Water Mass Formation from Revised COADS Data

Speer, Kevin; Isemer, Hans-Jörg; Biastoch, Arne

doi:10.1175/1520-0485(1995)025<2444:wmffrc>2.0.co;2

Cited by 49 publications

(26 citation statements)

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“…We were able to observe the full seasonal cycle over a 2-year period, and our in situ data confirmed previous modeling and climatological studies that found out that air-sea fluxes plus Ekman fluxes dominate the surface heat budget (Ribbe 1999;Rintoul and England 2002;Speer et al 1995). In the southeast Indian Ocean, we have quantified that the seasonal cycle of air-sea fluxes dominates the seasonal heat content variations in the mixed layer.…”

Section: Summary and Discussionsupporting

confidence: 87%

“…Rintoul and England (2002) estimated a dominant contribution of Ekman heat advection to observed variability in SAMW characteristics the south of Australia, and suggested that Ekman fluxes might partly explain a gradual cooling and freshening across the Indian and Pacific Oceans. Speer et al (1995) also inferred a strong Ekman contribution to SAMW formation. Our principal goal is to evaluate the contribution of the different terms of the mode water heat budget in the south Indian Ocean using a variety of data sources, but principally ARGO and satellite data.…”

Section: Introductionmentioning

confidence: 96%

“…Mode waters can be identified by relatively deep surface mixed layers, or, within the water column, by a pycnostad on a density-depth plot, or by a minimum of large-scale potential vorticity (PV). They are one of the primary results of air-sea interaction (Speer et al 1995) and serve to ventilate the interior of the upper ocean as they spread within gyres and boundary currents (McCartney 1982;Hanawa and Talley 2001).…”

Section: Introductionmentioning

confidence: 99%

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Formation of subantarctic mode water in the southeastern Indian Ocean

Sallée¹,

Wienders²,

Speer³

et al. 2006

Ocean Dynamics

128

147

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Subantarctic Mode Water (SAMW) is the name given to the relatively deep surface mixed layers found directly north of the Subantarctic Front in the Southern Ocean, and their extension into the thermocline as weakly stratified or low potential vorticity water masses. The objective of this study is to begin an investigation into the mechanisms controlling SAMW formation, through a heat budget calculation. ARGO profiling floats provide estimates of temperature and salinity typically in the upper 2,000 m and the horizontal velocity at various parking depths. These data are used to estimate terms in the mode water heat budget; in addition, mode water circulation is determined with ARGO data and earlier ALACE float data, and climatological hydrography. We find a rapid transition to thicker layers in the central South Indian Ocean, at about 70°S, associated with a reversal of the horizontal eddy heat diffusion in the surface layer and the meridional expansion of the ACC as it rounds the Kerguelen Plateau. These effects are ultimately related to the bathymetry of the region, leading to the seat of formation in the region southwest of Australia. Upstream of this region, the dominant terms in the heat budget are the air-sea flux, eddy diffusion, and Ekman heat transport, all having approximately equal importance. Within the formation area, the Ekman contribution dominates and leads to a downstream evolution of mode water properties.

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Section: Summary and Discussionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Formation of subantarctic mode water in the southeastern Indian Ocean

Sallée¹,

Wienders²,

Speer³

et al. 2006

Ocean Dynamics

128

147

View full text Add to dashboard Cite

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“…We also see a fall off in formation for densities of Ͼ 27.725 kg m Ϫ3 in the later part of the 1990s, as found by Rhein et al (2002). During this period, our formation in the lighter density range, possible upper LSW, is 9.3 Ϯ 0.5 Sv over 1995-98, 7.5 Ϯ 0.4 Sv over 1995-99, and 4.8 Ϯ 0.4 Sv over 1998 of which compare favorably with the estimate of Kieke et al (2006) who found a formation rate of 6.9-9.2 in 1998-99. Even using the reduced fluxes, estimates of 6.3 Ϯ 0.5 Sv for 1995-98 and 5.1 Ϯ 0.5 Sv for 1995-99 do not compare unfavorably.…”

