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Salmon, R, Talley LD.  1989.  Generalizations of Arakawas Jacobian. Journal of Computational Physics. 83:247-259.   10.1016/0021-9991(89)90118-6   AbstractWebsite

A simple method yields discrete Jacobians that obey analogues of the differential properties needed to conserve energy and enstrophy in 2-dimensional flow. The method is actually independent of the type of discretization and thus applies to an arbitrary representation in gridpoints, finite elements, or spectral modes, or to any mixture of the three. We illustrate the method by deriving simple energy- and enstrophy-conserving Jacobians for an irregular triangular mesh in a closed domain, and for a mixed gridpoint-and-mode representation in a semi-infinite channel.

Shcherbina, AY, Talley LD, Rudnick DL.  2003.  Direct observations of North Pacific ventilation: Brine rejection in the Okhotsk Sea. Science. 302:1952-1955.   10.1126/science.1088692   AbstractWebsite

Brine rejection that accompanies ice formation in coastal polynyas is responsible for ventilating several globally important water masses in the Arctic and Antarctic. However, most previous studies of this process have been indirect, based on heat budget analyses or on warm-season water column inventories. Here, we present direct measurements of brine rejection and formation of North Pacific Intermediate Water in the Okhotsk Sea from moored winter observations. A steady, nearly linear salinity increase unambiguously caused by local ice formation was observed for more than a month.

Shcherbina, AY, Talley LD, Rudnick DL.  2004.  Dense water formation on the northwestern shelf of the Okhotsk Sea: 2. Quantifying the transports. Journal of Geophysical Research-Oceans. 109   10.1029/2003jc002197   AbstractWebsite

A combination of direct bottom mooring measurements, hydrographic and satellite observations, and meteorological reanalysis was used to estimate the rate of formation of Dense Shelf Water (DSW) due to brine rejection on the Okhotsk Sea northwestern shelf and the rate of export of DSW from this region. On the basis of remote sensing data, an estimated 8.6x10(12) m(3) of DSW was formed during the winter of 1999-2000, resulting in a mean annual production rate of 0.3 Sv. According to direct observations, the export rate of DSW during this period varied from negligibly small in autumn to 0.75+/-0.27 Sv in winter (January-February), to 0.34+/-0.12 Sv in spring (March-April). From these observations the mean annual export rate can be estimated to be 0.27 Sv. The same relationships used to obtain the integral estimates were also applied differentially using an advective approach incorporating realistic flow and heat flux fields, which allowed direct comparison with the moored observations. The comparison highlights the importance of along-shelf advection and cross-shelf eddy transport to the accurate parameterization of DSW formation.

Shcherbina, AY, Talley LD, Rudnick DL.  2004.  Dense water formation on the northwestern shelf of the Okhotsk Sea: 1. Direct observations of brine rejection. Journal of Geophysical Research-Oceans. 109   10.1029/2003jc002196   AbstractWebsite

[1] Dense Shelf Water (DSW) formation due to brine rejection in the coastal polynya on the northwestern shelf of the Okhotsk Sea was studied using two bottom moorings during the winter of 1999 - 2000. A steady salinity and density increase that continued for over a month was observed at the shallower mooring. The maximum density of sigma(theta) = 26.92 kg m(-3) was reached during this period. The density increase terminated abruptly in late February, while the active brine rejection continued for several more weeks based on indirect evidence from water properties and ice cover. This termination was possibly due to the onset of baroclinic instability of the density front at the polynya edge facilitating offshore eddy transport of the density anomaly. Observed periodic baroclinic tide intensification events are hypothesized to be an indicator of the presence of such baroclinic eddies. No significant density increase was observed at the deeper, offshore mooring, indicating a robust demarcation of the offshore extent of newly formed DSW. The relatively fresh water of the tidally mixed zone inshore of the shelf front was the precursor of the DSW, aided by the late-autumn offshore transition of the front.

Shcherbina, AY, Talley LD, Firing E, Hacker P.  2003.  Near-surface frontal zone trapping and deep upward propagation of internal wave energy in the Japan/East Sea. Journal of Physical Oceanography. 33:900-912.   10.1175/1520-0485(2003)33<900:nfztad>2.0.co;2   AbstractWebsite

The full-depth current structure in the Japan/East Sea was investigated using direct velocity measurements performed with lowered and shipboard acoustic current Doppler profilers. Rotary spectral analysis was used to investigate the three-dimensional energy distribution as well as wave polarization with respect to vertical wave-numbers, yielding information about the net energy propagation direction. Highly energetic near-inertial downward-propagating waves were found in localized patches along the southern edge of the subpolar front. Between 500- and 2500-m depth, the basin average energy propagation was found to be upward, with the maximum of relative difference between upward- and downward-propagating energy lying at about 1500-m depth. This difference was most pronounced in the southeastern part of the basin.

