pacific Oceans; only 0.1 PW is gained at the surface in the Southern Ocean. Thus, while an adiabatic model of NADW global overturning driven by winds in the Southern Ocean, with buoyancy added only at the surface in the Southern Ocean, is a useful dynamical idealization, the associated heat changes require full participation of the diffusive Indian and Pacific Oceans, with a basin-averaged diffusivity on the order of the Munk value of 10(-4) m(2) s(-1).

Fiedler, PC, Talley LD.  2006.  Hydrography of the eastern tropical Pacific: A review. Progress in Oceanography. 69:143-180.   10.1016/j.pocean.2006.03.008   AbstractWebsite

Eastern tropical Pacific Ocean waters lie at the eastern end of a basin-wide equatorial current system, between two large subtropical gyres and at the terminus of two eastern boundary currents. Descriptions and interpretations of surface, pycnocline, intermediate and deep waters in the region are reviewed. Spatial and temporal patterns are discussed using (1) maps of surface temperature, salinity, and nutrients (phosphate, silicate, nitrate and nitrite), and thermocline and mixed layer parameters, and (2) meridional and zonal sections of temperature, salinity, potential density, oxygen, and nutrients. These patterns were derived from World Ocean Database observations by an ocean interpolation algorithm: loess-weighted observations were projected onto quadratic functions of spatial coordinates while simultaneously fitting annual and semiannual harmonics and the Southern Oscillation Index to account for interannual variability. Contrasts between the equatorial cold tongue and the eastern Pacific warm pool are evident in all the hydrographic parameters. Annual cycles and ENSO (El Nino-Southern Oscillation) variability are of similar amplitude in the eastern tropical Pacific, however, there are important regional differences in relative variability at these time scales. Unique characteristics of the eastern tropical Pacific are discussed: the strong and shallow pycnocline, the pronounced oxygen minimum layer, and the Costa Rica Dome. This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific. (c) 2006 Elsevier Ltd. All rights reserved.

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].

Talley, LD, Tishchenko P, Luchin V, Nedashkovskiy A, Sagalaev S, Kang DJ, Warner M, Min DH.  2004.  Atlas of Japan (East) Sea hydrographic properties in summer, 1999. Progress in Oceanography. 61:277-348.   10.1016/j.pocean.2004.06.011   AbstractWebsite

Hydrographic properties from CTD and discrete bottle sample profiles covering the Japan (East) Sea in summer, 1999, are presented in vertical sections, maps at standard depths, maps on isopycnal surfaces, and as property-property distributions. This data set covers most of the Sea with the exception of the western boundary region and northern Tatar Strait, and includes nutrients, pH, alkalinity, and chlorofluorocarbons, as well as the usual temperature, salinity, and oxygen observations. (C) 2004 Elsevier Ltd. All rights reserved.

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.

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, 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.

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.