Section: Interannual Variabilitysupporting

confidence: 85%

Water Mass Transformation and Formation in the Labrador Sea

Myers

Donnelly

2008

Journal of Climate

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Objectively analyzed surface hydrographic fields and NCEP-NCAR reanalysis fluxes are used to estimate water mass transformation and formation rates in the Labrador Sea, focusing on Labrador Sea Water (LSW). The authors estimate a mean long-term transformation of between 2.1 Ϯ 0.2 and 3.9 Ϯ 0.3 Sv (Sv ϵ 10 6 m 3 s Ϫ1 ) over the years 1960-99 to water with densities greater than ϭ 27.65 kg m Ϫ3 , depending on the correction used for the latent and sensible heat fluxes. Mean long-term formation rates are found between 0.9 Ϯ 0.2 and 1.7 Ϯ 0.3 Sv for ϭ 27.675 Ϫ 27.725 kg m Ϫ3 and 1.2 Ϯ 0.2 and 2.0 Ϯ 0.3 Sv for Ͼ 27.725 kg m Ϫ3 . There is tremendous variability associated with these formation rates with years of strong water formation (5.7-6.6 Ϯ 0.5-0.7 or 9.5-10.8 Ϯ 0.7-1.1 Sv) mixed with years of little or no formation in the given density ranges. The North Atlantic Oscillation (NAO) is linked (correlation coefficient of 0.45, significant at the 99% level) with the overall formation rate for Ͼ 27.625 kg m Ϫ3 . The observed long-term increase in net precipitation over the Labrador Sea does not seem to have had any significant effect on LSW, potentially reducing LSW transformation rates by 0.1 Sv. A reduction in surface salinity leads to formation occurring at a reduced density, but with little change in the amount of water transformed.

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“…The first is based on the analysis of the heat and mass fluxes between the ocean and the atmosphere and on the calculation of the density fluxes through the sea-air interface (Speer & Tziperman, 1992;Speer et al, 1995). The second, called kinematic method (Marshall et al, 1993;New et al, 1995), is based on the analysis of circulation in the upper ocean layers and it can be carried out in a Lagrangian or Eulerian reference frame.…”

Section: Kinematic Calculation Of Subductionmentioning

confidence: 99%

Subduction of South Atlantic Subtropical Mode Waters

Mill¹,

Paiva²

2013

Rev. Bras. Geof.

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ABSTRACT. The formation of the Subtropical Mode Waters (STMW) in the South Atlantic, part of the South Atlantic Central Water (SACW), by the subduction process, transferring mixed layer fluid into the permanent thermocline, is investigated using results of numerical simulations with the HYbrid Coordinate Ocean Model (HYCOM). Subduction rates were estimated by the kinematic method, adding the lateral induction of fluid through the sloping base of winter mixed layer with the vertical velocities at the base of winter mixed layer. Subduction rates above 100 m/year were found over the South Atlantic Subtropical Front, with maximum rates larger than 200 m/year in three distinct regions. The subduction pattern is dominated by the contribution of lateral induction, specially over the Subtropical Front, with rates significantly larger than the maximum rate of Ekman pumping. Different STMW were identified, associated with maximum layers thickness in isopycnals representative of upper and middle portion of SACW. The regions of maximum subduction rates were associated with the formation of the STMW.Keywords: mixed layer, ventilation, SACW, permanent thermocline, lateral induction. RESUMO. A formação deÁguas Modais Subtropicais (AMS) no Atlântico Sul, que fazem parte daÁgua Central do Atlântico Sul (ACAS), transferindo fluido da camada de mistura para a termoclina permantente pelo processo de subducção, foi estudada a partir dos resultados de simulações numéricas com um modelo oceânico de coordenadas híbridas (HYCOM -Hybrid Coordinate Ocean Model). A subducção foi calculada pelo método cinemático, somando as contribuições da indução lateral de fluido através da base da camada de mistura e as velocidades verticais na base da camada de mistura de inverno. Foram encontradas taxas de subducção superiores a 100 m/ano ao longo da Frente Subtropical do Atlântico Sul, com três núcleos distintos de máxima subducção atingindo mais de 200 m/ano. A indução lateral mostrou-se o processo dominante na subducção, especialmente ao longo da frente, com taxas significativamente superiores ao bombeamento de Ekman.Foram identificadas diferentes AMS associadasàs máximas espessuras de camadas representativas das porções média e superior daÁgua Central do Atlântico Sul (ACAS). As regiões de máximas taxas de subducção estão associadasà formação das AMS.Palavras-chave: camada de mistura, ventilação, ACAS, termoclina permanente, indução lateral.

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Water Mass Formation from Revised COADS Data

Cited by 49 publications

References 0 publications

Formation of subantarctic mode water in the southeastern Indian Ocean

Formation of subantarctic mode water in the southeastern Indian Ocean

Water Mass Transformation and Formation in the Labrador Sea

Subduction of South Atlantic Subtropical Mode Waters

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