Publications with links

Export 6 results:
Sort by: Author [ Title  (Asc)] Type Year
A B C D E F G H I J K L M N O P Q R S T U V [W] X Y Z   [Show ALL]
McCartney, MS, Talley LD.  1984.  Warm-to-Cold Water Conversion in the Northern North-Atlantic Ocean. Journal of Physical Oceanography. 14:922-935.   10.1175/1520-0485(1984)014<0922:wtcwci>;2   AbstractWebsite

A box Model of warm-to-cold-water conversion in the northern North Atlantic is developed and used to estimate conversion rates, given water mass temperatures, conversion paths and rate of air-sea heat exchange. The northern North Atlantic is modeled by three boxes, each required to satisfy heat and mass balance statements. The boxes represent the Norwegian Sea, and a two-layer representation of the open subpolar North Atlantic. In the Norwegian Sea box, warm water enters from the south, is cooled in the cyclonic gyre of the Norwegian–Greenland Sea, and the colder water returns southwards to the open subpolar North Atlantic. Some exchange with the North Polar Sea also is included. The open subpolar North Atlantic has two boxes. In the abyssal box, the dense overflows from the Norwegian Sea flow south, entraining warm water from the upper-ocean box. In the upper-ocean box, warm water enters from the south, supplying the warm water for an upper ocean cyclonic circulation that culminates in production by convection of Labrador Sea Water, and also the warm water that is entrained into the abyss, and the warm water that continues north into the Norwegian Sea. Our estimates are that 14 × 106 m3 s−1 of warm (11.5°C) water flows north to the west of Ireland, with about a third of this branching into the Norwegian Sea. The production rate for Labrador Sea Water is 8.5 × 106 m3 s−1), and this combines with a flow of dense Norwegian Sea Overflow waters (with entrained warmer waters) at 2.5 × 106 m3 s−1 to give a Deep Western Boundary Current of 11 × 106 m3 s−1. The total southward flow east of Newfoundland is this plus 4 × 106 m3 s−1 of cold less dense Labrador Current waters (there is a net southward flow between Newfoundland and Ireland of about 1 × 106 m3 s−1 supplied by northward flow through the Bering Strait, passing through the North Polar Sea to enter the Norwegian Sea.

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.

Abernathey, RP, Cerovecki I, Holland PR, Newsom E, Mazlo M, Talley LD.  2016.  Water-mass transformation by sea ice in the upper branch of the Southern Ocean overturning. Nature Geoscience. 9:596-+.   10.1038/ngeo2749   AbstractWebsite

Ocean overturning circulation requires a continuous thermodynamic transformation of the buoyancy of seawater. The steeply sloping isopycnals of the Southern Ocean provide a pathway for Circumpolar Deep Water to upwell from mid depth without strong diapycnal mixing(1-3), where it is transformed directly by surface fluxes of heat and freshwater and splits into an upper and lower branch(4-6). While brine rejection from sea ice is thought to contribute to the lower branch(7), the role of sea ice in the upper branch is less well understood, partly due to a paucity of observations of sea-ice thickness and transport(8,9). Here we quantify the sea-ice freshwater flux using the Southern Ocean State Estimate, a state-of-the-art data assimilation that incorporates millions of ocean and ice observations. We then use the water-mass transformation framework(10) to compare the relative roles of atmospheric, sea-ice, and glacial freshwater fluxes, heat fluxes, and upper-ocean mixing in transforming buoyancy within the upper branch. We find that sea ice is a dominant term, with differential brine rejection and ice melt transforming upwelled Circumpolar Deep Water at a rate of similar to 22 x 10(6) m(3) s(-1). These results imply a prominent role for Antarctic sea ice in the upper branch and suggest that residual overturning and wind-driven sea-ice transport are tightly coupled.

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, Stammer D, Fukumori I.  2001.  The WOCE Synthesis. Ocean circulation and climate : observing and modelling the global ocean. ( Siedler G, Church J, Gould WJ, Eds.).:525-546., San Diego, Calif. London: Academic Abstract
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.