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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.

Delman, AS, McClean JL, Sprintall J, Talley LD, Yulaeva E, Jayne SR.  2015.  Effects of eddy vorticity forcing on the mean state of the Kuroshio Extension. Journal of Physical Oceanography. 45:1356-1375.   10.1175/jpo-d-13-0259.1   AbstractWebsite

Eddy-mean flow interactions along the Kuroshio Extension (KE) jet are investigated using a vorticity budget of a high-resolution ocean model simulation, averaged over a 13-yr period. The simulation explicitly resolves mesoscale eddies in the KE and is forced with air-sea fluxes representing the years 1995-2007. A mean-eddy decomposition in a jet-following coordinate system removes the variability of the jet path from the eddy components of velocity; thus, eddy kinetic energy in the jet reference frame is substantially lower than in geographic coordinates and exhibits a cross-jet asymmetry that is consistent with the baroclinic instability criterion of the long-term mean field. The vorticity budget is computed in both geographic (i. e., Eulerian) and jet reference frames; the jet frame budget reveals several patterns of eddy forcing that are largely attributed to varicose modes of variability. Eddies tend to diffuse the relative vorticity minima/maxima that flank the jet, removing momentum from the fast-moving jet core and reinforcing the quasi-permanent meridional meanders in the mean jet. A pattern associated with the vertical stretching of relative vorticity in eddies indicates a deceleration (acceleration) of the jet coincident with northward (southward) quasi-permanent meanders. Eddy relative vorticity advection outside of the eastward jet core is balanced mostly by vertical stretching of the mean flow, which through baroclinic adjustment helps to drive the flanking recirculation gyres. The jet frame vorticity budget presents a well-defined picture of eddy activity, illustrating along-jet variations in eddy-mean flow interaction that may have implications for the jet's dynamics and cross-frontal tracer fluxes.

Macdonald, AM, Mecking S, Robbins PE, Toole JM, Johnson GC, Talley L, Cook M, Wijffels SE.  2009.  The WOCE-era 3-D Pacific Ocean circulation and heat budget. Progress in Oceanography. 82:281-325.   10.1016/j.pocean.2009.08.002   AbstractWebsite

To address questions concerning the intensity and spatial structure of the three-dimensional circulation within the Pacific Ocean and the associated advective and diffusive property flux divergences, data from approximately 3000 high-quality hydrographic stations collected on 40 zonal and meridional cruises have been merged into a physically consistent model. The majority of the stations were occupied as part of the World Ocean Circulation Experiment (WOCE), which took place in the 1990s. These data are supplemented by a few pre-WOCE surveys of similar quality, and time-averaged direct-velocity and historical hydrographic measurements about the equator. An inverse box model formalism is employed to estimate the absolute along-isopycnal velocity field, the magnitude and spatial distribution of the associated diapycnal flow and the corresponding diapycnal advective and diffusive property flux divergences. The resulting large-scale WOCE Pacific circulation can be described as two shallow overturning cells at mid- to low latitudes, one in each hemisphere, and a single deep cell which brings abyssal waters from the Southern Ocean into the Pacific where they upwell across isopycnals and are returned south as deep waters. Upwelling is seen to occur throughout most of the basin with generally larger dianeutral transport and greater mixing occurring at depth. The derived pattern of ocean heat transport divergence is compared to published results based on air-sea flux estimates. The synthesis suggests a strongly east/west oriented pattern of air-sea heat flux with heat loss to the atmosphere throughout most of the western basins, and a gain of heat throughout the tropics extending poleward through the eastern basins. The calculated meridional heat transport agrees well with previous hydrographic estimates. Consistent with many of the climatologies at a variety of latitudes as well, our meridional heat transport estimates tend toward lower values in both hemispheres. (C) 2009 Elsevier Ltd. All rights reserved.

Oka, E, Talley LD, Suga T.  2007.  Temporal variability of winter mixed layer in the mid- to high-latitude North Pacific. Journal of Oceanography. 63:293-307.   10.1007/s10872-007-0029-2   AbstractWebsite

