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    Double Diffusion and the Distribution of the Density Ratio in the Mediterranean Waterfront Southeast of the Azores

    Source: Journal of Physical Oceanography:;1987:;Volume( 017 ):;issue: 001::page 12
    Author:
    Washburn, Libe
    ,
    Käse, Rolf H.
    DOI: 10.1175/1520-0485(1987)017<0012:DDATDO>2.0.CO;2
    Publisher: American Meteorological Society
    Abstract: Temperture and salinity (T?S) finestructure on vertical scales of 10 db and larger is examined in a 500 by 500 km grid located southeast of the Azores in the North Atlantic. The convergence of several water masses dominated by the Mediterranean Water (MW) at mid-depth (1000 m) leads to variety of T?S finestructure which is unstable to double diffusive processes. By forming histograms of the density ratio R?, a fundamental parameter in controlling double diffusive processes, it is found that 71% of the volume is unstable to salt fingering while only 5% is unstable to diffusive layering, the other double diffusive instability. In about 24% of the volume, R? is less than 2 in the salt fingering sense and at these low values salt fingers grow rapidly. This suggests that salt fingering may be an important diapycnal mixing process in much of the region. Two primary salt fingering regions are found: a near-surface region from about 100 to 500 db with a modal R? of 2.0 and a deeper region from about 1000 to 1500 db (the maximum depth of the CTD survey) with a modal R? of 1.3 A horizontal map of R? in the lower region shows that on average the lowest values (R?≤1.25) are found under the MW pool, although other, isolated regions of low R? are found to the south. A map of the rms R? fluctuation ?R?rms in the lower region shows that the most vertically uniform R? profiles also occur under the MW pool. High levels of ?R?rms are found within a region containing a strong cyclonic meander described by Käse and Zenk and may result from increased isopycnal mixing activity. To examine the occurrence of thermohaline staircase structures which have been found previously in the Mediterranean Outflow, a ?steppiness index? is defined which detects step and layer finestructure on vertical scales of 20 db and larger. Staircase structures on these scales are found most frequently to the south of the Azores Current in the inner gyre waters. These structures are generally not found above 1500 db under the MW pool.
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      Double Diffusion and the Distribution of the Density Ratio in the Mediterranean Waterfront Southeast of the Azores

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    contributor authorWashburn, Libe
    contributor authorKäse, Rolf H.
    date accessioned2017-06-09T14:48:14Z
    date available2017-06-09T14:48:14Z
    date copyright1987/01/01
    date issued1987
    identifier issn0022-3670
    identifier otherams-27121.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4164092
    description abstractTemperture and salinity (T?S) finestructure on vertical scales of 10 db and larger is examined in a 500 by 500 km grid located southeast of the Azores in the North Atlantic. The convergence of several water masses dominated by the Mediterranean Water (MW) at mid-depth (1000 m) leads to variety of T?S finestructure which is unstable to double diffusive processes. By forming histograms of the density ratio R?, a fundamental parameter in controlling double diffusive processes, it is found that 71% of the volume is unstable to salt fingering while only 5% is unstable to diffusive layering, the other double diffusive instability. In about 24% of the volume, R? is less than 2 in the salt fingering sense and at these low values salt fingers grow rapidly. This suggests that salt fingering may be an important diapycnal mixing process in much of the region. Two primary salt fingering regions are found: a near-surface region from about 100 to 500 db with a modal R? of 2.0 and a deeper region from about 1000 to 1500 db (the maximum depth of the CTD survey) with a modal R? of 1.3 A horizontal map of R? in the lower region shows that on average the lowest values (R?≤1.25) are found under the MW pool, although other, isolated regions of low R? are found to the south. A map of the rms R? fluctuation ?R?rms in the lower region shows that the most vertically uniform R? profiles also occur under the MW pool. High levels of ?R?rms are found within a region containing a strong cyclonic meander described by Käse and Zenk and may result from increased isopycnal mixing activity. To examine the occurrence of thermohaline staircase structures which have been found previously in the Mediterranean Outflow, a ?steppiness index? is defined which detects step and layer finestructure on vertical scales of 20 db and larger. Staircase structures on these scales are found most frequently to the south of the Azores Current in the inner gyre waters. These structures are generally not found above 1500 db under the MW pool.
    publisherAmerican Meteorological Society
    titleDouble Diffusion and the Distribution of the Density Ratio in the Mediterranean Waterfront Southeast of the Azores
    typeJournal Paper
    journal volume17
    journal issue1
    journal titleJournal of Physical Oceanography
    identifier doi10.1175/1520-0485(1987)017<0012:DDATDO>2.0.CO;2
    journal fristpage12
    journal lastpage25
    treeJournal of Physical Oceanography:;1987:;Volume( 017 ):;issue: 001
    contenttypeFulltext
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    DSpace software copyright © 2002-2015  DuraSpace
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