Shcherbina, AY, Rudnick DL, Talley LD.  2005.  Ice-draft profiling from bottom-mounted ADCP data. Journal of Atmospheric and Oceanic Technology. 22:1249-1266.   10.1175/jtech1776.1   AbstractWebsite

The feasibility of ice-draft profiling using an upward-looking bottom-mounted acoustic Doppler current profiler (ADCP) is demonstrated. Ice draft is determined as the difference between the instrument depth, derived from high-accuracy pressure data, and the distance to the lower ice surface, determined by the ADCP echo travel time. Algorithms for the surface range estimate from the water-track echo intensity profiles, data quality control, and correction procedures have been developed. Sources of error in using an ADCP as an ice profiler were investigated using the models of sound signal propagation and reflection. The effects of atmospheric pressure changes, sound speed variation, finite instrument beamwidth, hardware signal processing, instrument tilt, beam misalignment, and vertical sensor offset are quantified. The developed algorithms are tested using the data from the winter-long ADCP deployment on the northwestern shelf of the Okhotsk Sea.

Shi, JR, Xie SP, Talley LD.  2018.  Evolving relative importance of the Southern Ocean and North Atlantic in anthropogenic ocean heat uptake. Journal of Climate. 31:7459-7479.   10.1175/jcli-d-18-0170.1   AbstractWebsite

Ocean uptake of anthropogenic heat over the past 15 years has mostly occurred in the Southern Ocean, based on Argo float observations. This agrees with historical simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), where the Southern Ocean (south of 30 degrees S) accounts for 72% +/- 28% of global heat uptake, while the contribution from the North Atlantic north of 30 degrees N is only 6%. Aerosols preferentially cool the Northern Hemisphere, and the effect on surface heat flux over the subpolar North Atlantic opposes the greenhouse gas (GHG) effect in nearly equal magnitude. This heat uptake compensation is associated with weakening (strengthening) of the Atlantic meridional overturning circulation (AMOC) in response to GHG (aerosol) radiative forcing. Aerosols are projected to decline in the near future, reinforcing the greenhouse effect on the North Atlantic heat uptake. As a result, the Southern Ocean, which will continue to take up anthropogenic heat largely through the mean upwelling of water from depth, will be joined by increased relative contribution from the North Atlantic because of substantial AMOC slowdown in the twenty-first century. In the RCP8.5 scenario, the percentage contribution to global uptake is projected to decrease to 48% +/- 8% in the Southern Ocean and increase to 26% +/- 6% in the northern North Atlantic. Despite the large uncertainty in the magnitude of projected aerosol forcing, our results suggest that anthropogenic aerosols, given their geographic distributions and temporal trajectories, strongly influence the high-latitude ocean heat uptake and interhemispheric asymmetry through AMOC change.

Sloyan, BM, Talley LD, Chereskin TK, Fine R, Holte J.  2010.  Antarctic Intermediate Water and Subantarctic Mode Water Formation in the Southeast Pacific: The Role of Turbulent Mixing. Journal of Physical Oceanography. 40:1558-1574.   10.1175/2010jpo4114.1   AbstractWebsite

During the 2005 austral winter (late August-early October) and 2006 austral summer (February-mid-March) two intensive hydrographic surveys of the southeast Pacific sector of the Southern Ocean were completed. In this study the turbulent kinetic energy dissipation rate epsilon, diapycnal diffusivity kappa, and buoyancy flux J(b) are estimated from the CTD/O(2) and XCTD profiles for each survey. Enhanced kappa of O(10(-3) to 10(-4) m(2) s(-1)) is found near the Subantarctic Front (SAF) during both surveys. During the winter survey, enhanced kappa was also observed north of the "subduction front,'' the northern boundary of the winter deep mixed layer north of the SAF. In contrast, the summer survey found enhanced kappa across the entire region north of the SAF below the shallow seasonal mixed layer. The enhanced kappa below the mixed layer decays rapidly with depth. A number of ocean processes are considered that may provide the energy flux necessary to support the observed diffusivity. The observed buoyancy flux (4.0 x 10(-8) m(2) s(-3)) surrounding the SAF during the summer survey is comparable to the mean buoyancy flux (0.57 x 10(-8) m(2) s(-3)) associated with the change in the interior stratification between austral summer and autumn, determined from Argo profiles. The authors suggest that reduced ocean stratification during austral summer and autumn, by interior mixing, preconditions the water column for the rapid development of deep mixed layers and efficient Antarctic Intermediate Water and Subantarctic Mode Water formation during austral winter and early spring.

Snyder, S, Franks PJS, Talley LD, Xu Y, Kohin S.  2017.  Crossing the line: Tunas actively exploit submesoscale fronts to enhance foraging success. Limnology and Oceanography Letters. 2:187-194.   10.1002/lol2.10049   Abstract

Fronts—i.e., the boundaries between water masses—are ubiquitous in the world oceans and have been shown to significantly influence pelagic ecosystems with enhanced local productivity and increased abundances of forage fish and top predators. Here we use data from archival tags to document how four juvenile albacore tunas foraged at and exploited a thermal front. Of the 3098 observed trips, the albacore mainly swam across the front between the warm side above the thermocline and the cold side below the thermocline with an average of 78 ± 20.4 cross-frontal trips per fish per day. The warm frontal surface waters provided a thermal resource, allowing the tuna to maintain higher body temperatures and thus forage more efficiently in the food-rich waters of the cold side of the front. Foraging success of the tunas decreased as the cross-front thermal gradient weakened. This first look into small-scale use of fronts by a top predator demonstrates that ephemeral, submesoscale oceanic features can play a significant role in pelagic ecology.

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.