Temperature and salinity data from 2001 through 2005 from Argo profiling floats have been analyzed to examine the time evolution of the mixed layer depth (MLD) and density in the late fall to early spring in mid to high latitudes of the North Pacific. To examine MLD variations on various time scales from several days to seasonal, relatively small criteria (0.03 kg m(-3) in density and 0.2 degrees C in temperature) are used to determine MLD. Our analysis emphasizes that maximum MLD in some regions occurs much earlier than expected. We also observe systematic differences in timing between maximum mixed layer depth and density. Specifically, in the formation regions of the Subtropical and Central Mode Waters and in the Bering Sea, where the winter mixed layer is deep, MLD reaches its maximum in late winter (February and March), as expected. In the eastern subarctic North Pacific, however, the shallow, strong, permanent halocline prevents the mixed layer from deepening after early January, resulting in a range of timings of maximum MLD between January and April. In the southern subtropics; from 20 degrees to 30 degrees N, where the winter mixed layer is relatively shallow, MLD reaches a maximum even earlier in December-January. In each region, MLD fluctuates on short time scales as it increases from late fall through early winter. Corresponding to this short-term variation, maximum MLD almost always occurs 0 to 100 days earlier than maximum mixed layer density in all regions.

Talley, LD, Sprintall J.  2005.  Deep expression of the Indonesian Throughflow: Indonesian Intermediate Water in the South Equatorial Current. Journal of Geophysical Research-Oceans. 110   10.1029/2004jc002826   AbstractWebsite

[1] The narrow westward flow of the South Equatorial Current ( SEC), centered at 12 degrees S and carrying freshened water from the Indonesian seas, is traced across the Indian Ocean using data from the World Ocean Circulation Experiment. The jet is remarkably zonal and quasi-barotropic, following the potential vorticity contours characteristic of the tropics, separating higher-oxygen and lower-nutrient waters of the subtropics from the oxygen-depleted waters of the tropics. The fresh surface waters are the usual Indonesian Throughflow Water reported previously. Less well studied is the intermediate-depth SEC carrying fresher water from the Banda Sea and Pacific, known as Indonesian Intermediate Water (IIW) or Banda Sea Intermediate Water. The high-silica signature of IIW is documented here, permitting us to ( 1) trace the spread of IIW from sill density at Leti Strait to higher density as it is diluted toward the west and ( 2) define an IIW core for transport estimates, of 3 to 7 Sv westward, using geostrophic and LADCP velocities. The high IIW silica is traced to the Banda Sea, arising from known diapycnal mixing of Pacific waters entering through Lifamatola Strait and local sources. New heat, freshwater, oxygen, and silica budgets within the Indonesian seas suggest at least 3 Sv of inflow through the relatively deep Lifamatola Strait, supplementing the observed 9 Sv through the shallower Makassar Strait. Both shallow and deep inflows and outflows, along with vigorous mixing and internal sources within the Indonesian seas, are required to capture the transformation of Pacific to Indonesian Throughflow waters.

Fukamachi, Y, Mizuta G, Ohshima KI, Talley LD, Riser SC, Wakatsuchi M.  2004.  Transport and modification processes of dense shelf water revealed by long-term moorings off Sakhalin in the Sea of Okhotsk. Journal of Geophysical Research-Oceans. 109   10.1029/2003jc001906   AbstractWebsite

The region off the east coast of Sakhalin is thought of as an important pathway of dense shelf water (DSW) from its production region in the northwestern Okhotsk Sea to the southern Okhotsk Sea. From July 1998 to June 2000, the first long-term mooring experiment was carried out in this region to observe the southward flowing East Sakhalin Current (ESC) and DSW. Moored and associated hydrographic data show considerable modification of cold dense water via mixing with warm offshore water in the slope region off northern Sakhalin. Significant onshore eddy heat flux was observed at the northernmost mooring (54.9degreesN), which suggests the occurrence of baroclinic instability. The eddy heat flux was not significant farther south. At moorings along 53degreesN, cold anticyclonic eddies were identified that were consistent with isolated eddies seen in the hydrographic data. The three years of hydrographic data also showed large differences in extent and properties of DSW. Furthermore, the mooring data show that seasonal variability of DSW was quite different in the two years. The average DSW transport for sigma(theta) > 26.7 evaluated using the moored data at 53degreesN for 1 year (1998-1999) was similar to0.21 Sv (= 10(6) m(3) s(-1)). This value is at the lower end of the previous indirect estimates. Along with the DSW modification, this transport estimate indicates that DSW was not only carried southward by the ESC but was spread offshore by eddies off northern Sakhalin.

Flatau, M, Talley L, Musgrave D.  2000.  Interannual variability in the Gulf of Alaska during the 1991-94 El Nino. Journal of Climate. 13:1664-1673.   10.1175/1520-0442(2000)013<1664:ivitgo>;2   AbstractWebsite

Mass and heat budgets in the Gulf of Alaska during the 1991-94 El Nino are examined using hydrographic data from several cruises undertaken as part of the International North Pacific Ocean Climate program and the repeated Canadian hydrographic sections out to Ocean weather Station Papa. The geostrophic ocean circulation resulted in convergence of heat into the region in spring 1992 and spring 1993. The advective heat convergence in spring 1992 corresponded to an average surface heat flux from the ocean to the atmosphere of about 74 W m(-2) in comparison with only 30 W m(-2) during spring 1993. The larger ocean heat loss to the atmosphere in 1992 followed a winter of large tropical SST anomalies and anomalously low pressure in the Aleutian low.

McCarthy, MC, Talley LD, Roemmich D.  2000.  Seasonal to interannual variability from expendable bathythermograph and TOPEX/Poseidon altimeter data in the South Pacific subtropical gyre. Journal of Geophysical Research-Oceans. 105:19535-19550.   10.1029/2000jc900056   AbstractWebsite

Estimates of dynamic height anomalies from expendable bathythermograph (XBT) and TOPEX/Poseidon (T/P) sea surface height (SSH) measurements were compared along a, transect at similar to 30 degrees S in the South Pacific. T/P SSH anomalies were calculated relative to a 5 year time mean. XBT dynamic height was calculated relative to 750 m using measured temperature and an objectively mapped climatological temperature-salinity relationship. The anomaly was obtained by subtracting out an objectively-mapped climatological dynamic height relative to 750 m. XBT temperature sections show evidence of a double-gyre structure, related to changes in shallow isopycnals near the gyre's center. XBT dynamic height and T/P SSH anomalies compare well with an RMS difference of 3.8 cm and a coherence above 0.7 for scales larger than 300 km. The differences between the two measures of dynamic height yield systematic patterns. Time-varying spatial averages of the differences are found to be related to changes in Sverdrup transport, zonal surface slope differences, and the 6 degrees C isotherm depth. Higher zonally averaged altimetry SSH than zonally averaged XBT height and larger northward transport from altimetry SSH than from XBT height correspond to gyre spinup determined from Sverdrup transport changes. This implies mass storage during gyre spinup due to the phase lag between the Ekman pumping and the full baroclinic Sverdrup response. Increases in the spatially averaged differences and zonal slope differences, associated with gyre spinup, correspond to shoaling in the 6 degrees C isotherm depth, requiring deep baroclinic changes out of phase with the 6 degrees C isotherm depth changes.

Talley, LD.  1999.  Simple coupled midlatitude climate models. Journal of Physical Oceanography. 29:2016-2037.   10.1175/1520-0485(1999)029<2016:scmcm>;2   AbstractWebsite

A set of simple analytical models is presented and evaluated for interannual to decadal coupled ocean-atmosphere modes at midlatitudes. The atmosphere and ocean are each in Sverdrup balance at these long timescales. The atmosphere's temperature response to heating determines the spatial phase relation between SST and sea level pressure (SLP) anomalies. Vertical advection balancing heating produces high (low) SLP lying east of warm (cold) SST anomalies, as observed in the Antarctic circumpolar wave (ACW), the decadal North Pacific mode, and the interannual North Atlantic mode. Zonal advection in an atmosphere with a rigid lid produces low SLP east of warm SST. However, if an ad hoc equivalent barotropic atmospheric response is assumed, high SLP lies east of warm SST. Relaxation to heating produces behavior like the observed North Atlantic decadal pattern, with low SLP over warm SST. Meridional advection in the atmosphere cannot produce the observed SST/SLP patterns. The dominant balance in the oceans temperature equation determines the phase speed of the modes. The coupled mode is nondispersive in all models examined here, indicating the need for additional processes. For modes with an SST-SLP offset as observed in the ACW and North Pacific, Ekman convergence acting as a heat source causes eastward propagation relative to the mean ocean flow. Sverdrup response to Ekman convergence, acting on the mean meridional temperature gradient, causes westward propagation relative to the mean ocean Row. When the ocean temperature adjusts through surface heat flux alone, the mode is advected by the mean ocean flow and is damped. Relaxation to heating in the atmosphere, when operating with Sverdrup response in the ocean, produces the only complete solution presented here that exhibits growth, with an a-folding timescale of order (100 days). This solution appears appropriate for the North Atlantic decadal mode. In Northern Hemisphere basins, with meridional boundaries, the: same sets of dynamics create the observed SST-SLP phase relation. An additional factor is the creation of SST anomalies through variations in the western boundary current strengths, which are related to the zonally integrated wind stress curl over the whole basin. If barotropic and hence fast adjustment is assumed, the resulting positive feedback can maintain or strengthen the coupled anomalies in the North Pacific and interannual North Atlantic modes.

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.

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.

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.